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The KRO Groundwater Literature Reference Compilation is is an extension of scientific references compiled by Nevada Exploration Inc that are related to hydro-geochemistry, the science that deals with elements dissolved in groundwater.
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Abstract: More than 100 samples from 18 stations on Wisconsin rivers1, including the Mississippi, have been analyzed fluorimetrically for uranium. Uranium content from 0.01 to 1.1 parts per billion were found, with an over all average of 0.45 parts per billion. Experiments indicate an average error of ±6.4 percent of the amount present. At different seasons of the year one station on the Mississippi showed unsystematic variations from 0.08 to 0.82 parts per billion, and other stations on large rivers showed similar variations. Small northern Wisconsin rivers systematically had their maximum uranium concentrations) in winter; it is believed that ground water is responsible for most of the uranium, in these streams. Southern Wisconsin rivers systematically had their maximum uranium concentrations in the spring; it is believed that uranium from phosphate fertilizer is responsible for this springtime peak. Analyses of representative samples of phosphate fertilizer used last spring in Wisconsin showed uranium contents from 22 to 56 parts per million, which would give uranium concentrations of about 8 pounds per square mile of fertilized land. These data and material balances based upon them are very useful in suggesting a pattern of geochemical prospecting based upon sampling ground and surface waters.
Critical Reviews in Environmental Controls 9, no. 2, p. 97-156.
Abstract: Prediction of the movement of contaminants in groundwater systems through the use of models has been given increased emphasis in recent years because of the growing trend toward subsurface disposal of wastes. Prediction is especially critical when nuclear wastes are involved. Contaminant transport models which include the effects of dispersion have been applied to several field situations. However, factors that limit the routine use of these models include the difficulty of determining the field coefficient of dispersion and numerical difficulties encountered when solving the dispersion equation. Regional size models which neglect the effects of dispersion have had limited success because of the scarcity and poor quality of field data. Another difficulty in the development of contaminant transport models is the current lack of knowledge regarding the quantification of chemical reaction terms. This review examines the formulation of contaminant transport models, application to field problems, difficulties involved in obtaining input data, and current status of modeling efforts.
Abstract: Effects of carbonate-bicarbonate, orthophosphate, and pyrophosphate on the toxicity of copper (II) to Daphnia magna were studied at constant pH and total hardness. Mortality rates and reciprocal survival times were directly correlated with cupric (Cu2+) and copper hydroxy (Cu(OH)n) ion activities as determined by equilibrium calculations. Toxicity was negatively related to activities of soluble copper carbonate (CuCO3) and other complexes, and was found to be independent of dissolved copper or total copper concentrations.
Abstract: A 3 a data set of isotopes in precipitation from northern Chile show a very distinct pattern, with ?18O values ranging between ?18 and ?15‰ at high altitude stations, compared to ?18O values between ?10 and ?6‰ at the lower altitude areas. The 18O-depleted values observed in the high altitude area, the Altiplano, are related to processes that affect the air masses that originated over the Atlantic, cross the Amazon Basin (continental effect), ascend the Andes (altitude effect) and precipitated (convective effect) in the Altiplano. It is postulated that a second source of moisture, associated with air masses from the Pacific, may contribute to the 18O-enriched values observed in the lower altitude areas. Similar isotopic patterns are documented in springs and groundwater indicating that the data presented in this paper are an accurate representation of the long term behavior isotopic composition of rain in northern Chile.
Bendix Field Engineering Corporation, Grand Junction, Colorado., Report GJBX-5(84), 224 p.
Abstract: The Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) effort involved collection and analysis of samples of stream sediment, groundwater, and surface water from the 48 conterminous states and Alaska, to determine concentrations of uranium and other selected elements. The data were not expected to identify individual orebodies or deposits; rather, they were expected to help delineate geochemical provinces and suggest favorable areas in which studies should be conducted in more detail. This guide provides tabulations that may be useful in determining which geographic areas were surveyed during the HSSR effort and what information is available for those areas. When the survey was terminated in 1980, fieldwork ceased leaving some quadrangles incompletely sampled and some quadrangles in which no sampling was conducted. All the samples collected were analyzed, but no further sampling was conducted, nor will any be undertaken in the future. This guide is directed toward any user of HSSR data, no matter how much or how little knowledge of the HSSR survey the user may already have. The emphasis is on the information that is available in reports issued as part of the HSSR effort. The data-tape repository, described later in this guide, may be more important to some users; information pertaining to the use of the data tapes is provided in the User's Guide to NURE HSSR Tape Formats (Zinkl and Brock, 1984). 11 references, 15 figures, 9 tables. (ERA citation 09:037223)
In Chemical Modeling of Aqueous Systems II, Melchior and Bassett eds., ACS Symposium Series 416, p. 1-15.
Abstract: Chemical modeling in hydrologic systems has become an area of active research with immediate opportunities for application to environmental problems, interpretation of diagenetic processes, and in evaluating the deposition of minerals to name a few. Researchers working in these and other areas have identified the need to quantitatively evaluate the chemical changes in geologic systems as a result of both natural and man-induced processes. To expedite these evaluations, fundamental theories of aqueous chemistry have been incorporated into computer codes along with the required constants and thermochemical data, to perform various simulations. Over the past several decades the equations and resultant codes have evolved greatly. Many of the codes that today serve as the foundations for geochemical calculations have increased in complexity both as a result of new theories in aqueous chemistry and the technical issues which needed to be resolved. The technical issues currently being addressed are often more complex
Abstract: The possibility of gold mobility in supergene environments is suggested by numerous indirect observations of gold particles. However, presently there are no dissolution or transport data based on the chemistry of actual weathering solutions. We have investigated models of gold transport by studying the water chemistry of a stream where weathering of auriferous minerals is occurring under supergene conditions in a temperate climate. Dissolved gold concentrations in the auriferous zone are forty times higher (200 pmolL?1) than in non-auriferous zones (5 pmolL?1). We have examined the potential gold ligands: thiosulfate, hydroxide, and chloride. Speciation calculations using the field data show that gold solubility is controlled by a gold thiosulfate complex: Au(S2O3)23?. The oxidation of the thiosulfate ligand induces the destabilization of the aurothiosulfate complex. Gold is then reduced to the metallic state as submicronsized suspended particles. This conclusion is supported by the measured increase in gold content of suspended particulates. Mass balance calculations performed with both dissolved and paniculate gold data permit the quantification of gold deposition along the stream.
Abstract: Low-pH waters, requiring treatment because of high concentrations of dissolved metals, are being discharged from a decommissioned tailings impoundment at the former Waite Amulet Znsingle bondCu mine in northeastern Quebec, Canada. A detailed study of the vadose zone of the tailings comparing mineralogical and geochemical analyses of the tailings solids with geochemical analysis of the tailings pore water and pore gas indicates the presence of three zones within the tailings. These zones include an upper sulfide-depleted zone in which the sulfides have been extensively removed and oxidation is largely complete, an intermediate zone, where sulfide oxidation and acid neutralization reactions are occurring, and an unoxidized zone below the depth of oxygen penetration, where sulfides are unoxidized. High aqueous concentrations of dissolved solids are being displaced downward from the sulfide-depleted zone, through the unoxidized zone toward the water table. Sulfide-oxidation and acid-neutralization reactions have generated concentrations of dissolved solids high enough to lead to the precipitation of a series of secondary solid phases. Precipitation-dissolution reactions involving these solid phases control the concentrations of the major ions in the tailings pore water. Concentrations of dissolved metals are controlled by precipitation-dissolution, crystal-structural replacement, and adsorption/coprecipitation reactions. Predictions based on the observed data and numerical simulations suggest that, in the absence of an effective remedial program, sulfide oxidation and H+ production will continue for several centuries.
Abstract: Sensitive multi-element analysis techniques together with major-element and isotopic analyses were applied to spring, mine and surface waters in the vicinity of an important known zinc-lead deposit in a carbonate environment, in the "Les Malines" area (Gard, France). Both the dissolved and suspended phases were investigated, and concretions and sediments were also considered in some cases. This methodological test shows that the ore body leaves various clear fingerprints, such as the Zn, As, Sb, Pb and U levels in the dissolved phase, the sulfate increment and the ? 34S.. Some of the elements in solution are controlled by slightly soluble compounds, e.g. Zn by smithsonite and hydrozincite, Ba by barite, and Pb by hydrocerussite. Mapping the saturation indices for these elements appears useful for displaying the hydrogeochemical anomaly.
Abstract: Saline Ca-Na/Cl type groundwaters and brines sampled in deep mines over an extensive area of the Canadian Precambrian Shield have elevated BrCl ratios which may indicate that the chlorinity of these waters was derived from the infiltration of residual evaporitic brines, remnants of the great marine incursions of the Paleozoic era. Boron concentrations in these waters are generally low (i.e., < ~2 mg/ L) relative to seawater or Alberta Basin Devonian formation waters. However, the 11B10B ratios of these waters are significantly greater than the average value for continental crustal rocks with the highest values (~4.19) approaching that of present-day seawater (4.20). Moreover, the boron isotopic ratios generally trend to higher values with increasing chlorinity which supports the conclusion from the Br-Cl relationship that most of the chloride in shield brines is of marine origin, rather than a product of water/rock interactions. If this is correct, crystalline rocks must then be sufficiently permeable on a regional scale to have allowed the brine to infiltrate to depths of several kilometers where it now resides.
Abstract: The interaction of water and sulfide minerals yields dissolved species which can be utilized to trace back the presence of sulfide minerals and associated minerals. Computer modeling and laboratory and field results show that the most characteristic dissolved species are hydrogen sulfide (H2S, HS?), polysulfide ions (Sn2?) and thiosulfate (S2O32?), derived from the hydrolysis of sulfide minerals. Typical concentration ranges are: 10?5 – 10?7 mole/l for hydrogen sulfide, 10?6 – 10?9 mole/l for polysulfides and 10?5 – 10?8 mole/l for thiosulfate. The chemical reactivity of these species at contact with air makes them difficult to assess unless determined immediately after sampling.These sulfur species can be determined rapidly and accurately in field conditions by simultaneous titration with mercuric chloride employing an Ag/Ag2S electrode for the determination of the end points.The application to ore exploration is exemplified by the results of the research on roll-type uranium deposits in the southwest of France.
Application of groundwater geochemistry in mineral exploration--L'utilisation de la geochimie des eaux souterraines dans le domaine de l'exploration minerale.
In Berry, M.J. (ed) Current activities forum 1988, program with abstracts--Forum de, Geological Survey of Canada.
Abstract: A brief review of the history of geochemical prospecting is given and the various methods are described and discussed. The present and future applications are mentioned, with discussion of the advantages and drawbacks. Emphasis is laid on the ever-increasing future possibilities for the utilization of chemical methods. An extensive review of the relevant literature is given.
In D.M. Nelson and A.I. Johnson (eds.) Ground Water and Vadose Zone Monitoring, ASTM STP 1053
Abstract: Experiences with many measurements of the hydraulic conductivity of unlithified glacial and fluvial materials in Wisconsin suggest that hydraulic conductivity must be viewed in terms of the operational scale of measurement, based on the scale of the problem at hand and the volume of the materials of interest. Frequently, the hydraulic conductivity of a given lithostratigraphic unit appears to increase as the operational scale of measurement increases. In particular, laboratory methods can yield hydraulic conductivities one to two orders of magnitude lower than conductivities determined in field tests on the same materials. The operational scale of most laboratory methods is much smaller than the operational scale of most field problems, and laboratory tests, although often logistically and financially attractive, may be of little value in characterizing the hydraulic conductivity of Pleistocene and recent deposits at working field scales.
Abstract: A combination of solvent extraction and flameless atomic absorption spectrometry was used to determine gold at the parts-per-trillion (pg cm?3) level in natural waters. The method consisted of a two-step extraction procedure where Au was complexed as HAuCl4 in the presence of hydrochloric acid and extracted into a small volume of methylisobutyl ketone (MIBK), where a favourable distribution ratio (D = 1250) exists. In stage 1 of the extraction, 2 l of water was acidified with 70 cm3 of 6 M redistilled HCl and shaken with 55 cm3 of redistilled MIBK. At equilibrium, the volume of solvent was reduced to ? 5 cm3 and extracted 76% of the Au from the water. In the second extraction stage, the MIBK extracts were further concentrated by evaporating to dryness with a rotary evaporator in the presence of ? 5 cm3 of the original extracted water. Standards were prepared in the same manner as the samples of natural waters. The Au was re-extracted into 0.2 cm3 of MIBK. With a total concentration factor of ? 104, coupled with the high sensitivity of flameless atomic absorption, it was possible to determine Au levels as low as 1 pg cm?3. The technique was used to determine Au levels in unfiltered river-water samples draining Au-bearing Cambro-Ordovician sediments of the Meguma Group of eastern Nova Scotia, between Halifax and Sherbrooke. Au levels tended to decrease in a northeasterly direction and were highest (7 ppt) in the Little Salmon River draining Lake Major which is adjacent to the Montague Gold Mines.
Abstract: Spence is a supergene-enriched copper porphyry deposit located between Antofagasta and Calama in the Atacama Desert of northern Chile. Porphyry intrusion and hypogene mineralization took place during the Palaeocene. Following supergene enrichment that produced an atacamite-–brochantite assemblage in the oxide zone, the deposit was covered by 50 to 100?m of piedmont gravels of Miocene age. RioChilex discovered the deposit in 1996 by reconnaissance drilling. This paper describes elemental and isotopic data for groundwaters collected within and peripheral to the deposit and relates these compositions to geochemical anomalies in gravel soils over the deposit. There are two distinct types of groundwater with distinctive isotopic and elemental composition: saline water (average Cl= 11 600?mg/l) extending downflow from the axis of the deposit; and non-saline water (average Cl=1300?mg/l) upflow from the axis. Oxygen and hydrogen isotope ratios imply that the former is a deep formation water and the other is meteoric water derived from precipitation in mountains to the east. The data suggest that the saline formation water flows upward from a permeable fault zone coincident with the long axis of the deposit. This fault may have originally guided the intrusion of the porphyries and the copper-bearing hydrothermal fluids. The saline water has much greater contents of As and Se (up to 129?ppb and 800?ppb, respectively) than the meteoric water (both less than detection limits of 10 and 50?ppb, respectively), but both types have high amounts of Cu within the deposit area. Dispersion of Cu away from the deposit is restricted by adsorption of Cu2+ on negatively charged hydroxide colloids, whereas As and Se freely disperse dissolved as anions. Reactivation of the axial fault created a permeable fracture zone in the gravels above the deposit. During earthquake activity there was pumping of saline formation water to the surface up this fracture zone, which created soil anomalies. The anomalies are characterized by NaCl, As, Se and Cu. One kilometre to the east of the deposit there is another fracture zone in the gravels, overlying unmineralized basement. Soils above this zone have anomalies for NaCl, As and Se, indicative of flooding by formation water, but lacking Cu.
Abstract: It has become increasingly common for geologists to drill through 100?m or more of cover in search for buried mineral deposits. Geochemistry is one tool applied to this search, using a variety of approaches, including selective leaching of soils to extract the mobile component of elements, and the measurement of inorganic and organic gases. This paper provides an overview of some of the work carried out by the project Deep-Penetrating Geochemistry, sponsored by the Canadian Mining Industry Research Organization (CAMIRO), and supported by 26 Canadian and international companies and by the Ontario Geological Survey and the Canadian Geological Survey. The objective was to provide the mining industry with information relating to processes that may form anomalies at surface over buried deposits and to provide comparative data on methods used to detect these anomalies. Phase I of the project considered the theoretical and experimental framework for the movement of material from deeply buried deposits to the surface; much of this information has come from research on the containment of buried nuclear waste. In arid or semi-arid terrain, with a thick vadose zone, advective transport, which is the mass transfer of groundwater or air along with their dissolved or gaseous constituents, is the only known viable means of moving elements to the surface; diffusion of ions in water or gases in air is orders of magnitude slower. Examples of advective transport are pumping of mineralized groundwater to the surface during seismic activity and the extraction of air plus gas by barometric pumping. Both mechanisms require fractured rock and the interpretation of the derived anomalies requires consideration of neotectonic structures. In wetter climates, where water lies close to the surface, a variety of mechanisms have been proposed for creating anomalies at the surface. Diffusion-based models again suffer from slow rates of migration. Electrochemical models show a cathodic zone at the top of a buried sulphide conductor. Cations are attracted to the cathode, rather than to the surface, yet metals that most commonly migrate as cations are found to form anomalies at the surface.
Phase II of the CAMIRO study involved field studies at ten test sites. The test sites included buried porphyry deposits in northern Chile, a gold-copper deposit in the Carlin district of Nevada, and volcanogenic massive sulphide bodies covered by glacial sediments in the Abitibi greenstone belt of Ontario. In all cases anomalies were found in soils above buried mineralization. It is suggested that anomaly formation is an episodic and cyclic process, in which batches of metal in water-soluble form are introduced and the metal is then progressively incorporated with time into the secondary minerals of soil. Selective leaches have been developed to dissolve specific phases in the soil to detect these anomalies. We have compared the results for five selective leaches that are available from commercial laboratories: deionized water, ammonium acetate, hydroxylamine hydrochloride, Enzyme Leach and Mobile Metal Ion (MMI) plus one non-selective decomposition, aqua regia. In addition, the Institute of Geophysical and Geochemical Exploration laboratory in China has supplied data for four sequential selective leaches: water-extractable, adsorbed, organic-bound and iron- and manganese-bound. The weakest leaches dissolve mainly the most recently introduced metals that remain in water-soluble form. Other leaches dissolve specific secondary minerals, such as carbonates, or iron and manganese oxides, which contain the introduced metals. The usefulness of leaches that dissolve secondary minerals depends on the ratio of introduced (exogenic) metal that the minerals contain relative to that of endogenic origin derived from the primary minerals of soils. Our results indicate that this ratio is variable from site to site, so that there is no universal ‘best’ leach for dissolving secondary minerals in exploration surveys. For the test sites in Chile and Nevada, anomalies may have formed incrementally over a period of a million years or more, which permitted metals of exogenic origin to become incorporated into many secondary minerals. For these sites, some anomalies can be detected by aqua regia, although the anomaly/background contrast is less than for selective leaches. For the test sites in Ontario, only a few thousand years have elapsed since glacial sediments were deposited to conceal mineralization. Over this short period, metal of exogenic origin has been incorporated into only the most labile of secondary minerals and it is the leaches that dissolve these labile minerals that can successfully identify anomalies. At the two sites where the most detailed studies have been carried out, the Spence deposit in Chile and Cross Lake near Timmins, we have found that the optimum sampling depth in soils is critical to detecting anomalies.
Mineralium Deposita, 42, 205-218. DOI 10.1007/s00126-006-0108-0.
Abstract: Atacamite, a copper hydroxychloride, is an important constituent of supergene oxide zones of copper deposits in northern Chile, whereas in similar deposits elsewhere, it is rare. In Chile, it has generally been assumed to be a primary constituent of the supergene zones. There are two difficulties with this supposition. The first is that atacamite requires saline water for its formation, whereas supergene oxidation was caused by percolating, oxygenated meteoric water, mainly rainwater. The second is that atacamite dissolves rapidly or undergoes phase change when exposed to fresh water. Supergene enrichment of copper deposits in northern Chile extended over a long period, 44 to 9 Ma, being terminated by the onset of hyperaridity. During this period, there was at least intermittent rainfall, exposing previously formed atacamite to dissolution or phase change. Furthermore, atacamite-bearing oxide zones in several deposits are directly overlain by thick Miocene alluvial gravels; the stream waters that transported these gravels would have permeated the oxide zones. In some deposits, atacamite-bearing assemblages occur both in the oxide zones and in contiguous gravels. We suggest that atacamite-bearing oxide assemblages are more likely to have been a replacement of preexisting oxide phases after the onset of hyperaridity at about 9 Ma. A hyperarid climate made possible evaporation and concentration of chloride in meteoric waters. In this paper, we discuss another source of saline waters to modify oxide zones. Dewatering of the Domeyko Basin expelled brines along faults, some of which had earlier guided the location of porphyry deposits. At the Spence porphyry copper deposit, saline waters, which ?D vs ? 18O isotope analyses identify as basinal brines, are presently rising through the deposit, then flowing away along the base of the covering gravels. Compositions of these waters lie within the stability fields of atacamite and brochantite, the two minerals that comprise the oxide zone. Evidence is presented for other porphyry deposits, Radomiro Tomic and Gaby Sur, that basinal brines may have been involved in the late formation of atacamite.
Abstract: Northern Chile is a major producer of copper from porphyry deposits. Most ores worked to date were exposed near the surface. Exploration is now focused on deposits along a basement unconformity buried under piedmont gravels deposited by ca. 10 Ma. Two recent discoveries, the Spence and Gaby Sur deposits, are covered by gravel. Soils above these deposits have anomalies for elements present in saline, mineralized groundwaters. The anomalies occur above fracture zones in the gravels, believed to represent the upward propagation of basement faults that guided emplacement of the porphyries. We propose that during earthquakes in this seismically active region there was pumping of saline basement waters up the faults and fracture zones, entraining mineralized groundwaters from the deposits. After surface flooding and evaporation, elements were redistributed by infrequent rains. Sampling shows that surface-active cations, such as Cu2+, were adsorbed and retained in the top few centimeters of soil, whereas NaCl and porphyry indicator elements that dissolve as anions (Se, Re, and As) are not adsorbed and are removed to >40 cm depth. Given the 10 m.y. interval since the gravels were deposited, and the hyperarid climate of the Atacama Desert, anomalies may have formed by repeated episodes of seismically induced flooding. Company geochemical surveys show that such features are numerous in northern Chile, producing linear zones of saline soils plus other constituents of local groundwaters (e.g., B and I). Where faults controlling these features intersect mineralization, elements specific to the mineralization are also present. Saline zones may be outlined in the field by measuring the conductivity of soil plus water slurries; sampling for full geochemical analyses can be limited to areas so defined. Anomalies may be generated along fault lines in other seismically active, wetter climates, but only for elements that are adsorbed on soil minerals. Although the context of the study is mineral exploration, the process may be relevant to the formation of geochemical features of environmental interest above major faults.
Abstract: The Agricola Lake area lies within the tundra and is underlain by continuous permafrost. Archean metavolcanic rocks are host to massive sulphide mineralization, which contains Zn, Cu, Pb, Ag, Au, As, Cd and Hg. This mineralization is being actively oxidized, producing acidic waters enriched in a number of metals. The elements Pb, Ag and Hg are immobile in the surface environment and are largely retained in the soils near the mineralization. Zn, Cd and Cu are mobile and are dispersed in quantity far along the lake-stream system draining the mineralization. Arsenic is relatively immobile, but it has so wide a primary distribution, particularly in metasedimentary rocks overlying the volcanics, that it too is anomalous in sediments throughout the drainage. Ni and Co, derived from these metasedimentary rocks, and as mobile as Zn and Cd, are also strongly anomalous in lake sediments. Fixing of the mobile elements in sediments appears to be determined by their adsorption on iron oxides, Cu being adsorbed at lower pH values and closer to the mineralized source, than Zn, Cd, Ni or Co. The use of nearshore and centre-lake sediments for reconnaissance-level geochemical exploration is compared. The latter are a more homogeneous, finer-grained sampling medium. Dispersion of mobile indicator elements from their source in centre-lake sediment is greater than for nearshore sediment. This is because nearshore sediments are essentially subaqueous soils, that are not produced by lacustrine sedimentation. Adsorption of metals on nearshore material takes place in situ, so that dispersion trains can be no longer than that of the waters in contact. In the case of centre-lake sediments, it is suggested that metals are adsorbed on fine-grained particulates, which travel downstream before settling in the centre-lake bottoms. Waters are the most convenient sampling medium for more detailed levels of exploration. Surface waters are homogeneous within any one lake and show only moderate variation in composition throughout the summer ice-free season. Lake waters that are not derived from mineralized areas are very pure, with dissolved solids contents of 10 ppm or less.
Abstract: The use of lake waters for base metal exploration has been studied in the northern part of the Slave Geological Province of the Canadian Shield. The area is north of the treeline, within the zone of continuous permafrost, and, like most other regions of the Shield, has a high density of small lakes. A regional sampling of 1218 lakes established that less than 2 ppb (?g/l) Zn or Cu is typical of waters from unmineralized terrane. These samples had a median pH of 6.8 and a median specific conductivity of 19.5 ?mhos. Lake waters were also taken from the areas surrounding five massive sulphide occurrences: High Lake, Canoe Lake, Takiyuak Lake, Hackett River and Agricola Lake. In all cases there are unambiguous anomalies for Zn. Anomalies are also present for Cu, but are less intense and extensive. This difference between the two elements is related to the superior mobility of Zn in surface waters and its more consistent presence as a major constituent of massive sulphides. A water sampling apparatus has been developed and tested on a light turbine helicopter. Using this, thirty sites may be sampled each hour when sampling at a density of 1 site per 2.8 km2. Measurement of pH, conductivity and water temperature are recorded in the helicopter during sampling. A number of factors have been investigated that may influence the utility of lake water sampling for base metal exploration:
(1) Seasonal variability, while present to moderate degree, is unlikely to hinder application of the method.
(2) For the size of lakes sampled (2 km2 or less), elements are homogeneously distributed across the lake surface during the ice-free season. During the initial period of break-up there are marked variations in element content around the ice-free lake margin. Sampling during this period may help define the source of metals for anomalous lakes.
(3) Study of sample preservation suggests that mobile elements, such as Zn, that are stable in solution within lakes, are also relatively stable when untreated water is stored in plastic bottles.
(4) Care must be taken to avoid contamination of the samples, particularly from the bottle.
The areal extent of lake water base metal anomalies appears to be less than equivalent lake sediment anomalies. Thus for wide-interval, regional geochemical reconnaissance, lake sediment sampling is the method of choice. Lake waters are an appropriate medium for detailed exploration of areas of interest, such as volcanic belts. For this application, the principal attractions are rapid sampling rates, and hence low costs, high contrast anomalies, and a uniform sampling medium.
Abstract: This paper describes part of a project to examine geochemical methods in exploration for Pd deposits in northwestern Ontario. Palladium is one of the platinum group elements (PGE) that is mobile in dilute surface waters as hydroxy complexes, a feature that can facilitate its use in exploration. Earlier studies around the Lac des Iles Pd mine have shown that Pd is widely dispersed in solution even from sulphide-poor mineralization (Hattori & Cameron 2004). The region that includes Lac des Iles has been covered by a lake sediment survey by the Ontario Geological Survey (Dyer & Russell 2002). These lake sediment data provide a further means of better understanding the geochemistry of Pd in the surface environment and its application to exploration for PGE deposits. Factor analysis of the lake sediment data reveals three associations: Factor 1, an association of Cr, Co, Ni, Pt and Pd; Factor 2, an association of Pd, S and As; and Factor 3, an association of Cu, Ag and Au. High scores for Factor 1 extend for 10?km down-ice from the mineralized mafic rocks of Archean age at Lac des Iles and reflect the dispersion of clastic material by ice sheets, supplemented by hydromorphic dispersion. High scores for Factor 2 are much more widespread and are spatially associated with Quaternary glaciofluvial deposits, notably eskers. A plot of Pd alone in lake sediments throughout the area largely reflects this association with eskers. The elemental assemblage of Factor 2 originates from the leaching of fragments of Nipigon diabase (Pd) and Sibley sedimentary rocks (S, As), both of Proterozoic age, contained within the eskers. The high permeability of the eskers permits soluble elements to be leached. All three elements, Pd, S and As, form neutral and anionic complexes and are not adsorbed by negatively-charged iron oxyhydroxide colloids and coatings, which restrict the dispersion of elements that dissolve as cations, such as Cu, Ni and Co. Factor 3, Cu, Ag and Au, occurs in areas of Proterozoic bedrock.
Abstract: Geochemical sampling of groundwater may be an effective tool in exploring for Au deposits in areas of transported overburden. However, to use hydrogeochemistry effectively, we need to understand which elements are useful pathfinders and how their distribution patterns are affected by groundwater flow and geochemistry, especially in areas that have hypersaline groundwater. A hydrogeochemical survey was completed over the strongly Au-endowed St. Ives area of the Eastern Goldfields of Western Australia. Extensive geochemical and hydrogeological data were measured from 80 holes drilled on a kilometre-spaced grid. A numerical model was developed to quantify the groundwater flow regime in the study area. Also, hydrogeological data in combination with the geochemistry of the waters were used to identify a complex flow regime adjacent to Lake Lefroy, a playa lake in the area. Regional brine flows towards the salt lake, evaporation occurs and hypersaline (playa) brines are formed that sink and flow away from Lake Lefroy and beneath the regional brines. Density-driven, convective mixing of these two brines is responsible for forming a zone of brines with transitional compositions located near the edge of Lake Lefroy. Knowledge of the groundwater flow regime was used to interpret the distribution of elements around bedrock Au mineralization. An Au-only groundwater anomaly (>10?ppt, maximum 52?ppt) is located downstream of the Junction Au ore body. No anomaly was identified in deep brines associated with the nearby Argo/Apollo Au ore body; however, shallow regional brines sampled in a previous survey showed elevated Au values overlying and downstream of the mineralization. The lack of elevated Au concentrations in deeper groundwater associated with Argo/Apollo is because the samples collected were hypersaline playa brines sourced from Lake Lefroy that had not flowed over the mineralization. Possible pathfinder elements, such as Sb, Bi and Te, were either present in concentrations too low to detect or showed no spatial pattern related to known mineralization; however, a strong correlation was noted between some of their concentrations and salinity. Evaluation of the groundwater anomalies observed in this study suggests that hydrogeochemical exploration is most effective at a resolution of 0.5-4?km spacing, and does not require fully cased and packed wells, at least in cases where no confined aquifers are intersected in drilling. The results of this study illustrate the importance of understanding groundwater flow regimes in planning and interpreting hydrogeochemical surveys.
Abstract: This volume is an attempt to identify new directions, to summarize recent basic research and to review the state of knowledge about underlying principles that may influence the success of bio-geochemical exploration.
Abstract: The ?34S values of a variety of gypsum types from the moderm playa lakes of southern Australia show little relationship with underlying bedrock types or the ?34S values of the bedrock sulphur. On a regional scale, in both Western Australia (Yilgarn Block) and South Australia, the ?34S values of surficial gypmsum have a regular pattern over distances of 500 to 1000 km with highest values (? +21%‰) near coastlines decreasing to ?34S values of ? 14% further inland. Sea-salt sulphate is the dominant source of sulphur to the lakes investigated, although the proportion decreases from ? 100% near coastlines to ? 55% in some inland areas. A secondary source of sulphate is also airborne, but derives from volatile biogenic sulphur compounds of largely marine origin. Sulphur derived from rock weathering is a minor component, except in areas where the bedrock contains abundant sulphur. Thus Lake Cadibarrawirracanna receives ? 10% of its sulphur from weathering of the pyritic Bulldog Shale (Cretaceous), and Lake Amadeus, possibly up to one-third of its sulphate from evaporites of the Bitter Springs Formation (Late Proterozoic). Our ?34S measurements are the first tracers to directly establish the marine origin of components in Australian surface brines. The ?34S analyses indicate the accession of sulphur from both sea-salt and marine biogenic sulphur and clearly support delivery of salts to the Australian landscape as aerosols following established wind patterns. The data negate the possibility of derivation of the lacustrine “seawater-like” brine chemistry from either marine transgression or weathering of connate salts from marine strata alone. The occurrence of non-marine evaporites exhibiting largely marine-like chemistry and isotopic signatures is probably common to low-latitude tectonically stable areas and will make the distinction between some marine and non-marine evaporites from the geological record more difficult. The regular pattern of ?34S values of surficial sulphate in lakes and groundwaters in southern Australia provides an ideal baseline against which to search for anomalous ?34S values associated with base-metal or gold mineralization.
Abstract: Groundwater is an increasingly important resource to human populations around the world, and the study and protection of groundwater is an essential part of hydrogeology - the subset of hydrology that concentrates on the subsurface. Environmental isotopes, naturally occurring nuclides in water and solutes, have become fundamental tools for tracing the recharge, history, and contamination of groundwater.
Abstract: Comparison of decreasing total copper content and increasing pH of an abandoned copper mine drainage stream to the stability fields of malachite, tenorite, and cupric hydroxide indicates that soluble copper is not lost by precipitation but by sorption on the stream sediments.
Abstract: The relative abundances of dissolved 238U and its daughter 234U appear to be greatly affected as the uranium is transported downdip in sandstone aquifers. In an actively forming uranium accumulation at a reducing barrier, an input of 234U occurs in proximity to the isotopically non-selective precipitation of uranium from the water. The result is a downdip water much lower in uranium concentration but relatively enriched in 234U. The measurement of isotopic, as well as concentration, changes may increase the effectiveness of hydrogeochemical exploration for uranium. The investigation includes the uranium isotopic patterns in aquifers associated with known uranium orebodies in the Powder River and Shirley Basins, Wyoming, and Karnes County, Texas, U.S.A. In addition, the Carrizo sandstone aquifer of Texas was studied in detail, and the presence of an uranium accumulation inferred.
Abstract: The relationship between deuterium and oxygen-18 concentrations in natural meteoric waters from many parts of the world has been determined with a mass spectrometer. The isotopic enrichments, relative to ocean water, display a linear correlation over the entire range for waters which have not undergone excessive evaporation.
Abstract: Natural organic matter is readily adsorbed by alumina and kaolinite in the pH range of natural waters. Adsorption occurs by complex formation between surface hydroxyls and the acidic functional groups of the organic matter. Oxides with relatively acidic surface hydroxyls, e.g. silica, do not react strongly with the organic matter. Under conditions typical for natural waters, almost complete surface coverage by adsorbed organic matter may be expected for alumina, hydrous iron oxides and the edge sites of aluminosilicates. Potentiometric titration and electrophoresis indicate that most of the acidic functional groups of the adsorbed organic matter are neutralized by protons from solution. The organic coating is expected to have a great influence on subsequent adsorption of inorganic cations and anions.
ACS Symposium Series 93, Am. Chem. Soc., Washington D.C., p. 199-317.
Abstract: The results of a newly proposed model for adsorption at the oxide/water interface are discussed. The modeling approach is similar to other surface complexation schemes, but mass-law equations are corrected for the effect of the electrostatic field. In this respect, this model bridges the gap between those models that emphasize physical interactions. The general applicability of the model is demonstrated with comparisons of calculations and experimental data for adsorption of metal ions, anions, and metal-ligand complexes. Intrinsic ionization and surface complexation constants can be determined with an improved double extrapolation technique. By comparison with analogous reactions in solution, it is shown that the stabilities of complexes formed at oxide surfaces are governed primarily by large positive entropy changes. The most important factor in the change of entropy is the increased mobility of solvent molecules after complex formation. The entropy change of complexes within the compact layer of the EDL will be larger than analogous reactions in solution, due to the decreased dielectric strength of water. Thus, reactions which lead to a neutralization of charge, e.g. hydrolysis of metal ions, protolysis of anions, have greater stability constants at the surface than in bulk water.
Abstract: The supergiant Pb-Zn-Ag Broken Hill orebody and numerous other minor mineral deposits occur within the limited outcrop of the Proterozoic Curnamona Province of Australia. The vast majority of this Province is concealed by up to 200 m of transported regolith, hampering conventional exploration strategies. Approximately 300 groundwater samples were collected over the southern Curnamona Province to test whether this medium could be helpful in the search for hidden mineral deposits. Sulphur, Sr and Pb isotope composition of the groundwaters were determined and S excess (SXS), i.e., the amount of S that can be ascribed neither to evaporation nor to mixing, was calculated. Many samples were recognised to have undergone an addition of 34S-depleted S, which can be attributed to oxidation of sulfides with a Broken Hill type ?34S signature (average ?0‰-V-CDT). Furthermore, Sr isotopes identify the broad types of bedrock that the groundwater has been interacting with, from the less radiogenic Adelaidean rocks (and minerals) in the west (groundwater 87Sr/86Sr ratio as low as 0.708) to the highly radiogenic Willyama Supergroup in the east (87Sr/86Sr ratio up to 0.737). The groundwaters have 207Pb/204Pb and 206Pb/204Pb ratios comparable to, or intermediate between, various mineralisation types recognised in the area (Broken Hill, Rupee, Thackaringa, etc., types). The few samples taken in the vicinity of known mineralisation yield positive indicators (positive SXS, low ?34S, 87Sr/86Sr signature of bedrock type and Pb isotope fingerprinting of mineralisation type). This study also highlights several new locations under sedimentary cover where these indicators suggest interaction with mineralisation.
Abstract: A novel analytical technique for isotopic analysis of dissolved and particulate iron (Fe) from various marine environments is presented in this paper. It combines coprecipitation of dissolved Fe (DFe) samples with Mg(OH)(2), and acid digestion of particulate Fe (PFe) samples with double pass chromatographic separation. Isotopic data were obtained using a Nu Plasma MC-ICP-MS in dry plasma mode, applying a combination of standard-sample bracketing and external normalization by Cu doping. Argon interferences were determined prior to each analysis and automatically subtracted during analysis. Sample size can be varied between 200 and 600 ng of Fe per measurement and total procedural blanks are better than 10 ng of Fe. Typical external precision of replicate analyses (1S.D.) is +/-0.07 per thousand on delta(56)Fe and +/-0.09 per thousand on delta(57)Fe while typical internal precision of a measurement (1S.E.) is +/-0.03 per thousand on delta(56)Fe and +/-0.04 per thousand on delta(57)Fe. Accuracy and precision were assured by the analysis of reference material IRMM-014, an in-house pure Fe standard, an in-house rock standard, as well as by inter-laboratory comparison using a hematite standard from ETH (Zürich). The lowest amount of Fe (200 ng) at which a reliable isotopic measurement could still be performed corresponds to a DFe or PFe concentration of approximately 2 nmol L(-1) for a 2 L sample size. To show the versatility of the method, results are presented from contrasting environments characterized by a wide range of Fe concentrations as well as varying salt content: the Scheldt estuary, the North Sea, and Antarctic pack ice. The range of DFe and PFe concentrations encountered in this investigation falls between 2 and 2000 nmol L(-1) Fe. The distinct isotopic compositions detected in these environments cover the whole range reported in previous studies of natural Fe isotopic fractionation in the marine environment, i.e. delta(56)Fe varies between -3.5 per thousand and +1.5 per thousand. The largest fractionations were observed in environments characterized by redox changes and/or strong Fe cycling. This demonstrates the potential use of Fe isotopes as a tool to trace marine biogeochemical processes involving Fe.
In Uranium in the Pine Creek Geosyncline, J. Ferguson and A.B. Goleby, eds. STI/PUB, Applied Publishing Ltd. Wilmette, Illinois, p. 74-77.
Abstract: Seventeen exploration drill holes in the vicinity of the Jabiluka One and Jabiluka Two deposits were logged for Eh-pH and conductivity at 5 metre intervals to depths of up to 195 metres below ground surface. Forty-seven water samples from exploration drill holes, augered holes on the Magela flood plain and from two billabongs in the vicinity of the deposits were collected and analyzed. Analyses for pH and Fe were conducted in the field, and further analyses for major ions Ca2+, Mg2+, Na+, K+, SO42-, Cl-, HCO3- and Si and minorelements Zn, Cd, Pb, Cu and U were conducted in the laboratory. The in situ Eh-pH and conductivity measurements, and analyses for major and minor elements of ground waters suggest that deep-lying chlorite-graphite schists containing the uranium mineralization are well protected from, or do not react rapidly with, ground water under present-day conditions, i.e. the schists of the Cahill Formation are a stable host for uranium mineralization at depth. In the vicinity of the Magela flood plain where the Cahill Formation and the permanent water table are close to the surface, some samples were found to contain high concentrations of sulphate, zinc, lead and iron. These same samples were characterized by low pH's in the pH range 3.0-4.0. The anomalies suggest weathering of sulphides associated with the mineralized Cahill Formation, where the schists are at shallow depths and in an oxidizing environment. The anomalies are not, however, necessarily indicative of zones of uranium enrichment in this formation.
Abstract: Groundwater geochemistry assists in determining the character of deep geological or geophysical targets from a limited number of boreholes, refining location, size and orientation of host target zones, or directly demonstrating presence of alteration or mineralisation. By themselves, uranium analyses can be very misleading in applying groundwater to U exploration. Detailed analyses of multi-element data is required to properly interpret water data, sorting false from significant indicators. Examples from a range of Australian areas reinforce these comments and show that, sometimes, the U indicator is a mineral assemblage, not a U concentration. Ready availability of modelling software and chemical databases allow exploration implications from groundwater data to be easily accomplished.
Abstract: A geochemical survey involving the collection and analysis of about 2000 well water samples from an area of roughly 25,000 km2 was carried out during the 1975 field season over parts of the Carboniferous basin of eastern Canada. This report describes the results of 1721 regional well sites. Three samples of water were collected from each site and analyzed in four different laboratories for twenty constituents. The distribution and relationships of U, Rn, He F, CH4, Zn, Cu, Pb, Mn, Fe, pH, suspended matter, depth of well, conductivity and alkalinity are described.
The elements U, Rn, He, F, along with conductivity and alkalinity, show systematic regional patterns indicating broad regional belts of element enrichment which are being leached by circulating groundwaters. The close spatial association of these elements over many tens of miles suggests chemical reaction cells or fronts similar to those observed in the uranium mining districts of Colorado and Wyoming in the United States and elsewhere. Their relatively weak character suggests an intermediate cycle in the cyclic enrichment hypothesis believed to be responsible for the formation of epigenetic uranium ore deposits.The heavy elements Zn, Cu, Pb, Mn, and Fe show positive correlation with each other but their spatial distribution is more spotty than that of the uranium elements. Broadly speaking the anomalies of these elements cluster mainly on the southern border of the survey area. Most of the anomalies can be explained in terms of known mineral occurrences. The most prominent CH4 anomaly is located south of Moncton and is believed to be due to the old St. Josephs gas and oil field. Several weaker CH4 anomalies are probably generated by swamps and peat bogs.
Abstract: As part of our exploration programs for unconformity-related uranium deposits, we have studied the chemistry of deep ground waters from throughout the Athabasca Basin. Samples have been collected from routine, small-diameter, exploration diamond drillholes, and we have placed considerable emphasis on ensuring that they represent true ground waters.
We have measured both major and minor constituents, including various uranium daughter products. Ground-water samples collected from the vicinity of uranium mineralization have consistently high levels of uranium, radium, radon and helium. Although we have not been able to establish the maximum extent of the hydrogeochemical anomalies in this environment, we have detected anomalies at distances of up to tens of meters from known mineralization.
Abstract: The source of the acid, high sulfate, and high heavy-metal content of some spring waters near the head of Fourmile Canyon probably is a concealed oxidizing sulfide deposit. Spring waters near the mouth of the canyon have a high Mo content, but the source of the Mo is not known.
Techniques of Water Resources Investigations of the U.S. Geological Survey, Book 5, Chapter A1.
Abstract: Chapter Al of the laboratory manual contains methods used by the U.S. Geological Survey to analyze samples of water, suspended sediments, and bottom material for their content of inorganic constituents. Included are methods for determining the concentration of dissolved constituents in water, the total recoverable and total of constituents in water-suspended sediment samples, and the recoverable and total concentrations of constituents in samples of bottom material. The introduction to the manual includes essential definitions and a brief discussion of the use of significant figures in calculating and reporting analytical results. Quality control in the water-analysis laboratory is discussed, including the accuracy and precision of analyses, the use of standard-reference water samples, and the operation of an effective quality-assurance program. Methods for sample preparation and pretreatment are given also. A brief discussion of the principles of the analytical techniques involved and their particular application to water and sediment analysis is presented. The analytical methods of these techniques are arranged alphabetically by constituent. For each method, the general topics covered are the application, the principle of the method, the interferences, the apparatus and reagents required, a detailed description of the analytical procedure, reporting results, units and significant figures, and analytical precision data, when available. More than 126 methods are given for the determination of 70 inorganic constituents and physical properties of water, suspended sediment, and bottom material.
Abstract: In the Pine Creek Geosyncline, fast moving, annually recharged, low-salinity ground waters dissolve uranium- and magnesium-enriched gangue minerals from mineralized aquifer rocks. The level of dissolved uranium depends on prevailing pH, Eh, salinity and degree of adsorption, which limits its effectiveness as an exploration indicator. Near each known deposit, leaching of magnesium-enriched gangue minerals produces ground waters with very similar major-element concentration plots, the shape of which constitutes a mineralized aquifer “signature”. Gangue minerals also supply high levels of Mg2+ (expressed as NMg = [Mg2+]/[Ca2+ + Mg2+ + Na+ + K+] in milliequivalents per litre) to contained ground waters, NMg > 0.8 being common in ground waters from mineralized aquifers at each Pine Creek Geosyncline deposit. Data from Ranger One No. 3 ore body illustrates how progressive mixing of waters from mineralized and unmineralized aquifers causes graded reductions in NMg, which, when plotted onto a ground plan, delineate a hydrogeochemical aureole. High NMg (> 0.8) coincides with high uranium concentration (> 20 ?g/l of U) in ground waters near Nabarlek and Ranger. Because pH-Eh conditions in aquifers at Jabiluka depress uranium solution, < 10 ?g/l of U is present, although NMg values are generally > 0.8. To date NMg has always been < 0.8 in nonmineralized aquifer waters, whereas uranium may be > 50 ?g/l in ground waters from felsic igneous aquifers, which can be identified as uneconomic by low (< 0.4) NMg, and by a fixed relationship between uranium and co-leached species such as F- and soluble salts. Measurements of pH, Eh, salinity, Fe(II), Ca, Mg, Na, K, Cl, SO4, total carbonate, phosphate, F-, Cu, Pb, Zn and U in waters from 48 percussion holes in and near the Koongarra ore bodies have been related to mineralogy recorded in drill logs. The composition of waters from 20 holes near and along strike from known mineralization, fitted the mineralized aquifer "signature", had NMg > 0.8 and uranium up to 4100 ?/l. These data confirm the use in this region of NMg as a hydrogeochemical indicator of uranium mineralization; they also indicate additional zones of possible mineralization.
Abstract: Apparently anomalous levels of Cu, Pb, Zn (up to 6.1, 26.0 and 10.8 mg 1?1 respectively) and Ra (2000 pg 1?1) have been noted in groundwaters from 28 drill holes within a 20 km × 20 km zone centred about a 10 times background airborne radiometric anomaly near Lake Maurice in the Great Victoria Desert in South Australia. Within 6 km of the anomaly centre the water table depth is generally less than 10 m, increasing to approximately 30 m in the drill holes furthest from the anomaly centre. All waters are very acid (pH 3.6 to 5.8) and deficient in carbonate species (all <0.5 mg 1?1) but saturated with respect to calcium sulphate minerals. XRD traces of drill hole cuttings show the presence of quartz and halite at every sample site, pyrite at 75% of sites, variable amounts of kaolinite and muscovite at all sites, and variable amounts of feldspar, jarosite, calcium sulphate minerals, hydrated iron oxides, siderite, chlorite and calcite at certain locations only. Salinity of waters is very high ranging from that approximating sea water (Ionic strength (I) = 0.93 and Cl? = 19 g 1?1) to approximately six times sea water salinity (I = 4.61 and Cl? = 120 g 1?1).
Abstract: Weathering of mineral deposits under glacial cover may slowly release elements to the groundwater that disperse forming secondary geochemical halos. The Tillex Cu-Zn deposit subcrops beneath a sand aquifer and glacial clay/silt aquitard that extends to the surface. A conceptual model was developed based on hydrologic, geochemical and mineralogical data to describe dispersion in the aquifer and aquitard overlying the mineralization. In the recharge zone, dissolved oxygen oxidizes detrital sulphides in the aquifer and aquitard, which promotes the dissolution of carbonate minerals, increasing the concentrations of Ca and Mg. Iron released by sulphide oxidation precipitates as Fe(III) oxyhydroxides. Trace metals released during sulphide oxidation may be subsequently adsorbed onto, or co-precipitated with, clays and Fe oxyhydroxides. Sulphate-reducing conditions occur deep in the aquifer over the mineralization and there is no evidence of metal transport upward through the overlying sand and clay/silt overburden. The sulphate-reducing conditions are not favourable for the development of a plume of weathering products that could represent a target for mineral exploration. The one-dimensional reactive transport model PHREEQC was used to test the conceptual model by simulating the hydrogeochemical conditions in the aquitard. The observed data correspond well to the model results, suggesting that the conceptual model is reasonable.
Abstract: The hydrogeochemistry of the Keno Hill area, Yukon is discussed in terms of the statistical treatment of analytical data obtained on 739 stream and 172 spring water samples. The surface and spring waters are S04-HC03 waters dominated mainly by the presence of Ca and Mg with small amounts of Fe, Na, K, and Mn. Some surface and spring waters are characterized by relatively high contents of Zn. Moving average - residual element maps show that high values for so4, CXM (cold extractable metal), and SO 4/Cl in the waters from the area outline the zones containing Pb -Zn-Ag deposits and pyritiferous rocks. The distribution of Cl in the waters exhibits no relationship to the known mineral deposits. Relatively high Cl contents correlate mainly with the presence of limestone and dolomite units. Spring waters that leach the known siderite-sulphide lodes exhibit appreciably higher geometric means for various constituents including HCO 3, SO 4, SiO 2, F, and various cations, particularly Zn, compared with the spring waters in the region as a whole. They also have a higher pH but lower Cu contents. Springs exhibiting relatively high values in their anionic and cationic content may be reflecting hidden mineral deposits, and their source areas should be thoroughly prospected.
Abstract: There is currently widespread interest in the exploration community worldwide in the development of methods to locate deeply buried mineralisation. In the application of geochemical methods, some success has been achieved using the selective extraction of mobile and weakly bonded forms of elements (MWBE) in overburden. Studies in Russia commenced in the 1960s, and have continued in Russia and in other countries to the present time. This paper presents some examples of experimental and applied research carried out in Russia, specifically by members of VITR and then VIRG NPO Rudgeofizika (St. Petersburg). In particular, some characteristics of MWBE anomalies and rates of MWBE migration are illustrated, with reference to several case studies in geochemical exploration for base metal and precious metal deposits.
Abstract: Neutron activation analysis of 67 samples of water draining from gold-barren and gold-enriched sedimentary, igneous, and metamorphic rocks of the Colorado Front Range reveals a relatively small range in total gold content (nondetectable to 150 nanograms per liter). "Solute" gold concentrations were generally higher than particulate gold concentrations and both were unrelated to rock or water types. The data suggest the occurrence of a spring flush out of "solute" gold in groundwater discharge during the snow-melt recharge period but indicate that direct hydrogeochemical prospecting for gold is unpromising.
Abstract: The hydrogeochemistry of the Yilgarn Craton and its margins has been extensively investigated, with particular emphasis on the chemistry of Au. Four groundwater regions have been delineated based on variations in salinity, acidity and oxidation potential: (1) Northern (N Yilgarn and margins) - Fresh and neutral, trending more saline in the valley axes; (2) Central – Neutral and brackish (commonly <1% TDS) to saline (about 3% TDS), trending to hypersaline (10-30% TDS) at the salt lakes, with common increases in salinity with depth; (3) Kalgoorlie – Commonly acid (pH?3-5), except where buffered by extremely alkaline materials (e.g. ultramafic rocks), and saline within the top part of the groundwater mass, trending more neutral (pH?5-7) and hypersaline at depth and within a few kilometres of salt lakes; and (4) Eastern (E Yilgarn and Officer Basin) - Saline to hypersaline, neutral to acid and reducing. Dissolved concentrations of many ions are low, due to the presence of lignites in the channel sediments.These regional variations have major effects on the concentrations of many elements. Aluminium, Li, Y, REE and U are dominantly controlled by pH and thus have higher concentrations in acid groundwaters, such as those in the Kalgoorlie region. Dissolved concentrations of Mn, Co, Ni, Cu and Zn are less closely correlated with acidity, and show scope for lithological discrimination, but there is no apparent relationship with Au mineralization. Dissolved Cr shows an absolute correlation with ultramafic rocks, apparently irrespective of pH, possibly due to its presence as chromate (i.e. Cr6+ as CrO42?). Concentrations of As, Sb Mo, W and Bi are low in acid groundwaters, but are higher above pH?6.5, particularly in the Central region. Therefore, acid groundwaters (particularly in the Kalgoorlie district) will be poor media for the use of these elements as exploration pathfinders. Molybdenum differs from the other elements in this group in having significant concentrations in acid groundwaters, although lower than in neutral and alkaline groundwaters.
Dissolved Au is commonly the best pathfinder for Au mineralization. It occurs dominantly as halides (chloride and/or iodide) and has enhanced concentrations (to >1?ppb) under the acid/saline/oxidizing conditions common in the Kalgoorlie region, whereas concentrations in the northern Yilgarn are two orders of magnitude less. This implies that supergene Au remobilization should be considerably less in the northern Yilgarn than in the Kalgoorlie region. Additionally, the threshold dissolved Au concentration as used for Au exploration differs significantly between regions.
Abstract: Ground-water, alluvium, and bedrock samples were collected from drill holes near the Chimney Creek, Preble, Summer Camp, and Rabbit Creek disseminated gold deposits in northern Nevada to determine if Au and ore-related metals, such as As, Sb, and W, are being hydromorphically mobilized from buried mineralized rock, and, if they are, to determine whether the metal-enriched ground water is reacting with the alluvial material to produce a geochemical anomaly within the overburden. Results of chemical analyses of drill-hole water samples show the presence of hydromorphic dispersion anomalies of Au, As, Sb, and W in the local ground-water systems associated with these deposits. Background concentrations for Au in the ground water up-gradient from the buried deposits was less than 1 nanogram per liter (ng/L), near the deposits the Au values ranged from 1 to 140 ng/ L, and in drill holes penetrating mineralized rock, concentrations of Au in the ground water were as high as 4700 ng/L. Highest concentrations of Au were found in ground-water samples where the measured Eh and the distribution of arsenic species, arsenite [As(III)] and arsenate [As(V)], indicated oxidizing redox potentials. Similarly, As, Sb, and W concentrations in the ground water near the deposits were significantly enriched relative to concentrations in the ground water up-gradient from the deposits. In general, however, the highest concentrations of As, Sb, and W occurred in ground-water samples where the measured Eh and the distribution of arsenic species indicated reducing conditions. Arsenic concentrations ranged from 9 to 710 micrograms per liter (?g/L); Sb, from less than 0.1 to 250 ?g/L; and W, from 1 to 260 ?g/L.. In addition, analysis of sequential dissolution and extraction solutions of drill cuttings of alluvium and bedrock indicate geochemical anomalies of gold and ore-related metals in the overburden at depths corresponding to the location of the present-day water table. This relationship suggests that water-rock reactions around these buried deposits are active and that this information could be very useful in exploration programs for concealed disseminated gold deposits.
Cost-effective protocols for the collection, filtration and preservation of surface waters for detection of metals and metalloids at ppb (µg l-1) and ppt (ng l-1) levels.
Aquatic Effects Technology Evaluation Program (Task Force on Water Quality Issues), AETE Project 3.1.3, Canmet, Ottawa.
Abstract: 70 water samples. Dissolved gold discriminated from particulate gold by filtration through a 1.2-mu filter. The particulate gold concentrations showed excessive scatter, which made their use for locating gold anomalies unpromising. Dissolved gold occurred in concentrations ranging from < or =0.3 to 2.5 parts per trillion to as high as 130 parts per trillion. The limit of detection of the analytic method was 0.3 parts per trillon.--Modified journal abstract.
Abstract: Fifty-four surface and twenty drill-hole waters were sampled in the vicinity of the old Eustis mine in the Eastern Townships of Quebec. Some of these waters were tested periodically over a three-month period. The purpose of the investigation was to develop a method for locating sources of anomalous waters using chemical analyses together with geomorphic and geologic evidence. Techniques have been developed which use chemical and hydrologic theory to estimate travel distance and location of the approximate source area of a water. The travel distance can be approximated as a function of hydraulic head, sodium concentration in the water, and an approximate constant which must be derived for the area. Water samples having anomalous concentrations of copper or zinc can be ascribed, in the specific region of this investigation, partly to contamination from mine workings (35%), partly to known mineralization (25%), and partly to unknown causes (40%).
I. Rates presentation from 4th workshop on metal speciation and contamination of aq, H.E. Allen chairman, June 8-11, Jekyll Island, GA.
Abstract: Several published adsorption and desorption (sorption) data sets have been recalculated and replotted in the course of developing and testing data-linearization techniques. Data sets that yielded results that appeared anomalous and two other data sets, one with adsorption time series for several metals and another with extensive particle size data, are examined in detail to better understand the factors that result in sorption data artifacts. Drying (and certain other pretreatments), uncontrolled (and frequently unmeasured) pH, unknown valence changes of redox-sensitive metals, unmonitored bacterial growth, and experimentally imposed differences in time-to-equilibrium were found to contribute to the large uncertainties in much of the published sorption data.
Abstract: Rare earth elements (REE) were determined in groundwater samples collected from a thick till and clay-rich aquitard sequence located in southern Saskatchewan, Canada. The groundwaters are Na-Mg-SO4-type waters that range from highly concentrated brines (e.g., I up to 2 moles/kg) near the ground surface to relatively dilute waters (I ? 0.04 moles/kg) at depth. The majority of these groundwaters have pH values between 7 and 8, although the deepest samples are more alkaline (9 ? pH ? 9.6). Groundwater REE concentrations are relatively constant in the overlying till but increase by up to a factor of 50 in the underlying clay bedrock. Shallow groundwaters have heavy REE (HREE)-enriched shale-normalized patterns, whereas the REE patterns of the deep groundwaters are relatively flat. Solution complexation modelling indicates that variations in REE patterns reflect differences in solution complexation across the REE suite. In the shallow groundwaters, strongly adsorbed, positively charged carbonate complexes (LnCO3+), sulfate complexes (LnSO4+), and free metal ion species (Ln3+) dominate the speciation of light REEs (LREE), whereas HREEs occur chiefly as more stable, negatively charged dicarbonato complexes [i.e., Ln(CO3)2?)]. For the deepest groundwaters, however, all of the REEs are predicted to occur in solution as dicarbonato complexes. The large HREE enrichments of the shallow groundwaters reflect the greater affinity of the positively charged LREE solution species to adsorb to clay minerals or coatings on clay minerals in the aquitard sequence compared to the more stable, negatively charged HREE dicarbonato complexes. On the other hand, the flat REE patterns of the deep groundwaters reflect the dominance of the negatively charged dicarbonato complex for all REEs. The solution complexation model along with the strong positive correlation between REEs and [CO32?]F(0.79 ? r ? 0.95), and to a lesser extent pH (0.57 ? r ? 0.72), indicates that carbonate ion concentrations, and thus pH, exert important controls on aqueous REE concentrations in these groundwaters.
Abstract: Middle rare earth element (MREE) enriched rock-normalized rare earth element (REE) patterns of a dilute acidic lake (Colour Lake) in the Canadian High Arctic, were investigated by quantifying whole-rock REE concentrations of rock samples collected from the catchment basin, as well as determining the acid leachable REE fraction of these rocks. An aliquot of each rock sample was leached with 1 N HNO3 to examine the readily leachable REE fraction of each rock, and an additional aliquot was leached with a 0.04 M NH2OH · HCl in 25% (v/v) CH3COOH solution, designed specifically to reduce Fe-Mn oxides/oxyhydroxides. Rare earth elements associated with the leachates that reacted with clastic sedimentary rock samples containing petrographically identifiable Fe-Mn oxide/oxyhydroxide cements and/or minerals/amorphous phases, exhibited whole-rock-normalized REE patterns similar to the lake waters, whereas whole-rock-normalized leachates from mafic igneous rocks and other clastic sedimentary rocks from the catchment basin differed substantially from the lake waters. The whole-rock, leachates, and lake water REE data support acid leaching or dissolution of MREE enriched Fe-Mn oxides/oxyhydroxides contained and identified within some of the catchment basin sedimentary rocks as the likely source of the unique lake water REE patterns. Solution complexation modelling of the REEs in the inflow streams and lake waters indicate that free metal ions (e.g., Ln3+, where Ln = any REE) and sulfate complexes (LnSO4+) are the dominant forms of dissolved REEs. Consequently, solution complexation reactions involving the REEs during weathering, transport to the lake, or within the lake, cannot be invoked to explain the MREE enrichments observed in the lake waters.
Environmental geochemistry of shale-hosted Ag-Pb-Zn massive sulfide deposits in northwest Alaska: natural background concentrations of metals in water from mineralized areas.
Abstract: Groundwater quality data was collected from published sources and estimated when necessary for three sandstone-type uranium deposits in Texas and Wyoming. The purpose of the study was to compare the merits of using the computed saturation state of the groundwater with respect to uranium minerals, to that of single-element tracers in groundwater for geochemical prospecting. The uranium minerals considered were carnotite and tyuyamunite within oxidized deposits in the Catahoula Tuff in southern Texas, and uraninite and coffinite in reduced deposits within the Oakville Sandstone in southern Texas, and Wasatch Formation in northeast Wyoming. Groundwater chemical maps and profiles were constructed for the three sites, showing locations of known and probable uranium mineralization. The single tracer elements and parameters considered in the comparison were pH, Fe, SO4, V, U, Ra, As, Mo and Se. Mineral-saturation results were the most dependable evidence for uranium mineralization, and showed systematic trends towards saturation at distances as great as 300 m from the ore. In general, the next best indicators of ore were uranium concentrations, and vanadium concentrations in the oxidized deposit. Single tracer species As, Mo, Se and V were at or below detection in groundwaters near the reduced deposits, and except for V, provided ambiguous information in the oxidized deposit. Because of its high mobility, radium was displaced from the mineralization in the direction of groundwater flow at the Oakville Site, although its success as an ore pathfinder was equal to that of dissolved uranium at the Wasatch Site.
Refinement of the thermodynamic properties of uranium minerals and dissolved species, with application to the chemistry of groundwaters in sandstone-type uranium deposits.
Layton-Matthews, D., Peter, J. M., Scott, S. D. and Leybourne, M. I.
Distribution, mineralogy, and geochemistry of Selenium in felsic volcanic-hosted Massive Sulfide Deposits of the Finlayson Lake Area, Yukon Territory, Canada.
Abstract: Metallogenic studies that try to identify the geochemical fluxes of metals in the lithosphere leading to ore formation have a higher sensitivity when the traditional mining data, based on grades and tonnages, are normalized to crustal element abundances, and derivative units such as clarke of concentration and tonnage accumulation index are used. This technique has been applied to the world-class deposits of all industrial metals, i.e., to 34 metals plus the rare earth elements and platinoid groups. The lower magnitude limits for inclusion in the giant and supergiant categories (ore metal content in a deposit/metal clarke >1X10 11 metric tons (t) and 10 12 t of average crustal material, respectively) have been established for each metal. There are, presently, 486 giant and 61 supergiant metal accumulations of the various metals in 446 deposits and districts.
EPRI RP-910-1, Electric Power Research Institute, Palo Alto, CA.,
Abstract: This report presents the results of laboratory experiments that evaluated the feasibility of using freshly precipitated ferric oxyhydroxide to extract trace elements from power plant wastes.
Abstract: Suspended sediments from groundwaters were recovered from two undisturbed massive sulfide deposits (Halfmile Lake and Restigouche) in the Bathurst Mining Camp, New Brunswick, Canada. Suspended sediments in most groundwaters are dominated by quartz and aluminum silicate minerals. Fe oxyhydroxides are probably present as surface coatings in addition to amorphous phases. Suspended sediments from groundwaters recovered from boreholes that intersect the Restigouche orebody near its surface expression consist primarily of Fe, Pb, and Zn sulfate and Fe sulfide minerals. In general, suspended sediments are depleted in the mobile elements K, Rb and Cs compared to host rock-types from both deposits. Suspended sediments show generally flat element- enrichment patterns normalized to respective felsic host-rocks for most other elements, but exhibit strong enrichments in Pb, F e, Co, Zn, Ag, and Eu. Iron-oxide-rich suspended sediments from a borehole that penetrates massive sulfide gossan at the Halfmile Lake deposit are more strongly depleted in most elements relative to other sediments. At the Restigouche deposit, the degree of enrichment in Pb, Zn, Cu, and Ag in the suspended sediment is greater than for the deeper Halfmile Lake deposit. Compared to coexisting groundwaters, suspended sediments are relatively enriched in Al, Fe, Pb, and relatively depleted in Ca, Sr, and Mg. Potassium and Rb are generally more strongly fractionated into the suspended sediment phase than other mobile elements, suggesting that their abundance in the groundwaters is controlled by secondary phases (illite - white mica), consistent with SE M and XRD data. Comparisons of groundwaters, suspended material and host rocks yield important information regarding relative fractionation of major and trace elements among these reservoirs. Suspended sediments proximal to massive sulfide ore have elevated Fe/Ti and base-metal contents; with increasing distance away from mineralization, Al/(Al + Fe + Mn) values increase, base-metal contents decrease, and Zn/Pb values increase. The elevated base-metal content of suspended sediments associated with massive sulfides is important, as mining activities in the Bathurst mining camp can result in changes in groundwater Eh-pH conditions, potentially resulting in greater dispersion of metals that are presently strongly sorbed onto sediments.
Goodfellow, W.D. (ed). Geological Association of Canada, Mineral Deposits Division, Special Publication No. 5, p. 1007-1034.
Abstract: Ground and surface waters are important media for the geochemical exploration of many different styles of mineralization. Water-transported (hydromorphic) metals can develop anomalous concentrations and reveal hidden mineralization directly (dissolved phase) and by adsorption/precipitation reactions with suspended and bed-load stream sediments (labile fraction). Groundwater recharges to depth, resulting in greater likelihood of interacting with buried mineralization compared to surface geochemical methods. Advances in the understanding of ore formation processes, water-rock interaction, and metals transport/attenuation in the secondary environment are enhancing the efficacy of aqueous geochemical exploration. Overcoming the issue of false anomalies is aided by traditional and nontraditional isotopic techniques to more directly fingerprint metal sources, in particular through the use of Pb and S isotopes. Advances in analytical technologies should permit such isotopic analyses, traditionally not used by the exploration industry due to cost, to become as routine as elemental analyses are today. This paper synthesizes the current thinking and state of the art of surficial geochemical methods that are useful to the mineral exploration industry. Examples of how ground and surface waters vector to mineralization are presented for a number of deposit types (volcanogenic massive sulphide, gold, porphyry copper, sedimentary exhalative, unconformity
uranium, kimberlite diamond, and Cu-Ni-PGE). The most successful aqueous-phase indicators of mineralization are those that are ore-associated and mobile in solution.
Abstract: The Pampa del Tamarugal in northern Chile is a gravel plain, part of the hyperarid Atacama desert. Soil geochemical surveys over the pampa using partial extraction analyses identified a large, >100-km2 geochemical anomaly for Cu. Subsequent analyses showed unusually high concentrations of elements that are associated with copper porphyry deposits, Mo, As, and Se. The soils are saline (NaCl) and contain high concentrations of Br and I, which are abundant in ground waters from northern Chile. The anomaly lies west of one of the world’s most important copper porphyry districts, which includes the Chuquicamata, Radomiro Tomic, and El Abra deposits. Follow-up drilling in the center of the anomaly, through ~300 m of piedmont gravel cover, revealed barren andesitic basement rocks. The soil anomalies were caused by ground water reaching the surface, then evaporating. Both ground waters and soils share a common element assemblage, with higher concentrations of Mo, As, and Se than Cu. The former dissolve as anions in ground water, which can travel far from their source, whereas dispersion of Cu2+ is restricted by adsorption. The soil anomaly is interpreted to be a "fossil" anomaly, preserved by the hyperarid climate. To the south the anomaly is cut by an alluvial fan; another nearby fan has been dated at ~7 Ma. To the west the anomaly was eroded in the flood plain of the Rio Loa. Prior to the present ~50-m-deep incision of the Rio Loa, the water table in the area of the anomaly may have been higher than the present depth of 33 to 55 m, facilitating capillary rise of water to the surface. We suggest that the source for the anomaly was the El Abra deposit, 75 km east and updrainage from the anomaly.
In "Proceedings of Exploration 07: Fifth Decennial International Conference on Mine, p. 201-221.
Abstract: Groundwater is an important medium for geochemical exploration of many different styles of mineralization, including porphyry copper, volcanogenic massive sulfide (VMS), sandstone uranium, and gold. Groundwater recharges to depth, resulting in greater likelihood of interacting with buried mineralization compared to surface geochemical methods, and thus providing a three dimensional perspective. Advances in understanding of ore formation processes, water-rock interaction and metals transport/attenuation in the secondary environment are enhancing the efficacy of groundwater geochemical exploration. This paper describes key techniques and methodologies for sampling, analysis and interpretation of groundwater geochemical data, and provides two different approaches for use by industry: routine exploration and research approaches. New advances in analytical methods are providing new isotopic systems and improving the cost and speed of traditional isotopic techniques, which can greatly aid in interpretation of water sources, water-rock reactions and fingerprinting of ore sources. Case studies are presented for the use of groundwater geochemistry around a porphyry copper deposit in the hyperarid Atacama Desert of Chile, and VMS mineralization in a mature mining camp in Canada. This paper also summarizes key elemental associations for successful utilization of aqueous geochemistry in mineral exploration. The most successful aqueous-phase indicators of mineralization are those that are ore associated and mobile in solution.
Chemical Geology, 247, 208-228. DOI 10.1016/j.chemgeo.2007.10.017.
Abstract: We collected groundwaters in and around a large (313 Mt at 1.08% Cu and 0.3% cutoff) undisturbed porphyry copper deposit (Spence) in the hyperarid Atacama Desert of northern Chile, which is buried beneath 30-180 m of Miocene piedmont gravels. Groundwaters within and down-flow of the Spence deposit have elevated Se (up to 800 ?g/l), Re (up to 31 ?g/l), Mo (up to 475 ?g/l) and As (up to 278 ?g/l) concentrations compared to up-flow waters (interpreted to represent regional groundwater flow). In contrast, Cu is only elevated (up to 2036 ?g/l) in groundwaters recovered from within the deposit; Cu concentrations are low down gradient of the deposit. The differential behavior of the metals/metalloids occurs because the former group dissolves as anions, enhancing their mobility, whereas the base metals dissolve as cations and are lost from solution most likely through adsorption to clay surface exchange sites and through formation of secondary copper chlorides, carbonates, and oxides. Most groundwaters within and down-flow of the deposit have Eh-pH values around the FeII/FeIII phase boundary, limiting the impact of Fe-oxyhydroxides on oxyanions mobility. Se, Re, Mo, and As are all mobile (with filtered/unfiltered samples ? 1) to the limit of sampling 2 km down gradient from the deposit. The increase in ore-related metals, metalloids, and sulfate and decrease in sulfate-S isotope ratios (from values similar to regional salars, + 4 to + 8- ?34SCDT to lower values closer to hypogene sulfides, + 1 to + 4-- ?34SCDT) is consistent with active water-rock reactions between saline groundwaters and the Spence deposit. It is likely that hypogene and/or supergene sulfides are being oxidized under the present groundwater conditions and mineral saturation calculations suggest that secondary copper minerals (antlerite, atacamite, malachite) may also be actively forming, suggesting that supergene and exotic copper mineralization is possible even under the present hyperarid climate of the Atacama Desert.
Abstract: Ground water recovered from fractured bedrock at the Halfmile Lake, Restigouche, and Stratmat Main zone Zn-Pb volcanogenic massive sulfide deposits, Bathurst Mining Camp, Canada, is compositionally distinct. At the Halfmile Lake deposit, ground water is dominated by low total dissolved solids (TDS < 100 mg/l) and Ca-HCO3-type compositions, although deeper ground water has higher TDS (up to 230 mg/l) and more evolved Na-HCO3-type compositions. The geochemical and stable isotope compositions (?18OVSMOW = –.70 to 13.09 and ?DVSMOW = 97.8 to 81.5) of the Halfmile Lake deposit ground water indicate that this ground water is dominated by modern meteoric water, which is rapidly recharged to depth along steep structures. Ground water at the Restigouche deposit varies in composition from shallow (<200 m) Ca-HCO3 and Ca-SO4-type to high TDS Na-Cl-type water with increasing depth (>200 m). The stable isotope composition of the saline ground water indicates that this water was not recharged under the present climatic regime. Shallow Ca-SO4 -type ground water proximal to massive sulfides at the Restigouche and Stratmat Main zone deposits contains elevated sulfate (up to >1,000 mg/l) and base metals (up to 4,200 ?g/l Zn and 1,400 ?g/l Pb). Proximity of the ore deposit to surface and, therefore, to O2-rich recharge water influences sulfide oxidation and ground-water metal contents. The degree to which the massive sulfides are oxidized depends on the depth of penetration of dissolved oxygen and flux rates, which are controlled by the permeability of the rocks and local hydrological gradients. Transport of metals away from massive sulfides depends on physical factors that include the ground-water flow system and the degree of connectivity between the ground-water and surface water environments, as well as chemical factors that influence the solubility of metals. These chemical factors include ground-water pH, redox state, metal adsorption, and the mobility of colloids and suspended particles within the ground-water system. Oxidation of massive sulfides at the Restigouche and Stratmat Main zone deposits may occur below the water table, and pH values in the ground water are buffered to circumneutral values that limit metal mobility and transport.
Abstract: We report results of a detailed geochemical study of surface waters from several streams in a small catchment in northern New Brunswick, Canada. Rocks in the catchment represent metamorphosed (greenschist facies) felsic volcanic rocks, metavolcaniclastic sediments, and mafic volcanic rocks; no massive carbonate or evaporite lithologies are present, thus providing an excellent opportunity to investigate the relative influence of silicate weathering compared to trace carbonate (vein and disseminated) dissolution and the influence of volcanogenic massive sulfide (VMS) mineralization on surface water chemistry. Surface waters, catchment lithologies and stream sediments were analyzed for a full suite of major and trace elements. Surface waters are dilute (typically < 60 mg/L total dissolved solids), and are of dominantly Ca-HCO3-type. Most waters have Ca/Namolar > 1. The major ion chemistry of the waters is consistent with binary mixing between silicate weathering and dissolution of trace calcite; Si/Camolar relationships suggest that trace calcic silicates are insignificant compared to calcite as a Ca source, and PO4 concentrations of waters are too low for apatite to be a major source of Ca. Host rocks have highly variable Ca/Na, Mg/Na and K/Na values complicating the assignment of a silicate end-member. Geochemical modeling indicates that surface waters range from essentially 100% of the Na and Ca being derived by silicate weathering, to being dominantly controlled by trace calcite, also consistent with mass balance calculations. The Cl/Ca ratios are consistent with the host felsic and mafic metavolcanic rocks as being an important source of Cl in addition to precipitation. The host lithologies have much larger variations in Mg/Na, Ca/Na, K/Na, and Sr/Na than the stream sediments and waters and the sediments are shifted to higher Mg/Na and K/Na and lower Ca/Na than the waters. It is remarkable that the waters have such small variations in major ion ratios relative to the host rocks, indicating that the controls on solute loads of these streams is more a function of relative elemental solubility (Ca > Mg > Na), secondary mineral formation (e.g. Mg- and K-rich clays), incongruent dissolution, and water-rock reactions than end-member rock compositions. Oxidation of massive and disseminated sulfide mineralization accounts for on average 60% of the dissolved sulfate. Calculations indicate that sulfide oxidation (sulfuric acid) weathering accounts for around 20% of the cation flux in the watershed. On average 12% of the Ca and 72% of the Mg are derived from silicate weathering, although cationic silicate denudation rates are only 1.88 tonnes/km2/year compared to 4.16 tonnes/km2/year for trace carbonate dissolution. The total cation denudation rate and CO2 consumption rate are similar to watersheds draining volcanic rocks in the Western Canadian Cordillera.
Geochimica et Cosmochimica Acta, 72, 5962-5983. DOI: 10.1016/j.gca.2008.09.022.
Abstract: We have collected ?500 stream waters and associated bed-load sediments over an ?400 km2 region of Eastern Canada and analyzed these samples for Fe, Mn, and the rare earth elements (REE + Y). In addition to analyzing the stream sediments by total digestion (multi-acid dissolution with metaborate fusion), we also leached the sediments with 0.25 M hydroxylamine hydrochloride (in 0.05 M HCl), to determine the REE + Y associated with amorphous Fe- and Mn-oxyhydroxide phases. We are thus able to partition the REE into "dissolved" (<0.45 ?m), labile (hydroxylamine) and detrital sediment fractions to investigate REE fractionation, and in particular, with respect to the development of Ce and Eu anomalies in oxygenated surface environments. Surface waters are typically LREE depleted ([La/Sm]NASC ranges from 0.16 to 5.84, average = 0.604, n = 410; where the REE are normalized to the North America Shale Composite), have strongly negative Ce anomalies ([Ce/Ce?]NASC ranges from 0.02 to 1.25, average = 0.277, n = 354), and commonly have positive Eu anomalies ([Eu/Eu?]NASC ranges from 0.295 to 1.77, average = 0.764, n = 84). In contrast, the total sediment have flatter REE + Y patterns relative to NASC ([La/Sm]NASC ranges from 0.352 to 1.12, average = 0.778, n = 451) and are slightly middle REE enriched ([Gd/Yb]NASC ranges from 0.55 to 3.75, average = 1.42). Most total sediments have negative Ce and Eu anomalies ([Ce/Ce?]NASC ranges from 0.097 to 2.12, average = 0.799 and [Eu/Eu?]NASC ranges from 0.39 to 1.43, average = 0.802). The partial extraction sediments are commonly less LREE depleted than the total sediments ([La/Sm]NASC ranges from 0.24 to 3.31, average = 0.901, n = 4537), more MREE enriched ([Gd/Yb]NASC ranges from 0.765 to 6.28, average = 1.97) and Ce and Eu anomalies (negative and positive) are more pronounced. The partial extraction recovered, on average ?20% of the Fe in the total sediment, ?80% of the Mn, and 21-29% of the REEs (Ce = 19% and Y = 32%). Comparison between REEs in water, partial extraction and total sediment analyses indicates that REEs + Y in the stream sediments have two primary sources, the host lithologies (i.e., mechanical dispersion) and hydromorphically transported (the labile fraction). Furthermore, Eu appears to be more mobile than the other REE, whereas Ce is preferentially removed from solution and accumulates in the stream sediments in a less labile form than the other REEs + Y. Despite poor statistical correlations between the REEs + Y and Mn in either the total sediment or partial extractions, based on apparent distribution coefficients and the pH of the stream waters, we suggest that either sediment organic matter and/or possibly ?-MnO2/FeOOH are likely the predominant sinks for Ce, and to a lesser extent the other REE, in the stream sediments.
Geochimica et Cosmochimica Acta, 71, 2209-2223. DOI 10.1016/j.gca.2007.02.011.
Abstract: Saline groundwaters were recovered from undisturbed (Restigouche deposit) and active (Brunswick #12 mine) Zn-Pb volcanogenic massive sulfide deposits in the Bathurst Mining Camp (BMC), northern New Brunswick, Canada. These groundwaters, along with fresh to brackish meteoric ground and surface waters from the BMC, have been analyzed to determine their major, trace element and stable isotopic (O, H, C, and B) compositions. Saline groundwaters (total dissolved solids = 22-45 g/L) are characterized by relatively high Na/Ca ratios compared to brines from the Canadian Shield and low Na/Clmolar and ?11B isotopic compositions (?2.5‰-to 11.1-) compared to seawater. Although saline waters from the Canadian Shield commonly have oxygen and hydrogen isotopic compositions that plot to the left of the global meteoric water line, those from the BMC fall close to the water line. Fracture and vein carbonate minerals at the Restigouche deposit have restricted carbon isotopic compositions of around ?5- to ?6-. The carbon isotopic compositions of the saline waters at the Restigouche deposit (+12‰ ?13CDIC) are the result of fractionation of dissolved inorganic carbon by methanogenesis. We suggest that, unlike previous models for shield brines, the composition of saline waters in the BMC is best explained by prolonged water-rock reaction, with no requirement of precursor seawater. We suggest that elevated Br/Cl ratios of saline waters compared to seawater may be explained by differential uptake of Br and Cl during groundwater evolution through water-rock reaction.
Abstract: Stable isotopes (H, O, C) were determined for ground and surface waters collected from two relatively undisturbed massive sulfide deposits (Halfmile Lake and Restigouche) in the Bathurst Mining Camp (BMC), New Brunswick, Canada. Additional waters from active and inactive mines in the BMC were also collected. Oxygen and hydrogen isotopes of surface and shallow groundwaters from both the Halfmile Lake and Restigouche deposits are remarkably uniform (? 13 to ? 14‰ and ? 85 to ? 95‰ for ?18OVSMOW and ?2HVSMOW, respectively). These values are lighter than predicted for northern New Brunswick and, combined with elevated deuterium excess values, suggest that recharge waters are dominated by winter precipitation, recharged during spring melting. Deeper groundwaters from the Restigouche deposit, and from active and inactive mines have heavier ?18OVSMOW ratios (up to ? 10.8‰) than shallow groundwaters suggesting recharge under warmer climate or mixing with Shield-type brines. Some of the co-variation in Cl concentrations and ?18OVSMOW ratios can be explained by mixing between saline and shallow recharge water end-members. Carbon isotopic compositions of dissolved inorganic carbon (DIC) are variable, ranging from ? 15 to ? 5‰ ?13CVPDB for most ground and surface waters. Much of the variation in the carbon isotopes is consistent with closed system groundwater evolution involving soil zone CO2 and fracture zone carbonate minerals (calcite, dolomite and siderite; average = ? 6.5‰ ?13CVPDB). The DIC of saline Restigouche deposit groundwater is isotopically heavy (?+ 12‰ ?13CVPDB), indicating carbon isotopic fractionation from methanogenesis via CO2 reduction, consistent with the lack of dissolved sulfate in these waters and the observation of CH4-degassing during sampling.
Abstract: ABSTRACT We collected ground and surface water samples, as well as samples of host felsic and mafic volcanic lithologies and massive sulphide ore from the Restigouche deposit in the Bathurst Mining Camp, New Brunswick, Canada. These water and rock samples were analysed for their Pb isotope composition in order to investigate the utility of Pb isotope analyses of waters for mineral exploration and environmental tracing. Waters proximal to the near-surface Zn-Pb Restigouche deposit have Pb isotope compositions indistinguishable from galena from a number of volcanogenic massive sulphide deposits in the camp (206Pb/204Pb = 18.18 - 18.34; 207Pb/204Pb = 15.63 - 15.68; 208Pb/204Pb = 38.10 - 38.21). These deposit proximal waters are interpreted to have derived the dissolved (< 0.45 ?m) Pb primarily from oxidation of massive sulphide minerals (galena, sphalerite). Groundwaters more distal from the Restigouche deposit have more radiogenic isotopic compositions, with Pb derived by weathering of U- and Th-rich minerals in the felsic volcanic and volcaniclastic country rocks that host the deposit. There is no correlation between dissolved Pb concentration and isotopic signature owing to the low solubility of Pb in water. The Pb isotopic composition of the dissolved loads of waters is therefore a powerful tool in fingerprinting Pb sources and has important implications for mineral exploration and environmental baseline studies.
Abstract: A detailed hydrochemical study at two undisturbed Ordovician massive sulphide (Zn-Pb) deposits (Restigouche and Halfmile Lake deposits, Bathurst Mining Camp, New Brunswick) was initiated to elucidate the processes controlling the oxidation and dissolution of sulphide minerals, the subsequent dispersion of metals in ground and surface waters, and the precipitation of secondary minerals. Groundwater hydrogeochemical signatures are different for the two deposits. Elements that form sulphide minerals in the deposits correlate positively in surface waters and increase with proximity to the Restigouche deposit, whereas metal contents for Halfmile Lake surface waters are lower, though still typically higher than background levels. Variations in the composition of ground and surface waters draining the two deposits reflect in part differences in the depth and geometry of the massive sulphides and host lithologies. The Halfmile Lake deposit is deeper, more steeply dipping, and overturned compared to the shallower Restigouche deposit. Groundwaters at the Halfmile Lake deposit up to 760 m below surface are low-TDS (<250 mg l?1), Ca-HCO3 to Na-HCO3 waters with oxygen and hydrogen isotopic compositions identical to surface waters. Groundwater REE patterns are flat to LREE-enriched and are similar to host lithologies, unlike the surface waters which are LREE-depleted compared to shale. The Restigouche groundwaters range up to 21,000 mg l?1 TDS (Na-Cl waters) and display heavier oxygen and hydrogen isotopic compositions than local surface waters. Variations in groundwater composition require that the two deposits have different hydrologies which influence the natural oxidation of the massive sulphides and thus the environmental hydrochemical signature.
Abstract: A detailed hydrogeochemical study at the undisturbed Halfmile Lake and Restigouche Zn-Pb deposits, Bathurst Mining Camp, New Brunswick, was initiated to elucidate processes controlling the oxidation of sulphide minerals, factors influencing base-metal dispersion in ground and surface waters, and to improve hydrogeochemical exploration methods. Groundwaters were collected using flow-through bailer and straddle-packer technologies; the latter of which proved to be the most effective under the fracture-flow dominated conditions. Groundwaters from the two deposits are compositionally distinct. At the Halfmile Lake deposit, groundwaters are dominated by low total dissolved solids (TDS < 250 mg 1-1) and Ca-HCO3-type compositions. Groundwaters at the Restigouche deposit vary in composition from shallow Ca-HCO3- and Ca-SO4-type waters to high TDS Na-Cl-type waters. Elevated sulphate and base metal contents (up to 4200 ?g1-1 Zn and 1400 ?g 1-1 Pb) of shallow Ca-SO4-type groundwaters proximal to massive sulphides indicate that the sulphides are undergoing natural oxidation. The degree to which the massive sulphides are oxidized depends on the depth of penetration of dissolved oxygen and flux rates, which are controlled by the permeability of the rocks and local hydrological gradients. Transport of metals away from massive sulphides depends on physical factors that include hydrology, groundwater flow, and the degree of connectivity between groundwater and surface water environments, as well as groundwater pH, metal adsorption and colloid mobility.
Leybourne, M. I., Goodfellow, W. D., Boyle, D. R. and Hall, G. E. M.
Form and distribution of anthropogenic gold mobilized in surface waters and sediments from a gossan tailings pile, Murray Brook massive sulfide deposit, New Brunswick, Canada.
Abstract: Ground and surface waters collected from two undisturbed Zn-Pb massive sulphide deposits (the Halfmile Lake and Restigouche deposits) and active mines in the Bathurst Mining Camp (BMC), NB, Canada were analysed for the rare earth elements (REE). REE contents are highly variable in waters of the BMC, with higher contents typical of waters with higher Fe and lower pH. There are significant differences between ground- and surface waters and between groundwaters from different deposits. The REE contents of surface waters are broadly similar within and between deposit areas, although there are spatial variations reflecting differences in pH and redox conditions. Surface waters are characterised by strong negative Ce anomalies ([Ce/Ce*]NASC as low as 0.08), produced by oxidation of Ce3+ to Ce4+ and preferential removal of Ce4+ from solution upon leaving the shallow groundwater environment. Groundwaters and seeps typically lack significant Ce anomalies reflecting generally more reducing conditions in the subsurface environment and indicating that Ce oxidation is a rapid process in the surface waters. Deeper groundwaters at the Halfmile Lake deposit are characterised by REE patterns that are similar to the host lithologies, whereas most groundwaters at the Restigouche deposit have LREE-depleted patterns compared to NASC. Halfmile Lake deposit groundwaters have generally lower pH values, whereas Restigouche deposit groundwaters show greater heavy REE-complexation by carbonate ions. Shallow waters at the Halfmile Lake and Stratmat Main Zone deposits have unusual patterns which reflect either the adsorption of light REE onto colloids and fracture-zone minerals and/or precipitation of REE-phosphate minerals. Middle REE-enrichment is typical for ground- and surface waters and is highest for neutral pH waters. The labile portion of stream sediments are generally more middle REE-enriched than total sediment and surface waters indicating that the REE are removed from solution by adsorption to Fe- and Mn-oxyhydroxides in the order middle REE?light REE>heavy REE.
Leybourne, M. I., Hamilton, S. M., Mwenifumbo, J. C., Goodfellow, W. D. and Boyle,
Hydrogeochemical and geophysical evidence for in situ oxidation of an undisturbed massive sulfide deposit below the water table and development of self-potential anomalies.
Abstract: Primary massive sulfide gossans (MSG) in the Bathurst Mining Camp (BMC), New Brunswick, Canada, are characterized by relative enrichment of Au, Sb, and As, formation of jarosite group minerals (jarosite, plumbojarosite, and argentojarosite) and little or no fractionation in the rare earth elements (REE), including preservation of large positive Eu anomalies (average [Eu/Eu*]NASC=4.14 in MSG; 6.61 in massive sulfide mineralization; 0.60 in host rocks). The chemical and mineralogical characteristics of MSG (e.g., Halfmile Lake deposit) imply low pH.
Abstract: A deposit-scale study of hydrochemical processes has been conducted at the Halfmile Lake and Restigouche massive (Zn-Pb-Cu-Ag) sulphide deposits, Bathurst Mining Camp (BMC), New Brunswick, Canada. Both the Halfmile Lake and Restigouche deposits are hosted in a deformed sequence of Ordovician (465 Ma) felsic volcanic rocks with similar topography and climate. Groundwater flow is dominated by fracture-flow. The two deposits differ in that the Halfmile Lake deposit is steeply dipping with steep structures whereas the Restigouche deposit is closer to surface with shallower structures. Groundwaters were collected using flow-through bailers and a straddle-packer system that permits recovery of groundwaters from a discrete depth interval. In fracture-controlled rocks, straddle-packer groundwater compositions are more depth representative than bailer groundwaters. Geochemical modelling and stable isotopic compositions indicate that shallow Ca-HCO3 groundwaters are produced by modern meteoric recharge and the major solutes are controlled by dissolution of fracture and vein carbonate and silicate hydrolysis. The Ca-SO4 groundwaters reflect oxidation of the sulphide minerals by modern recharge waters. Deeper brackish to saline groundwaters from the Restigouche, Heath Steele, Brunswick #12, Stratmat Main Zone, and Willett deposits have heavier oxygen and deuterium isotopic compositions than shallow groundwaters indicating older recharge under warmer climates. Interaction between oxygenated recharge waters at the Restigouche and Stratmat Main Zone deposits has resulted in elevated levels of metals (e.g., up to 4000 m g/L Pb and 5300 m g/L Zn) which, based on geochemical modelling and borehole geophysics (self-potential anomalies), are produced by sulphide oxidation. Surface waters collected from the Halfmile Lake and Restigouche deposit primarily represent groundwater discharge based on the compositional and stable isotopic similarity with shallow groundwaters. Geochemical and isotopic modelling indicates that the major solute compositions are controlled primarily by the underlying lithologies and dissolution of carbonate. Although sulphide-associated metals (Zn, Cd, Pb, Cu, Fe) in surface waters at the Halfmile Lake and Restigouche deposits are low compared to streams draining other deposits and mine tailings, anomalously high values (with respect to local background) occur proximal to the Restigouche massive sulphides. The generally neutral pH values in the BMC results in more subtle base metal anomalies in surface waters which indicates that detailed sampling is required for hydrogeochemistry to be an effective exploration tool in the BMC. Groundwaters have higher base metal abundances and display greater contrast between anomalous and background compositions such that groundwaters have potential in better outlining mineralized targets during a drilling program.* (Abstract shortened by UMI.) *The appendices are presented on CD-ROM in Microsoft Excel and Adobe Acrobat format with "xl" and "pdf" suffixes, respectively. The files are readable on Macintosh computers as well as Windows 95 and Windows NT.
Composition of soils and groundwaters at the Pampa del Tamarugal: anatomy of a fossil geochemical anomaly derived from a distant porphyry copper deposit.
Melchior and Bassett eds. ACS Symposium Series 416, p. 292-308.
Abstract: Experiments using hematite particles (70 nm in diameter) in the presence of organics (phthalic acid, fatty acids, polyaspartic acid, fulvic and humic acid) reveal important features of particle coagulation dynamics. A light scattering technique was used to determine quantitatively the initial coagulation rates of hematite particles. Electrokinetic measurements were taken to obtain the sign and magnitude of electrical potential at the oxide/aqueous solution interface. Adsorption experiments were carried out to evaluate affinities of aqueous molecules for the metal oxide surface. Intrinsic equilibrium constants for surface complexes are derived from a Surface Complex Formation/Diffuse Layer Model (SCF/DLM) accounting for interfacial electrostatic charge and potential. Small organic molecules, such as phthalate, show specific chemical reaction with the hematite surface and influence colloidal hematite coagulation kinetics by altering interfacial charge and potential. For fatty acids, hydrophobic interaction, in addition to covalent and electrostatic interaction, offers a plausible explanation for observed systematic changes in hematite stability and electrokinetic data. In the presence of polyelectrolytes, such as polyaspartic acid, fulvic and humic acids, a combination of specific chemical, electrostatic, and hydrophobic energies of carboxyl segments favors adsorption, and these materials have a relatively great impact on particle coagulation and stability.
Hydrogeology and groundwater multi-parametric Hydrogeochemical analysis: an effective methodology to detect buried mineral deposits and establish baseline water quality characteristics.
15th International Geochemical Exploration Symposium, Reno, Nevada, April 29 to May 1, 1991.
Abstract: Gold(III)-chloride and gold(I)-thiosulfate adsorption by goethite was investigated as a function of pH (4 to 8), Cl? concentration (0 to 0.1 M), and ionic strength (0.01 and 0.1 M). Several observations suggest that Au(III)-chloride hydrolysis species with <4 Cl ligands are preferentially adsorbed by goethite and that at low surface coverages these species are adsorbed in an inner-sphere, bidentate fashion. At pH 4.0 and in 0.01 M NaNO3, adsorption isotherms have a shape and maximum adsorption densities (210 ?mol Au/g) similar to those previously observed for phosphate. In addition, excess Cl? appears in solution after adsorption, and an ionic strength increase to 0. l M NaNO3 has little effect on adsorbed amounts below 25% of maximum surface coverage. In 0.01 and 0. l M NaCl, however, adsorption increases as pH increases from 4 to 7, which is opposite to typical behavior for anion adsorption onto oxide surfaces. This "retrograde" adsorption trend is probably due to a shift in Au(III)-chloride species dominance from AuCl4? at pH 4 to preferentially adsorbed hydroxyl-substituted species such as AuCl(OH)3? at higher pH values. Maximum adsorption densities for Au(S2O3)23? at pH 4.0 in 0.01 M NaNO3 are only 35 ?mol Au/g and decrease to 15 /?mol/g in 0.1 M NaNO3. Also, adsorption decreases as pH is increased from 4 to 8. This behavior suggests Au(I)-thiosulfate adsorption occurs primarily via a non-specific or outer-sphere mechanism. Moreover, the contrast in adsorption behavior of these two gold species demonstrates the importance of steric factors to adsorption processes. Gold(III)-chloride species are square planar, and the distance along an edge of this square (3.23 Å) closely matches the distance between A-type hydroxyl groups on the goethite surface (3.04 Å). Thus, these hydroxyl groups form an ideal "template" for bidentate coordination. Conversely, Au(S2O3)23? is a large, linear anion, and consequently it is difficult for this species to coordinate specifically with goethite surface hydroxyl groups.
Abstract: The mid-greenschist facies turbiditic and subaqueous volcaniclastic metasediments at Stawell, Western Victoria, are overprinted by two shear zone systems that host gold mineralization in the Magdala mine. The younger Scotchmans fault zone overprints the older Central lode system and both systems have a reverse sense of movement. There is a systematic reorientation of the Central lode system structures and foliation into parallelism with structures of the Scotchmans fault zone. The boundaries of the Scotchmans fault zone are defined by discrete master faults along which are emplaced gold-bearing laminated quartz veins. The hanging-wall and footwall master faults are linked by an irregular array of subsidiary faults which form duplex structures containing slickenlines, rotated shear zone foliations, and S-C fabrics. Fault breccias, developed on both master and subsidiary faults, are overprinted by a fault gouge implying multiple movements along these faults. In zones where the subsidiary faults intersect and link with the master faults, gold grades increase from an average of 4 to 5 g/t in the laminated quartz veins to greater than or equal to 10 g/t.Microfabrics in the laminated quartz veins indicate vein accretion from either wall or from the center and quartz fibers attesting to vein growth occurring as a series of incremental events rather than being a single event. The gold-bearing fluids overprint earlier laminations but are coeval with later vein accretion associated with sulfides and ankerite. The mineral assemblage of pyrrhotite-pyrite-chalcopyrite-galena is deformed together with the host graphite mica schists and hosts no gold at all. This assemblage is overprinted by the shear zone-forming events. Subsidiary faults exhibit fault jogs in which quartz, pyrite, arsenopyrite, and minor chalcopyrite have precipitated. The assemblage of pyrite-arsenopyrite-chal-copyrite, which is always associated with the gangue minerals of quartz, ankerite, and minor calcite, is present in the laminated quartz veins and hosts the gold mineralization. The gold occurs typically as inclusions or in fractures within pyrite and arsenopyrite. Retrograde minerals are present, associated with the formation of pressure solution structures such as stylo-lites and quartz fibers overprinting the gold-bearing ore assemblages. Tetrahedrite and enargite replace pyrite and arsenopyrite, and some new pyrite has recrystallized from older grains. In the retrograde assemblages no gold is enclosed within individual minerals but it occurs on grain boundaries. This low-temperature mineral overprint is due to diffusive mass transfer that has remobilized the gold that was locked in pyrite and arsenopyrite as inclusions. Extensive dissolution of pyrite and arsenopyrite has resulted in gold redeposition into fractures, cracks, grain boundaries, and stylolites.
EPA Ground Water Issue, EPA/540/S-92/018., Technology Innovation Office, Office of Solid Waste and Emergency Response, US EPA,
Abstract: Metals added to soil will normally be retained at the soil surface. Movement of metals into other environmental compartments, i.e. groundwater, surface water, or the atmosphere, should be minimal as long as the retention capacity of the soil is not exceeded. The extent of movement of a metal in the soil system is intimately related to the solution and surface chemistry of the soil and to the specific properties of the metal and associated waste matrix. The retention mechanisms for metals added to soil include absorption of the metal by the soil solid surfaces and precipitation. In addition to soil properties, consideration must be given to the type of metal and its concentration and to the presence of competing ions, complexing ligands, and the pH and redox potential of the soil-waste matrix. Because of the wide range of soil characteristics and various forms by which metals can be added to soil, evaluating the extent of metal retention by a soil is site/soil/waste specific. Laboratory methods for evaluating the behavior of metals in soils are available in the literature. Thermodynamic equilibrium computer models are also available to assist with the evaluation. The advantages and disadvantages of some of the available procedures and models have been presented in the document.
Abstract: A hydrogeochemical survey utilizing waters from streams and springs was conducted in the area of two known porphyry copper deposits in the tropical-marine climate of westcentral Puerto Rico. The most important pathfinder for regional hydrogeochemical surveys is sulfate which reflects the associated pyrite mineralization. Because of increased mobility due to intense chemical weathering and the low pH environment, dissolved copper can also be used as a pathfinder for regional surveys and has the advantage of distinguishing barren pyrite from pyrite associated with copper mineralization. For follow-up surveys, the most important pathfinders are copper, sulfate, pH, zinc, and fluoride. High concentrations of dissolved copper and moderate concentrations of sulfate is a diagnostic indication of nearby sources of copper minerals. An understanding of the geochemical processes taking place in the streambeds and the weathering environment, such as the precipitation of secondary copper minerals, contributes to the interpretation of the geochemical data and the selection of the most favorable areas for further exploration.
Abstract: A forest-bog landscape is developed in an area of moderate to low topography in northeastern China. Bogs are widespread along U- and V-shaped valleys (200–2000 m wide) and in depressions. Due to the cold climate, it was initially thought that chemical weathering would be slight in the area. However, a study of the geochemistry of surface water showed that, although most elements occur in relatively low concentrations compared to average contents in world river water, a number of mobile elements are dispersed over long distances. Marked Cu, Zn, Fe, Mn, and SO2?4 anomalies, and relatively weak Ni, Co, Be, Pb and F anomalies form in stream water in the vicinity of known mineralization. Concentrations of Cu, Pb, Zn, Fe, and Mn in suspensates show no marked variations between background and anomalous streams whereas Ag exhibits a marked increase in suspensates near the mineralization. The pH of stream water near the mineralization is considerably lower than the 5 to 6.5 values recorded for background water. It can be concluded that water plays an important role in transporting elements chemically and stream water is a useful medium to sample in follow-up geochemical surveys for base and precious metals (Ag) in this landscape.
Abstract: Porphyry-related metal deposits are large-tonnage, generally low-grade, hydrothermal deposits related to igneous intrusions emplaced at high crustal levels. Mineralization may be confined to pluton-hosted disseminations, stockworks, vein sets, and breccias and (or) occur in skarns, replacements, veins, and disseminated deposits peripheral to the inferred source pluton. Coeval epithermal precious metal-dominated deposits may occur above, or be telescoped onto, porphyry systems. This spectrum of deposit types includes many of the world's largest accumulations of Cu, Mo, Au, Ag, Sn, and W. As such the deposits represent critical economic resources and important exploration targets (Gilmour et al., 1995; Kirkham and Sinclair, 1996; Singer, 1995). To prospect efficiently for undiscovered mineral deposits, or to speculate about future metal supply, it is useful to define the size, distribution, and geologic characteristics of known deposits. It is to that end that we have compiled this database, the release of which is part of a larger effort to characterize the world's largest and most important porphyry-related deposits. We hope that this compilation can be of aid to researchers, explorationists, and students alike. We also recognize that any compilation effort is, by its very nature, incomplete, as well as out-of-date as soon as it is released. Thus, we welcome any corrections or updates to the data presented here and request that you direct any communications to Felix Mutschler at 509-359-2854 or Steve Ludington at 650-329-5371. E-mail addresses are linked below.
Water Resources Research, V. 26, No. 8, p. 1749-1758.
Abstract: An interpretation is offered for the observation that dispersivities increase with scale. Apparent longitudinal dispersivity data from a variety of hydrogeologic settings are assumed to represent a continuous hierarchy of log hydraulic conductivity fields with mutually uncorrelated increments, each field having its own exponential autocovariance, associated integral scale, and variance that increases as a power of scale. Such a hierarchy is shown theoretically to form a self-similar random field with homogeneous increments. Regardless of whether or not the underlying assumption is valid, one can justify interpreting the apparent dispersivities in a manner consistent with a recent quasi-linear theory of non-Fickian and Fickian dispersion in homogeneous media which supports the notion of a self-similar hierarchy a posteriori. The hierarchy is revealed to possess a semivariogram ?(s;) ? cs½, where c is a constant, and a fractal dimension D ? E + 0.75, where E is the topological dimension of interest. This can be viewed as a universal scaling rule about which large deviations occur due to local influences including the existence of discrete natural scales at which log hydraulic conductivity is statistically homogeneous. As such homogeneity is at best a local phenomenon occurring intermittently over narrow bands of the scale spectrum, one must question the utility of associating medium properties with representative elementary volumes and relying on Fickian models of dispersion over more than relatively narrow scale intervals. Porous and fractured media appear to follow the same idealized scaling rule for both flow and transport, raising a question about the validity of many distinctions commonly drawn between such media. Finally, the data suggest that conditioning transport models through calibration against hydraulic measurements has the effect of filtering out large-scale modes from the hierarchy.
In Geochemical Exploration 1978, Proceedings of the Seventh Int’l. Geochemical Exploration Symposium, Golden, CO.
Abstract: Paper presented at 7th International Geochemical Exploration Symposium held in 1979. Report of study which involved mapping of compositional phases of Tombstone batholith in Yukon, examination of geological setting and probable style of mineralization, and evaluation of use of stream sediments and waters in exploration for porphyry uranium within the batholith and rocks of similar composition elsewhere in the region.
Nevada Bureau of Mines and Geology, Bulletin 87, 35 p.
Abstract: Describes playas, playa deposits, and commodities in Nevada playas: sodium chloride (halite), borates (borax, ulexite, colemanite), sodium carbonate (trona, gaylussite), sodium sulfate (mirabilite, thenardite), potassium, and lithium; references and index. Supplements material in Bulletin 65; additional information on industrial minerals available on Map 46.
Abstract: A detailed chemical study of groundwater was carried out to elucidate the processes controlling the oxidation and dissolution of sulphide minerals at two massive sulphide deposits in the Iberian Pyrite Belt (IPB), i.e. the mined La Zarza deposit and the unmined Masa Valverde deposit. It was found that major-element compositions varied according to the hydrological regime, La Zarza being in a relatively high area with groundwater recharge (and disturbance due to the human factor) and Masa Valverde being in a relatively low area with groundwater discharge. The variations mainly concern pH, Eh, SO4 and Na concentrations. Metal concentrations were determined (a) by ICP-MS after filtration, and (b) in some cases by voltammetric measurement of Cu, Pb, Zn, Cd and Mn using the Voltammetric In situ Profiling (VIP) System, which allows detection of only the mobile fractions of trace elements (i.e., free metal ions and small labile complexes a few nanometers in size). If one compares the results obtained by each of the two methods, it would appear that the groundwater shows significant enhancement of metal solubility through complexing with organic matter and/or adsorption onto colloids and/or small particles. In areas of sulphide oxidation, however, this solubility enhancement decreases according to Cu>Zn>Cd>Pb. Under very low redox conditions, the attained metal concentrations can be several orders of magnitude (up to 108-109 for Cu and 102-103 for Pb) larger than those expected from equilibrium with respect to sulphide minerals as calculated with the EQ3NR geochemical code; Zn concentrations, however, are close to equilibrium with respect to sphalerite. The implication of these results is discussed with respect both to mineral exploration and to environmental issues.
Geostandards and Geoanalytical Research, 32, 149-166.
Abstract: The present study evaluates several critical issues related to precision and accuracy of Cu and Zn isotopic measurements with application to estuarine particulate materials. Calibration of reference materials (such as the IRMM 3702 Zn) against the JMC Zn and NIST Cu reference materials were performed in wet and/or dry plasma modes (Aridus I and DSN-100) on a Nu Plasma MC-ICP-MS. Different mass bias correction methods were compared. More than 100 analyses of certified reference materials suggested that the sample-calibrator bracketing correction and the empirical external normalisation methods provide the most reliable corrections, with long term external precisions of 0.06 and 0.07- (2SD), respectively. Investigation of the effect of variable analyte to spike concentration ratios on Zn and Cu isotopic determinations indicated that the accuracy of Cu measurements in dry plasma is very sensitive to the relative Cu and Zn concentrations, with deviations of ?65Cu from ?0.4‰-(Cu/Zn = 4) to +0.4- (Cu/Zn = 0.2). A quantitative assessment (with instrumental mass bias corrections) of spectral and non-spectral interferences (Ti, Cr, Co, Fe, Ca, Mg, Na) was performed. Titanium and Cr were the most severe interfering constituents, contributing to inaccuracies of ?5.1- and +0.60- on ?68/64Zn, respectively (for 500 ?g l?1 Cu and Zn standard solutions spiked with 1000 ?g l?1 of Ti or Cr). Preliminary isotopic results were obtained on contrasting sediment matrices from the Scheldt estuary. Significant isotopic fractionation of zinc (from 0.21- to 1.13- for ?66Zn) and copper (from ?0.38‰--to 0.23- for ?65Cu), suggest a control by physical mixing of continental and marine water masses, characterized by distinct Cu and Zn isotopic signatures. These results provide a stepping-stone to further evaluate the use of Cu and Zn isotopes as biogeochemical tracers in estuarine environments.
Abstract: The Myra Falls Price deposit is a zinc-rich volcanogenic massive-sulphide ore-body located in a mountainous region of central Vancouver Island, British Columbia. High rainfall and steep hydraulic gradients limit the water–mineral contact, which results in a low solute load in the oxygenated groundwater. Despite this, significant element contrasts exist that permit the development of groundwater geochemical methods for exploration. Zinc displays the strongest and most reliable anomaly contrasts in groundwaters associated with mineralization related to the Price deposit. Statistical procedures are used to differentiate two overlapping subpopulations of Zn concentrations, which are partitioned into two constituent populations. A threshold value of 20??g/l was established, which includes an uncertainty that allows up to 10% of the background population being defined as anomalous. Zn anomalies can be further enhanced with a suite of pathfinder elements associated with primary mineralization and hydrothermal alteration, including Cu, Pb, Cd, Mn, As, Sb, Ba and U. In addition to massive-sulphide mineralization, sulphides also exist as clasts within a breccia unit designated as the ore-clast breccia (OCB). Effective discrimination is possible between anomalies in groundwaters associated with massive-sulphide mineralization and groundwaters associated with OCB through the use of elements associated with primary mineralization and hydrothermal alteration such as K, Rb, B, Ba, Cd, Sb, U and barite saturation, which are elevated in groundwaters associated with massive-sulphide mineralization but not the OCB. Groundwater geochemical exploration methods offer a supplemental tool to exploration of Zn-rich massive-sulphide deposits where existing infrastructure, exploration drifts and drill holes are present.
Abstract: This paper considers the interpretation of uranium (U) ore-mineral equilibrium calculations in groundwater to help understand ore genesis and assist exploration. Groundwater samples collected on two recent field sampling trips in the Frome Embayment region of South Australia have been analysed for major and selected trace elements. These data together with previous published data have been used to construct geochemical models of the equilibrium state of the groundwaters. Species’ activities and mineral saturation states have been estimated. Calculated species’ activities are generally in the range reported in the previous modelling by Giblin involving groundwaters from similar local sources. Our models indicate that amorphous UO2, rather than the ore minerals coffinite and uraninite, is the solidU mineral phase that is the likely control on groundwater U concentration. The UO2(am) saturation index did not show a systematic variation with ore grade or proximity to mineralization. Its use for exploration at smaller scales, where the groundwater composition is similar between sample sites and U minerals are present at various concentrations, is doubtful. Inherent limitations on the information provided by mineral saturation indices restrict their exploration application,particularly in high salinity palaeochannel groundwater environments, such as those common in Australia.
In Filipek, L.H. and Plumlee, G.S. (ed) The Environmental Geochemistry of Mineral D, Vol. Reviews in Economic Geology 6B, pp. 373-432. Society of Economic Geologists.
Abstract: Sulfide-bearing mineral deposits formed in reduced conditions out of contact with an oxygenated atmosphere. When sulfides in the deposits are exposed by natural erosion or by mining to atmospheric oxygen and water, weathering of the sulfides can produce natural or mining-related acid-rock drainage. The prediction of water quality that results from mining and mineral processing activities has therefore become a high priority in the permitting of mining activities worldwide, in order to prevent the formation of or mitigate the environmental effects of deleterious drainage waters. In addition, estimating the compositions of natural waters that drained mineral deposits prior to mining is crucial to establish appropriate baseline environmental standards at mine sites. There are a variety of techniques currently in use to predict the acidity or metal content of mine-drainage waters, most common of which are static and kinetic testing procedures. In static procedures such as acid-base accounting (White et al., 1997, 1999), the contents of acid-generating sulfide minerals from ores and wastes from a proposed mine are measured and balanced against the measured contents of acid-consuming minerals such as carbonates; based on this balance, the materials are determined to be acid generating or non-acid-generating. In kinetic tests such as column or humidity-cell tests (ASTM, 1996), samples of ores and wastes are allowed to react over a period of time under laboratory conditions with oxidized waters or moist air, and the pH and metal contents of the resulting leachates are then measured. Although both static and kinetic methods are widely used to help predict the compositions of mine waters, they have several potential limitations. Most important of these are (1) whether the samples used in the tests adequately represent the range of mineralogic characteristics commonly present in complex mineral deposits, (2) whether the time scale and laboratory conditions of kinetic tests adequately reproduce the time scales and physical, geochemical, and biological conditions actually present in the mine, mine dump, or tailings impoundment environment, and (3) whether kinetic test leachate compositions accurately reproduce actual drainage quality. Another approach to mine-drainage prediction that can be used to supplement the static and kinetic engineering tests is one in which the compositions of existing mine waters draining geologically similar deposit types in similar climates are measured empirically and then interpreted in a geologic and geochemical context. By evaluating the compositions of waters draining geologically comparable deposits in comparable climates, it is possible to place constraints on the potential ranges in composition of Chapter 19 373 waters that might result from the development of a particular ore deposit. Such empirical examinations of existing drainage waters help overcome the issues of sample representation, adequacy of time scales, and accuracy of reproduction of natural conditions by laboratory experiments—the waters already are draining larger, more representative volumes of rock, and they are generated under field conditions and time scales. Past studies that demonstrated the importance of geologic controls on mine-drainage compositions include those of Wildeman et al. (1974) in the Central City mining district, Colorado, and those of Wai et al. (1980) in the Bunker Hill mine, Coeur d’Alene district, Idaho. Results of both these studies showed that drainage compositions vary predictably within a mine (Wai et al., 1980) and across a district (Wildeman et al., 1974) as a function of deposit geology. However, in the time since these studies were carried out and prior to the early 1990s, a systematic examination of minedrainage compositions across a spectrum of mineral deposit types, and within different ore types of given deposit types was generally lacking. Since the early 1990s, a number of studies have begun to examine both natural- and mine-drainage water compositions in the context of mineral-deposit geology (Ficklin et al., 1992; Plumlee et al., 1992, 1993a, b; Runnells et al., 1992; Smith et al., 1994; Price et al., 1995; studies in du Bray, 1995; Goldfarb et al., 1996, 1997; Eppinger et al., 1997; Kelley and Taylor, 1997). This paper summarizes results to date of an ongoing empirical study examining the composition of mine waters and natural waters draining a broad spectrum of mineral deposit types, mineralogic zones within deposit types, and geologically similar mineral deposit types in different climates (Ficklin et al., 1992; Plumlee et al., 1992, 1993a; Smith et al., 1994). We include in this study data that we have collected and data compiled from the literature. The results to date of this empirical study illustrate the many fundamental controls that mineral-deposit geology exerts, in combination with geochemical processes and biogeochemical processes, on the compositions of mine-drainage waters and natural waters draining unmined mineral deposits. Other important controls, such as climate, mining method used, and mineral processing method used, modify the effects mandated by deposit geology, geochemical, and biogeochemical processes. Our results show that, by interpreting empirical drainage data in a geologic context, it is possible to constrain the potential ranges in pH and ranges in metal concentrations of mine- and natural-drainage waters that may develop within different mineralogic zones, ore types, or alteration types in a given mineral deposit. Our results are not sufficiently precise that they can be used to quantitatively predictthe exact compositions of water that will develop in a particular mine, mine dump, or tailings impoundment at a particular mineral deposit. Instead, the predictive capabilities provided by such an empirical approach should be only part of a comprehensive riskbased approach to environmentally responsible mineral-resource development employed by industry and regulators alike. For general references on the geology of mineral deposits, the reader is referred to economic geology textbooks such as Guilbert and Park (1986), and to other compilations such as Cox and Singer (1986), Kirkham et al. (1993), du Bray (1995), and references contained therein. For a summary of the environmental geology characteristics of mineral deposits, see Plumlee (1999) and references therein.
Abstract: In 1956, the All-Union Scientific Research Institute for Prospecting Methods and Equipment (VITR) and the Chita Geological Bureau conducted joint studies to develop a prospecting method for polymetallic ore occurrences using muds and waters of the regional drainage system in eastern Transbaikal. The region is dry with distinctly continental climate; precipitation, averaging 330 millimeters per year, is proportionately heavier during the summer season. The Nerchinsky Zavod district, selected for study, is hilly with absolute elevations of 600-850 meters, cut into ridges by northeast-southwest trending ravines; and, characterized by a mature drainage system. Permafrost islands are widespread and vegetation is transitional between steppe and taiga types. Lower Paleozoic, Silurian, and Lower and Middle Jurassic sedimentary rocks occur to the west along with granite bodies and other intrusives. To the east, Lower Cretaceous sediments are extensive; Tertiary and Quaternary effusive appear and Proterozoic and lower Paleozoic metamorphic rocks are exposed over an extensive area along the Serebyanka River. Most ore occurrences are to the west in upper and lower Paleozoic, principally carbonate, rocks. Galena, sphalerite and pyrites occur in carbonates and some quartz, as lenses, veins, and irregular bodies. Limonite is predominant among oxidized ores, which include manganese oxides. Pb, Zn, Ag, As, and Sn, content is high; Sb and Cd are present. The following conclusions have been developed frompreliminary work: Dispersion halos in stream-bed muds reflected occurrence and composition of polymetallic ore deposits on the sides of ravines. Small and medium-sized deposits were found to have halo heads as long as 4.5 kilometers andtrains as long as 2. 5 kilometers; according to the degree of sensitivity obtained by analysis. It was concluded that simultaneous determination for several elements is desirable, as well as sampling in two stages to reduce work volume: i. e., general sampling at 200-meter intervalsito establish presence of ore bearing valleys; and 50-100-meter interval sampling to discover halos for individual deposits. Polymetallic deposits are identifiable by high ?M (sum of metals present), or, essentially, the zinc content because of its widespread dissemination in natural waters in underground and surface waters. No false ?M anomalies, not related to ore deposits, were encountered. Sampling of alluvium and talus waters and of country rock waters yielded identical results. It was established that hydrochemical prospecting should be during rainy periods when many springs appear in alluvium and talus; however, frequent and brief precipitation may complicate sampling results. Possible contamination of samples must be avoided, especially in sampling surface waters. Thus, hydrochemical prospecting for polymetallic ore deposits by sampling stream-bed muds proved to be particularly adapted to the regional conditions of eastern Transbaikal. A comparatively small number of samples is needed to find ore-bearing districts; probably one-tenth that required for areal metallometric survey of eluvium and talus on the usual 1:50,000 scale. In addition, muds of underground and surficial waters may reflect blind deposits not identifiable by metallometric surveys of talus. Heavy or extensive equipment, power source, or fuel haulage are not required; thus, analyses can be run by most field parties. Analysis methods have been deVeloped for only a small number of elements, it is planned to develop these methods for use under a wider range of environments, and for use of indicators for a large variety of metal complexes.
Abstract: The Upper Miocene and Pliocene evaporite deposits of the Atacama Desert of northern Chile (Hilaricos and Soledad Formations) are among the few non-marine evaporites in which aridity not only formed the deposits, but has also preserved them almost unaltered under near-surface conditions. These deposits are largely composed of displacive Ca sulphate and halite together with minor amounts of glauberite, thenardite and polyhalite. However, at the base and top of these deposits, there are also beds of gypsum crystal pseudomorphs that originally formed as free-growth forms within shallow brine bodies, rather than as displacive sediments. The halite is present as interstitial cement, displacive cubes and shallow-water, bottom-growth chevron crusts. Most of the calcium sulphate is presently anhydrite, pseudomorphous after gypsum, that was the primary depositional sulphate mineral. The secondary anhydrite formed under early diagenetic conditions after slight burial (some metres) resulting from the effect of strongly evolved pore brines. The anhydrite has been preserved without rehydration during late diagenetic and exhumation stages on account of the arid environment of the Atacama Desert. Both the Hilaricos and the Soledad Formations contain geochemical markers indicating that these Neogene evaporites had a largely non-marine origin. Bromine content in the halite is very low (few p.p.m.), indicating neither a sedimentological relation with sea water nor the likelihood of direct recycling of prior marine halites. Moreover, the ?34S of sulphates (+4·5‰-to +9-) also reflects a non-marine origin, with a strong volcanic influence, although some recycling of Mesozoic marine sulphates cannot be ruled out. ?34S of dissolved sulphate from hot springs and streams in the area commonly displays positive values (+2‰-to +10-). Leaching of oxidized sulphur and chlorine compounds from volcanoes and epithermal ore bodies, very common in the associated drainage areas, have been the main contribution to the accumulation of evaporites. The sedimentary and diagenetic evolution of the Hilaricos and Soledad evaporites (based on lithofacies analysis) provides information about the palaeohydrological conditions in the Central Depression of northern Chile during the Neogene. In addition, the diagenesis and exhumation history of these evaporites confirms the persistence of strongly arid conditions from Late Miocene until the present. A final phase of tectonism took place permitting the internal drainage to change and open to the sea, resulting in dissolution and removal of a significant portion of these deposits. Despite the extensive dissolution, the remaining evaporites have undergone little late exhumational hydration.
Abstract: The presence of large amounts of atacamite in oxide zones from ore deposits in the Atacama Desert of northern Chile requires saline solutions for its formation and hyperarid climate conditions for its preservation. We investigated the nature and origin of atacamite-forming solutions by means of coupling groundwater geochemical analyses with fluid inclusion data, high-resolution mineralogical observations, and chlorine-36 (36Cl) data in atacamite from the Mantos Blancos and Spence Cu deposits. In both deposits, the salinities of fluid inclusions in atacamite are comparable to those measured in saline groundwaters sampled from drill holes. The average salinity of fluid inclusions in atacamite for the Mantos Blancos and Spence deposits (~7-9 and 2-3 wt.% NaCleq, respectively) are strongly correlated to the salinities at which gypsum supersaturates from groundwaters in both deposits (total dissolved solids ~5–9 and 1-3 wt.% NaCleq, respectively). This correlation is confirmed by transmission electron microscopy observations of atacamite-bearing samples, revealing an intimate association between atacamite and gypsum that can be traced down to the nanometer scale. 36Cl data in atacamite provide new lines of evidence concerning the origin and age of the saline waters that formed atacamite in various stratabound and porphyry Cu deposits from the Atacama Desert. All atacamite samples show very low 36Cl-to-Cl ratios (11?×?10?15 to 28?×?10?15 at at?1), comparable to previously reported 36Cl-to-Cl ratios of deep formation waters and old groundwaters. In addition, 36Cl-to-Cl ratios in atacamite correlate with U and Th concentration in the host rocks but are independent from distance to the ocean. This trend supports an interpretation of the low 36Cl-to-Cl ratios in atacamite as representing subsurface production of fissiogenic 36Cl in secular equilibrium with the solutions involved in atacamite formation. Therefore, 36Cl in atacamite strongly suggest that the chlorine in saline waters related to atacamite formation is old (>1.5 Ma) but that atacamite formation occurred more recently (<1.5 Ma) than suggested in previous interpretations. Our data provide new constraints on the origin of atacamite in Cu deposits from the Atacama Desert and support the recent notion that the formation of atacamite in hyperarid climates such as the Atacama Desert is an ongoing process that has occurred intermittently since the onset of hyperaridity.
Abstract: Supergene enrichment of Cu deposits in the Atacama Desert has played a critical role in making this the prime Cu-producing province of the world. Previously, this has been believed to have occurred exclusively over a long period from the middle Eocene to the late Miocene, which ended when climatic conditions changed from arid to hyperarid. Here, we report U-series disequilibrium ages in atacamite-bearing supergene assemblages that provide a new conceptualization on both the supergene enrichment process and the onset of extreme hyperaridity in the Atacama Desert. 230Th-234U ages of gypsum intergrown with atacamite in supergene veins from Cu deposits cluster at ~240 ka (Chuquicamata), 130 ka (Mantos Blancos, Spence), and 80 ka (Mantos de la Luna, Michilla). When coupled with previous data, these results indicate that supergene enrichment of Cu deposits did not cease after the onset of hyperaridity. We propose that supergene enrichment in the Atacama region developed in two main stages. The main phase, caused by downward circulation of meteoric waters in a semi-arid setting, was active from 45 until ~9 Ma, with a last pulse ca. 5 Ma in the southern Atacama Desert. During this phase, atacamite-bearing supergene assemblages were not preserved because atacamite requires saline water for its formation and rapidly dissolves when contacted by meteoric water. This was followed by a second stage starting at ~2-1.5 Ma and continuing until at least the late Pleistocene, when deep formation waters derived from the basement passed up through and modified the pre-existing supergene Cu oxide minerals. Atacamite has then been preserved in the prevailing hyperarid climate.
The Science of the Total Environment, 234, 155-173.
Abstract: Analyses of unfiltered and filtered (<0.45 ?m and <0.10 ?m) groundwater samples from 15 selected wells in crystalline bedrock aquifers of the Oslo area, Norway, have been studied for 62 chemical elements. While concentrations of almost all elements vary over several orders of magnitude between the individual wells, the discrepancy between filtered and unfiltered samples from the same well are rather small, not exceeding one order of magnitude. Many elements show no influence of filtration at all, while one element (Sn) suggests that filtration may actually introduce contamination to the samples. Correlation between unfiltered and filtered samples is high for most elements. The study shows that: (1) even unfiltered samples will satisfactorily reflect general water chemistry as long as drinking water (i.e. by definition rather ‘clean’ water, with low particulates) is collected; (2) filtered samples do not necessarily reflect ‘true’ solution chemistry (an elusive concept); and (3) the differences between samples filtered at <0.45 ?m and <0.10 ?m are so minimal for most elements, that the additional effort invested in ultra-filtration may not be justified for bedrock groundwater samples.
The Science of the Total Environment, 239, 111-130.
Abstract: Groundwater samples from 15 boreholes in crystalline bedrock aquifers in South Norway (Oslo area) have been collected in parallel in five different clear plastic bottle types (high density polyethene [HDPE], polypropene [PP, two manufacturers], fluorinated ethene propene copolymer [FEP] and perfluoroalkoxy polymer [PFA]. In the cases of polyethene and polypropene, parallel samples have been collected in factory-new (unwashed) bottles and acid-washed factory-new bottles. Samples have been analysed by ICP-MS techniques for a wide range of inorganic elements down to the ppt (ng/l) range. It was found that acid-washing of factory-new flasks had no clear systematic beneficial effect on analytical result. On the contrary, for the PP-bottles concentrations of Pb and Sn were clearly elevated in the acid-washed bottles. Likewise, for the vast majority of elements, bottle type was of no importance for analytical result. For six elements (Al, Cr, Hf, Hg, Pb and Sn) some systematic differences for one or more bottle types could be tentatively discerned, but in no case was the discrepancy of major cause for concern. The most pronounced effect was for Cr, with clearly elevated concentrations returned from the samples collected in HDPE bottles, regardless of acid-washing or not. For the above six elements, FEP or PFA bottles seemed to be marginally preferable to PP and HDPE. In general, cheap HDPE, factory new, unwashed flasks are suitable for sampling waters for ICP-MS ultra-trace analysis of the elements tested.
Abstract: The role of organic ligands in metal complexing in natural waters has received little attention because of uncertainties regarding both the abundance and nature of dissolved organic carbon compounds. Recent data show that the bulk of dissolved organic matter in natural waters consists of highly oxidized and chemically and biologically stable polymeric compounds closely resembling soil humic substances. Average molar concentrations of these aquatic humics in major U.S. rivers range from 5 × 10?6to 3 × 10?5 moles 1?1. Fractional elution of soil organic matter by meteoric waters may be considered to be the main process contributing to the presence of humic matter in rivers. The aquatic humic polymers participate in complex formation through ionizable functional groups with a range of differential acidities. The stabilities of metal-humic complexes in natural waters are higher than those of the corresponding inorganic metal complexes. Quantitative evaluation of the metal-organic interactions can be approached by applying variable equilibrium functions which take into account the differential physico-chemical characteristics of the active complexing sites on the polymer molecule. Assuming an average humic concentration of 10 mg 1?1, complexation of trace metals can be significant even in the presence of excess concentrations of major cations.
In Symposium on hydrogeochemical and stream sediment reconnaissance for Uranium in, p. 301-303.
Abstract: Field studies conducted in areas of known uranium deposits are described. In Weld County, Colorado, 18 samples were collected in an 80 square kilometer area around a roll-type uranium deposit approximately 70 meters deep. Stock supply wells and domestic wells, ranging from 5 to 25 meters deep, were sampled and analyzed for helium. The wells located down the ground water gradient with respect to the ore body had helium concentrations 30 to 50 times greater than those values expected from atmospheric equilibrium. The shallow wells had less helium than the deeper domestic wells. At the Schwartzwalder mine in Jefferson County, Colorado, mine water, pond water, springs and streams were sampled and analyzed for helium. The mine water and springs had helium concentrations 5 to 15 times greater than atmospheric equilibrium, but the ponds and streams, into which the mine water drained, showed no excess helium. The equilibrium values of helium found in the ponds and streams were expected because even minor turbulence effectively removes excess helium from water. Therefore, streams and standing bodies of water are not good candidates for helium analysis. Mine water was also sampled from several uranium mines at the Ambrosia Lake deposits near Grants, New Mexico. The samples were taken at the surface discharge pipes and the helium values were 2 to 7 times that of atmospheric equilibrated waters. Because of both the short residence time of the water with the ore and the great amount of turbulence from pumping, the helium values were relatively low. The large geographic area in the vicinity of a uranium deposit in which subsurface water samples show helium anomalies indicates that helium analyses can be used as a reconnaissance exploration tool.
Abstracts Volume, 9th International Geochemical Exploration Symposium, Saskatoon, C, May 12-14, 1982, 14 p.
Abstract: About 500 well and spring waters were collected on an approximately 1-km spacing in an area centered on six small U and Cu-U occurrences near Monticello, N.Y., as an orientation survey in the NURE program. Rocks of the area belong to the Devonian Catskill Group and are predominantly red sandstones and shales of fluvial origin. The sediments dip 0-5° in the main part of the area, but steepen to 45° in the east. The ground waters were analyzed for 46 elements plus several other water properties. An R-mode factor analysis extracted 10 factors. The strongest factor, termed "Dissolved solids", has heavy loadings on most major elements, plus U, B, Li, Sr, and Zn. This factor is attributed to varying degrees of interaction between original rainwater and rocks. Recognition of anomalies for elements loaded on this factor is aided by evaluation of ratios or plots against total dissolved solids or conductivity. Three weaker factors apparently represent admixtures with two types of deep brine and with waters of enhanced Fe-Mn resulting from reducing conditions. Other factors include an assemblage of insoluble trace metals and a Zn-Cu-P factor, both possibly related to contamination and/or analytical problems, a rare earth group, and an Se-As-Ag factor. The waters are clearly complex mixtures of effects. The geographic distribution of high U values shows some correlation with the distribution of U occurrences, but many equally high values occur outside the known mineralized area. When the data are projected to a vertical section normal to the strike, high U values define two gently dipping aquifers. The upper anomalous aquifer contains the known occurrences but extends downdip. Samples within this aquifer show patterns in U, dissolved O2, and conductivity, apparently related to influx of fresh water from updip, along major rivers, and along possible fractured zones. High He values are also most numerous near the occurrences and define the deeper U-rich aquifer. The interpretation of the data is greatly clarified by separation of individual aquifers.
Abstract: A hydrogeochemical orientation survey in a basalt-covered area in northeastern China was carried out in order to investigate concealed metallic mineralization under thick basalt cover by hydrogeo-chemical procedures. In this presentation, the main results of the investigation around a Cu-Mo mineralized zone in a basalt-covered area are described. Discussions focus on: 1, the distribution of the principal indicator elements in the stream and spring waters; 2. the migration ability of the main indicator elements in the surficial environment; 3. geochemical characteristics of waters in different geological units of the area; 4. the stability and persistence of the hydrogeochemical patterns of the known deposits and 5. the influence of basalt components on the ore-related hydrogeochemical anomalies and the procedures to eliminate this influence. It has been noted that Mo and SO4 can be used directly as indicators of Cu-Mo mineralization in the basalt-covered area. In the case of other common indicator elements of sulfide deposits such as Cu and Zi, it is difficult or impossible to discriminate ore-related hydrogeochemical anomalies from background contents related to basalt. However, Cu/Ni and Zn/Ni ratios have been successfully used to eliminate the basalt influence and enhance the ore-related hydrogeochemical anomalies. The stability of the ore-related hydrogeochemical anomalies during a three-week sampling period and the persistence of the hydrogeochemical patterns in different years indicates the effectiveness of water sampling during the dry season in the area. On this basis, it is concluded hydrogeochemical exploration can be used as a major regional exploration method for exploring for concealed metallic mineralization in the basalt-covered areas in northeastern China.
Abstract: Groundwaters in contact with hidden ore deposits may acquire chemical compositions that offer a guide for exploration, if the chemistry of the waters can be properly interpreted. Hydrogeochemical computer models allow significant progress to be made in the interpretation of the chemistry of all types of natural waters. The computer program, WATEQFC, an expansion and restructuring of WATEQF, is directed toward geochemical exploration for uranium and base metals. The expanded program can now solve the simultaneous equilibria involved in the aqueous geochemistry of 47 chemical elements, represented by approximately 540 minerals and solid compounds and 650 aqueous species. Calibration of the model with groundwaters from known deposits of uranium ore suggests that hidden ore bodies may be revealed by the state of saturation of the waters with respect to a suite of potential ore and gangue minerals. The saturation index (SI) is a reliable predictor of the presence of uranium ore from known deposits in Texas, Wyoming, and Czechoslovakia. The use of groundwater for regional reconnaissance strongly suggests that uranium mineralization is present in the subsurface near Colorado City, Colorado, whereas a similar modeling of groundwaters from a large area of Triassic sandstones in England virtually eliminates that area from consideration as a host for hidden uranium ore.
Abstract: Groundwaters from diamondiferous kimberlite pipes in the Kirkland Lake and Lake Timiskaming regions display unusual geochemical characteristics and signatures compared with groundwaters from the surrounding host rock. Reaction modelling was used to better constrain water/rock ratios, alteration mineralogy and groundwater geochemistry. A soil-zone Ca-HCO3? water from glacial till was reacted, using a reaction-modelling program, with three different suites of minerals: a kimberlite suite, a felsic intrusive suite and a mafic intrusive suite. Decreasing pH and alkalinity with increasing water/rock ratios in model reactions with the kimberlite suite suggest that sampled groundwaters are from both the hypabyssal facies (high pH and alkalinity; low water/rock ratios) and the diatreme facies (low pH and alkalinity; high water/rock ratios). Geochemical concentrations of sampled groundwaters from kimberlites were compared to modelled waters; results indicate that these waters are different from those flowing through local felsic or mafic intrusive rocks. The kimberlitic groundwaters, and modelled waters, contain low concentrations of Mg and Fe, high concentrations of K and Ca, have elevated pH (up to 12.45), and are defined as a Ca-OH? water for the A4 and B30 kimberlites. In contrast, the C14, Diamond Lake and 95-2 kimberlites contain groundwaters that have higher Mg and Fe, lower Ca and K concentrations, and relatively low pH (8.5-10). The reaction model suggests that different minerals precipitate where the water interacts with different kimberlite facies and/or where a different water/rock ratio exists. More hydroxide phases form where pH and hydroxide alkalinity are high. Where kimberlite waters interact with host-rock waters, minerals not likely to be found otherwise, such as magnesite, brucite and magnetite, may be detected along fractures, or near seeps or springs where groundwater comes to surface. Exploration for kimberlites can benefit from the use of groundwater. Groundwater interaction with kimberlitic rocks produces characteristic aqueous geochemical anomalies due to low-temperature serpentinization reactions. The identification of geochemical anomalies in the groundwaters down-flow of a kimberlite and the unusual mineral assemblages that may precipitate from these groundwaters may aid in the location of undiscovered kimberlites.
Abstract: Supergene gold of high fineness, chlorargyrite (AgCl), and alunite occur in veinlets and vugs in the upper 30 m of bonanza Au-Ag veins at the Sleeper deposit, Humboldt County, Nevada. Gold and silver were leached from the primary electrum under acidic conditions caused by iron-sulfide oxidation. In addition, post-ore hydrothermal alteration associated with hot-spring systems along high angle Basin and Range faults may have caused similar Au-Ag leaching on a local scale. Gold and silver were solubilized primarily as chloride complexes AuCl2? and and AgCl2?, respectively. Downward migration of chloride-rich waters containing these species into a more reducing environment resulted in reduction of the AuCl2? complex and gold precipitation, whereas dilution most likely precipitated the associated chlorargyrite. This study and descriptions of other Great Basin shallow Au-Ag deposits suggests that chlorargyrite is a common oxidation product. Hence, the solubility of chlorargyrite probably controls silver contents of shallow groundwaters near oxidized deposits. Shallow groundwater within the arid basins of the region is commonly saline due to evapotranspiration and dissolution of evaporite minerals, creating high chloride concentrations, which increase the solubility of silver as chloride complexes. Chemical modeling using the computer program SOLMINEQ.88 indicates silver contents in the low ppm range are possible in typical saline shallow groundwaters of the Great Basin if: (1) groundwaters have equilibrated with chlorargyrite, and (2) specific adsorption of Ag-chloride species on silicate and Fe-oxyhydroxide surfaces is negligible. Therefore, hydrogeochemical surveys, emphasizing silver content of shallow groundwaters, may be useful in exploring for shallow Au-Ag deposits buried by alluvium along the margins of basins.
Abstract: River water (Water of Luce, Scotland) is used in laboratory experiments designed to investigate physical and chemical properties of Fe. Mn, Cu, Ni, Co, Cd and humic acids in riverine and estuarine systems. Using NaCl, MgCl2 and CaCl2 as coagulating agents, coagulation of dissolved (0.4 ?m filtered) Fe, Cu, Ni, Cd and humic acids increases in a similar matter with increasing salt molarily: Ca2+ is the most dominant coagulating agent. Removal by coagulation with Ca2+ at seawater concentrations ranges from large (Fe-80%. HA-60%, Cu-40%) to small (Ni, Cd-15%) to essentially nothing (Cd, Mn-3%). Destabilization of colloids is the indicated mechanism. Solubility-pH measurements show that between a pH of 3 and 9, Fe, Cu, Ni, Mn, Co and Cd are being held in the dissolved phase by naturally occurring organic substances. Between pH of 2.2 and 1.2 a large proportion of dissolved Fe, Cu. Ni and Cd (72, 35,44 and 36% respectively) is precipitated along with the humic acids; in contrast, Mn and Co show little precipitation (3%). Adsorption-pH experiments, using unfiltered river water spiked with Cu, indicate that adsorption of Cu onto suspended particles is inhibited to a large extent by the formation of dissolved Cu-organic complexes.The experimental results demonstrate that solubilities and adsorption properties of certain trace metals in freshwaters can be opposite to those observed with artificial solutions or predicted with chemical models. Interaction with organic substances is a critical factor.
Abstract: Zinc solutions were equilibrated with both fresh and aged Fe and Al hydrous oxides to measure Zn adsorption. The data conformed to the Langmuir isotherm, and the Langmuir coefficients for Zn adsorption capacities and bonding energies were determined. The adsorption capacities for the aged Fe oxide (goethite) and the aged Al oxide (gibbsite) were the same. The adsorption capacities for both of the fresh oxides (amorphous) were about 10 times those for the aged oxides which corresponded to a 10-fold difference between their respective CEC's and surface areas. The bonding energies for Zn for the fresh Al oxide were three times that for the fresh Fe oxide, but the bonding energies for the two aged oxides were the same. Bonding energies were directly related to adsorption capacities. The inflection points on the Zn adsorption vs. pH curves were between pH 5 and 6 for both oxides.
Abstract: Suspended and equivalent active sediments were collected from streams at 84 sites at the eastern and western sides of a ridge with stratabound Zn mineralization, Rockingham County, Virginia (USA). The purpose was to evaluate the relative effectiveness of suspended and bottom sediment in the geochemical exploration for Mississippi-Valley type Zn ores. The orebody is composed of sphalerite and minor amounts of galena with some chalcopyrite, strikes parallel to the enclosing dolomite beds at N34°E, and cuts vertically across the 30°SE dip. Oxidation of the ore extends to about 100 m in depth. Zinc was effective in detecting the mineralized zone. Zinc in the suspensates provided a denser anomaly system (7 strong and 2 moderate samples) than Zn in the <150 ?m size of the bottom sediment, either totally dissolved (4 strong and 1 moderate anomalies) or extracted with cold 3% HCl (5 strong and 3 moderate anomalies). The magnitude of the high values for suspensate Zn was considerably higher than those for the other sample types studied. Suspensate Zn was complemented by 3 strong suspensate Cu anomalies. The suspensate Zn anomaly dispersion was about 850 m, 400 m of which was upstream from the mineralization. Lead was detected only in the cold acid extraction and in combination with Cu and Zn gave an extensive overlapping multielement anomaly string that targeted the ore zone and had a dispersion downstream from the mineralization of more than 1000 m. The Pb anomalies extended about 900 m upstream and 400 m downstream from the ore zone. Together with suspensate Zn, the Pb anomalies suggest a continuation of mineralization upstrike from the known orebody. The major anomaly systems are along the eastern side of the ridge with comparatively few anomalies present in the drainage along the western side. The concentration of anomalies in the eastern drainage and anomaly disposition with respect to known mineralization result from structural control on the hydromorphic dispersion of metals from the orebody.
Abstract: Suspended sediment geochemistry in the drainage near the Magruder mines, in the easternmost Piedmont, Georgia, targeted Au and base metal mineralization. The mineralization is in a metadacite sequence and is comprised of quartz-vein hosted Au plus the primary minerals chalcopyrite, sphalerite, galena and pyrite. In addition to quartz, the gangue minerals include sericite and chlorite but gahnite and barite are common. The suspended sediments were analysed for 24 elements by instrumental neutron activation analysis and for Cu and Pb by atomic absorption spectrometry. Of the elements analysed, Au, Cu, Zn and Ba are strong indicators of the mineralization but Pb and the rare earth elements (REE) also contribute to the multielement anomalies. The order of downstream dispersion of the elements from the Magruder mineralization is Au < Pb = Ba < Cu = Eu, Yb, Lu < Zn. The strongest Au value in the suspended sediment (1290 ppb) is located at the first sample site downstream (150–200 m) from the mineralized area. The maximum downstream dispersion of strong concentrations of an indicator element (Zn, 2300 ppm) extends to about 800 m from the mine area. Suspended sediment should be included as a sampling medium in geochemical exploration for quartz-vein hosted fine-grained (micron) Au and polymetallic sulfide deposits in felsic metavolcanic rocks in geomorphological and climatological regimes similar to that at the Magruder mines. Suspended sediments may be useful in delimiting areas with saprolite (eluvial) Au deposits and stream reaches with potential for the accumulation of very fine-grained (micron) Au in placer deposits.
Abstract: Over 62 percent of the 193,000 metric tons of gold discovered to date is located in four countries and more than 68 percent occurs in four types of mineral deposits. About 55 percent of the 1,740,000 metric tons of silver found is in four countries and 45 percent is in four types of deposits. Fifty-six percent of the 1.52 billion metric tons of discovered copper is from four countries and four types of deposits contain 88 percent of the total. Over 50 percent of both the 713,000,000 metric tons of zinc and 349,000,000 metric tons of lead discovered to date come from four countries and 70 percent of both metals occur in four types of deposits. All discovered gold would fit in a cube with a height oF 22 m, silver in a 55-m cube, copper in a 550-m cube, zinc in a 460-m cube, and lead in a 310-m cube. At least 74 percent of gold, silver, zinc, and lead is in deposits having average grades above the respective median grades and 44 percent of copper is in deposits with average grades above the median grade of all deposits. Lower grade deposits contain less total metal than higher grade deposits. Tonnage of mineralized rock is an even better predictor of contained metal with over 96 percent of each metal's total residing in deposits having greater than median size and between 47 and 79 percent of metal contained in the largest 10 percent of deposits. World class deposits, defined as the upper 10 percent of deposits in terms of contained metal, account for over 86 percent of all gold, 79 percent of silver, 84 percent of copper, 71 percent of zinc, and 73 percent of lead. These giant deposits contain at least 100 metric tons (3.2 Moz) gold, 2,400 metric tons (77 Moz) silver, 2 million metric tons copper, 1.7 million metric tons zinc, or 1 million metric tons lead. Mineral deposits occur rarely in the earth's crust and large ones are especially uncommon. This analysis shows that only the unusually large deposits can significantly affect supply.
Abstract: Hydrogeochemical exploration was undertaken over an area of 3100 km2 in the northeastern part of Cuddapah Basin to identify target areas for exploring the unconformity-related U-mineralization. Water samples from 626 borewells drilled in the Kurnool Group of the Palnadu sub-basin, Nallamalai Group and basement rocks were collected. For the individual lithological domain, univariate and multivariate statistical techniques were applied to the analytical data on 20 variables, i.e. U, Na, K, Ca, Mg, Cl, SO4, HCO3, CO3, Si, Fe, Cu, Ba, Zn, F, Mn, conductivity, total dissolved salts (TDS), Eh and pH. The R-mode factor analysis establishes geochemical association between U, Na, K, Cl, SO4, HCO3, TDS and conductivity. Another important association is between Fe, Mn and Zn. Maps of factor-1 scores (with high loadings on U) and U-contours, clearly delineate the well-established U-mineralization at Koppunuru-Dwarkapuri in the Palnadu sub-basin. Interestingly, the same maps also display another prominent north–south trending anomaly zone extending over a linear stretch of 45 km, commencing in the basement, passing through the Nallamalai Group and continuing into the younger Kurnool Basin in the eastern part. The hydrogeochemical anomaly around Julakallu is significant for targeting unconformity-related U-mineralization as, in this area, the Kurnool Group sediments unconformably overly the most promising Cumbum Formation comprising low-grade metamorphosed carbonaceous pelites.
9th International Geochemical Exploration Symposium, Saskatoon, Canada, May 12-14, 1982.
Abstract: Approximately 100 springs were sampled as part of a general geochemical survey in a 130 by 140 km multi-mineralized area of the Ouachita Mountains. The study area was subdivided into Area I and Area II based on differences in lithology and mineralization. Area I is composed primarily of the Paleozoic Stanley Shale and the Arkansas Novaculite Formation, and has considerable manganese (often present as psilomelane) and barite mineralization. The barite occurs primarily as replacement deposits in shale in Area I. Area II is composed of Paleozoic and Cretaceous sedimentary rocks, and Quaternary alluvium. Mercury, antimony, strontium and barite mineralization is present. The barite mineralization occurs as cement in the Cretaceous sandstone and gravel in this area.The widely prevalent barite cement in Area II is reflected by higher median and upper range values of barium concentration and also higher median and threshold % BaSO4 saturation values. The presence of barite as cement in the sediments of Area II tends to mask the detection of the barite deposits in this area. Approximately 83% of the sites within 1.7 km of known barite mineralization in Area I were characterized by anomalous barium concentration, and 67% within 3.4 km. Anomalous % BaSO4 saturation values and Ba/Sr ratios produced success rates generally similar to those of anomalous barium concentrations. Anomalous strontium concentrations did not prove effective in detecting barite mineralization.
Abstract: The saturation state of olivine, plagioclase, clinopyroxene, orthopyroxene, Fe-Ti oxides and apatite of variable composition has been assessed in natural waters in Iceland, with temperature ranging from 0°C to 300°C and in situ pH from below 5 to above 10. Cold waters are undersaturated with respect to olivine, orthopyroxene, clinopyroxene and plagioclases indicating that all these minerals tend to dissolve under weathering conditions. With increasing pH and temperature, the waters approach saturation with pyroxene, olivine, and plagioclases. Also, the degree of undersaturation of olivine and orthopyroxene decreases with increasing Fe content of the minerals and Fe-rich olivine and orthopyroxene are stable between 50°C and 150°C, whereas Mg-rich ones tend to dissolve. Natural waters in Iceland are saturated with respect to pure albite when above 50°C. They are, on the other hand, undersaturated with Ca-rich plagioclase up to 250°C where the waters reach saturation. Pure magnetite and hematite are stable at all temperatures. With increasing titanium content, the minerals become unstable, and the waters are undersaturated with respect to pure ulvöspinel at temperatures up to 300°C. Pure ilmenite is, however, close to saturation under weathering conditions but undersaturated above 200°C. F-apatite is close to saturation at all temperatures. On the other hand, undersaturation with respect to OH-apatite is observed at all temperatures. The weathering susceptibilities of primary minerals of basalt in Icelandic waters in increasing order are Mg-olivine>Fe-olivine, Ti-rich magnetite>Ca-plagioclase, Mg-orthopyroxene>Fe-orthopyroxene, clinopyroxene>Na-plagioclase, F-apatite>Ti-rich ilmenite?Ti-poor magnetite, Ti-poor hematite.
Abstract: Acidic water from a copper-mining area has contaminated an alluvial aquifer and stream near Globe, Arizona. The most contaminated groundwater has a pH of 3.3, and contains about 100 mmol/1 SO4, 50 mmol/1 Fe, 11 mmol/1 Al and 3 mmol/1 Cu. Reactions between alluvium and acidic groundwater were first evaluated in laboratory column experiments. A geochemical model was developed and used in the equilibrium speciation program, MINTEQA2, to simulate breakthrough curves for different constituents from the column. The geochemical model was then used to simulate the measured changes in concentration of aqueous constituents along a flow path in the aquifer. The pH was predominantly controlled by reaction with carbonate minerals. Where carbonates had been dissolved, adsorption of H+ by iron oxides was used to simulate pH. Acidic groundwater contained little or no dissolved oxygen, and most aqueous Fe was present as Fe(II). In the anoxic core of the plume, Fe(II) was oxidized by MnO2 to Fe(III), which then precipitated as Fe(OH)3. Attenuation of aqueous Cu, Co, Mn, Ni and Zn was a function of pH and could be quantitatively modeled with the diffuse-layer, surface complexation model in MINTEQA2. Aluminum precipitated as amorphous Al(OH)3 at pH < 4.7 and as AlOHSO4 at pH < 4.7. Aqueous Ca and SO4 were close to equilibrium with gypsum. After the alluvium in the column had reached equilibrium with acidic groundwater, uncontaminated groundwater was eluted through the column to evaluate the effect of reactants on groundwater remediation. The concentration of Fe, Mn, Cu, Co, Ni and Zn rapidly decreased to the detection limits within a few pore volumes. All of the gypsum that had precipitated initially redissolved, resulting in elevated Ca and SO4 concentrations for about 5 pore volumes. Aluminum and pH exhibited the most potential for continued adverse effects on groundwater quality. As H+ desorbed from Fe(OH)3, pH remained below 4.5 for more than 20 pore volumes, resulting in dissolution of AlOHSO4 and elevated aqueous Al.
Abstract: Provides an introduction to the chemistry of the solid-water interface, progressing from the simple to more complex and applied. Discusses the important interfaces in natural systems, especially geochemistry, in natural waters, soils and sediments. The processes occurring at mineral-water, particle-water and organism-water interfaces play critical roles in regulating the composition and ecology of oceans and fresh waters, the development of soils and plant nutrient's supply, preserving the integrity of water repositories and in such applications as water technology and corrosion science.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, V. 73, p. 1-18. Elsevier Publishers, Amsterdam.
Abstract: Colloids are ubiquitous; they occur in natural waters, even in seawater, groundwater and interstitial soilwater, in relatively large concentrations (more than 109 colloids per liter). We consider first an idealized ?-Fe2O3 (hematite) colloid and consider how its surface chemistry, surface speciation and surface charge is affected by its interaction H+, OH?, metal ions and ligands. The interaction is modeled with the help of the surface complex formation theory; effects of electrostatic interaction are taken care of with the Gouy-Chapman diffuse double layer theory. The surface charge of a particle can be estimated from the extent of isomorphic substitution, and from H+, OH?, metal ions and ligands bound to the surface. Competitive surface complex formation equilibria can be used to estimate surface charge and, in turn, surface potential. Steric stabilization by polymer segments needs to be considered when the thickness of the polymer layer is larger than the thickness of the electric double layer, e.g. in seawater, ?h(polymer) > ?D(debye length).. Most surface-controlled processes depend on the identity of the surface species and the geometry of the coordinating shell. The overlapping orbital of the inner-sphere surface complex interconnects the solid phase (ionic or covalent solid, polymer) with the aqueous solution phase. Surface complex formation concepts have been extended to carbonates, sulfides, phosphates and organic particles (cells). The surface structure can be modified by hydrophobic adsorption and the sorption of polymers. Colloid surfaces can mediate electron transfer (including light-induced) processes. Electron cycling mediated by surfaces often complements or substitutes for an enzymatic mechanism.
Abstract: The investigation was conducted within highly and moderately separated highlands and high plateaus where glaciers, stone streams, solifluction, and glacial and fluvio-glacial deposits are widely developed. A capping of Miocene basalts remains in the divides over the Au ore deposits and their oxidation zones. Young water-filled fractures traverse the ore-bearing structures and control the direction of the glacial and river valleys, as well as the location of the lakes, springs, and icings. Gold occurs in small- to average-sized sulphide-Au-quartz veins and in a sulphidized black shale series of Precambrian and Paleozoic age. Both mechanical and hydromorphic dispersion of Au are exhibited clearly in the highlands. The latter is due to the processes of modern oxidation of the Au-bearing sulphide minerals. The anomalies of Au in streams and small lakes are related to supra- and sub-ice waters. In the water of streams Au is present in three forms; colloidal, dissolved, and sorbed. Gold in colloidal form comprises the most ample and contrasty anomalies. The truly dissolved Au is more local and manifests itself close to the source of the stream. Gold sorbed on suspended matter is evident because of a significant removal from the source into the solution. Migration of Au and formation of long (up to 2.5 km) and contrasty dispersions in waters of low dissolved solids is favoured by the presence of organic matter and argillaceous and ferruginous suspensions as well as other sorbents. The anomalies of Au in water either coincide with anomalies in stream sediments over mineralized zones or indicate new mineralized areas not reflected in stream sediments.
In Exploration 97, Geophysics and Geochemistry at the Millenium. Fourth Decennial, Published by the GEO F/X Division of AG Information Systems Ltd.
Abstract: The geochemistry of natural waters traditionally has provided an important avenue for the explorationist to evaluate mineral deposit prospectivity in a third "depth" dimension. Appreciation of basic principles in aqueous geochemistry provide a means to understanding element mobilities and interpreting dispersion patte ns, with applications in both the minerals exploration and environmental disciplines. Applied hydrogeochemistry in minerals exploration peaked in the 1970s, but a new episode in hydrogeochemical minerals exploration has been opened, and investigation of robust element anomalies and dispersion patterns, at concentration levels unattainable a decade ago, can now proceed on a cost-effective basis. This paper is divided into three parts. An abbreviated overview of some fundamentals of inorganic aqueous geochemistry controlling element mobilities, and a brief historical perspective of the use of hydrogeochemistry in minerals exploration comprise the first two parts. These are followed by two case histories illustrating how water surveys can be used in both early-stage and late-stage (pre-feasibility) exploration programs. Inorganic aqueous geochemistry can be simplified by considering three fundamental aspects of this field: solution speciation, mineral precipitation, and element sorption onto solid substrates and solution particulates. These fundamentals are useful in interpreting hydrogeochemical survey results. Applications of hydrogeochemistry to minerals exploration and resource development are presented, with examples from a blind porphyry Cu system under pediment cover in arid terrain of the southwestern United States, and a high-sulfidation Cu ore body in a high-relief tropical environment in the Philippines. Survey results from each example may be understood in terms of hydrogeochemistry fundamentals, and demonstrate useful applications of hydrogeochemistry in minerals exploration programs.
Abstract: Apparent overall equilibrium constants for the adsorption of Cd, Cu, Ni, Pb and Zn onto natural iron oxyhydroxides have been calculated from the partitioning of these trace metals in oxic lake sediments and the in situ measurement of trace metal concentrations in the associated pore waters. Such values obtained from lakes of various pH located on the Precambrian Shield, in the area of Sudbury, Ontario, are compared with equilibrium constants obtained for the adsorption of the trace metals onto iron oxyhydroxides in well-defined media.The field data are consistent with laboratory experiments reported in the literature and with theory. Both the influence of pH upon adsorption and the binding strength sequence observed for the field data agree with theory. At high sediment pH values, the partitioning of Cd, Ni and Zn between the pore waters and the natural iron oxyhydroxides is similar to those reported in the literature for the adsorption of these metals at low surface coverage onto amorphous iron oxyhydroxides in a NaNO3 medium; deviation from this simple model is however observed for Cu and Pb, presumably due to the competitive action of dissolved ligands. At low sediment pH values, the adsorption is much higher than predicted by the simple model and can be explained by the formation of ternary complexes with the iron oxyhydroxide surface.
Trace metals in oxic lake sediments: possible adsorption onto iron oxyhydroxides. Geochim Cosmochim Acta - ResearchGate. Available from: http://www.researchgate.net/publication/223500426_Trace_metals_in_oxic_lake_sediments_possible_adsorption_onto_iron_oxyhydroxides._Geochim_Cosmochim_Acta [accessed Oct 30, 2015].
Abstract: The interactions of humic substances from Esthwaite Water with hydrous iron oxides (?-FeOOH, ?-Fe2O3, amorphous Fe-gel) have been examined by measuring adsorption isotherms and by microelectrophoresis. In Na+-Cl?-HCO3?at I = 0.002 M (medium I) the extent of adsorption decreases with increasing pH. The results are consistent with a mechanism involving ligand exchange of humic anionic groups with H2O and OH?of surface Fe-OH2+and Fe-OH groups respectively, with an increasing degree of protonation of the adsorbed humics as the adsorption density increases at constant pH. At pH 7 in a medium containing Mg2+, Ca2+ and SO42?, at their Esthwaite Water concentrations and at I= 0.002 M (medium II) the adsorption capacity of goethite (?-FeOOH) is approximately twice that in medium I. Electrophoresis experiments show that the extra capacity is associated with coadsorption of Mg2+ and/or Ca2+ ions.. When the iron oxides are added to samples of Esthwaite Water itself they become negatively charged and plots of electrophoretic mobility against pH for the natural water are identical to those in medium II plus humics.
Abstract: At several sites where uranium mineralization was known - West Morvan test area and Lodève basin (France), and Cigar Lake (Saskatchewan, Canada) - we have applied both isotopic and conventional geochemical methods based on major and trace elements concentrations for the detection of concealed uranium deposits. Isotopic methods comprise: (1) the analysis of lead isotopes in groundwater, in order to find any contribution of radiogenic lead from the supposed surrounding or overlying mineralizations: (2) the measurement of 234U/238U activity ratios, variations of which have been proven to be correlated with the presence of uranium accumulatiions. The conventional geochemical methods consist simply in looking for uranium or accompanying elements in groundwaters. A more elaborate method uses the notion of saturation indices of uranium-bearing minerals, thus requiring accurate and complete determinations of major ions and other parameters of groundwaters. The data show that determination of lead isotopes is efficient in many contexts, and gives results that are rather independent of the geochemical characteristics (i.e., reducing or oxidizing) of the waters. The information is global and expresses the presence of uraiium accumulation in the vicinity of the sampling point. No information about grades and distance to the mineralization can be obtained. The anomalous lead can be transported either in solution or on particles, as lead is readily adsorbed on many substrates such as clays or oxides. The analysis of 234/238U activity ratios in groundwaters provide information which is more difficult to decipher. In general, oxidized waters encountering uranium accumulations show high uranium concentrations and low 234U/238U activity ratios, but groundwaters which are more reducing or close to uraninite saturation will produce either high 234U/238U activity ratios if the exchange surface between uranium-bearing phases and groundwater is large enough to promote preferential 234U enrichment in the fluid phase (selective leaching or alpha recoil) or low 234U/238U activity ratios if the exchange surface is smaller. High 234U/238U are observed above dispersed uranium accumulations, frequently situated in the vicinity of massive uranium deposits. This pattern is observed at all studies sites, where contrasting signatures between massive ore zones and surrounding secondary mineralizations are found. In this case, the 234U/238U activity ratio may give information on the succession of the relative ore grades. The use of uranium concentration anomalies has often been questioned, because: (1) non-significant anomalies may appear in oxidizing waters; (2) reduced waters may not be able to record significant U anomalies. The concept of saturation indices of uranium minerals generally allows a more accurate detection of the mineralized areas, but it requires a careful determination of redox potentials, in some cases by in situ measurements, but more generally by calculating the redox potential from dissolved iron, assuming equilibrium with iron oxides. Waters flowing through mineralized areas are generally saturated with respect to uranium minerals, without any clear U concentration peak (this is the case around the Cigar Lake U deposit). If they are not saturated, they are generally strongly oxidized and thus show very high uranium concentrations (this is the case of the Nord-Tréviels part of the Lodève uraniferous basin). If no uranium accumulation is present, saturation indices are generally strongly negative, but in strongly reducing waters, even far from any uranium deposit, one can obtain uraninite saturation. This is the case in Lodève sulphide-bearing waters, or in alkaline geothermal waters from the Pyrénées. If we analyze both U concentration and U saturation index, we can see that waters flowing through mineralized zones have either high U concentrations or are very close to U saturation. One can say that, with little doubt, any water that does not possess one of these two characteristics is of no interest for uranium detection.
In Precious Metals of the Northern Cordillera, Proceedings of a Symposium held Apri, p. 79-88.
Abstract: Stream-water samples (52) collected from approx 1000 km2 of the E half of this graben were analysed for Au, Ag and As by electrothermal AAS. Au, Ag and As values averaged 0.5 p.p.b., 0.11 p.p.b., and 5 p.p.b., respectively. Good correlations were found between anomalies in one or more of these three elements, which were used as pathfinders in 15 of the 17 known Au-Ag mining areas in the graben. Correlation analysis of the log-normalized Au, Ag and As data against log-normalized Si showed significant positive correlation between these elements and Si. Scatter plots of these pairs were used to help define the Au, Ag and As anomalies. The Si content of the waters appears to reflect the chemical weathering intensity of the sample drainage cells.-P.Br.
Abstract: Solubility measurements of Au in dilute to concentrated aqueous NaOH solutions at 25°C have been carried out. The data were fitted to the general half reaction Au(c) + 2 H2O ? AuO2H4?n1?n + nH+ + e? in order to identify the stoichiometry and stability of the hydrolyzed species formed. The monohydroxide, AuOH(H2O)0, is found to be the most stable species up to pH ~ 12. The equilibrium constant for the formation of this species (i.e., n = 1) is logK1 = ?22.57 ± 0.44. Consideration of competitive complexation of Au by a number of inorganic ligands which are encountered in natural waters indicates that AuOH(H2O)0 is the most stable inorganic Au species over a wide range of Eh, pH, and ligand activities. The only inorganic ligands which may occur in natural waters at concentrations high enough to stabilize Au(I) include HS? under reducing conditions, S2O32? under alkaline oxidizing conditions, Cl? in very acidic, oxidizing brines, and possibly CN? locally, in environments where there is biogenic and/or anthropogenic production of cyanide. Calculated equilibrium pe-pH diagrams for Cl? and ?S activities typical of both fresh and sea water show that AuOH(H2O)0 is probably the dominant dissolved Au species in these environments, with the exception of anoxic ocean and lake waters.
Abstract: Copper (Cu) is highly complexed by carbonate and hydroxide ions in natural waters and this complexation determines the concentration of copper species in solution. Results of detailed equilibrium calculations on data from bioassays where alkalinity, pH, hardness, and total copper concentration are different indicate that copper(II) is the chemical species that is toxic to fishes and that alkalinity is the factor controlling copper(II) concentration.
Abstract: Optimum sampling methods in surface water and associated sediments for use in uranium exploration are being studied at thirty sites in Colorado, New Mexico, Arizona and Utah. For water samples, filtering is recommended to increase sample homogeneity and reproducibility because for most elements studied water samples which were allowed to remain unfiltered until time of analysis contained higher concentrations than field-filtered samples of the same waters. Acidification of unfiltered samples resulted in still higher concentrations. This is predominantly because of leaching of the elements from the suspended fraction. U in water correlates directly with Ca, Mg, Na, K, Ba, B, Li and As. In stream sediments, U and other trace elements are concentrated in the finer size fractions. Accordingly, in prospecting, grain size fractions less than 90 ?m (170 mesh) should be analyzed for U. A greater number of elements (21) show a significant positive correlation with U in stream sediments than in water. Results have revealed that anomalous concentrations of U found in water may not be detected in associated sediments and vice versa. Hence, sampling of both surface water and coexisting sediment is strongly recommended.
In Proceedings of the American Chemical Society National Meeting, Washington D.C., August 23-28, 1992.
Abstract: The Bureau of Mines is developing a geochemical predictive model for acid mine drainage (AMD) from waste rock associated with metal mining. The model will identify AMD potential during property exploration and development, and will facilitate preplanning of waste-rock handling. This paper presents results to date on waste-rock characterization, and static and kinetic tests for three selected samples. Sulfide content of the samples was 1.5, 3.5, and 13.0 %, mainly as a mix of euhedral/subhedral and framboidal pyrite. Although acid-base accounting classified all three samples as potential acid producers, effluent pH from the 1.5 % sulfide sample was neutral to slightly basic during 51 weeks of accelerated weathering. Samples containing 3.5 and 13.0 % sulfide continuously produced acidic effluent during the same 51-week period. Sulfate release rates resulting from sulfide oxidation increased with solid-phase sulfide content and decreasing pH. Extrapolated calcium and magnesium release-rate data from the 1.5 % sulfide sample suggest that it should develop AMD after 110 to 130 weeks of laboratory accelerated weathering.
Abstract: Buried and blind deposits, with no direct geological or geochemical manifestation at surface, are becoming increasingly important exploration targets in Australia. A promising approach, tested in a recently completed AMIRA project is presented. It is based on the detection of concealed orebodies from the isotopic compositions of Pb, S and Sr dissolved in groundwaters. This method provides information that is complementary to that obtainable from major and trace element abundance and have the potential to overcome some of the ambiguities in conventional hydrogeochemical surveys.
Abstract: The use of geographic information system (GIS) technology and quantitative data integration methods to investigate the spatial relationship between known volcanic-hosted massive sulfide (VHMS) deposits and the various types of geoscience data can be an effective tool in mineral exploration. A prediction model based on the kernel method was used to investigate the relationship between known VHMS deposits and Cu, Pb, and Zn abundance data collected from stream sediments and till. The model used to compute the prediction map involves two steps. Two empirical distribution functions using rank-order statistics were generated for each layer of gridded geochemical data, one for the areas associated with mineralization and one for the nonmineralized area. The ratio of the two distribution functions (the likelihood ratio) is then computed to emphasize the difference. Bayes’ rule is then used to combine the likelihood ratios for all the data layers. The resulting values are plotted to generate the final prediction map. Cross-validation techniques are used to evaluate the results. The best cross-validation results were obtained using the kernel method with the combination of Pb and Zn abundance data from both stream sediments and tills. In order to reduce exploration costs, a typical exploration program might target 10 percent of the study area with the highest prediction values. In this selected area, 17 (74%) of the 23 known VHMS deposits that occur within the study area were predicted. The Pb and Zn abundance data of stream sediments and tills predicted only 12 (52%) of the 23 known VHMS deposits. Five areas showing high prediction values and no known VHMS deposits were identified as areas that may warrant further exploration.
Abstract: Groundwater geochemistry at the Koongarra uranium ore deposit was investigated in order to gain a detailed understanding of the migration of uranium in a highly weathered water-rock system. Koongarra groundwaters are quite dilute with the total dissolved solids usually below 200 mg/l. The pH is slightly acidic or neutral, and the major chemical characteristics are dominated by magnesium and bicarbonate. Partial pressures of CO2 in the deeper groundwaters are substantially elevated relative to those of surface waters. Groundwater in the mineralized zones exhibits elevated levels of uranium up to three orders of magnitude above background levels. Total organic carbon levels are generally low, suggesting that uranium complexation by organic species plays a minor role. Due to the high bicarbonate concentration, uranium appears to be mobile in the weathered zone as uranyl carbonate complexes. Other inorganic uranium complexants are not present at levels sufficient to influence uranium speciation, with the possible exception of phosphate. On the basis of chemical and isotopic evidence, there are two major inputs of groundwater to the system. The first of these is flows from the vicinity of the Koongarra fault into the Cahill formation, which hosts the uranium mineralization. A second major source is infiltrating waters which permeate downward from the surface, and cause a gradual mixing and dilution of the characteristics of groundwaters from the mineralized zone. The migration of uranium in groundwater is not only perpendicular to the fault, but includes a component at an angle to it. In the vicinity of borehole C1 (due south of the ore zone), uranium concentrations are comparatively high, given the distance from the orebody. Moving away from the ore zone to the south-east, there is a gradual decrease of groundwater uranium concentrations to background levels over approximately 200 meters, which coincides with the uranium distribution in the solid phase. Therefore, at Koongarra, uranium seems to have migrated over distances of approximately 200 m toward the south-east over a time period estimated to be 1 to 1.5 million years.
Abstract: The concentrations of uranium series radionuclides in groundwater were determined to investigate the migration behavior of radionuclides in the Koongarra ore deposit. Particular attention was given to 238U and alpha-emitting radionuclides in its decay chain, including 234U, 230Th, 226Ra, and 222Rn, and beta-emitting 210Pb. Disequilibrium between various members of the 238U decay chain in the Koongarra system arises from a combination of factors, including differences in solubility, surface affinity, the degree of weathering, diffusion of gaseous 222Rn, alpha-recoil effects and redox processes. Measured groundwater 234U/238U activity ratios were below unity in the surficial weathered zone (shallower than about 20 m depth), and greater than unity in the deeper unweathered zone (>30 m depth). These were attributed to various mechanisms related to the alpha-recoil process. Groundwater concentrations of 230Th, and also 230Th/238U ratios were extremely low, indicating that thorium is immobile in this system. Radium-226 was relatively immobile in groundwaters of the weathered zone, with lower 226Ra/238U ratios than deeper groundwaters. This was attributed to co-precipitation of radium together with manganese and ferric hydroxides at the base of the weathered zone, and also to the greater abundance of radium-sorbing minerals in the weathered zone. Large excess concentrations of 222Rn were found in most Koongarra groundwaters, indicating substantial loss of 222Rn from the solid phase despite its short half-life. The 210Pb/222Rn ratios were relatively constant and it was possible to compute an average scavenging residence time for 210Pb in the groundwater of about 6 days using a simple box model. The patterns of dispersion of uranium series radionuclides in Koongarra groundwaters also suggest that present-day migration is toward the south of the orebody. This conclusion is in agreement with the outcome of the geochemistry study.
Abstract: Acid rock drainage (ARD) solution from an abandoned ore mine (pH 2.7, SO2?4 concentration 411 mmol/l, Fe concentration 93.5 mmol/l) was investigated by photon correlation spectroscopy, centrifugation, filtration, ultrafiltration, scanning electron microscopy, ICP-MS, AAS, ion chromatography, TOC analysis, and extended X-ray absorption fine structure (EXAFS) spectroscopy. A colloid concentration of -1 g/l was found. The prevailing particle size was <5 nm. Iron, As and Pb were the metal constituents of the colloidal particles. The most probable mineralogical composition of the particles is a mixture of hydronium jarosite and schwertmannite. A small amount of a relatively coarse precipitate was formed in the ARD solution during the months after sampling. The colloid particles are obviously an intermediate in the precipitate formation process. The results suggest that the arsenate is bound to the colloids by the formation of a bidentate binuclear inner-sphere surface complex. However, the transformation of the colloidal material to the more aggregated long-term precipitate results in the incorporation of the arsenate into the interior of the Fe hydroxy sulfate crystal structures. Lead seems to occur as anglesite.
