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The Sheahan Diamond Literature Reference Compilation - Technical, Media and Corporate Articles based on Major Region - Guyana
The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcements called the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The references are for personal use information purposes only; when available a link is provided to an online location where the full article can be accessed or purchased directly. Reproduction of this compilation in part or in whole without permission from the Sheahan Diamond Literature Service is strictly prohibited. Return to Diamond Region Index
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
Each article reference in the SDLRC is tagged with one or more key words assigned by Pat Sheahan to highlight the main topics of the article. In addition most references have been tagged with one or more region words. In an effort to make it easier for users to track down articles related to a specific region, KRO has extracted these region words and developed a list of major region words presented in the Major Region Index to which individual region words used in the article reference have been assigned. Each individual Region Report contains in chronological order all the references with a region word associated with the Major Region word. Depending on the total for each reference type - technical, media and corporate - the references will be either in their own technical, media or corporate Region Report, or combined in a single report. Where there is a significant number of technical references there will be a technical report dedicated to the technical articles while the media and corporate references are combined in a separate region report. References that were added in the most recent monthly update are highlighted in yellow within the Region Report. The Major Region words have been defined by a scale system of "general", "continent", "country", "state or province" and "regional". Major Region words at the smaller scales have been created only when there are enough references to make isolating them worthwhile. References not tagged with a Region are excluded, and articles with a region word not matched with a Major Region show up in the "Unknown" report.
Kimberlite - diamondiferous
Lamproite - diamondiferous
Lamprophyre - diamondiferous
Other - diamondiferous
Kimberlite - non diamondiferous
Lamproite - non diamondiferous
Lamprophyre - non diamondiferous
Other - non diamondiferous
Kimberlite - unknown
Lamproite - unknown
Lamprophyre - unknown
Other - unknown
Future Mine
Current Mine
Former Mine
Click on icon for details about each occurrence. Works best with Google Chrome.
CITATION: Faure, S, 2010, World Kimberlites CONSOREM Database (Version 3), Consortium de Recherche en Exploration Minérale CONSOREM, Université du Québec à Montréal, Numerical Database on consorem.ca. NOTE: This publicly available database results of a compilation of other public databases, scientific and governmental publications and maps, and various data from exploration companies reports or Web sites, If you notice errors, have additional kimberlite localizations that should be included in this database, or have any comments and suggestions, please contact the author specifying the ID of the kimberlite: [email protected]
Gold and Diamonds in Guyana: investment opportunities.Two volume prospectus in conjunction with thegovernment.of Guyana and available at $ 275.00United States
Techno-Economic Cons Inc. Park Ave. Attrium 237 21st Fl. N.Y. 10017 Attn:, Two volumes
Diamond exploration and developments in the Republic of Guyana, SouthAmerica.
Mid-continent diamonds Geological Association of Canada (GAC)-Mineralogical Association of Canada (MAC) Symposium ABSTRACT volume, held Edmonton May, pp. 117-120.
Zircon geochronology and Sm Nd isotopic study: further constraints for the Archean and Paleoproterozoic geodynamical evolution of southe eastern Guiana Shield.
Almeida, M.E., Macambira, M.J.B., Valente, S.de C.
New geological and single zircon Pb evaporation dat a from the central Guyana Domain, southeastern Roraima, Brazil: tectonic implications for the central shield.
Journal of South American Earth Sciences, Vol. 26, 3, Nov. pp. 318-328.
Abstract: The Geological and Geodiversity Mapping binational program along the Brazil?Guyana border zone allowed reviewing and in? tegrating the stratigraphy and nomenclature of the Roraima Supergroup along the Pakaraima Sedimentary Block present in northeastern Brazil and western Guyana. The area mapped corresponds to a buffer zone of approximately 25 km in width on both sides of the border, of a region extending along the Maú?Ireng River between Mount Roraima (the tri? ple?border region) and Mutum Village in Brazil and Monkey Mountain in Guyana. The south border of the Roraima basin is overlain exclusively by effusive and volcaniclastic rocks of the Surumu Group of Brazil and its correlated equivalent the Burro?Burro Group of Guyana.
Anais Do 15 Simposio Geologia da Amazonia, Belem , Dec. 5p. Abstract pdf
South America, Guiana
craton
Abstract: The Orocaima Igneous Belt (OIB) is a huge plutono-volcanic belt at the central part of Guiana Shield, consisting mainly of 1.99-1.96 Ga volcano-plutonic rocks with high-K calc-alkaline, A-type and shosho-nitic geochemical signatures. Three A-type granitic bodies from the central part of the OIB have been dated using U-Pb SHRIMP and LA-ICPMS methods. A 1985±11 Ma age was calculated for the Macucal Mountain Granite of the Saracura Suite (Brazil) and ages of 1977±3.9 Ma and 1975±5 were calculated for the alkaline riebeckite granites respectively of the Lontra (Brazil) and Makarapan (Guyana) bodies. These ages are in the same range of those reported for the Aricamã A-type granitoids and the results indicate that different A-type magmatism took place in the 1.993-1.975 Ma interval along the OIB, coeval to high-K calc-alkaline and shoshonitic magmatism. This scenario fits well to a post-collisional setting.
Abstract: Interpretations of magnetic anomolies, fracture-zone geometry, and continental-oceanic crust transitions frame the debate surrounding the tectonic opening of the Equatorial and South Atlantic Ocean. Misinterpretations of movement in this region lead to misalignments and misunderstanding of the depositional environments at the margins. This article presents further evidence of the Guiana Shield's role during the initial separation between the American and African plates. Research suggests that the structure of the larger Guiana basin was controlled by the reactivation of Paleozoic and early Mesozoic faults, inherited from older orogenic belts. The same river paths fed the basin with clastic deposits for several tens to hundreds of millions of years. A network of NNW-SSE and NNE-SSW lineaments along the Atlantic margin coast and their onshore continuity at the edge of the Guiana Shield denote relics of deep faulting associated with the early rifting of the central Atlantic Ocean during early Jurassic, between 190 and 170 million years (Ma) (Fig. 1). These older faults were reactivated during Cretaceous E-W drift, a fact that created a favorable Tertiary-to-present structural and depositional environment for southward-shoreward hydrocarbon migration in the South American-Central Equatorial Atlantic margin (OGJ, Jan. 4, 2016, p. 42).
Abstract: Among fancy-color diamonds, natural-color green stones with saturated hues are some of the rarest and most sought after. These diamonds are colored either by simple structural defects produced by radiation exposure or by more complex defects involving nitrogen, hydrogen, or nickel impurities. Most of the world’s current production of fine natural green diamonds comes from South America or Africa. Laboratory irradiation treatments have been used commercially since the late 1940s to create green color in diamond and closely mimic the effects of natural radiation exposure, causing tremendous difficulty in gemological identification. Compounding that problem is a distinct paucity of published information on these diamonds due to their rarity. Four different coloring mechanisms—absorption by GR1 defects due to radiation damage, green luminescence from H3 defects, and absorptions caused by hydrogen- and nickel-related defects—can be identified in green diamonds. Careful microscopic observation, gemological testing, and spectroscopy performed at GIA over the last decade allows an unprecedented characterization of these beautiful natural stones. By leveraging GIA’s vast database of diamond information, we have compiled data representative of tens of thousands of samples to offer a look at natural green diamonds that has never before been possible.
Abstract: Placer diamonds from the Proterozoic and Paleoproterozoic terranes of the Guiana Shield in Guyana, have an enigmatic geochemistry and provenance. Diamonds may be derived from kimberlite intrusions, but no outcrops have been identified in the dense tropical terrain. Alternatively, they may be weathered from 1.79 Ga, NE-SW trending mafic dykes of the Avanavero suite or eroded from 1.95 to 1.78 Ga sandstones and conglomerates of the Roraima Formation into recent alluvial river bed deposits [1]. To resolve these uncertainties, we acquired initial samples of 212 placer diamonds from different locations in Guyana for study. Diamonds range in size from 1.1 mm to 1.7 mm with a mean diameter of 1.3±0.2 mm. Diamonds are primarily dodecahedral to cubic, with lesser octahedral and minor macle forms. The diamonds are colourless to brown and most have a green surface skin. Diamond surfaces show diverse textures, including frosting, edge abrasions, network patterns, and ruts. Dissolution features are common and include point bottom trigons, with a diameter of 21±15 ?m. We measured N concentrations using FTIR (measured at 1282 cm-1). Diamonds are Type IaA-IaB with N concentrations of 55 ppm to 210 ppm. Total N ppm vs %NB ratios indicate mantlederived conditions of 1200 ºC and 4.7 GPa. Calculated Shields Parameter shear stresses of 0.0009 dynes/cm2 to 0.0016 dynes/cm2 suggest diamonds could be transported in bedloads derived from medium to very coarse sandstones or coarse- to pebble-sized kimberlitic lithics. Guyana’s diamonds are dissimilar to those from other regions of the Guiana Shield. To further this comparison, we studied 8 diamonds from Eastern Venezuela and Western Colombia on loan from the Smithsonian Museum of Natural History. Compared to Venezuelan and Colombian diamonds, Guyana’s diamonds are dodecahedral, and have a higher degree of dissolution textures, suggestive of higher ƒO2 conditions during kimberlite magma ascent. We will continue to study Guyana’s diamonds using a combination of electron microprobe, ?XRD, and Raman analyses of inclusions. Taken together we hope to infer the provenance of Guyana’s placer diamonds and the petrology of the mantle rocks from which they were derived.
Leal, R.E., Lafon, J.M., da Ros Costa, L.T., Dantas, E.L.
Orosirian magmatic episodes in the erepercuru-trombetas domain ( southeastern Guyana shield: implications for the crustal evolution of the Amazonian craton.
South American Earth Sciences, Vol. 85, pp. 278-297.
Brazilian Journal of Geology, Vol. 47, 1, pp. 43-57.
South America, Brazil, Guyana
craton
Abstract: The Geological and Geodiversity Mapping binational program along the Brazil?Guyana border zone allowed reviewing and in? tegrating the stratigraphy and nomenclature of the Roraima Supergroup along the Pakaraima Sedimentary Block present in northeastern Brazil and western Guyana. The area mapped corresponds to a buffer zone of approximately 25 km in width on both sides of the border, of a region extending along the Maú?Ireng River between Mount Roraima (the tri? ple?border region) and Mutum Village in Brazil and Monkey Mountain in Guyana. The south border of the Roraima basin is overlain exclusively by effusive and volcaniclastic rocks of the Surumu Group of Brazil and its correlated equivalent the Burro?Burro Group of Guyana.
Dyke Swarms of the World: a modern perspective Ed. Srivastava et al. Springer , Chapter pp. 111-154. available
South America, Guiana, Brazil
craton
Abstract: We review geochronological data including U-Pb baddelyite ages of Proterozoic mafic dyke swarms and sills of the Amazonian Craton, as well as their geochemical character and geological settings, in order to arrive at an integrated tectonic interpretation. The information together with the characteristics of coeval volcanic-plutonic suites indicates a cyclicity of the mafic-felsic activity through time and space. At least four LIP/SLIP events are apparent, and each one appears to accompany the stepwise accretionary crustal growth of Amazonia. The oldest two, the Orocaima (1.98-1.96 Ga) and Uatumã (c. 1.89-1.87 Ga) SLIPs, comprise calc-alkaline I-type and subordinate A-type plutonic and volcanic rocks. Synchronous mafic intraplate activity occurs across the Guiana and Central-Brazil Shields. These two events may be caused by interaction between subduction-related processes and mantle plumes with synchronous lithosphere extension during the two time periods. The Avanavero (1.79 Ga) LIP event mostly consists of mafic dykes and sills which are intrusive into the Roraima platform cover, in the Guiana Shield. They show tholeiitic chemistry and similarities with E-MORB and subcontinental lithospheric mantle-derived basalts, whereas the REE pattern suggests affinity with intraplate settings. The age of the Avanavero rocks is identical to the Crepori Diabase, located ca. 1800 km away to the south (Central-Brazil Shield). The youngest LIP event (1.11 Ga), the Rincón del Tigre-Huanchaca, has the Rio Perdido Suite as a component in the Rio Apa Terrane, which is ca. 300 km away from the Rincón del Tigre Complex, located in the SW portion of the Amazonian Craton. Furthermore, the Central-Brazil and Guiana Shields boasts widespread intraplate mafic activity, highlighted by the Mata-Matá (1.57 Ga), Salto do Céu (1.44 Ga) and Nova Floresta (1.22 Ga) mafic sills and the Cachoeira Seca Troctolite (1.19 Ga). Contemporaneous A-type, rapakivi granites with roughly similar ages also occur elsewhere. These particular episodes are extension specific steps of the Mesoproterozoic Amazonia, and the quite large distribution is consistent with LIP events. In a broader perspective, the intermittent Proterozoic intracratonic activity has a barcode that matches LIP/SLIP events in Columbia and Rodinia.
Abstract: Super-deep diamonds (SDDs) are those that form at depths between ?300 and ?1000 km in Earth’s mantle. They compose only 1% of the entire diamond population but play a pivotal role in geology, as they represent the deepest direct samples from the interior of our planet. Ferropericlase, (Mg,Fe)O, is the most abundant mineral found as inclusions in SDDs and, when associated with low-Ni enstatite, which is interpreted as retrogressed bridgmanite, is considered proof of a lower-mantle origin. As this mineral association in diamond is very rare, the depth of formation of most ferropericlase inclusions remains uncertain. Here we report geobarometric estimates based on both elasticity and elastoplasticity theories for two ferropericlase inclusions, not associated with enstatite, from a single Brazilian diamond. We obtained a minimum depth of entrapment of 15.7 (±2.5) GPa at 1830 (±45) K (?450 [±70] km depth), placing the origin of the diamond-inclusion pairs at least near the upper mantle-transition zone boundary and confirming their super-deep origin. Our analytical approach can be applied to any type of mineral inclusion in diamond and is expected to allow better insights into the depth distribution and origin of SDDs.
Brazilian Journal of Geology, Vol. 41, 1, pp. 43-57.
South America, Brazil, Guyana
Guiana shield
Abstract: The Geological and Geodiversity Mapping binational program along the Brazil-Guyana border zone allowed reviewing and integrating the stratigraphy and nomenclature of the Roraima Supergroup along the Pakaraima Sedimentary Block present in northeastern Brazil and western Guyana. The area mapped corresponds to a buffer zone of approximately 25 km in width on both sides of the border, of a region extending along the Maú-Ireng River between Mount Roraima (the triple-border region) and Mutum Village in Brazil and Monkey Mountain in Guyana. The south border of the Roraima basin is overlain exclusively by effusive and volcaniclastic rocks of the Surumu Group of Brazil and its correlated equivalent the Burro-Burro Group of Guyana.
Dyke swarms of the world: a modern perspective., 10.1007/978-981-13-1666-1_4
South America, Guiana, Brazil
magmatism
Abstract: We review geochronological data including U-Pb baddelyite ages of Proterozoic mafic dyke swarms and sills of the Amazonian Craton, as well as their geochemical character and geological settings, in order to arrive at an integrated tectonic interpretation. The information together with the characteristics of coeval volcanic-plutonic suites indicates a cyclicity of the mafic-felsic activity through time and space. At least four LIP/SLIP events are apparent, and each one appears to accompany the stepwise accretionary crustal growth of Amazonia. The oldest two, the Orocaima (1.98-1.96 Ga) and Uatumã (c. 1.89-1.87 Ga) SLIPs, comprise calc-alkaline I-type and subordinate A-type plutonic and volcanic rocks. Synchronous mafic intraplate activity occurs across the Guiana and Central-Brazil Shields. These two events may be caused by interaction between subduction-related processes and mantle plumes with synchronous lithosphere extension during the two time periods. The Avanavero (1.79 Ga) LIP event mostly consists of mafic dykes and sills which are intrusive into the Roraima platform cover, in the Guiana Shield. They show tholeiitic chemistry and similarities with E-MORB and subcontinental lithospheric mantle-derived basalts, whereas the REE pattern suggests affinity with intraplate settings. The age of the Avanavero rocks is identical to the Crepori Diabase, located ca. 1800 km away to the south (Central-Brazil Shield). The youngest LIP event (1.11 Ga), the Rincón del Tigre-Huanchaca, has the Rio Perdido Suite as a component in the Rio Apa Terrane, which is ca. 300 km away from the Rincón del Tigre Complex, located in the SW portion of the Amazonian Craton. Furthermore, the Central-Brazil and Guiana Shields boasts widespread intraplate mafic activity, highlighted by the Mata-Matá (1.57 Ga), Salto do Céu (1.44 Ga) and Nova Floresta (1.22 Ga) mafic sills and the Cachoeira Seca Troctolite (1.19 Ga). Contemporaneous A-type, rapakivi granites with roughly similar ages also occur elsewhere. These particular episodes are extension specific steps of the Mesoproterozoic Amazonia, and the quite large distribution is consistent with LIP events. In a broader perspective, the intermittent Proterozoic intracratonic activity has a barcode that matches LIP/SLIP events in Columbia and Rodinia.
The American Mineralogist, in press available 59p. Pdf
South America, Guyana
diamond crystallography
Abstract: Diamonds have long been mined from alluvial terrace deposits within the rainforest of Guyana, South America. No primary kimberlite deposits have been discovered in Guyana, nor has there been previous studies on the mineralogy and origin of the diamonds. Paleoproterozoic terranes in Guyana are prospective to diamond occurrences because the most productive deposits are associated spatially with the eastern escarpment of the Paleoproterozoic Roraima Supergroup. Geographic proximity suggests that the diamonds are detrital grains eroding from the <1.98 Ga conglomerates, metamorphosed to zeolite and greenschist facies. The provenance and paragenesis of the alluvial diamonds are described using a suite of placer diamonds from different locations across the Guiana Shield. Guyanese diamonds are typically small, and those in our collection range from 0.3 to 2.7 mm in diameter; octahedral and dodecahedral, with lesser cubic and minor macle forms. The diamonds are further subdivided into those with abraded and non-abraded surfaces. Abraded diamonds show various colors in cathodoluminescence whereas most non-abraded diamonds appear blue. In all populations, diamonds are predominantly colorless, with lesser brown to yellow and very rare white. Diamonds are predominantly Type IaAB and preserve moderate nitrogen aggregation and total nitrogen concentrations ranging from trace to ~1971 ppm. The kinetics of nitrogen aggregation indicate mantle-derived residence temperatures of 1124 ± 100 ºC, assuming residence times of 1.3 Ga and 2.6 Ga for abraded and non-abraded diamonds respectively. The diamonds are largely sourced from the peridotitic to eclogitic lithospheric upper mantle based on both ?13C values of -5.82 ± 2.45‰ (VPDB-LSVEC) and inclusion suites predominantly comprised of forsterite, enstatite, Cr-pyrope, chromite, rutile, clinopyroxene, coesite, and almandine garnet. Detrital, accessory minerals are non-kimberlitic. Detrital zircon geochronology indicates diamondiferous deposits are predominantly sourced from Paleoproterozoic rocks of 2079 ± 88 Ma.