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The Sheahan Diamond Literature Reference Compilation - Scientific and Media Articles based on Major Keyword - Lamprophyre
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 Keyword 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 an effort to make it easier for users to track down articles related to a specific topic, KRO has extracted these key words and developed a list of major key words presented in this Key Word Index to which individual key words used in the article reference have been assigned. In most of the individual Key Word Reports the references are in crhonological order, though in some such as Deposits the order is first by key word and then chronological. Only articles classified as "technical" (mainly scientific journal articles) and "media" (independent media articles) are included in the Key Word Index. References that were added in the most recent monthly update are highlighted in yellow.
A Lamprophyre is a volumetrically small ultrapotassic intrusion similar to a lamproite but with no record of being diamond bearing, possibly because they have a fairly shallow origin related to granitic intrusions. Lamprophyres have been spatially associated with orogenic lode gold deposits though no genetic relationship has been established.
Iugs Subcommision on the Systematics of Igneous Rocks; Classification and Nomenclature of Volcanic Rocks, Lamprophyres, carbonatites and Melilitic Rocks; Recommendations and Suggestions.
Neues Jahr. Min., Vol. 134, No. 1, PP. 1-14.
Global
Melilite, Lamprophyre, Carbonatite, Rock Classification
Archean lamprophyre dikes and gold mineralization, Matheson, the conjunction of large-ion lithophile elements (LILE) enriched magmas, deep crustal structure and Auconcentration.
Canadian Journal of Earth Sciences, Vol. 23, pp. 324-43.
Origins of bimodal leucogranite-lamprophyre suites, Climax and Red Mountain porphyry molydenum systems, Colorado: petrologic and strontium isotopicevidence
Colorado School of Mines Quarterly, Vol. 83, No. 2, Summer pp. 1-24
Archean shoshonitic lamprophyres associated with Superior Province golddeposits: distribution, tectonic setting, noble metal abundances and sign. forAu
Spinel chemistry as an indicator of magmatic processes in lamprophyres of Eastern British Columbia
Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Vancouver 90 Program with Abstracts, Held May 16-18, Vol. 15, p. A63. Abstract
Petrogenesis of Archean lamprophyres in the southern Vermilion graniticcomplex, northeastern Minnesota, with implications for the nature of their mantle source
Contributions to Mineralogy and Petrology, Vol. 104, No. 4, pp. 439-452
Neodymium isotopic compositions of Superior Provincelamprophyres:constraints on evolution of the lithospheric mantle and lamprophyric magmagenesis
Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Vancouver 90 Program with Abstracts, Held May 16-18, Vol. 15, p. A142. Abstract
Crystallization of mela-aillikites of the Narsaq region, Gardar alkaline province, south Greenland and relationships to other aillikitic carbonatitic assoc.
Petrology, geochemistry and tectonic significance of Paleoproterozoic alkaline lamprophyres from the Jungel Valley, Mahakostal supracrustal belt, Central India.
Mineralogy and Petrology, Vol. 89, 3-4, pp. 189-215.
Hauser, N., Matteini, M., Omarini, R.H., Pimentel, M.M.
Constraints on metasomatized mantle under central South America: evidence from Jurassic alkaline lamprophyre dykes from the eastern Cordillera, NM Argentina.
Mantle source components of the Early Cretaceous to Paleogene mafic tholeiitic and alkaline magmatism in Rio and related mantle metasomatism processes.
Lithospheric and asthenospheric sources of lamprophyres in the Jiadong Peninsula: a consequence of rapid lithospheric thinning beneath the North Chin a craton?
Geochimica et Cosmochimica Acta, Vol. 124, pp. 250-271.
Geochemistry and radiogenic isotope characteristics of xenoliths in Archean Diamondiferous lamprophyres: implications for the Superior Province cratonic keel.
Abstract: The results of geochronological, mineralogical, petrographical, and geochemical study of the Ilbokich ultramafic lamprophyre are reported. The specific features in the mineral and chemical compositions of the studied ultramafic lamprophyre indicate that it can be regarded as a variety similar to aillikite, while other differences dominated by K-feldspar can be referred to damtjernite. According to Rb-Sr analysis, ultramafic lamprophyre dikes intruded at the turn of the Early and Middle Devonian, about 392 Ma ago. This directly proves the existence of Early Paleozoic alkali-ultramafic magmatism in the northern part of the southwest Siberian Platform. A finding of Devonian alkali-ultramafic lamprophyre is of dual predictive importance. On the one hand, it is indicative of the low probability of finding large diamond-bearing deposits in close association with aillikite. On the other hand, it can be indicative of a possible large Devonian diamond province in the studied territory, where diamondiferous kimberlite is structurally separated from aillikite.
Abstract: Carbonate-rich ultramafic lamprophyres (aillikites) and associated rocks characteristically occur during the early stages of thinning and rifting of cratonic mantle lithosphere, prior to the eruption of melilitites, nephelinites and alkali basalts. It is accepted that they require volatile-rich melting conditions, and the presence of phlogopite and carbonate in the source, but the exact source rock assemblages are debated. Melts similar to carbonate-rich ultramafic lamprophyres (aillikites) have been produced by melting of peridotites in the presence of CO2 and H2O, whereas isotopes and trace elements appear to favor distinct phlogopite-bearing rocks.
Olivine macrocrysts in aillikites are usually rounded and abraded, so that it is debated whether they are phenocrysts or mantle xenocrysts. We have analyzed minor and trace element composition in olivines from the type aillikites from Aillik Bay in Labrador, Canada. We characterize five groups of olivines: [1] mantle xenocrysts, [2] the main phenocryst population, and [3] reversely zoned crystals interpreted as phenocrysts from earlier, more fractionated, magma batches, [4] rims on the phenocrysts, which delineate aillikite melt fractionation trends, and [5] rims around the reversely zoned olivines. The main phenocryst population is characterized by mantle-like Ni (averaging 3400 ?g g? 1) and Ni/Mg at Mg# of 88-90, overlapping with phenocrysts in ocean island basalts and Mediterranean lamproites. However, they also have low 100 Mn/Fe of 0.9-1.3 and no correlation between Ni and other trace elements (Sc, Co, Li) that would indicate recycled oceanic or continental crust in their sources. The low Mn/Fe without high Ni/Mg, and the high V/Sc (2-5) are inherited from phlogopite in the source that originated by solidification of lamproitic melts at the base of the cratonic lithosphere in a previous stage of igneous activity. The olivine phenocryst compositions are interpreted to result from phlogopite and not high modal pyroxene in the source. The presence of kimberlites and ultramafic lamprophyres of Mesozoic age in Greenland indicates the persistence of a steep edge to the cratonic lithosphere at a time when this had been removed from the western flank in Labrador.
Abstract: Lamprophyres from the greenstone belts play a crucial role in deciphering tectonic and geodynamic processes operating during the Archean. This study presents a comprehensive mineralogical and geochemical study of three lamprophyre dykes with calc-alkaline to shoshonitic affinities from the Neoarchean Kadiri schist belt, eastern Dharwar craton, southern India. These rocks display porphyritic-panidiomorphic texture, typical of the lamprophyres with amphibole (magnesio-hornblende) as phenocrysts, biotite as microphenocrysts and feldspar, epidote, titanite and apatite confined to the groundmass. Alteration of biotite to chlorite is observed along with mild deformation in the amphibole phenocrysts. Based on mineralogy and major oxide geochemistry, these rocks are classified as the calc-alkaline lamprophyres. Higher Ba/Nb and low Nb/La points to their derivation from an enriched lithospheric mantle source and higher Th/Yb ratio along with negative TNT (Ti-Nb-Ta) and Zr-Hf anomalies on the primitive mantle (PM) normalized multi-element diagram indicates dehydrated fluids from the foundering slab could be the possible metasomatic agent. Fractionated HREE ratios (GdN/YbN >1.9) and higher SmN/YbN suggests that the source region lies in the garnet stability field. Higher than PM Rb/Sr along with positive correlation between K/La and Rb/La reveals presence of metasomatic phlogopite in the source region. Strong negative initial ?Nd along with radiogenic 87Sr/86Sr ratios further support an enriched mantle reservoir involved in their genesis. Non-modal batch melting (1-5%) of a mixed source (phlogopite-garnet peridotite) assuming 5% mixing of subducted sediment with ambient mantle wedge (depleted mantle) satisfies the multi-element concentration pattern shown by the Kadiri lamprophyres. The source enrichment can be linked to the accretion-related growth of Dharwar craton and its schist belts during Neoarchean. Our study shows that a majority of lamprophyres associated with the Archean greenstone belts display a shoshonitic character; this highlights the role of subduction-related processes in the growth and evolution of the greenstone belts .
Abstract: Late Proterozoic-Early Cambrian magmatic rocks that range in composition from mafic to felsic have intruded into the Hour region of the central Iranian micro-continent. The Hour lamprophyres are alkaline, being characterized by low contents of SiO2 and high TiO2, Mg# values, high contents of compatible elements, and are enriched in LREE and LILE but depleted in HFSE. Mineral chemistry studies reveal that the lamprophyres formed within a temperature range of ?1200? to 1300?C and relatively moderate pressure in subvolcanic levels. The Hour lamprophyres have experienced weak fractional crystallization and insignificant crustal contamination with more primitive mantle signatures. They were derived from low degree partial melting (1-5%) of the enriched mantle characterized by phlogopite/amphibole bearing lherzolite in the spinel-garnet transition zone at 75-85 km depth, and with an addition of the asthenospheric mantle materials. We infer the Hour lamprophyres to be part of the alkaline rock spectrum of the Tabas block and their emplacement, together with that of other alkaline complexes in the central Iran, was strongly controlled by pre-existing crustal weakness followed by the asthenosphere-lithospheric mantle interaction during the Early Cambrian.
Abstract: We present a comprehensive petrographic, mineralogical and geochemical study of calc-alkaline lamprophyres (CAL) from the Archean Yilgarn Craton, Western Australia. Previous studies have shown that the emplacement age of CAL from the Eastern Goldfields Superterrane of the Yilgarn Craton is ~2684 to ~2640 Ma. A new Rb/Sr mica age for a CAL sample in the Western Yilgarn is ~2070 Ma. Both Archean and Proterozoic CAL analysed in this study display porphyritic textures and contain phenocrysts of amphibole, minor clinopyroxene and biotite in a fine-grained groundmass dominated by feldspar. High MgO, Ni and Cr abundances (up to 11.9 wt%, 373 and 993 ppm. respectively) are consistent with derivation of primitive magmas from a mantle source. Enrichment in H2O, reflected in the abundance of magmatic amphibole and mica, combined with high whole-rock LILE, Th/Yb ratios and negative Nb-Ta anomalies in trace element patterns are consistent with a source that was metasomatised by hydrous fluids analogous to those generated by Phanerozoic subduction-related processes. Chondritic ?Nd and ?Hf signatures and Archean mantle-like Sr isotope signatures of the Late Archean CAL indicate that the fluid metasomatism required to explain their volatile and trace-element enriched composition shortly preceded partial melting (i.e. there was insufficient time to develop enriched radiogenic isotopic signatures). The concurrence of apparently juvenile radiogenic isotopes and fluid-related trace element compositions requires a geodynamic scenario whereby dehydration of a subducted slab triggered metasomatism of the overlying mantle wedge. Our findings therefore support a subduction setting at ~2.6-2.7 Ga along the eastern margin of the Yilgarn Craton. The CAL from the Western Yilgarn have similar compositions but enriched Sr-Nd-Hf isotopes compared to those in the Eastern Goldfields Superterrane. This signature is consistent with melting of lithospheric mantle domains previously enriched by subduction-related metasomatism. Hence, our study suggests the presence of a subduction setting in the Western Yilgarn during the Archean, which is consistent with previous geodynamic reconstructions. However, the geodynamic trigger for the early Proterozoic event that generated CAL magmatism in the Western Yilgarn is currently unclear.
Abstract: We present a comprehensive petrographic, mineralogical and geochemical study of calc-alkaline lamprophyres (CAL) from the Archean Yilgarn Craton, Western Australia. Previous studies have shown that the emplacement age of CAL from the Eastern Goldfields Superterrane of the Yilgarn Craton is ~2684 to ~2640 Ma. A new Rb/Sr mica age for a CAL sample in the Western Yilgarn is ~2070 Ma. Both Archean and Proterozoic CAL analysed in this study display porphyritic textures and contain phenocrysts of amphibole, minor clinopyroxene and biotite in a fine-grained groundmass dominated by feldspar. High MgO, Ni and Cr abundances (up to 11.9 wt%, 373 and 993 ppm. respectively) are consistent with derivation of primitive magmas from a mantle source. Enrichment in H2O, reflected in the abundance of magmatic amphibole and mica, combined with high whole-rock LILE, Th/Yb ratios and negative Nb-Ta anomalies in trace element patterns are consistent with a source that was metasomatised by hydrous fluids analogous to those generated by Phanerozoic subduction-related processes. Chondritic ?Nd and ?Hf signatures and Archean mantle-like Sr isotope signatures of the Late Archean CAL indicate that the fluid metasomatism required to explain their volatile and trace-element enriched composition shortly preceded partial melting (i.e. there was insufficient time to develop enriched radiogenic isotopic signatures). The concurrence of apparently juvenile radiogenic isotopes and fluid-related trace element compositions requires a geodynamic scenario whereby dehydration of a subducted slab triggered metasomatism of the overlying mantle wedge. Our findings therefore support a subduction setting at ~2.6-2.7 Ga along the eastern margin of the Yilgarn Craton. The CAL from the Western Yilgarn have similar compositions but enriched Sr-Nd-Hf isotopes compared to those in the Eastern Goldfields Superterrane. This signature is consistent with melting of lithospheric mantle domains previously enriched by subduction-related metasomatism. Hence, our study suggests the presence of a subduction setting in the Western Yilgarn during the Archean, which is consistent with previous geodynamic reconstructions. However, the geodynamic trigger for the early Proterozoic event that generated CAL magmatism in the Western Yilgarn is currently unclear.
Abstract: Geochemical and petrological characteristics of lamprophyre dykes at Kalagalla intruded into the auriferous schistose rocks of the Ramagiri- Penakacherla Schist Belt, Anantapur district, Andhra Pradesh, India are presented here. The Kalagalla lamprophyre (KGL) is a melanocratic rock exhibiting typical knobby or pustular texture on the surface. The microtextures and mineralogy typical of lamprophyres are obscured by metamorphism; however, it exhibits porphyritic, nemato-granoblastic texture representative of greenschist facies of metamorphism. The rock is sheared and possesses several globules formed by polycrystalline aggregates of calcite rimmed by coronitic subhedral plagioclase and biotite, evidencing its mantle-magmatic origin. The mineral assemblages noticed in thin-sections include amphibole, plagioclase, biotite, phlogopite and calcite ocelli as essential while apatite, zircon, magnetite, ilmenite, Ni-bearing chalcopyrite and pyrite as accessory phases. The SEM-EDS investigation on the accessory minerals revealed accessory sulphide and silicate phases like As-free pyrite, haematitised Ni-bearing chalcopyrite and Ni-As-Co- minerals indicative of sulphidation associated with greenstone auriferous lodes, along with silicates like LREE-bearing titanite partially transformed into leucoxene and oxide phases like magnetite altered to goethite at places. Based on mineral chemistry, whole rock geochemistry, presence of amphibole and dominance of plagioclase, the KGL is classified as a calc-alkaline variety in general and as spessartite in particular possessing shoshonitic affinity. No anomalous chemical composition is noticed in the ocellar calcite. The LREE-bearing titanite appears to be the contributor of LREE enrichment. The high Mg# (77- 79), Ni (153-162 ppm) and Cr (380-470 ppm) support a mantle source. The absence of Eu anomaly reflects lack of plagioclase fractionation. The high Zr/Hf ratio (163-202) indicates absence of crustal contamination and contribution of magmatic carbonate at the source to form ocelli as product of late-stage liquid silicate-carbonate immiscibility of segregation mechanism. The trace and REE patterns (?REE: 326-343 ppm, LREE>HREE) indicate involvement of residual garnet at the source presumably enriched in phlogopite in a ‘subduction-related’ environment.
Abstract: Lamprophyres are some of the oldest recognized alkaline rocks and have been studied for almost the last 150 years. Known for hosting economic minerals such as gold, diamond and base metals, they are also significant in our understanding of the deep-mantle processes (viz., mantle metasomatism and mantleplume-lithosphere interactions) as well as large-scale geodynamic processes (viz., subduction-tectonics, supercontinent amalgamation and break-up). The Indian shield is a collage of distinct cratonic blocks margined by the mobile belts and manifested by large igneous provinces (LIPs) such as the Deccan. A plethora of lamprophyres, varying in age from the Archaean to the Eocene, with diverse mineralogical and geochemical compositions, are recorded from the Indian shield and played a key role in clarifying the tectonic processes, especially during the Paleo- and Mesoproterozoic and the Late Cretaceous. A comprehensive review of the occurrence, petrology, geochemistry and origin of the Indian lamprophyres is provided here highlighting their tectonomagmatic significance. The relationship of the lamprophyres to the Kimberlite clan rocks (KCRs), focusing on the Indian examples, is also critically examined.
Abstract: We report a 40Ar/39Ar Mesoproterozoic radiometric age for a calc-alkaline lamprophyre dyke from the Mudigubba area towards the western margin of the Cuddapah Basin, Eastern Dharwar Craton (EDC), Southern India. Amphibole phenocryst separates from this lamprophyre yielded a plateau age of 1169 ± 8 Ma (2? ), which is almost 50 million years older than the majority of radiometric dates available for the Wajrakarur field kimberlites which are proximal to this dyke. Bulk-rock Sr-Nd isotopic analyses of the Mudigubba lamprophyre dykes (?Nd(t) between -13.3 and -12.4) reveal their derivation from an old, enriched, continental lithospheric mantle unlike the kimberlites (bulk-rock and perovskite in situ ?Nd(t) between -0.77 and +7.93), which originated either from a chondritic or depleted mantle source. This study provides further evidence for emplacement of compositionally distinct, mantle-derived Mesoproterozoic alkaline magmas in the EDC and highlights the extremely heterogeneous character of the lithospheric mantle beneath this craton.