S. Henning, T. Graupner, Thomas Krassmann, H. Gäbler, S. Goldmann, J. Kus, Peter Onuk
The increasing demand for high-tech trace elements supports the need for systematic investigations of their primary occurrences. Mineralogy and trace element characteristics of hydrothermal base-metal veins from the Ruhr Basin (Ruhrgebiet) and the Rhenish Massif (Bergisches Land) in Germany were studied by energy-dispersive X-ray fluorescence mapping, laser ablation-ICP-mass spectrometry, and electron microprobe analyses. Quantitative trace element analysis proves elevated concentrations of Ge and Ga in sphalerite from the Ruhrgebiet. In addition to about 6 Mt of sphalerite-dominated ore, a potential of about 10 t of Ge is indicated to be concentrated in the Auguste Victoria and Graf-Moltke base-metal deposits in the Ruhrgebiet. Assessments on physicochemical fluid properties and metal sources using vitrinite reflectance analysis and host rock investigation indicate a genetic link between the Carboniferous carbonaceous rocks (hosting a number of coal seams) and significant trace metal enrichment in the veins. Gallium enrichment, outlining primary growth zones in ore stage 1 sphalerite, is facilitated by the alteration of Al-bearing minerals in adjacent host rocks due to intense fluid/rock interaction. Reduced Ga and very low In concentrations in ore stage 2 may reflect sealed fluid pathways or changes in the fluid properties. The high level of organic matter in the system probably supported enrichment of Ge in the hydrothermal fluids. The constantly high levels of fixation of Ge in sector zoning patterns of the sphalerite during both ore stages indicate a continuous supply. Elevated contents of Sb together with Cu, As, and Pb in sectors of the sphalerite grains point to a local enrichment of nanometer-scale inclusions of sulfosalt-like phases. Sphalerite of both districts and even of the two ore stages in the Ruhrgebiet shows variations in δ34S isotope compositions due to varying sulfur sources. Both the host rock composition and the presence of organic matter contributed to the trace metal enrichment in the Ruhrgebiet base-metal sulfides as compared to the low contents typical of base-metal ore from the Bergisches Land.
{"title":"Processes of Enrichment of Trace Metals for High-Tech Applications in Hydrothermal Veins of the Ruhr Basin and the Rhenish Massif, Germany","authors":"S. Henning, T. Graupner, Thomas Krassmann, H. Gäbler, S. Goldmann, J. Kus, Peter Onuk","doi":"10.3749/canmin.2100053","DOIUrl":"https://doi.org/10.3749/canmin.2100053","url":null,"abstract":"\u0000 The increasing demand for high-tech trace elements supports the need for systematic investigations of their primary occurrences. Mineralogy and trace element characteristics of hydrothermal base-metal veins from the Ruhr Basin (Ruhrgebiet) and the Rhenish Massif (Bergisches Land) in Germany were studied by energy-dispersive X-ray fluorescence mapping, laser ablation-ICP-mass spectrometry, and electron microprobe analyses. Quantitative trace element analysis proves elevated concentrations of Ge and Ga in sphalerite from the Ruhrgebiet. In addition to about 6 Mt of sphalerite-dominated ore, a potential of about 10 t of Ge is indicated to be concentrated in the Auguste Victoria and Graf-Moltke base-metal deposits in the Ruhrgebiet. Assessments on physicochemical fluid properties and metal sources using vitrinite reflectance analysis and host rock investigation indicate a genetic link between the Carboniferous carbonaceous rocks (hosting a number of coal seams) and significant trace metal enrichment in the veins. Gallium enrichment, outlining primary growth zones in ore stage 1 sphalerite, is facilitated by the alteration of Al-bearing minerals in adjacent host rocks due to intense fluid/rock interaction. Reduced Ga and very low In concentrations in ore stage 2 may reflect sealed fluid pathways or changes in the fluid properties. The high level of organic matter in the system probably supported enrichment of Ge in the hydrothermal fluids. The constantly high levels of fixation of Ge in sector zoning patterns of the sphalerite during both ore stages indicate a continuous supply. Elevated contents of Sb together with Cu, As, and Pb in sectors of the sphalerite grains point to a local enrichment of nanometer-scale inclusions of sulfosalt-like phases. Sphalerite of both districts and even of the two ore stages in the Ruhrgebiet shows variations in δ34S isotope compositions due to varying sulfur sources. Both the host rock composition and the presence of organic matter contributed to the trace metal enrichment in the Ruhrgebiet base-metal sulfides as compared to the low contents typical of base-metal ore from the Bergisches Land.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123319075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Thematic Issue on Critical Minerals: The Canadian Mineralogist Keeping up with the Hot Topics","authors":"","doi":"10.3749/canmin.int013","DOIUrl":"https://doi.org/10.3749/canmin.int013","url":null,"abstract":"","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"422 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116533477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Christina Loidolt, R. Zimmermann, Laura Tusa, S. Lorenz, D. Ebert, R. Gloaguen, S. Broom-Fendley
The Storkwitz carbonatite breccia, located near Delitzsch, Germany, is one of the few European domestic rare earth elements (REE) deposits, but is relatively understudied owing to more than 100 m of Cenozoic sedimentary cover. We present the results of a petrological investigation of the recently acquired ∼700 m-deep SES 1/2012 borehole. The Storkwitz breccia is composed of clasts of country rock and carbonatite ranging from <1 mm to ∼30 cm in size, cemented by ankeritic carbonatite. Extensive fenitization and biotitization mainly affects clasts of coarse-grained granitoids and medium-grained dolomite-calcite-carbonatites. An intersection of Storkwitz breccia at 425 m to 542 m contains local REE enrichment up to ∼1.7 wt.%. total rare earth oxides, which is predominantly contained in a REE-fluorcarbonate bearing mineral assemblage. The assemblage locally forms irregularly shaped vug-like features and rare hexagonal pseudomorphs in clasts of fine-grained ankerite-carbonatite. The REE-fluorcarbonate mineral assemblage formed prior to brecciation in the ankerite-carbonatite, which paragenetically fits with recent experimental and fluid inclusion data demonstrating the importance of late magmatic processes in forming carbonatite-hosted REE mineralization, possibly from an evolved ‘brine-melt' phase. Our findings indicate that minor REE recrystallization and redistribution occurred during late-stage hydrothermal or supergene processes, without leading to significant REE enrichment in the upper part of the breccia compared to the lower part. Cross-cutting faults represent the last deformation event and post-date carbonatite intrusion and fenitization. They may represent important conduits for late-stage hydrothermal or supergene fluids responsible for recrystallization of the breccia matrix to a cryptocrystalline oxide mineral assemblage. Our findings highlight the importance of REE enrichment in late-stage ‘brine-melt' phases through magmatic fractionation and in situ hydrothermal replacement.
{"title":"New Insights into the Rare Earth Element Mineralization of the Storkwitz Carbonatite, Germany","authors":"Christina Loidolt, R. Zimmermann, Laura Tusa, S. Lorenz, D. Ebert, R. Gloaguen, S. Broom-Fendley","doi":"10.3749/canmin.2100061","DOIUrl":"https://doi.org/10.3749/canmin.2100061","url":null,"abstract":"The Storkwitz carbonatite breccia, located near Delitzsch, Germany, is one of the few European domestic rare earth elements (REE) deposits, but is relatively understudied owing to more than 100 m of Cenozoic sedimentary cover. We present the results of a petrological investigation of the recently acquired ∼700 m-deep SES 1/2012 borehole. The Storkwitz breccia is composed of clasts of country rock and carbonatite ranging from <1 mm to ∼30 cm in size, cemented by ankeritic carbonatite. Extensive fenitization and biotitization mainly affects clasts of coarse-grained granitoids and medium-grained dolomite-calcite-carbonatites. An intersection of Storkwitz breccia at 425 m to 542 m contains local REE enrichment up to ∼1.7 wt.%. total rare earth oxides, which is predominantly contained in a REE-fluorcarbonate bearing mineral assemblage. The assemblage locally forms irregularly shaped vug-like features and rare hexagonal pseudomorphs in clasts of fine-grained ankerite-carbonatite. The REE-fluorcarbonate mineral assemblage formed prior to brecciation in the ankerite-carbonatite, which paragenetically fits with recent experimental and fluid inclusion data demonstrating the importance of late magmatic processes in forming carbonatite-hosted REE mineralization, possibly from an evolved ‘brine-melt' phase. Our findings indicate that minor REE recrystallization and redistribution occurred during late-stage hydrothermal or supergene processes, without leading to significant REE enrichment in the upper part of the breccia compared to the lower part. Cross-cutting faults represent the last deformation event and post-date carbonatite intrusion and fenitization. They may represent important conduits for late-stage hydrothermal or supergene fluids responsible for recrystallization of the breccia matrix to a cryptocrystalline oxide mineral assemblage. Our findings highlight the importance of REE enrichment in late-stage ‘brine-melt' phases through magmatic fractionation and in situ hydrothermal replacement.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133247233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Eastman, C. Gammons, K. Goemann, Amanda Griffith
Weathering processes superimposed onto exhumed hydrothermal ore deposits in western North America have developed secondary mineral assemblages that inform the near-surface evolution of these systems within the context of Basin and Range extension. The occurrence of the secondary phosphate mineral turquoise [CuAl6(PO4)4(OH)8·4H2O] in the weathering profile of Laramide porphyry copper deposits is widely documented, although previous studies on the composition and distribution of turquoise are largely restricted to the archaeological literature. In this study, we use the world-class Butte porphyry-epithermal system to study the occurrence, paragenesis, and mineral chemistry of turquoise and related phosphates in the weathering profile of the deposit. Field observations, mineral textures by optical microscopy, electron microprobe analyses, and geochemical modeling show that blue, Al-endmember turquoise formed exclusively at or immediately below the pre-mining water table, within the chalcocite enrichment blanket and in the absence of significant FeIII. At higher structural levels above the pre-mining water table, green FeIII-bearing turquoise [Cu(Al,FeIII)6(PO4)4(OH)8·4H2O] is commonly intergrown with jarosite and/or tinticite at the micron scale. We show that jarosite, tinticite, and FeIII-bearing turquoise formed at the expense of pre-existing, Al-endmember turquoise after extensional faulting caused a relative lowering of the water table in the eastern fault block of the deposit. The low solubility of the FeIII-phosphates tinticite and strengite in the leach cap environment suggests that it is unlikely that these minerals formed directly from oxidized meteoric water. Electron probe microanalysis documented the presence of As and F in blue Al-endmember turquoise and Cl in green FeIII-bearing turquoise. The presence of Cl in FeIII-bearing turquoise may represent an evaporitic signal associated with basin development as the Butte district was exhumed. The paragenesis of Cu- and Fe-phosphate minerals provides another tool with which to interrogate spatial and temporal relationships in the near-surface evolution of porphyry copper systems.
{"title":"Supergene Turquoise and Associated Phosphate Minerals of the Porphyry-Lode System at Butte, Montana, USA","authors":"K. Eastman, C. Gammons, K. Goemann, Amanda Griffith","doi":"10.3749/canmin.2100068","DOIUrl":"https://doi.org/10.3749/canmin.2100068","url":null,"abstract":"\u0000 Weathering processes superimposed onto exhumed hydrothermal ore deposits in western North America have developed secondary mineral assemblages that inform the near-surface evolution of these systems within the context of Basin and Range extension. The occurrence of the secondary phosphate mineral turquoise [CuAl6(PO4)4(OH)8·4H2O] in the weathering profile of Laramide porphyry copper deposits is widely documented, although previous studies on the composition and distribution of turquoise are largely restricted to the archaeological literature. In this study, we use the world-class Butte porphyry-epithermal system to study the occurrence, paragenesis, and mineral chemistry of turquoise and related phosphates in the weathering profile of the deposit. Field observations, mineral textures by optical microscopy, electron microprobe analyses, and geochemical modeling show that blue, Al-endmember turquoise formed exclusively at or immediately below the pre-mining water table, within the chalcocite enrichment blanket and in the absence of significant FeIII. At higher structural levels above the pre-mining water table, green FeIII-bearing turquoise [Cu(Al,FeIII)6(PO4)4(OH)8·4H2O] is commonly intergrown with jarosite and/or tinticite at the micron scale. We show that jarosite, tinticite, and FeIII-bearing turquoise formed at the expense of pre-existing, Al-endmember turquoise after extensional faulting caused a relative lowering of the water table in the eastern fault block of the deposit. The low solubility of the FeIII-phosphates tinticite and strengite in the leach cap environment suggests that it is unlikely that these minerals formed directly from oxidized meteoric water. Electron probe microanalysis documented the presence of As and F in blue Al-endmember turquoise and Cl in green FeIII-bearing turquoise. The presence of Cl in FeIII-bearing turquoise may represent an evaporitic signal associated with basin development as the Butte district was exhumed. The paragenesis of Cu- and Fe-phosphate minerals provides another tool with which to interrogate spatial and temporal relationships in the near-surface evolution of porphyry copper systems.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"596 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131737809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Huzyk Creek area is situated along the boundary between the Reindeer Zone and the Superior Boundary Zone of the Paleoproterozoic Trans-Hudson Orogen, where the Precambrian rocks are overlain by Phanerozoic cover. Two drill holes intersect graphite schist that is enriched in V, as well as U, Zn, Mo, and Cu, and is hosted by a metamorphosed wacke-mudstone sequence interleaved with variably altered mafic rocks. Whole-rock lithogeochemistry and Sm-Nd isotope chemistry suggest that the wacke-mudstone package is related to the turbidite-derived Burntwood Group of the Kisseynew Domain and was likely deposited relatively proximal to the Flin Flon arc-collage. A model is proposed in which redox-sensitive metals were leached from rocks of the Flin Flon arc-collage during weathering under oxidizing conditions. The metals were transported in oxygenated surface run-off draining the arc-collage and discharged into the Kisseynew Basin. Shallow waters of the Kisseynew Basin were likely oxygenated and biologically productive; however, the basin was likely euxinic at mid-depths. The mixing of the metal-enriched, oxygenated water with organic matter and euxinic water resulted in the reduction of the redox-sensitive metals and the formation of insoluble organometallic complexes and particles. A highstand, or period of tectonic quiescence, likely halted turbidite deposition and allowed for the settling organic and metal-rich particles to create relatively thick deposits. Burial and metamorphism resulted in the organic-rich material being transformed into graphite, while Mo, Cu, and Zn were partitioned into sulfides. The mineral hosts of V and U are not known at this time. The model calls for the fractionation of redox-sensitive metals from the water column shortly after discharge into the Kisseynew Basin and implies that graphitic horizons in relatively close proximity to the Flin Flon arc-collage have a greater potential for metal enrichment than graphite deposits farther removed from the arc. This model could apply to basins of similar metamorphic grade, age, and tectonic setting around the globe.
{"title":"Affinity and Petrogenesis of the Huzyk Creek Metal-Enriched Graphite Deposit: A Metamorphosed Metalliferous Black Shale in the Trans-Hudson Orogen Of Manitoba, Canada","authors":"C. Couëslan","doi":"10.3749/canmin.2100001","DOIUrl":"https://doi.org/10.3749/canmin.2100001","url":null,"abstract":"\u0000 The Huzyk Creek area is situated along the boundary between the Reindeer Zone and the Superior Boundary Zone of the Paleoproterozoic Trans-Hudson Orogen, where the Precambrian rocks are overlain by Phanerozoic cover. Two drill holes intersect graphite schist that is enriched in V, as well as U, Zn, Mo, and Cu, and is hosted by a metamorphosed wacke-mudstone sequence interleaved with variably altered mafic rocks. Whole-rock lithogeochemistry and Sm-Nd isotope chemistry suggest that the wacke-mudstone package is related to the turbidite-derived Burntwood Group of the Kisseynew Domain and was likely deposited relatively proximal to the Flin Flon arc-collage. A model is proposed in which redox-sensitive metals were leached from rocks of the Flin Flon arc-collage during weathering under oxidizing conditions. The metals were transported in oxygenated surface run-off draining the arc-collage and discharged into the Kisseynew Basin. Shallow waters of the Kisseynew Basin were likely oxygenated and biologically productive; however, the basin was likely euxinic at mid-depths. The mixing of the metal-enriched, oxygenated water with organic matter and euxinic water resulted in the reduction of the redox-sensitive metals and the formation of insoluble organometallic complexes and particles. A highstand, or period of tectonic quiescence, likely halted turbidite deposition and allowed for the settling organic and metal-rich particles to create relatively thick deposits. Burial and metamorphism resulted in the organic-rich material being transformed into graphite, while Mo, Cu, and Zn were partitioned into sulfides. The mineral hosts of V and U are not known at this time. The model calls for the fractionation of redox-sensitive metals from the water column shortly after discharge into the Kisseynew Basin and implies that graphitic horizons in relatively close proximity to the Flin Flon arc-collage have a greater potential for metal enrichment than graphite deposits farther removed from the arc. This model could apply to basins of similar metamorphic grade, age, and tectonic setting around the globe.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130156445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Schoneveld, S. Barnes, I. Puchtel, S. Tessalina, M. Locmelis
The abundance of Ru in chromite has been suggested as an indicator of sulfide liquid saturation in komatiites. The komatiite magma-derived Archean Coobina intrusion is known to be barren in terms of sulfide mineralization. Therefore, the Coobina intrusion can serve as a useful case study to test the applicability of Ru abundance in chromite as a potential indicator for sulfide mineralization, as well as for better understanding the PGE-chromite association in general. The Coobina intrusion is a highly deformed layered intrusion interpreted to be a flared dike. It contains multiple massive chromitite seams that have been recently mined for metallurgical-grade chromite. In this study, 18 samples from chromitite seams throughout this intrusion are investigated for their whole-rock platinum group element (PGE) contents, which are compared to their chromite mineral chemistry (including PGE content), the platinum group mineral (PGM) mineralogy, and Re-Os isotope systematics. Each sample has a similar chromite major and minor element chemistry, but a unique trace element signature, even within the same seam. In general, there are higher concentrations of Ru (>300 ppb) within chromite in the southeast (toward the feeder dike) and lower concentrations (<50 ppb Ru) in the northwest. At a sample scale, Ru in the whole rock and Ru in solid solution in the chromite are inversely correlated, while Ir shows a positive correlation between the whole rock and chromite mineral chemistry, indicating differing partitioning behaviors within the iridium-group PGE (IPGE = Os, Ir, Ru). The inverse correlation between Ru in solid solution within chromite and Ru in whole-rock chromitite suggests that, for seams with high Ru in whole rock, Ru is occurring within separate PGM phases. This is supported by the observation that the samples with high whole-rock Ru also have a high number of visible metal alloy and/or PGM inclusions. Although these inclusions are not necessarily Ru-rich phases, their presence suggests that there is a preference for these samples to form nuggets, which may restrict Ru partitioning into the chromite crystal structure. We suggest that the low Ru values in the Coobina chromite are a result of transient sulfide saturation. The Re-Os isotopic composition of the Coobina chromitite is chondritic [γ187Os(3.189 Ga) = −0.63 ± 0.21] and is consistent with derivation of the Coobina parental magma from the convecting upper mantle source, providing evidence for the mantle origin of the Coobina PGE inventory. If using chromite as a detrital indicator mineral for magmatic sulfide exploration, it must be kept in mind that transient sulfide saturation within chromitite seams may give a false positive signature.
{"title":"Distributions of Platinum Group Elements and Re-Os Isotope Systematics in Chromite from the Coobina Chromitite Deposit in Western Australia: Implications for Chromite as a Sulfide Mineralization Indicator","authors":"L. Schoneveld, S. Barnes, I. Puchtel, S. Tessalina, M. Locmelis","doi":"10.3749/canmin.2200006","DOIUrl":"https://doi.org/10.3749/canmin.2200006","url":null,"abstract":"\u0000 The abundance of Ru in chromite has been suggested as an indicator of sulfide liquid saturation in komatiites. The komatiite magma-derived Archean Coobina intrusion is known to be barren in terms of sulfide mineralization. Therefore, the Coobina intrusion can serve as a useful case study to test the applicability of Ru abundance in chromite as a potential indicator for sulfide mineralization, as well as for better understanding the PGE-chromite association in general.\u0000 The Coobina intrusion is a highly deformed layered intrusion interpreted to be a flared dike. It contains multiple massive chromitite seams that have been recently mined for metallurgical-grade chromite. In this study, 18 samples from chromitite seams throughout this intrusion are investigated for their whole-rock platinum group element (PGE) contents, which are compared to their chromite mineral chemistry (including PGE content), the platinum group mineral (PGM) mineralogy, and Re-Os isotope systematics. Each sample has a similar chromite major and minor element chemistry, but a unique trace element signature, even within the same seam. In general, there are higher concentrations of Ru (>300 ppb) within chromite in the southeast (toward the feeder dike) and lower concentrations (<50 ppb Ru) in the northwest. At a sample scale, Ru in the whole rock and Ru in solid solution in the chromite are inversely correlated, while Ir shows a positive correlation between the whole rock and chromite mineral chemistry, indicating differing partitioning behaviors within the iridium-group PGE (IPGE = Os, Ir, Ru). The inverse correlation between Ru in solid solution within chromite and Ru in whole-rock chromitite suggests that, for seams with high Ru in whole rock, Ru is occurring within separate PGM phases. This is supported by the observation that the samples with high whole-rock Ru also have a high number of visible metal alloy and/or PGM inclusions. Although these inclusions are not necessarily Ru-rich phases, their presence suggests that there is a preference for these samples to form nuggets, which may restrict Ru partitioning into the chromite crystal structure. We suggest that the low Ru values in the Coobina chromite are a result of transient sulfide saturation. The Re-Os isotopic composition of the Coobina chromitite is chondritic [γ187Os(3.189 Ga) = −0.63 ± 0.21] and is consistent with derivation of the Coobina parental magma from the convecting upper mantle source, providing evidence for the mantle origin of the Coobina PGE inventory.\u0000 If using chromite as a detrital indicator mineral for magmatic sulfide exploration, it must be kept in mind that transient sulfide saturation within chromitite seams may give a false positive signature.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134271488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Wekusko Lake pegmatite field in central Manitoba, Canada, is known for its multiple pegmatite dike occurrences, most remarkably its Li-rich pegmatites of economic importance. The Li-rich pegmatites from Wekusko Lake are the focus of this study and belong to the Green Bay group of the Wekusko Lake pegmatite field. These dikes were dated at ca. 1.78 Ga and were emplaced early during the D4 brittle–ductile deformational event. The results presented here describe in detail the pegmatite mineralogy, textures, and zonation of the Li-rich dikes of the Green Bay group, with emphasis on white mica chemistry. The aim of this study is to establish the nature and evolution of white micas from the Li-rich pegmatites of the Wekusko Lake pegmatite field in Manitoba. We aim to understand the differentiation mechanisms that allowed the high level of trace element enrichment observed in the white micas of the studied Li-rich pegmatites. Major and trace elements in white micas from a representative and well studied pegmatite dike were analyzed by electron microprobe and LA-ICP-MS. White mica compositions and textural evidence were used to define two different populations that seem to have been affected by magmatic processes (fractional crystallization) and a secondary episode of metasomatism. Fractional crystallization modeling of a granitic melt can explain some of the trace element enrichment, but extreme Cs enrichment cannot be explained via this mechanism. We interpret that many metasomatic white micas crystallized in boundary layers. Their compositions are controlled by the local melt composition, but aqueous fluids likely contributed to the development of the white mica textures. The substitution mechanisms at play depend on the type of trend and on the stage of evolution. Li enrichment without M2+ enrichment in metasomatic white mica grains is observed, and it is postulated that Fe3+ in white mica explains this behavior. The K/Rb ratio decreases in white micas with fractionation, whereas the concentrations of incompatible elements, such as Cs, Rb, Tl, Ta, and Li, increase. At Wekusko Lake, the Nb and Ta contents seem to be controlled in part by the presence of columbite group minerals and in part by crystallization in boundary layers.
{"title":"Fractionation and Enrichment Patterns in White Mica from Li Pegmatites of the Wekusko Lake Pegmatite Field, Manitoba, Canada","authors":"D. Benn, T. Martins, R. Linnen","doi":"10.3749/canmin.2200003","DOIUrl":"https://doi.org/10.3749/canmin.2200003","url":null,"abstract":"\u0000 The Wekusko Lake pegmatite field in central Manitoba, Canada, is known for its multiple pegmatite dike occurrences, most remarkably its Li-rich pegmatites of economic importance. The Li-rich pegmatites from Wekusko Lake are the focus of this study and belong to the Green Bay group of the Wekusko Lake pegmatite field. These dikes were dated at ca. 1.78 Ga and were emplaced early during the D4 brittle–ductile deformational event. The results presented here describe in detail the pegmatite mineralogy, textures, and zonation of the Li-rich dikes of the Green Bay group, with emphasis on white mica chemistry. The aim of this study is to establish the nature and evolution of white micas from the Li-rich pegmatites of the Wekusko Lake pegmatite field in Manitoba. We aim to understand the differentiation mechanisms that allowed the high level of trace element enrichment observed in the white micas of the studied Li-rich pegmatites. Major and trace elements in white micas from a representative and well studied pegmatite dike were analyzed by electron microprobe and LA-ICP-MS. White mica compositions and textural evidence were used to define two different populations that seem to have been affected by magmatic processes (fractional crystallization) and a secondary episode of metasomatism. Fractional crystallization modeling of a granitic melt can explain some of the trace element enrichment, but extreme Cs enrichment cannot be explained via this mechanism. We interpret that many metasomatic white micas crystallized in boundary layers. Their compositions are controlled by the local melt composition, but aqueous fluids likely contributed to the development of the white mica textures. The substitution mechanisms at play depend on the type of trend and on the stage of evolution. Li enrichment without M2+ enrichment in metasomatic white mica grains is observed, and it is postulated that Fe3+ in white mica explains this behavior. The K/Rb ratio decreases in white micas with fractionation, whereas the concentrations of incompatible elements, such as Cs, Rb, Tl, Ta, and Li, increase. At Wekusko Lake, the Nb and Ta contents seem to be controlled in part by the presence of columbite group minerals and in part by crystallization in boundary layers.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"1989-1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130265338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shisheng Li, Lin Li, Sheng‐Rong Li, M. Santosh, Ying-xin Song
Potassic alteration is a common feature in hydrothermal ore systems, and both its occurrence and degree can be important features applicable to ore deposit exploration. Here we report results from optical cathodoluminescence (CL) and chemical composition investigations on K-feldspar of different origins in and around the Early Cretaceous lode gold deposits in the Xiaoqinling area, located along the southern margin of the North China Craton. We focus on K-feldspars from an Early Cretaceous biotite monzogranite (G-Kfs), a Paleoproterozoic migmatite (M-Kfs), and a hydrothermal alteration zone of Early Cretaceous gold deposits (H-Kfs). The grain size of G-Kfs ranges from 1 to 4 mm, usually exhibits tartan twinning, and occasionally shows evidence of exsolution. Part of the M-Kfs exhibits tartan twinning, and the grain size shows wide variation (from tens of microns to several centimeters), while the H-Kfs shows no twinning, and the grain size is generally less than 0.5 mm. Optical CL analyses show that the G-Kfs exhibits two emission bands at around 466–472 and 708–713 nm which occur in multiple, alternating dark red and blue zones. The M-Kfs exhibits blue, red, and/or violet-red luminescence resulting from two emission bands at 446–465 and 694–701 nm. The H-Kfs displays a distinct greenish-yellow luminescence resulting from an emission band at 545–550 nm. Electron probe microanalyses show that among the three K-feldspar types, the G-Kfs contains higher Na2O (average: 0.71 wt.%) and Al2O3 (average: 18.79 wt.%) and lower K2O (average: 15.62 wt.%), whereas the H-Kfs shows higher K2O (average: 16.31 wt.%) and lower Na2O (average: 0.45 wt.%) and Al2O3 (average: 18.61 wt.%). The K2O, Na2O, and Al2O3 contents of the M-Kfs are intermediate between those of the G-Kfs and H-Kfs. In transitioning from the G-Kfs, M-Kfs, to H-Kfs, it is noted that the concentrations of Sr, Ba, and Pb decrease progressively, whereas W, V, Zn, Mn, Sc, Ge, and Ga gradually increase. Concentrations of La, Ce, and Eu in the H-Kfs are lower than in the G-Kfs and M-Kfs, and the Cr and Cu concentrations in the G-Kfs are the lowest. Scatter diagrams constructed with Sr, Ba, Pb, and Rb concentrations show that the three types of K-feldspars fall into different fields. These, as well as the CL and spectral properties of K-feldspar, can clearly distinguish the K-feldspars of magmatic, metamorphic, and hydrothermal origin in the study area.
{"title":"Geochemical and Cathodoluminescence Properties as Discriminators to Characterize K-Feldspar in Different Genetic Settings","authors":"Shisheng Li, Lin Li, Sheng‐Rong Li, M. Santosh, Ying-xin Song","doi":"10.3749/canmin.2200004","DOIUrl":"https://doi.org/10.3749/canmin.2200004","url":null,"abstract":"\u0000 Potassic alteration is a common feature in hydrothermal ore systems, and both its occurrence and degree can be important features applicable to ore deposit exploration. Here we report results from optical cathodoluminescence (CL) and chemical composition investigations on K-feldspar of different origins in and around the Early Cretaceous lode gold deposits in the Xiaoqinling area, located along the southern margin of the North China Craton.\u0000 We focus on K-feldspars from an Early Cretaceous biotite monzogranite (G-Kfs), a Paleoproterozoic migmatite (M-Kfs), and a hydrothermal alteration zone of Early Cretaceous gold deposits (H-Kfs). The grain size of G-Kfs ranges from 1 to 4 mm, usually exhibits tartan twinning, and occasionally shows evidence of exsolution. Part of the M-Kfs exhibits tartan twinning, and the grain size shows wide variation (from tens of microns to several centimeters), while the H-Kfs shows no twinning, and the grain size is generally less than 0.5 mm.\u0000 Optical CL analyses show that the G-Kfs exhibits two emission bands at around 466–472 and 708–713 nm which occur in multiple, alternating dark red and blue zones. The M-Kfs exhibits blue, red, and/or violet-red luminescence resulting from two emission bands at 446–465 and 694–701 nm. The H-Kfs displays a distinct greenish-yellow luminescence resulting from an emission band at 545–550 nm.\u0000 Electron probe microanalyses show that among the three K-feldspar types, the G-Kfs contains higher Na2O (average: 0.71 wt.%) and Al2O3 (average: 18.79 wt.%) and lower K2O (average: 15.62 wt.%), whereas the H-Kfs shows higher K2O (average: 16.31 wt.%) and lower Na2O (average: 0.45 wt.%) and Al2O3 (average: 18.61 wt.%). The K2O, Na2O, and Al2O3 contents of the M-Kfs are intermediate between those of the G-Kfs and H-Kfs. In transitioning from the G-Kfs, M-Kfs, to H-Kfs, it is noted that the concentrations of Sr, Ba, and Pb decrease progressively, whereas W, V, Zn, Mn, Sc, Ge, and Ga gradually increase. Concentrations of La, Ce, and Eu in the H-Kfs are lower than in the G-Kfs and M-Kfs, and the Cr and Cu concentrations in the G-Kfs are the lowest. Scatter diagrams constructed with Sr, Ba, Pb, and Rb concentrations show that the three types of K-feldspars fall into different fields. These, as well as the CL and spectral properties of K-feldspar, can clearly distinguish the K-feldspars of magmatic, metamorphic, and hydrothermal origin in the study area.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129539169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. R. Kampf, John M. Hughes, Chiu‐Shun Ma, J. Marty
Pseudodickthomssenite (IMA2021-027), Mg(VO3)2·8H2O, is a new mineral discovered at the Pickett Corral mine, Bull Canyon, Montrose County, Colorado, USA. The mineral formed from the oxidation of montroseite-corvusite assemblages in a moist environment and occurs on asphaltite and on montroseite-corvusite-bearing sandstone in association with dickthomssenite, gypsum, huemulite, lasalite, and trebiskyite. Pseudodickthomssenite is known only from a diverging cluster of striated needles up to about 500 μm long and 20 μm in diameter; the mineral is light tan in color, with a white streak and a silky luster. The crystals are brittle but somewhat flexible in thin fibers. There are two excellent cleavages, {011} and , and the fracture is splintery. The measured density is 1.97(2) g/cm3. Electron probe microanalysis provided the empirical formula [Mg0.99Ca0.01]Σ1.00(V5+O3)2·8H2O. Pseudodickthomssenite is triclinic, P, a = 7.3566(6) Å, b = 9.4672(9) Å, c = 9.5529(9) Å, α = 104.205(7)°, β = 100.786(7)°, γ = 100.157(7)°, V = 616.08(10) Å3, and Z = 2. The structure of pseudodickthomssenite (R1 = 0.0307 for 1124 I > 2σI reflections) contains V5+O5 polyhedra that link by edge-sharing to form a zig-zag [VO3] chain. MgO2(H2O)4 octahedra link the [VO3] chains into a Mg(H2O)4[VO3]4 sheet and the sheets are linked to one another via a complex network of hydrogen bonding involving Mg(H2O)6 octahedra and isolated H2O groups. The structure is very similar to that of dickthomssenite.
伪二钾锰矿(IMA2021-027)， Mg(VO3)2·8H2O，是在美国科罗拉多州蒙特罗斯县Bull Canyon Pickett Corral矿山发现的一种新矿物。这种矿物是在潮湿的环境中由孟长辉石-粗铝石组合氧化形成的，与二辉石、石膏、湿长辉石、拉长石和闪辉石伴生在沥青岩和含孟长辉石-粗铝石的砂岩上。伪二钾辉石岩只存在于长约500 μm、直径约20 μm的发散条纹针状簇中;该矿物呈浅棕褐色，带有白色条纹和丝绸般的光泽。晶体易碎，但在细纤维中具有一定的柔韧性。有两个极好的解理，{011}和，断口呈碎裂状。测得密度为1.97(2)g/cm3。电子探针微量分析得到经验公式[Mg0.99Ca0.01]Σ1.00(V5+O3)2·8H2O。Pseudodickthomssenite为三斜状，P, a = 7.3566(6) Å， b = 9.4672(9) Å， c = 9.5529(9) Å， α = 104.205(7)°，β = 100.786(7)°，γ = 100.157(7)°，V = 616.08(10) Å3, Z = 2。伪二钾锰矿(1124 I > 2σI反射时R1 = 0.0307)的结构由V5+O5多面体组成，这些多面体通过共享边连接形成锯齿状[VO3]链。MgO2(H2O)4八面体将[VO3]链连接成Mg(H2O)4[VO3]4薄片，薄片通过一个复杂的氢键网络相互连接，其中包括Mg(H2O)6八面体和分离的H2O基团。其结构与二钾锰矿非常相似。
{"title":"Pseudodickthomssenite, Mg(VO3)2·8H2O, a New Mineral from the Pickett Corral Mine, Bull Canyon, Montrose County, Colorado, USA","authors":"A. R. Kampf, John M. Hughes, Chiu‐Shun Ma, J. Marty","doi":"10.3749/canmin.2200012","DOIUrl":"https://doi.org/10.3749/canmin.2200012","url":null,"abstract":"\u0000 Pseudodickthomssenite (IMA2021-027), Mg(VO3)2·8H2O, is a new mineral discovered at the Pickett Corral mine, Bull Canyon, Montrose County, Colorado, USA. The mineral formed from the oxidation of montroseite-corvusite assemblages in a moist environment and occurs on asphaltite and on montroseite-corvusite-bearing sandstone in association with dickthomssenite, gypsum, huemulite, lasalite, and trebiskyite. Pseudodickthomssenite is known only from a diverging cluster of striated needles up to about 500 μm long and 20 μm in diameter; the mineral is light tan in color, with a white streak and a silky luster. The crystals are brittle but somewhat flexible in thin fibers. There are two excellent cleavages, {011} and , and the fracture is splintery. The measured density is 1.97(2) g/cm3. Electron probe microanalysis provided the empirical formula [Mg0.99Ca0.01]Σ1.00(V5+O3)2·8H2O. Pseudodickthomssenite is triclinic, P, a = 7.3566(6) Å, b = 9.4672(9) Å, c = 9.5529(9) Å, α = 104.205(7)°, β = 100.786(7)°, γ = 100.157(7)°, V = 616.08(10) Å3, and Z = 2. The structure of pseudodickthomssenite (R1 = 0.0307 for 1124 I > 2σI reflections) contains V5+O5 polyhedra that link by edge-sharing to form a zig-zag [VO3] chain. MgO2(H2O)4 octahedra link the [VO3] chains into a Mg(H2O)4[VO3]4 sheet and the sheets are linked to one another via a complex network of hydrogen bonding involving Mg(H2O)6 octahedra and isolated H2O groups. The structure is very similar to that of dickthomssenite.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129477008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Claude Lamy Morissette, Emmanuelle Cecchi, J. Blais
The Whabouchi pegmatite, located in the James Bay area of Québec, is a lithium-cesium-tantalum pegmatite of albite-spodumene type. In order to evaluate the mineralogical and geochemical variability of the pegmatite, 168 samples were collected from drill core and analyzed for their whole rock geochemistry and mineralogy. The pegmatite is composed of quartz, albite, K-feldspar, spodumene, and muscovite, with trace amounts of spessartine garnet, apatite, beryl, tourmaline, and oxides. It is mostly homogenous, showing greatest variability with respect to the minerals albite, K-feldspar, and spodumene. The Li2O concentration varies between 0.03 and 4.46 wt.%, for an average of 1.53 wt.% and an estimated variability of 53%. Modal mineralogical data showed an inverse correlation between spodumene and the feldspars (albite + K-feldspar), which could also be observed when comparing the Li2O content with the sum of Na2O and K2O. To improve on this relationship, correlation matrices comparing all geochemical components were constructed and allowed the development of an equation able to estimate the Li2O content of the samples within 0.5 wt.% of the measured value. The applicability of the equation to other albite-spodumene type pegmatites was verified with samples collected from the Georgia Lake area of northwestern Ontario. The calculation provided a good approximation of the Li2O content of the samples, with 92% of the data showing a difference of 0.5 wt.% Li2O or less; however, it has an impact on the statistical mean of the data set, the data being recalculated to return an average closer to 1.5 wt.% Li2O. Considering the difficulty in analyzing lithium content of an in situ sample, this relationship could facilitate estimation in the field using portable X-ray fluorescence with the capability of analyzing all required components.
{"title":"Mineralogical Variability of the Whabouchi Pegmatite and its Effect on the Li Concentrations","authors":"Claude Lamy Morissette, Emmanuelle Cecchi, J. Blais","doi":"10.3749/canmin.2100071","DOIUrl":"https://doi.org/10.3749/canmin.2100071","url":null,"abstract":"\u0000 The Whabouchi pegmatite, located in the James Bay area of Québec, is a lithium-cesium-tantalum pegmatite of albite-spodumene type. In order to evaluate the mineralogical and geochemical variability of the pegmatite, 168 samples were collected from drill core and analyzed for their whole rock geochemistry and mineralogy. The pegmatite is composed of quartz, albite, K-feldspar, spodumene, and muscovite, with trace amounts of spessartine garnet, apatite, beryl, tourmaline, and oxides. It is mostly homogenous, showing greatest variability with respect to the minerals albite, K-feldspar, and spodumene. The Li2O concentration varies between 0.03 and 4.46 wt.%, for an average of 1.53 wt.% and an estimated variability of 53%. Modal mineralogical data showed an inverse correlation between spodumene and the feldspars (albite + K-feldspar), which could also be observed when comparing the Li2O content with the sum of Na2O and K2O. To improve on this relationship, correlation matrices comparing all geochemical components were constructed and allowed the development of an equation able to estimate the Li2O content of the samples within 0.5 wt.% of the measured value. The applicability of the equation to other albite-spodumene type pegmatites was verified with samples collected from the Georgia Lake area of northwestern Ontario. The calculation provided a good approximation of the Li2O content of the samples, with 92% of the data showing a difference of 0.5 wt.% Li2O or less; however, it has an impact on the statistical mean of the data set, the data being recalculated to return an average closer to 1.5 wt.% Li2O. Considering the difficulty in analyzing lithium content of an in situ sample, this relationship could facilitate estimation in the field using portable X-ray fluorescence with the capability of analyzing all required components.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122609058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：