Pub Date : 2023-10-20DOI: 10.1007/s00126-023-01222-7
Andreas B. Kaufmann, Marina Lazarov, Stefan Weyer, Martin Števko, Stefan Kiefer, Juraj Majzlan
In this work, we investigated in situ isotopic compositions of antimony (Sb) minerals from two substages of the ore deposits near Pezinok (Slovakia). The δ123Sb values of the primary Sb minerals range from −0.4 and +0.8‰ and increase progressively along the precipitation sequence. In the substage II, the early-formed gudmundite (FeSbS) shows in all sections the lowest δ123Sb values, followed by berthierite (FeSb2S4), stibnite (Sb2S3), and valentinite (Sb2O3) with the heaviest δ123Sb values. A similar trend was observed for the substage III, from the initially-formed stibnite, followed by kermesite (Sb2S2O), valentinite, senarmontite (both Sb2O3), and schafarzikite (FeSb2O4). The evolution can be rationalized by a Rayleigh fractionation model with a starting δ123Sb value in the fluid of +0.3‰, applying the same mineral-fluid fractionation factor to all minerals. Thus, the texturally observed order of mineralization is confirmed by diminishing trace element contents and heavier δ123Sb values in successively crystallized Sb minerals. Antimony in substage III was likely supplied from the oxidative dissolution of stibnite that formed earlier during substage II. The data interpretation, although limited by the lack of reliable mineral-fluid fractionation factors, implies that Sb precipitation within each substage occurred from an episodic metal precipitation, likely associated with a similar Sb isotope fractionation between fluid and all investigated Sb minerals. Large isotopic variations, induced by precipitation from a fluid as a response to temperature decrease, may be an obstacle in deciphering the metal source in hydrothermal ore deposits. However, Sb isotopes appear to be an excellent instrument to enhance our understanding on how hydrothermal systems operate.
{"title":"Changes in antimony isotopic composition as a tracer of hydrothermal fluid evolution at the Sb deposits in Pezinok (Slovakia)","authors":"Andreas B. Kaufmann, Marina Lazarov, Stefan Weyer, Martin Števko, Stefan Kiefer, Juraj Majzlan","doi":"10.1007/s00126-023-01222-7","DOIUrl":"https://doi.org/10.1007/s00126-023-01222-7","url":null,"abstract":"<p>In this work, we investigated in situ isotopic compositions of antimony (Sb) minerals from two substages of the ore deposits near Pezinok (Slovakia). The δ<sup>123</sup>Sb values of the primary Sb minerals range from −0.4 and +0.8‰ and increase progressively along the precipitation sequence. In the substage II, the early-formed gudmundite (FeSbS) shows in all sections the lowest δ<sup>123</sup>Sb values, followed by berthierite (FeSb<sub>2</sub>S<sub>4</sub>), stibnite (Sb<sub>2</sub>S<sub>3</sub>), and valentinite (Sb<sub>2</sub>O<sub>3</sub>) with the heaviest δ<sup>123</sup>Sb values. A similar trend was observed for the substage III, from the initially-formed stibnite, followed by kermesite (Sb<sub>2</sub>S<sub>2</sub>O), valentinite, senarmontite (both Sb<sub>2</sub>O<sub>3</sub>), and schafarzikite (FeSb<sub>2</sub>O<sub>4</sub>). The evolution can be rationalized by a Rayleigh fractionation model with a starting δ<sup>123</sup>Sb value in the fluid of +0.3‰, applying the same mineral-fluid fractionation factor to all minerals. Thus, the texturally observed order of mineralization is confirmed by diminishing trace element contents and heavier δ<sup>123</sup>Sb values in successively crystallized Sb minerals. Antimony in substage III was likely supplied from the oxidative dissolution of stibnite that formed earlier during substage II. The data interpretation, although limited by the lack of reliable mineral-fluid fractionation factors, implies that Sb precipitation within each substage occurred from an episodic metal precipitation, likely associated with a similar Sb isotope fractionation between fluid and all investigated Sb minerals. Large isotopic variations, induced by precipitation from a fluid as a response to temperature decrease, may be an obstacle in deciphering the metal source in hydrothermal ore deposits. However, Sb isotopes appear to be an excellent instrument to enhance our understanding on how hydrothermal systems operate.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Olivine (Fo80-88) from the Shitoukengde deposit exhibits low levels of Ca, Cr, and Al (< 220 ppm) and varying Ni content. The low Ca-Cr-Al contents in olivine and subsolidus temperatures (600–900 °C) indicated by olivine-spinel thermometers align with subsolidus equilibria, emphasizing substantial postcumulus modifications. Therefore, the postcumulus effect must be considered when applying olivine-spinel oxybarometers to intrusive rocks. Back-calculating the spinel Fe–Mg contents to magmatic temperature, the estimated oxidation fugacity (fO2) range between FQM − 1.5 and FQM − 3.0, approximately 0.5 to 1.5 ΔFQM more reduced compared to those calculated from the raw spinel composition. Moreover, the fO2 aligns with results obtained from the olivine-sulfide pair (FMQ − 3.0 to FMQ 0). The considerably reducing state and wide oxidation variation are consistent with the graphite occurrence within the reduced intervals and the systematic fO2 indicated by olivine V/Sc ratios. Combined with the wide olivine Ni range (200–1500 ppm) and the restricted Ni tenor in coexisting sulfides, those findings imply that the olivine-sulfide interaction was predominantly controlled by fO2. Diffusion modeling at magmatic temperatures reveals that the core-level Fe–Ni re-equilibration after crystallization requires hundreds of years. The homogeneous olivine composition suggests that re-equilibrium has been achieved in Shitoukengde. However, in fast cooling systems, olivine may record the status approaching olivine-sulfide equilibration, leading to extensive intragrain Ni variation (up to 1000 ppm). This study highlights that extreme Ni depletion in olivine from sulfide-bearing rocks is a sign of reducing conditions. Strongly Ni-rich olivine, such as those in the Kevitsa deposit, could result from interaction with high-Ni tenor sulfides at oxidizing conditions.
{"title":"Redox-controlled olivine-sulfide equilibration of the Shitoukengde Ni–Cu deposit in Qinghai-Tibet Plateau and its implications","authors":"Ya-Jing Mao, Xuyang Zheng, Tong Pan, Fanglin Yuan, Hua-Liang Huang, Ke-Zhang Qin","doi":"10.1007/s00126-023-01215-6","DOIUrl":"https://doi.org/10.1007/s00126-023-01215-6","url":null,"abstract":"<p> Olivine (Fo80-88) from the Shitoukengde deposit exhibits low levels of Ca, Cr, and Al (< 220 ppm) and varying Ni content. The low Ca-Cr-Al contents in olivine and subsolidus temperatures (600–900 °C) indicated by olivine-spinel thermometers align with subsolidus equilibria, emphasizing substantial postcumulus modifications. Therefore, the postcumulus effect must be considered when applying olivine-spinel oxybarometers to intrusive rocks. Back-calculating the spinel Fe–Mg contents to magmatic temperature, the estimated oxidation fugacity (<i>f</i>O<sub>2</sub>) range between FQM − 1.5 and FQM − 3.0, approximately 0.5 to 1.5 ΔFQM more reduced compared to those calculated from the raw spinel composition. Moreover, the <i>f</i>O<sub>2</sub> aligns with results obtained from the olivine-sulfide pair (FMQ − 3.0 to FMQ 0). The considerably reducing state and wide oxidation variation are consistent with the graphite occurrence within the reduced intervals and the systematic <i>f</i>O<sub>2</sub> indicated by olivine V/Sc ratios. Combined with the wide olivine Ni range (200–1500 ppm) and the restricted Ni tenor in coexisting sulfides, those findings imply that the olivine-sulfide interaction was predominantly controlled by <i>f</i>O<sub>2</sub>. Diffusion modeling at magmatic temperatures reveals that the core-level Fe–Ni re-equilibration after crystallization requires hundreds of years. The homogeneous olivine composition suggests that re-equilibrium has been achieved in Shitoukengde. However, in fast cooling systems, olivine may record the status approaching olivine-sulfide equilibration, leading to extensive intragrain Ni variation (up to 1000 ppm). This study highlights that extreme Ni depletion in olivine from sulfide-bearing rocks is a sign of reducing conditions. Strongly Ni-rich olivine, such as those in the Kevitsa deposit, could result from interaction with high-Ni tenor sulfides at oxidizing conditions.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-19DOI: 10.1007/s00126-023-01218-3
Leanne Schmitt, Thomas Kirnbauer, Thomas Angerer, Rebecca Volkmann, Vladimir Roddatis, Richard Wirth, Sabine Klein
Fe-oxide deposits of the Lahn-Dill-type in the eastern Rhenish Massif comprise haematite and quartz with minor siderite, magnetite, and calcite. The deposits are located in the hanging wall of thick volcaniclastic rock sequences and mark the Middle to Late Devonian boundary. Varying ore types with accompanying footwall rocks were sampled from two formerly important ore deposits, the Fortuna mine (Lahn syncline) and the Briloner Eisenberg mine (East Sauerland anticline), in order to elucidate the interplay of processes leading to ore formation. Deposit geology, petrography, and whole-rock geochemistry suggest that the ores formed by iron mobilisation from deeply altered footwall volcaniclastic rocks, subsequent venting of a modified H2O-CO2-Fe-rich and H2S-poor fluid, and precipitation on the seafloor (sedimentary-type), or locally by metasomatic replacement of wall rocks (replacement-type). Petrographic analysis to the sub-micron scale revealed that the sedimentary-type ores most likely formed from a Fe-Si-rich gel and accompanying maturation. Early gel textures include the presence of spherules, aggregates, tubes, and filamentous stalks consisting of nanocrystalline haematite dispersed in a matrix of microcrystalline quartz. Local diagenetic Fe3+ reduction within the gel is indicated by siderite replacement of haematite. Replacement-type ores formed due to a two-step process including coprecipitation of (precursor) haematite and carbonates and subsequent metasomatic replacement by haematite. These ore-forming processes took place during a time when several restricted shallow marine basins in the north-eastern Rheic Ocean were influenced by extensive volcanism and associated hydrothermal fluid flux. Examples of similar volcanic-associated Fe-oxide occurrences of Silurian to Carboniferous age can be categorised as being of Lahn-Dill-type ores as well.
{"title":"Genesis of Devonian volcanic-associated Lahn-Dill-type iron ores — part I: iron mobilisation and mineralisation style","authors":"Leanne Schmitt, Thomas Kirnbauer, Thomas Angerer, Rebecca Volkmann, Vladimir Roddatis, Richard Wirth, Sabine Klein","doi":"10.1007/s00126-023-01218-3","DOIUrl":"https://doi.org/10.1007/s00126-023-01218-3","url":null,"abstract":"<p>Fe-oxide deposits of the Lahn-Dill-type in the eastern Rhenish Massif comprise haematite and quartz with minor siderite, magnetite, and calcite. The deposits are located in the hanging wall of thick volcaniclastic rock sequences and mark the Middle to Late Devonian boundary. Varying ore types with accompanying footwall rocks were sampled from two formerly important ore deposits, the Fortuna mine (Lahn syncline) and the Briloner Eisenberg mine (East Sauerland anticline), in order to elucidate the interplay of processes leading to ore formation. Deposit geology, petrography, and whole-rock geochemistry suggest that the ores formed by iron mobilisation from deeply altered footwall volcaniclastic rocks, subsequent venting of a modified H<sub>2</sub>O-CO<sub>2</sub>-Fe-rich and H<sub>2</sub>S-poor fluid, and precipitation on the seafloor (sedimentary-type), or locally by metasomatic replacement of wall rocks (replacement-type). Petrographic analysis to the sub-micron scale revealed that the sedimentary-type ores most likely formed from a Fe-Si-rich gel and accompanying maturation. Early gel textures include the presence of spherules, aggregates, tubes, and filamentous stalks consisting of nanocrystalline haematite dispersed in a matrix of microcrystalline quartz. Local diagenetic Fe<sup>3+</sup> reduction within the gel is indicated by siderite replacement of haematite. Replacement-type ores formed due to a two-step process including coprecipitation of (precursor) haematite and carbonates and subsequent metasomatic replacement by haematite. These ore-forming processes took place during a time when several restricted shallow marine basins in the north-eastern Rheic Ocean were influenced by extensive volcanism and associated hydrothermal fluid flux. Examples of similar volcanic-associated Fe-oxide occurrences of Silurian to Carboniferous age can be categorised as being of Lahn-Dill-type ores as well.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-18DOI: 10.1007/s00126-023-01223-6
Sebastian Staude, Laure A.J. Martin, Matvei Aleshin, Marco L. Fiorentini, Gregor Markl
New data on the multiple sulfur isotope signature of Archean sulfides from country rocks and magmatic mineralization at the Moran deposit (Kambalda, Western Australia) were combined with previously published geochemical data to constrain the various stages of the dynamic evolution of this magmatic system, unveiling new insights into the transport mechanisms of sulfide liquids in komatiite magmas. Sulfides in the Archean magmatic and sedimentary host rocks of the komatiites display a unique mass-independent sulfur isotope signature (Δ33S), which records a photochemical reaction of sulfur in an oxygen-poor atmosphere prior to the Great Oxidation Event.
Sedimentary rocks that are thought to be assimilated by komatiite show a distinctly positive Δ33S signature (+ 0.9 to + 2.4‰). Early ore sulfides situated above these sedimentary rocks contain relatively few valuable metals and display an overlapping Δ33S range (+ 0.6 to + 1.0‰). Subsequent but still early ore sulfides are situated above basalt, as the sedimentary rocks were thermo-mechanically eroded by the sulfide melt, displaying more mantle-like signatures (+ 0.2 to + 0.3‰) and valuable metal content - indistinguishable from the main ore deposit. This reflects a progressive dilution of the contaminant signature by the magmatic isotope signature of the komatiite liquid. Calculated volumes of the interaction of silicate melt and sulfide melt to explain the metal tenor of the ore and its Δ33S signature indicate a decoupling between chemical and isotopic signatures. This can be explained by upgrading the sulfide melt with valuable metals simultaneously with the dissolution of sulfur in the komatiite melt.
{"title":"The multiple sulfur isotope architecture of the Kambalda nickel camp, Western Australia","authors":"Sebastian Staude, Laure A.J. Martin, Matvei Aleshin, Marco L. Fiorentini, Gregor Markl","doi":"10.1007/s00126-023-01223-6","DOIUrl":"https://doi.org/10.1007/s00126-023-01223-6","url":null,"abstract":"<p>New data on the multiple sulfur isotope signature of Archean sulfides from country rocks and magmatic mineralization at the Moran deposit (Kambalda, Western Australia) were combined with previously published geochemical data to constrain the various stages of the dynamic evolution of this magmatic system, unveiling new insights into the transport mechanisms of sulfide liquids in komatiite magmas. Sulfides in the Archean magmatic and sedimentary host rocks of the komatiites display a unique mass-independent sulfur isotope signature (Δ<sup>33</sup>S), which records a photochemical reaction of sulfur in an oxygen-poor atmosphere prior to the Great Oxidation Event.</p><p>Sedimentary rocks that are thought to be assimilated by komatiite show a distinctly positive Δ<sup>33</sup>S signature (+ 0.9 to + 2.4‰). Early ore sulfides situated above these sedimentary rocks contain relatively few valuable metals and display an overlapping Δ<sup>33</sup>S range (+ 0.6 to + 1.0‰). Subsequent but still early ore sulfides are situated above basalt, as the sedimentary rocks were thermo-mechanically eroded by the sulfide melt, displaying more mantle-like signatures (+ 0.2 to + 0.3‰) and valuable metal content - indistinguishable from the main ore deposit. This reflects a progressive dilution of the contaminant signature by the magmatic isotope signature of the komatiite liquid. Calculated volumes of the interaction of silicate melt and sulfide melt to explain the metal tenor of the ore and its Δ<sup>33</sup>S signature indicate a decoupling between chemical and isotopic signatures. This can be explained by upgrading the sulfide melt with valuable metals simultaneously with the dissolution of sulfur in the komatiite melt.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. 40Ar/39Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O2-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore.
{"title":"Intraplate orogenesis as a driver of multistage karst-hosted mineralization: the Imini manganese case (Atlas, Morocco)","authors":"Augustin Dekoninck, Jocelyn Barbarand, Gilles Ruffet, Yves Missenard, Nadine Mattielli, Rémi Leprêtre, Abdellah Mouttaqi, Michèle Verhaert, Omar Saddiqi, Johan Yans","doi":"10.1007/s00126-023-01212-9","DOIUrl":"https://doi.org/10.1007/s00126-023-01212-9","url":null,"abstract":"<p>The Imini mining district (southern foreland of the intraplate Atlasic belt of Morocco) hosts the largest Mn resources of North Africa, consisting of two laterally extensive bodies of high-grade pyrolusite-rich manganese ore and a third discontinuous medium-grade coronadite-rich Mn ore in a ~ 10–15-m-thick Cenomanian–Turonian dolostone unit. Until now, the origin and timing of the Mn ore have been poorly constrained. New Pb isotopic ratios show that Triassic series (basalts and ferruginous sandstone) are likely the source of the metals. <sup>40</sup>Ar/<sup>39</sup>Ar dating of K-Mn oxides shows that the Mn-rich orebodies formed during at least three periods: late Cretaceous to late Paleocene (> 58 Ma), late Eocene (ca. 36.3 Ma), and early Burdigalian to early Serravalian probably in two pulses at ca. 19–20 Ma and ca. 13 Ma. These periods coincide with three known building phases of the Atlasic relief during late Cretaceous, late Eocene, and the Early(?)-Middle Miocene. We therefore propose the Atlasic tectonics as the first-order control of the Mn mineralization. Periods with regionally high elevations modified the climate to wetter conditions that supplied meteoric water to feed temporary aquifers. Relief building created the required hydraulic head to sustain (1) fluid-rock interaction between O<sub>2</sub>-poor acidic fluids and the Triassic series, (2) migration of the metal-rich fluid, and (3) to overpressure fluid in the Imini depositional site. The decreasing thickness of Triassic series in front of the Imini anticline forced these low-temperature (< 100 °C) fluids to mix with oxygenated and alkaline ground waters in the karst system and precipitate Mn oxides. The N70°-oriented Atlasic tectonic structure controls the orientation of the Mn deposits. The late Eocene–Early/Middle Miocene uplifts generated additional supplies and/or in situ remobilization of the primary late Cretaceous medium-grade ore to form the high-grade pyrolusite-rich ore.</p><h3 data-test=\"abstract-sub-heading\">Graphical Abstract</h3>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-06DOI: 10.1007/s00126-023-01217-4
Nikola Denisová, Stephen J. Piercey, Markus Wälle
The ABM deposit is a bimodal-felsic, replacement-style volcanogenic massive sulfide deposit (VMS) that is hosted by back-arc affinity rocks of the Yukon–Tanana terrane in the Finlayson Lake VMS district, Yukon, Canada. Massive sulfide zones occur as stacked and stratabound lenses subparallel to the volcanic stratigraphy, surrounded by pervasive white mica and/or chlorite alteration. Remnant clasts of volcanic rocks and preserved bedding occur locally within the massive sulfide lenses and indicate that mineralization formed through subseafloor replacement of pre-existing strata. Three mineral assemblages occur at the ABM deposit: (1) a pyrite–chalcopyrite–magnetite–pyrrhotite assemblage that is associated with Cu–Bi–Se–Co-enrichment and occurs at the center of the massive sulfide lenses; (2) a pyrite–sphalerite assemblage, which occurs more commonly towards lens margins and is enriched in Zn–Pb–Ag–Au–Hg–As–Sb–Ba; and (3) a minor assemblage comprising chalcopyrite–pyrrhotite–pyrite stringers associated with pervasive chlorite alteration, which occurs mostly at the sulfide lens margins. Petrographic observations of preserved primary, zone refining, and metamorphic textures in combination with in situ geochemistry show that the pyrite–sphalerite assemblage formed at lower temperatures (< 270 °C) than the other two mineral assemblages (~ 270–350 °C), and that mineral chemistry in all mineral assemblages was affected by greenschist facies metamorphism, although the effects are limited to recrystallization, small-scale remobilization (< 1 m) and trace element redistribution.
ABM矿床是加拿大育空地区Finlayson Lake VMS地区一个由Yukon - tanana地块弧后亲和岩组成的双峰长英质、置换型火山岩块状硫化物矿床(VMS)。块状硫化物带呈叠置和层控透镜状,与火山地层近平行,被普遍存在的白色云母和/或绿泥石蚀变所包围。在块状硫化物透镜体中局部出现了火山岩残余碎屑和保存的层理,表明成矿是通过海底替换原有地层形成的。ABM矿床有3种矿物组合:(1)黄铁矿-黄铜矿-磁铁矿-磁黄铁矿组合,与cu - bi - se - co富集有关,出现在块状硫化物透镜体的中心;(2)黄铁矿-闪锌矿组合,多产于晶状体边缘,富集Zn-Pb-Ag-Au-Hg-As-Sb-Ba;(3)与绿泥石蚀变有关的黄铜矿-磁黄铁矿-黄铁矿条带组成的小型组合,主要发生在硫化物透镜体边缘。结合原位地球化学观测,对原生、带炼和变质结构进行了岩石学观察,结果表明黄铁矿-闪锌矿组合形成温度(~ 270℃)低于其他两种矿物组合(~ 270 ~ 350℃),并且所有矿物组合中的矿物化学均受到绿片岩相变质作用的影响,但影响仅限于重结晶、小尺度再活化(~ 1 m)和微量元素重分布。
{"title":"Mineralogy and mineral chemistry of the ABM replacement-style volcanogenic massive sulfide deposit, Finlayson Lake district, Yukon, Canada","authors":"Nikola Denisová, Stephen J. Piercey, Markus Wälle","doi":"10.1007/s00126-023-01217-4","DOIUrl":"https://doi.org/10.1007/s00126-023-01217-4","url":null,"abstract":"<p>The ABM deposit is a bimodal-felsic, replacement-style volcanogenic massive sulfide deposit (VMS) that is hosted by back-arc affinity rocks of the Yukon–Tanana terrane in the Finlayson Lake VMS district, Yukon, Canada. Massive sulfide zones occur as stacked and stratabound lenses subparallel to the volcanic stratigraphy, surrounded by pervasive white mica and/or chlorite alteration. Remnant clasts of volcanic rocks and preserved bedding occur locally within the massive sulfide lenses and indicate that mineralization formed through subseafloor replacement of pre-existing strata. Three mineral assemblages occur at the ABM deposit: (1) a pyrite–chalcopyrite–magnetite–pyrrhotite assemblage that is associated with Cu–Bi–Se–Co-enrichment and occurs at the center of the massive sulfide lenses; (2) a pyrite–sphalerite assemblage, which occurs more commonly towards lens margins and is enriched in Zn–Pb–Ag–Au–Hg–As–Sb–Ba; and (3) a minor assemblage comprising chalcopyrite–pyrrhotite–pyrite stringers associated with pervasive chlorite alteration, which occurs mostly at the sulfide lens margins. Petrographic observations of preserved primary, zone refining, and metamorphic textures in combination with in situ geochemistry show that the pyrite–sphalerite assemblage formed at lower temperatures (< 270 °C) than the other two mineral assemblages (~ 270–350 °C), and that mineral chemistry in all mineral assemblages was affected by greenschist facies metamorphism, although the effects are limited to recrystallization, small-scale remobilization (< 1 m) and trace element redistribution.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-05DOI: 10.1007/s00126-023-01219-2
Louise Lenoir, Thomas Blaise, Diana Chourio-Camacho, Antonin Richard, Alexandre Tarantola, Pierre Agrinier, Thomas Rigaudier, Gaël Monvoisin, Gérard Bardoux, Benjamin Brigaud, Jocelyn Barbarand
We provide new constraints for the fluid flow system at the origin of two F-Ba deposits located at the unconformity between the south of the Paris Basin and the northern edge of the French Massif Central. We used microthermometry and bulk crush-leach analyses to determine isotope ratios of mineralizing fluids (δ18O, δD, δ37Cl), together with cation and anion composition of fluid inclusions hosted by fluorite. Chlorinity and Cl/Br molar ratios (212–521) indicate the involvement of a brine, whose origin likely corresponds to Triassic evaporated seawater compatible with supratidal dolomitic facies preserved nearby. Microthermometry reveals high Ca/Na ratios, suggesting that the brine composition evolved from hydrothermal alteration of the Variscan basement and partial dissolution and replacement of the host sedimentary rocks. δ37Cl values are lower than the expected value of evaporated seawater, suggesting Cl isotope fractionation by ion filtration in clay-rich horizons. Fluorite crystallized at minimum temperatures of 70 to 110 °C, 10–40 °C warmer than the host Triassic sedimentary rocks. Ascending brines were expelled during the Early Cretaceous and experienced a drop in pressure and temperature, together with possible mixing with the SO4-rich pore water of the sedimentary rocks, causing precipitation of silica, followed by fluorite and barite, forming a stratabound deposit similar to those found in many areas in Western Europe.
{"title":"The origin of fluorite-barite mineralization at the interface between the Paris Basin and its Variscan basement: insights from fluid inclusion chemistry and isotopic (O, H, Cl) composition","authors":"Louise Lenoir, Thomas Blaise, Diana Chourio-Camacho, Antonin Richard, Alexandre Tarantola, Pierre Agrinier, Thomas Rigaudier, Gaël Monvoisin, Gérard Bardoux, Benjamin Brigaud, Jocelyn Barbarand","doi":"10.1007/s00126-023-01219-2","DOIUrl":"https://doi.org/10.1007/s00126-023-01219-2","url":null,"abstract":"<p>We provide new constraints for the fluid flow system at the origin of two F-Ba deposits located at the unconformity between the south of the Paris Basin and the northern edge of the French Massif Central. We used microthermometry and bulk crush-leach analyses to determine isotope ratios of mineralizing fluids (δ<sup>18</sup>O, δD, δ<sup>37</sup>Cl), together with cation and anion composition of fluid inclusions hosted by fluorite. Chlorinity and Cl/Br molar ratios (212–521) indicate the involvement of a brine, whose origin likely corresponds to Triassic evaporated seawater compatible with supratidal dolomitic facies preserved nearby. Microthermometry reveals high Ca/Na ratios, suggesting that the brine composition evolved from hydrothermal alteration of the Variscan basement and partial dissolution and replacement of the host sedimentary rocks. δ<sup>37</sup>Cl values are lower than the expected value of evaporated seawater, suggesting Cl isotope fractionation by ion filtration in clay-rich horizons. Fluorite crystallized at minimum temperatures of 70 to 110 °C, 10–40 °C warmer than the host Triassic sedimentary rocks. Ascending brines were expelled during the Early Cretaceous and experienced a drop in pressure and temperature, together with possible mixing with the SO<sub>4</sub>-rich pore water of the sedimentary rocks, causing precipitation of silica, followed by fluorite and barite, forming a stratabound deposit similar to those found in many areas in Western Europe.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-05DOI: 10.1007/s00126-023-01206-7
Brendan C. Hoare, Sarah E. Arden, Gary J. O’Sullivan
The direct dating of gem-quality garnet mineralization has been extremely limited, even though it has been known for decades that garnet may be dated by the U–Pb method. Here, we demonstrate the application of in situ laser U–Pb geochronology on gem-quality tsavorite to determine the timing of mineralization from two localities in the Mozambique Belt, Tanzania.
U–Pb dating of tsavorite from Merelani and Umba provides ages of 569.5 ± 6.8 Ma and 540.0 ± 5.8 Ma, respectively. Due to the high closure temperature of the U–Pb system in garnet, we argue that these ages correspond to tsavorite mineralization. These ages postdate the East African Orogeny (650–620 Ma), the most significant metamorphic episode recorded in the Mozambique Belt, which had been previously considered to be the main tsavorite mineralization event. Instead, these dates correspond to the later Kuungan orogenic episode (570–530 Ma), associated with the final amalgamation of Gondwana. The mineralization of tsavorite tens of millions of years after the East African Orogeny in the Mozambique Belt illustrates the benefits of direct dating of gem-quality garnet to determine mineralization timing and style.
{"title":"U–Pb dating of gem-quality vanadium-bearing grossular garnet (var. tsavorite) from north-eastern Tanzania","authors":"Brendan C. Hoare, Sarah E. Arden, Gary J. O’Sullivan","doi":"10.1007/s00126-023-01206-7","DOIUrl":"https://doi.org/10.1007/s00126-023-01206-7","url":null,"abstract":"<p>The direct dating of gem-quality garnet mineralization has been extremely limited, even though it has been known for decades that garnet may be dated by the U–Pb method. Here, we demonstrate the application of in situ laser U–Pb geochronology on gem-quality tsavorite to determine the timing of mineralization from two localities in the Mozambique Belt, Tanzania.</p><p>U–Pb dating of tsavorite from Merelani and Umba provides ages of 569.5 ± 6.8 Ma and 540.0 ± 5.8 Ma, respectively. Due to the high closure temperature of the U–Pb system in garnet, we argue that these ages correspond to tsavorite mineralization. These ages postdate the East African Orogeny (650–620 Ma), the most significant metamorphic episode recorded in the Mozambique Belt, which had been previously considered to be the main tsavorite mineralization event. Instead, these dates correspond to the later Kuungan orogenic episode (570–530 Ma), associated with the final amalgamation of Gondwana. The mineralization of tsavorite tens of millions of years after the East African Orogeny in the Mozambique Belt illustrates the benefits of direct dating of gem-quality garnet to determine mineralization timing and style.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-30DOI: 10.1007/s00126-023-01214-7
Hélène Legros, Janina Czas, Yan Luo, Sarah Woodland, Chiranjeeb Sarkar, Steven B. Shirey, Dan Schulze, D. Graham Pearson
Mantle xenoliths in a Mesoproterozoic lamprophyre dyke at Elliot Lake, Ontario, located on the east margin of the Midcontinent Rift (MCR), erupted at ~ 1.1 Ga. These xenoliths enable a study of critical metal enrichment in the sub-cratonic lithospheric mantle (SCLM). Whole-rock major and trace element data from a suite of peridotite xenoliths document a combination of melt depletion and cryptic metasomatic processes. Trace element whole-rock and mineral systematics show a specific endowment in Nb-U-REE (ca. 5–30 ppm mean value), linked to carbonated silicate metasomatism. Geochronological data from the lamprophyre host (Rb–Sr age of 1112.8 ± 4.95 Ma) and the mantle xenoliths (Re-Os) indicate that our samples document the state of the mantle during the earlier stages of magmatism of the MCR. Mineral thermobarometry reveals a hot geotherm reflecting the thinning of the Superior cratonic root to 110 km. Most of the Nb-U-REE deposits and anomalies associated with the MCR event are located around Lake Superior. Here we document for the first time north of Lake Huron, metasomatic processes in the lithosphere that may have created Nb-U-REE metal endowment. The mantle events documented here relate to other observations made in the Slave and North China craton and show how silico-carbonated mid-lithospheric metasomatism up-grades the cratonic lithospheric mantle into a fertile source. Comparison with other small degree melts such as kimberlites, and mantle metasomes related to the MARID suite, show that small degree melts are very efficient at transporting critical metals from the HFSE group plus U and Th, into Earth’s lithosphere.
{"title":"Post-Archean Nb-REE-U enrichment in the Superior craton recorded in metasomatised mantle rocks erupted in the 1.1 Ga Midcontinental Rift event","authors":"Hélène Legros, Janina Czas, Yan Luo, Sarah Woodland, Chiranjeeb Sarkar, Steven B. Shirey, Dan Schulze, D. Graham Pearson","doi":"10.1007/s00126-023-01214-7","DOIUrl":"https://doi.org/10.1007/s00126-023-01214-7","url":null,"abstract":"<p>Mantle xenoliths in a Mesoproterozoic lamprophyre dyke at Elliot Lake, Ontario, located on the east margin of the Midcontinent Rift (MCR), erupted at ~ 1.1 Ga. These xenoliths enable a study of critical metal enrichment in the sub-cratonic lithospheric mantle (SCLM). Whole-rock major and trace element data from a suite of peridotite xenoliths document a combination of melt depletion and cryptic metasomatic processes. Trace element whole-rock and mineral systematics show a specific endowment in Nb-U-REE (ca. 5–30 ppm mean value), linked to carbonated silicate metasomatism. Geochronological data from the lamprophyre host (Rb–Sr age of 1112.8 ± 4.95 Ma) and the mantle xenoliths (Re-Os) indicate that our samples document the state of the mantle during the earlier stages of magmatism of the MCR. Mineral thermobarometry reveals a hot geotherm reflecting the thinning of the Superior cratonic root to 110 km. Most of the Nb-U-REE deposits and anomalies associated with the MCR event are located around Lake Superior. Here we document for the first time north of Lake Huron, metasomatic processes in the lithosphere that may have created Nb-U-REE metal endowment. The mantle events documented here relate to other observations made in the Slave and North China craton and show how silico-carbonated mid-lithospheric metasomatism up-grades the cratonic lithospheric mantle into a fertile source<i>.</i> Comparison with other small degree melts such as kimberlites, and mantle metasomes related to the MARID suite, show that small degree melts are very efficient at transporting critical metals from the HFSE group plus U and Th, into Earth’s lithosphere.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-28DOI: 10.1007/s00126-023-01213-8
Matthew J. Manor, Stephen J. Piercey, Corey J. Wall
Magmatism is a critical component in sustaining hydrothermal convection and metal transport during the formation of volcanogenic massive sulfide (VMS) deposits. Previous studies of magmatic petrogenesis in VMS systems have demonstrated that ore-related volcanic rocks have distinct whole-rock geochemical and isotopic signatures (i.e., high HFSE, REE, Th, εHf-Nd, zircon saturation T) relative to barren volcanic rocks, which supports models of elevated crustal heat flow during periods of ore deposition; however, the petrologic characteristics and intrinsic parameters (e.g., T, fO2) related to these magmatic events in VMS districts remain poorly understood. Arc–back-arc assemblages from the mid-Paleozoic Yukon-Tanana terrane are well-characterized and include the Finlayson Lake VMS district, which is host to several felsic-hosted deposits (e.g., Kudz Ze Kayah, GP4F, Wolverine) that were generated in a peri-Laurentian continental back-arc tectonic setting. In this study, zircon from back-arc and coeval arc rocks in the Yukon-Tanana terrane was used as a proxy for primary magma formation conditions that generated VMS-proximal and VMS-distal stratigraphy. Our results indicate that zircon grains in VMS-proximal environments have unique textural, geochemical, and isotopic characteristics (e.g., low-aspect ratios, greater abundance of zircon-phosphate intergrowths, Th/U > 1, Zr/Hf > 80, Tzrc > 780 °C, εHfi > –7) that are clearly distinguished from zircon in VMS-distal rocks in both the back-arc and arc settings (Th/U < 1, Zr/Hf < 80, Tzrc < 780 °C, εHfi < –7). These signatures correlate to VMS-proximal magmas that were hotter, less fractionated, and contained greater juvenile melt contributions compared to VMS-distal magmas and reflect a series of high-flux magmatic events that directly correspond to the early tectonic development of Yukon-Tanana terrane. Moreover, this study underscores the importance of mineral-scale petrology, geochemistry, and geochronology in defining the primary magmatic conditions that generated VMS-related felsic rocks and highlights the utility of zircon as a prospectivity tool in both grassroots and brownfields VMS exploration.
{"title":"Zircon and the role of magmatic petrogenesis in the formation of felsic-hosted volcanogenic massive sulfide (VMS) deposits: a case study from the mid-Paleozoic Yukon-Tanana terrane, northern Canadian Cordillera","authors":"Matthew J. Manor, Stephen J. Piercey, Corey J. Wall","doi":"10.1007/s00126-023-01213-8","DOIUrl":"https://doi.org/10.1007/s00126-023-01213-8","url":null,"abstract":"<p>Magmatism is a critical component in sustaining hydrothermal convection and metal transport during the formation of volcanogenic massive sulfide (VMS) deposits. Previous studies of magmatic petrogenesis in VMS systems have demonstrated that ore-related volcanic rocks have distinct whole-rock geochemical and isotopic signatures (i.e., high HFSE, REE, Th, εHf-Nd, zircon saturation T) relative to barren volcanic rocks, which supports models of elevated crustal heat flow during periods of ore deposition; however, the petrologic characteristics and intrinsic parameters (e.g., T, <i>f</i>O<sub>2</sub>) related to these magmatic events in VMS districts remain poorly understood. Arc–back-arc assemblages from the mid-Paleozoic Yukon-Tanana terrane are well-characterized and include the Finlayson Lake VMS district, which is host to several felsic-hosted deposits (e.g., Kudz Ze Kayah, GP4F, Wolverine) that were generated in a peri-Laurentian continental back-arc tectonic setting. In this study, zircon from back-arc and coeval arc rocks in the Yukon-Tanana terrane was used as a proxy for primary magma formation conditions that generated VMS-proximal and VMS-distal stratigraphy. Our results indicate that zircon grains in VMS-proximal environments have unique textural, geochemical, and isotopic characteristics (e.g., low-aspect ratios, greater abundance of zircon-phosphate intergrowths, Th/U > 1, Zr/Hf > 80, <i>T</i><sub>zrc</sub> > 780 °C, εHf<sub>i</sub> > –7) that are clearly distinguished from zircon in VMS-distal rocks in both the back-arc and arc settings (Th/U < 1, Zr/Hf < 80, <i>T</i><sub>zrc</sub> < 780 °C, εHf<sub>i</sub> < –7). These signatures correlate to VMS-proximal magmas that were hotter, less fractionated, and contained greater juvenile melt contributions compared to VMS-distal magmas and reflect a series of high-flux magmatic events that directly correspond to the early tectonic development of Yukon-Tanana terrane. Moreover, this study underscores the importance of mineral-scale petrology, geochemistry, and geochronology in defining the primary magmatic conditions that generated VMS-related felsic rocks and highlights the utility of zircon as a prospectivity tool in both grassroots and brownfields VMS exploration.</p>","PeriodicalId":18682,"journal":{"name":"Mineralium Deposita","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49696744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}