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Haixia Chu - One of the best experts on this subject based on the ideXlab platform.
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Petrography, Fluid Inclusion analysis, and geochronology of the End uranium deposit, Kiggavik, Nunavut, Canada
Mineralium Deposita, 2017Co-Authors: Guoxiang Chi, Taylor Haid, David Quirt, Mostafa Fayek, Nigel Blamey, Haixia ChuAbstract:The End deposit is one of several uranium deposits in the Kiggavik area near the Proterozoic Thelon Basin, which is geologically similar to the Athabasca Basin known for its unconformity-related uranium deposits. The mineralization occurs as uraninite and coffinite in quartz veins and wall rocks (psammopelitic gneisses) in the sub-Thelon basement and is associated with clay- and hematite-altered fault zones. Fluid Inclusions were studied in quartz cementing unmineralized breccias formed before mineralization (Q2), quartz veins that were formed before mineralization but spatially associated with uranite (Q4), and calcite veins that were formed after mineralization. Four types of Fluid Inclusions were recognized, namely liquid-dominated biphase (liquid + vapor), vapor-dominated biphase (vapor + liquid), monophase (vapor-only), and triphase (liquid + vapor + halite) Inclusions. The first three types were found in Q2, whereas all four types were found in Q4 and calcite. The coexistence of these different types of Inclusions within individual Fluid Inclusion assemblages is interpreted to indicate Fluid immiscibility and heterogeneous trapping. Based on microthermometry, the Fluids associated with Q2 are characterized by low salinities (0.4 to 6.6 wt%) and moderate temperatures from 148 to 261 °C, and the Fluids associated with calcite show high salinities (26.8 to 29.3 wt%) and relatively low temperatures from 146 to 205 °C, whereas the Fluids associated with Q4 have a wide range of salinities from 0.7 to 38.8 wt% and temperatures from 80 to 332 °C. Microthermometric and cryogenic Raman spectroscopic studies indicate that the high-salinity Fluids in Q4 and calcite belong to the H_2O-NaCl-CaCl_2 ± MgCl_2 system, with some dominated by NaCl and others by CaCl_2. The Fluid Inclusions in Q2 are interpreted to be unrelated to mineralization, whereas those in Q4 and calcite reflect the mineralizing Fluids. The Fluid Inclusion data are consistent with a genetic link of mineralization with basinal brines derived from the Thelon Basin. However, unlike the conventional deep-burial (>5 km) diagenetic-hydrothermal model proposed for the unconformity-related uranium deposits, the uranium mineralization in the End deposit is inferred to have formed in a shallow environment (probably
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petrography Fluid Inclusion analysis and geochronology of the end uranium deposit kiggavik nunavut canada
Mineralium Deposita, 2017Co-Authors: Guoxiang Chi, Nigel J F Blamey, Taylor Haid, David Quirt, Mostafa Fayek, Haixia ChuAbstract:The End deposit is one of several uranium deposits in the Kiggavik area near the Proterozoic Thelon Basin, which is geologically similar to the Athabasca Basin known for its unconformity-related uranium deposits. The mineralization occurs as uraninite and coffinite in quartz veins and wall rocks (psammopelitic gneisses) in the sub-Thelon basement and is associated with clay- and hematite-altered fault zones. Fluid Inclusions were studied in quartz cementing unmineralized breccias formed before mineralization (Q2), quartz veins that were formed before mineralization but spatially associated with uranite (Q4), and calcite veins that were formed after mineralization. Four types of Fluid Inclusions were recognized, namely liquid-dominated biphase (liquid + vapor), vapor-dominated biphase (vapor + liquid), monophase (vapor-only), and triphase (liquid + vapor + halite) Inclusions. The first three types were found in Q2, whereas all four types were found in Q4 and calcite. The coexistence of these different types of Inclusions within individual Fluid Inclusion assemblages is interpreted to indicate Fluid immiscibility and heterogeneous trapping. Based on microthermometry, the Fluids associated with Q2 are characterized by low salinities (0.4 to 6.6 wt%) and moderate temperatures from 148 to 261 °C, and the Fluids associated with calcite show high salinities (26.8 to 29.3 wt%) and relatively low temperatures from 146 to 205 °C, whereas the Fluids associated with Q4 have a wide range of salinities from 0.7 to 38.8 wt% and temperatures from 80 to 332 °C. Microthermometric and cryogenic Raman spectroscopic studies indicate that the high-salinity Fluids in Q4 and calcite belong to the H2O-NaCl-CaCl2 ± MgCl2 system, with some dominated by NaCl and others by CaCl2. The Fluid Inclusions in Q2 are interpreted to be unrelated to mineralization, whereas those in Q4 and calcite reflect the mineralizing Fluids. The Fluid Inclusion data are consistent with a genetic link of mineralization with basinal brines derived from the Thelon Basin. However, unlike the conventional deep-burial (>5 km) diagenetic-hydrothermal model proposed for the unconformity-related uranium deposits, the uranium mineralization in the End deposit is inferred to have formed in a shallow environment (probably <2 km), based on Fluid immiscibility and low Fluid pressures obtained in this study. The U-Pb age of uraninite (1295 ± 12 Ma) is interpreted to reflect isotopic resetting after the primary mineralization.
Chengbiao Leng - One of the best experts on this subject based on the ideXlab platform.
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metal source and wolframite precipitation process at the xihuashan tungsten deposit south china insights from mineralogy Fluid Inclusion and stable isotope
Ore Geology Reviews, 2019Co-Authors: Jiehua Yang, Chengbiao Leng, Jiantang PengAbstract:Abstract The Xihuashan tungsten deposit, hosted in the late Jurassic granitic pluton in the Nanling Range of South China, has a total resource of about 81,300 tonnes of WO 3 with an average ore grade of 1.08% WO 3 . Wolframite is the dominant ore mineral and intergrown with quartz in the main mineralization stage. Ore-forming Fluids trapped in wolframite have δD and δ 18 O values from -82‰ to -64‰ and 7.4‰ to 8.8‰, respectively. Those in quartz have similar δD (-72‰ to -58‰) and δ 18 O (6.8‰ to 8.0‰) values, indicative of a magmatic Fluids simultaneously trapped by quartz and wolframite. LA-ICP-MS analyses for individual Fluid Inclusion show that this mineralizing Fluid contains measurable Li, Rb, Cs, K, Na, Ti, Cu, Zn, As and W (1 to 125 ppm with average of 19 ppm) while depleted in Fe and Mn. The wolframite from the Xihuashan tungsten deposit contains high FeO (10.9 to 17.7 wt. %) and MnO (5.9 to 12.7 wt. %) contents with Fe/(Fe+Mn) atomic ratio of 0.46 to 0.75, thus requires the availability of external Fe and Mn. We detect that the Fe and Mn contents in mica from the greisen are remarkably lower than primary mica from granite. Some magmatic micas were observed in greisen and were subjected to hydrothermal alteration. Compared to the core, the rim of these micas depleted in Fe, Mn, F, and Na. The siderite and pyrophanite are formed along cleavage planes of altered magmatic mica that are evidence to be due to Fe and Mn release during granite alteration. Thus, we demonstrate quantitatively that magmatic Fluids at Xihuashan provide W in solution, whereas the hosted granite alteration contributes Fe and Mn to precipitate wolframite. It is also supported by wolframites have trace and rare earth elements characteristics similar to those of granite and some characteristics similar to the greisen. Therefore, the ore-forming Fluids has components derived from the last highly evolved residual granitic melt and components acquired by releasing through the hosted granite alteration. Fluid-rock interaction exert a principle control on wolframite precipitation. Based on mineralogy, Fluid Inclusion and stable isotope, we proposed three-stage process to illustrate the genetical link between tungsten mineralization and granite.
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ore geology Fluid Inclusion and isotope geochemistry of the xunyang hg sb orefield qinling orogen central china
Geological Journal, 2014Co-Authors: Ying Zhang, Chengbiao Leng, Haoshu Tang, Yanjing Chen, Chenghai ZhaoAbstract:The Xunyang Hg–Sb orefield, Shaanxi Province, containing two large (Gongguan and Qingtonggou) and tens of small to medium Hg–Sb deposits, is located in the southern Qinling Orogen. Ore bodies of the deposits are hosted in Devonian dolomite and controlled by a fault system. Ores are mainly present as massive veins, disseminations, breccias and fine veinlets, with cinnabar (Hg) and stibnite (Sb) being the dominant ore minerals. Gangue minerals include quartz, calcite and dolomite. Hydrothermal minerals (quartz and calcite) only contain aqueous Fluid Inclusions with low homogenization temperature (135–274 °C) and salinity (1.23–12.3 wt.% NaCl equiv.), supporting an epizonogenic hydrothermal origin. The carbon, oxygen and hydrogen isotope data indicate that the ore-forming Fluids were mainly sourced from epizonogenic to metamorphic devolatilization of the Sinian−Triassic strata that possibly underthrusted beneath the orefield, with inflow of the circulating meteoric water. Sulphur isotope ratios of stibnite and cinnabar range from 2‰ to 12‰, suggesting a contribution from sedimentary sulphate or sulphate-bearing Fluids potted in strata, which is coincident with the δ34S values (3.4–8.6‰) of diagenetic pyrite in the strata. The conclusion drawn from sulphur isotopes is fully supported by the Pb isotope signatures. In addition, the 87Sr/86Sr ratios gradationally increase from ore-hosting dolostones, through ore-barren calcite or low-grade ores, to high-grade ores, indicating that a portion of the Fluids originated from a source with higher 87Sr/86Sr values than the host-rocks, which is possibly composed of the Neoproterozoic−Lower Palaeozoic basement of the Xunyang Basin. Integrating the data from ore geology, Fluid Inclusion microthermometry and stable, radioactive isotope geochemistry, it can be concluded that the deposits in the Xunyang Hg–Sb orefield were formed by epizonogenic hydrothermal Fluids mainly sourced from the strata via structural deformation during the North China−Yangtze continental collision. Copyright © 2014 John Wiley & Sons, Ltd.
Guoxiang Chi - One of the best experts on this subject based on the ideXlab platform.
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petrography Fluid Inclusion analysis and geochronology of the end uranium deposit kiggavik nunavut canada
Mineralium Deposita, 2017Co-Authors: Guoxiang Chi, Nigel J F Blamey, Taylor Haid, David Quirt, Mostafa Fayek, Haixia ChuAbstract:The End deposit is one of several uranium deposits in the Kiggavik area near the Proterozoic Thelon Basin, which is geologically similar to the Athabasca Basin known for its unconformity-related uranium deposits. The mineralization occurs as uraninite and coffinite in quartz veins and wall rocks (psammopelitic gneisses) in the sub-Thelon basement and is associated with clay- and hematite-altered fault zones. Fluid Inclusions were studied in quartz cementing unmineralized breccias formed before mineralization (Q2), quartz veins that were formed before mineralization but spatially associated with uranite (Q4), and calcite veins that were formed after mineralization. Four types of Fluid Inclusions were recognized, namely liquid-dominated biphase (liquid + vapor), vapor-dominated biphase (vapor + liquid), monophase (vapor-only), and triphase (liquid + vapor + halite) Inclusions. The first three types were found in Q2, whereas all four types were found in Q4 and calcite. The coexistence of these different types of Inclusions within individual Fluid Inclusion assemblages is interpreted to indicate Fluid immiscibility and heterogeneous trapping. Based on microthermometry, the Fluids associated with Q2 are characterized by low salinities (0.4 to 6.6 wt%) and moderate temperatures from 148 to 261 °C, and the Fluids associated with calcite show high salinities (26.8 to 29.3 wt%) and relatively low temperatures from 146 to 205 °C, whereas the Fluids associated with Q4 have a wide range of salinities from 0.7 to 38.8 wt% and temperatures from 80 to 332 °C. Microthermometric and cryogenic Raman spectroscopic studies indicate that the high-salinity Fluids in Q4 and calcite belong to the H2O-NaCl-CaCl2 ± MgCl2 system, with some dominated by NaCl and others by CaCl2. The Fluid Inclusions in Q2 are interpreted to be unrelated to mineralization, whereas those in Q4 and calcite reflect the mineralizing Fluids. The Fluid Inclusion data are consistent with a genetic link of mineralization with basinal brines derived from the Thelon Basin. However, unlike the conventional deep-burial (>5 km) diagenetic-hydrothermal model proposed for the unconformity-related uranium deposits, the uranium mineralization in the End deposit is inferred to have formed in a shallow environment (probably <2 km), based on Fluid immiscibility and low Fluid pressures obtained in this study. The U-Pb age of uraninite (1295 ± 12 Ma) is interpreted to reflect isotopic resetting after the primary mineralization.
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Petrography, Fluid Inclusion analysis, and geochronology of the End uranium deposit, Kiggavik, Nunavut, Canada
Mineralium Deposita, 2017Co-Authors: Guoxiang Chi, Taylor Haid, David Quirt, Mostafa Fayek, Nigel Blamey, Haixia ChuAbstract:The End deposit is one of several uranium deposits in the Kiggavik area near the Proterozoic Thelon Basin, which is geologically similar to the Athabasca Basin known for its unconformity-related uranium deposits. The mineralization occurs as uraninite and coffinite in quartz veins and wall rocks (psammopelitic gneisses) in the sub-Thelon basement and is associated with clay- and hematite-altered fault zones. Fluid Inclusions were studied in quartz cementing unmineralized breccias formed before mineralization (Q2), quartz veins that were formed before mineralization but spatially associated with uranite (Q4), and calcite veins that were formed after mineralization. Four types of Fluid Inclusions were recognized, namely liquid-dominated biphase (liquid + vapor), vapor-dominated biphase (vapor + liquid), monophase (vapor-only), and triphase (liquid + vapor + halite) Inclusions. The first three types were found in Q2, whereas all four types were found in Q4 and calcite. The coexistence of these different types of Inclusions within individual Fluid Inclusion assemblages is interpreted to indicate Fluid immiscibility and heterogeneous trapping. Based on microthermometry, the Fluids associated with Q2 are characterized by low salinities (0.4 to 6.6 wt%) and moderate temperatures from 148 to 261 °C, and the Fluids associated with calcite show high salinities (26.8 to 29.3 wt%) and relatively low temperatures from 146 to 205 °C, whereas the Fluids associated with Q4 have a wide range of salinities from 0.7 to 38.8 wt% and temperatures from 80 to 332 °C. Microthermometric and cryogenic Raman spectroscopic studies indicate that the high-salinity Fluids in Q4 and calcite belong to the H_2O-NaCl-CaCl_2 ± MgCl_2 system, with some dominated by NaCl and others by CaCl_2. The Fluid Inclusions in Q2 are interpreted to be unrelated to mineralization, whereas those in Q4 and calcite reflect the mineralizing Fluids. The Fluid Inclusion data are consistent with a genetic link of mineralization with basinal brines derived from the Thelon Basin. However, unlike the conventional deep-burial (>5 km) diagenetic-hydrothermal model proposed for the unconformity-related uranium deposits, the uranium mineralization in the End deposit is inferred to have formed in a shallow environment (probably
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An overview on current Fluid-Inclusion research and applications
Acta Petrologica Sinica, 2003Co-Authors: Guoxiang Chi, I.-ming ChouAbstract:This paper provides an overview of some of the more important developments in Fluid-Inclusion research and applications in recent years, including Fluid-Inclusion petrography, PVTX studies, and analytical techniques. In Fluid-Inclusion petrography, the introduction of the concept of 'Fluid-Inclusion assemblage' has been a major advance. In PVTX studies, the use of synthetic Fluid Inclusions and hydrothermal diamond-anvil cells has greatly contributed to the characterization of the phase behaviour of geologically relevant Fluid systems. Various analytical methods are being developed and refined rapidly, with the Laser-Raman and LA-ICP-MS techniques being particularly useful for volatile and solute analyses, respectively. Ore deposit research has been and will continue to be the main field of application of Fluid Inclusions. However, Fluid Inclusions have been increasingly applied to other fields of earth science, especially in petroleum geology and the study of magmatic and earth interior processes.
Junxing Zhao - One of the best experts on this subject based on the ideXlab platform.
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porphyry to epithermal transition at the rongna cu au deposit tibet insights from h o isotopes and Fluid Inclusion analysis
Ore Geology Reviews, 2020Co-Authors: Bernd Lehmann, Xianan Zhang, Kezhang Qin, Junxing ZhaoAbstract:Abstract The giant Rongna Cu-(Au) deposit is a recently discovered low-grade composite porphyry-high sulfidation epithermal system in the Duolong ore district of central Tibet. We present Fluid Inclusion petrography, microthermometry, stable isotope (H, O), and Fluid-compositional data (LA-ICP-MS) to constrain the Fluid evolution of the Rongna deposit. Hydrothermal quartz and muscovite formed in the porphyry stage yielded Fluid values of 8.2 ± 1.0‰ δ18OH2O, and −75 ± 19‰ δDH2O (n = 13). Pyrophyllite, kaolinite, and dickite define the isotopic composition of the epithermal Fluid (δ18OH2O = 2.2–8.3‰, δDH2O = −87 ~ −45‰). This epithermal Fluid of lighter oxygen isotope and heavier hydrogen isotope composition still has a magmatic-hydrothermal signature and rules out any significant involvement of meteoric water. The very high concentration of Cu in Fluid Inclusions from epithermal veins and the common sulfide replacement features suggest that the epithermal mineralization may be partially related with the dissolution and re-precipitation of the porphyry-stage sulfides. Combined with Fluid Inclusion petrography and microthermometric data, it is indicated that a single-phase Fluid exsolved from magma at depth and underwent boiling and cooling, forming the porphyry alteration and mineralization. With decrease of temperature and pressure, the ascending vapor contracted into acid aqueous Fluid, leaching downward to develop the telescoped high-sulfidation epithermal alteration and mineralization.
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Fluid Inclusion and stable isotope constraints on ore genesis of the zajkan epithermal base metal deposit tarom hashtjin metallogenic belt nw iran
Ore Geology Reviews, 2019Co-Authors: Hossein Kouhestani, Kezhang Qin, Mir Ali Asghar Mokhtari, Junxing ZhaoAbstract:In the Zajkan Pb-Zn-Cu (Au-Ag) deposit of the Tarom-Hashtjin metallogenic belt (THMB), northwest Iran, mineralization occurs as quartz-base metal sulfide veins hosted by Eocene volcanic and volcaniclastic rocks of the Karaj Formation. Four stages of ore formation are identified at Zajkan: (1) quartz-chalcopyrite-pyrite veins, (2) quartz-galena-sphalerite +/- chalcopyrite +/- pyrite veins and breccias, (3) quartz-hematite veins and breccias, and (4) barren quartz-carbonate veinlets. The primary metallic minerals are pyrite, chalcopyrite, sphalerite, galena, and trace amounts of hematite; gangue minerals are mainly quartz, sericite, chlorite, and calcite. The main wall-rock alteration is silicification, and intermediate argillic, and propylitic alteration. The coexistence of different types of Fluid Inclusions (LV, VL, and V) in individual Fluid Inclusion assemblages in quartz and sphalerite suggests boiling and heterogeneous trapping. Excluding the heterogeneously entrapped Fluid Inclusions, the microthermometric measurements of primary LV Fluid Inclusion assemblages in quartz and sphalerite indicate that the veins were formed at temperatures between 217 and 273 degrees C from Fluids with salinities between 1.7 and 6.4 wt% NaCl equiv. The oxygen isotopic compositions (delta O-18(water-VSMOW) of +3.7 to +1.1 parts per thousand) indicate that the ore-forming Fluids were mainly derived from magmatic water with the input of meteoric water in the later ore-stages. Sulfur isotopic values of sulfide minerals vary over a narrow range from -5.0 to -0.9 parts per thousand(VCDT) (averaging -2.2 parts per thousand(VCDT)), suggesting that sulfur was derived from a homogeneous magmatic source. The Fluid Inclusion and stable isotope data indicate that Fluid boiling and mixing facilitated hydrothermal alteration and mineralization at Zajkan. Our data suggest that the Zajkan deposit is an intermediate-sulficiation style epithermal mineralization. The estimated ore formation depth of Zajkan indicates minor denudation in the region and may imply a great prospecting potential for other epithermal mineralization in the THMB.
David Quirt - One of the best experts on this subject based on the ideXlab platform.
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Petrography, Fluid Inclusion analysis, and geochronology of the End uranium deposit, Kiggavik, Nunavut, Canada
Mineralium Deposita, 2017Co-Authors: Guoxiang Chi, Taylor Haid, David Quirt, Mostafa Fayek, Nigel Blamey, Haixia ChuAbstract:The End deposit is one of several uranium deposits in the Kiggavik area near the Proterozoic Thelon Basin, which is geologically similar to the Athabasca Basin known for its unconformity-related uranium deposits. The mineralization occurs as uraninite and coffinite in quartz veins and wall rocks (psammopelitic gneisses) in the sub-Thelon basement and is associated with clay- and hematite-altered fault zones. Fluid Inclusions were studied in quartz cementing unmineralized breccias formed before mineralization (Q2), quartz veins that were formed before mineralization but spatially associated with uranite (Q4), and calcite veins that were formed after mineralization. Four types of Fluid Inclusions were recognized, namely liquid-dominated biphase (liquid + vapor), vapor-dominated biphase (vapor + liquid), monophase (vapor-only), and triphase (liquid + vapor + halite) Inclusions. The first three types were found in Q2, whereas all four types were found in Q4 and calcite. The coexistence of these different types of Inclusions within individual Fluid Inclusion assemblages is interpreted to indicate Fluid immiscibility and heterogeneous trapping. Based on microthermometry, the Fluids associated with Q2 are characterized by low salinities (0.4 to 6.6 wt%) and moderate temperatures from 148 to 261 °C, and the Fluids associated with calcite show high salinities (26.8 to 29.3 wt%) and relatively low temperatures from 146 to 205 °C, whereas the Fluids associated with Q4 have a wide range of salinities from 0.7 to 38.8 wt% and temperatures from 80 to 332 °C. Microthermometric and cryogenic Raman spectroscopic studies indicate that the high-salinity Fluids in Q4 and calcite belong to the H_2O-NaCl-CaCl_2 ± MgCl_2 system, with some dominated by NaCl and others by CaCl_2. The Fluid Inclusions in Q2 are interpreted to be unrelated to mineralization, whereas those in Q4 and calcite reflect the mineralizing Fluids. The Fluid Inclusion data are consistent with a genetic link of mineralization with basinal brines derived from the Thelon Basin. However, unlike the conventional deep-burial (>5 km) diagenetic-hydrothermal model proposed for the unconformity-related uranium deposits, the uranium mineralization in the End deposit is inferred to have formed in a shallow environment (probably
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petrography Fluid Inclusion analysis and geochronology of the end uranium deposit kiggavik nunavut canada
Mineralium Deposita, 2017Co-Authors: Guoxiang Chi, Nigel J F Blamey, Taylor Haid, David Quirt, Mostafa Fayek, Haixia ChuAbstract:The End deposit is one of several uranium deposits in the Kiggavik area near the Proterozoic Thelon Basin, which is geologically similar to the Athabasca Basin known for its unconformity-related uranium deposits. The mineralization occurs as uraninite and coffinite in quartz veins and wall rocks (psammopelitic gneisses) in the sub-Thelon basement and is associated with clay- and hematite-altered fault zones. Fluid Inclusions were studied in quartz cementing unmineralized breccias formed before mineralization (Q2), quartz veins that were formed before mineralization but spatially associated with uranite (Q4), and calcite veins that were formed after mineralization. Four types of Fluid Inclusions were recognized, namely liquid-dominated biphase (liquid + vapor), vapor-dominated biphase (vapor + liquid), monophase (vapor-only), and triphase (liquid + vapor + halite) Inclusions. The first three types were found in Q2, whereas all four types were found in Q4 and calcite. The coexistence of these different types of Inclusions within individual Fluid Inclusion assemblages is interpreted to indicate Fluid immiscibility and heterogeneous trapping. Based on microthermometry, the Fluids associated with Q2 are characterized by low salinities (0.4 to 6.6 wt%) and moderate temperatures from 148 to 261 °C, and the Fluids associated with calcite show high salinities (26.8 to 29.3 wt%) and relatively low temperatures from 146 to 205 °C, whereas the Fluids associated with Q4 have a wide range of salinities from 0.7 to 38.8 wt% and temperatures from 80 to 332 °C. Microthermometric and cryogenic Raman spectroscopic studies indicate that the high-salinity Fluids in Q4 and calcite belong to the H2O-NaCl-CaCl2 ± MgCl2 system, with some dominated by NaCl and others by CaCl2. The Fluid Inclusions in Q2 are interpreted to be unrelated to mineralization, whereas those in Q4 and calcite reflect the mineralizing Fluids. The Fluid Inclusion data are consistent with a genetic link of mineralization with basinal brines derived from the Thelon Basin. However, unlike the conventional deep-burial (>5 km) diagenetic-hydrothermal model proposed for the unconformity-related uranium deposits, the uranium mineralization in the End deposit is inferred to have formed in a shallow environment (probably <2 km), based on Fluid immiscibility and low Fluid pressures obtained in this study. The U-Pb age of uraninite (1295 ± 12 Ma) is interpreted to reflect isotopic resetting after the primary mineralization.