Marta Sośnicka | CSIRO - Academia.edu (original) (raw)

Papers by Marta Sośnicka

Mineralogy and Petrology

Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in publishe... more Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Mineralium deposita, May 7, 2024

Mineralium Deposita

The origin, evolution, and interplay of brine and hydrocarbon fluid systems play a crucial role i... more The origin, evolution, and interplay of brine and hydrocarbon fluid systems play a crucial role in the formation of deep sediment-hosted base metal ore deposits. Here we investigate ratios of halogens, noble gases, stable C and S isotopes, and metal budgets of aqueous brines, which deposited deep-seated and near-surface hydrothermal Zn-Pb mineralization hosted by Zechstein carbonates in the Lower Saxony Basin (North German Basin), by studies of fluid inclusions in sphalerite and quartz. Major and trace element geochemistry and noble gas isotopic signatures of brine inclusions revealed that the ore-forming fluids were highly reactive and experienced prolonged interactions with host rocks in the constricted, over-pressured metal source regions and consequently evolved from near-neutral, oxidized brines towards more reduced, acidic high-salinity brines. Quartz-hosted halite-saturated fluid inclusions with Th <200°C contain Zn and Pb concentrations up to ca. 9400 μg g-1 and 5200 μg g...

Applied Earth Science, 2019

Journal of African Earth Sciences, Feb 1, 2023

Mineralogy and Petrology, 2021

The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted main... more The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted mainly in the organic matter-rich Albian and Cenomanian–Turonian rocks. The orebodies occur mainly as open-space fillings and are structurally-controlled. The paragenetic sequence consists of three stages, which reflect three ore events. Three discrete stages of Zn-Pb sulfide and/or Zn-Pb-Ba-Sr sulfide-sulfate ores are identified. Fluid inclusion study carried out on selected minerals of different stages reveals that sphalerite, galena, marcasite, celestine, barite, and fluorite precipitated as a result of mixing between a hydrothermal, saline, metal-rich basinal fluid and a low-temperature, less saline, metal-depleted, sulfur- or sulfate-rich fluid with the intermittent involvement of hydrocarbons. Based on sulfur isotope data, sulfur of sulfides was derived from the reduction of the dissolved Triassic sulfates primary through thermochemical sulfate reduction with a contribution of bacterial sulfate reduction. The Pb isotopic composition of galena samples and trace elements data of the host carbonate rocks suggest that metals were derived primarily from the Paleozoic siliciclastic rocks with a contribution of the organic matter-rich Albian and Cenomanian–Turonian rocks. The Alpine orogeny triggered the migration of the metalliferous fluids from the deep parts of the basin towards the peridiapiric paleohigh of Ech Chehid diapir through major faults towards the loci of deposition.

Mineralogy and Petrology, 2021

Jemmali et al. 2021

Mineralium Deposita, 2021

Stibnite was mined until the end of the twentieth century in the Schlaining ore district, Austria... more Stibnite was mined until the end of the twentieth century in the Schlaining ore district, Austria, near the easternmost border of the Eastern Alps where windows of Penninic ophiolites and metasediments are exposed below Austroalpine tectonic units. In Early Miocene, structurally controlled small vein and metasomatic stibnite-quartz deposits were formed in Penninic Mesozoic calcareous marbles and calcite schists. Fluid inclusion studies identified two fluids involved in the mineralization: (i) a low-salinity, low-CO2 metamorphic fluid that precipitated quartz at approximately 240 °C and (ii) a stibnite-forming ore fluid that had a meteoric origin. There is no evidence of boiling or that the fluids mixed during mineralization. The ore components Sb and H2S were leached by fluid/rock interaction from buried rock units. Stibnite mineralization occurred by cooling the ore fluid to below 300 °C, at less than 2000 m depth. Quartz precipitated at slightly lower temperatures, approximately c...

Nature Communications, 2021

C–O–H–N–S-bearing fluids are known as one of the most challenging geochemical systems due to scar... more C–O–H–N–S-bearing fluids are known as one of the most challenging geochemical systems due to scarcity of available experimental data. H2S-rich fluid systems were recognized in a wide array of world-class mineral deposits and hydrocarbon reservoirs. Here we report on a nature of low-temperature (T ≥ −192 °C) phase transitions observed in natural CH4–H2S–CO2–N2–H2O fluid inclusions, which are modeled as closed thermodynamic systems and thus serve as natural micro-laboratories representative of the C–O–H–N–S system. For the first time, we document solid–solid H2S (α ↔ β ↔ γ) transitions, complex clathrates and structural transformations of solid state H2S in natural inclusion gas mixtures. The new data on Raman spectroscopic features and a complete sequence of phase transition temperatures in the gas mixtures contribute to scientific advancements in fluid geochemistry. Enhanced understanding of the phase equilibria in the C–O–H–N–S system is a prerequisite for conscientious estimation ...

Chemical Geology, 2020

Abstract Upper Permian Zechstein carbonate Ca2 gas reservoirs in the southern part of the Pompeck... more Abstract Upper Permian Zechstein carbonate Ca2 gas reservoirs in the southern part of the Pompeckj Block in the North German Basin locally contain up to 36 vol% hydrogen sulfide (H2S) produced by thermochemical sulfate reduction (TSR). TSR was triggered by migration of dry to extremely dry coal gas from Upper Carboniferous into the Zechstein carbonate reservoirs. Methane reacted with dissolved sulfate at temperatures of The results of this study decipher three major stages of gas migration in the Pompeckj Block. Stage I commenced in the Late Triassic during burial when Zechstein Ca2 reservoirs were charged with dry CH4-CO2 ± N2 gas sourced from mature Upper Carboniferous coals. Burial continued through the Jurassic and caused alteration of Ca2 reservoir gas by sulfate reduction reactions due to increasing temperatures. Entrapment of CH4-H2S-CO2-N2 gases in fluid inclusions, hosted in cements and fracture-filling minerals, occurred at temperatures between 100 and 152 °C and was related to Stage II uplift in the Early Lower Cretaceous. In the Late Cretaceous (Stage III) deep burial of the Pompeckj Block led to charge of the Zechstein Ca2 carbonate reservoirs with Upper Carboniferous-derived CH4-CO2 ± N2 ± C2+ coal gas and/or dilution of existing reservoir gas at temperatures of 144–167 °C. Highly variable δ13CCH4 values from −18.7 to −8.7‰ and very negative δ13CCO2 values (−22.4 to −18.9‰) of H2S-rich fluid inclusion gases as well as negative δ13C values (−10.4 to −4.6‰) of host calcites reveal compelling evidence for participation of methane in TSR. Fluid inclusions imply that CH4-dominated TSR proceeded at Tmin of 135 °C in the presence of catalyzers such as H2S and dissolved Mg2+. This study demonstrates that fluid inclusions serve as an excellent and accurate tool for tracing H2S concentrations in hydrocarbon gases through time and space, which is not possible using the present-day compositions of natural reservoir gases. It also contributes to the understanding of carbonate reservoir-hosted hydrocarbon-bearing fluid systems and processes that significantly control the quality of reservoir gases.

Economic Geology, 2019

The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (... more The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (Albian-Vra-conian) along major faults in the Slata ore district raises the question of the roles played by halokinesis, hydrocarbons, and tectonics in mineralization. The Slata mining district, located in the Tunisian salt diapiric zone, contains Ba-Pb-(± Zn) ore hosted in the Aptian carbonates. The mineralogical paragenetic sequence consists of barite (Ba-1)–galena ± sphalerite ± calcite (Ca-1)–barite (Ba-2) and finally, late calcites (Ca-2 and Ca-3). Fluid inclusions from early barite reveal that it was precipitated from a warm (134°–157°C), H2O-NaCl-KCl-CaCl2, moderately saline (13.3–24.6 wt % NaCl equiv) basinal brine. This fluid is thought to have resulted from the mixing of a deep-seated, hot, metal-bearing fluid with a cooler, dilute SO42−-rich fluid. Early calcite and cogenetic sulfides (galena and sphalerite) precipitated from fluids of similar salinities and temperatures as the...

Metallomics, 2019

Surficial contamination is not the cause for abnormal Cu–Co concentrations in Haumaniastrum katan... more Surficial contamination is not the cause for abnormal Cu–Co concentrations in Haumaniastrum katangense.

Chemical Geology, 2018

Abstract The Earth's crust is endowed with outstanding mineral wealth, however, in the future... more Abstract The Earth's crust is endowed with outstanding mineral wealth, however, in the future near-surface ore deposits will become exhausted and mineral potential of deeper crustal levels will become a target for exploration. Knowledge of the fluid dynamics of deep-seated ore-forming systems in e.g. sedimentary basins is therefore crucial for developing genetic models, which would facilitate effective exploration of hidden orebodies. Here we utilized fluid inclusion and stable isotope analyses in order to decipher the ore-forming processes, which were responsible for deposition of considerable deep-seated (2.7–3.6 km) Zn-Pb mineralization in the Lower Saxony Basin (LSB). Massive sphalerite-rich stratiform/stratabound and vein-type mineralization in the LSB is hosted by Ca2 carbonate. Our data show that ore deposition was controlled by mixing of reservoir H 2 S with hot (T = 125–208 °C), highly-saline (21–32 wt% NaCl equiv.) metalliferous fluids ascending from greater depth along fault zones. Sulfur isotope ratios of sulfides (δ 34 S = −12.5 to +8.5‰) and carbon isotope ratios of fluid inclusion gases (δ 13 C CH4 = −6.2 to −22.7‰; δ 13 C CO2 = −0.8 to −6.2‰) reveal compelling evidence for TSR (thermochemical sulfate reduction)-derived origin of H 2 S. The ore-forming fluids were expelled from an over-pressurized system during Late Cretaceous basin inversion. Depth estimates show that the Zn-Pb mineralization in the LSB formed considerably deeper (3.3–4.4 km) than any other Phanerozoic MVT Zn-Pb deposit and therefore they can be classified as a super-deep, TSR-controlled MVT end-member.

Geosciences, 2018

The authors would like to correct the published article [...]

Geosciences, 2018

Hydrothermal fluorites from Paleozoic sedimentary rocks and volcanic units in the North German Ba... more Hydrothermal fluorites from Paleozoic sedimentary rocks and volcanic units in the North German Basin (NGB) have been investigated to create a petrographic and geochemical inventory—with particular focus on strategic elements such as rare earth elements (REE)—and to uncover possible links between the post-Variscan hydrothermal mineralization in the NGB and bordering areas such as the Harz Mountains and Flechtingen Calvörde Block (FCB). Fluorites from ten localities underwent a detailed petrographic examination, including SEM-BSE/CL imagery, and were compositionally analysed using LA-ICP-MS. Overall, REY concentrations are comparatively low in fluorite from all investigated areas—the median sum of REY ranges from 0.3 to 176 ppm. EuropiumCN anomalies are slightly negative or absent, indicating that either the formation fluid experienced temperatures above 250 °C or that fluid-rock interactions and REE enrichment was likely controlled by the source rock (i.e., volcanic) composition and ...

Ore Geology Reviews, 2015

Economic Geology

The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (... more The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (Albian-Vra-conian) along major faults in the Slata ore district raises the question of the roles played by halokinesis, hydrocarbons, and tectonics in mineralization. The Slata mining district, located in the Tunisian salt diapiric zone, contains Ba-Pb-(± Zn) ore hosted in the Aptian carbonates. The mineralogical paragenetic sequence consists of barite (Ba-1)–galena ± sphalerite ± calcite (Ca-1)–barite (Ba-2) and finally, late calcites (Ca-2 and Ca-3). Fluid inclusions from early barite reveal that it was precipitated from a warm (134°–157°C), H2O-NaCl-KCl-CaCl2, moderately saline (13.3–24.6 wt % NaCl equiv) basinal brine. This fluid is thought to have resulted from the mixing of a deep-seated, hot, metal-bearing fluid with a cooler, dilute SO42−-rich fluid. Early calcite and cogenetic sulfides (galena and sphalerite) precipitated from fluids of similar salinities and temperatures as the...

Mineralogy and Petrology

Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in publishe... more Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Mineralium deposita, May 7, 2024

Mineralium Deposita

The origin, evolution, and interplay of brine and hydrocarbon fluid systems play a crucial role i... more The origin, evolution, and interplay of brine and hydrocarbon fluid systems play a crucial role in the formation of deep sediment-hosted base metal ore deposits. Here we investigate ratios of halogens, noble gases, stable C and S isotopes, and metal budgets of aqueous brines, which deposited deep-seated and near-surface hydrothermal Zn-Pb mineralization hosted by Zechstein carbonates in the Lower Saxony Basin (North German Basin), by studies of fluid inclusions in sphalerite and quartz. Major and trace element geochemistry and noble gas isotopic signatures of brine inclusions revealed that the ore-forming fluids were highly reactive and experienced prolonged interactions with host rocks in the constricted, over-pressured metal source regions and consequently evolved from near-neutral, oxidized brines towards more reduced, acidic high-salinity brines. Quartz-hosted halite-saturated fluid inclusions with Th <200°C contain Zn and Pb concentrations up to ca. 9400 μg g-1 and 5200 μg g...

Applied Earth Science, 2019

Journal of African Earth Sciences, Feb 1, 2023

Mineralogy and Petrology, 2021

The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted main... more The Jebel El Akhouat Zn-Pb-(Ba-Sr) ore deposit, located in the Tunisian Dome zone, is hosted mainly in the organic matter-rich Albian and Cenomanian–Turonian rocks. The orebodies occur mainly as open-space fillings and are structurally-controlled. The paragenetic sequence consists of three stages, which reflect three ore events. Three discrete stages of Zn-Pb sulfide and/or Zn-Pb-Ba-Sr sulfide-sulfate ores are identified. Fluid inclusion study carried out on selected minerals of different stages reveals that sphalerite, galena, marcasite, celestine, barite, and fluorite precipitated as a result of mixing between a hydrothermal, saline, metal-rich basinal fluid and a low-temperature, less saline, metal-depleted, sulfur- or sulfate-rich fluid with the intermittent involvement of hydrocarbons. Based on sulfur isotope data, sulfur of sulfides was derived from the reduction of the dissolved Triassic sulfates primary through thermochemical sulfate reduction with a contribution of bacterial sulfate reduction. The Pb isotopic composition of galena samples and trace elements data of the host carbonate rocks suggest that metals were derived primarily from the Paleozoic siliciclastic rocks with a contribution of the organic matter-rich Albian and Cenomanian–Turonian rocks. The Alpine orogeny triggered the migration of the metalliferous fluids from the deep parts of the basin towards the peridiapiric paleohigh of Ech Chehid diapir through major faults towards the loci of deposition.

Mineralogy and Petrology, 2021

Jemmali et al. 2021

Mineralium Deposita, 2021

Stibnite was mined until the end of the twentieth century in the Schlaining ore district, Austria... more Stibnite was mined until the end of the twentieth century in the Schlaining ore district, Austria, near the easternmost border of the Eastern Alps where windows of Penninic ophiolites and metasediments are exposed below Austroalpine tectonic units. In Early Miocene, structurally controlled small vein and metasomatic stibnite-quartz deposits were formed in Penninic Mesozoic calcareous marbles and calcite schists. Fluid inclusion studies identified two fluids involved in the mineralization: (i) a low-salinity, low-CO2 metamorphic fluid that precipitated quartz at approximately 240 °C and (ii) a stibnite-forming ore fluid that had a meteoric origin. There is no evidence of boiling or that the fluids mixed during mineralization. The ore components Sb and H2S were leached by fluid/rock interaction from buried rock units. Stibnite mineralization occurred by cooling the ore fluid to below 300 °C, at less than 2000 m depth. Quartz precipitated at slightly lower temperatures, approximately c...

Nature Communications, 2021

C–O–H–N–S-bearing fluids are known as one of the most challenging geochemical systems due to scar... more C–O–H–N–S-bearing fluids are known as one of the most challenging geochemical systems due to scarcity of available experimental data. H2S-rich fluid systems were recognized in a wide array of world-class mineral deposits and hydrocarbon reservoirs. Here we report on a nature of low-temperature (T ≥ −192 °C) phase transitions observed in natural CH4–H2S–CO2–N2–H2O fluid inclusions, which are modeled as closed thermodynamic systems and thus serve as natural micro-laboratories representative of the C–O–H–N–S system. For the first time, we document solid–solid H2S (α ↔ β ↔ γ) transitions, complex clathrates and structural transformations of solid state H2S in natural inclusion gas mixtures. The new data on Raman spectroscopic features and a complete sequence of phase transition temperatures in the gas mixtures contribute to scientific advancements in fluid geochemistry. Enhanced understanding of the phase equilibria in the C–O–H–N–S system is a prerequisite for conscientious estimation ...

Chemical Geology, 2020

Abstract Upper Permian Zechstein carbonate Ca2 gas reservoirs in the southern part of the Pompeck... more Abstract Upper Permian Zechstein carbonate Ca2 gas reservoirs in the southern part of the Pompeckj Block in the North German Basin locally contain up to 36 vol% hydrogen sulfide (H2S) produced by thermochemical sulfate reduction (TSR). TSR was triggered by migration of dry to extremely dry coal gas from Upper Carboniferous into the Zechstein carbonate reservoirs. Methane reacted with dissolved sulfate at temperatures of The results of this study decipher three major stages of gas migration in the Pompeckj Block. Stage I commenced in the Late Triassic during burial when Zechstein Ca2 reservoirs were charged with dry CH4-CO2 ± N2 gas sourced from mature Upper Carboniferous coals. Burial continued through the Jurassic and caused alteration of Ca2 reservoir gas by sulfate reduction reactions due to increasing temperatures. Entrapment of CH4-H2S-CO2-N2 gases in fluid inclusions, hosted in cements and fracture-filling minerals, occurred at temperatures between 100 and 152 °C and was related to Stage II uplift in the Early Lower Cretaceous. In the Late Cretaceous (Stage III) deep burial of the Pompeckj Block led to charge of the Zechstein Ca2 carbonate reservoirs with Upper Carboniferous-derived CH4-CO2 ± N2 ± C2+ coal gas and/or dilution of existing reservoir gas at temperatures of 144–167 °C. Highly variable δ13CCH4 values from −18.7 to −8.7‰ and very negative δ13CCO2 values (−22.4 to −18.9‰) of H2S-rich fluid inclusion gases as well as negative δ13C values (−10.4 to −4.6‰) of host calcites reveal compelling evidence for participation of methane in TSR. Fluid inclusions imply that CH4-dominated TSR proceeded at Tmin of 135 °C in the presence of catalyzers such as H2S and dissolved Mg2+. This study demonstrates that fluid inclusions serve as an excellent and accurate tool for tracing H2S concentrations in hydrocarbon gases through time and space, which is not possible using the present-day compositions of natural reservoir gases. It also contributes to the understanding of carbonate reservoir-hosted hydrocarbon-bearing fluid systems and processes that significantly control the quality of reservoir gases.

Economic Geology, 2019

The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (... more The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (Albian-Vra-conian) along major faults in the Slata ore district raises the question of the roles played by halokinesis, hydrocarbons, and tectonics in mineralization. The Slata mining district, located in the Tunisian salt diapiric zone, contains Ba-Pb-(± Zn) ore hosted in the Aptian carbonates. The mineralogical paragenetic sequence consists of barite (Ba-1)–galena ± sphalerite ± calcite (Ca-1)–barite (Ba-2) and finally, late calcites (Ca-2 and Ca-3). Fluid inclusions from early barite reveal that it was precipitated from a warm (134°–157°C), H2O-NaCl-KCl-CaCl2, moderately saline (13.3–24.6 wt % NaCl equiv) basinal brine. This fluid is thought to have resulted from the mixing of a deep-seated, hot, metal-bearing fluid with a cooler, dilute SO42−-rich fluid. Early calcite and cogenetic sulfides (galena and sphalerite) precipitated from fluids of similar salinities and temperatures as the...

Metallomics, 2019

Surficial contamination is not the cause for abnormal Cu–Co concentrations in Haumaniastrum katan... more Surficial contamination is not the cause for abnormal Cu–Co concentrations in Haumaniastrum katangense.

Chemical Geology, 2018

Abstract The Earth's crust is endowed with outstanding mineral wealth, however, in the future... more Abstract The Earth's crust is endowed with outstanding mineral wealth, however, in the future near-surface ore deposits will become exhausted and mineral potential of deeper crustal levels will become a target for exploration. Knowledge of the fluid dynamics of deep-seated ore-forming systems in e.g. sedimentary basins is therefore crucial for developing genetic models, which would facilitate effective exploration of hidden orebodies. Here we utilized fluid inclusion and stable isotope analyses in order to decipher the ore-forming processes, which were responsible for deposition of considerable deep-seated (2.7–3.6 km) Zn-Pb mineralization in the Lower Saxony Basin (LSB). Massive sphalerite-rich stratiform/stratabound and vein-type mineralization in the LSB is hosted by Ca2 carbonate. Our data show that ore deposition was controlled by mixing of reservoir H 2 S with hot (T = 125–208 °C), highly-saline (21–32 wt% NaCl equiv.) metalliferous fluids ascending from greater depth along fault zones. Sulfur isotope ratios of sulfides (δ 34 S = −12.5 to +8.5‰) and carbon isotope ratios of fluid inclusion gases (δ 13 C CH4 = −6.2 to −22.7‰; δ 13 C CO2 = −0.8 to −6.2‰) reveal compelling evidence for TSR (thermochemical sulfate reduction)-derived origin of H 2 S. The ore-forming fluids were expelled from an over-pressurized system during Late Cretaceous basin inversion. Depth estimates show that the Zn-Pb mineralization in the LSB formed considerably deeper (3.3–4.4 km) than any other Phanerozoic MVT Zn-Pb deposit and therefore they can be classified as a super-deep, TSR-controlled MVT end-member.

Geosciences, 2018

The authors would like to correct the published article [...]

Geosciences, 2018

Hydrothermal fluorites from Paleozoic sedimentary rocks and volcanic units in the North German Ba... more Hydrothermal fluorites from Paleozoic sedimentary rocks and volcanic units in the North German Basin (NGB) have been investigated to create a petrographic and geochemical inventory—with particular focus on strategic elements such as rare earth elements (REE)—and to uncover possible links between the post-Variscan hydrothermal mineralization in the NGB and bordering areas such as the Harz Mountains and Flechtingen Calvörde Block (FCB). Fluorites from ten localities underwent a detailed petrographic examination, including SEM-BSE/CL imagery, and were compositionally analysed using LA-ICP-MS. Overall, REY concentrations are comparatively low in fluorite from all investigated areas—the median sum of REY ranges from 0.3 to 176 ppm. EuropiumCN anomalies are slightly negative or absent, indicating that either the formation fluid experienced temperatures above 250 °C or that fluid-rock interactions and REE enrichment was likely controlled by the source rock (i.e., volcanic) composition and ...

Ore Geology Reviews, 2015

Economic Geology

The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (... more The juxtaposition of a Triassic evaporite diapir with the organic matter-rich Fahdene Formation (Albian-Vra-conian) along major faults in the Slata ore district raises the question of the roles played by halokinesis, hydrocarbons, and tectonics in mineralization. The Slata mining district, located in the Tunisian salt diapiric zone, contains Ba-Pb-(± Zn) ore hosted in the Aptian carbonates. The mineralogical paragenetic sequence consists of barite (Ba-1)–galena ± sphalerite ± calcite (Ca-1)–barite (Ba-2) and finally, late calcites (Ca-2 and Ca-3). Fluid inclusions from early barite reveal that it was precipitated from a warm (134°–157°C), H2O-NaCl-KCl-CaCl2, moderately saline (13.3–24.6 wt % NaCl equiv) basinal brine. This fluid is thought to have resulted from the mixing of a deep-seated, hot, metal-bearing fluid with a cooler, dilute SO42−-rich fluid. Early calcite and cogenetic sulfides (galena and sphalerite) precipitated from fluids of similar salinities and temperatures as the...