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1.
The Jinding Zn–Pb deposit located in the Mesozoic-Cenozoic Lanping Basin of southwest China has ore reserves of ∼ 220 Mt with an average grade of 6.1% Zn and 1.3% Pb. The mineralization is hosted by sandstone in the Early Cretaceous Jingxing Formation and limestone breccia in the Paleocene Yunlong Formation. Mineralization in both types of host rocks is characterized by a paragenetic sequence beginning with marcasite–sphalerite (Stage 1) followed by pyrite–marcasite–sphalerite–galena (Stage 2), and then galena–sphalerite–pyrite–sulfate–carbonate (Stage 3). Pyrite from these stages have different δ33S compositions with pyrite from Stage 1 averaging − 9.6‰, Stage 2 averaging − 8.9‰, and Stage 3 averaging + 0.3‰. Sphalerite hosted by the sandstone has similar δ66Zn values ranging from 0.10 to 0.30‰ in all stages of the mineralization, but sphalerite samples from the limestone breccia-hosted ore show variable δ66Zn values between − 0.03 and 0.20‰. Our data on sphalerite precipitated during the earlier stages of mineralization has a constant δ66Zn value and cogenetic pyrite displays a very light sulfur isotope signature, which we believe to reflect a sulfur source that formed during bacterial sulfate reduction (BSR). The Stage 3 sphalerite and pyrite precipitated from a late influx of metal-rich basinal brine, which had a relatively constant variable δ66Zn isotopic composition due to open system isotope fractionation, and a near zero δ33S composition due to the influence of abiotic thermochemical sulfate reduction from observed sulfates in the host rock. 相似文献
2.
《Journal of Geochemical Exploration》1997,59(1):1-10
The Navia gold belt is located in the West Asturian-Leonese Zone of the Iberian Variscan Orogen. The host rocks of the mineralization are quartzites, sandstones and black shales of Cambro-Ordovician age. The gold belt extends along 35 km and has five major veins: Penedela, Encarnita, Fornaza, Carmina and S. Jose. The ores belong to at least four associations having contrasting mineralogies and textures. The δ34S values for individual mineral phases reflect the polyphase metallogenic history. The older association (Stage 1) is Fe-Mn-rich and is made up of spessartine, grunerite-dannemorite and quartz, with magnetite, pyrrhotite and chalcopyrite as metallic phases. The mineralization of Stage 1 is followed by the As-rich Stage 2 with quartz, arsenopyrite and pyrite. The δ34S values for pyrite range from 14.9 to 19.9 per mil (n = 16), and for arsenopyrite from 13.2 to 17.3 per mil (n = 7). The observed isotopic homogeneity likely implies isotopic equilibrium at the scale of the gold vein. Stage 3 contains a coarse-grained base metal sulphide-rich association. The δ4S values for sphalerite range from 16.4 to 20.6 per mil (n= 16), and for galena from 17.0 to 18.7 per mil (n = 11). δ34Ssp > δ34Sgl suggests that the sulphur isotopic fractionation of the ore-forming system had reached equilibrium. The youngest crosscutting mineral association (Stage 4) consists of Pb-Sb sulphosalts, bornite, electrum and quartz. The δ34S values for sulphosalts range from 9.7 to 15.8 per mil, showing the lightest results of the Navia sulphides.The relatively tight clustering of δ34S values of the Au-related sulphides, and the results of fluid inclusions and paragenetic studies, can be interpreted to indicate that the hydrothermal fluids of the last three stages were dominated by H2S. In the H2S predominant field, sulphide minerals precipitating from solutions would exhibit δ34S values similar to the δ34SΣS value of the ore fluid. The heavy δ34SΣS of the Navia fluids is consistent with leaching of sulphur from the host rocks. The main sulphur source could be diagenetic pyrite from the siliciclastic rocks of the Cabos and Luarca Formations, which exhibit δ34S values from 8.3 to 21.2 per mil. An additional sulphur-source in Stage 3 would be the leaching of disseminated sphalerite and galena present in Cambrian carbonates. 相似文献
3.
Although Zn–Pb deposits are one of the most important Cd reservoirs in the earth, few studies have focused on the Cd isotopic fractionation in Zn–Pb hydrothermal systems. This study investigates the causes and consequences of cadmium and sulfur isotope fractionation in a large hydrothermal system at the Tianbaoshan Zn–Pb–Cd deposit from the Sichuan–Yunnan–Guizhou (SYG) metallogenic province, SW China. Moderate variations in Cd and S isotope compositions have been measured in sphalerite cover a distance of about 78 m. Sphalerite has δ114/110Cd values ranging from 0.01 to 0.57‰, and sulfides (sphalerite, galena and chalcopyrite) have δ34SCDT values ranging from 0.2 to 5.0‰. Although δ34SCDT and δ114/110Cd values in sphalerites have no regular spatial variations, the δ34SCDT values in galena and calculated ore-forming fluid temperatures decreased from 2.1 to 0.2‰ and from about 290 to 130 °C, respectively, from the bottom to the top of the deposit. Heavy Cd isotopes are enriched in early precipitated sphalerite in contrast to previous studies. We suggest that Cd isotopic compositions in ore-forming fluids are heterogeneous, which result in heavy Cd isotope enrichment in early precipitated sphalerite. In comparison with other Zn–Pb deposits in the SYG area, the Tianbaoshan deposit has moderate Cd contents and small isotope fractionation, suggesting differences in origin to other Zn–Pb deposits in the SYG province.In the Tianbaoshan deposit, the calculated δ34S∑S-fluids value is 4.2‰, which is not only higher than the mantle-derived magmatic sulfur (0 ± 3‰), but also quite lower than those of Ediacaran marine sulfates (about 30 to 35‰). Thus, we suggest that reduced sulfur of ore-forming fluids in the deposit was mainly derived from the leaching of the basement, which contains large amount of volcanic or intrusive rocks. Based upon a combination of Cd and S isotopic systems, the Tianbaoshan deposit has different geochemical characteristics from typical Zn–Pb deposits (e.g., the Huize deposit) in SYG area, indicating the unique origin of this deposit. 相似文献
4.
Zhang Hongjie Fan Haifeng Xiao Chaoyi Wen Hanjie Ye Lin Huang Zhilong Zhou Jiaxi Guo Qingjun 《中国地球化学学报》2019,38(5):642-653
The Sichuan–Yunnan–Guizhou (SYG) metallogenic province of southwest China is one of the most important Zn–Pb ore zones in China, with ~ 200 Mt Zn–Pb ores at mean grades of 10 wt.% Zn and 5 wt.% Pb. The source and mechanism of the regional Zn–Pb mineralization remain controversial despite many investigations that have been conducted. The Wusihe Zn–Pb deposit is a representative large-scale Zn–Pb deposit in the northern SYG, which mainly occurs in the Dengying Formation and yields Zn–Pb resources of ~ 3.7 Mt. In this paper, Zn and S isotopes, and Fe and Cd contents of sphalerite from the Wusihe deposit were investigated in an attempt to constrain the controls on Zn and S isotopic variations, the potential sources of ore-forming components, and the possible mineralization mechanisms. Both the δ66Zn and δ34S values in sphalerite from the Wusihe deposit increase systematically from the bottom to the top of the strata-bound orebodies. Such spatial evolution in δ66Zn and δ34S values of sphalerite can be attributed to isotopic Rayleigh fractionation during sphalerite precipitation with temperature variations. The strong correlations between the Zn–S isotopic compositions and Fe–Cd concentrations in sphalerite suggest that their variations were dominated by a similar mechanism. However, the Rayleigh fractionation mechanism cannot explain the spatial variations of Fe and Cd concentrations of sphalerite in this deposit. It is noted that the bottom and top sphalerites from the strata-bound orebodies document contrasting Zn and S isotopic compositions which correspond to the Zn and S isotopic characteristics of basement rocks and host rocks, respectively. Therefore, the mixing of two-source fluids with distinct Zn–S isotopic signatures was responsible for the spatial variations of Zn–S isotopic compositions of sphalerite from the Wusihe deposit. The fluids from basement rocks are characterized by relatively lighter Zn (~ 0.2 ‰) and S (~ 5 ‰) isotopic compositions while the fluids from host rocks are marked by relatively heavier Zn (~ 0.6 ‰) and S (~ 15 ‰) isotopic compositions.
相似文献5.
Dashuigou Tellurium Deposit in Sichuan Province, China: S, C, O, and H Isotope Data and Their Implications on Hydrothermal Mineralization 总被引：6，自引：0，他引：6
Jingwen MAO Yitian WANG Tiping DING Yuchuan CHEN Jiaxiu WEI Jianzhao YIN 《Resource Geology》2002,52(1):15-23
Abstract: Dashuigou, a unique tellurium‐dominated deposit over the world, is located in the western margin of the Yangtze cra‐ton in southwestern China. It is characterized by high‐grade tellurium accompanied by bismuth, gold, silver, and sulfur, and occurs in the area of less than one km2. The mineralization is divided into three stages, i.e. (1) tellurium‐bearing pyrrhotite–pyrite stage, (2) tetradymite stage, and (3) auriferous quartz veins stage. Tellurium mineralization coexisting with bismuth, silver, selenium, and gold predominantly develops in the stage 2, while the stage 1 is enriched only in sulfur and iron, and the stage 3 is very weakly mineralized with gold. The δ34S values of sulfides in the ore of the deposit vary in a narrow range of –3.1 ‐ +2.8 per mil with –3.1 ‐ +2.8 per mil for the stage 1 and –0.5 ‐ +2.1 for the stage 2, showing the isotopic characteristics of mantle derived sulfur. The δ13C values of vein dolomites vary from –5.3 to –7.2 per mil, with –5.3 ‐ –6.6 per mil for the stage 1 and –5.3 ‐ –7.2 per mil for the stage 2, which are significantly different from those of surrounding Triassic marble with δ13C values of –0.3 ‐ +2.8 per mil, and show characteristics of mantle derived carbon. The δ18O values of vein dolomites range from +10.2 to +13.1 per mil, which are higher than those of carbonatite, but lower than those of the marble. Their corresponding δ18Owater values are +0.6 ‐ +3.9 per mil, with +2.7 ‐ +3.8 per mil for the stage 1 and +0.6 ‐ +3.9 per mil for the stage 2. The data implies that these vein carbonates were formed by the mixing fluids of magmatic or mantle source with meteoric or formation water. The δ18O values of ore‐forming fluids responsible for the formation of vein quartz are estimated to be +3.2 to +6.8, the δD values of inclusion fluids of the quartz are measured to be –54 to –82 per mil. All those stable isotopic data suggest the involvement of the fluids from mantle and/or mantle‐derived magmas through fault system in the forming process of the Dashuigou tellurium deposit. 相似文献
6.
7.
The Bleiberg Pb-Zn deposit in the Drau Range is the type locality of Alpine-type carbonate-hosted Pb-Zn deposits. Its origin has been the subject of on-going controversy with two contrasting genetic models proposed: (1) the SEDEX model, with ore forming contemporaneously with sedimentation of the Triassic host rocks at about 220 Ma vs. (2) the epigenetic MVT model, with ores forming after host rock sedimentation at about 200 Ma or later. Both models assume that, on a deposit or even district scale, a fixed paragenetic sequence of ore minerals can be established. The results of our detailed petrographic, chemical and sulfur isotope study of two key ore-samples from two major ore horizons in the Wetterstein Formation at Bleiberg (EHK02 Erzkalk horizon and Blb17 Maxer Bänke horizon) demonstrate that there is no fixed paragenetic sequence of ore minerals. Small-scale non-systematic variations are recorded in textures, sphalerite chemistry and δ34S. In each sample, texturally different sphalerite types (colloform schalenblende, fine- and coarse-grained crystalline sphalerite) co-occur on a millimeter to centimeter scale. These sphalerites represent multiple mineralization stages/pulses since they differ in their trace element inventory and in their δ34S. Nonetheless, there is some correspondence of sphalerite micro-textures, sulfur isotope and chemical composition between the two samples, with microcrystalline colloform schalenblende being Fe-rich, having high Fe/Cd (15 and 9, respectively) and a light sulfur isotope composition (δ34S −26.0 to −16.2‰). Cadmium-rich and Fe-poor sphalerite in both samples has relatively heavier sulfur isotope composition: in sample EHK02 this sphalerite has Fe/Cd of ∼0.5 and δ34S from −6.6 to −4.6‰; in sample Blb17 Fe/Cd is ∼0.1 and δ34S ranges from −15.0 to −1.5‰. Barite, which is restricted to sample EHK02, has δ34S ≈ 17‰. The large variations in δ34S recorded on the mm to cm-scale is consistent with variable contributions of reduced sulfur from two different sulfur reservoirs. The dominant reservoir with δ34S values <−20‰ likely results from local bacteriogenic sulfate reduction (BSR), whereas the second reservoir, with δ34S about −5‰ suggests a hydrothermal source likely linked with thermochemical sulfate reduction (TSR). Based on this small- to micro-scale study, no simple, deposit-wide paragenetic and sulfur isotope evolution with time can be established. In the Erzkalk ore (sample EHK02) an earlier Pb-Zn-Ba stage, characterized by heavy sulfur isotope values, is succeeded by a light δ34S-dominated Zn-Pb-F stage. In contrast, the several mineralization pulses identified in the stratiform Zn-Pb-F Maxer Bänke ore (sample Blb17) define a broad trend to heavier sulfur isotope values with time. The interaction documented in these samples between two sulfur reservoirs is considered a key mechanism of ore formation. 相似文献
8.
Zhaxikang is one large Sb–Pb–Zn–Ag deposit located in the North Himalaya of southern Tibet. To date, the genesis of this deposit still remains controversial. Here, we present new pyrite Fe and sphalerite Zn isotopic data for the first three stages of mineralization, Fe–Zn isotopic data for Mn–Fe carbonate that formed during the first two stages of mineralization, and Zn isotopic data for the slate wall rocks of the Jurassic Ridang Formation to discuss the genesis of the Zhaxikang deposit. The overall δ56Fe and δ66Zn values range from −0.80‰ to 0.43‰ and from −0.03‰ to 0.38‰, respectively. The δ56Fe values of Mn–Fe carbonates are lighter than those of associated pyrite in six mineral pairs, indicating that the iron carbonates are preferentially enriched in light Fe isotopes relative to pyrite. The sphalerite has lighter δ66Zn values than associated Mn–Fe carbonates in three mineral pairs.The δ56Fe values of pyrite that formed during the first three stages of mineralization gradually increase from stage 1 (−0.33‰ to −0.09‰) through stage 2 (−0.30‰ to 0.19‰) to stage 3 (0.16‰–0.43‰). In comparison, the sphalerite that formed during these stages has δ66Zn values that gradually decrease from stage 1 (0.16‰–0.35‰) through stage 2 (0.09‰–0.23‰) to stage 3 (−0.03‰ to 0.22‰). These data, in conjunction with the observations of hand specimens and thin sections, suggest that the deposit was overprinted by a second pulse of mineralization. This overprint would account for these Fe–Zn isotopic variations as well as the kinetic Rayleigh fractionation that occurred during mineralization. The temporally increasing δ56Fe and decreasing δ66Zn values recorded in the deposit are also coincident with an increase in alteration, again supporting the existence of two pulses of mineralization. The δ56Fe values of the first pulse of ore-forming fluid were calculated using theoretical equations, yielding values of −0.54‰ to −0.34‰ that overlap with those of submarine hydrothermal solutions (−1‰ to 0‰). However, the δ56Fe values of the stage 3 pyrite are heavier than those of typical submarine hydrothermal solutions, which suggests that the second pulse of mineralization was probably derived from a magmatic hydrothermal fluid. In addition, the second pulse of ore-forming fluid has brought some Fe and taken away parts of Zn, which results the lighter δ66Zn values of sphalerite and heavier δ56Fe values of pyrite from the second pulse of mineralization. Overall, the Zhaxikang deposit records two pulses of mineralization, and the overprint by the second pulse of mineralization causes the lighter δ66Zn values and heavier δ56Fe values of modified samples. 相似文献
9.
The Shanshulin Pb–Zn deposit occurs in Upper Carboniferous Huanglong Formation dolomitic limestone and dolostone, and is located in the western Yangtze Block, about 270 km west of Guiyang city in southwest China. Ore bodies occur along high angle thrust faults affiliated to the Weishui regional fault zone and within the northwestern part of the Guanyinshan anticline. Sulfide ores are composed of sphalerite, pyrite, and galena that are accompanied by calcite and subordinate dolomite. Twenty-two ore bodies have been found in the Shanshulin deposit area, with a combined 2.7 million tonnes of sulfide ores grading 0.54 to 8.94 wt.% Pb and 1.09 to 26.64 wt.% Zn. Calcite samples have δ13CPDB and δ18OSMOW values ranging from − 3.1 to + 2.5‰ and + 18.8 to + 26.5‰, respectively. These values are higher than mantle and sedimentary organic matter, but are similar to marine carbonate rocks in a δ13CPDB vs. δ18OSMOW diagram, suggesting that carbon in the hydrothermal fluid was most likely derived from the carbonate country rocks. The δ34SCDT values of sphalerite and galena samples range from + 18.9 to + 20.3‰ and + 15.6 to + 17.1‰, respectively. These values suggest that evaporites are the most probable source of sulfur. The δ34SCDT values of symbiotic sphalerite–galena mineral pairs indicate that deposition of sulfides took place under chemical equilibrium conditions. Calculated temperatures of S isotope thermodynamic equilibrium fractionation based on sphalerite–galena mineral pairs range from 135 to 292 °C, consistent with previous fluid inclusion studies. Temperatures above 100 °C preclude derivation of sulfur through bacterial sulfate reduction (BSR) and suggest that reduced sulfur in the hydrothermal fluid was most likely supplied through thermo-chemical sulfate reduction (TSR). Twelve sphalerite samples have δ66Zn values ranging from 0.00 to + 0.55‰ (mean + 0.25‰) relative to the JMC 3-0749L zinc isotope standard. Stages I to III sphalerite samples have δ66Zn values ranging from 0.00 to + 0.07‰, + 0.12 to + 0.23‰, and + 0.29 to + 0.55‰, respectively, showing the relatively heavier Zn isotopic compositions in later versus earlier sphalerite. The variations of Zn isotope values are likely due to kinetic Raleigh fractional crystallization. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of the sulfide samples fall in the range of 18.362 to 18.573, 15.505 to 15.769 and 38.302 to 39.223, respectively. The Pb isotopic ratios of the studied deposit plot in the field that covers the upper crust, orogenic belt and mantle Pb evolution curves and overlaps with the age-corrected Proterozoic folded basement rocks, Devonian to Lower Permian sedimentary rocks and Middle Permian Emeishan flood basalts in a 207Pb/204Pb vs. 206Pb/204Pb diagram. This observation points to the derivation of Pb metal from mixed sources. Sphalerite samples have 87Sr/86Sr200 Ma ratios ranging from 0.7107 to 0.7115 similar to the age-corrected Devonian to Lower Permian sedimentary rocks (0.7073 to 0.7111), higher than the age-corrected Middle Permian basalts (0.7039 to 0.7078), and lower than the age-corrected Proterozoic folded basement (0.7243 to 0.7288). Therefore, the Sr isotope data support a mixed source. Studies on the geology and isotope geochemistry suggest that the Shanshulin deposit is a carbonate-hosted, thrust fault-controlled, strata-bound, epigenetic, high grade deposit formed by fluids and metals of mixed origin. 相似文献
10.
The sulphur isotope composition of 233 sulphides and 40 sulphates has been investigated and evaluated in combination with 29 earlier published data. The total variation of δ34S values for the sulphides and the sulphates ranges from ?40 up to ?1 ‰ and from +7 up to +20 ‰, respectively. For the mineral species the variations are (with number of samples in brackets): galena (96) ?32 up to ?2 ‰, sphalerite (141) ?30 up to ?4 ‰, marcasite (16) ?27 up to ?1 ‰, pyrite (10) ?26 up to ?13 ‰, molybedenite (3) ?40 up to ?29 ‰, anhydrite and gypsum (8) +15 up to +20 ‰, coelestine (1) +19 ‰, and barite (33) +7 up to +18 ‰. The frequency distribution of the δ34S values corresponds with the complexity of the ore forming processes which resulted in six strata-bound ore mineralizations. The sulphate values clearly show that the sulphate sulphur originates from sea water sulphate. The sulphides are formed by bacteriogeneric processes from seawater sulphate, and their sulphur isotope composition depends on the lithofacies of the sediments as well as on the following diagenetic processes. 相似文献
11.
E. P. Ambler P. M. Ashley R. A. Both T. H. Donnelly 《Australian Journal of Earth Sciences》2013,60(7-8):399-409
The Mount Black Pb‐Zn deposit is a quartz‐galena‐sphalerite replacement body in the Silurian Cooleman Limestone. Fluid inclusion homogenisation temperatures range from 120° to 170°C for paragenetically early sphalerite, to 210° to 315°C for late quartz, and 245° to 320°C for calcite from contiguous recrystallised limestone. Fluid salinities increased with rising temperature, during deposition of the minerals, and the fluid composition changed from NaCl‐rich to possibly CaCl2‐NaCl (‐?MgCl2)‐rich brines. δ34S values of sphalerite and galena range from —8.1 to —2.7 per mil, and —13,5 to —4.4 per mil respectively. Although a magmatic source for sulphur is not excluded, it is suggested that most probably the sulphur was derived by biogenic reduction of sea‐water sulphate during diagenesis. Carbon and oxygen isotope data for the Cooleman Limestone range from compositions typical of Silurian marine carbonate in samples distant from the deposit, to fluctuating, but 12C‐ and 16O‐enriched in recrystallised material adjacent to the quartz‐sulphide rocks. 12C‐enrichment probably reflects organic carbon oxidation during karst formation, continuing later during limestone recrystallisation and accompanied by 16O‐enrichment during the action of saline formation waters. The process of formation of the Mount Black deposit may have been analogous to that of Mississippi Valley‐type deposits, but modified by and/or resulting from, an increasing geothermal gradient caused by nearby synchronous intrusions. 相似文献
12.
The Ohori ore deposit is one of the Cu–Pb–Zn deposits in the Green Tuff region, NE Japan, and consists of skarn‐type (Kaninomata) and vein‐type (Nakanomata) orebodies. The former has a unique origin because its original calcareous rocks were made by hydrothermal precipitation during Miocene submarine volcanism. Carbon and oxygen isotope ratios of skarn calcite and sulfur isotope ratios of sulfides were measured in and around the deposit. Carbon and oxygen isotope ratios of the skarn calcite are δ13C = ?15.51 to ?5.1‰, δ18O = +3.6 to +22.5‰. δ13C values are slightly lower than those of the Cretaceous skarn deposits in Japan. These isotope ratios of the Kaninomata skarn show that the original calcareous rocks resemble the present submarine hydrothermal carbonates at the CLAM Site, Okinawa Trough, than Cenozoic limestones, even though some isotopic shifts had occurred during later skarnization. δ34S ratios of the sulfide minerals from the Kaninomata and Nakanomata orebodies are mostly in a narrow range of +4.0 to +7.0‰ and they resemble each other, suggesting the same sulfur origin for the both deposits. The magnetite‐series Tertiary Kaninomatasawa granite is distributed just beneath the skarn layer and has δ34S ratios of +7.5 to 8.1‰. The heavy sulfur isotope ratio of the skarn sulfides may have been affected by the Kaninomatasawa granite. 相似文献
13.
《International Geology Review》2012,54(6):526-546
The Dashuigou tellurium deposit, located on the western margin of the Yangtze platform, is unique. The deposit is hosted by Triassic metabasalt 50 to 80 meters thick. The orebodies occur as a group of NNE-striking parallel veins. Mineralization developed in three stages: Stage I— pyrrhotite-pyrite, Stage II—tetradymite, and Stage III—chalcopyrite-pyrite. Stage II is the principal tellurium mineralization stage and the tellurium-bearing minerals are mainly tetradymite, tsumoite, tellurbismuth, joseite, calaverite, stuetzite, and native tellurium. The general ore grade of the tellurium in Stage II ranges from 0.2 to 5 wt%, and it reaches 15 to 25 wt% for the massive ores. The dominant gangue minerals are calcite and dolomite, with minor biotite, muscovite, albite, quartz, and chlorite. Fluid-inclusion studies of calcite, dolomite, and quartz from Stages I, II, and III yield homogenization temperatures of 356° to 260° C (mean = 320° C), 295° to 198° C (mean = 240°), and 235° to 152° C (mean = 170° C), respectively. Salinities of primary fluid inclusions in all three stages are 1.5 to 5.8 wt% NaCl equivalent, 9 to 15.2 wt% NaCl equivalent, and 2.8 to 3.0 wt% NaCl equivalent, respectively. Isotopic studies show that δ34 values of sulfides range from -2.2 to +2.8 per mil. δ13C values of calcites and dolomites in the ore veins range from -5.3 to -7.42 per mil, and δ18O values range from +10.9 to +13.1 per mil, which are quite different from the δ13C values of+1.0 to +2.8 per mil and δ18O values of +16.8 to +28.5 per mil for the calcites from the Triassic carbonates in the deposit. The δD and δ18O values of muscovite and quartz were measured to be -61 to -54 per mil and +9.9 to +13.0 per mil, respectively. Values of δ18Owater computed from fluid-inclusion trapping temperatures are +3.9 and +7 per mil. A date of 93 Ma was obtained through measurement of muscovite from the No. 12 ore vein. Sulfur-, oxygen-, carbon-, and hydrogenisotope data indicate that the ore-forming substances of the Dashuigou tellurium deposit were derived from deep-seated sources, and the mineralizations probably are associated with Late Mesozoic alkaline or alkaline granitic magmatism. The estimated sulfur fugacities (fs2) are 10?16.7 for Stage I and 10?14 to 1015.5 for Stage II, whereas the tellurium fugacities (fTe2) are 10?15 to 10?14 and 10?11.2 to 10?10.5, respectively. 相似文献
14.
L. I. Rogulina V. G. Moiseenko E. G. Odarichenko E. N. Voropayeva 《Doklady Earth Sciences》2018,479(1):352-354
The S isotopic composition in the ore-forming minerals galena and sphalerite was studied in different Ag–Pb–Zn deposits of the region. It was pointed out that the δ34S modal values range from–1.2 to +6.7‰ in the minerals with a positive value for the skarn mineralization. In the flyschoid formation, the vein-type mineralization is characterized by negative and positive values. The narrow range of δ34S values indicates the marginal-continental type of the mineralization and the multiple origins of its sources. 相似文献
15.
Changming Wang Da Zhang Ganguo Wu M. Santosh Jing Zhang Yigan Xu Yaoyao Zhang 《Mineralium Deposita》2014,49(6):733-749
The Lengshuikeng ore district in east-central China has an ore reserve of ～43 Mt with an average grade of 204.53 g/t Ag and 4.63 % Pb?+?Zn. Based on contrasting geological characteristics, the mineralization in the Lengshuikeng ore district can be divided into porphyry-hosted and stratabound types. The porphyry-hosted mineralization is distributed in and around the Lengshuikeng granite porphyry and shows a distinct alteration zoning including minor chloritization and sericitization in the proximal zone; sericitization, silicification, and carbonatization in the peripheral zone; and sericitization and carbonatization in the distal zone. The stratabound mineralization occurs in volcano-sedimentary rocks at ～100–400 m depth without obvious zoning of alterations and ore minerals. Porphyry-hosted and stratabound mineralization are both characterized by early-stage pyrite–chalcopyrite–sphalerite, middle-stage acanthite–native silver–galena–sphalerite, and late-stage pyrite–quartz–calcite. The δ34S values of pyrite, sphalerite, and galena in the ores range from ?3.8 to +6.9‰ with an average of +2.0‰. The C–O isotope values of siderite, calcite, and dolomite range from ?7.2 to ?1.5‰ with an average of ?4.4‰ (V-PDB) and from +10.9 to +19.5‰ with an average of +14.8‰ (V-SMOW), respectively. Hydrogen, oxygen, and carbon isotopes indicate that the hydrothermal fluids were derived mainly from meteoric water, with addition of minor amounts of magmatic water. Geochronology employing LA–ICP–MS analyses of zircons from a quartz syenite porphyry yielded a weighted mean 206Pb/238U age of 136.3?±?0.8 Ma considered as the emplacement age of the porphyry. Rb–Sr dating of sphalerite from the main ore stage yielded an age of 126.9?±?7.1 Ma, marking the time of mineralization. The Lengshuikeng mineralization classifies as an epithermal Ag–Pb–Zn deposit. 相似文献
16.
Leyla Kalender 《Journal of African Earth Sciences》2011,59(4-5):341-348
Pb–Zn deposits are widespread and common in various parts of the Taurus Belt. Most of the deposits are of pyrometasomatic and hydrothermal origin. The Keban Pb–Zn deposits are located along the intrusive contact between the Paleozoic – Lower Triassic Keban Metamorphic Formation and the syenite porphyry of the Upper Cretaceous Keban igneous rocks. Various studies have already been carried out; using fluid inclusion studies on fluorite, calcite and quartz on the pyrite–chalcopyrite bearing Keban ore deposits. This study focuses on the interpretation of stable isotope compositions in connexion with fluid inclusion data. Sulphur isotope values (δ34S) of pyrite are within the range of ?0.59 to +0.17‰V-CDT (n = 10). Thus, the source of sulphur is considered to be magmatic, as evidenced by associated igneous rocks and δ34S values around zero“0”. Oxygen isotope values δ18O of quartz vary between +10.5 and +19.9‰(SMOW). However, δ18O and δ13C values of calcite related to re-crystallized limestone (Keban Metamorphic Formation) reach up to +27.3‰(SMOW) and +1.6‰(PDB), respectively. The δ34S, δ13C and δ18O values demonstrate that skarn-type Pb–Zn deposits formed within syeno-monzonitic rocks and calc-schist contacts could have developed at low temperatures, by mixing metamorphic and meteoric waters in the final stages of magmatism. 相似文献
17.
Multiple sulfur isotope ratios （^34S/^33S/^32S） of Archean bedded sulfides deposits were measured in the Yanlingguan Formation of the Taishan Group in Xintai, Shandong Province, East of China; 633S = -0.7%o to 3.8‰,δ^34S = 0.1‰-8.8‰, △^33S = -2.3‰ to -0.7‰. The sulfur isotope compositions show obvious mass-independent fractionation （MIF） signatures. The presence of MIF of sulfur isotope in Archean sulfides indicates that the sulfur was from products of photochemical reactions of volcanic SO2 induced by solar UV radiation, implying that the ozone shield was not formed in atmosphere at that time, and the oxygen level was less than 10-5 PAL （the present atmosphere level）. The sulfate produced by photolysis of SO2 with negative △^33S precipitated near the volcanic activity center; and the product of element S with positive △^33S precipitated far away from the volcanic activity center. The lower △^33S values of sulfide （-2.30‰ to --0.25‰） show that Shihezhuang was near the volcanic center, and sulfur was mostly from sulfate produced by photolysis. The higher △^33S values （-0.5‰ to -‰） indicate that Yanlingguan was far away from the volcanic center and that some of sulfur were from sulfate, another from element S produced by photolysis. The data points of sulfur isotope from Yanlingguan are in a line parallel to MFL （mass dependent fractionation line） on the plot of δ^34S--δ^33S, showing that the volcanic sulfur species went through the atmospheric cycle into the ocean, and then mass dependent fractionation occurred during deposition of sulfide. The data points of sulfur isotope from Shihezhuang represent a mix of different sulfur source. 相似文献
18.
The Paleozoic Ozbak-Kuh carbonate-hosted Pb-Zn deposit of East Central Iran: Isotope (C,O, S,Pb) geochemistry and ore genesis 总被引：1，自引：0，他引：1
Farhad Ehya 《Mineralogy and Petrology》2014,108(1):123-136
Lead and zinc mineralization occurs in dolostones of the Middle Devonian Sibzar Formation at Ozbak-Kuh, which is located 150 km north of Tabas city in East Central Iran. The ore is composed of galena, sphalerite and calcite, with subordinate dolomite and bitumen. Wall-rock alterations include carbonate recrystallization and dolomitization. Microscopic studies reveal that the host rock is replaced by galena and sphalerite. The Pb–Zn mineralization is epigenetic and stratabound. The δ13C values of hydrothermal calcite samples fall in the narrow range between ?0.3‰ and 0.8‰. The δ18O values in calcite display a wider range, between ?14.5‰ and ?11.9‰. The δ13C and δ18O values overlap with the oxygen and carbon isotopic compositions of Paleozoic seawater, indicating the possible important participation of Paleozoic seawater in the ore-forming fluid. The δ18O signature corresponds to a spread in temperature of about 70 °C in the ore-bearing fluid. The δ13C values indicate that the organic materials within the host rocks did not contribute significantly in the hydrothermal fluid. The δ34S values of galena and sphalerite samples occupy the ranges of 12.2‰–16.0‰ and 12.1–16.8‰, respectively. These values reveal that the seawater sulfate is the most probable source of sulfur. The reduced sulfur was most likely supplied through thermochemical sulfate reduction. The sulfur isotope ratios of co-precipitated sphalerite–galena pairs suggest that deposition of the sulfide minerals took place under chemical disequilibrium conditions. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of the galena samples represent average values of 18.08, 15.66, and 38.50, respectively. These ratios indicate that galena Pb likely originated from an orogenic source in which supracrustal rocks with high 238U/204Pb and 232Th/204Pb ratios are dominant. The average lead isotope model age portrays Cambrian age. This model age is not coeval with the host rocks, which are of middle Devonian age. It is probable that the pre-Middle Devonian model age shows the derivation of Pb from older sources either from host rocks of Cambrian age or from deposits previously formed in these rock units. The Pb isotopic composition of galena accords with the occurrence of an orogenic activity from Late Neoproterozoic to Lower Cambrian in Central Iran. The proposed genetic model considers the fact that mineralization formed in fractured and brecciated host rocks along shear zones and faults from metal-bearing connate waters that were discharged due to deformational dewatering of sediments. 相似文献
19.
Fourteen stratiform, stratabound and vein-type sulphide occurrences in the Upper Allochthon of the Central–North Norwegian Caledonides have been studied for their sulphur, oxygen and hydrogen isotope composition. Depositional ages of host rocks to the stratabound and stratiform sulphide occurrences range from 590 to 640?Ma. The sulphides and their host rocks have been affected by polyphase deformation and metamorphism with a peak temperature of 650?°C dated to 432?Ma. A total of 104 sulphide and 2 barite samples were analysed for δ34S, 16 whole-rock and quartz samples for δ18O and 12 samples of muscovite for δD. The overall δ34S values range from ?14 to +31‰ with the majority of sampled sulphides lying within a range of +4 to +15‰. In most cases δ34S within each hand specimen behaves in accordance with the equilibrium fractionation sequence, δ34Sgn<δ34Scp<δ34Ssph<δ34Spy. A systematic increase in δ34S from the vein sulphides (?8‰) through schist/amphibolite-hosted (+6‰) and schist-hosted (+7 to +12‰) to dolomite-hosted (+12 to +31‰) occurrences is documented. The δ34S averages of the stratiform schist-hosted sulphides are 17 to 22‰ lower than in the penecontemporaneous seawater sulphate. The Bjørkåsen (+4 to +6‰) occurrence is a volcanogenic massive sulphide (VMS) transitional to sedimentary massive sulphide (SMS), exhalative, massive, pyritic deposit of Cu–Zn–Pb sulphides formed by fluids which obtained H2S via high-temperature reduction of seawater sulphate by oxidation of Fe2+ during the convective circulation of seawater through underlying rock sequences. The Raudvatn, volcanic-hosted, disseminated Cu sulphides (+6 to +8‰) obtained sulphur via a similar process. The Balsnes, stratiform, ‘black schist’-hosted, pyrite–pyrrhotite occurrence (?6 to ?14‰) is represented by typical diagenetic sulphides precipitated via bacteriogenic reduction of coeval (ca. 600?Ma) seawater sulphate (+25 to +35‰) in a system open to sulphate supply. The δ34S values of the Djupvik–Skårnesdalen (+7 to +12‰), Hammerfjell (+5 to 11‰), Kaldådalen (+10 to +12‰) and Njallavarre (+7 to +8‰) stratiform, schist-hosted, massive and disseminated Zn–Pb (±Cu) sulphide occurrences, as well as the stratabound, quartzite-hosted, Au-bearing arsenopyrite occurrence at Langvatnet (+7 to +11‰), suggest that thermochemically reduced connate seawater sulphate was a principal sulphur source. The Sinklien and Tårstad, stratabound, dolomite- and dolomite collapse breccia-hosted, Zn (±Cu–Pb) sulphides are marked by the highest enrichment in 34S (+20 to +31‰). The occurrences ?are?assigned to the Mississippi-Valley-type deposits.?High δ34S values require reduction/replacement of contemporaneous (ca. 590?Ma) evaporitic sulphate (+23 to +34‰) with Corg-rich fluids in a closed system. The Melkedalen (+12 to +15‰), stratabound, fault-controlled, Cu–Zn sulphide deposit is hosted by the ca. 595?Ma dolomitised Melkedalen marble. The deposit is composed of several generations of ore minerals which formed by replacement of host dolomite. Polyphase hydrothermal fluids were introduced during several reactivation episodes of the fault zone. The positive δ34S values with a very limited fractionation (<3‰) are indicative of the sulphide-sulphur generated through abiological, thermochemical reduction of seawater sulphate by organic material. The vein-type Cu (±Au–W) occurrences at Baugefjell, Bugtedalen and Baugevatn (?8 to ?4‰) are of hydrothermal origin and obtained their sulphur from igneous sources with a possible incorporation of sedimentary/diagenetic sulphides. In a broad sense, all the stratiform/stratabound, sediment-hosted, sulphide occurrences studied formed by epigenetic fluids within two probable scenarios which may be applicable separately or interactively: (1) expulsion of hot metal-bearing connate waters from deeper parts of sedimentary basins prior to nappe translation (late diagenetic/catagenetic/epigenetic fluids) or (2) tectonically driven expulsion in the course of nappe translation (early metamorphic fluids). A combination of (1) and (2) is favoured for the stratabound, fault-controlled, Melkedalen and Langvatnet occurrences, whereas the rest are considered to have formed within option (1). The sulphides and their host rocks were transported from unknown distances and thrust on to the Fennoscandian Shield during the course of the Caledonian orogeny. The displaced/allochthonous nature of the Ofoten Cu–Pb–Zn ‘metallogenetic province’ would explain the enigmatically high concentration of small-scale Cu–Pb–Zn deposits that occur only in this particular area of the Norwegian Caledonides. 相似文献
20.
Large rounded pyrite grains (>1 mm), commonly referred to as “buckshot” pyrite grains, are a characteristic feature of the auriferous conglomerates (reefs) in the Witwatersrand and Ventersdorp supergroups, Kaapvaal Craton, South Africa. Detailed petrographic analyses of the reefs indicated that the vast majority of the buckshot pyrite grains are of reworked sedimentary origin, i.e., that the pyrite grains originally formed in the sedimentary environment during sedimentation and diagenesis. Forty-one of these reworked sedimentary pyrite grains from the Main, Vaal, Basal, Kalkoenkrans, Beatrix, and Ventersdorp Contact reefs were analyzed for their multiple sulfur isotope compositions (δ34S, Δ33S, and Δ36S) to determine the source of the pyrite sulfur. In addition, five epigenetic pyrite samples (pyrite formed after sedimentation and lithification) from the Middelvlei and the Ventersdorp Contact reefs were measured for comparison. The δ34S, Δ33S, and Δ36S values of all 41 reworked sedimentary pyrite grains indicate clear signatures of mass-dependent and mass-independent fractionation and range from ?6.8 to +13.8?‰, ?1.7 to +1.7?‰, and ?3.9 to +0.9?‰, respectively. In contrast, the five epigenetic pyrite samples display a very limited range of δ34S, Δ33S, and Δ36S values (+0.7 to +4.0?‰, ?0.3 to +0.0?‰. and ?0.3 to +0.1?‰, respectively). Despite the clear signatures of mass-independent sulfur isotope fractionation, very few data points plot along the primary Archean photochemical array suggesting a weak photolytic control over the data set. Instead, other factors command a greater degree of influence such as pyrite paragenesis, the prevailing depositional environment, and non-photolytic sulfur sources. In relation to pyrite paragenesis, reworked syngenetic sedimentary pyrite grains (pyrite originally precipitated along the sediment-water interface) are characterized by negative δ34S and Δ33S values, suggesting open system conditions with respect to sulfate supply and the presence of microbial sulfate reducers. On the contrary, most reworked diagenetic sedimentary pyrite grains (pyrite originally precipitated below the sediment-water interface) show positive δ34S and negative Δ33S values, suggesting closed system conditions. Negligible Δ33S anomalies from epigenetic pyrite suggest that the sulfur was sourced from a mass-dependent or isotopically homogenous metamorphic/hydrothermal fluid. Contrasting sulfur isotope compositions were also observed from different depositional environments, namely fluvial conglomerates and marine-modified fluvial conglomerates. The bulk of the pyrite grains from fluvial conglomerates are characterized by a wide range of δ34S values (?6.2 to +4.8?‰) and small Δ33S values (±0.3?‰). This signature likely represents a crustal sulfate reservoir derived from either volcanic degassing or from weathering of sulfide minerals in the hinterland. Reworked sedimentary pyrite grains from marine-modified fluvial conglomerates share similar isotope compositions, but also produce a positive Δ33S/δ34S array that overlaps with the composition of Archean barite, suggesting the introduction of marine sulfur. These results demonstrate the presence of multiple sources of sulfur, which include atmospheric, crustal, and marine reservoirs. The prevalence of the mass-dependent crustal sulfur isotope signature in fluvial conglomerates suggests that sulfate concentrations were probably much higher in terrestrial settings in comparison to marine environments, which were sulfate-deficient. However, the optimum conditions for forming terrestrial sedimentary pyrite were probably not during fluvial progradation but rather during the early phases of flooding of low angle unconformities, i.e., during retrogradational fluvial deposition, coupled in some cases with marine transgressions, immediately following inflection points of maximum rate of relative sea level fall. 相似文献