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期刊名称: Geofluids
Volume:15    Issue:3        Page:421-437

Thermochemical and bacterial sulfate reduction in the Cambrian and Lower Ordovician carbonates in the Tazhong Area, Tarim Basin, NW China: evidence from fluid inclusions, C, S, and Sr isotopic data期刊论文

作者: Jia L Cai C Yang H Li H Wang T

页码: 421-437
被引频次: 15
出版者: WILEY-BLACKWELL,Hindawi Limited
期刊名称: Geofluids
ISSN: 1468-8115
卷期: Volume:15    Issue:3
语言: English
摘要: Petrographic features, C , O , S , and S r isotopes were determined, and fluid inclusions ( FI ) were analyzed on various stages of vug‐ and fracture‐fillings from the C ambrian and L ower O rdovician reservoirs in the T azhong area, T arim basin, NW C hina. The aim was to assess the origin of pyrite and anhydrite and the processes affecting sulfur during diagenesis of the carbonates. Pyrite from seven wells has δ 34 S values from −22‰ to +31‰. The pyrites with low δ 34 S values from −21.8‰ to −12.3‰ were found close to fracture‐filling calcites with vapor‐liquid double‐phase aqueous fluid inclusions homogenization temperatures ( FI ‐ T h) from 55.7 to 73.2°C, salinities from 1.4wt% to 6.59wt% N a C l equiv and δ 13 C values from −2.3‰ to −14.2‰, indicating an origin from bacterial sulfate reduction by organic matter. Other sulfides with heavier δ 34 S values may have formed by thermochemical sulfate reduction ( TSR ) during two episodes. The earlier TSR in the M iddle and L ower C ambrian resulted in pyrites and H 2 S having δ 34 S values from 30 to 33‰, close to those of bedded anhydrite and oilfield water (approximately 34‰). The later TSR is represented by calcites with δ 13 C values as light as −17.7‰ and FI ‐ T h of about 120–145°C, and pyrite and H 2 S with δ 34 S values close to those of the U pper C ambrian burial‐diagenetic anhydrite (between +14.8‰ and +22.6‰). The values of the anhydrite are significantly lighter than contemporary seawater sulfates. This together with 87 S r/ 86 S r values of anhydrite and TSR calcites from 0.7091 to 0.7125 suggests a source from the underlying E diacaran seawater sulfate and detrital S r contribution. Pyrites were originated from BSR and two periods of TSR with different δ 34 S values. Free H 2 S and pyrite in the Ordovician with δ 34 S values from 15 to 23% may have been generated from the later TSR of burial‐diagenetic anhydrite by petroleum.
相关主题: bacterial sulfate reduction, anhydrite, sulfur isotopes, fluid inclusion, pyrite, carbon isotopes, thermochemical sulfate reduction, Bacterial sulfate reduction, Pyrite, Anhydrite, Thermochemical sulfate reduction, Fluid inclusion, Sulfur isotopes, Carbon isotopes, SULFUR ISOTOPE, PETROLEUM-EXPLORATION, H2S CONCENTRATIONS, KHUFF FORMATION, GEOCHEMISTRY & GEOPHYSICS, GAS-RESERVOIRS, YANGTZE PLATFORM, GEOLOGY, ANAEROBIC OXIDATION, OXYGEN ISOTOPES, REDUCING BACTERIA, EAST SICHUAN BASIN,






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