Genetic relationship between the Maoping Pb-Zn deposit and paleo-oil reservoir in the northern Yunnan-Guizhou depression: Evidence from bitumen trace elements and the in-situ sulfur isotope of pyrite associated with bitumen

The coexistence of numerous Mississippi Valley-type (MVT) Pb-Zn deposits and oil/gas reservoirs in the world demonstrates that a close genetic link between them. northern Yunnan–Guizhou depression (NYGD) is tectonic unit containing Pb–Zn deposits, paleo-oil shale gas. However, previous studies on relationship hydrocarbon accumulation mineralization have been ignored. Maoping deposit large-sized MVT NYGD where large amount solid bitumen (i.e., reservoir) occurs, it an ideal area to study lead–zinc mineralization. In this paper, pyrite associated with from Xujiazhai (discovered study) Xiaocaoba are researched. Geological observation has revealed occurs dissolution pores, fractures intercrystalline pores dolomite Upper Devonian Carboniferous. Xujiazhai, high similar Raman equivalent reflectance ( Rmc Ro%) indicates they over-mature level may be derived cracking early-accumulated crude oils. reservoir abundant Pb Zn content, indicating petroleum liquids act as transporting agents metallogenic metal elements, carrying them sites take place. source rocks provided not only oil for paleo-oil/gas reservoirs, but also portion ore metals bacterial sulfate reduction (BSR) thermochemical (TSR) processes were recorded by reservoir, which was consistent mechanism reduced sulfur formation deposit. addition, negative (−27.7‰ −5.7‰) positive (.9‰ 19.2‰) δ 34 S values those sulfide We believe evolution closely related process deposit, sulfides same sulfur. BSR phenomena could occur prior migration hydrocarbons into or low mature stage reservoir; small H 2 combined ions ancient form early subhedral, xenomorphic granular, fine-grained strawberry aggregate and/or gelatinous sphalerite. paleo-gas formed main period potentially participated mineralization; is, organic gas acted reducing agent transformed SO 4 2− upper Zaige Formation gypsum strata periphery mining TSR through TSR, providing creating environmental conditions During after transformation decoupling complexes Massive precipitation occurred during cracked reservoir.