Re-Os dating of bitumen in the giant Jinding Zn-Pb deposit,Yunnan and its geological significance

Oil-gas reservoirs and metal deposits often co-exist in many sedimentary basins,and their genetic relations have been paid much attention.The Jinding Zn-Pb deposit,Yunnan,China,is so far the largest Zn-Pb deposit in China,the youngest and only giant Zn-Pb deposit hosted in continental sedimentary rocks in the world.Bitumen and heavy oil were often observed in the Jinding ZnPb deposit.It has been a subject of debate whether the bitumen formed before or after the Zn-Pb mineralization,making it difficult to evaluate and the genetic relationship between the bitumen and Zn-Pb mineralization.The bitumen in the Jinding Zn-Pb ores hosted in the breccia-bearing sandstones and sandy breccias of the Paleocene Yunlong Formation has been dated by the Re-Os method in this paper,and an isochron age of 68 ± 5Ma(MSWD = 9.2,n = 6) has been obtained.Therefore,the oil-gas reservoir in the Jinding ore district was formed earlier than the Zn-Pb mineralization.The hydrocarbons in the reservoirs may have provided the condition for the production of reduced sulfur required for Zn-Pb mineralization through thermal chemical reduction of sulfates.The formation of the oilgas reservoir and the Zn-Pb deposit may have been a continuous geologic process,and the oil-gas reservoir was one of the basic conditions of Zn-Pb mineralization in the Jinding ore district.The oil-gas reservoir was destructed by the mineralization process.