Study On The Two Kinds Of Important Zinc-lead Deposits In Sedimentary Basin Of Southern Tianshan, Xinjiang

The lead and zinc resources in sedimentary basin of southern Tianshan in Xinjiang are abundant. There are two typical deposits: one is hosted in carbonate rock of late Paleozoic basins, represented by Huoshibulake and Shalitashi ore; the other is hosted in clastic rock of Meso-cenozoic basins, represented by Wulagen deposit. These deposits are important for theoretical research and economic development. Although many researches have been carried out, there are still many controversies on deposit genisis. Therefore, the understanding of the deposit is in urgent need to be improved.The deposits in Paleozoic basins are hosted by the Devonian carbonate rock. The Pb-Zn ore body,with tabular shape as well as stratiform and stratoid, controlled by the strata. The ore minerals are mainly galena and sphalerite. The mineralization shows the evident epigenetic characteristics, with a weak wall-rock alteration. The Wulagen deposit in Paleozoic basin is hosted by the lower cretaceous sandy conglomerate and Paleocene dolomite. The orebody is stratiform and stratoid in shape and the ore minerals are mainly galena and sphalerite, occurring as disseminated and vein conditions. The wall-rock alteration is also weak.The REE compositions of monomineral in Huoshibulake indicated that the mineralization is related to recrystallization of micritic limestone. The Co/Ni<1 of pyrite indicates the genesis related to sedimentary basin fluid processes.δ¹³C_V-PDB,δD_V-SMOW andδ¹⁸O_V-SMOW shows the ore-forming fluids are likely to be the pent-up water in the basin, and the CO2 in the ore-forming fluids might be related to the strata of marine carbonate. Theδ³⁴S of the sulfide in ores mostly fall in the range from 16‰to 24‰, which indicates that the sulfur derives from the marine sulfate thermal chemical reduction. The Pb-isotopic compositions and related parameters suggest that the ore-forming material should be mainly from the upper crust supported by strata.The geochemistry of ore-bearing strata in Wulagen deposit in Meso-cenozoic basin show that the ore-hosted rock types are feldspar-quartz sandstone and lithic quartz sandstone and its provenance is passive continental margin. Theδ³⁴S of the sulfide in ore mostly fall in the range from -27.9‰to 14.6‰, which indicates that the sulfur derives from the marine sulfate bacterial reduction. The lead isotope composition suggests that the ore metals were derived from the erosion source of upper crust and orogenic belt.The lead-zinc metallegenic theory and the geological and geochemical charactersitcs of typical deposit lead to the conclusion that the ore type in Paleozoic basins is Mississippi valley type. After comparing with the lead-zinc ore type, we conclude that the Wulagen deposit in Meso-cenozoic basins is sandstone type in continental sedimentary environment and the exploration of Wulagen deposit is an successful example to find giant lead-zinc deposit in Meso-cenozoic sandstone of continental sedimentary environment.