C-S-Pb isotope geochemistry of the Yindonggou orogenictype silver deposit in Henan province
河南银洞沟造山型银矿床碳硫铅同位素地球化学

The Yindonggou silver(poly-metals)deposit,a large fault-controlled lode deposit in Neixiang County,Henan province,occurs in the Erlangping Terrane,northern East Qinling Orogen.The host-rocks are the lava-clastic assemblage of Erlangping Group.The occurrences of ore bodies were controlled by the subsidiary fault of Zhu-Xia fault and located in the faulted structure belt.All of the characteristics of the ore texture,mineral assemblage,the type and zonation of wall-rock alternation are similar to those of the orogenictype gold deposits as summarized by previous studies,which suggests it to be a typical orogenic-type silver deposit.The δ~(34)S values of the ore minerals are,+4.7～+8.1‰,higher than those of organic matter and magmatic rock.The δ~(13) C_(CO2) values of its ore-fluids vary from-0.2 to+0.9‰,which is consistent with marine carbonate and higher than all of other geologic bodies.The ore minerals have a uniform lead isotope compositions,with ~(206)Pb/~(204) Pb = 18.2026～18.4462,~(207)pb/~(204) Pb = 15.5835～15.7739,and ~(208)Pb/~(204)Pb = 38.5478～39.0890,indicating the richness in U-radioactive Pb and little lack of Th-radioactive Pb.The C-S-Pb isotope geochemistry suggests that the sedimentary formation of carbonate-clastic rock with sedimentary sulfate interbed was the most ideal source that provided the ore-forming fluid and materials to the Yindonggou deposit.This paper deduced that the metallogenic materials and fluids were mainly sourced from the Erlangping and Qinling groups,especially the Yanlinggou Formation of Qinling Group that consists of carbonate strata.During the collisional orogenesis process of the North and South China Cratons in Mesozoic,the Qinling Group northward underthrusted and located beneath the Erlangping terrane along the Zhu-Xia fault,and provided lots of oreforming materials and fluid to the Yindonggou deposit via metamorphic dehydration.In the north of Zhu-Xia fault,there were the Yindonggou Ag deposit,Xuyaogou Au deposit,Songduo buried granite pluton,Luanchuan porphyry Mo ore belt in turn,and such zonation is totally consistent with the Tectonic Model of Collisional Orogeny,Metallogeny and Fluid Flow(CMF model),which proves not only the CMF model is scientific and applicative but also the isotope geochemistry is effective to trace the source of metallogenic material and fluid.Additionally the discovery and study result of the Yindonggou Ag deposit approve the forecast is right that there was the Sangping-Miping-Xuyaogou Cu-Au-Pb-Zn-Ag ore belt in the north of Zhu-Xia fault,thus this belt should be a key area in silver poly-metals exploration.