Mineralization of Pb-Zn deposits in Lower Paleozoic in Xunyang basin, South Qinling

Recently,significant achievements has been obtained in the exploration of lead-zinc deposits in miner alized zones in the Silurian system in Xunyang basin of Shaanxi province.These deposits in Xunyang basin mainly locate in middle Meiziya Group and Shuanghezhen Group of Silurian,and it is controlled by stratum.The ore body is simple in shape.It is mainly layer and stratiform-like;the structure of ore is simple,with few components;alteration weak and asymmetry.The average δ³⁴S of sphal erite is 6.83‰;average δ³⁴S of galena is 5.95‰;the δ³⁴S of pyrite is 1.1‰;but averag δ³⁴S of pyritelocated in the mudst one of Silurian is 15.64‰.The sulfur is mainly from seawater.The isotopic ratio of ²⁰⁸Pb/²⁰⁴Pb are 37.93%～38.95%,²⁰⁷Pb/²⁰⁴Pb are 15.55%～15.69%.It indicates the Pb from up earth's crust.The temperature of mineral ization was from 135℃ to 297℃.The components of ore-forming fluid mainly are K⁺、Na⁺、Ca²⁺、Mg²⁺、F^-、Cl^-、SO₄^2-.The Na⁺/K⁺ ratio is less than 1;F^-/Cl^- is very low.That means ore-forming fluid comes from seawater.To sumup,the majorgenesis of Pb-Zn deposits in Lower Paleozoic in Xunyang basin is hydrothermal sedimentary mineralization.