| The Dongchuan lead-zinc deposit is located in the Fengxian-Zhenanlu Terrigenous basin,that belongs Sourthern Qinling Orogenic Belt of the Qinling-Dabie Neoproterozoic-Mesozoic Orogenic Belt in the Yangtze Plate.The ore-bearing strata are from Cambrian to Shiwengzi Formation of Ordovician.The major rock assemblages are thick layered to massive structured dolomite with microcry stalline structure or fine grained structure,containing a small amount of banded and crumby firestone,is partially mingled with algal layer and contains argillaceous stripes(bands).The ore bodies appear to be lamellar,veined,lumpy,lenticular,expansion and shrinkage,end to end alignment.The ore body mainly occurs in the second member of the Shiwengzi Formation in light gray to gray dolomite.Hydrothermal alterations in the mining area are widespread,mainly including silicification,pyritization,tremolitization and carbonation.Silicification,pyritization and tremolitization are closely related to lead and zinc mineralization.The main metal minerals of lead-zinc ore are sphalerite,galena and pyrite,and the oxidation minerals are mainly galite and smithsonite.The ore texture includes is xenomorphic-granular texture,metasomatic texture,and residual texture,and the ore structure is layered structure,massive structure,vein-like structure,vein network structure,and scattered structure.The types of lead ore include: primary lead-zinc ore and a small amount of lead-zinc oxide ore.Geochemical characteristics indicate that the most suitable Lead and Zinc mineralization geochemistry condation in the Upper Cambrain-Shiwengzi Formation of Middle Ordovician.Its geochemical characteristics are accodant with the knowned Lead and Zinc mineralization distribution characteristics in the strata.The Lead,Zinc anomalies are strong intensity,large scale,and with a significant three-level concentration banding,showing the characteristics of the main mineralized elements.According to regional geological characteristics and tectonic evolution,this deposit is considered to be the evolutionary stage of the Late Indosinian to Early Yanshanian orogenic belt in the marginal basin of the South Qinling Mountains.The Low-Middle temperature magmatic hydrothermal veined lead-zinc deposit is controlled by the multiple geological factors such as faults and Late Triassic tectonic magmatism.The distribution of orebodies(veins)in each ore deposit in the Dongchuan lead-zinc deposit is mainly controlled by the northeast to north-northeast fault and the interlaminar fissures on both sides of the dolomite.Hydrothermal deposits are mainly formed by hydrothermal filling,and lead-zinc mineralization is mainly characterized by hydrothermal(quartz)veins.The prediction of ore-prospecting is conducted in the study area,and 2 lead-zinc metallogenic prospects were delineated at all levels,including grade I prospective area,named the Xiaochuanxigou-Dajiaogou PbZn ore prospecting area(I1);grade II ore prospecting area,named the PbZn ore prospecting area(II1)in the Siyuangou-Yindonggou. |
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