| Xicheng concentrated mineralization area is located in Xihe, Chengxian and Huixian county, Gansu province, western Qinling. In the concentrated mineralization area ,there are many types of Pb-Zn-(Ag) deposits and gold deposits , it is one of bases of lead-zinc in china. In this area seafloor hydrothermal sedimentary ore deposits and hydrothermal sedimentary-rebuilded ore deposits are predominated. All lead-zinc-(silver) and gold deposits hosted in Devonian sedimentary rocks, and orebodies of seafloor hydrothermal sedimentary deposits and hydrothermal sedimentary-rebuilded deposits draped in phase with stratum.Applying System theory to study mineralized belt or concentrated area has been a hot topic recently. This paper applied new theory of modern seafloor hydrothermal sedimentary minerlization,sequence stratigraphy, mantle plume or hotspot and metallogenic series to study systematacially characteristic of geology and geochemistry of seafloor hydrothermal sedimentary deposits and hydrothermal sedimentary-rebuilded deposits and gold deposits. Begining with analysis of sequence stratigraphy of stratum ore hosted, this paper analysed structure of basin, variation of sea level and terrigenous sedimentation input rate which impacted on seafloor hydrothermal sedimentary mineralization, then through the study of characteristics of hydrothermal sedimentary rocks ,ore deposit geochemisty and geology, metallogenic series are established.Through synthetically study, some achievements are made as follows:1.Based on the application of sequence stratigraphy, for the first time the characteristics of sequence stratigraphy in the Xicheng concentrated mineralization area are discussed systematically and 13 three graded imperfect sequences of Devonian stratum are recognized.The result shows that hydrothermal sedimentary mineralized type and hydrothermal sedimentary-rebuilded mineralized type ore deposits occur in intergrade between two sequence, as well as occur in intergrade between highstand systems tract and transgressive systems tract. Main ore bodies of Changba style lead-zinc-(silver) deposit lie in transitional position from carbonate plateform fades to basin argillic and fine clastic fades, while Bijiashan style lead-zinc-(silver) deposit in the position from plateform margin shoal facies to basin argillic facies. In the interim from highstand systems tract to transgressive systems tract, faulting is violent in the basin, different kind of fluids coming from dissimilar position of lithosphere enter into synsedimentary faults served as a place fluids mixed to form ore-bearing Hydrocarbon Alkali-Fluids. The fluids upwelled to seafloor along fault thus ore-forming metals accumulated.2.This paper indicated the definition the hydrothermal sedimentary rocks.The definition is a group of especial sedimentary rocks forming at the temperature ranging from 70?to 350癈(or more high) through sedimentation and synsedimentary metasomatism in the seafloor. Many kinds of seafloor hydrothermal sedimentary rocks, such as silica rock, albitite, potassium feldspar rock,baritite, chloritite,dolomitite, tremolitite, and ankerite speckle phyllite. have been found in the sedimentary pile of Devonian in the area associated with hydrothermal sedimentary mineralization. The compositional minerals and elements are much complex and poorly differentiated, on the plot of Si-Mg and (SiO2/Al2O3)-[(CaO+-Na2O)/K2O],hydrothermal sedimentary rocks lie in intergrade place among natural sedimentary rocks or between magmatite and sedimentary rocks.Silicon isotope composition 8 30SiNBS-28 of silica rocks ranges from -0.1 to-0.6%o,indicating silicon coming from sedimentary rocks of deeplying sedimentary pile, which is consistent with research result of strontium isotope and carbon isotope. The result of study of geology and geochemistry indicates that forming manner is exogenous, but compositions mainly comes from deep part of lithosphere.3.Acceding to geological characteristics of ore deposits and the mode of mineralization, deposits of lead...
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