Study On The Ore-Controlling Structures In Yinchanggou-Qiluogou Pb-Zn Deposit, Ninnan, Sichuan

Yinchanggou-qiluogou Pb-Zn ore deposits in Ningnan County, Sichuan Province, which are located in Sichuan-Yunnan-Guizhou Pb-Zn polymetallic metallogenic belt in east of Kangdian earth axis in southwest of Yangtze block, are an important structurally Sichuan-Yunnan-Guizhou metallogenic belt, and thus have been capturing numerous geologists'extensive attention.Based on sufficient former researches and data, starting with foundational structure geology, analyses about how structure is controlling Pb-Zn deposits is involved in this paper from regional tectonic evolution, tectonic deformation features, characteristics of deposits, structural ore-control characteristics, orebody chronology and other aspects. Initial discussion has gain following conclusion:1.During long geological evolutionary history, Ningnan area experienced following seedtimes: EW-trending aulacogen in Proterozoic, SN-trending continental shelf rift in Sinian-early Paleozonic, SN-trending continental rift in late Permian-meso Cenozoic. Rift of different tectonic cycles and different tectonic stages develops in the same area, leading to formation of supraposition rift. SN-trending rift of Phanerozoic overlays on EW-trending aulacogen, pocessing cross-straddletype supraposition rift. Ningnan area is just located in crunode between EW-trending and SN-trending rift.2.All tectonic evolution stages have a close relationship with mineralization. Huili-Dongchuan EW-trending aulacogen of Proterozoic formed basement structure of Sichuan-Yunnan-Guizhou, which controlled the distribution of Pb-Zn ore band; SN-trending continental shelf rift of Sinian-early Paleozonic formed ore-containing shielding lithologic association good for mineralization; and during SN-trending continental rift of late Permian-meso Cenozoic and other seedtimes, deep mantle substances upwell to supracrustal with extensional rift of lithosphere; shrink and extrusion of lithosphere in Cenozoic leaded to closed folds, ore solution gathering in supracrustal formed mineralization with adequate structure such as tensional fracture, turn end, anticline ruga and so on, and reservoir-close system consisting of stratum having shielding-ore containing lithologic association.3.Our reseach shows that the primary geologic tectonic pattern in Yinchanggou-qiluogou Pb-Zn mining area presented as following: Qiluogou anticline trending near NS direction; secondary transverse and longitudinal small amplitude folds; NNW-trending, NS-trending and NNE-trending longitudinal rupture, transmeridional transverse rupture and early and late phases consequent landslide.4.Pb-Zn ore body primarily occurs in dolomite or silicified rocks; ore body is controlled NS and NNW rupture, characterizing thin out reconstruction and in both tendency and trend; research of mineralization chronology suggests that three periods'mineralization is formed primarily during brittle deformation stage since late Yanshanian; mineral deposits belongs to hydrothermal deposits.5. According to analysis , the structural deformation sequence is as following: Qiluogou anticline formed with early layer shearing→NNW- trending to fracture and thrust and longitudinal small amplitude folds,SN-trending formation→NNW- trending left lateral normal slip,SN- trending left lateral line thrust, transverse small amplitude folds→NNW- trending right lateral normal slip,NS trending small fracture left lateral normal slip→NW- trending,NE- trending and EW- trending formed, late fracture in the shear.6. Structural ore-control characteristics of Yinchanggou-qiluogou Pb-Zn deposits are summarized in the paper: Xiaojiang rupture is the ore conducting structure; secondary NS-trending and NNW-trending tensional fracture is ore blending structure; NNW-trending and near NS-trending rupture, early bedding shear fracture zone and transverse and longitudinal small anticline constitute host structure; extensively developed Dengying dolomite, Upper Sinian is the host strata.