Study On The Ore-Controlling Structures In Tianbaoshan Pb-zn Deposit,Huili, Sichuan

Tianbaoshan Pb-Zn ore deposits in Huili 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.In the long history of geological evolution, Tianbaoshan district experienced the development stages of Proterozoic EW-trending aulacogen and Sinian-Early Paleozoic SN-trending shelf rifting, Late Permian-the new generation of SN to the continental rift. Phanerozoic SN-trending rift superimposed on top of the EW-trending rift aulacogen,which is an across type superimposed rift system.Tianbaoshan is at the site of the EW and SN rift superimposed. And its deep structure, which with EW-trending Huili-Dongchuan mantle uplift and EW-trending fracture intersection to Tianbaoshan lithosphere determines the days Baoshan lead and zinc deep mineral rich sources.2. Various tectonic stages and the mineralization is closely related:In Proterozoic, Huili-Dongchuan EW aulacogen formed the basement structure of the Sichuan-Yunnan Guizhou region, controlling the distribution of Pb-Zn in this region; Sinian-Early Paleozoic 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 seed times, deep mantle substances upwell to supracrustal with extensional rift of lithosphere; Cenozoic lithosphere contraction and extrusion, making rift valley close the fold, ore solution gathering the case. In the fitting structure (such as turn of the anticline transverse and longitudinal jointing fracture system, fault system forming by Bedding slippage burst system and dolerite invaded) mineralization in the ore-containing shielding lithologic association.3. India-Eurasia collision caused Intracontinental pulled subduction in the combination of Longmen mountains-Anning river,which is the geodynamic origin of tectonic-magmatic-metallogenic for Tianbaoshan deposit.4.Study indicted that the geological tectonic framework in Huili Tianbaoshan mining area can be conclude that:a relatively integrated fold block which compose with nearly E-W Yi-Wanshui anticline and Laoguanfangliangzi syncline in early stage, as well as is a gentle fold trend to east west;in later stage fault block were west branch ofNN-W Yimen Turn thrust fault zone and N-S secondary fold.5.Pb-Zn orebody produced in dolomite with silicon and controlled by the the intensive joints band. And it reproduced after dying out on tendency and direction After a preliminary examination,the formation time of diabase is after the late yanshanian. The deep department of the diabase has mine and even formed orebody,but the shallow department hasn’t, known orebody formed after Yu diabase, this inferred orebody may formed in late Yanshan period-early Hi mountain period; deposit belonging to hot liquid deposit.6. Mining area constructed deformation sequence can be divided into two period: early, the EW-trending anticline of yiwanshuiniangzi and the EW-trending syncline of laoguanfangniangzi formeqd huqili-dongchuqan aulacogen in Middle Proterozoic; lately, the west branch of the NS-trending yimen fault zone formed,which can be divided into three stages:the first is the stage of forming the east-dipping normal fault wich is tensile nature; the second is the stage of forming eastward overthrust nappe and reversing to the west; the third is the sinistral strike-slip stage.7. Summarized the structural ore-controlling characteristics of Tianbaoshan lead-zinc deposit:Tianbaoshan fracture is guide mine tectonic; the fracture system of axial (vertical) joints and transverse joints, the cracked system formed by diabase emplacement and the cracked system formed by bedding decollement are ore-hosting structures;thedolomite in the upper middle of the widely developed Dengying Formation is ore strata.