Analysis Of Ore-controlling Factors Of Datongchang Copper Deposit In Huili, Sichuan

The Datongchang copper deposit in Huili county of Sichuan province is an important medium copper deposit in Southwest China. It is located in the central section of the Sichuan Yunnan north-south tectonic belt and the South West of Huili Mesozoic fault basin. on the basis of extensive collection of former data, The author investigated the lithological association, sedimentary formation, tectonic characteristics of the copper deposit, entered the underground openings workings, the level, the chamber,the selective smelting plant and the tailings reservoir to obtain the first-hand research data, and then through the comprehensive analysis of the indoor, in-depth understanding of the metallogenic geological background and geological characteristics of the deposit, presents some views about the mineralization controlling factors, and some points of the previous proposed amendments.The Huili Datongchang copper deposit is produced in the Xiaobazu strata of late cretaceous in the Mesozoic, the lithology is a set of stratigraphic about the fluvial facies clastic sedimentary rocks, it is mainly the middle-fine conglomerate and middle-fine-grained debris-feldspar sandstone. The color is mainly purple red, include a few gray green belts. The mining area’ fold structures are mainly Qingwajia anticline and syncline, near north and south. The faults are not developed, which have found only in the northwest corner and have less impact on the orebody. The ore bodies are layered, stratoid and assumes the imbricate arrangement to the east; plane is lotus root shaped, the extension direction is north-south direction. The major primary metal minerals of ore are chalcocite and bornite, and the secondary metal mineral is malachite, mainly allotriomorphic granular texture and disseminated gum structure, no obvious surrounding rock alteration phenomena. The macroelement- microelement and sulfur isotopic data of the ore and surrounding rock indicate, ore and surrounding rock macroelement and microelement composition and content fit very high, suggest that the ore-forming materials directly come from the surrounding rock; sulfur isotope composition characteristics show that sulfur is mainly come from microbial bacteria of sulfate reduction and organic matter reduction.In the study of the main ore controlling factors of the deposit, the author found: coal, copper, salt three-color formation control the formation of sandstone copper deposits obviously; ore bodies are mainly distributed in the high permeability sandstone which is closed by the upper and lower water-resisting layer; deposit is strictly controlled by strata, Xiaobazu glutenite formation is the target layer; ore bodies occur mainly in the transition contact of gray rock and purple rock; the porosity, particle size fractions, cement components are closely related to the mineralization; the character and direction of the groundwater control the precipitation and the ore bodies distribution direction; through the analysis of the rock facies discovered riverbed retention deposit and channel bar deposit form a lithological combination which is helpful to the groundwater transfusion later; the regional geological evolution control the fault basin and source of ore-forming material; the fracture open up the channel of fluid migration, which play a important role in the formation of the ore-forming fluids; The Qingwajia anticline plays a key role on the enrichment of the ore body in the reform mineralization period.Finally, the author proposes that the deposit is a sedimentary-diagenesistransformation type sandstone copper deposit. The mineralization has experienced tectonic movements stages before the mineralization, the ore source layer deposition stage, reforming mineralization stages and surface oxidation of four stages, and makes a brief illustration of the metallogenic model of the reforming mineralization stages.