| Gala Gold Deposit,lying in Ganzi-Litang fault zones in the eastern margin of Sanjiang Tethys,along with Xionglongxi,Ajialongwa,Xichonglong and Qukailongwa gold deposits/occurrences,constitutes an important metallogenic belt in western Sichuan.On the basis of previous research results and field investigations,the natures,origins and evolutions of mineralizing fluids are analyzed by fluid inclusion geochemistry studies,and the distributed characteristics of ore-forming elements are researched according to the element geochemistry of strata,magmatites and ores.In addition,H-O,C and S isotope values of mineral fluids,ores,and host rocks are tested,based on which the origins of ore-forming materials and fluids and mineralizing epoch are determined.Finally,in light of comprehensive discussions,we discuss the mineralizing processes of Gala Gold Deposit.Results are as follows:Gala Gold Deposit is suited in the transition portion of NW-SN direction in the northern section of Ganzi-Litang bonding zone,in which the characteristics of ductile shear deformations and hydrothermal alterations are very obvious,ore-bearing strata are upper Triassic Qugasi Formation,and ore bodies are mainly controlled by NW trending faults.The homogenization temperatures of mineral fluids concentrates between 180 and 240?,with salinities varying from 1.2 to 6.1 wt%NaCl,and densities ranging from 1.83 to 0.97 g/cm3,belonging to middle-low temperature and low salinity fluid systems.Fluid compositions and C and H-O isotope characteristics indicate sedimentary-metamorphic water origins,with some meteoric waters mixing in them in the late mineralizing period.C,S and Pb isotope and element geochemistry analysis show ore-forming materials are mainly originated from host rocks(strata).Furthermore,Upper Triassic Qugasi Formation is an indispensible ore-forming material base of Gala Gold Deposit.Gala Gold Deposit,whose ore-forming epoch changes from 170 to 150Ma,forms in a compression turning to extension systems tectonic setting in Yidun island-arc continent-continent collisional orogeny. |
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