MINERALIZATION AND ORE-FORMING FLUIDS OF THE XINTAIZI GOLD DEPOSIT IN WESTERN SICHUAN PROVINCE,CHINA
The Xintaizi gold deposit in western Sichuan is situated at the junction of the Longmenshan o-rogenic belt and the Xianshuihe ductile fault belt,making it a pivotal component of the"Guzan-Kongyu Danba"gold metallogenic area.This deposit is found within the first layer phyllite of the Lower Devonian Guiguan Group.This study investigates the characteristics of mineralization and the ore-forming fluids of the Xintaizi gold deposit using electron probe microanalysis,microthermometry of fluid inclusions,LA-ICP-MS surface scanning tests,and thermodynamic simulation of native gold ore-forming fluids.Field in-vestigations and microscopic observations reveal that the gold-bearing quartz veins in the Xintaizi gold de-posit predominantly occur within fractures of early quartz veins,with native gold primarily associated with late-stage metal sulfides such as pyrite and sphalerite.The hydrothermal processes related to mineraliza-tion can be classified into two stages:an early pyrite-quartz stage and a late native gold-polymetallic sul-fide-quartz stage.Electron probe microanalysis indicates that the fineness value of native gold ranges from 918.9 to 945.9,with high contents of Au,As,and Zn in pyrite formed during the late stage.Homogeni-zation temperature of fluid inclusions ranges from 189 to 349 ℃,with salinity between 0.6 and 13.7％Na-Cleqv,and estimated pressures ranging from 2 to 15 MPa.LA-ICP-MS scanning tests demonstrate that concentrations of As,Au,Ag,Co,Ni,Cu,Pb,Zn,Sb,and Au/Ag ratios(＞0.1)are higher in pyrite formed during the late stage,but lower in pyrite formed during the early stage.This comprehensive analy-sis sheds light on the complex mineralization processes at the Xintaizi gold deposit,contributing valuable insights for further geological and mineralogical research in similar regions.Thermodynamic simulations,based on experimental results,indicate that a decrease in temperature and an increase in oxygen fugacity are key factors promoting the precipitation of gold.The changes in gold composition may be attributed to a decrease in the temperature of the ore-bearing fluid during the late stages.The Xintaizi gold deposit is characterized by early lean-bearing quartz veins overlain by late gold-bearing quartz veins.The ore-forming fluid,characterized by H2O-NaCl,exhibits low temperature,low salinity,and low pressure conditions,suggesting that the Xintaizi deposit can be classified as a hypabyssal orogenic gold deposit.
Ganzi-Songpan orogenic beltnative goldfluid inclusionLA-ICP-MS scanning testcharac-teristics of ore-forming fluid
万方数据
维普
