Study Of Fluid Inclusions In The Daruoluolong Sharn Copper Deposit,Tibet

A newly discovered deposit,Daruoluolong skarn copper deposit,is the first Late Jurassic skarn Cu deposit,which is located in the northern margin of the central section of the Bangong-Nujiang metallogenic belt.The Daruoluolong deposit is located at the Cuozheluoma town in Shuanghu count,Tibet.In order to understand the characteristics of the ore-forming fluids and metallogenesis of the Daruoluolong sharn copper deposit,petrology,micro-thermometry,and Laser Raman Spectrum studies of fluid inclusions as well as the geological futures,have been carried out in this dissertation.The Daruoluolong deposit is dominated by copper mineralization.The ore bodies are mainly hosted in skarn and skarnificated granodiorite porphyry.According to the cross cutting relationships of the veinlets combined with the ore texture,structure and mineral assemblages,the mineralization process of the Daruoluolong deposit can be divided into three stages: skarn stage,quart-sulfide stage and quartz-carbonate stage.Mineralization mainly took place in the quartz-sulfide stage.There are four types of fluid inclusions in the Daruoluolong deposit: including liquid-rich(LV),daughter mineral-bearing(LVH),vapor-rich(VL)and pure vapor(V).LV and LVH fluid inclusions are mainly present at the quartz-sulfide stage.All these two types of fluid inclusions exhibit homogenization temperatures primarily ranging from 150 ? to 350 ?,but show very different salinity peaks,varying from 10% to 23% NaCleqv and from 30% to 40% NaCleqv.The relatively late quartz-carbonate stage mainly contains LV fluid inclusions with homogenization temperatures from 150 ? to 200 ? and salinities from 5% to 10% NaCleqv.In addition,different types of fluid inclusions could be observed in one quartz grain,and show similar temperatures but different salinities,suggesting the fluid immiscility or boiling.The micro-thermometry date and hydrogen and oxygen isotopic analyses indicate that the ore-forming fluid might be originated from magmatic hydrotherm.In the quartz-sulfide stage,the ore-forming fluid experienced boiling and mixtured with the meteoric water.In summary,ore-forming fluid evolves from high temperature and high salinity to low temperature and low salinity condition,while the density change a little.In the quartz-carbonate strage,the ore-forming fluid is mixed by the meteoric water.According to our study,the decreasing of temperature,boiling and mixture by meteoric water might give rise to the precipitation of metal minerals in the Daruoluolong deposit.