| Ganzi-Litang gold belt is located in the junction area of Songpan-Ganzi orogenic zones and Yidun arc orogen,the gold belt is from north of Yushu in Qinghai to southward in Sichuan in a reverse S shape.The gold belt is an important gold-copper polymetallic ore belt,has discovered many medium-sized gold districts in recent years,and Ajialongwa gold deposit is one of them.In order to realize origins of ore-forming fluids and physical and chemical conditions of Ajialongwa gold deposit,this article made research on geochemistry of fluid inclusions,major and trace elements of host or ore rocks and stable isotope compositions.In addition,the article summarized the mineralization of Ajialongwa gold deposit.Research on ore-forming fluid shows that the mineralization temperature is from 121.3? to 211.7?,solinity is from 0.18 to 6.16 WNaci%,fluid density is from 0.859 to 0.968 g/cm3,mineralization pressure is from 7.22 to 18.70 MPa,and mineralization depth is from 0.27 to 0.69 Km,in conclusion,Ajialongwa gole deposit is a gold deposit of low depth,low temperature,salt and Thermal fluid.It lack daughter crystal and CO2 containing inclusions,the gas phase composition of fluid inclusions gave priority to H2O,and CO2 secondaryly,while Na+,K+ and SO42-as the main liquid phase composition;8D changes between-114.968‰ and-124.243%?,?18O? changes from-1.56‰ to 1.91‰,which is less than the value of normal magma water(5‰?7‰),all of these show that underground thermal brine formed from meteoric water which have taken water-rock interaction with host rocks at shallow depth is the source of ore fluid.Research on major and trace elements shows that the host/ore rocks of Ajialongwa gold deposit have much SiO2,silication is strong,Au/Ag value is 0.01?10.56,average value is 2.09,less than the general orogenic gold deposit,Ag and As are closely related to the enrichment of Au.Analysis on fission track of apatite and zircon shows that there are four evolution atsges of the thermal history in Ganzi-Litang fracture zone.If the average geothermal gradient of orogenic belt is 35?/km,this zone uplift 3.58 Km since 200 Ma,the speed is fastest since 20 Ma,its uplift rate is 0.043 mm/a,and its uplift range is 0.86 km,Ganzi-Litang fracture zone is mainly affected by the late Himalaya orogeny.Comparing Ajialongwa gold deposit with general orogenic gold deposit,they obviously have the same basic character,but there are also many differences,so Ajialongwa gold deposit is a atypical orogenic gold deposit. |
PDF Full Text Request