Research On Fluid Inclusions And Analysis Of Metallogenic Process In Yandong Copper Deposit,East Tianshan

The Yandong copper deposit is located in Hami City,Xinjiang,in the eastern Tianshan orogenic belt,with the Dacaotan fault zone in the north and Kangguer fault zone in the south.It is an important porphyry copper deposit in the eastern Tianshan Mountains.In this paper,petrography and mineralogy observations are combined with quartz cathodoluminescence observations to accurately determine the metallogenic stage;petrographic observations of fluid inclusions in different stages of metallogenesis,fluid inclusions temperature measurement and laser Raman analysis to study the properties of ore-forming fluids and discuss the ore-forming process,the main results and understandings are as follows:There are four cathodoluminescence characteristics of Yandong copper ore:Phase I quartz emits orange-red light with extremely strong luminous intensity;Phase II quartz emits green light with low luminous intensity;Phase III quartz emits indigo light with medium luminous intensity;The IV stage quartz does not emit light.There is no obvious ring belt structure in four stages.The mineralization process of the mining area can be divided into four stages:the main mineral in stage I is pyrite,followed by chalcopyrite and magnetite,and the gangue minerals include quartz,albite,biotite,sericite and chlorite The second stage is the main mineralization stage,the main mineral is chalcopyrite,followed by pyrite and bornite,the gangue minerals include quartz,muscovite,chlorite,epidote and sericite,etc.;stage III It is a polymetallic metallogenic stage.The main mineral is molybdenite,followed by pyrite,chalcopyrite,chalcocite and sphalerite.Gangue minerals include quartz,sericite and epidote.The IV stage is late In the mineralization stage,the main mineral is pyrite with a small amount of chalcopyrite.Gangue minerals include quartz,calcite,fluorite and gypsum.The results of temperature measurement and composition analysis of fluid inclusions of quartz in the four mineralization stages are:the homogeneous temperature of the inclusions in the first stage is 302?358°C,the salinity range is 9.34?12.85 wt%Na Cl equiv.,and the mineralization depth range is 3.08?6.10km.The gas and liquid components are both H₂O;the homogenization temperature of the inclusions in the second stage is concentrated at 237?298°C,the salinity range is 6.30?9.08 wt%Na Cl equiv.,the mineralization depth range is 3.00?8.06 km,the gas and liquid phases The components are all H₂O;the homogenization temperature of the inclusions in the third stage is concentrated at 179?234°C,the salinity range is 3.39?7.45 wt%Na Cl equiv.,the mineralization depth is 0.96?2.96 km,and the gas and liquid components are mainly H₂O,and the gas inclusions Contains a small amount of CO;The homogenization temperature of the inclusions in stage IV is concentrated at 130?180°C,the salinity range is 2.24?5.26 wt%Na Cl equiv.,the mineralization depth is 0.27?0.92 km,the gas and liquid components are both H₂O.Comprehensive analysis shows that the Yandong ore-forming fluid belongs to a simple H2O-Na Cl system,and the ore-forming fluid has evolved from the early medium-high temperature and medium-high salinity to the late-stage low temperature and low salinity.The ore-forming fluid is mainly magmatic water.The initial ore-forming fluid has the characteristics of medium-high temperature and medium-high salinity.A large amount of porphyry Cu-Mo mineralization is produced in and around the center of the Yandong porphyry body,and water is generated between the fluid and the surrounding rock.Rock action,phase separation occurred during the rapid upward migration.In the main mineralization stage,as the magma gradually cools down and solidifies,the temperature and salinity of the fluid decrease,copper-bearing minerals precipitate,the rock fragments due to cooling,the static rock pressure changes to the hydrostatic pressure,and the surrounding rock changes.form.In the third stage,the temperature continued to drop,resulting in the precipitation of polymetallic minerals.In the late stage of mineralization,due to the addition of atmospheric precipitation,the metal content of the ore-forming fluid was reduced and the mineralization weakened.