Genesis And Exploriation Of The Mazhanshan Copper Deposit,Lishui County,Jiangshu Province

Mazhanshan is located southeastern of Lishui vocalnic-sedimentary basin in lower Yangtze region,and is considered to be a small scale polymetallic deposit.Ore geology and geochemistry of this deposit is poorly constrained and seriously restrict the regional ore exploration.Based on detailed field observation and mineral texture-structure identification,in combination with fluid inclusions study,the genetic type of this deposit is determined.Prospect attestation on the new prospecting targets was also conducted according to geophysical and geochemical techniques.This deposit is hosted by continental volcanic rocks including rachyandensite,breccias-bearing trachyandensite and breccias-bearing tuff-lava.The copper ore bodies occur as vein and lenticular shapes which is apparently controlled by approximate EW and NE trend faults.Based on ore minerals texture-structure investigation under the microscope,ore minerals are dominated by chalcopyrite and pyrite,secondly bornite and hematite,minor galena and sphalerite.Gangue minerals mainly consist of quartz,barite and calcite.Ore structure occur as vein,veinlet,and stock-work,minor disseminate and lumpy.Ore texture is dominanted by euhedral-anhedral grain,radial and filling texture,minor metasomatic texture.Fluid inclusions in quartz and barite associated with copper mineralization have been selected for petrographical observation and mico-thermometry in this study.The results indicate that these fluid inclusions are two-phases aqueous fluid inclusions of NaCl-H2O system with low to moderate temperature and low salinity.The study on the ore-froming fluid suggests an evolution trend of a mixture of initial magmatic water and meteoric water.In combination with the results of geology and geochemistry,the Mazhanshan copper deposit is an epithermal deposit hosted by continental vocalnic rocks.By using geophysical and geochemical techniques,good effects on ore exploration were obtained through prospect attestation of the new prospecting targets,indicating a good ore potential in the studied region.