Geochemical Characteristics And Prospecting Indications Of Greenstone Minerals In Shaxi Porphyry Copper-Gold Deposit, Luzong Mineral Concentration Area, Anhui

Porphyry copper-gold deposits are important sources of copper and gold in the world.With the exploration of porphyry deposits gradually moving towards deep blind orebodies in the prospecting of porphyry deposits,weak mineralization and alteration information can not be accurately identified by traditional geochemical and geophysical techniques.Prophylitic alteration zone represents the weak hydrothermal activity in the distal end of the porphyry deposit system.Through the study of trace element geochemistry of chlorite and epidote in the porphyry deposits in magmatic arc environment,some researchers found that there was closely relationship between the variations of trace elements and the mineralization center,and established a set of prospecting model.Whether these models will be useful in the porphyry deposits system in the intracontinental setting is uncertain.It is also necessary to establish a model for the porphyry deposits system in the intracontinental setting.Shaxi porphyry copper-gold deposit,located in the northwest margin of Luzong Basin,is a typical intracontinental porphyry copper-gold deposit in the Middle and Lower Yangtze River metallogenic belt.It has a large copper-gold reserves and typical porphyry deposit alteration zonings.On the basis of previous geological studies of Shaxi porphyry copper-gold deposit,we collected systematically the epidote and chlorite samples in prophylitic alteration zone of the Fengtai Mountain,Tongquanshan Mountain and Qipanshan orebodies.Based on the detailed microscopic work,electron probe and LA-ICP-MS analysis,we found that the spatial variations of Ti,Ba,Co,Pb,Sr,Mn contents and Ti/Sr,Ti/Pb,V/Ni ratios of chlorite in the deposit can give a clearly indication.The spatial variations of Mo,Cu,Sn,Pb,Zn,Mn and Ti/Sr,Ti/Pb,Mg/Sr,V/Ni ratios of epidote can clearly indicate the mineralization center.The variations of the trace elements of epidote and chlorite in Shaxi deposit are different from that in the arc setting,which may be caused by the differences in tectonic setting,wall rocks,geochemical characteristics of ore-forming rocks and prophylitic alteration,and the evolution process of ore-forming fluid.Considering that the content of in Shaxi deposit,the content of these elements does not indicate the mineralization center.The variation characteristics of trace elements in chlorite and epidote,which may be influenced by temperature,acidity and alkalinity of fluids and redox environment,and the variation of Si,Na,K and Al of chlorite may be mainly influenced by metasomatic minerals.According to the above research,the trace element characteristics of chlorite and epidote in intracontinental porphyry deposits can also give a signal for the mineralization center,and have some similarity with the porphyry deposits in magmatic arc environment.