Geological Characteristics And Genetic Mineralogy Of Gold Deposits In Dong'an-Tangwanghe Region,Heilongjiang

Dong'an-Tangwanghe Region,located in the contact zone of the Lesser Hinggan Range-Songnen block and Yichun-Yanshou geosynclinals fold belt,is accompanied with complicated geological background and large-scale gold mineralization.Different researchers have studied different aspects of the Gaosongshan,Dong'an,Tuanjiegou and Pingdingshan gold deposit,such as metallogenic geological background,mineralogenetic epoch,genesis of the deposit and so on.However,only small amounts of research work about genetic mineralogy have been carried out.Hence,systematic researches of geological characteristics of the four gold deposits and cell parameters,thermoluminescence?pyroelectricity?and composition characteristics of quartz,pyrite?marcasite or arsenopyrite?,have been carried out in this dissertation to deepen the understanding of geological characteristics of deposit and genetic mineralogic features.Furthermore,characteristics of the ore-forming fluid have been discussed and favorable mineralogy prospecting information was pointed out.Gaosongshan and Dong'an gold deposit are hosted by continental volcanic rocks and alkali-feldspar granites of the Yanshanian and orebodies all occurr as veins.Silicification,pyritization,adularization,chloritization and fluoritization are the main wall-rock alterations type.Among those,silicification and adularization has close relationship with gold mineralization.The wall rocks of Tuanjiegou gold deposit are Yanshanian Putaogou granite porphyry and early Cretaceous dacite of N ingyuancun Formation.The orebodies were controlled by porphyries and occurred mainly as vein and lenticular within the prophyries and the contact zone between prophyries and schist of the Heilongjiang Group.The wall-rock alterations primarily include silicification,pyritization,marcasite and carbonatization.The wall rock of Pingdingshan gold deposit is mainly Variscan biotite granite and orebodies occur as veins and lenticular.The wall-rock alterations primarily include silicification,pyritization and sericitization.Based on the systematic research about geological characteristics and monomineral genetic mineralo gical characteristics,comprehensive understandings about the features of ore-forming fluid they reflect have been obtained.The rare earth element?REE?and trace element characteristics of quartz and pyrite,together with the occurrence of adularia and sericite in the Gaosongshan gold deposit reflect that the ore-forming fluid is of medium-low temperature?160³20oC?,neutral and weak reducibility.Metallogenic material comes from the ore-forming volcanic rocks and metallogenic system remains relatively stable during the mineralizing process.The REE characteristics?negative Eu anomaly and no Ce anomaly?of quartz,together with the occurrence of adularia and sericite in the Dong'an gold deposit indicate that the ore-forming fluid might be a reductive fluid with nearly neutral p H.REE characteristics of quartz and marcasite and the thermoelectricity of marcasite show that the ore-forming fluid in Tuanjiegou gold deposit is of medium temperature?194²56oC?,S-rich,and oxidizability,which has close relationship with granite porphyry.Comprehensive analysis of REE features of quartz and arsenopyrite and the thermoelectricity of arsenopyrite suggest that the fluid is both of S-rich and C l-rich,and ore-forming environment is relatively reductive in Pingdingshan gold deposit.The spatial variation of cell parameters and thermoelectricity parameters(X_NPP and?)of pyrite from the Gaosongshan gold deposit shows that the west part of No.1vein has undergone relatively strong erosion,followed by its middle part.Thus,deep in the middle part of No.1 vein still has the potential for exploration.In terms of denudation in deposit,it gradually increases from the southwest part,where No.1 vein located to the northeast part,where No.2 vein located.