Study On Ore Fabric Of Sifangshan Copper Polymetallic Deposit In Baiyinchang,Gansu Province

Sifangshan Copper Polymetallic deposit,located between Zheyaoshan and Xiaotieshan copper polymetallic deposit,is a concealed ore deposit which is found in the Baiyinchang Orefield in 2013.The deposit is located in the eastern part of the northern Qilianshan fold zone.According to the study on geological features of the deposit,drill core record compiling,sampling,sample handling,microscope examining,electronic probe testing and other testing methods,we study on the fabric and mineral characteristics and drew conclusions?There are four major ore structures about the ore,including sparse disseminated structure,dense disseminated structure,mesh-vein structure and massive structure.The principal textures of ore are metasomatic texture,crystalline texture and pressure texture.The main ore minerals are pyrite,sphalerite,galena,chalcopyrite,and the main gangue minerals are quartz,plagioclase,chlorite,sericite,calcite.According to analyzing ore fabric,typomorphic minerals and typomorphic texture,this deposit has volcanogenic endogenic deposit characteristics.Ore-forming fluids range from high sulphidation to medium sulphidation to low sulphidation types with shallow sea turning to deep sea zone.Sifangshan copper polymetallic deposit has the characteristics of high oxygen fugacity before the stage?of hydrothermal phase.Fractures in minerals develop in all the hydrothermal mineralization periods and provide space for ore-forming fluids migrating and depositing,which shows that tectonic stress is related to mineralization.The results of study on typomorphic minerals features in all the hydrothermal stages show that the temperature or mineralization process ranges from medium and low temperature to high temperature to medium and low temperature,and meanwhile minerals crystallization period increases in the ore-forming processes.According to the field occurrence of ore samples,mineral assemblage and the vein intercalating relationships,this metallogenic process of deposit experiences multiperiod hydrothermal process and tectonic superimposition and reworking.We conclude that Sifangshan copper polymetallic deposit is a hydrotherm filling and metasomatic deposit with tectonic superposition and reworking and favorable geological prospecting conditional is interior ore body,lithology transferring interface and other structures.