Mineralogical Study Of Magnetite In Xiongcun Copper (Gold) District,Tibet

Xiongcun ore concentrated area is composed of No.?,No.? and No.? orebodies and a number of mineralized bodies which have not been further prospected.Therefore,it is the only island-type porphyry copper and gold deposit in subduction period which has been prospected and evaluated in Gangdeis metallogenic belt.The study on the metallic minerals in Xiongcun ore concentrated area is still in the initial stage,and the enrichment degree of magnetite in No.? and No.? orebodies has a significant difference,but the formation mechanism of magnetite and its genesis of mineral deposit are still unclear.Based on the field geological mapping of Xiongcun ore concentrated area,the petrogeochemical profile measurement and the drilling core compilation,the magnetite of No.? ore body is selected as the main research object.Then the light thin section authentication,energy spectrum scanning,electron probe analysis and test,and microelement in-situ isotopic analysis?LA-ICP-MS?are systematically carried out,and compared with the geochemical characteristics of the magnetite minerals of porphyry copper and gold deposits in Xiongcun ore concentrated area No.? orebody and Bangong Lake-Nujiang metallogenic belt,it studied the output state and the characteristics of principal element and trace elements,and found out the genetic type of the magnetite is found out,discussed the physical and chemical conditions of coexisted hydrothermal fluid when the magnetite became crystals,and then expounded the precipitation mechanism of metallogenic substances in No.? orebody.The research progress is as follows:?1?The output status of magnetite in No.? and No.? orebodies of Xiongcun mining area and Naruo deposit was found out.?2?The mineral chemical characteristics of the magnetite were found out.?3?In terms of the genesis discrimination diagram of Ti+V-Al+Mn and Ti+V-Ni-Al/?Cr+Mn?,compared with the boundaries of the previous studies,the magnetite components of No.? and No.?orebodies in Xiongcun and Naruo formed under the background of arc magma were mainly distributed under the typical porphyry-type magnetite boundaries.?4?The crystallization temperature was an average temperature of 509.5?,and the oxygen fugacity logfO₂ was between-21.38 and-19.81.?5?The sedimentation mechanism of metallogenic substances in No.? orebody was discussed.The early biotite formed by the hydrothermal metasomatism which is rich in Fe³⁺in the early stage changed S⁶⁺in the hydrothermal fluid into S^2-,and the reducible sulfur in the hydrothermal fluid was combined with metallogenic elements such as Cu,Au and so on to be deposited,thus forming major copper-bearing mineral?chalcopyrite?in No.? ore body.?6?The chemical differences of magnetite minerals in No.? and No.? orebodies in Xiongcun mining area and Naruo porphyry copper and gold deposit in Bangong Lake-Nujiang Metallogenic Belt were compared.