Study On Diagenesis And Mineralization Of Granites Associated With Tungsten Deposits In Caledonian,Northeast Guangxi

Northeast Guangxi is located at the conjunction part of Yangtze plate and Cathaysian plate.It has undergone many tectonic cycles,and has developed many times of granitic bodies and related deposits.Especially in this area,the large area of Caledonian intermediate acid rocks and the accompanying raw tungsten polymetallic deposits are the ideal places to study the diagenesis and metallogenic mechanism of Caledonian granite.On the basis of the previous research and the project group,this paper focuses on the selection of the representative deposits of YanYing Tsui tungsten deposit,yuekosing boundary brand tungsten(copper)deposit and niangtang tungsten deposit,and discusses the diagenesis and metallogenic mechanism of granite in Caledonian and tungsten deposits in Northeast Guangxi.Based on the detailed fieldwork,this work carried out(or collected the project team)the main trace elements,rare earth elements and Sr-Nd isotopic analysis of ore-forming rock in typical mineralization areas;zircon LA-ICP-MS U-Pb Dating,microscopic temperature measurement of ore-forming fluid inclusions,etc.,explored the diagenesis and mineralization mechanism of granites associated with tungsten minerals of Caledonian flower in northeastern Guangxi and the controlling factors affecting the formation of deposits of different scales,and obtained the following achievements and understanding:(1)The Yanyingzui skarn tungsten deposit,the Yuecheng Lingjie tungsten(copper)deposit and the Niutangjie skarn tungsten deposit are all tungsten deposits formed in the Caledonian period.The diagenesis and mineralization period is 401.9 to 447.3 Ma.It is concentrated in the range of 420?435Ma and belongs to the intracontinental collision extension stage of late Caledonian.(2)The ore-forming rock masses are medium to high-silicon(w(SiO2)ranges from 65.44%to 77.51%,with an average of 72.25%),potassium-rich(w(K2O)ranges from 3.86%to 6.99%,with a mean of 5.28%),peraluminous(W(Al2O3)ranged from 11.61%to 16.36%with an average of 13.7%)in acid granites with K2O/Na2O ratios ranging from 1.16 to 44.46,all greater than 1;the aluminum supersaturation index(A/CNK)ranged from 1.01 to 1.82.The average is 1.26,all greater than 1 and belongs to peraluminous granite;trace elements are enriched in large-scale ionic lithophilic elements Rb,Th,U,depleted Ba,Sr,loss of high field strength elements Nb,Ti;rare earth element content is low,light The rare earth specific gravity rare earth fractionation degree is high,the distribution pattern is "gull type" and Eu is negatively anomalous.It has the characteristics of South China S-type granite and is a shell-type S-type granite.(3)The enrichment scale of the Caledonian tungsten deposit in northeastern Guangxi is constrained by the degree of crystallization of the magma,the evolution and participation of the fluid,and the maturity of the material in the source region.The higher the degree of evolution of the granite,the more the fluid participates in the mineralization.Sufficient,the higher the material maturity of the source area,the greater the deposit size formed.(4)The Caledonian tungsten deposit has a wide temperature range of diagenesis and mineralization,and can be formed from low temperature,medium temperature to high temperature,but mainly concentrated in the range of medium temperature and low salinity.(5)During the late Caledonian period(440?410Ma),the W-rich magma chamber was partially melted in the Palaeo-Meo Proterozoic strata with a W-rich magma chamber due to the upward emplacement of tectonic extensional magma to reach the near surface and atmosphere.Precipitation or construction of water mixing,so that the ore-forming material unloading ore-forming elements,eventually forming a deposit.