Petrological Characteristics And Geochemistry And Genesis Of The Black Talc Deposit In Guangfeng County,Jiangxi Province

China’s talc mines are rich in resources and excellent in quality,and are the dominant minerals in China’s non-metallic mines,and their distribution is relatively concentrated,there are a lot of talc resources in Liaoning,Shandong,Jiangxi and other places in China.Xujiaqiao black talc non-metallic ore section is located in Xujiaqiao,Guangfeng District,Shangrao City,Jiangxi Province,east of the Beiwuyi metallogenic belt.Based on the field geological survey,this paper carried out research on the petrological characteristics,rock geochemical characteristics and mineral chemical characteristics of the Guangfeng talc mine,discussed the genesis of the talc mine,and obtained the following achievements and understanding:1.The Guangfeng black talc deposit is mainly exposed in the Upper Sinian Dengying Formation,a color ranging from black to dark gray,with lepidoblastic texture,metasomatic relict texture and crumb structure,the structure is mainly breccia structure,lamellar structure,deformed breccia structure,the main mineral composition is talc,dolomite and quartz.2.The surrounding rock of the talc deposit is dolomite,and the top and bottom plates are siliceous rocks.Near the bottom plate,talc is used as a filler to fill the siliceous cracks;and near the top plate,the silica begins to replace talc and gradually becomes silicon rock.3.Talc is not an olitic structure,but a breccia structure formed by tectonic action.Siliceous later filled in the cracks of breccia4.Through electron probe analysis,a large amount of talc and magnesite were found inside the breccia,indicating that talc is formed by basic-ultrabasic rocks under the combined action of hydrothermal fluids containing CO₂ and hydrothermal fluids containing SiO₂.Rock geochemistry features show that talc deposits were formed in an island arc environment.5.The average element Fe/Ti of siliceous rock is 41.95,the average value of（Fe+Mn）/Ti is 43.67,the average value of Al/（Al+Fe+Mn）is 0.21;the average value of trace element U/Th is 1.23;The rare earth elementδCe is negative anomaly,andδEu is a positive anomaly;indicating that the siliceous rock is a hydrothermal origin.