Composition characteristics and indicative significance of chlorites in the Shulouqiu deposit,northern Guangdong
Chloritization is a typical middle-low temperature hydrothermal alteration type of early ore-forming stage in Shulouqiu deposit of Changjiang rock mass in southern Zhuguang.In this paper,the chlorite in the horizontal al-teration zone around the ore body are studied comprehensively by optical microscopy,electron probe and scanning electron microscopy.Based on the lithological characteristics and genesis of chlorite,they are divided into five types:fissure filling chlorite,biotite altered chlorite,feldspar altered chlorite,dolomite altered chlorite and spheri-cal chlorite.The five types of chlorite are all trioctahedral iron-rich chlorite with the same structure type,belonging to three species:vermicular chlorite,ferromagnesian chlorite and uraninite chlorite.Then,the five types of chlorite may have formed in the same period of fluid action in the early ore-forming period,with the formation temperature between 219～282℃ and logfO2 between-47.74～-43.69.Combined with previous research results in the region,the early ore-forming fluid may be a crust-mantle mixed fluid dominated by mantle-derived materials,with strong reducibility.Its formation is related to the intrusion of regional basic veins,which provides a reducing field for the mineralization system,resulting in the reduction and precipitation of U6+in the ore-forming fluid.
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