Study On Application Of Composition Thermometer Of Chlorite And The Forming Temperature Of Chlorite Of Furong Tin Deposit In Hunan

As one of the minerals which widely distribute in the nature, the chlorite composition varies greatly in different geological environment. By researching on it, pioneers established a lot of formulas which calculate the formation temperature of chlorite making use of the difference composition in different geological. Recently, these formulas are widely used in presume the ore-forming conditions, and make some contribution on the development of solid mineral deposit and the exploration of fluid mineral deposit.Taking the Furong tin deposit of Hunan for example and on the base of generalizing geological background of this tin deposit, geological characteristics of orebody, surrounding rock alteration, mineral paragenesis combination and mineral formative sequence, this paper has partitioned the mineralization periods and species of chlorite, and has studied on chemical composition and crystal-chemical characteristics of chlorite using modern testing methods. By contrasting with the homogenization temperatures of fluid inclusions in symbiotic quartz, this paper has applied the chlorite composition thermometer formula which is chose from three formulas to the Furong tin deposit of Hunan and tried to presume the mineralization condition.of Songshugou copper deposit of Xinjiang .Chlorite distributes widely in Furong tin deposit and generates form early stage to later stage. According to the mineralization and alteration stages and intergrowth combination, the chlorite can be divided into three mineralization periods. According to producing characteristic and colacobisis combination relation, chlorite can be divided into two types, one is metasomatic type, the other is filling vein type.The result of EMA manifests that the species of chlorite are leptochlorite, chamoisite and brunsvigite in this deposit. And the cholorite contains high Fe and Alâ…£and low Mg. The chlorite of metasomatic type contains higher Fe and Alâ…£and lower Mg than the chlorite of filling vein type. The relationship between Fe²⁺+Alâ…£and Fe²⁺/(Fe²⁺+Mg²⁺) is positive correlation. The XRD test result manifests that the unit cell values of chlorite are both lower than standard. The infrared spectrum analysis on chlorite shows its atlas corresponds with chamosite.The forming temperatures of chlorite computed by the chosen three formulas vary greatly, and the variance value is 30℃～60℃. The homogenization temperatures of fluid inclusions in symbiotic quartz indicates the chlorite composition thermometer formula can by applied with and using formula which was derived by Cathelineau in 1985 can compute the forming temperature more accurately. The result of calculation reveals the chlorite in tin allotment formed in early stage (280℃～320℃), medium stage (210℃～260℃)and later stage (100℃～180℃) and the chlorite in copper deposit of Xinjiang formed in medium temperature condition.By this research, the limitation of application of the chlorite composition thermometer formula can be concluded. And the paper suggests the chlorite composition thermometer formula should be used with other mineral thermometer to compute the forming temperature more accurately.