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Geochemical Characteristics and Classification of Granites Related to Tin Deposits in the Tengchong Area, Southwest China
详细信息   
摘要


     The Early Cretaceous K1 Donghe granitoid belt 143.0-111.7Ma, Late Cretaceous K1 Guyong granitoid belt 84.3-65.9Ma and Paleogene E1-2 Binlangjiang granitoid belt 66.4-41.2Ma extend from east to west in the Tengchong area. Based on petrography and element geochemistry of the Lailishan granite from Binlangjiang granitoid belt and Xiaolonghe as well as Shuicheng granites from Guyong granitoid belt which are closely related to tin deposits, this study shows that., these granites are riched in SiO2 and belong to potassic calc-alkalic to alkali-calcic series which total alkali ALK are 8. 17~ 8.15%, K20/Na2O1 and modified alkali-lime index MALI are 7.25-8.34; Lailishan granites A/ CNK is 1.02 - 1. 04 and appears weakly peraluminous whereas Xiaolonghe and Shuicheng granites A/ CNK are lower than 1. 0 and appear to be metaluminous; these granites were related to the collision between Tengchong and Baoshan blocks for Lailishan granite, FeO/FeO-k MgO = 0. 61 - 0. 67, relatively Mg enriched but low in ferromagnesian and referred to pelitic or semi-pelitic rocks sources as well as post-collision extension S-type granite~ while for Xiaolonghe and Shuicheng granites, FeO/FeO MgO =0.88-0.94, relatively Fe enriched and referred to anhydrous silicates continental crust sources as well as post-collision A2-subtype of A-type granites. This study defined genetic types, source characteristics and tectonic settings of Lailishan, Xiaolonghe and Shuicheng granites which are related to tin deposits, and pointed that different granitoid belts developed different granites.

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