Research On Geological Feature And Controlling Structure Of The Saxi Emerald Deposit

The Saxi emerald occurrence in southwestern Yunnan province is the first emerald occurrence discovered in China,Henceforth it has significant economic and geologic importance.The study of emerald occurrences in China started only recently,and the studies were mainly on gemmology and mineralogy.there were few studies on structural control and timing of mineralization,therefore it is necessary to study structural control of the occurrence and mineralization modelBe is an important constitution in emerald,and Cr and V are the color forming minerals.geochemical studies of the intrusive plutons and country rocks indicated that the Saxi group is an important source rock for Cr and V,and Cretaceous plutons provided Be and heat for the emerald mineralization.Argon dating of biotite from country rocks yielded plateau age of 112.44Ma±0.77 Ma.combined with mineralization related granites,we concluded that the emerald occurrence formed between 112.44±0.77Ma-75.9Ma.The emerald occurrence lies on the north to the boundary between south China and Indosinia blocks.Since Mesozoic it experienced multi-stage tectonic and magmatic evolution.The thrust belt formed between 220-159 Ma,consequently,Tuantian unit,Nanyangtian unit and Saxi unit were in fault contact with each other.The thrust belt cracked Saxi unit and resulted in numerous joints.The distribution of the emerald veins indicate that in 112Ma±0.77Ma-75.9Ma,the lithosphere' thinning and magmatism expanded previous joints,which provides good ore forming material and space for mineralization.