Geochemical Characteristics of Granite in the Xiaopingba Deposit of Wenshan,Yunnan Province and Its Implications for Petrogenesis

Xiaopingba contact metasomatic scheelite skarn deposit is located in the eastern margin of Bozhushan granite,southeastern Yunnan province.The orebodies are mainly produced in the contacts between medium grained biotite monzogranite of the first intrusion and Cambrian carbonatite.Major trace and rare element analysis of the granite shows that its SiO₂ contents range from 67.69%-76.98%(average 70.96%),the average total alkaline contents,K₂O/Na₂ O,A/CNK and Rittmann index are 8.06%,2.04,1.03,and 2.36 respectively.The rockbody is characterized by highly-enriched kalium cale-alkaline and belongs to peraluminous granite.The trace elements are characterized by enrichment of large-ion lithophile elements such as Rb,Pb,Th,U,La and Zr depletion of high field strength element and incompatible elements such as Nb,Ta,Sr,Ba,Ti.It has high total rare earths(average 288.01×10^-6),medium strong negative Eu anomalies(^δEu=0.36-0.69,average 0.57) and the right-declining of rare earth elements distribution patterns.CaO/Na₂O vs Al₂O3/TiO₂ and Rb/Ba vs Rb/Sr all indicate the granite originated from the magma formed by argillite rocks.Its geochemical characteristics imply that the Xiaopingba granite is mainly derived in the crust,and experienced a crystal process.Hence,it belongs to the S-type granite and should be formed in a continental collision tectonic setting.