CHEN Hui-jun1,2, ZHANG Shou-ting2, CAO Hua-wen2, WANG Xiang-fa1, NIE Xiao-liang1,ZHANG Wei2, TANG Li2
(1. Jiangxi Exploration and Development Center of Geology and Mineral Resources，Nanchang 330030, China;
2. School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China)
Abstract: The granite from the Guyong region, western Yunnan Province, China is closely associated with Sn deposits. Electron microprobe analyses show that the biotite in the Guyong biotite adamellite is “ferribiotite”, and the biotite from the Xiaolonghe Sn deposits biotite mimophyre adamellite is siderophyllite. Biotite from both plutons are iron-rich (FeOt=22.39%－27.91%) and magnesium-poor (MgO=1.08%－10.51%, Magnesium coefficient is 0.07－0.50). Biotite from Guyang granite is magnesium-rich, suggesting I-type granite contaminated by mantle material, while biotite from Xiaolonghe metallogenetic granite is aluminum-rich and magnesium-poor, suggesting typical peraluminous S-type granites of crustal origin. The crystallization temperature for biotite in Guyong granite and Xiaolonghe granite is 700－750 ℃ and 620－650 ℃ respectively, with the oxygen fugacity lgf(O2) of -14.0－-13.8 and -17.5－-17.2 respectively. Crystallization pressure for biotite from Guyong granite is 67－120 MPa, indicating a crystallization depth of 2.54－4.55 km. Relatively high temperature, low oxygen fugacity and shallow environments are favored for forming granite in this region. Xiaolonghe granite is more conducive to the formation of Sn deposits and has a higher potential for Sn mineralization than Guyong granite.
Keywords: biotite; granite; mineral chemistry; petrogenesis; mineralization; Guyong, Yunnan
E-mail: chenhuijun198910@163.com
ACTA MINERALOGICA SINICA Vol. 35, No. 2, 2015, Page 267-275
