Mineralogical Characteristics of Exsolved Spinel in the Panzhihua V-Ti Magnetite Deposit, Sichuan: Implications for the Mineralization Process

作     者：ZHANG Zhibin HUANG Fei XING Miaomiao WAN Quan GAO Wenyuan GAO Shang CHEN Zhenyu CAI Jianhui 

作者机构：College of Resources and Civil Engineering Northeastern University State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences School of Civil Engineering Shijiazhuang Tiedao University Key Laboratory of Metallogeny and Mineral Resource Assesment Ministry of Land and Resources Institute of Mineral Resources Chinese Academy of Geological Sciences 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2018年第92卷第5期

页      面：1784-1797页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：funded by the National Natural Science Foundation of China(Grant No.41172047) the Open Fund of the Key Laboratory of Ore Deposit Geochemistry(Institute of Geochemistry,Chinese Academy of Sciences,Guiyang),(Grant No.201308) the Open Fund of the Key Laboratory Metallogeny and Mineral Resource Assessment,Ministry of Land and Resources(Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing)(Grant No.ZS1407) 

主　　题：spinel exsolution mineralogical characteristics compositional zonation mineralization process Panzhihua Sichuan 

摘      要：Spinel exsolution is widespread in titanomagnetite from the Fe-Ti oxide gabbro of the Panzhihua intrusion, Emeishan Large Igneous Province, SW China. However, little research has been conducted into the implications of patterns in the mineralogical characteristics of the spinel for spatial variation in the controls on the exsolution mechanism and, hence, the formation process of the ore deposit. This study selected the Lanjiahuoshan Ore Block in the Panzhihua V-Ti magnetite deposit to explore this issue, systematically studying exsolution textures in the titanomagnetite through petrographic observation and the integrated use of in-situ microanalysis. The results show that the exsolved spinel gradually becomes finer-grained and less abundant from the center to edge and the bottom to top of the ore bodies. Compositionally, there is an inverse correlation between the size of exsolved spinel grains and their Mg# value. In addition, there is compositional zonation in the spinel interiors, with a gradual increase in the Mg content and decrease in Fe content from the core to the rim. The analysis suggests that fractional crystallization of ferrotitanium magma with a high oxygen fugacity in a shallow magma chamber caused compositional differences in the primary magnetite solid solution in different parts of the Panzhihua intrusion. Additionally, the thermal evolution of the magnetite solid solution differed in different parts of orebody, bringing about variations in spinel development. Together, these effects resulted in spatial variation in the abundance, grain size, and morphology of spinel in different parts of the orebody and intrusion that follows an identifiable distribution law. Furthermore, the compositional zonation of exsolved spinels reflects the rapid growth of exsolution features in a high-temperature environment. Thus, the size, morphology, abundance, and composition of spinel exsolution features in titanomagnetite provide a valuable petrogenetic tool for esti