摘要
云南个旧锡多金属矿床处于滇东南锡矿带的西端,是全球最大的锡多金属矿床之一。锡石作为个旧锡矿床中最主要的矿石矿物,其矿物化学特征对矿床成因具有重要的指示意义。本文运用扫描电镜、电子探针等手段对个旧锡多金属矿床中6种不同类型矿石中的锡石进行了详细的内部结构和矿物化学特征研究,并对其可能的成因进行了探讨。扫描电镜研究结果发现,除层间氧化矿型锡石较破碎外,其余类型锡石内部均发育有明显的环带结构。电子探针分析结果显示:各类型矿石中锡石的SnO_2质量分数变化范围为97.700%~101.728%;Ta_2O_5、FeO、ZrO_2、HfO_2平均质量分数较高,指示锡石形成于高温热液环境;(Fe+Mn)/(Nb+Ta)显示个旧锡矿区各类型矿石中的锡石具有热液锡石的特征,且各类型锡石中Nb_2O_5和MnO的质量分数极低,说明成矿热液可能来自于高度分异的花岗质岩浆,而Nb、Ta质量分数说明成矿作用发生于酸性-弱酸性环境中;In_2O_3质量分数显示了成矿温度及压力从块状硫化物型矿石、矽卡岩型矿石、电气石细脉带型矿石、含锡白云岩型矿石到层间氧化矿型矿石有逐渐降低的趋势;云英岩型矿石中锡石的In_2O_3质量分数较高还需进一步论证。锡石形成过程中岩浆热液物理化学条件的变化导致其内部环带结构的形成,电子探针数据显示锡石的环带结构中化学成分呈"锯齿状"变化,显示成矿作用发生于动荡的环境中,说明锡石沉淀具有多期多阶段的特征。
The Gejiu tin polymetallic deposit is located in the west of the southeastern Yunnan tin ore belt,and is one of the largest tin polymetallic deposits in the world.As the main ore minerals in the Gejiu tin-polymetallic deposit,the mineral chemical characteristics of cassiterite have a great implication to the ore genesis.In this research,we studied the internal structure and the mineral chemical characteristics of cassiterites out of six types of ores in the Gejiu tin-polymetallic using the scanning electron microscopy and electron probe microscope analyzer.The results of scanning electron microscopy show that except the interlayer oxidation broken ore type cassiterites,the zonal structure is clearly developed within cassiterites.The results of electron probe microscope analyzer（EPMA）show that the variation range of the mass fraction of SnO2 is 97.700%-101.728%,and the mass fractions of Ta2O5,FeO,ZrO2 and HfO2 are high,which indicates that these cassiterites may be precipitated in a high temperature environment.The value of（Fe＋ Mn）/（Nb＋ Ta）shows that the different types of cassiterites have the characteristics of hydrothermal cassiterites.Very low mass fractions of Nb2O5 and MnO in different types of cassiterites suggest that the ore-forming fluid may be derived from the highfractionated granitic magma.The mass fractions of Na,Ta indicate that the mineralization occurred in an acid to weak acid environment.The gradually decreased In2O3 in different ores（including sulfide,skarn,tourmaline veinlet belt,tin-bearing dolomite,and interlayer oxidation types of ores）indicates that the ore forming temperature and pressure have decreased gradually.However,the average mass fractions of In2O3 in greisen type need further study.The change of the physicochemical conditions of magma hydrothermal fluid during the formation of cassiterite resulted in the formation of its internal zonal structure.The electron probe data shows that the chemical composition in the zonal structure of cassiterite is ＂serrated＂,
作者
谈树成
郭翔宇
何小虎
谢志鹏
张亚辉
李惠民
郝爽
Tan Shucheng;Guo Xiangyu;He Xiaohu;Xie Zhipeng;Zhang Yahui;Li Huimin;Hao Shuang(School of Resource Environment and Earth Science, Yunnan University, Kunming 650500, China;Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, China;Tianjin Center of China Geological Survey, Tianjin 300170, China)
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2018年第3期736-753,共18页
Journal of Jilin University：Earth Science Edition
基金
国家自然科学基金项目(41262004
41702084)
云南省科技厅应用基础研究计划青年项目(2017FD063)~~
关键词
矿物化学
电子探针
锡石
个旧锡多金属矿床
mineral chemistry
electron probe microscope analyzer
cassiterite
Gejiu tinpolymetallic deposit
