摘要
党坝矿床是四川西部可尔因稀有金属矿田中的花岗伟晶岩型锂辉石矿床,达到了超大型规模。锡石是锂辉石伟晶岩中重要的矿物成分。但对锡石的显微结构特征研究较为滞后,微区成分及其对岩浆演化的指示意义尚不明确。本次研究以党坝矿床Ⅷ号和Ⅵ号锂辉石伟晶岩(矿体)中的锡石为研究对象,开展背散射图像(BSE)、阴极发光(CL)、综合矿物分析系统(TIMA)、原位微区成分(EPMA和LA-ICP-MS)分析。研究结果显示,党坝矿床锡石中Fe,Nb,Ta,Ti元素含量较高,Fe,Mn,Nb,Ta,Ti等元素与Sn^(4+)可发生替代;Fe与Nb,Ta呈明显的正相关性,与Sn呈负相关性;Hf和Zr之间不存在正相关关系,但Ti与Zr和Hf的阳离子成正比,表明锡石的元素替代方式主要包括2(Nb,Ta)^(5+)+Fe^(2+)→3Sn^(4+)和Ti^(4+)→Sn^(4+)。TIMA分析显示,锡石中含有钠长石和铌锰矿等矿物包裹体。锡石的BSE图像相对均一。CL图像显示锡石主要有黑色、灰黑色均一结构、振荡环带、核边结构(黑色核+灰白色边或补丁)以及核-边反环带(灰白色核+黑色边)四种结构。从锡石的黑色(灰黑色)晶体(核)→振荡环带→灰白色边(补丁)区域,党坝矿床Ⅵ号矿体锡石的Nb、Ta、Fe、Zr、Ga以及Hf的含量逐渐降低。Ⅵ号矿体锡石发育灰白色补丁结构或者灰白色边,以及较低的Ta(16.45×10^(-6)~93.84×10^(-6))含量,显示经历了热液活动或者有新的岩浆活动事件叠加;党坝矿床Ⅷ号矿体锡石Ti/Zr比值(0.32~3.12)低于Ⅵ号矿体锡石的Ti/Zr比值(1.65~10.80),指示Ⅷ号矿体相比Ⅵ号矿体距离成矿母岩距离较远。
The ultra-large-scale Dangba deposit is a granitic pegmatite-type spodumene deposit in the Ke’eryin rare metal mineral field of western Sichuan.The cassiterite mineral within it is an important mineral component of the spodumene pegmatite,but previous studies on the microstructural characteristics of this cassiterite have been relatively limited.This study uses methods of backscattered electron imaging(BSE),cathodoluminescence(CL),integrated mineral analysis system(TIMA),and in-situ micro-area composition analyses(EPMA and LA-ICP-MS)to investigate the cassiterite in spodumene pegmatites from theⅧandⅥorebodies of the Dangba deposit,aiming to reveal the micro-area composition of cassiterite and unravel its implications for magmatic evolution.The research results show that the cassiterite in the Dangba deposit has relatively high contents of elements such as Fe,Nb,Ta,and Ti,with elements like Fe,Mn,Nb,Ta,and Ti being able to substitute for Sn^(4+).There is a significant positive correlation between Fe and Nb,Ta,while a negative correlation is observed with Sn.No positive correlation exists between Hf and Zr,but Ti is positively correlated with the cations Zr and Hf,indicating that the elemental substitution in cassiterite primarily includes 2(Nb,Ta)^(5+)+Fe^(2+)→3Sn^(4+)and Ti^(4+)→Sn^(4+).TIMA analysis reveals the presence of mineral inclusions such as albite and columbite-Mn in the cassiterite and the BSE images of cassiterite appear relatively homogeneous.The CL images show that the cassiterite mainly exhibits four structures:homogeneous black and dark gray structures,oscillatory ring,core-rim structures(black core+gray-white rim or patch),and core-reversed rim(gray-white core+black rim).From the black(dark gray)crystal(core)→oscillatory ring→gray-white rim(patch)region,the content of Nb,Ta,Fe,Zr,Ga,and Hf in the cassiterite of theⅥorebody gradually decreases.The cassiterite in theⅥorebody develops gray-white patch structures or gray-white rims,as well as lower Ta contents(16.45×10^(-6)~93.84×10^(-6)),indicating that it has experienced hydrothermal activity or the overlay of new magmatic events.The Ti/Zr ratio of the cassiterite in theⅧorebody(0.32~3.12)is lower than that in theⅥorebody(1.65~10.80),indicating that theⅧorebody is relatively farther from the mineralizing parent rock compared to theⅥorebody.
作者
钟伟
谭华
费光春
陈金香
陆雪
蔡云华
朱汇派
杨贵兵
冯倍诗
林程扬
丰国瑞
宋梓煜
ZHONG Wei;TAN Hua;FEI Guangchun;CHEN Jinxiang;LU Xue;CAI Yunhua;ZHU Huipai;YANG Guibing;FENG Beishi;LIN Chengyang;FENG Guorui;SONG Ziyu(Sichuan Institute of Comprehensive Geological Survey,Chengdu,Sichuan 618000,China;College of Earth and Planetary Science,Chengdu University of Technology,Chengdu,Sichuan 610059,China)
出处
《矿物岩石》
北大核心
2025年第3期81-94,共14页
Mineralogy and Petrology
基金
国家自然科学基金项目(批准号:41702074)
四川省科技厅项目(编号:25JBGOV0001)
四川省政府性投资地质勘查项目(编号:DZ202415)
四川省地质调查研究院科研项目(编号:SCLGS-CZDXM-2024001)。
关键词
锡石
阴极发光
原位微区分析
锂辉石伟晶岩
四川
cassiterite
cathodoluminescence(CL)
in-situ microanalysis
spodumene pegmatite
Sichuan
