摘要
文章对柴北缘沙柳泉1号绿柱石型伟晶岩脉按结构分带开展系统矿物学和流体包裹体研究,探讨沙柳泉伟晶岩岩浆分异和成矿流体演化特征。微斜长石和云母的成分变化趋势表明,沙柳泉1号伟晶岩从边缘向核部的岩浆演化主要受分离结晶的控制,分异程度逐渐升高。熔体的演化伴随着流体盐度的降低,流体于绿柱石结晶阶段变为富CO_(2)弱酸性流体。成矿流体从早期的中高温(200~427℃)、低盐度(w(NaCleq)为3.2%~9.9%)的NaClH_(2)O体系向后期的NaCl-H_(2)O和NaCl-H_(2)O-(CO_(2))组成的2种不同性质的流体演化。大量CO_(2)流体包裹体及流体包裹体内含较多菱铁矿(FeCO_(3)),指示富CO_(2)(CO_(3)^(2-))流体可能促进了绿柱石结晶。1号脉伟晶岩铍矿化是伟晶岩熔(流)体分异演化的结果。
In this contribution,systematic mineralogical and fluid inclusion study were performed on the Shaliuquan No.1 beryl-type pegmatite dike at northern margin of Qaidam Basin based on its internal zonation to explore the magmatic differentiation and evolution of ore-forming fluid within the pegmatite.The evolutionary trends of microcline and mica compositions suggest that the evolution of magmatic differentiation of the No.1 pegmatite from margin to core is mainly controlled by fractional crystallization,and the degree of differentiation increases gradually.The differentiation of the pegmatite-forming melt is accompanied by the decrease in the fluid salinity.The ore-forming fluids evolved to CO_(2)-bearing,weakly acidic fluids during the beryl crystallization.The ore-forming fluid hosed by quartz belongs to the NaCl-H_(2)O system with medium-high temperature(200~427℃)and low salin ity(w(NaCleq)3.2%~9.9%),whereas that hosted by beryl belongs to the NaCl-H_(2)O-(CO_(2))system with mediumhigh temperature(213~363℃)and low salinity(w(NaCleq)1.1%~10.2%).The early-stage NaCl-H_(2)O fluid evolved to two distinctly different fluids,namely a NaCl-H_(2)O fluid and a NaCl-H_(2)O-CO_(2) fluid at the late stage.The presence of abundant CO_(2)-rich fluid inclusions and daughter minerals including siderite(FeCO_(3))indicates that the crystallization of beryl was facilitated by fluids enriched in CO_(2)(CO_(3)^(2-)).The Be mineralization hosted by the Shaliuquan No.1 pegmatite is likely the consequence of both melt differentiation and fluid evolution.
作者
李兴辉
凤永刚
梁婷
李善平
李积清
余福承
高景刚
刘艳荣
郑炜
LI XingHui;FENG YongGang;LIANG Ting;LI ShanPing;LI JiQing;YU FuCheng;GAO JingGang;LIU YanRong;ZHENG Wei(School of Earth Science and Resources,Chang’an University,Xi’an 710054,Shannxi,China;Xi’an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Chang’an University,Xi’an 710054,Shannxi,China;Qinghai Institute of Geological Survey,Xining 810012,Qinghai,China)
出处
《矿床地质》
CAS
CSCD
北大核心
2024年第6期1404-1427,共24页
Mineral Deposits
基金
国家重点研发计划“战略性矿产资源开发利用”专项“我国西部伟晶岩型锂等稀有金属成矿规律与勘查技术”项目(编号:2021YFC2901902)
中国地质调查局“中国矿产地质志”项目(编号:DD20221695)共同资助。
关键词
矿物学
伟晶岩
流体特征
流体包裹体
沙柳泉矿床
mineralogy
pegmatite
fluid characteristic
fluid inclusion
Shaliuquan deposit
