岩石矿物学杂志2025，Vol.44Issue(5)：1117-1136,20.DOI:10.20086/j.cnki.yskw.2025.4169
川西李家沟花岗伟晶岩型锂矿床熔-流体演化及成矿时代
Melt-fluid evolution and mineralization age of the granite pegmatite-type lithium deposit in Lijiagou,western Sichuan:Constraints from microregional compositions of muscovite and cassiterite and U-Pb isotopes of cassiterite
摘要
Abstract
The Lijiagou granite pegmatite-type lithium deposit is a super-large ore deposit in western Sichuan.Cur-rently,the enrichment mechanism of lithium in the pegmatite of the Lijiagou deposit remains unclear.This paper focuses on multi-stage and multi-type muscovite and cassiterite in the pegmatite of the Lijiagou deposit,conducting microstructural observations,electron probe microanalysis(EPMA),LA-ICP-MS analysis,and cassiterite U-Pb dating.The study categorizes muscovite in pegmatites into three types:① primary muscovite(Ms),a product of the magmatic stage,with a relatively low-Li content ranging from 2 089×10-6 to 4 561 ×10-6;② transitional musco-vite(TM),formed during the magmatic-hydrothermal transition stage where melt and fluid coexist,resulting from the exsolution of volatile-rich fluid leading to the enrichment of Li element,with a Li content ranging from 8 173× 10-6 to 25 307 ×10-6;③ hydrothermal muscovite(HM),formed by fluid metasomatism,where the Li element gradually decreases during this stage(with a minimum of 642.7×10-6).The microregional compositional character-istics indicate that the K/Rb and Nb/Ta values gradually decrease from Ms to TM,indicating a higher degree of evolution of the Lijiagou deposit.Meanwhile,cassiterite in the pegmatite is classified into four types,from early to late,namely,relatively uniform structure(Cst-1)→ inhomogeneous core-edge structure(Cst-2,Cst-3)→ white patchy structure(Cst-4),with gradually increasing contents of elements such as Fe,Nb,and Ti.Combine with the Ta/(Nb+Ta)value,it is inferred that cassiterite exhibits characteristics of early Fe enrichment and late Nb enrich-ment during magmatic evolution.The significant increase of Ti content in white patchy cassiterite(Cst-4)reflects the metasomatic action of hydrothermal fluids.Furthermore,U-Pb dating of cassiterite within pegmatite containing spodumene reveals the depositional age of the Lijiagou deposit to be 196.18±4.39 Ma(n=18,MSWD=0.62).Based on existing research,it is determined that there are two stages of mineralization in the Lijiagou deposit,with ages of 211～205 Ma and 199～186 Ma,respectively.This paper believes that the mineralization process of the Lijiagou pegmatite experienced a melting-fluid evolution stage.The fluid exsolution resulted in the enrichment of Li element,which entered the spodumene lattice and precipitated into ore after reaching supersaturation,ultimately forming the Lijiagou pegmatite-type lithium deposit.关键词
李家沟/花岗伟晶岩型矿床/白云母/锡石/LA-ICP-MS微区分析Key words
Lijiagou/granite pegmatite-type deposit/muscovite/cassiterite/LA-ICP-MS microanalysis分类
天文与地球科学引用本文复制引用
韩警锐,赵媛,杨德剑,赵恒兵,陈浩,冉凤琴,多吉,彭勃,陈燃,唐波,奉大博,顾春进,杨阳..川西李家沟花岗伟晶岩型锂矿床熔-流体演化及成矿时代[J].岩石矿物学杂志,2025,44(5):1117-1136,20.基金项目
国家重点研发计划(2022YFC2905001) （2022YFC2905001）
国家自然科学基金项目(42230813,42402078) （42230813,42402078）
四川省自然科学基金项目(2023NSFSC0791) National Key Research and Development Program of China(2022YFC2905001) （2023NSFSC0791）
National Natural Science Foundation of China(42230813,42402078) （42230813,42402078）
Natural Science Foundation of Sichuan Province(2023NSFSC0791) （2023NSFSC0791）
