新疆和田大红柳滩矿田稀有金属矿床的成矿机制  

The metallogenic mechanism of rare metal deposits in the Dahongliutan ore field,Hotian,Xinjiang

作　　者：高景刚[1,2] 梁婷 王登红[3] 凤永刚 李永[4] 谭细绢 岑炬标 何蕾 GAO JingGang;LIANG Ting;WANG DengHong;FENG YongGang;LI Yong;TAN XiJuan;CEN JuBiao;HE Lei(School of Earth Science and Resources,Chang an University,Xi'an 710054,China;Xi'an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Xi'an 710054,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Xinjiang Non-ferrous Geological Exploration Bureau,Urumqi 830000,China)

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]西安市关键金属成矿与高效利用重点实验室,西安710054 [3]中国地质科学院矿产资源研究所,北京100037 [4]新疆有色地质勘查局,乌鲁木齐830000

出　　处：《岩石学报》2024年第9期2753-2768,共16页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2021YFC2901902);中国地质调查局项目(DD20221695)联合资助.

摘　　要：大红柳滩稀有金属矿田位于西昆仑中段,是松潘-甘孜-西昆仑花岗伟晶岩型稀有金属成矿带的重要组成部分,已发现白龙山、509道班西、大红柳滩东、507锂矿等大中型花岗伟晶岩型锂矿床7处,探获Li_(2)O储量达到1Mt以上,成矿潜力巨大。本文梳理了前人对大红柳滩稀有金属矿田的成矿特征及成矿作用研究,得出以下认识:(1)花岗伟晶岩与大红柳滩复式岩体形成于晚三叠世,两者空间关系密切,自岩体向远端可分成微斜长石型(矿物组合为微斜长石、石英和白云母)、锂辉石型(矿物组合为锂辉石、钠长石、石英和白云母)的分带规律,锂辉石伟晶岩多数分布在岩体外接触带1~2km范围内;(2)石英闪长岩、黑云母二长花岗岩和二云母二长花岗岩具有不同的地球化学特征以及ε_(Hf)(t)、ε_(Nd)(t)和δ^(7)Li值,是晚三叠世同碰撞构造背景下不同源区熔融的产物;(3)花岗伟晶岩与二云母二长花岗岩形成时代基本一致,具有相似的Hf、Li同位素特征,反映其源于相同的源区,形成于富白云母矿物的变沉积岩通过白云母脱水熔融;(4)初始熔体富助熔元素P、B、F和碱金属,能够增加H_(2)O在熔体中的溶解度,有利于Na、Li碱金属元素的富集,形成初始富锂熔体;(5)二云母二长花岗岩和花岗伟晶岩的空间关系、地球化学和Li同位素特征与岩浆分离结晶模型不同,与花岗岩浆的不混溶作用有关。综上所述,富挥发分、碱金属元素的初始富锂熔体上升过程中的熔体-流体分离作用可能是稀有金属元素超常富集的主要机制。大红柳滩复式岩体的外围,特别是二云母二长花岗岩的外接触带1~2km范围是寻找锂辉石伟晶岩的有利地区。The Dahongliutan rare metal ore field,situated in the West Kunlun orogenic belt,is a significant component of the pegmatite belt of Songpan-Ganzi-West Kunlun.Seven large and medium-sized lithium-beryllium deposits,including the Bailongshan,509 Daobanxi,Dahongliutan East and 507 lithium deposits,have been discovered in this area,with a total Li_(2)O reserve of over 1 million tons and even a greater mineralization potential.This article provides a comprehensive summary of the mineralization characteristics and processes within the Dahongliutan pegmatite field.Our findings reveal that:(1)The granitic pegmatite and the Dahongliutan pluton were formed in the Late Triassic,with a close spatial relationship.Additionally,there is a zoning pattern observed,with microcline pegmatites(mineral composition of microcline,quartz and muscovite)transitioning to spodumene pegmatites(mineral composition of spodumene,albite,quartz and muscovite)from the Dahongliutan pluton to its distal end.Most of the spodumene pegmatites are concentrated within 1~2km of the outer contact zone of the Dahongliutan pluton.(2)Differences of geochemical compositions,andε_(Hf)(t),ε_(Nd)(t)andδ^(7)Li values among quartz diorite,biotite adamellite and two-mica adamellite indicate they have distinct sources,albeit they have the same syn-collision tectonic background during the Late Triassic.(3)The consistency in ages and Hf and Li isotopic characteristics between pegmatite and two-mica adamellite suggests a shared origin from a muscovite-rich metasediment source through muscovite dehydration melting.(4)The initial pegmatite-forming melts are rich in fluxing elements,such as P,B,F and alkali metal elements,which enhance the solubility of H_(2)O in the melt,facilitating the enrichment of Na,Li and alkali metal elements,thus forming a lithium-rich pegmatite-forming melt.(5)Space relations,geochemistry and Li isotope characteristics indicate that fractional crystallization may not occur between granite and granite pegmatite,but they may form due to the immi

关 键 词：稀有金属 伟晶岩 花岗岩 成矿机制 大红柳滩 

分 类 号：P588.12[天文地球—岩石学] P611.12[天文地球—地质学] P618.71