青藏高原新生代造山型金成矿系统  

Cenozoic orogenic gold system in Tibet

作　　者：王庆飞[1] 邓军[1] 翁伟俊 李华健[1] 王璇[1] 李龚健[1] WANG QingFei;DENG Jun;WENG WeiJun;LI HuaJian;WANG Xuan;LI GongJia(State Key laboralary of Gedlogical Preceses and Mineral Resources,China Uniteniy of Geusciences,Bejing 100083,Chins)

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083

出　　处：《岩石学报》2020年第5期1315-1353,I0001-I0006,共45页Acta Petrologica Sinica

基　　金：国家重点研发计划(2016YFC0600307);国家重点基础研究发展计划“973”项目(2015CB452606);基础科研费优秀教师基金项目(2652016070);科技部项目(BP0719021)联合资助.

摘　　要：形成在大洋俯冲过程的造山型金矿已被广泛研究,而对随后的大陆碰撞阶段形成的造山型金矿研究较少。青藏高原是最年轻的大陆碰撞事件的产物,为揭示大洋俯冲-大陆碰撞完整构造演化背景下的造山型金成矿系统的成因提供了难得的研究窗口。研究表明,青藏高原存在三个金成矿带:(1)在大洋俯冲和大陆碰撞初期(60~43Ma),在正向碰撞带的挤压构造中,沿雅鲁藏布江缝合带形成石英脉型金矿带;(2)在大陆侧向碰撞带的大规模走滑剪切环境中(32~21Ma),发育受剪切带控制的石英脉型和浸染型矿体为主的金矿带;(3)在中新世印度大陆岩石圈回撤背景下(19~15Ma),喜马拉雅穹窿带普遍发育与Sb矿化有关的浸染型和细脉型金矿带。矿床矿化-蚀变和成矿流体特征综合表明三个矿带成矿深度具有逐次变浅的系统变化规律。碰撞造山环境造山型金成矿作用发生在峰期变质和退变质之后,脉动式的成矿作用多数和印度-欧亚板块汇聚速率的多期下降具有同步性,和大洋板片断离和大陆板片回撤等地幔扰动事件同期。岩石圈结构控制了流体的运移和成矿位置,深部成矿流体在较厚岩石圈的压力下沿板块边界上涌至岩石圈厚度梯度处就位。石英脉型金矿金属沉淀受到地震泵模式和流体不混溶作用控制,浅成蚀变岩型主要受到水岩反应的控制。三个金矿带黄铁矿δ34S中值大多是0左右,与不同时期的围岩地层无关;成矿流体δ18O整体上与富集地幔产生流体的氧同位素一致;与成矿有关的黄铁矿的40Ar/36Ar和3He/4He值表现出明显的地幔来源特征;矿石硫化物PGE特征显示成矿流体具有和岩浆热液不同的地化属性。矿床地球化学特征、金矿化整体滞后于区域进变质并与地幔扰动事件具有同步性均表明青藏高原金矿成矿流体和金属主体来自于地幔。文章进一步为造山型金矿石氢氧同位素的时空变The orogenic gold deposits formed in the oceanic subduction processes have attracted much attention,yet those generated in the following continental collision stages have been less researched. Tibet Plateau is the youngest continental collision product which has provide a rare opportunity to study the genesis of orogenic gold systems formed in the complete course from the oceanic subduction to continental collision. Three orogenic gold belts were delineated in Tibet Plateau:( 1) the mesozonal quartz vein type deposits formed in 60 ~ 43 Ma along the Yalung Tsangpo suture zone under a compressional regime;( 2) the mesozonal gold deposits,consisting of both quartz vein and disseminated ores,developed along shear zones in the oblique continental collision zone from the initiation to termination of crustal shearing during 32 ~ 21 Ma;and( 3) the widely distributed mesozonal to epizonal disseminated and veinlet gold deposits produced in Himalayan doming belt within 19 ~ 15 Ma in the background of Miocene rollback of Indian continental lithosphere,and these deposits are commonly related to antimony mineralization. The features of mineralization and alteration,together with oreforming fluids physiochemical parameters,consistently indicate systematic and gradual shallowing of metallogenic depth of these three gold belts. The Cenozoic orogenic gold deposits in Tibet were formed during peak to retrograde metamorphism of regional crustal rocks.The mutiperiodic mineralization was mostly synchronized with multi-stage drops of convergence rate between India and Eurasia plates,and significantly controlled by oceanic slab breakoff and continental slab rollback. Ore fluids migration and spatial location of orogenic gold deposits were much determined by lithospheric structure. Ore fluids migrating upwards were considered to be driven by higher pressure of thicker lithosphere into the thinner lithosphere with less pressure. Metal precipitation of mesozonal quartz vein type gold deposits was controlled by repetitive cracking-sealing p

关 键 词：造山型金矿 同位素 青藏高原 穹窿 地幔流体 大陆碰撞 

分 类 号：P618.51[天文地球—矿床学]