摘要
在地球演化早期的强还原条件下,钨表现为中等亲铁元素,因此地球中>90%的钨进入地核。在地幔和地壳的演化过程中,钨是极度不相容亲石元素,从而导致钨元素在地壳中的丰度约是地幔丰度的250倍。钨在岩浆熔体中主要以钨酸的形式迁移,在成矿热液中主要以氟、硼化合物或其络合物的形式运移。钨的矿化需要其在部分熔融、岩浆演化和晚期热液等各阶段逐渐富集。中国是世界上钨矿产资源最丰富的国家,约占世界总储量的60%以上,其中绝大多数矿床产在华南地区,与华南大规模的中生代岩浆活动具有密切的时空联系。微量元素特征(高Rb/Sr和K/Rb比值,低Nb/Ta和Zr/Hf比值)显示它们往往经历了强烈的岩浆分异,这可能与这些花岗岩通常具有高挥发分含量(如F)有关。岩浆中高的F含量对钨的富集和矿化十分重要,它可以降低熔体固相线、粘度和密度,有利于提高岩浆的结晶分异程度,因而使得高度不相容的钨元素在岩浆演化过程和后期热液阶段的富集与矿化。富挥发分岩浆的形成可能与俯冲板块后撤,软流圈物质上涌导致的多硅白云母等富F矿物的高温分解有关。研究表明,华南南岭地区侏罗纪的钨矿化花岗岩主要形成于太平洋板块的俯冲后撤,而华南南部晚白垩世钨成矿作用与新特提斯洋的俯冲后撤有关。
Tungsten(W)is a moderately siderophile element under reducing condition in the early history of the Earth,and thus has been mostly sequestered into the Earth\s core.During partial melting and magma evolution of the silicate Earth,tungsten is a highly incompatible lithophile element and thus can be dramatically enriched through these processes.The abundance of tungsten in the crust is about 250 times greater than that in the mantle.Tungsten migrates mainly in the form of tungstic acid in magmatic melts and in fluorine,boron compounds or their complexes in ore-forming hydrothermal fluids.The mineralization of tungsten in granitic magma requires the enrichment of tungsten in various stages,such as partial melting,magmatic evolution and late hydrothermal solution.The magmatic tungsten deposit is an important type of tungsten deposits.It can be further divided into different subtypes based on the characteristics of tungsten deposits,including quartz vein type,greisen type,porphyry type,skarn type,etc.China hosts more than 60%W reserves in the world,which were mainly formed in South China during the Mesozoic and were closely related to highly evolved granites.These granites generally have high F contents and have experienced significant differentiation as indicated by their high Rb/Sr and K/Rb ratios,and low Nb/Ta and Zr/Hf ratios.High F content is critical for W mineralization,because it decreases the viscosity and solidus of the magma,which consequently promote magmatic evolution and enrichment of W in the residual magmas.The high F characteristics in granites have been attributed to the Pacific and/or Neo-Tethys plate slab rollback,which leads to decomposition of phengite±apatite in the subducting slab due to abruptly elevated temperatures caused by asthenosphere upwelling during slab rollback,and releasing F and Li.
作者
祝红丽
张丽鹏
杜龙
隋清霖
ZHU HongLi;ZHANG LiPeng;DU Long;SUI QingLin(Center of Deep Sea Research Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,China;Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Minerals,Shandong University of Science and Technology,Qingdao 266590,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第1期13-22,共10页
Acta Petrologica Sinica
基金
国家自然科学基金项目(41803032)
国家重点研发计划“深地资源勘查开采”重点专项(2016YFC0600408)联合资助
关键词
钨矿
花岗岩
华南地区
岩浆演化
板块后撤
Tungsten deposit
Granite
South China
Magma evolution
Slab rollback
