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    斑岩型钨矿床研究进展

    Advances in the study of porphyry tungsten deposits

    • 摘要: 斑岩型钨矿床是全球第三重要的钨矿类型,但对其研究较为薄弱、零散。文章基于团队近年来对斑岩钨矿床的研究并系统搜集了全球的相关资料,然后对其进行梳理与总结。研究表明,斑岩型钨矿主要分布于环太平洋成矿带与阿尔卑斯—喜马拉雅成矿带,岩浆弧、板内及陆-陆碰撞等多种环境均有矿床产出。矿床绝大多数形成于中生代、少量形成于古生代。斑岩型钨矿化与弱氧化、较高分异程度的I型或A型花岗质浅成侵入体密切相关。成矿有关岩浆岩主要起源于古老地壳的重熔,并有少量亏损地幔和/或海洋沉积物的混染。成矿流体、金属元素等主要来自于相关的岩浆岩,成矿所需的钙、铁、锰可由地层与岩浆岩通过水岩反应共同提供。岩浆弧及板内环境下初始成矿流体多属于中高温、中高盐度的NaCl-H2O系统,大陆碰撞体系下则多属于中高温、中低盐度的NaCl-H2O-CO2体系。钨在熔-流体分异过程中倾向于富集在共存的流体相,然后以单体钨酸盐、多钨酸盐及氟钨酸盐类等形式迁移。矿质沉淀机制主要包括流体不混溶/沸腾/CO2逃逸±流体混合和水岩反应。白钨矿和黑钨矿作为斑岩钨矿床中最重要的两种钨矿物,其产出可能主要受控于相关岩浆-流体系统中F含量的高低。

       

      Abstract: P Porphyry tungsten deposit is the third most important type in the world, but its research is weak and scattered. This paper systematically summarizes and analyzes the research results in recent years from our team and other scholars about porphyry tungsten deposits. The results show that porphyry tungsten deposits are widely distributed in the Circum-Pacific metallogenic belt and the Alps-Himalayan metallogenic belt, and occur in magmatic arc, intraplate, and continental collision settings. Most of them were formed in Mesozoic and a few in Paleozoic. Porphyry tungsten mineralization is closely related to weakly oxidized, highly fractionated I-type or A-type hypabyssal granitic rocks, which were mainly derived from re-melting of the ancient crust, contaminated with a small amount of juvenile crust and/or depleted mantle and/or marine sediments. The ore-forming metals and fluids were dominantly originated from related magmatic rocks, and the Ca2+, Fe2+, and Mn2+ needed for W mineralization could be provided by the strata and magmatic rocks through water-rock reaction. The initial ore-forming fluids of porphyry tungsten deposits in magma arc and intraplate settings belong to the NaCl-H2O system with medium-high temperature, medium-high salinity and low CO2 content, while those under continental collision setting belong to NaCl-H2O-CO2 system with medium-high temperature, medium-low salinity and high CO2 content. W tends to be enriched in the coexisting fluid phase in the process of melt-fluid differentiation, and then migrates in the form of monomer tungstate, polytungstate, and fluorotungstate. The mechanisms of mineral precipitation mainly include fluid immiscibility/boiling/CO2 escape ±fluid mixing and water- rock reaction. Scheelite and wolframite are the dominant W-bearing minerals in porphyry tungsten deposits, and their occurrence may be mainly controlled by the fluorine content in relevant magma-fluid system.

       

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