秦岭-大别钼矿带超大型斑岩钼矿成因研究

The nature of ore-forming fluids, the sources of ore metals, and the type and zoning of wallrock alteration are always the core of the studies of hydrothermal mineral deposits. They are also the keys to understand the hydrothermal mineralization, including the porphyry-type Mo systems. The Qinling-Dabie Mo belt, containing many Yanshanian giant Mo deposits and the biggest Mo reserve in the world, has experienced multistage Mo metallogenic events, and thus can be taken as the “Natural Laboratory” to insight into porphyry-type Mo mineralization. Taking the unique “out-porphyry mineralization” as a window, this project will focus on detail study in geology, wallrock alteration and geochemistry of six large to giant Mo deposits at Shapinggou, Tangjiaping, Qian’echong, Donggou, Yuchiling and Jinduicheng, with aims to develop a zoning model for wallrock alteration of porphyry Mo systems in continental collision orogens; to reveal the nature and source of ore fluids and their controlling on wallrock alteration, and to trace the sources of ore metals. Thus we improve the metallogeny of porphyry Mo deposits, and scientifically interpreat the unique out-porphyry mineralization. This project also improves the understandings of the Mo-mineralization in the Qinling-Dabie Mo belt, enhance the international impact of the Mo belt, innovate the ore-forming theory of Mo deposits, and provide better guide for future exploration.

成矿流体性质，成矿物质来源，围岩蚀变类型和分带，始终是热液矿床研究的核心内容和解决矿床成因问题的关键依据，也是斑岩钼矿床研究的三大科学问题。秦岭-大别钼矿带钼资源量全球第一，历经多期钼矿化，燕山期超大型斑岩钼矿聚集，是研究斑岩钼矿成矿问题的天然实验室。本项目拟发挥这一自然优势，以“斑岩体外成矿”这一奇异现象为突破口，选择6个大型-超大型矿床（沙坪沟、汤家坪、千鹅冲、东沟、鱼池岭、金堆城），详细解剖矿床地质、围岩蚀变以及地球化学特征，建立大陆碰撞造山带斑岩钼矿床围岩蚀变分带模式，揭示成矿流体性质、来源及其与围岩蚀变的关系，示踪成矿物质来源，科学解释“岩体外成矿”的现象，丰富和完善斑岩钼矿床成矿理论。研究结果可提升秦岭-大别造山带钼矿床成矿规律的认识水平，实现钼成矿理论研究的创新，提升秦岭-大别钼矿带研究的国际影响力，服务于找矿勘查。

秦岭-大别造山带是典型的大陆碰撞造山带，已探明钼金属储量超过1000万吨，是世界第一大钼矿省，彰显了大陆碰撞造山过程钼成矿的重要意义。本项目对秦岭-大别钼矿带代表性的大型、超大型钼矿床开展了深入研究，揭示了一系列成矿规律: (1) 钼矿床集中分布在地壳厚度较大的造山带内部，特别是A型俯冲或逆冲构造的上盘; (2) 矿床爆发式形成于燕山期，特别是160-110 Ma；(3)早前寒武纪岩石钼含量高，是成矿元素钼的主要来源，也是有利的赋矿围岩; (4) 赋矿围岩的物理化学性质制约了矿化类型、矿体定位、成矿元素组合、围岩蚀变特征及变化；(5) 岩浆热液矿床的成矿过程普遍具有4阶段特点，成矿流体从岩浆热液最终演化为大气降水热液；(6) 斑岩钼矿床比斑岩铜钼矿床，燕山期斑岩钼矿比前燕山期斑岩钼矿，具有更强的钾长石化、萤石化和碳酸盐化，更弱的绢英岩化、青磐岩化和高级泥化；(7)大陆碰撞体制的斑岩钼矿床形成于富碳质流体，发育含子晶和不含子晶的碳质包裹体和碳水溶液包裹体; (8) 各类包裹体中，富CO2流体包裹体的钼含量最高；（9）斑岩矿床辉钼矿Re含量是判别物质来源的重要标志，低于50ppm者壳源为主，大于50ppm者幔源为主。成果集中体现于2本专著，即《秦岭造山带钼矿床成矿规律》（科学出版社，2020，942页）和《Geology and Geochemistry of Molybdenum Deposits in the Qinling Orogen, P R China》(Springer, 2022, 842p).