摘要
高品位超大型斑岩铜矿床因其巨大的经济价值和战略意义, 一直是矿产勘查学界的重点目标。西藏铁格隆南矿床作为我国首例高硫化型浅成低温热液矿化叠加斑岩铜矿化的超大型铜矿床, 具有埋藏浅、铜品位高、资源储量大的显著优势, 为我国高品位斑岩铜矿富集机制研究提供了难得的对象。该矿床的形成与早白垩世120~116Ma多期次花岗闪长斑岩侵入密切相关。矿床深部的高品位黄铜矿±斑铜矿矿体(0.8% Cu)主要分布在绢云母化蚀变带中, 其形成时代约为120Ma;浅部则叠加了以斑铜矿-蓝辉铜矿-硫砷铜矿-砷黝铜矿为主的高品位浅成低温热液矿化, 与明矾石-高岭石为主的高级泥化蚀变带相关, 形成时代约为116Ma和112Ma。铁格隆南矿床经历了约8Myr的岩浆-热液活动, 期间伴随的剥蚀作用和地下水潜水面下降是浅成低温热液铜矿化叠加于深部斑岩型铜矿化、并促进铜富集的关键因素。矿床形成后, 形成于110Ma的美日切错组火山岩的快速喷发覆盖, 有效保存了形成较浅的高品位铜矿体。铁格隆南矿床与全球多个世界级超大型高品位斑岩铜矿(如Resolution、Hugo Dummett North、Chuquicamata、Rosario、Butte、Onto和Čukaru Peki等)具有相似的地质特征, 其成矿过程的岩浆-热液活动持续时间长(2~5Myr), 高级泥化蚀变叠加于早期的绢云母化和钾化蚀变之上, 形成规模巨大的高品位矿体, 主要分布于绢云母化和高级泥化蚀变带。长时间持续的岩浆-热液活动为超大型高品位斑岩铜矿的形成提供了巨量的金属元素来源。在高级泥化蚀变过程中, 强酸性、高氧逸度的流体活化早期的铜硫化物, 并在高级泥化蚀变带中发生铜的富集, 形成高硫化态的斑铜矿、蓝辉铜矿及铜蓝等矿物。浅成低温热液蚀变的叠加加速了含矿热液的冷却, 促使铜的快速沉淀而富集。由于此类矿床通常形成较浅, 易受剥蚀作用影响, 因此成矿后的沉积岩或火山岩覆盖是其得以保存的关键。在高品位超大型斑岩铜矿床的勘查中, 应重点关注具有长期岩浆-热液活动的斑岩成矿区带内存在后期火山岩或沉积岩覆盖的区域。同时, 与高级泥化和绢云母化蚀变相关的地质、地球化学、遥感及地球物理特征是重要的勘查标志。
Giant high-grade porphyry copper deposits are of significant economic value and strategic importance, which can rapidly improve the copper resource landscape of a region and bring it some critical exploration targets. The Tiegelongnan deposit in Tibet is an iconic copper deposit in China characterized by high-sulfidation epithermal Cu-Au mineralization superimposed on porphyry copper mineralization. This deposit, characterized by shallow burial, high copper grade and large resource reserves, represents an excellent case for studying high-grade porphyry copper deposits in China. The formation of the Tiegelongnan deposit is associated with multiple intrusions of granodiorite porphyries aged between 120Ma and 116Ma in the Early Cretaceous. High-grade chalcopyrite±bornite porphyry-type ore bodies (0.8% Cu) are mainly distributed in zones of sericitic alteration, dated to around 120Ma. Near-surface high-grade epithermal Cu mineralization, characterized by bornite-covellite-enargite-tennantite-pyrite mineral assemblages, is related to advanced argillic alteration dominated by alunite and kaolinite with formation ages of approximately 116Ma to 112Ma. The Tiegelongnan deposit experienced around 8 million years of magmatic-hydrothermal activity, accompanied by erosion and groundwater infiltration, which resulted in the superposition of epithermal copper mineralization on deeper porphyry copper mineralization, promoting copper enrichment. Rapid volcanic cover preserved the near-surface, large-scale, high-grade copper ore bodies. This deposit shares characteristics with several world-class giant high-grade porphyry copper deposits (e.g., Resolution, Hugo Dummett North, Chuquicamata, Rosario, Butte, Onto, and Čukaru Peki). These features include prolonged magmatic-hydrothermal activity and late-stage advanced argillic alteration superimposed on early-stage sericitic and potassic alteration, forming abundant high-grade ore bodies in sericitic and advanced argillic alteration zones. Prolonged magmatic-hydrothermal activity provided massive amounts of metallic elements, forming the material basis for giant high-grade porphyry copper deposits. Strongly acidic, high-oxygen fugacity fluids during advanced argillic alteration likely remobilized early copper sulfides and facilitated primary copper enrichment in advanced argillic zones, forming high-sulfidation state sulfides such as bornite, covellite and chalcocite. Additionally, the overlap of low-temperature alteration accelerated the cooling of ore-bearing hydrothermal fluids, concentrating copper within relatively confined spaces. Since these deposits are typically associated with advanced argillic alteration in the shallow parts of porphyry systems and are prone to erosion, post-mineralization cover is crucial for their preservation. Exploration for such porphyry deposits should prioritize areas with long-term magmatic-hydrothermal activity in porphyry metallogenic belts that are covered by volcanic or sedimentary rocks. Key indicators include geological, geochemical, remote sensing and geophysical anomalies associated with advanced argillic and sericitic alteration.
作者
杨超
李社
李宏伟
李建力
刘长城
王勤
翟建军
张琪
YANG Chao;LI She;LI HongWei;LI JianLi;LIU ChangCheng;WANG Qin;ZHAI JianJun;ZHANG Qi(College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu 610059,China;Tibet Jinlong Mining Co.,Ltd.,Lhasa 850000,China;No.5 Geological Brigade of the Tibet Bureau of Geology and Mineral Exploration and Development,Golmud 816000,China;China University of Geosciences(Beijing),Beijing 100083,China)
出处
《岩石学报》
北大核心
2025年第5期1509-1530,共22页
Acta Petrologica Sinica
基金
国家自然科学基金项目(42230813)
国家重点研发计划项目(2022YFC2905002)
珠峰科学研究计划项目(2024ZF11426)
新一轮找矿突破战略行动项目(DD20230054)
四川省自然科学基金项目(2024NSFSC0818)联合资助。
作者简介
第一作者:杨超,男,1989年生,博士,研究员,矿床学专业,E-mail:yangchao_21@126.com。
