西藏冈底斯中新世斑岩铜矿带:埃达克质斑岩成因与构造控制  

Genesis of adakitic porphyry and tectonic controls on the Gangdese Miocene porphyry copper belt in the Tibetan orogen.

作　　者：侯增谦[1] 高永丰[2] 孟祥金[1] 曲晓明[1] 黄卫 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]石家庄经济学院,河北石家庄050031 [3]西藏地勘局第六地质大队,西藏拉萨851400

出　　处：《岩石学报》2004年第2期239-248,共10页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目"印度-亚洲大陆主碰撞成矿作用"(项目编号:2002CB412600)资助。

摘　　要：作为贱金属主要来源的斑岩铜矿床,大多数产出于大陆边缘和岛弧环境。普遍认为。被俯冲洋壳板片释放流体交代的地幔楔部分熔融形成的玄武质岩浆,在相对封闭系统结晶分异和/或同化混染形成含铜长英质岩浆。然而.我们的研究表明,在西藏碰撞造山带,发育一条具有巨大成矿潜力的中新世斑岩铜矿带,含铜斑岩具有埃达克岩地球化学特性,来源于被加厚的藏南镁铁质下地壳,但俯冲的新特提斯洋壳板片部分熔融也不能完全被排除。斑岩铜矿形成于陆-陆后碰撞伸展时期(13～18 Ma),即青藏高原迅速抬升之后。横切碰撞造山带的南北向正断层系统,类似于岛弧环境下的横切弧的断层系统,成为埃达克质斑岩岩浆快速上升和就位的通道与场所,并使岩浆热液系统中大量的含矿流体充分地分离而成矿。Most porphyry Cu deposits, a main source of base metals, occur in continent and island-arcs. Cu-bearing felsic magmas were widely regarded to be derived from the basaltic paternal magma that was formed by melting of the mantle wedge, metasomatized by hydrous fluid released from the subducted oceanic slab and then evolved by crystal fractionation with or without assimilation. However, the data we present here indicate that a Miocene porphyry Cu belt with large mineral potential occurs in the Tibetan collisional orogen, and Cu-bearing porphyries show the geochemical characteristics of adakites, which were mainly derived directly from the thickened mafic lower-crust or the subducted New-Tethyan oceanic slab. The porphyry Cu systems developed during post-collisional extension after rapid uplift of the Tibetan plateau before 13 similar to 18 Ma ago. Like arc-transverse faults in arc settings, SN-trending normal faulting systems across the Tibetan orogen resulted in rapid rising and localization of adakitic porphyry magmas and sufficiently separating of large-volume Cu-bearing fluids from the magmatie-hydrothermal systems.

关 键 词：构造控制 埃达克岩 斑岩铜矿 碰撞造山带 西藏 

分 类 号：P588.13[天文地球—岩石学]