摘要
作为金属Cu最主要来源的斑岩铜矿床主要产于岛弧及陆缘弧环境。基于大量弧环境斑岩铜矿床研究而建立的经典斑岩铜矿成矿模型,在后来环太平洋成矿带斑岩型矿床的勘查中取得了重大突破,成为科学理论指导矿床勘查的典范。然而,近年来国内矿床学家发现,除经典成矿模型所记录的岛弧及陆缘弧环境外,斑岩铜矿还可产于碰撞造山带内,甚至产在陆内环境中。显然,这些斑岩铜矿的成因无法用经典的斑岩铜矿成矿模型解释。文章从弧环境斑岩铜矿成矿模型的综述入手,通过对青藏高原斑岩铜矿床的成矿环境及构造控制、含矿斑岩起源、矿床基本特征、成矿物质来源、金属富集机制以及成矿流体来源及演化等已有研究成果的综合分析,初步提出了碰撞造山环境斑岩铜矿的成矿模型。该模型强调:①碰撞造山环境斑岩铜矿含矿斑岩为强烈挤压构造背景下形成的埃达克岩,岩浆起源于加厚的新生下地壳,板块断离或岩石圈拆沉诱发的软流圈物质上涌,以及斜向碰撞导致的挤压-伸展的构造机制转换通常是引发岩浆源区发生部分熔融的外部条件;②成矿金属的深部富集是因岩浆高氧逸度所致,高氧逸度条件下,S主要以硫酸盐的形式溶解于岩浆之中,从而导致通常优先向硫化物分配的Cu、Au等开始作为不相容元素向硅酸盐熔浆中富集;③含矿斑岩的侵位既可受到因斜向碰撞诱发的大型走滑断裂系统的控制,也可受到岩石圈拆沉诱发的大型张性断层的控制;而含矿斑岩的就位则受矿区尺度的构造控制,多组构造的交汇部位或大型背斜的核部常是斑岩铜矿产出的重要位置;④大型矿床,特别是超大型矿床下部通常存在岩浆房,岩浆房的流体出溶是引发矿床大规模蚀变与矿化的根源;成矿金属与S均来自岩浆,与含矿斑岩可能具有相同的源区;⑤矿床整体上具有与弧环境类似的�
Porphyry Cu deposits （PCDs）, as the primary source of copper, are usually thought to be formed in a magmatic arc setting. They can also occur in collisional orogen or intraplate settings. The classic PCDs model, proposed by Lowell and Guilbert （1970）, has been widely accepted by economic geologists because of its practical value in the exploration of PCDs in the arc setting, especially in the Circum-Pacific Belt. However, Lowell and Guilbert＇s model fails to give a reasonable explanation of the PCDs in the collisional orogen setting. The authors therefore give a detailed description of geological setting, tectonic control, magma source, general characteristics of the ore deposit, source and enrichment mechanism of metals, fluid source and evolutionary path of PCDs in the Qinghai-Tibetan collisional orogen setting, and propose a preliminary genetic model. Several points are emphasized in this model： ① Mineralization-related porphyry intrusions in the collisional orogen setting are geochemically adakitic rocks, which originaue from the newly-formed lower crust and are triggered by the upwelling of asthenosphere and/or the transition of structure mechanism from extrusion to extension. ② The enrichment of Cu and other metals in the adakitic magmas results from the relatively high oxidation state of the source, in which the bulk of the sulfur is dissolved in the sulfate form, with the result that sulfide-compatible elements such as Cu and Au can also behave as incompatible elements and will be retained in the evolving magmas.③ The ascent of the adakitic magmas is usually constrained by large-sized strike-slip fault systems triggered by oblique collision or by large-sized normal faults induced by lithosphere removal, whereas the emplacement of the adakitc magmas is generally controlled by mine-scale structures. ④ The magma chamber usually exists below large-sized and, especially, giant deposits. In these deposits, Cu, S and magmatic fluids, which are essential for the formation of porphyry Cu deposi
出处
《矿床地质》
CAS
CSCD
北大核心
2009年第5期515-538,共24页
Mineral Deposits
基金
国家基础研究规划973项目(2009CB421004-1)
国家自然科学重点基金(40730419)的联合资助
关键词
地质学
斑岩铜矿
成矿模型
碰撞造山带
青藏高原
geology
porphyry copper deposit
genetic model
collisional orogenic belt
Qinghai-Tibetan plateau
