大型斑岩铜矿成矿的深部构造岩浆活动背景

Deep tectono-magmatic setting for metallogenesis of large porphyry copper deposits

笔者以深部地球物理探测结果为基础,将地球物理与地质、地球化学资料结合起来分析了南美稳态的洋陆俯冲体制下安第斯斑岩铜矿带、藏南不稳态的陆陆碰撞体制下冈底斯斑岩铜矿带和不稳态的陆岛陆碰撞体制下三江地区的玉龙斑岩铜矿带渐新世以来深部成矿的构造岩浆活动背景条件,总结归纳出6条成矿的基本条件:(1)要有上地幔来源的高温岩浆热液的大量供给;(2)要有区域性铜的萃取来源;(3)要有上地壳的部分熔融层或岩浆房,以提供含铜热液的循环沉淀条件;(4)地壳上层构造体系中的张性断裂,以供岩浆热液的就位;(5)围岩的化学性质对矿质沉淀是重要的;(6)构造的相对稳态期,为矿质大量沉淀积累创造条件。在不稳态体制下要寻找相对稳态的时段。陆陆碰撞体制与洋陆俯冲体制下成矿作用的主要不同之处是构造的不稳态期长、陆壳加厚与构造复杂化,岩石层碎裂发育机制等。提出了冈底斯带的新的找矿远景地带。

Based on the results of deep geophysical exploration, combined with geological and geochemical data, this paper analyzes the Oligocene tectono-magmatic settings of deep-seated mineralization in the Andean porphyry copper belt in the South America stable ocean-continent subduction regime, the Gangdise porphyry copper belt in the southern Tibet unstable continent-continent collision regime and the Jamda porphyry copper belt in the Sanjiang area in the unstable continental island-continent collision regime. Six basic conditions for mineralization have been summarized：（1） there was a good supply of upper mantle-derived high-temperature magmatic hydrothermal fluids; （2） a regional source for copper extraction was available; （3） there were a partial melting layer of the upper crust or magma chamber for circulation and deposition of copper-bearing hydrothermal fluids; （4） there were tensile faults in the upper crustal tectonic system for emplacement of magmatic hydrothermal fluids; （5） the chemical properties of the country rocks were important for the precipitation of ore materials; and （6） the relatively stable tectonic stage created conditions for the precipitation of ore materials. In the case of an unstable regime, it is necessary to look for a relatively stable time interval in the regime. The main differences in mineralization between the continent-continent collision regime and ocean-continent subduction regime lie in the long tectonically unstable stage, continental crustal thickening and tectonic complication, as well as the mechanism of crack and break of the mantle lithosphere. The author proposes new ore prospect areas in the Gangdise belt .