岩浆混合作用与新疆希勒库都克斑岩铜钼矿成矿关系研究

Magma mixing as one of the most important ways of rock-forming system, is important in understanding rock-forming process and magma evolution. Especially, magma mixing between the mantle-derived basic magma and the crustal acidic magma is a window to probe mantle-curst interaction. Magma mixing has a close connection with ore-forming processes, especially with the formation of porphyry-type deposits. Crust-mantle mixing played a major role in the formation of porphyry-type deposits, which occurred in both magmatic arc settings and continental settings. The Central Asian Orogenic Belt represented by northern Xinjiang is a very important continental metallogenic domain in the world, and shows the signs of magma mixing in many areas of Xinjiang, but the study on the relationship between magma mixing and metallogeny was rather poorly understood. The main objective of this project is to establish the genetic relationship between magma mixing and ore-forming processes. Taking Xilekuduke porphyry deposit formed in continental collision setting in northern Xinjiang and hybrid complex closely connected with ore-forming processes as research object, through combined use of petro-geochemistry, isotopic geochemistry, fliud inclusion, geochoronology, and the key studies of magma mixing characteristics, magma mixing processes, magma evolution of ore-bearing, ect, this study will discuss the genetic relationship between magma mixing and metallogeny and set up the model of magma mixing - porphyry deposit in the continental collision setting.

岩浆混合作用是成岩体系重要方式之一，是认识成岩过程、岩浆演化的重要途径。特别是深部岩浆在上升过程中与地壳偏酸性岩浆的混合作用，是研究壳-幔相互作用的重要窗口。壳幔相互作用与成矿，尤其是与斑岩型矿床的形成息息相关。无论是形成于岩浆弧环境还是大陆环境的斑岩型矿床，壳幔源岩浆混合对矿床的形成都至关重要。以新疆北部为代表的中亚增生型造山带是全球重要的大陆成矿域，其中岩浆混合现象发育，但关于岩浆混合与成矿关系研究甚少。本项目以建立岩浆混合作用和斑岩型矿床成因联系为目标，选取新疆北部大陆碰撞环境下形成的希勒库都克斑岩型铜钼矿床及与成矿密切相关的岩浆混合杂岩体为研究对象，通过岩石地球化学、同位素地球化学、流体包裹体、年代学等多手段联合应用，对研究区岩浆混合特征、岩浆混合过程、含矿岩浆演化等方面进行重点研究，探讨岩浆混合作用与斑岩矿床成矿的内在联系，建立大陆碰撞造山环境下岩浆混合-斑岩型矿床成矿模式。

壳幔岩浆混合作用是诱发成矿系统中各种地质作用的重要原因之一，与斑岩型矿床成矿关系密切。东准噶尔北缘希勒库都克铜钼矿床是一后碰撞斑岩型矿床，矿区内岩浆混合现象发育，而该区特殊的后碰撞环境下岩浆混合作用与成矿关系不清。本研究以研究区岩浆混合相关岩类及成矿斑岩的特征及相互间关系为切入点，通过岩石地球化学特征、Sr-Nd-Lu-Hf同位素示踪、流体包裹体特征、成矿物质来源等研究，来探讨希勒库都克矿区岩浆混合与成矿间的关系。本次取得的主要成果如下。（1）岩浆混合寄主花岗闪长岩及其中暗色包体、岩浆混合岩安山玢岩详细的岩石学、地球化学、Nd-Hf同位素研究获得岩浆混合作用过程经历了一个快速的均一化过程的重要认识。（2）成矿花岗斑岩岩石地球化学、Nd-Hf同位素特征及与岩浆混合各岩类的对比研究表明，含矿岩浆为偏基性的玄武安山质岩浆和偏酸性的花岗闪长质岩浆混合形成的安山质岩浆再次与幔源岩浆发生混合演化而来。矿床S同位素、成矿元素、流体包裹体特征均印证了成矿物质的岩浆来源，且主要来自地幔。基于此，提出复杂的壳幔岩浆混合作用及幔源岩浆的二次添加可能是希勒库都克铜钼矿床形成的重要机制。（3）岩浆混合寄主岩中流体包裹体与矿脉中流体包裹体岩相学、温度盐度、气液相成分、H、O、C同位素及石英中Si同位素的对比研究揭示了岩浆混合寄主岩→成矿斑岩→矿体的地质流体均属NaCl-CO2-H2O体系，成矿流体是岩浆混合过程中地质流体逐渐演化而来。（4）初步构建了希勒库都克地区岩浆混合与后碰撞斑岩型矿床成矿模式。