大兴安岭及邻区三期钨成矿作用

The Da Hinggan Mountains and adjacent region is located at the superposition area of the paleo-Asia Ocean, paleo-Pacific Ocean and Mongolia-Okhotsk Ocean tectonics. A lot of W deposits were discovered and explored in this region in recent years, and this metallogenic province become the second largest W metallogenic province in China. The W deposits can be divided into three types: porphyry, skarn and quartz vein types. The previous studies show that W mineralization is related to the granotoids, and these W deposits were formed in Triassic, Jurassic and Early Cretaceous. Moreover, its tungsten mineralization characteristics and ore-forming rocks have certain particularities compared with that of South China. Taking the typical W deposit as the research subject, integrated geological and chronological studies will be used to determine the temporal and spatial distribution of tungsten mineralization in metallogenic province. Fluid inclusions of quartz and wolframite are studied to find out the properties and characteristics of different types of ore-forming fluids in different stages; integrated with composition analysis of scheelite and wolframite, in-situ S, Pb isotopes of sulfides and He-Ar isotopes of pyrite analysis will be used to study the evolution of ore-forming fluids in different stages and the source of ore-forming materials. Through comprehensive granitoids realted to the W mineralization studies and comparisons, the coupling relationship between tungsten mineralization and three great tectonic events will be discussed, and the tungsten metallogenic model will be established. The research work has important theoretical significance for enriching the theory of tungsten metallogenesis, and also has important practical significance for realizing regional prospecting breakthroughs and establishing strategic resource replacement bases for tungsten deposits in China.

大兴安岭及邻区处于古亚洲洋、古太平洋及蒙古-鄂霍茨克洋构造的叠加区域，近年来，一系列钨矿床不断被勘查发现，该成矿省有望成为继华南之后我国第二大钨成矿省。初步确定区域存在斑岩型、矽卡岩型和石英脉型三种类型钨矿床，成矿与花岗岩有关，形成于三叠纪、侏罗纪和早白垩世。其钨矿化特征和成矿岩体相比华南均具有一定的特殊性。本项目拟以区域内典型钨矿床为对象，通过综合地质及成矿年代学研究，厘定成矿省钨成矿时空分布规律；通过石英、黑钨矿等流体包裹体研究，查明不同期次钨成矿流体性质及特点；结合白钨矿、黑钨矿成分分析，硫化物原位S、Pb同位素及黄铁矿He-Ar同位素分析，探讨不同期次成矿流体演化及成矿物质来源。结合成矿岩体研究，探讨钨成矿作用与三大构造事件的耦合关系，建立钨矿成矿作用模式。研究工作对丰富钨成矿理论具有重要的理论意义，对指导区域找矿突破，建立我国钨矿战略资源接替基地具有重要实际意义。

大兴安岭及邻区位于古亚洲洋、古太平洋和蒙古-鄂霍茨克洋构造的叠加区域，近年来，一系列钨矿床不断被勘查发现，使该成矿省有望成为继华南之后我国第二大钨成矿省。区域内主要存在石英脉型、矽卡岩型和斑岩型三种类型钨矿床，钨成矿作用与中生代花岗岩存在空间和成因联系。我们的主要研究内容包括钨矿床的时空分布规律、钨成矿花岗岩的成因及地球化学判别标志、成矿物质来源、成矿流体来源与演化及矿质沉淀机制、钨成矿作用与三大构造事件耦合关系。通过广泛收集成岩成矿年代学数据，我们提出大兴安岭及邻区主要存在五期成矿作用，时代分别为480–440、300–220、200–165、155–130和125–100 Ma。研究区共存在三期钨成矿作用，包括三叠纪（250–240 Ma）、早中侏罗世（200–170 Ma）和晚侏罗世–早白垩世（160–125 Ma）。其中，三叠纪钨成矿作用形成于与古亚洲洋闭合有关的同/后碰撞背景；早中侏罗世钨成矿作用形成于与古太平洋板块俯冲和蒙古-鄂霍茨克洋闭合有关的挤压背景；晚侏罗世–早白垩世钨成矿作用形成于蒙古-鄂霍茨克洋和古太平洋构造域共同控制下的后碰撞伸展背景。通过对比研究区的与钨成矿有关和无关的花岗岩的地球化学特征，我们发现早中生代钨成矿花岗岩与同时代的与钨成矿无关的花岗岩相比具有高的Rb含量和低的K/Rb比值。晚中生代钨成矿花岗岩富集Rb、Th、U，亏损Ba、Sr、P、Ti、U，与同时代与钨成矿无关的花岗岩相比具有更高的Rb/Sr和U/Th比值，更低的 (La/Yb)N、LREE/HREE、Eu/Eu*、K/Rb、Zr/Hf、Nb/Ta和Y/Ho比值。中生代钨成矿花岗岩主要起源于新生下地壳的部分熔融，早中生代钨成矿花岗岩包含少量再循环的古老地壳物质。那仁乌拉矿田的黑钨矿原位分析表明其微量元素组成受结晶化学效应和初始热液组成的双重控制，成矿物质主要来源于高分异花岗岩浆。那仁乌拉矿床的流体包裹体研究表明流体不混溶和水岩反应是钨成矿阶段黑钨矿沉淀的主要机制。研究工作对丰富钨成矿理论具有重要的理论意义，对指导区域找矿突破，建立我国钨矿战略资源接替基地具有重要实际意义。