石英脉型白钨矿矿床的成因与构造背景-以延边东部钨矿为例

The scheelite-quartz lode deposit is a rarely seen tungsten deposit type at home and abroad. The important significance of studies on this deposit type lies on both the tungsten metallogenetic theory and guidance on ore-prospecting. Taking scheelite-quartz lode deposits recently discovered in eastern Yanbian area as examples, the metallogenic age will be determined by geochronological studies of metallogenic granitic rocks, associated dykes and the scheelite-quartz ore. Based on geochemical characteristics of strata, igneous rocks including granitic rocks and dykes associated with mineralization, as well as the scheelite-quartz ore from such typical deposits as Yangjingou and Wudaogou, the relationship between the magmatism and tungsten mineralization can be discussed by the element and isotope tracer method. Moreover, the source of ore-forming materials and ore genesis are to be explained. Rock types, rock series and geochemical characteristics of metallogenic granitic rocks and synchronous dykes, together with comparison of regional petrogenic and metallogenic events, can be used to determine the tectonic setting of the scheelite-quartz lode deposits in eastern Yanbian area. The petrogenic and metallogenic model of this type tungsten deposit is the eventual goal of the program. Some new knowledge concluded in this program is likely to play a significant role in tungsten exploration in NE China.

石英脉型白钨矿矿床是国内外少见的一种钨矿类型，其成因研究不仅能够丰富钨矿成矿理论，而且对指导找矿具有重要意义。本项目以延边东部最近发现的此类钨矿为例，通过杨金沟和五道沟等矿床中成矿相关岩体、脉岩以及矿体的年代学研究，查明钨矿的成矿时代；开展与钨矿有关的地层、花岗质岩体及同期脉岩的岩石地球化学研究，结合矿石地球化学特征研究，采用元素与同位素地球化学示踪技术，查明岩浆作用与成矿作用的关系，进而揭示成岩成矿物质来源与矿床成因。在上述研究基础上，根据成矿岩体和同期脉岩的岩石类型、岩性组合、岩石系列以及地球化学特征，以及区域成岩成矿事件的对比研究，确定延边东部石英脉型白钨矿矿床的成矿构造背景，最终建立成岩成矿模型，并指导区域找矿。

本项目采用野外调研、岩相学和矿相学鉴定、流体包裹体测试、元素-同位素地球化学分析、同位素测年等方法，对延边东部珲春地区的杨金沟、五道沟等石英脉型白钨矿矿床（点）的成矿地质条件、矿床地质地球化学特征、成矿流体特征、矿床成因、成矿时代和构造背景等进行了研究。结果表明，晚古生代五道沟群浅变质岩系、中-晚二叠世中酸性侵入体为区内钨矿形成提供了有利的地层和岩浆岩条件，北东-北北东向、北西-北北西向断裂构造及五道沟群变质岩中的层间破碎带为主要控矿构造；区内钨矿床均为白钨矿-石英脉型，成因类型为与岩浆热液有关的中温热液脉型，成矿流体属中温、中低盐度、低密度的NaCl-H2O-CO2±CH4±N2体系，流体不混溶作用是钨矿的重要成矿机制；钨矿的成矿时代为二叠纪末期（250-260Ma），其中，杨金沟矿床的含矿石英闪长岩锆石U-Pb年龄为251.9±2.2 Ma，白钨矿的Sm-Nd等时线年龄为251.7±2.9 Ma；杨金沟矿床含矿石英闪长岩体即为成矿岩体，成因为钙碱性、弱过铝质的I型花岗质，成岩成矿物质来源于亏损地幔，并受到地壳物质的混染。根据成矿岩体、赋矿地层的岩石学和岩石地球化学特征，以及区域构造演化最新研究成果，综合认为延边东部钨成矿作用发生于活动大陆边缘的构造背景，与古亚洲洋俯冲闭合有关。基于上述研究资料与成果，建立了该区钨矿的区域成矿模型和典型矿床成矿模式。本项研究，全面提高了延边东部新发现钨矿床的理论认识水平，为区域成矿规律研究、资源潜力评价和地质找矿提供了理论支撑。依托项目，培养博士和硕士研究生3名，发表科研论文9篇，7人次参加国内外学术会议。