探索胶东金矿成矿物质来源的新证据—岩石学、矿物学约束

Jiaodong gold mineralization area（JGA for short）has received tremendous international attention in the research of gold mineralization. Previous researches have got quite a few study fruit on JGA, and in some extent have known the geological setting, the regional structure, the magmatism, the metallogenetic fluid and the metallogenic mechanism of the JGA. But the ore-forming material sources is often ambiguous and raises wide concerns. It is still a bottle neck limiting the development of the further research, due to the lacking of the direct petrological or mineralogical vidence. A great deal of evidence indicates that the "Au elements-enriched event" is the inevitable existing process in mineralization of gold deposits. And this event should leaves behind a fingerprint of petrology of mineralogy. This application chooses Linglong and Jiaojia gold ore deposits as the research object with a focus on an analysis of deep xenoliths, gold-carrying minerals characteristics and magma- materials evolution mechanism through the following research: (1) Detailed field investigationon the field geological characteristics of intrusive rocks, intrusive dyke, deep xenoliths, and gold ores, including their distribution, zoning and mineral assemblage characteristics; (2) Systematic microscopic observation on the microscopic characteristics of the orebody, mineral assemblages, texture and structure, try to analyze and define the petrographical composition; (3) High-accuracy mineralogical, geochemical and Tof-SIMS micro area analysis with focuses on the research of the petrochemistry characteristics, the elemental geochemistry characteristics, the Au enrichment regularities and the symbiosis relation between magma- materials evolution. (4) Comprehensive study on the activization, transportation, concentration of the gold-carrying minerals so as to set up a magma- materials evolution model of JGA. Obviously, This project will help to understand the ore-forming material sources and the Au elements geochemical behavior during magmatic processes. This achievement in research would provide important information for further research and prospecting of such deposits.

胶东金矿一直是国内外研究的热点。前人在构造、岩浆、流体或成矿机制方面取得了大量的研究成果，但金成矿物质来源问题却一直颇具争议，成为严重阻碍进一步研究的瓶颈，其根本问题在于各学说都缺乏相对直接的岩石学证据。金成矿过程中，必会在某个地质阶段发生金的富集，那么就应会留下相应的痕迹。为此，本次工作拟以玲珑和焦家金矿为研究对象，通过充分的野外地质调查，在已有样品基础上，寻找更多的可佐证金来源的富金岩体、岩石包体（/矿物巨晶）或者寄主于硅酸盐矿物中的载金矿物熔融包裹体等岩石学证据，进行详细的岩相学观察，并辅以高精度的矿物学、元素地球化学及元素微区分布图谱分析研究，约束金成矿物质来源、了解在岩浆过程中金的地球化学行为，并在此基础上讨论金元素在岩浆、流体系统中的演化特征和富集机制。通过开展这项探索性的研究工作，不仅能约束胶东地区金矿成矿物质来源问题，也可为国内外的金矿相关研究提供重要的资料和论据。

本项目按照设计的总体思路，通过详细的野外地质调查，并结合科学合理的测试研究手段取得了一些新的成果，找到了部分反映成矿物质来源的线索，丰富了成矿理论和找矿思路。（1）对胶东地区与成矿密切的13个侵入体进行了详细系统的岩相学、矿物学、矿物元素分布扫面、主微量稀土岩石地球化学、同位素地球化学和年代学研究，大体查明中生代132-108Ma胶东地区主要侵入体的时代和分布规律。（2）发现了指示胶东地区金元素来源的岩浆演化信息。一是首次在栾家河金矿深部2000m 处发现含矿黑云母二长岩，发现金和硫化物除了以浸染状的形式分布于硅酸盐矿物晶体间，还存在硫化物以熔融包裹体的形式保存于黑云母、角闪石、斜长石等硅酸盐矿物中，二者具有成因联系。二是在西涝口金矿深部黑云闪长玢岩中通过重砂分选出3粒自然金，经详细的岩相学观察，发现该侵入体中含大量的原生金属矿物，岩石地球化学分析表明这套黑云闪长玢岩的金含量高于其他中生代侵入体，该岩体年龄为108.8±2.2Ma，初步研究认为，这套岩体可能与西涝口金矿床的成矿过程关系密切，胶东东部应该存在110Ma±的成矿事件。三是首次系统研究了昆嵛山杂岩体中的含矿的细粒二长花岗岩初步认为这类矿床是在岩浆演化过程中成矿的，是在岩浆作用晚期的不均匀分布的产物，没有受到后期的热液或者蚀变作用。（3）初步在昆嵛山岩体中识别出一种与细粒花岗岩有关的新类型金矿床，有以下特点：一是矿体为达到金工业品位的新鲜细粒细粒黑云二长花岗岩；二是载金矿物以黄铁矿为主，主要以晶隙金、包体金的形式赋存于硅酸盐矿物和石英矿物间隙或矿物中；三是未见到明显的构造活动和热蚀变。初步研究认为这类型金矿床是在岩浆过程中，由于岩浆的结晶分离或者不混溶作用，而导致成矿的，可初步视为“岩浆型金矿”。这类矿床的发现将改变传统的胶东金矿找矿思路，提高金矿的找矿潜力。