动力变形条件下Au迁移、富集的构造地球化学实验研究

TECTONO-GEOCHEMICAL RESEARCH ON Au MIGRATION AND ENRICHMENT UNDER DYNAMIC DEFORMATION EXPERIMENTS

对海南二甲金矿和广东河台金矿形成的动力学条件进行了一系列的构造地球化学模拟实验。结果表明 ,动力变形中发生了明显的力学 化学耦合作用。云母矿物变形强烈 ,塑性变形 ,定向拉长显著。黑云母发生了褪色作用 ,从褐色变成浅褐色甚至无色 ;白云母干涉色从鲜艳的蓝色变为黄色 ,甚至无色。随试验温度、压力条件的升高 ,岩石、矿物从脆性变形向塑性变形演变。动力变形还使岩石和矿物中的元素呈现化学迁移和富集作用 :云母矿物中的杂质容量降低 ,导致铁质释放 ;硫化物矿物的反射率增高 ,成矿元素特别是Au在其不同部位发生一定的变化。自然金颗粒在析出过程中 ,与Si、Fe分离而纯化。动力变形中成矿元素 (特别是Au)的迁移、富集等效应是通过压溶作用实现。

A series of tectono-geochemical experimental tests on block rock and powder samples were carried out by stimulating the dynamic condition of the Erjia gold deposit, Hainan Province and the Hetai gold deposit, Guangdong Province. Significant mechano-chemical coupling in dynamic deformation can be observed for block rock and powder samples after experiments. Mica minerals were strongly deformed, ductilely deformed and directionally elongated. Biotites were commonly discolored, usually from brown color to hazel color, even to colorlessness, while muscovites were discolored on their interference color, from bright blue to yellowish, even to colorlessness. With the elevation of test temperature and pressure, the rocks and minerals were deformed from brittleness to ductility. Dynamic deformation also caused chemical migration and enrichment of elements, especially Au, in the rocks and minerals, for example, impurity capacity in mica minerals was decreased, which induced the release of Fe; the reflectivity of sulfide minerals was elevated, which induced the variance of ore-forming elements in their different parts. Natural gold grains were observed crystallized and purified with separation from Si and Fe. The migration and enrichment of ore forming elements, especially Au, during dynamic deformation was controlled and effected by pressure solution process.