甘肃阳山超大型热液金矿床的成矿特征

从阳山超大型金矿床的区域构造演化发展背景、成矿地质地球化学等特征进行的研究与分析表明,它是形成、产出在中新生代活化造山带、地壳高位浅成的中低温热液型超大型金矿床。从大地构造成矿学的研究途径,对其成矿流体与成矿物质的源区类型、形成与演化的构造环境、成矿作用的地质成因类型、成矿流体传输与聚集的构造系统等方面的初步研究表明成矿流体是变质与非变质的复杂混合体系,主要由基底、盖层中的构造热动力区域变质流体+重熔花岗岩浆热变质流体+岩浆热液等,组成多成因类型混合成矿流体,并受到同生水、大气降水的混染。因此,阳山金矿主要是由混合型变质成矿流体与岩浆热液成矿流体叠加形成,具有多因复成成矿特征的超大型中低温热液金矿床。

METALLOGENIC FEATURES OF THE YANGSHAN SUPER-LARGE HYDROTHERMAL GOLD DEPOSIT IN GANSU

Research and analysis were carried out on Yangshan super-large gold deposit in terms of regional background for tectonic evolution and development and geological and geochemical characteristics for metallogenesis, and the results indicate that it is a hydrothermal (medium to low temperature type) super-large gold deposit formed in Mesozoic to Cenozoic activated orogens or at hypabyssal positions in the crust. In geotectonics and metallogeny, a preliminary study was performed on the type of source region for metallogenic fluid and substance, structural setting for its formation and evolution, genetic types of metallogenesis, and structural system for migration and accumulation of metallogenic fluid, and the results demonstrate that the metallogenic fluid is a complex system covering both metamorphic and unmetamorphic types and consisting mainly of regional metamorphic fluid due to structural thermodynamic forces in basement or in cover, thermal metamorphic fluid due to remelted granitic magma and hydrothermal fluid due to magma, and this complex hydrothermal system may be additionally contaminated by connate water and atmospheric precipitation. As a result, Yangshan gold deposit is mainly derived from metallogenesis of mixing metamorphic fluid and magmatic hydrothermal fluid, hence showing multiple genetic and compounding metallogenic features, typical of a super-large hydrothermal (medium to low temperature) gold deposit.