镇安米粮地区微细浸染型层控金矿床的形成与构造演化的关系

THE RELATIONSHIP BETWEEN THE FORMATION OF THE MICRO-DISSEMINATED STRATABOUND GOLD DEPOSITS AND THE STRUCTURAL EVOLUTION IN MILIANG AREA, ZHEN'AN COUNTY

构造解析和典型矿床研究相结合分析了构造在金矿床形成过程中的重要作用。同生断裂活动伴随了构造－火山热液作用，提供了深部金等成矿物质。在此构造背景下，沉积了以重力流为主的陆源细碎屑岩与颗粒碳酸盐岩高频交替的岩相垂向组合，具有利于金活化、富集的初始元素组合（Ａｕ、Ｓｂ、Ａｓ），构成了金的矿源层。后期构造递进变形作用发育的韧－脆性剪切变形叠加，及与之伴随的多期多阶段蚀变矿化，致使矿源层中的易释放金活化聚集，形成工业矿体。

The important role of structure in the fOrmation of the gold deposits is analysed in this paper by means of the combination of structural analysis with typical deposit study, The contemporaneous faulting was accompanied by tectonic-volcanogene hydrothermal activity noted for volcanic crystal fra-gments and trace elements as well as sulfur isotopes in diagenetic pyrite,which might have provided ore-forming materials for gold at depth. In such an environment,the high-frequency alternate vertical lithofacies association of terrigenous fine detrital rock and grained carbonate rock was deposited,reflecting the relative falling of the sea level and the dominance of gravity flow alld coI1taining initially-enriched Au-Sb-As association favorable for activation and concentration of gold to form the gold source bed.The gold source bed went through four late s tages of structural progressive deformation accompanied by multi-phase and poly-stage al teration、and mineralization,in which the inherited evolution of the auriferous pyrite and arsenopyrite re-veals the correlation between Au and As;in the process of deformation,thesuperimposition of the second and the third stage ductile-brittle shear de-formation caused the enrichment of the easily-activated gold to form indus-trial orebodies or even rich prapockets. AI though the orebodies in the four ore blocks show some differences in mode of occurrence,the mechanism of gold enrichment is quite the same during the progressive deformation.