变质细碎屑岩型金矿床的三阶段成矿模式

THREE-STAGE METALLOGENIC MODEL FOR GOLD DEPOSITS OF METAMORPHOSED FINE-CLASTIC ROCK TYPE

变质细碎屑岩型金矿床在国内外分布广泛，其中部分矿床具有超大型规模。矿床由三个阶段形成：沉积阶段在相对半封闭还原海盆中发育，常夹火山物质及热水沉积且富碳、硫、金的浊流沉积物，构成了金的矿源层；区域变质阶段随温度、压力增高，有机质破坏，粘土矿物消失，金被释出、归并、定向迁移、集中得到初步富集；成矿阶段的构造热液事件使金从变质细碎屑岩中淋出、迁移，或与其他来源的金汇集、沉淀构成矿床。矿床可分活化带型及造山带型，成矿主要为改造作用产物，少数矿床可能有岩浆叠加作用发生。

Gold deposits of metamorphosed fine-dastic rock type are wddy distributed both in Chinaand abroad, with some of them being supergiant in size. The formation of these deposits might bedivided into three stages:sedimentary stage,regional metamorphic stage and ore-forming stage.At the first stage,source beds of microclastic sediments,rich in carbon,sulfur and gold,were de-veloped in a relatively euxinic semirestricted reducing basin. At the second stage,with the increasein temperature and pressure,organic matters were destroyed,clay minerals disappeared,and goldabsorbed in these materials was released,and then attained preliminary enrichment through ori-ented migration and concentration. At the third stage ,due to the action of the structural-hydro-thermal event,gold was leached from metamorphosed microclastic rocks, moved to the favorableplace,sometimes mixed with gold from other sources during its migration l and eventually fomedore deposits through precipitation. Gold deposits of this type can be further classified into activat-ed zone type and orogenic beIt type. They are mainly products of reworking with a few affectedby magmatic superimposition.