海州式磷矿床地质特征及其成矿模式

GEOLOGICAL FEATURES AND METALLOGENIC MODEL OF HAIZHOU TYPE PHOSPHORITE DEPOSIT

海州式磷矿成矿物质有多种来源。磷元素在地壳发展过程中,随着磷矿成矿作用不同阶段物化条件等改变而变化。将成矿划分为沉积、变质及改造三阶段。中元古代早期海州群锦屏组,肥东群双山组,宿松群柳坪组和虎踏石组及红安群七角山组下段为其"源",磷块岩形成后,由于变质、混合岩化交代和风化淋滤作用,使磷质活化,在一定的空间富集成矿。

The present paper has described in detail the Haizhou type phosphorite deposit in such as- pects as its metallogenic geological stting,phosphate rocks and protolith,sedimentary facies of phosphorite,gological features of ore deposits and mineralogy of apatite.Based on a study of metallogenic regularity in combination with plate structure and modern metallogenic theory,the authors divide the ore-forming process of the Haizhou type phosphorite deposit into three stages. In the sedimentary stage,deposition of phosphate rocks was controlled mainly by lithofacies-pale- ogeographical conditions and mostly took place in shallow areas of tablelands along margins of basins.In the metamorphic stage,phosphate substances and phosphorite were concentrated through such physical changes as dewatering and escape of CO_2;metasomatism of migmatization and partial melting led to remobilization and eventual crystallization or recrystallization of phos- phate substance.In the reformation stage,there were obvious creeping flow folding and weather- ing,which resulted in further enrichment of phosphate substance. The Haizhou type phosphorite deposits are characterized by multiphase and multistage min- eralization.Early strata of Middle Proterozoic,including Jinping Formation of Haizhou Group, Shuangshan Formation of Feidong Group,Liuping Formation and Hutashi Formation of Susong Group as well as lower member of Hongan Group,served as the source.After the formation of phosphorite,factors such as metamorphism,metasomatism of migmatization and weathering caused activation of phosphate substance,which was concentrated into phosphorite deposits that exhibit typical stratabound features.