江苏省海州式磷矿岩石地球化学特征及成矿背景

Geochemical Characteristics and Metallogenic Setting of Haizhou-Type Phosphorite Deposit in Jiangsu Province

本文对苏北地区锦屏组磷矿石及地层样品进行了岩相学及地球化学分析,研究了磷矿初始沉积环境和源区特征。磷矿类微量元素富集Ba、Pb、U、Sr,贫Th、Ta、Nb、Ti;REE配分曲线为LREE富集型,Ce负异常,表明成矿环境为陆缘海,且成矿过程受深海热水沉积和生物作用影响。Sr、Nd同位素初始值判断磷灰岩物质来源为年轻的地壳物质。绿片岩类微量元素富集Rb、Th、K,贫Th、U、Ta、Nb、Sr、Ti;REE配分曲线为LREE富集型,判断其原岩为陆源碎屑岩。(混合)片麻岩类微量元素富集Pb、Th、K,亏损Ba、Ta、Nb、Sr、Ti;REE配分曲线为LREE富集型,具地幔源区特征。

The initial sedimentary environment and source characteristics of phosphorite deposition were studied by geochemical analysis of samples from the Jinping Formation in northern Jiangsu Province.The trace element characteristics of phosphorite deposit display enrichment of Ba,Pb,U,Sr,and depletion of Th,Ta,Nb and Ti;REE distribution pattern is rich in LREE,indicating that the metallogenic environment of phosphorite is characterized by hot water deposition and biological effects in continental margin sea.Initial values of Sr and Nd isotopes indicate that the source of phosphorite is young crustal material.The trace element characteristics of green schist show enrichment of Rb,Th,K,and depletion of Th,U,Ta,Nb,Sr,Ti;REE distribution pattern is rich in LREE,implying that the origin is terrigenous clastic sediment.The trace element characteristic of(migmatitic)gneiss shows enrichment of Pb,Th,K,relatively depletion of Ba,Ta,Nb,Sr,Ti;REE distribution pattern is rich in LREE,which shows characteristics of mantle source region.