华南埃迪卡拉纪磷矿的沉积环境  

The Depositional Environment of Ediacaran Phosphorite Deposits,South China

作　　者：肖朝益 张正伟[1] 何承真 温汉捷[1] 樊海峰[1] 

机构地区：[1]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵阳550002 [2]中国科学院大学,北京100049

出　　处：《矿物岩石地球化学通报》2018年第1期121-138,共18页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(41573011);中国科学院西部之光项目;中国科学院青年促进会项目(2016-09-1)

摘　　要：为查明华南埃迪卡拉纪磷矿床的沉积环境,本文选取瓮安磷矿区和开阳磷矿区作为研究对象,进行了详细的矿物学、稀土元素和铁同位素的研究。研究结果表明,瓮安下磷矿层和开阳磷矿床的磷块岩中含铁矿物为黄铁矿,显示重稀土亏损、无铈异常的特征,δ^56Fe显示出一定的变化范围（分别介于-0.33‰~0.27‰和0.1‰~0.54‰之间）。瓮安上磷矿层和厦安磷矿床、英坪磷矿床的磷块岩中含铁矿物为铁氧化物,δ^56Fe在~0‰附近,具明显的负铈异常特征。稀土元素配分方面,瓮安上磷矿层呈现出＂帽子＂型的配分特征,厦安磷矿床类似于现代海水的稀土配分模式,英坪磷矿床类似于热液的稀土配分模式。瓮安下磷矿层和开阳磷矿床在还原的沉积环境中形成;厦安上磷矿层、厦安磷矿床及英坪磷矿床形成于氧化的沉积环境。In order to cipher the depositional environment in Ediacaran phosphorite deposits of South China,detailed mineralogy,REE and iron isotope studies of the Weng＇an and Kaiyang phosphorite deposits were performed in this paper.In the Kaiyang deposit and lower ore bed of the Weng＇an deposit,the iron mineral is pyrite.The REE patterns shows no cerium anomaly and HREE depletion,and the iron isotopic composition shows a certain range of variation（vary from 0.1‰-0.54‰,-0.33‰-0.27‰,respectively）.While,in the upper ore bed of the Weng＇an deposit and Xia＇an and Yingping phosphorites,iron minerals are iron-oxide with near 0‰ iron isotopic composition.Phosphorites of these deposits display obvious negative cerium anomalies in REE.A typical ＂ hat＂ type REE distribution pattern is preserved in the upper ore bed of Weng＇an depocit.A modern seawater-like REE pattern is record in the Xia＇an phosphorice,however,a hydrothermal-like REE pattern is observed in the Yingping phosphorite.The geochemical compositions imply that the lower ore bed of the Weng ＇ an deposit and Kaiyang phosphorites were formed in the anoxic sedimentary environment.The others are formed in the oxidation environment.

关 键 词：磷矿 氧化还原环境 铁矿物 稀土 铁同位素 

分 类 号：P611[天文地球—矿床学]