湖北省放马山磷矿物质组分及元素地球化学特征

COMPOSITION AND ELEMENT GEOCHEMISTRY OF FANGMASHAN,HUBEI PROVINCE

湖北省放马山磷矿层位为震旦系陡山沱阶。在对其第一磷矿层(Ph1)和第三磷矿层(Ph3)物质组成、结构、构造等研究的基础上,对比Ph1和Ph3的化学分析数据,Ph1的I、Sr、Ba和Cd含量相对富集,表明其形成与有机质和微生物作用关系比Ph3更大。采用Co/Ni、Th/U来做相近元素的比值分析,Co/Ni值小于1、Th/U值大于1,在logw(U)-logw(Th)关系图中,Ph1和Ph3磷块岩样品点几乎都落在热水沉积区,表现出热水沉积成因的地球化学特征。稀土元素的北美页岩标准化配分模式图呈宽阔的帽状图形,并显示明显的Ce负异常,反映在正常的海相沉积过程中有海相热水流的加入。

The phosphorites of Fangmashan deposit is hosted in Doushantuo stage of simian system, On the basis of study on phosphate layers Phi and Ph3 material composition, structure, tectonic, compare chemical analysis data of Phl and Ph3, Phl are rich in I, Sr, Ba, Cd, Indicate that the formation of Phl concerned with organic matter and microbe more than Ph3. This paper uses the Co/Ni, Th/U to do similar element ratio analysis, Co/Ni is less than 1, Th/U is greater than 1, in logw （U） -logw （Th） diagram, Phi and PH3 PhosPhate rock sample point almost fall in hot water sedimentary area, show the geochemical characteristics of hydrothermal sedimentary origin. PAAS normalized REE concentrations plotted against respective atomic numbers are characterized by slight MREE enrichment , showing hat-shaped REE pattems. The patterns show obvious negative Ce anomalies, suggesting that Fangmashan PhosPhorites are of normal marine deposition plus hydrothermalism origin.