贵州修文县铝质岩物质组成及稀土元素特征

Material Component and REE Characteristics of Aluminous Rock in Xiuwen of Guizhou

对贵州修文地区铝质岩进行了显微镜特征、常量化学成分、XRD等分析,3个综合样的主要矿物为一水硬铝石和粘土矿物,主要化学成分为SiO2、Al2O3和Fe2O3等,Al2O3主要赋存于一水硬铝石、勃姆石和粘土矿物中,SiO2主要以粘土矿物的形式存在,TiO2则主要赋存于锐钛矿中。ICP-MS测试结果表明:铝质岩中V、Cr、Zr和Sr等元素含量较高,V/Cr比值小于1,反映了成岩的富氧环境,Co/Ni比值则反映了该地区的热水沉积环境;样品明显见轻稀土元素富集特征,并且轻稀土元素含量偏高;稀土元素分配模式图表明:Eu明显呈负异常,Ce除XL-2接近1外,其他两个样均呈现负异常,反映了沉积环境为相对氧化的海相环境,海水中的Ce3+浓度较低,易被氧化为Ce4+,在搬运过程中易形成CeO2沉淀,导致铝质岩中的Ce负异常形成。

The microscopic characteristics,constant chemical component and XRD analysis on aluminous rock from Xiuwen,Guizhou,were studied.For the three comprehensive samples,the mineral components are mainly diaspore and clay mineral,the chemical components are mainly SiO2,Al2O3 and Fe2O3,Al2O3 occurs in dispore,boehmite and clay mineral,SiO2 mainly exits in the form of anatase,TiO2 mainly exits in anatase.The results of ICP-MS test show that the contents of V,Cr,Zr and Sr in the aluminous rock are higher.V/Cr is less than 1 which shows the aerobic condition in diagenesis.The value of Co/Ni performs the hot-water sedimentary environment in Xiuwen.The samples are characterized by the obvious enrichment of LREE（light rare earth element）,and the LREE is higher.The REE distribution patterning of aluminous rock shows that Eu presents negative abnormal obviously,and Ce also performs negative abnormal except for sample XL-2,which shows that the sedimentary environment is oxydic marine facies,the concentration of Ce3＋ in sea water is lower,and it easily oxidated into Ce4＋,then formed CeO2 in the process of transport,finally negative abnormal is formed.