桂北摩天岭花岗岩体的地质地球化学特征及其意义

为研究摩天岭花岗岩体的地质及地球化学特征，分别测定了该岩体的主量元素，微量元素和稀土元素含量，并作了图解分析。结果表明，摩天岭花岗岩体在主量元素特征上表现为富钾，低钠、较低的／7,（Na2O）／n（K2O），贫钙镁，富铁，w（A）／w（CNK）〉1．1，为强过铝质，具有华南产铀花岗岩的基本特征。微量元素特征表现为：富集强不相容元素，尤其是Rb、Th元素；而贫弱不相容元素zr、Hf、Sm、Y和Yb。Sr元素呈强烈亏损。稀土总含量较低，具有较低的轻重稀土分异，略富集LREE，亏损HREE，具有较低的埘（La）／w（Yb）。岩体具有强烈的负8Eu异常。摩天岭花岗岩体的岩石类型及地球化学特征表明其是S型花岗岩，其形成的构造环境判别图解显示摩天岭岩体具有火山弧花岗岩和同碰撞花岗岩的双重属性。

Geological and Geochemical Characteristics of Granite in Motianling, North Guangxi Province

The granite pluton structure locates in uplift of the core in north guangxi, the fold and upheaval compound part southwest of the Yangtze plate. The rock is mainly consisted of biotite - granite, formed in Xuefengian. Geochemical data characteristics with w （A）/w （CNK） 〉 1.1, rich aluminum, rich potassium low sodium, low n （Na2O）/n （K2O）, the poor calcium magnesium rich iron, show the basic natures of granite uranium in south China. Trace element features are： enrichment in incompatible elements, especially Rb, Th, and poor in incompatible elements, such as Zr, Hf, Sm, Y and Yb. Sr element is strongly losses. The total content of REE in granite body is low, displaying slight gravity differentiation, light LREE enrichment, HREE defect, and have a low w （La）/w （Yb） ratio. Moreover, the rock group has an obvious negative Eu anomaly. Rock type and geochemistry characteristics show that the Motianling granitoid belongs to S- type granite. Its environmental structure discrimination diagrams indicate Motianling rock group has the dual nature of volcanic arc granite and collision with granite.