粤北白石坳地区印支期过铝质花岗岩岩相学、主微量地球化学特征

The Petrographical-Geochemical Characteristics of the Indosinian Peraluminous Granites in Baoshiao Region, NorthernGuangdong

本文选取粤北白石坳地区广泛出露的印支期花岗岩为研究对象,运用系统的野外地质调查、镜下鉴定、岩石地球化学等方法,分析了该地区花岗岩的野外地质产状、岩相学、主微量地球化学特征。本文认为白石坳地区印支期花岗岩具以下特征:(1)绝大多数岩石样品K2O/Na2O>1,δ<3.3,属于高钾钙碱性系列,A/CNK>1.1,为S型过铝质花岗岩;(2)稀土元素具有轻稀土相对富集和重稀土相对亏损、中等负铕异常的特征(3)微量元素具有富集大离子亲石元素而亏损高场强元素的特征,Rb/Sr比值和U含量均远高于全球上地壳的平均值,属于壳源型花岗岩范畴,为区域内铀矿床的形成提供丰富的铀源。

The Indosinian granites widely exposed in Baishi region,northern GuangdongProvince,are selected as the research object in this paper.By the method of systematic field geological survey,microscopic identification and rock geochemistry,the paper in detail analyses the petrographical and geochemical characteristic of the regional Indosinian granites.The Indosinian granites in Baishi region have the following characteristics:First of all,the most rock samples belong to the high-K calc-alkaline series(K2O/Na2O>1,δ<3.3)and are defined as typical S-type peraluminous granites(A/CNK>1.1).Secondly,REE are characterized byrelatively rich LREE and poor HREE,with moderate Eu negative abnormality.Finally,LILE elements are relatively enriched and HFS elements are relatively depleted.The ratio of Rb/Sr and the content U element are significantly higher than the global average of the upper crust,Which shows that Indosinian granites belong to the category of crustal granites andprovide abundant uranium sources for the formation of uranium deposits in the region.