桂东北豆乍山花岗岩年代学与地球化学特征  

Geochemical characteristics and geochronology of the Douzhashan granite,northeastern Guangxi Province,China.

作　　者：谢晓华[1] 陈卫锋[1] 赵葵东[1] 孙涛[1] 陈培荣[1] 蒋少涌[1] 朱康任 李妩巍 

机构地区：[1]南京大学地球科学与工程学院,内生金属成矿机制研究国家重点实验室,南京210093 [2]核工业二三0研究所,长沙410011

出　　处：《岩石学报》2008年第6期1302-1312,共11页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40372036,40702012);教育部科学研究重大资助项目(306007);核工业地质局“十一五”生产科研项目《湘南桂北花岗岩型、外接触带型铀矿控矿因素核找矿模式研究》共同资助

摘　　要：豆乍山花岗岩主要由中细粒二云母二长花岗岩构成,是桂东北苗儿山复式花岗岩体中段的一个重要产铀的岩体。单颗粒锆石 SHRIMP U-Pb 年龄为228±11Ma,属于印支期岩浆活动产物。地球化学特征显示该花岗岩以过铝、富硅、富碱和低 CaO/Na_2O 比值为特征,微量元素主要富集 Rb、Th、U 和 Ta,亏损 Sr、Ba 和 Ti。稀土总量30.24×10^(-6)～139.18×10^(-6),轻稀土轻微富集(LREE/HREE=4.00～6.35,(La/Yb)_N=3.24～6.74),Eu 亏损明显(δEu=0.14～0.19)。结合其它相关地质资料,表明豆乍山花岗岩是壳源型花岗岩,是在印支运动晚期地壳伸展—减薄的构造背景下,成分为泥质的变质岩通过低程度部分熔融方式而形成。The Douzhashan granite is mainly composed of medium-to fine-grain two-mica monzonitic granite and great importance because of hosting several uranium ore deposits within the middle of the Miaoershan granitic complex in northeastern Guangxi province. Signle zircon SHRIMP U-Pb dating yields 228 ± 11Ma, which suggests that this granite formed during Indosinian. In geochemistry, it is strongly peraluminous and characterized by enrichment of silicon, alkalis, Rb, Th, U and Ta, low CaO/Na2O ratios, depletion of Ba, Sr and Ti. The ∑REE has the range of 30.24×10^-6 - 139.18×10^-6, slight enrichment of LREE （ LREE/HREE = 4.00 - 6.35, （La/Yb）N = 3. 24 -6. 74 ）, and strong depletion of Eu （δEu = 0. 14 -0. 19 ）. According to correlative geological data, the Douzhashan granite belongs to crust sourced type granite and was derived from partial melting of metamorphic rocks under a tectonic setting of thinning and extension of crust during the late Indosinian period.

关 键 词：锆石SHRIMP U-PB定年 印支期 元素地球化学 豆乍山花岗岩 桂东北 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]