埃塞俄比亚西部布雷地区A型花岗岩成因及地质意义  

Petrogenesis of A-Type Granite and Geological Significance of Bure Area,Western Ethiopia

作　　者：向文帅 姜军胜[2] 雷义均 赵凯[2] Xiang Wenshuai;Jiang Junsheng;Lei Yijun;Zhao Kai(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Wuhan Center,China Geological Survey,Wuhan 430205,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]中国地质调查局武汉地质调查中心,湖北武汉430205

出　　处：《地球科学》2021年第7期2299-2310,共12页Earth Science

基　　金：中国地质调查局项目“北部非洲大型铜金资源基地评价”(No.121201009000172708);中国地质调查局项目“埃及及邻区矿产资源潜力评价”(No.DD20160109)。

摘　　要：为进一步约束埃塞俄比亚西部地区区域地质构造演化,选取埃塞俄比亚西部布雷地区岩浆岩开展岩石地球化学、年代学等分析.结果显示:布雷岩体具有相对较高的SiO_(2)(66.4%~68.5%)、K_(2)O(4.56%~4.87%)及铁值[TFeO/(TFeO+MgO]为0.75~0.79,相对较低的MgO(0.80%~1.3%)、CaO(2.01%~2.36%)和A/CNK(0.89~0.96),富集Zr、Hf、Y、Ga等元素,亏损Sr、P、Ti和Eu元素,显示了A型花岗岩的特征.锆石LA-ICP-MS U-Pb加权平均年龄为631±4 Ma,代表了东非造山运动后伸展阶段.锆石ε_(Hf)(t)值为3.2~9.1,具有一定的不均一特征.布雷A型花岗岩形成于碰撞造山的后伸展环境.岩石地球化学及Hf同位素特征表明布雷岩体主体可能来源于减薄的岩石圈地幔玄武质岩浆,其后经历了广泛的结晶分异作用而形成.In order to furtherly constrain the evolution of regional geological structure in the western Ethiopia,we selected the magmatic rocks from the Bure area of western Ethiopia for petrogeochemical and chronologic analysis.The Burequartz monzonite in western Ethiopia has relatively high SiO_(2)(66.4%to 68.5%),K_(2)O(4.56%to 4.87%),and iron value(TFeO/(TFeO+MgO)is0.75 to 0.79),and relatively low MgO(0.8%to 1.3%),CaO(2.01%to 2.36%),and A/CNK(0.89~0.96),withthe characteristic that areemriched in elements such as Zr,Hf,Y,and Ga,and depleted Sr,P,Ti,and Eu elements,which reveal the feature of Atype granite.The zircon LA-ICP-MS U-Pb age of the rock is 631±4 Ma(MSWD=2.9),representing the extension stage of the East African orogenic movement.Theε_(Hf)(t)values of Bure A-type granite range from 3.2 to 9.1(average=7.3),showing a relatively inhomegeneous feature.The Bure A-type granite formed in the post-stretching environment of the East African orogenic movement.Thewhole rock geochemistryand Hf isotopic characteristicssuggest that the Bure A-type granite may originated from basaltic magma in the thinned lithospheric mantle,and then formed through extensive crystallization differentiation.

关 键 词：锆石U-PB年代学 地球化学 A型花岗岩 埃塞俄比亚西部布雷地区 

分 类 号：P581[天文地球—岩石学]