埃塞俄比亚施瑞地区花岗岩地球化学特征及构造环境  

Geochemistry and Tectonic Setting of Granites from Shire Region,Ethiopia

作　　者：韩世礼[1,2] 张术根[2] 柳建新[2] 丁俊[2] 张文山[2,3] 

机构地区：[1]南华大学核资源工程学院,湖南衡阳421001 [2]中南大学地球科学与信息物理学院,湖南长沙410083 [3]中色金地资源科技有限公司,北京100012

出　　处：《地球科学（中国地质大学学报）》2014年第1期10-20,共11页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(No.41174103);2010年国外矿产资源风险勘查专项资金项目(No.管理财[2010]211号)

摘　　要：埃塞俄比亚北部施瑞地区具有造山前、造山期和造山后3种花岗岩类型,全岩Sm-Nd等时线测年结果表明,造山前和造山后花岗岩成岩年龄分别为824.4±15.5Ma和517.9±5.8Ma.3类花岗岩主量元素和稀土微量元素成分存在明显差异,其中造山前花岗岩属于低钾过铝质花岗岩,稀土分配模式属轻稀土弱富集型,富集大离子亲石元素,亏损P和Ti高场强元素;造山期花岗岩为准铝质高钾钙碱性花岗岩,稀土分配模式属轻稀土富集型,富集大离子亲石元素和高场强元素;造山后花岗岩为弱过铝质高钾钙碱性花岗岩,稀土分配模式具强烈铕亏损的海鸥型,富集大离子亲石元素,明显亏损P和Ti高场强元素.综合研究表明:造山前和造山期花岗岩均为I型幔源花岗岩,构造环境处于被动大陆边缘-火山岛弧环境;造山后花岗岩为A2型壳源主花岗岩,是在洋盆关闭和阿拉伯-努比亚地盾成熟后,由减薄的地壳部分熔融产生.There are pre-,syn-,and post-orogenic granites in Shire region of northern Ethiopia.Whole rock Sm-Nd isochron dating results show that diagenetic age of pre-,and post-orogenic ages are 824.4±15.5Ma and 517.9±5.8Ma respectively.Major,rare-earth and trace elements of three kinds of granite are obviously different.The pre-orogenic granites are relatively low in MgO and high in SiO2,belonging to the peraluminous series granite,with low K content and slight light REE enrichment,high large-ion lithophile element abundance and relative depletion of HFSE.The syn-orogenic granite belongs to the quasi-aluminous rock and high-potassium calc-alkaline granite,with the light REE enriched pattern,high large-ion lithophile element and HFSE abundances.The post-orogenic granite belongs to the weakly peraluminous high-potassium calc-alkaline gran-ite,which has the chondrite-normalized REE patterns in the type of＂gull＂with severe depletion in Eu.The large-ion lithophile elements are concentrated,while P and Ti are severely depleted here.Comprehensive study shows both the pre-and syn-orogenic granites are I-type mantle-source granites in the passive continental margin-volcanic island arc tectonic setting;the post-orogenic granites are A2-type crust-source major granites,which were formed from the melting of thinner crust after the closure of oceanic basins and the growth of Arabian-Nubian shield.

关 键 词：花岗岩 地球化学 构造 SM-ND同位素 埃塞俄比亚 施瑞 

分 类 号：P588.12[天文地球—岩石学] P595[天文地球—地质学]