Petrogenesis and Tectonic Implications of the Tertiary Choke Shield Basalt and Continental Flood Basalt from the Central Ethiopian Plateau  

作　　者：Junaid Khan Huazhou Yao Junhong Zhao Qiwei Li Wenshuai Xiang Junsheng Jiang Asma Tahir 

机构地区：[1]Institute of Geological Survey,China University of Geosciences,Wuhan,430074,China [2]State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan,430074,China [3]Faculty of Earth Sciences,China University of Geosciences,Wuhan,430074,China [4]Wuhan Center,China Geological Survey,Wuhan,430205,China

出　　处：《Journal of Earth Science》2023年第1期86-100,共15页地球科学学刊（英文版）

基　　金：supported by China Commerce Ministry (foreign-aid project (2007)420);China Geological Survey (Nos. DD20190443, DD20160109)。

摘　　要：The voluminous Choke Shield basalts and flood basalts are distributed in the central Ethiopian Plateau.They are tholeiitic in composition and have OIB-like geochemical features.The ca.23 Ma Choke Shield basalts have SiO_(2)(47.1 wt.%-59.6 wt.%),MgO(1.01 wt.%-7.8 wt.%),Na_(2)O+K_(2)O(2.7 wt.%-8.4 wt.%),and display right inclined REE patterns((La/Yb)N=21.4-24.2) with enrichment of Nb,Ta,Zr,Hf and Pb in the primitive mantle-normalized trace element diagrams.They show low initial ^(87)Sr/^(86)Sr ratios(0.703 47-0.703 77) and high ε_(Nd)(t) values(+4.4 to+5.0).In comparison,the 24Ma high-Ti(HT1) flood basalts have SiO_(2)(38.9 wt.%-50.8 wt.%),MgO(3.9 wt.%-11.4 wt.%),Na_(2)O+K_(2)O(1.6 wt.%-5.8 wt.%), and display right inclined REE patterns((La/Yb)N=24-130.3) with enrichment of Nb,Ta,Zr,Hf,and Pb.They also show low initial ^(87)Sr/^(86)Sr ratios(0.703 30-0.704 44) and highε_(Nd)(t) values(+2.2 to+5.3).Both types of basalts were contaminated by minor crustal materials and underwent fractional crystallization of clinopyroxene,plagioclase,olivine,and minor Fe-Ti oxide.The Choke Shield basalts were generated by 1%-5% melting of garnet-spinel to phlogopite-bearing spinel lherzolite in a shallow zone of the mantle plume,while the flood basalts were formed by <20% melting of amphibole-bearing garnet to garnet-spinel lherzolite in a deeper zone of the same mantle plume.The mantle source beneath the central Ethiopian Plateau was significantly heterogeneous during the Tertiary.It was characterized by EMI and EMII end-members that were formed by the metasomatism of the different components.

关 键 词：BASALT shield basalt continental flood basalt Ethiopian Plateau mantle plume 

分 类 号：P58[天文地球—岩石学]