埃塞俄比亚高原西北部 Mertolemariam- Abamineos 地区洪积玄武岩和盾玄武岩的岩石成因:地幔源变化评估

IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
Wubante Fikadu , Takele Chekol , Daniel Meshesha , Dejene H mariam , David Buriánek , Leta Alemayehu , Krystof Verner
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引用次数: 0

摘要

本文介绍了埃塞俄比亚高原西北部 Mertolemariam-Abamineos 地区渐新世洪积玄武岩和中新世盾状熔岩的岩石学和地球化学数据(主要元素和痕量元素),以研究喷发岩浆的岩石成因和地幔源成分的性质。默托勒马里亚姆洪积玄武岩主要具有斑岩和斜长石质地。阿巴米诺斯盾状熔岩则具有稀疏的辉石质到高度的斜长石-辉石质构造。地球化学分类显示,Mertolemariam渐新世洪积玄武岩的成分为亚碱性,而阿巴米诺斯中新世盾构熔岩的成分为高碱性。与埃塞俄比亚高原西北部的所有其他盾状玄武岩(过渡到碱性)相比,阿巴米诺斯盾状玄武岩具有独特的成分(即玄武岩)。主要元素和痕量元素组成在梅托勒马里亚姆洪积玄武岩和阿巴米诺斯盾状玄武岩之间呈现出两种截然不同的趋势。同质地幔源的碎裂结晶、部分熔融和地壳污染无法解释默托勒马利亚姆洪积玄武岩和阿巴米诺斯盾状玄武岩之间的成分变化。微量元素成分表明,Mertolemariam渐新世洪积玄武岩更有可能是由OIB(地幔羽流)和E-MORB(富集星体层)地幔成分混合生成的。阿巴米诺斯中新世盾状玄武岩来自地幔羽流(OIB)成分。LREE/MREE和LREE/HREE表明,这两个组可能都源自尖晶石和石榴石稳定场内的地幔源。相比之下,与阿巴米诺斯盾状玄武岩相比,默托勒马里亚姆洪积玄武岩是由相对较浅的部分熔融形成的。我们提出了一种解释埃塞俄比亚高原西北部岩浆成因的方案:岩石圈下的地幔羽流(类似于 OIB)最初到达时,遇到了上星体层中地球化学肥沃和富集的 MORB(E-MORB)地幔成分,从而引发了火山活动。炽热的地幔羽流引发了肥沃和富集的 MORB 的熔化,然后在羽流(OIB-like)深处的尖晶石和石榴石稳定场中发生了熔化。在埃塞俄比亚高原西北部的渐新世期间,来自地幔羽流(OIB-like)和 E-MORB 成分的熔体混合产生了亚碱性洪积玄武岩,随后,来自高级上涌地幔羽流(OIB-like)的熔体在埃塞俄比亚高原西北部产生了中新世盾状熔岩。
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Petrogenesis of flood basalts and shield basanite from Mertolemariam- Abamineos area, northwestern Ethiopian plateau: Assessments for mantle source variations

Petrographic and geochemical data (major and trace elements) are presented for Oligocene flood basalts and Miocene shield lavas from the Mertolemariam-Abamineos area, northwestern Ethiopian Plateau to examine the petrogenesis of the erupted magmas and the nature of mantle source compositions. The Mertolemariam flood basalts have mainly aphyric and plagioclase phyric textures. The Abamineos shield lavas have sparsely clinopyroxene phyric to highly plagioclase-clinopyroxene phyric textures. Geochemical classification shows that the Mertolemariam Oligocene flood basalts are sub-alkaline in composition, whereas the Abamineos Miocene shield lavas are highly alkaline in composition. The Abamineos shield has a unique composition (i.e., basanites) compared with all other shield basalts (transitional to alkaline) in the northwestern Ethiopian Plateau. Major and trace element compositions display two distinct trends between Mertolemariam flood basalts and Abamineos shield basanites. Fractional crystallization, partial melting, and crustal contamination of a homogeneous mantle source cannot explain the compositional variations between the Mertolemariam flood basalts and the Abamineos shield basanites. The trace element composition suggests that the Mertolemariam Oligocene flood basalts were more likely generated from the mixing of OIB (mantle plume) and E-MORB (enriched asthenosphere) mantle components. The Abamineos Miocene shield basanites were derived from the mantle plume (OIB) component. LREE/MREE and LREE/HREE indicate that both groups possibly originated from a mantle source within the stability field of spinel and garnet. In comparison, the Mertolemariam flood basalts were formed by a higher degree of partial melting from relatively shallow depths than the Abamineos shield basanites. We propose a scenario that explains the magmatic genesis in the northwestern Ethiopian Plateau: volcanism initiated by the initial arrival of the mantle plume (OIB-like) beneath the lithosphere, which comes across a geochemically fertile and enriched MORB (E-MORB) mantle component in the upper asthenosphere. The hot mantle plume triggered melting of the fertile and enriched MORB, and then melting occurred in the plume (OIB-like) at depth in the stability field of spinel and garnet. Melts from the mantle plume (OIB-like) and E-MORB components mixed to produce sub-alkaline flood basalts during the Oligocene in the northwestern Ethiopian Plateau Subsequently, melts from the advanced upwelling mantle plume (OIB-like) produced Miocene shield lavas in the northwestern Ethiopian Plateau.

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来源期刊
Journal of African Earth Sciences
Journal of African Earth Sciences 地学-地球科学综合
CiteScore
4.70
自引率
4.30%
发文量
240
审稿时长
12 months
期刊介绍: The Journal of African Earth Sciences sees itself as the prime geological journal for all aspects of the Earth Sciences about the African plate. Papers dealing with peripheral areas are welcome if they demonstrate a tight link with Africa. The Journal publishes high quality, peer-reviewed scientific papers. It is devoted primarily to research papers but short communications relating to new developments of broad interest, reviews and book reviews will also be considered. Papers must have international appeal and should present work of more regional than local significance and dealing with well identified and justified scientific questions. Specialised technical papers, analytical or exploration reports must be avoided. Papers on applied geology should preferably be linked to such core disciplines and must be addressed to a more general geoscientific audience.
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