Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variations
The Kesem-Megezez Section is located on the western escarpment of the main Ethiopian rift, central Ethiopia, part of the northwestern Ethiopia plateau, and hosts both flood basalts (Kesem Oligocene basalts) and shield volcano basalts (Megezez Miocene basalts) separated by an Oligo-Miocene silicic py...
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Elsevier
2023-06-01
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| Series: | Heliyon |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S240584402304464X |
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| author | Birhane Girum Takele Chekol Daniel Meshesha |
| author_facet | Birhane Girum Takele Chekol Daniel Meshesha |
| author_sort | Birhane Girum |
| collection | DOAJ |
| description | The Kesem-Megezez Section is located on the western escarpment of the main Ethiopian rift, central Ethiopia, part of the northwestern Ethiopia plateau, and hosts both flood basalts (Kesem Oligocene basalts) and shield volcano basalts (Megezez Miocene basalts) separated by an Oligo-Miocene silicic pyroclastic formation. Petrography, whole-rock trace, and major element data are presented for the Kesem Oligocene and Megezez Miocene basalts to assess their petrogenetic characteristics and the processes involved in their evolution. The Kesem Oligocene basalts are dominated by aphanitic textures, whereas the Megezez Miocene basalts are dominated by porphyritic textures. The Kesem Oligocene basalts are alkaline, whereas the Megezez Miocene basalts have transitional composition. The Kesem Oligocene basalts and Megezez Miocene basalts show distinct compositional differences. MREE/HREE and LREE/HREE show different depths of melt segregation and degrees of partial melting for the Kesem Oligocene basalts and the Megezez Miocene basalts. The geochemical differences (Zr/Nb, Rb/Zr, K/Nb, Ba/Zr and Nb/Zr) between Kesem alkaline basalts and the Megezez transitional basalts reflect the involvement of EMORB-like and OIB-like mantle sources in different proportion in their petrogenesis. Using primitive mantle, garnet- and spinel-bearing lherzolitic sources, a non-modal equilibrium melting model shows that the Kesem alkali basalt can be produced by equilibrium melting of ∼3–4% residual garnet and about 3% degree of partial melting. Whereas, the Megezez transitional basalts were formed by melting of ∼2–3% residual garnet and >3% degree of partial melting. Geochemical evidences envisioned a scenario in which magmatism started with the arrival of a mantle plume (OIB-like; aka Afar Plume), which comes across a sub-lithospheric geochemically enriched and fertile asthenospheric mantle component (EMORB-like). The upwelling of the hot mantle plume that impinging beneath the lithiosphere at ∼30 Ma generates OIB-type melts due to decompression. The thermal effect of the hot plume also triggered melting of the fertile E-MORB component in the asthenosphere at the garnet stability depth. Then, the interaction between more melts from the plume (OIB) and lesser melts from the E-MORB created flood basalts (Kesem basalts) in the Oligocene. During the Miocene, the progressive melting of OIB and E-MORB generates the plateau shield basalts (Megezez basalts). |
| first_indexed | 2024-03-13T05:01:25Z |
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| institution | Directory Open Access Journal |
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| language | English |
| last_indexed | 2024-03-13T05:01:25Z |
| publishDate | 2023-06-01 |
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| spelling | doaj.art-19d9e989e31f4860a0902a1df188b8ee2023-06-17T05:19:34ZengElsevierHeliyon2405-84402023-06-0196e17256Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variationsBirhane Girum0Takele Chekol1Daniel Meshesha2Department of Geology, College of Applied Sciences, Addis Ababa Science and Technology University, P.O. Box 16417, Addis Ababa, Ethiopia; Mineral Exploration, Extraction and Processing Center of Excellence, Addis Ababa Science and Technology University, P.O. Box 16417, Addis Ababa, EthiopiaDepartment of Geology, College of Applied Sciences, Addis Ababa Science and Technology University, P.O. Box 16417, Addis Ababa, Ethiopia; Mineral Exploration, Extraction and Processing Center of Excellence, Addis Ababa Science and Technology University, P.O. Box 16417, Addis Ababa, Ethiopia; Corresponding author. Department of Geology, College of Applied Sciences, Addis Ababa Science and Technology University, P.O. Box 16417, Addis Ababa, Ethiopia.Department of Geology, College of Applied Sciences, Addis Ababa Science and Technology University, P.O. Box 16417, Addis Ababa, Ethiopia; Mineral Exploration, Extraction and Processing Center of Excellence, Addis Ababa Science and Technology University, P.O. Box 16417, Addis Ababa, EthiopiaThe Kesem-Megezez Section is located on the western escarpment of the main Ethiopian rift, central Ethiopia, part of the northwestern Ethiopia plateau, and hosts both flood basalts (Kesem Oligocene basalts) and shield volcano basalts (Megezez Miocene basalts) separated by an Oligo-Miocene silicic pyroclastic formation. Petrography, whole-rock trace, and major element data are presented for the Kesem Oligocene and Megezez Miocene basalts to assess their petrogenetic characteristics and the processes involved in their evolution. The Kesem Oligocene basalts are dominated by aphanitic textures, whereas the Megezez Miocene basalts are dominated by porphyritic textures. The Kesem Oligocene basalts are alkaline, whereas the Megezez Miocene basalts have transitional composition. The Kesem Oligocene basalts and Megezez Miocene basalts show distinct compositional differences. MREE/HREE and LREE/HREE show different depths of melt segregation and degrees of partial melting for the Kesem Oligocene basalts and the Megezez Miocene basalts. The geochemical differences (Zr/Nb, Rb/Zr, K/Nb, Ba/Zr and Nb/Zr) between Kesem alkaline basalts and the Megezez transitional basalts reflect the involvement of EMORB-like and OIB-like mantle sources in different proportion in their petrogenesis. Using primitive mantle, garnet- and spinel-bearing lherzolitic sources, a non-modal equilibrium melting model shows that the Kesem alkali basalt can be produced by equilibrium melting of ∼3–4% residual garnet and about 3% degree of partial melting. Whereas, the Megezez transitional basalts were formed by melting of ∼2–3% residual garnet and >3% degree of partial melting. Geochemical evidences envisioned a scenario in which magmatism started with the arrival of a mantle plume (OIB-like; aka Afar Plume), which comes across a sub-lithospheric geochemically enriched and fertile asthenospheric mantle component (EMORB-like). The upwelling of the hot mantle plume that impinging beneath the lithiosphere at ∼30 Ma generates OIB-type melts due to decompression. The thermal effect of the hot plume also triggered melting of the fertile E-MORB component in the asthenosphere at the garnet stability depth. Then, the interaction between more melts from the plume (OIB) and lesser melts from the E-MORB created flood basalts (Kesem basalts) in the Oligocene. During the Miocene, the progressive melting of OIB and E-MORB generates the plateau shield basalts (Megezez basalts).http://www.sciencedirect.com/science/article/pii/S240584402304464XNorthwestern Ethiopian PlateauCrustal contaminationMantle plumeAlkali basaltsTransitional basaltsKesem Megezez |
| spellingShingle | Birhane Girum Takele Chekol Daniel Meshesha Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variations Heliyon Northwestern Ethiopian Plateau Crustal contamination Mantle plume Alkali basalts Transitional basalts Kesem Megezez |
| title | Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variations |
| title_full | Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variations |
| title_fullStr | Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variations |
| title_full_unstemmed | Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variations |
| title_short | Petrological and geochemical characteristics of flood and shield basalts from Kesem-Megezez section, northwestern Ethiopian Plateau: Implication for their mantle source variations |
| title_sort | petrological and geochemical characteristics of flood and shield basalts from kesem megezez section northwestern ethiopian plateau implication for their mantle source variations |
| topic | Northwestern Ethiopian Plateau Crustal contamination Mantle plume Alkali basalts Transitional basalts Kesem Megezez |
| url | http://www.sciencedirect.com/science/article/pii/S240584402304464X |
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