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Petrographic and geochemical data of high alkaline basalts, Sisaket Terrain, NE Thailand.

ABSTRACT: This data article presents mineralogical and geochemical data of high alkaline basalts in Sisaket province, the southern part of Khorat Plateau, NE Thailand. Under the polarized light microscope, the photomicrographs divided the basalts into olivine basalt and alkaline basalt with four textures: aphanitic, porphyritic, vesicular, and diabase. These basaltic rocks comprise olivine microphenocrysts associated with labradorite-anorthite (An_66-94), clinopyroxene, opaque minerals groundmass. In addition, nepheline is only found in alkaline basalt as groundmass. Major oxides (Na₂O+K₂O and SiO₂) suggest that Sisaket basalts are basalt, basanite, trachy basalt, and basaltic trachy-andesite. High ratio Nb/Y and low Zr/Ti classify these basalts as alkaline basalt and basanite.

SUBMITTER: Singtuen V

PROVIDER: S-EPMC8602002 | biostudies-literature | 2021 Dec

REPOSITORIES: biostudies-literature

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Petrographic and geochemical data of high alkaline basalts, Sisaket Terrain, NE Thailand.

Singtuen Vimoltip V Phajan Sirinthorn S

Data in brief 20211103

This data article presents mineralogical and geochemical data of high alkaline basalts in Sisaket province, the southern part of Khorat Plateau, NE Thailand. Under the polarized light microscope, the photomicrographs divided the basalts into olivine basalt and alkaline basalt with four textures: aphanitic, porphyritic, vesicular, and diabase. These basaltic rocks comprise olivine microphenocrysts associated with labradorite-anorthite (An<sub>66-94</sub>), clinopyroxene, opaque minerals groundmas ...[more]

PMID: 34820488

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Project 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).

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Petrographic and geochemical data of high alkaline basalts, Sisaket Terrain, NE Thailand.

Publications

Petrographic and geochemical data of high alkaline basalts, Sisaket Terrain, NE Thailand.

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