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Geology, Petrology and Geochemistry of Volcanic Rocks Around Arba Minch, Southern Ethiopia

Received: 24 April 2019    Accepted: 28 May 2019    Published: 12 June 2019
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Abstract

The study area is subpart of the southern main Ethiopian Rift and geographically bounded between UTM (Universal Transverse Mercator) coordinates of 662000m-669000m latitude and 336000m-341000m longitude. The main aim of this study is to investigate the geological, petrographic and geochemical properties of volcanic rocks around Arba Minch, southern Ethiopia. Both field and laboratory analytical techniques are employed to characterize minerals and the rock types. Eight thin section samples are prepared to study petrographic properties of minerals and five best representative samples are analyzed for whole rock chemistry using ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). Petrographically, samples from the porphyritic basalt show phenocrysts of olivine and plagioclase within the fine-grained groundmass. There are rounded to subrounded holes or vesicles that appear white under plane polarized light observations and dark under cross polarized light observations which further confirms vesicular nature of the basalt. Thin section sample from rhyolite outcrop shows phenocrysts of K-feldspar and quartz within tiny fine-grained groundmass of feldspar minerals. Aphanitic basalt, Porphyritic basalt, vesicular basalt, rhyolite and dolerite are the rock units found in the study area. The geochemical results of the analyzed samples indicate silica ranges of (48.5-60.1)%. Based geochemical classifications made, rock units are classified into rhyolite, basalt, hawaiite and mugherite rock types. Trace element analytical results show all samples lie on the within plate tectonic setting. The rare earth and trace element ratios and spider diagrams confirmed that most samples are derived from magmas of asthenospheric source with little crustal contamination.

DOI 10.11648/j.earth.20190803.14
Published in Earth Sciences (Volume 8, Issue 3, June 2019)
Page(s) 160-168
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This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2024. Published by Science Publishing Group

Keywords

Rift, Rock, Mineral, Basalt, Element

References
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[6] Ebinger, C. J., T. Yemane, D. J. Harding, S. Tesfaye, S. Kelley, and D. C. Rex (2000). Riftmigration and propagation: Linkage of the Ethiopian and Eastern rifts, Africa, Geol. Soc.Am. Bull.
[7] Fitton JG, James D, Kempton PD, Ormerod DS, Leeman WP (1988). The role of lithospheric mantle in the generation of late Cenozoic basic magmas in the western United States. In: Cox KG, Menzies MA, editors. Oceanic and Continental Lithosphere: Similarities and Differences.
[8] Ghebreab, W (1998). Tectonics of the Red Sea region reassessed, Earth Sci. Rev.
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[15] Sun, S. s., Mc Donough, W. F (1989). Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders, In: A.D. (Ed.), Magmatism in the Ocean Basins. Geological Society, London.
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Author Information
  • Department of Geology, Arba Minch University, Arba Minch, Ethiopia

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  • APA Style

    Gosaye Berhanu. (2019). Geology, Petrology and Geochemistry of Volcanic Rocks Around Arba Minch, Southern Ethiopia. Earth Sciences, 8(3), 160-168. https://doi.org/10.11648/j.earth.20190803.14

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    ACS Style

    Gosaye Berhanu. Geology, Petrology and Geochemistry of Volcanic Rocks Around Arba Minch, Southern Ethiopia. Earth Sci. 2019, 8(3), 160-168. doi: 10.11648/j.earth.20190803.14

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    AMA Style

    Gosaye Berhanu. Geology, Petrology and Geochemistry of Volcanic Rocks Around Arba Minch, Southern Ethiopia. Earth Sci. 2019;8(3):160-168. doi: 10.11648/j.earth.20190803.14

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  • @article{10.11648/j.earth.20190803.14,
      author = {Gosaye Berhanu},
      title = {Geology, Petrology and Geochemistry of Volcanic Rocks Around Arba Minch, Southern Ethiopia},
      journal = {Earth Sciences},
      volume = {8},
      number = {3},
      pages = {160-168},
      doi = {10.11648/j.earth.20190803.14},
      url = {https://doi.org/10.11648/j.earth.20190803.14},
      eprint = {https://download.sciencepg.com/pdf/10.11648.j.earth.20190803.14},
      abstract = {The study area is subpart of the southern main Ethiopian Rift and geographically bounded between UTM (Universal Transverse Mercator) coordinates of 662000m-669000m latitude and 336000m-341000m longitude. The main aim of this study is to investigate the geological, petrographic and geochemical properties of volcanic rocks around Arba Minch, southern Ethiopia. Both field and laboratory analytical techniques are employed to characterize minerals and the rock types. Eight thin section samples are prepared to study petrographic properties of minerals and five best representative samples are analyzed for whole rock chemistry using ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). Petrographically, samples from the porphyritic basalt show phenocrysts of olivine and plagioclase within the fine-grained groundmass. There are rounded to subrounded holes or vesicles that appear white under plane polarized light observations and dark under cross polarized light observations which further confirms vesicular nature of the basalt. Thin section sample from rhyolite outcrop shows phenocrysts of K-feldspar and quartz within tiny fine-grained groundmass of feldspar minerals. Aphanitic basalt, Porphyritic basalt, vesicular basalt, rhyolite and dolerite are the rock units found in the study area. The geochemical results of the analyzed samples indicate silica ranges of (48.5-60.1)%. Based geochemical classifications made, rock units are classified into rhyolite, basalt, hawaiite and mugherite rock types. Trace element analytical results show all samples lie on the within plate tectonic setting. The rare earth and trace element ratios and spider diagrams confirmed that most samples are derived from magmas of asthenospheric source with little crustal contamination.},
     year = {2019}
    }
    

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    T1  - Geology, Petrology and Geochemistry of Volcanic Rocks Around Arba Minch, Southern Ethiopia
    AU  - Gosaye Berhanu
    Y1  - 2019/06/12
    PY  - 2019
    N1  - https://doi.org/10.11648/j.earth.20190803.14
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    AB  - The study area is subpart of the southern main Ethiopian Rift and geographically bounded between UTM (Universal Transverse Mercator) coordinates of 662000m-669000m latitude and 336000m-341000m longitude. The main aim of this study is to investigate the geological, petrographic and geochemical properties of volcanic rocks around Arba Minch, southern Ethiopia. Both field and laboratory analytical techniques are employed to characterize minerals and the rock types. Eight thin section samples are prepared to study petrographic properties of minerals and five best representative samples are analyzed for whole rock chemistry using ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). Petrographically, samples from the porphyritic basalt show phenocrysts of olivine and plagioclase within the fine-grained groundmass. There are rounded to subrounded holes or vesicles that appear white under plane polarized light observations and dark under cross polarized light observations which further confirms vesicular nature of the basalt. Thin section sample from rhyolite outcrop shows phenocrysts of K-feldspar and quartz within tiny fine-grained groundmass of feldspar minerals. Aphanitic basalt, Porphyritic basalt, vesicular basalt, rhyolite and dolerite are the rock units found in the study area. The geochemical results of the analyzed samples indicate silica ranges of (48.5-60.1)%. Based geochemical classifications made, rock units are classified into rhyolite, basalt, hawaiite and mugherite rock types. Trace element analytical results show all samples lie on the within plate tectonic setting. The rare earth and trace element ratios and spider diagrams confirmed that most samples are derived from magmas of asthenospheric source with little crustal contamination.
    VL  - 8
    IS  - 3
    ER  - 

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