Publicado

2022-09-08

Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia

Petrogénesis de rocas Neoproterozoicas del área de Megele, Oeste de Etiopía

DOI:

https://doi.org/10.15446/esrj.v26n2.98451

Palabras clave:

Petrogenesis, Geochemistry, S-type granite, Fractional crystallization, Megele (en)
cristalización fraccionada; geoquímica; Megele; Neoproterozoico; petrogénesis; granitos tipo S (es)

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Autores/as

  • Temesgen Oljira Pan African University Institute of Life and Earth Science (Including Health and Agriculture), PAULESI https://orcid.org/0000-0002-5423-7914
  • Olugbenga Akindeji Okunlola Department of Geology, Faculty of Natural Science, University of Ibadan
  • Akinade Shadrach Olatunji Department of Geology, Faculty of Natural Science, University of Ibadan
  • Dereje Ayalew Department of Geology, Faculty of Natural Science, Addis Ababa Universit
  • Bekele Ayele Bedada Department of Geology, Pan African University, Life and Earth Sciences Institute, University of Ibadan, Ibadan, Nigeria

The Western Ethiopian Shield is underlain by volcano-sedimentary terranes, gneissic terranes, and ophiolitic rocks intruded by different granitoid bodies. The Megele area is part of Western Ethiopian Shield and consist of a low-grade volcano-sedimentary zone that has been intruded by mafic (dolerite dyke) and granitoid intrusions (granodiorite, diorite, granite gneiss). To establish the origin of the distinctive lithologies of the locality and evaluate its mineral potential, petrological, petrographical, and geochemical characterization of these rocks were carried out. Hence, the lithological, geochemical, and petrogenetic features of the Neoproterozoic granitoid intrusives and associated metavolcanic, were illustrated through a combination of field mapping, petrological, and geochemical analysis. The petrological result obtained from the thin section analysis of the granitoids and metabasalt from Megele area indicates that, these rocks has been metamorphosed from lower green-schist facies to lower amphibolite facies as denoted by mineral assemblages such as albite + muscovite + prehnite+ quartz and actinolite + hornblende + epidote + garnet. The major and trace element geochemical analysis of granodiorite, diorite, and granite gneiss revealed that the rocks in the studied area were mainly calc-alkaline and peraluminous in nature in the SiO2 versus Na2O+K2O and A/NK versus A/CNK, the details of the results on the major and rare elements are stated in the result section  respectively. The granitoids are S-type granites revealed silica saturated rock formed at the volcanic arc subduction (VAG) to syn-collisional (syn-COLD) tectonic setting by fractionation of LREE-enriched, HREE-depleted basaltic magma with considerable crustal input. This basaltic magma seems to be generated from the LREE-enriched, HREE-depleted mantle. In conclusion, the metabasalt is sub-alkaline (tholeiitic), metaluminous bodies generated at mid-oceanic ridge tectonic setting by partially melting of HREE-depleted and LREE-enriched basaltic magma. The magma sources are associated with the reworked sediment-laden crustal slabs from the subduction zone and resulted in S-type granitoid.

El Escudo Etíope Occidental está debajo de terrenos volcánicos sedimentarios, terrenos gneissicos y rocas ofiolíticas intruidas por diferentes cuerpos granitoides. El área Megele es parte del Escudo Etíope Occidental y consiste en una zona volcánica sedimentaria de bajo grado con intrusiones máficas (diques doleríticos) y granitoides (granodioritas, dioritas, granito gneissico). En este trabajo se realizaron caracterizaciones petrológicas, petrográficas y geoquímicas de estas rocas para establecer el origen de las litologías distintivas de la localidad y evaluar su potencial mineral. A partir de las caracterizaciones se ilustraron las características litológicas, geoquímicas y petrogenéticas de los granitoides intrusivos del Neoproterozoico y metavolcánicos asociados a través de una combinación de mapeo de campo y análisis petrológicos y geoquímicos. Los resultados petrológicos obtenidos del análisis de secciones delgadas de los granitoides y metabasaltos del área de Megele indican que estas rocas han presentado metamorfosis desde facies de esquistos bajos de color verde a facies de anfibolita, como lo denotan los grupos minerales albita +  muscovita + prehnita + cuarzo y actinolita + hornblenda + epidota + granate. Los análisis geoquímicos de elementos mayores y traza de gneisses de granodiorita, diorita y granito revelaron que las rocas en el área de estudio son principalmente calcoalcalinas y peraluminosas, según los gráficos SiO2 frente a Na2O+K2O y A/NK frente a A/CNK. Los granitoides son granitos tipo S que revelan que las rocas saturadas de sílice se formaron en el arco volcánico de subducción, en un escenario tectónico syn-colisional por el fraccionamiento de magma basáltico enriquecido en tierras raras ligeras y mermado en tierras raras pesadas con una considerable aportación de la corteza. Este magma basáltico, al parecer, se generó en un manto enriquecido de tierras raras ligeras y mermado de tierras raras pesadas. En conclusión, el metabasalto es subalcalino (toleítico), y los cuerpos metaluminosos se generaron en un ambiente de dorsal mediooceánica al derretir parcialmente el magma basáltico mermado en tierras raras pesadas y enriquecido en tierras raras ligeras. Las fuentes magmáticas están asociadas con los bloques de corteza sedimentaria refundida de la zona de subducción y que produjeron granitoides tipo S.

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Cómo citar

APA

Oljira, T., Okunlola , O. A. ., Olatunji , A. S. ., Ayalew, D. y Bedada, B. A. (2022). Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia. Earth Sciences Research Journal, 26(2), 157–172. https://doi.org/10.15446/esrj.v26n2.98451

ACM

[1]
Oljira, T., Okunlola , O.A. , Olatunji , A.S. , Ayalew, D. y Bedada, B.A. 2022. Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia. Earth Sciences Research Journal. 26, 2 (sep. 2022), 157–172. DOI:https://doi.org/10.15446/esrj.v26n2.98451.

ACS

(1)
Oljira, T.; Okunlola , O. A. .; Olatunji , A. S. .; Ayalew, D.; Bedada, B. A. Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia. Earth sci. res. j. 2022, 26, 157-172.

ABNT

OLJIRA, T.; OKUNLOLA , O. A. .; OLATUNJI , A. S. .; AYALEW, D.; BEDADA, B. A. Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia. Earth Sciences Research Journal, [S. l.], v. 26, n. 2, p. 157–172, 2022. DOI: 10.15446/esrj.v26n2.98451. Disponível em: https://revistas.unal.edu.co/index.php/esrj/article/view/98451. Acesso em: 19 oct. 2024.

Chicago

Oljira, Temesgen, Olugbenga Akindeji Okunlola, Akinade Shadrach Olatunji, Dereje Ayalew, y Bekele Ayele Bedada. 2022. «Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia». Earth Sciences Research Journal 26 (2):157-72. https://doi.org/10.15446/esrj.v26n2.98451.

Harvard

Oljira, T., Okunlola , O. A. ., Olatunji , A. S. ., Ayalew, D. y Bedada, B. A. (2022) «Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia», Earth Sciences Research Journal, 26(2), pp. 157–172. doi: 10.15446/esrj.v26n2.98451.

IEEE

[1]
T. Oljira, O. A. . Okunlola, A. S. . Olatunji, D. Ayalew, y B. A. Bedada, «Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia», Earth sci. res. j., vol. 26, n.º 2, pp. 157–172, sep. 2022.

MLA

Oljira, T., O. A. . Okunlola, A. S. . Olatunji, D. Ayalew, y B. A. Bedada. «Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia». Earth Sciences Research Journal, vol. 26, n.º 2, septiembre de 2022, pp. 157-72, doi:10.15446/esrj.v26n2.98451.

Turabian

Oljira, Temesgen, Olugbenga Akindeji Okunlola, Akinade Shadrach Olatunji, Dereje Ayalew, y Bekele Ayele Bedada. «Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia». Earth Sciences Research Journal 26, no. 2 (septiembre 8, 2022): 157–172. Accedido octubre 19, 2024. https://revistas.unal.edu.co/index.php/esrj/article/view/98451.

Vancouver

1.
Oljira T, Okunlola OA, Olatunji AS, Ayalew D, Bedada BA. Petrogenesis of the Neoproterozoic rocks of Megele area, Asosa, Western Ethiopia. Earth sci. res. j. [Internet]. 8 de septiembre de 2022 [citado 19 de octubre de 2024];26(2):157-72. Disponible en: https://revistas.unal.edu.co/index.php/esrj/article/view/98451

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1. Aliyu Ohiani Umaru, Olugbenga Okunlola, Umaru Adamu Danbatta, Olusegun G. Olisa. (2023). Geochemistry and Petrogenesis of Pan-african Granitoids in Kaiama, North Central, Nigeria. Economic and Environmental Geology, 56(3), p.259. https://doi.org/10.9719/EEG.2023.56.3.259.

2. Abiola Oyebamiji, Oluwatoyin Akinola, Olusola Olaolorun, Yusuf Abdu-Raheem, Aderemi Adeoye, Mary Oguntuase. (2024). Geochemistry, petrogenesis and geological implication of granitic rocks in Igarra area, southwestern Nigeria. Applied Earth Science: Transactions of the Institutions of Mining and Metallurgy, https://doi.org/10.1177/25726838241273519.

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