Dolerite sills in the sandstone of Bangui, Central African Republic: geochemistry and petrology
Keywords:
lithostratigraphic synthesis, dolerite sills, sandstone, tangential tectonics, lithological succession, mylonitisation, breccia, tholeiitic affinity
Abstract
The geology of the Bangui region is not very known, although sufficient data exist. However, the lithostratigraphic synthesis remains limited. The presence of certain rock types such as dolerite sills in sandstones can be observed as a consequence of extensional tectonics in the region. The dolerites of the Bangui-Mbaiki-Boali series correspond in composition to ferruginous subalkaline basalts of the tholeiite affinity. They are enriched in LILE, HFSE and LREE with low concentrations of Ni and Cr, and have experienced fractional crystallization with fractionation of olivine and pyroxene. Parental magmas were formed in shallow conditions of garnet instability. They are characterized by a high degree of oxidation and an increased content of fluid. The source for the dolerites could be enriched protoliths from the subcontinental lithospheric mantle. The Bangui dolerites were formed in an intraplate setting.
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References
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2. Poidevin J.L. Trainings of the Precambrian superior of the area of Bangui (R.C.A.).Bul. Soc. Géol. 1976. 7. XVIII. 4.P. 999–1003.
3. Poidevin J.L. Formations Proterozoic superior of the East and the North of the Central African Republic. Towards a global approach to the Upper Precambrian of the Central African Republic.Series of covers of the west and the center of the Central African Republic.Ann. Mus. Roy. Central Afr. Tervuren, Belgium, Geological Sciences. 1985. ser. in-8. 91.
4. Biandja J. Metallogenic approach of Green stone belt of Bogoin (R.C.A). Its mineralisation in Gold.Thesis of Doctor-Engineer, Académie de Paris VI, 1988.318 p.
5. Moloto G.R. Evolution paleoproterozoicgeotectonics with neoproterozoic of the cover of the archaean craton of Congo to the borders of Congo, Cameroun and Central Africa. Doct.thesis, Orléans University, 2002. 264 p.
6. Doyemet A. Le systèmeaquifère de la région de Bangui (RépubliqueCentrafricaine), conséquences des caractéristiquesgéologiques du socle sur la dynamique, les modalités de recharge et la qualité des eauxsouterraines. Thesis (PhD), USTL University of Lille, France, 2006.
7. Alvarez P. Evidence for a Neoproterozoic carbonate ramp on the northern of the central African craton: relations with Late Neoproterozoic intracratonic troughs. Geol. Rundschau. 1995.Vol. 84.P. 636–648.
8. Rolin P. New tectonic data on the Precambrian base in Central Africa: geodynamic implication. Ed. collect. Géocam, PresseUniv, Yaoundé 1.1998.No. 1.P. 249–224.
9. Le Maitre R.W., Streckeisen A., Zanettin B., et al. Igneous Rocks: A Classification and Glossary of Terms, Recommendations of the International Union of Geological Sciences, Subcommission of the Systematics of Igneous Rocks, Cambridge: University Press, 2002. 236 p. DOI
10. Vicat J.P., Pouclet A., Nsifa E. Les Dolérites du Groupe du Ntem (Sud Cameroun) et des RégionsVoisines (Centrafrique, Gabon, Congo, Bas Zaïre): CaractéristiquesGéochimiques et Place dansL’évolution du Craton Centrafricaine), Témtal Part of the Cameroon Volcanic du Congo au Protérozoïque. Géologiee-tEnvironnements au Cameroun, Eds.Vicat J.P. and Bilong P. Collection GEOCAM. 1998.P. 305–324.
11. Ngounouno I., Deruelle B., Guiraud R., Vicat J.-P. Les dykes des bassinscrétacés de Mayo-Oulo-Léréet de Babouri-Figuil (Nord du Cameroun-Sud du Tchad). 12e ConférenceInternationale de la SociétéGéologiqued'Afrique.Yaoundé. Volume: J. Geosci. Soc. Cameroon, 1, n 1A, Special Abstract Issue, GSA 12th Inter. Conf. "Geo-Environmental Catastrophes in Africa". 2001. 90p.
12. Vicat J.P., Ngounouno I., Pouclet A. Existence of old doleritic dykes of continental tholeiite composition, in the Cameroon Line alkaline province. Implication to the geodynamical context.ComptesRendus de l Académie des Sciences - Series IIAEarth and Planetary Science. 2001.Vol. 332.No. 4.P. 243–249. DOI
13. Mpemba-Boni J., Vellutini P-J. Characterisationgeochimique des dykes basiques du Massif de les Saras (MayombeCongolais, Afrique Centrale): consequences geodynamiques. J. Afr. Earth Sci.. 1992.Vol. 14.No. 2.P. 209–215. DOI
14. Zhao S.-Y., Yang A.Y., Langmuir C.H., Zhao T.-P. Oxidized primary arc magmas: Constraints from Cu/Zr systematics in global arc volcanics. Sci. Adv.. 2022.Vol. 8.No. 12. eabk0718. DOI
15. Pearce, J.A., Norry, M.J. Petrogenetic implications of Ti, Zr, Y, and Nb variations in volcanic rocks. Contrib. Mineral. Petrol.. 1979.Vol. 69.P. 33–47. DOI
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17. Condie K.C. High field strength element ratios in Archean basalts: a window to evolving sources of mantle plumes? Lithos.. 2005.Vol. 79.P. 491–504. DOI
Published
2023-03-23
How to Cite
Mapoka, H. F., Biandja, J., Savko, K. A., N’gbatouka, S. M., & Bazikov, N. S. (2023). Dolerite sills in the sandstone of Bangui, Central African Republic: geochemistry and petrology. Proceedings of Voronezh State University. Series: Geology, (1), 65-79. https://doi.org/10.17308/geology/1609-0691/2023/1/65-79
Section
Petrology, Volcanology, Geochemistry
