Research ArticleOpen AccessGoogle Scholar indexed
Petrology of Metaluminous A-Type Rhyolite Discovered from Hadjer el Hamis Volcanoes (Lake Chad Basin)
Institut Universitaire Polytechnique de Mongo, N’Djaména, Chad
Department of Earth Sciences, Faculty of Science, University of Ngaoundere, Yaounde, Cameroon
School of Geology and Mining Engineering, University of Ngaoundere, Meiganga, Cameroon
School of Geology and Mining Engineering, University of Ngaoundere, Meiganga, Cameroon
School of Geology and Mining Engineering, University of Ngaoundere, Meiganga, Cameroon
- 1 Institut Universitaire Polytechnique de Mongo, N’Djaména, Chad
- 2 Department of Earth Sciences, Faculty of Science, University of Ngaoundere, Yaounde, Cameroon
- 3 School of Geology and Mining Engineering, University of Ngaoundere, Meiganga, Cameroon
- 4 School of Geology and Mining Engineering, University of Ngaoundere, Meiganga, Cameroon
- 5 School of Geology and Mining Engineering, University of Ngaoundere, Meiganga, Cameroon
Open Journal of Geology·Volume 08 (2018)·Pages 883–895·Published 3 August 2018·DOI10.4236/ojg.2018.89052
Copy link · social · email
Abstract
Metaluminous (P.I. > 1) rhyolite from Hadjer el Hamis consisted of quartz, alkali feldspar, clinopyroxene (hedenbergite), amphibole (F-arfvedsonite) and oxides-hydroxides (ilmenite, magnetite, limonite) phenocrysts is characterized by the negative Eu, Ba, P, Sr and Ti anomalies. This metaluminous rhyolite and the early discovered peralkaline rhyolites in Hadjer el Hamis volcanoes derive likely from the same source, according to their coexistence on the same sector and their similar Zr/Nb ratios. The causes of magma heterogeneity are likely linked to varying amounts of extraction of an earlier melt phase or tectonic juxtaposition or a sudden increasing of f O 2 in silicic magmas, triggered from a hydrothermal process, associated with F- and alkali-bearing fluids influx, which promoted the enrichment of Na in the hedenbergite rims and the crystallization of arfvedsonite.
KeywordsMetaluminousRhyolitesLake ChadPetrologyHadjer el Hamis
- Eby, G.N. (1992) Chemical Subdivision of the A-Type Granitoids: Petrogenetic and Tectonic Implications. Geology, 20, 641-644. https://doi.org/10.1130/0091-7613(1992)020 2.3.CO;2
- Mbowou, G.I.B., Botelho, N.F., Lagmet, C. and Ngounouno, I. (2015) Petrology of Peraluminous and Peralkaline Rhyolites from the SE Lake Chad (Northernmost Cameroon Line). Journal of African Earth Sciences, 112, 129-141. https://doi.org/10.1016/j.jafrearsci.2015.09.015
- Vicat, J.-P., Pouclet, A., Bellion, Y. and Doumnang, J.-C. (2002) Les rhyolites hyperalcalines (pantellérites) du lac Tchad. Composition et signification tectonomagmatique. Comptes rendus Geoscience, 334, 886-891. https://doi.org/10.1016/S1631-0713(02)01832-1
- Mbowou, G.I.B., Lagmet, C., Nomade, S., Ngounouno, I., Déruelle, B. and Ohnenstetter, D. (2012) Petrology of the Late Cretaceous Peralkaline Rhyolites (Pantellerite, Comendite) from Lake Chad. Journal of Geosciences, 57, 127-141. https://doi.org/10.3190/jgeosci.118
- Moreau, C., Regnoult, J.-M., Déruelle, B. and Robineau, B. (1987) A New Tectonic Model for the Cameroon Line, Central Africa. Tectonophysics, 139, 317-334. https://doi.org/10.1016/0040-1951(87)90206-X
- Hong, W., Xu, X. and Zou, H. (2013) Petrogenesis of Coexisting High-Silica Aluminous and Peralkaline Rhyolites from Yunshan (Yongtai), Southeastern China. Journal of Asian Earth Sciences, 74, 316-329. https://doi.org/10.1016/j.jseaes.2013.01.005
- Le Bas, M.J., Le Maitre, R.W., Streckeisen, A. and Zanettin, B. (1986) A Chemical Classification of Volcanic Rocks Based on the Total Alkali-Silica Diagram. Journal of Petrology, 27, 745-750. https://doi.org/10.1093/petrology/27.3.745
- Leake, B.E., et al. (1997) Nomenclature of Amphiboles: Report of the Subcommitee on Amphiboles of the International Mineralogical Association Commission on New Minerals and Mineral Names. Mineralogical Magazine, 61, 295-321. https://doi.org/10.1180/minmag.1997.061.405.13
- McDonough, W.F. and Sun, S.-S. (1995) The Composition of the Earth. Chemical Geology, 120, 223-253. https://doi.org/10.1016/0009-2541(94)00140-4
- Whalen, J.B., Currie, K.L. and Chappell, B.W. (1987) A-Type Granites: Geochemical Characteristics, Discrimination and Petrogenesis. Contributions to Mineralogy and Petrology, 9, 407-419. https://doi.org/10.1007/BF00402202
- Loiselle, M.C. and Wones, D.R. (1979) Characteristics of Anorogenic Granites. Geological Society of America, Abstracts with Programs, 11, 468.