Petrology and geochemistry of ignimbrites and associated enclaves from Mount Bambouto, West-Cameroon, Cameroon Volcanic Line
Por:
Gountié Dedzo M., Diddi Hamadjoda D., Fozing E.M., Chako Tchamabé B., Mendoza-Rosas A.T., Asaah A.N.E., Zangmo Tefogoum G., Kamgang P., Ohba T.
Ahead of Print:
1 ene 2020
Resumen:
Geochemical and mineralogical analyses data are presented for ignimbritic deposits from the Bambouto volcano. These deposits are characterized by their welded and non-welded massive lapilli tuff and massive lithic breccias facies. The ignimbrites generally display vitroclastic and/or eutaxitic texture characterized by whole or broken minerals, subangular fragments of trachytes, rhyolites, ignimbrites, as well as fiammes, and fragments of glass. The geochemistry of the ignimbrites of Mount Bambouto indicates that they are alkaline and peralkaline with rhyolitic and trachytic composition. The behaviour of the major and trace elements suggest that ignimbrites, as well as felsic and mafic lavas of the Bambouto volcano have an evolution dominated by fractional crystallization (FC). The La/Yb, Ce/Zr and Th/Nb ratios for Mt Bambouto ignimbrites (19.92–52.66; 0–0.48; 0.10–0.12, respectively) and the whole Western Cameroon Highlands (WCH) and Mt Manengouba lavas (15.58–34.29; 0–0.61; 0–0.27, respectively) also reflect the dominant role of FC. This suggests a relatively constant degree of partial melting during the petrogenesis of the lavas and deposits. The high Rb/Sr (0.52–28.98) and the low ratios of LILE/HFSE (Rb/Nb: 0.08–0.95; Rb/Zr: 0.01–0.18; Th/Ta: 1.38–2.1; Ba/Nb: 0.06–8.27) in Mt. Bambouto ignimbrites, compared with the very high value of these ratios in the granitic basement rocks of the area, preclude the petrogenesis of the ignimbrites from the melting of the Pan-African basement. The weak values of Th/La and La/Nb in the studied ignimbrites and other WCH lavas suggest that crustal contamination was insignificant during ascent and storage of the magma in shallow magma chambers prior to their release to the surface. The similarities in Nb/Ta, Zr/Hf and Nb/U ratios in the Mt Bambouto ignimbrites (Nb/Ta: 13.54–20.93; Zr/Hf: 37.39–49.95; Nb/U: 26.04–55.70) and the lavas of the WCH (Nb/Ta: 11.3–19.57; Zr/Hf: 33.16–55.01; Nb/U: 19.83–75.35) corroborated with their similar source origin. The enrichment of light REE relative to heavy REE or their Dy/Yb > 2 (2.03–2.97), (La/Yb)N > 5 (14.29–46.69) and (Tb/Yb)N > 1.9 (1.91–2.9) suggest melting in a garnet-bearing mantle. © 2020 Elsevier GmbH
Filiaciones:
Gountié Dedzo M.:
Department of Life and Earth Sciences, High Teachers’ Training College, University of Maroua, P.O. Box. 55, Maroua, Cameroon
Diddi Hamadjoda D.:
Department of Life and Earth Sciences, High Teachers’ Training College, University of Maroua, P.O. Box. 55, Maroua, Cameroon
Fozing E.M.:
Laboratory of Environmental Geology, University of Dschang, P.O. Box 67, Dschang, Cameroon
Chako Tchamabé B.:
CONACYT-Centro de Ingeniería y Desarrollo Industrial, Av. Playa Pie de la Cuesta 702, Desarrollo San Pablo, Querétaro, Qro 76125, Mexico
Mendoza-Rosas A.T.:
CONACYT-Centro de Ingeniería y Desarrollo Industrial, Av. Playa Pie de la Cuesta 702, Desarrollo San Pablo, Querétaro, Qro 76125, Mexico
Asaah A.N.E.:
Department of Mines, Ministry of Mines, Industry and Technological Development, P.O. Box 70, Yaoundé, Cameroon
Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-Ku, Tokyo, 152-8551, Japan
Zangmo Tefogoum G.:
Department of Earth Sciences, Faculty of Sciences, University of Maroua, P.O. Box 814, Maroua, Cameroon
Kamgang P.:
Department of Earth Sciences, University of Yaoundé I, B.P. 812, Yaoundé, Cameroon
Ohba T.:
Department of Chemistry, School of Science, Tokai University, Hiratsuka, 259-1211, Japan
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