Petrology of the Volcanic Rocks from Bioko Island (“Cameroon Hot Line”)


Bioko island (3008 m a.s.l.), is composed of the alkaline basaltic lavas (basalts and hawaiites) with xenoliths. These lavas have a microlitic textureand consisted of euhedral to subhedral phenocrysts (>1 mm) of olivine (0.83 < Mg# < 0.87) and diopside ± Ti-augite. Plagioclase (An62-67Ab35-32Or3-1) phenocrysts are present only in hawaiites. In Harker diagrams, SiO2, Al2O3, Na2O and K2O contents of the lavas increase and Fe2O3, MgO and CaO decrease with increasing differentiation from basalts to hawaiites. The compatible elements Ni, Cr and V decrease strongly in basalts and remain at low levels in hawaiites. Basaltic lavas from Bioko lavas have low Hf contents (4.2 - 9.2 ppm) and consequently higher Hf/Zr ratios (50 - 90) than those (<50) of similar lavas from other volcanoes of the Cameroon Hot Line. Such high ratios are commonly observed in alkaline basaltic lavas associated with carbonatitic and/or nephelinitic magmatism. The Sr and Nd isotopic compositions point to a slightly depleted mantle source.

Share and Cite:

Yamgouot, F. , Déruelle, B. , Mbowou, I. and Ngounouno, I. (2015) Petrology of the Volcanic Rocks from Bioko Island (“Cameroon Hot Line”). International Journal of Geosciences, 6, 247-255. doi: 10.4236/ijg.2015.63019.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Aka, F.T., Nagao, K., Kusakabe, M., Sumino, H., Tanyileke, G., Ateba, B. and Hell, J. (2004) Symmetrical Helium Isotope Distribution on the Cameroon Volcanic Line, West Africa. Chemical Geology, 203, 205-223.
[2] Chauvel, C., Dia, A.N. Bulourde, M., Chabaux, F., Durand, S., Ildefonse, P., Gérard, M., Déruelle, B. and Ngounouno, I. (2005) Do Decades of Tropical Rainfall Affect the Chemical Compositions of Basaltic Lava Flows in Mt Cameroon? Journal of Volcanology and Geothermal Research, 141, 195-223.
[3] Hedberg, J.D. (1969) A geological Analysis of the Cameroon Trend. Ph.D. Thesis, Princeton University, Princeton, 188 p.
[4] Piper, J.D.A. and Richardson, A. (1972) The Palaeomagnetism of the Gulf of Guinea Volcanic Province, West Africa. Geophysical Journal of Royal Astronomical Society, 29, 147-171.
[5] Enciclopedia Universal Ilustrada 1924. Fernando Poo, Espasa-Calpe SA Hijos de J. Espasa, Madrid 23, 833.
[6] Boese, W. (1912) Petrographische Untersuchungen an jungvulkanischen Ergussgesteinen von Sao Thomé und Fernando Poo. Neues Jahrbrbuch für Geologie und Palaontologie Abhandlungen, 34, 253-320.
[7] Thornton, C.P. and Tuttle, O.F. (1960) Chemistry of Igneous Rocks—[Part] 1 I. Differentiation Index. American Journal of Science, 258, 664-684.
[8] Ridley, W.I. and Baker, I. (1973) The Petrochemistry of a Unique Cordierite-Bearing Lava from St. Helena Island, South Atlantic. American Mineralogist, 58, 813-818.
[9] Higgins, M.D. (2006) Verification of Ideal Semi-Logarithmic, Lognormal or Fractal Crystal Size Distributions from 2D Datasets. Journal of Volcanology and Geothermal Research, 154, 8-16.
[10] Marsh, B.D. (1988) Crystal Size Distribution (CSD) in Rocks and the Kinetics and Dynamics of Crystallization. 1. Theory. Contribributions to Mineralogy and Petroogy, 99, 277-291.
[11] Higgins, M.D. (1996) Magma Dynamics beneath Kameni Volcano, Thera, Greece, as Revealed by Crystal Size and Shape Measurements. Journal of Volcanology and Geothermal Research, 70, 37-48.
[12] Marsh, B.D. (1998) On the Interpretation of Crystal Size Distribution in Magmatic Systems. Journal of Petrology, 39, 553-599.
[13] Nimis, P. and Ulmer, P. (1998) Clinopyroxene Geobarometry of Magmatic Rocks Part 1: An Expanded Structural Geobarometer for Anhydrous and Hydrous, Basic and Ultrabasic Systems. Contributions to Mineralogy and Petrology, 133, 122-135.
[14] Woodland, A.B. and Jugo, P.J. (2007) A Complex Magmatic System beneath the Devès Volcanic Field, Massif Central, France: Evidence from Clinopyroxene Megacrysts. Contributions to Mineralogy and Petrology, 153, 719-731.
[15] Berger, J., Ennih, N., Liégeois, J.P., Nkono, C., Mercier, J.C.C. and Demaiffe, D. (2008) A Complex Multi-Chamber Magmatic System beneath a Late Cenozoic Volcanic Field: Evidence from CSDs and Thermobarometry of Clinopyroxene from a Single Nephelinite Flow (Djbel Saghro, Morocco). Geological Society, London, Special Publications, 297, 509-524.
[16] Déruelle, B., Ngounouno, I. and Demaiffe, D. (2007) The “Cameroon Hot Line” (CHL): A Unique Example of Active Alkaline Intraplate Structure in Both Oceanic and Continental Lithospheres. Comptes Rendus Geoscience, 339, 589-600.
[17] Lee, D.C., Halliday, A.N., Davies, G.R., Essene, E.J., Fitton, J.G. and Temdjim, R. (1996) Melt Enrichment of Shallow Depleted Mantle: A Detailed Petrological, Trace Element and Isotopic Study of Mantle-Derived Xenoliths and Megacrysts from the Cameroon Line. Journal of Petrology, 37, 415-441.
[18] Déruelle, B., Bardintzeff, J.M., Cheminée, J.L., Ngounouno, I., Lissom, J., Nkoumbou, C., Etamé, J., Hell, J.V., Tanyileke, G., N’ni, J., Ateba, B., Ntepe, N., Nono, A., Wandji, P., Fosso, J. and Nkouathio, D.G. (2000) éruptions simultanées de basalte alcalin et de hawaiite au mont Cameroun (28 mars-17 avril 1999). Comptes Rendus de l’Académie des Sciences Paris, 331, 525-531.
[19] Nkoumbou, C., Déruelle, B. and Velde, D. (1995) Petrology of Mt Etinde Nephelinite Series. Journal of Petrology, 36, 373-395.
[20] Halliday, A.N., Davidson, J.P., Holden, P., DeWolf, C., Lee, D.C. and Fitton, J.G. (1990) Trace-Element Fractionation in Plumes and the Origin of HIMU Mantle beneath the Cameroon Line. Nature, 347, 523-528.
[21] Ngounouno, I. and Déruelle, B. (2007) Pétrologie des xénolithes de wehrlites et clinopyroxénites du Mont Cameroun: Evidence d’un métasomatisme mantellique. Journal of Cameroon Academics Science, 7, 35-56.
[22] Hofmann, A.W. (1988) Chemical Differentiation of the Earth: The Relationship between Mantle, Continental Crust, Oceanic Crust. Earth and Planetary Science Letters, 90, 297-314.

Copyright © 2022 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.