Mount Etinde is a Recent (<1 Ma) strombolian-type volcano located on the southern flank of Mount Cameroon. Mount Etinde lavas are distinguished on the basis of the mineralogical compositions of their phenocrysts: olivine-pyroxene, olivine-melilite and clinopyroxene-nepheline. Some magnetite and ilmenite occur as inclusions in these early phases. Mafic mineral composition indicates that fractionation involved only limited Fe-enrichment. Oscillatory, normal and sectorial zoning in clinopyroxene relates to the differentiation and fractional crystallization of the magma. Based on the primitive mantle-normalized trace and rare earth element patterns, all nephelinites have high abundances of incompatible elements (103 < La < 281; 131 < Ce < 503), with negative anomalies for high field strength element Ti and low Nb/Y (0.1 - 0.2) and Rb/Y (<0.03) ratios, suggesting derivation from a similar source. Textural characteristics and mineral chemical data, as well as whole-rock compositions, suggest that the nephelinitic lavas may have been derived from basaltic magma from a heterogeneous lithospheric mantle. Geochemical modeling of major and trace element variations indicates that the Etinde lavas could not have been produced by only fractional crystallization. Pneumatolytic reaction probably affected the pyromagmas (basaltic magma composition) and was responsible for the nephelinite rocks at lower oxygen fugacity (fO2).
References
[1]
Déruelle, B., Ngounouno, I. and Demaiffe, D. (2007) The “Cameroon HotLine” (CHL): A Unique Example of Active Alkaline Intraplatestructure in Both Oceanic and Continental Lithospheres. Comptes Rendus Geoscience, 339, 589-600.
https://doi.org/10.1016/j.crte.2007.07.007
[2]
Le Bas, M.J. (1987) Nephelinitite and Carbonatite. In: Fitton, J.G. and Upton, B.G.J., Eds., Alkaline Igneous Rocks, Geological Society, Special Publications, London, 30, 53-83.
https://doi.org/10.1144/GSL.SP.1987.030.01.05
[3]
Blancher, S. (2008) Le coeur alcalin du complexe du Messum, Namibie: Description pétrologique, interprétation de l’évolution minéralogique et relations roches sous-et sur-saturées en silice. Thèse de Doctorat Université Paris VI, Pierre et Marie Curie.
[4]
Déruelle, B., N’ni, J. and Kambou, R. (1987) Mount Cameroon: An Active Volcano of the Cameroon Line. Journal of African Earth Sciences, 6, 197-214.
https://doi.org/10.1016/0899-5362(87)90061-3
[5]
Esch, E. (1901) Der Vulkan Etinde in Kamerun und seine Gesteine (I). Sitzungsberichte. Akad. Wiss. Berlin, 277-299.
[6]
Gèze, B. (1941) Sur les massifs volcaniques du Cameroun OCcidental. C. R. Acad. Sci. Paris, 212, 498-500.
[7]
Tilley, C.E. (1953) The néphelinite of Mont etinde, Cameroon, West Africa. Geological Magazine, 90, 145-151.
[8]
Fitton, G. (1981) Strontian melilite in a nephelinite lava from Etinde, Cameroon.
[9]
Mouafo, L. (1988) Contribution à l’étude géologique du Mont Etindé: Par exemple d’une série hyperalcaline fortement sous saturé. Thèse Doct 3 ème cycle, Université de Yaoundé, Yaounde, 157.
[10]
Mouafo, L., Nkoumbou, C. and Tchoua, F. (1992) Données géomorphologiques et pétrologie sur le Mont Etindé, Géographie au Cameroun XI, 2, 90-100.
[11]
Nkoumbou, C. (1990) Etude géochronologique des monts Rumpi: Un ensemble plutonique et volcanique de la “Ligne du Cameroun”. 2. Données pétrologiques sur les néphénilites du Mont Etindé (Cameroun). Thèse Doct Université de Nancy I, 356.
[12]
Nkoumbou, C., Déruelle, B. and Velde, D. (1995) Petrology of Mount Etinde Nephelinite Series. Journal of Petrology, 36, 373-395. https://doi.org/10.1093/petrology/36.2.373
[13]
Roffet, L. (2003) Géochimie du volcanisme du Mont Cameroun et du Mont Etindé. DEA, Université Joseph-Fourier, Grenoble, France.
[14]
Etame, J., Gerard, M., Bilong, P. and Suh, C.E. (2009) Halloysite Neoformation during the Weathering of Nephelinitic Rocks under Humid Tropical Conditions at Mt Etinde, Cameroon. Geaderma, 154, 59-68.
[15]
Etame, J., Suh, C.E., Gerard, M. and Bilong, P. (2012) Phillipsite Formation in Nephelinitic Rocks in Response to Hydrothermal Alteration at Mount Etinde, Cameroon. Chemie der Erde-Geochemistry, 72, 31-37.
[16]
Tsafack, J.M., Wandji, J.P.F., Bardintzeff, D.G. and Nkouathio, A. (2007) Occurrence of a Sedimentary Basement under the Mount Cameroon Active Volcano (Cameroon Volcanic Line). 26th (ECGS: European center for Geodynamics and Seismology) Workshop, Active Volcanism and Continental Rifting (Accor-07), Luxembourg, 19-21 November 2007.
[17]
Ngounouno, I. (2013) La pétrologie éruptive Moderne (Le Cameroun, l’Islande, les Andes). T2 Harmattan, 410 p.
[18]
Pouchou, J.L. and Pichoir, F. (1991) Quantitative Analysis of Homogeneous or Stratified Microvolumes Applying the Model “PAP”. In: Heinrich, K.F.J. and Newbury, D.E., Eds., Electron Probe Quantification, Plenum Press, New York, 31-75.
https://doi.org/10.1007/978-1-4899-2617-3_4
[19]
Andersen, D.J., Lindsley, D. and Davidson, P.M. (1993) QUILF: A PASCAL Program to Assess Equilibria among Fe-Mg-Mn-Ti Oxides, Pyroxenes, Olivine, and Quartz. Computers & Geosciences, 19, 1333-1350. https://doi.org/10.1016/0098-3004(93)90033-2
[20]
White, J.C, Ren, M. and Parker, D.F. (2005) Variation in Mineralogy, Temperature, and Oxygen Fugacity in a Suite of Strongly Peralkaline Lavas and Tuffs, Pantelleria, Italy. The Canadian Mineralogist, 43, 1331-1347. https://doi.org/10.2113/gscanmin.43.4.1331
[21]
Ren, M., Onenda, P.A., Anthony, E.Y., White, J.C., Macdonald, R. and Bailey, D.K. (2006) Application of the QUILF Thermobarometer to the Peralkaline Trachytes and Pantellerites of the Eburu Volcanic Complex, East African Rift, Kenya. Lithos, 91, 109-124.
https://doi.org/10.1016/j.lithos.2006.03.011
[22]
Mbowou, I., Nguihdama, D., Yamgouot, F., Ntoumbe, M. and Ngounouno, I. (2013) Ti-Bearing Aenigmatite from Djinga Tadorgal (Adamawa Plateau) and Sao Tomé (Cameroon Line) Phonolites: Geochemical Implications and Application of the QUILF Thermobarometer for the Crystallization Conditions. International Journal of Biology and Chemical Sciences, 7, 2601-2610.
[23]
Fitton, J.G. and Dunlop, H.M. (1985) The Cameroon Line, West Africa, and Its Bearing on the Origin of Oceanic and Continental Alkali Basalt. Earth and Planetary Science Letters, 72, 23-38. https://doi.org/10.1016/0012-821X(85)90114-1
[24]
Morimoto, N., Fabries, J., Ferguson, A.K., Ginzburg, I.V., Ross, M., Seifert, F.A. and Zussman, J. (1988) Nomenclature of Pyroxenes. American Mineralogist, 73, 1123-1133.
[25]
Dawson, J.B., Smith, J.V. and Jones, A.P. (1985) A Comparative Study of Bulk Rock and Mineral Chemistry of Olivine Melilitites and Associated Rocks from East and South Africa. Neues Jahrbuchfür Mineralogie, Abhandlungen, 152, 143-175.
[26]
Coleman, R.G. (1965) Eclogites and Eclogites: Their Differences and Similarities. Geological Society of America Bulletin, 76, 483-508.
https://doi.org/10.1130/0016-7606(1965)76[483:EAETDA]2.0.CO;2
[27]
Hoffer (2008) Fusion partielle d’un manteau métasomatisé par un liquide adakitique: Approches géochimique et expérimentale de la genèse et de l’évolution des magmas de l’arrière arc équatorien. Thèse de l’Université Blaise Pascal, 334 p.
[28]
Deer, W.A. and Abbot, D. (1965) Clinopyroxène of the Gabbro Cumulates of the Edvard Holm Complex, East Greenland. Mineralogical Magazine, 34, 177-193.
https://doi.org/10.1180/minmag.1965.034.268.14
[29]
De Vries, R.C., Roy, R. and Osborn, E.F. (1955) Phase Equilibria in the Systeme CaO-TiO2-SiO2. Journal of the American Ceramic Society, 38, 158-171.
https://doi.org/10.1111/j.1151-2916.1955.tb14922.x
[30]
Stormer J.C. (1973) Calcium Zoning in Olivine and Its Relationship to Silica Activity and Pressure. Geochimica et Cosmochimica Acta, 37, 1815-1821.
https://doi.org/10.1016/0016-7037(73)90144-0
[31]
Maurel, C. and Maurel, P. (1982) Etude expérimentale de la distribution de l’aluminium entre bain silicaté basique et spinelle chromifère. Implications pétrogénétiques: Teneur en chrome des spinelles. Bulletin Minéralogie, 105, 197-202.
[32]
Sack, R.O. and Ghiorso, M.S. (1991) Chromian Spinels as Petrogenetic Indicators: Thermodynamics and Petrological Applications. American Mineralogist, 76, 827-847.
[33]
Shannon, R., Iishi, K., Allik, T., Rossman, G.R. and Liebertz, J. (1992) Dielectric Constants of BaO and Melilites and Oxide Additivity Rule. European Journal of Mineralogy, 4, 1239-1249.
[34]
Donaldson, C.H., Dawson, J.N., Kanaris-Sotiriou, R., Batchelor, R.A. and Walsh, J.N. (1987) The Silicate Lavas of Oldoinyo Lengai, Tanzania. Neues Jahrbuch für Mineralogie Abhandlungen, 156, 247-279.
[35]
Lustrino, M. and Wilson, M. (2007) The Circum-Mediterrane an Anorogenic Cenozoic Igneous Province. Earth-Science Review, 81, 1-65.
[36]
Yamgouot, F.N., Déruelle, B., Mbowou, G.I.B. and Ngounouno, I. (2015) Petrology of the Volcanic Rocks from Bioko Island (“Cameroon Hot Line”). International Journal of Geosciences, 6, 247-255. https://doi.org/10.4236/ijg.2015.63019
[37]
Ngounouno, I., Déruelle, B., Montigny, R. and Demaiffe, D. (2006) Les camptonites du Mont Cameroun, Cameroun, Afrique. Comptes Rendus Géoscience, 338, 537-544.
https://doi.org/10.1016/j.crte.2006.03.015
[38]
Nguihdama, D., Chazot, G., Pierre, K., Bertrand, M.G.I., Ismaila, N. (2014) Spinel-Bearing Lherzolite Xenoliths from Hosséré Garba (Likok, Adamawa-Cameroon): Mineral Compositions and Geothermobarometric Implications. International Journal of Geosciences, 5, 1435-1444.
[39]
Wandji, J.P.F., Tsafack, J.M., Bardintzeff, D.G., Nkouathio, A., Kagou, D.H., Bellon, H. and Guillou, H. (2009) Xenoliths of Dunite, Wehrlites and Clinopyroxenites in the Basanite from Batoke Volcanic Cone (Mount Cameroon, Central Africa) Petrogenetic Implication. Mineralogy and Petrology, 96, 81-98. https://doi.org/10.1007/s00710-008-0040-3
[40]
Harris, P.G. (1972) Geothermal Environment and Basalt Magma Type. Journal of Earth Science, 8, 275-281.
[41]
Rittmann, A. (1963) Les volcans et leur activité. Edition MASSON et CIE, 461 p.
[42]
Sun, S. and McDonough, W.F. (1989) Chemical and Isotopic Systematics of Oceanics Basalts: Implications for Mantle Composition and Processes. Geological Society, London, Special Publications, 42, 313-345.
[43]
Chazot, G., Menzies, M.A. and Harte, B. (1996) Determination of Partition Coefficients between Apatite, Clinopyroxene, Amphibole and Melt in Natural Spinel Lherzolites from Yemen: Implications of Wet Meltingin the Lithospheric Mantle. Geochimica et Cosmochimica Acta, 60, 423-427. https://doi.org/10.1016/0016-7037(95)00412-2
[44]
Hamilton, D.L. (1961) Nepheline as Crystallization Temperature Indicators. The Journal of Geology, 69, 321-329.
[45]
Edgar, A.D. (1987) The Genesis of Alkaline Magmas with Emphasis on Their Source Regions: Inferences from Experimental Studies. Geological Society, London, Special Publications, 30, 29-52. https://doi.org/10.1144/gsl.sp.1987.030.01.04
[46]
Simonetti, A., Goldstein, S.L., Schmidberger, S.S. and Viladkar, S.G. (1998) Geochemical and Nd, Pb, and Sr Isotope Data from Deccan Alkaline Complexes—Inferences for Mantle Sources and Plume-Lithosphere Interaction. Journal of Petrology, 39, 1847-1864.
https://doi.org/10.1093/petroj/39.11-12.1847
