Petrology of Spinel-Lherzolite Xenoliths from Mazélé and Others Northen Xenoliths Localities of Cameroon Volcanic Line: Exchange Reactions and Equilibrium State
The alkaline volcanism of the Cameroon Volcanic Line in its northern domain has raised many fresh enclaves of peridotites. The samples selected come from five (05) different localities (Liri, in the plateau of Kapsiki, Mazélé in the NE of Ngaoundéré, Tello and Ganguiré in the SE of Ngaoundéré and Likok, locality located in the west of Ngaoundé). The peridotite enclaves of the above localities show restricted mineralogical variation. Most are four-phase spinel-lherzolites, indicating that this is the main lithology that forms the lithospheric mantle below the shallow zone. No traces of garnet or primary plagioclase were detected, which strongly limits the depth range from which the rock fragments were sampled. The textures and the wide equilibrium temperatures (884˚C - 1115˚C) indicate also entrainment of lherzolite xenoliths from shallow depths within the lithosphere and the presence of mantle diapirism. The exchange reactions and equilibrium state established in this work make it possible to characterize the chemical composition of the upper mantle of each region and test the equilibrium state of the phases between them. Variations of major oxides and incompatible elemental concentrations in clinopyroxene indicate a primary control by partial melting. The absence of typical “metasomatic” minerals, low equilibration temperatures and enriched LREE patterns indicate that the upper mantle below septentrional crust of Cameroun underwent an event of cryptic metasomatic enrichment prior to partial melting. The distinctive chemical features, LREE enrichment, strong U, Ce and Pr, depletion relative to Ba, Nb, La, Pb, and T, fractionation of Zr and Hf and therefore ligh high Zr/Hf ratio, low La/Yb, Nb/La and Ti/Eu are all results of interaction of refractory peridotite residues with carbonatite melts.
References
[1]
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. Géoscience, 339, 589-600. https://doi.org/10.1016/j.crte.2007.07.007
[2]
Kamgang, P. (2003) Pétrologie et géochimie d’un secteur clé de la Ligne du Cameroun, les monts Bamenda: Implications sur la genèse et l’évolution des magmas. Thèse Doct., University of Yaoundé I, Yaoundé, 373 p.
[3]
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
[4]
Louis, P. (1970) Contribution géophysique à la connaissance géologique du bassin du lac Tchad. Mémoires OSTROM, n˚42, 311 p. et cartes en annexes.
[5]
Browne, S.E. and Fairhead, J.D. (1983) Gravity Study of the Central African Rift System: A Model of Continental Disruption. Part 1: The Ngaoundéré and Abu Gabra Rifts. In: Morgan, P. and Baker, B.H., Eds., Developments in Geotectonics, Elsevier, Amsterdam, 187-203. https://doi.org/10.1016/B978-0-444-42198-2.50018-3
[6]
Girod, M., Dautria, J.M. and Balle, S.D. (1984) Estimation de la profondeur du manteau du Moho sous le massif volcanique de l’Adamaoua (Cameroun) à partir de l’étude d’enclaves de lherzolite. Comptes rendus de l’Académie des Sciences Paris 2, 298, 699-704.
[7]
Stuart, G.W., Fairhead, J.D., Dorbath, L. and Dorbath, C. (1985) A Seismic Refraction Study of the Crustal Structure Associated with the Adamawa Plateau and Garoua Rift Cameroon, West Africa. Geophysical Journal International, 81, 1-12. https://doi.org/10.1111/j.1365-246X.1985.tb01346.x
[8]
Dautria, J.M. and Girod, M. (1986) Les enclaves de lherzolite à spinelle et plagioclase du volcan de Dibi (Adamaoua, Cameroun): Des témoins du manteau anormal. Bulletin de Minéralogie, 109, 275-286. https://doi.org/10.3406/bulmi.1986.7934
[9]
Poudjom Djomani, Y.P., Diament, M. and Albouy, Y. (1992) Mechanical Behaviour of the Lithosphere beneath the ADAMAWA Uplift (Cameroon, West Africa) Based on Gravity Data. Journal of African Earth Sciences, 15, 81-90. https://doi.org/10.1016/0899-5362(92)90009-2
[10]
Dorbath, C., Dorbath, L., Fairhead, J.D. and Stuart, G.W. (1986) A Teleseismic Delay Time Study across the Central African Shear Zone in the Adamawa Region of Cameroon, West Africa. Geophysical Journal International,86, 751-766. https://doi.org/10.1111/j.1365-246X.1986.tb00658.x
[11]
Thomas, P. (2004) Crustal Thinning and Associated Tectonic Subsidence during Continental Rifting. Geophysical Journal International, 158, 529-553.
[12]
Karmalkar, N.R., et al. (2002) Cryptic Metasomatism in the Upper Mantle beneath Kutch: Evidence from Spinel Lherzolite Xenoliths. Current Science, 82, 1157-1165.
[13]
Ngounouno, I., Déruelle, B. and Demaiffe, D. (2000) Petrology of the Bimodal Cenozoic Volcanism of the Kapsiki Plateau (Northern Most Cameroun, Central Africa). Journal of Volcanology and Geothermal Research, 102, 21-44. https://doi.org/10.1016/S0377-0273(00)00180-3
[14]
Tamen, J. (1998) Contribution à l’étude géologique du plateau Kapsiki (Extrême-Nord, Cameroun): Volcanologie, Pétrologie et Géochimie. Thèse Doct. 3ème cycle, Université de Yaoundé 1, Yaoundé, 127 p.
[15]
Ngounouno, I. (1993) Pétrologie du magmatisme cénozoïque de la vallée de la Bénoué et du plateau Kapsiki (nord du Cameroun). Thèse Doct., Université Pierre et Marie Curie, Paris, 1-280.
[16]
Dunlop, H.M. (1983) Strontium Isotope Geochemestry and Potassium-Argon Studies on Volcanic Rocks from the Cameroon Line, West Africa. PhD thesis, The University of Edinburgh, Edinburgh, 347.
[17]
Vincent, P.M. and Armstrong, R.L. (1973) Volcanism of the Kapsiki Plateau (North Cameroon) and the Underlying Sedimentary Formations. Coll. African Geol., Florence.
[18]
Okereke, C.S. (1988) Contrasting Modes of Rifting: The Benue Trough and the Cameroon Volcanic Line, West Africa. Tectonophysics, 7, 775-784. https://doi.org/10.1029/TC007i004p00775
[19]
Guiraud, R. and Maurin, J.C. (1992) Early Creataceous Rifts of Western and Central Africa: An Overview. Tectonophysics, 213, 153-168. https://doi.org/10.1016/B978-0-444-89912-5.50035-1
[20]
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
[21]
Droop, G.T.R. (1987) A General Equation for Estimating Fe3 Concentrations in Ferromagnesian Silicates and Oxides from Microprobre Analyses, Using Stoichiometric Criteria. Mineralogical Magazine, 51, 431-435. https://doi.org/10.1180/minmag.1987.051.361.10
[22]
Stormer, C.Fr. (1983) The Effects of Recalculation on Estimates of Temperature and Oxygen Fugacity from Analyses of Multicomponent Iron-Titanium Oxides. American Mineralogist, 68, 586-594.
[23]
Caldeira, R. and Munha, J.M. (2002) Petrology of Ultramafic Nodules from Sao Tomé Island, Cameroon Volcanic Line (Oceanic Sector). Journal of African Earth Sciences, 34, 231-246. https://doi.org/10.1016/S0899-5362(02)00022-2
[24]
Déruelle, B., Moreau, C., Nkoumbou Kambou, R., Lissom, J., Njonfang, E., Ghogomu, R.T. and Nono, A. (1991) The Cameroon Line: A Review. In: Kampuru, A.B. and Lubala, R.T., Eds., Magmatism in Extensional Structural Settings. The Phanerozoic African Plate, Springer-Verlag, Berlin, 273-327. https://doi.org/10.1007/978-3-642-73966-8_12
[25]
Lee, D.C., Halliday, A.N., Davies, G.R., Essene, E.J., Fitton, G.J. 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. https://doi.org/10.1093/petrology/37.2.415
[26]
Nana, R., Nkoumbou, C., Tchouankoué, J.P., Tabod, F. and Tchoua, F. (1998) Pétrologie des nodules de péridotites de Nyos (Cameroun): Implications sur l’évaluation des risques volcaniques. In: Vicat, J.-P. and Bilong, P., Eds., Géosciences au Cameroun, Press. Univ., Yaoundé I, Yaoundé, 225-228.
[27]
Princivalle, F., Tirone, M. and Comin-Chiaramonti, P. (2000) Clinopyroxenes from Metasomatized Spinel-Peridotite Mantle Xenoliths from Nemby (Paraguay): Crystal Chemistry and Petrological Implications. Mineralogy and Petrology, 70, 25-35. https://doi.org/10.1007/s007100070011
[28]
Nkouandou, O.F. and Temdjim, R. (2011) Petrology of Spinel Lherzolite Xenoliths and Host Basaltic Lava from Ngao Voglar Volcano, Adamawa Massif (Cameroon Volcanic Line, West Africa): Equilibrium Conditions and Mantle Characteristics. Journal of Geosciences, 56, 375-387. https://doi.org/10.3190/jgeosci.108
[29]
Morimoto, N., Fabries, J., Ferguson, A.K., Ginzburg, I.V., Ross, M., Seifert, F.A., Zussman, J., Aoki, K. and Gottardi, G. (1988) Nomenclature of Pyroxenes. American Mineralogist, 73, 1123-1133.
[30]
Simkim, T. and Smith, J.V. (1970) Minor Element Distribution in Olivine. The Journal of Geology, 78, 207-219. https://doi.org/10.1086/627519
[31]
Roeder, P.L. and Emslie, R.F. (1970) Olivine-Liquid Equilibrium. Contributions to Mineralogy and Petrology, 29, 275-508. https://doi.org/10.1007/BF00371276
[32]
Vaselli, O., Downes, H., Thirwall, M., Dobosi, G., Coradossi, N., Seghedi, I., Szakacs, A. and Vannucci, R. (1995) Ultramafic Xenoliths in Plio-Pleistocene Alkali Basalts from the Eastern Transylvanian Basin: Depleted Mantle Enriched by Vein Metassomatism. Journal of Petrology, 36, 23-53. https://doi.org/10.1093/petrology/36.1.23
[33]
Sun, S.S. and McDonough, W.F. (1989) Chemical and Isotopic Systematics of Oceanic Basalts: Implications for Mantle Composition and Processes. In: Saunders, A.D. and Norry, M.J., Eds., Magmatism in the Ocean Basins, Vol. 42, The Geological Society, London, 313-345. https://doi.org/10.1144/GSL.SP.1989.042.01.19
[34]
Ngounouno, I. and Déruelle, B. (2007) Pétrologie des xénolites de wehrlites et clinopyroxénites du mont Cameroun: Évidence d’un métasomatisme mantellique. Journal of the Cameroon Academy of Sciences, 7, 35-46.
[35]
Matsui, Y. and Nishizawa, O. (1974) Iron (II)-Magnesium Exchange Equilibrium between Olivine and Calcium-Free over a Temperature Range 800 ˚C to 1300 ˚C. Bulletin de Minéralogie, 97, 122-130. https://doi.org/10.3406/bulmi.1974.6868
[36]
Ganguly, J. and Ghose S. (1979) Aluminous Orthopyroxene: Order-Disorder, Thermodynamic Properties and Petrologic Implications. Contributions to Mineralogy and Petrology, 69, 375-385. https://doi.org/10.1007/BF00372263
[37]
Ben Jamma, N. (1988) Les péridotites de Bay of Islands (Terre Neuve) et de Cap Ortegal (Espagne): Approche petro-structurale. Thèse de Doctorat, I.P.G.P. & Univ. Paris 7, Paris, 245 p.
[38]
Bertrand, P., Sotin, C., Gaulier, J.M. and Mercier, J.C.C. (1987) La solubilité de l’aluminium dans l’orthopyroxène. Inversion globale des données expérimentales de MgO-Al2O3-SiO2. Bulletin de la Société Géologique de France, 3, 821-832. https://doi.org/10.2113/gssgfbull.III.5.821
[39]
Mercier, J.C. (1980) Magnitude of Continental Lithospheric Stresses Inferred from Rheomorphic Petrology. Journal of Geophysical Research, 85, 6293-6303. https://doi.org/10.1029/JB085iB11p06293
[40]
Webb, S.A. and Wood, B.J. (1986) Spinel-Pyroxene-Garnet Relationships and Their Dependance on Cr/Al Ratio. Contributions to Mineralogy and Petrology, 92, 471-480. https://doi.org/10.1007/BF00374429
[41]
Cabanes, N. and Mercier, J.C.C. (1988) Insight into the Upper Mantle beneath an Active Extensional Zone: The Spinel-Peridotite Xenoliths from San Quintin (Baja California, Mexico). Contributions to Mineralogy and Petrology,100, 374-382. https://doi.org/10.1007/BF00379746
[42]
Benoit, V. (1987) Etat d’équilibre de péridotites du manteau supérieur: Application du plateau du Colorado. Ph.D. Thesis, Université Paris 7, Institut Physique du Globe de Paris, Paris.
[43]
Fabriès, J. (1979) Spinel-Olivine Geothermometry in Peridotite from Ultramafic Complexes. Contributions to Mineralogy and Petrology, 69, 329-336. https://doi.org/10.1007/BF00372258
[44]
Green, D.H. and Hibberson, W. (1970) The Instability of Plagioclase in Peridotite at High Pressure. Lithos,3, 209-221. https://doi.org/10.1016/0024-4937(70)90074-5
[45]
Adams, G.E. and Bishop, F.C. (1986) The Olvine-Clinopyroxene Geobarometer: Experimental Results in the CaO-FeO-MgO-SiO2 System. Contributions to Mineralogy and Petrology, 94, 230-237. https://doi.org/10.1007/BF00592939
[46]
Nimis (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. https://doi.org/10.1007/s004100050442
[47]
Carswell, D.A., Griffin, W.L. and Kresten, P. (1984) Peridotite Nodules from the Ngopetsoen and Lipelaneng Kimberlites, Lesotho: A Crustal or Mantle Origin. In: Kornprobst, J., Ed., Kimberlites II: The Mantle and Crust-Mantle Relationships, Elsevier, Amsterdam, 229-243. https://doi.org/10.1016/B978-0-444-42274-3.50025-1
[48]
Fabriès, J., Lorand, J.-P., Bodinier, J.-L. and Dupuy, C. (1991) Evolution of the Upper Mantle beneath the Pyrenees: Evidence from Orogenic Spinel Lherzolite Massifs. Journal of Petrology, No. 2, 55-76. https://doi.org/10.1093/petrology/Special_Volume.2.55
[49]
Nicolas, A., Lucazeau, F. and Bayer, R. (1987) Peridotite Xenoliths in Massif Central Basalts, France: Texture and Geophysical Evidence for Asthenospheric Diapirism. In: Nixon, P.H., Ed., Mantle Xenoliths, John Wiley and Sons, Chichester, 563-574.
[50]
Bodinier, J.-L., Menzies, M.-A. and Thirlwall, M.-F. (1991) Continental to Oceanic Mantle Transition-REE and Sr-Nd Isotopic Geochemistry of the Lanzo Lherzolite Massif. Journal of Petrology, No. 2, 191-210. https://doi.org/10.1093/petrology/Special_Volume.2.191
[51]
Frey, F.A., Suen, J. and Stockman, H.W. (1985) The Ronda High Temperature Peridotite Geochemistry and Petrogenesis. Geochimica et Cosmochimica Acta, 49, 2469-2491. https://doi.org/10.1016/0016-7037(85)90247-9
[52]
Bussod, G.-Y. and Christie, J.-M. (1991) Textural Development and Melt Topology in Spinel Lherzolite Experimentally Deformed at Hypersolidus Conditions. Journal of Petrology, No. 2, 17-40. https://doi.org/10.1093/petrology/Special_Volume.2.17
[53]
Mysen, B.O. and Kushiro, I. (1977) Compositional Variations of Coexisting Phases with Degree of Partial Melting of Peridotite in the Upper Mantle. American Mineralogist, 62, 843-865.
[54]
Navon, O. and Stolper, E. (1987) Geochemical Consequence of Melt Percolation: The Upper Mantle as a Chromatogaphic Column. The Journal of Geology, 95, 285-307. https://doi.org/10.1086/629131
[55]
Fabriès, J., Lorand, J.-P. and Bodinier, J.-L. (1998) Petrogenetic Evolution of Orogenic Lherzolite Massifs in the Central and Western Pyrenees. Tectonophysics, 292, 145-167. https://doi.org/10.1016/S0040-1951(98)00055-9
[56]
Midoun, M. and Perthuisot, V. (1992) Les éléments de socle inclus dans les évaporites du Trias (région d’Oran, Algérie) Implications sur les caractéristiques du substratum et sur l’amincissement lithosphérique triasique. Comptes rendus de l’Académie des SciencesParis, série II, 315, 571-577.
[57]
Teitchou, M., Gregoire, M., Dantas, C. and Tchoua, F.M. (2007) Le manteau supérieur à l’aplomb de la Plaine de Kumba (Ligne du Cameroun), d’après les enclaves de péridotites à spinelles dans les laves basaltiques. Comptes Rendus. Géoscience, 339, 101-109. https://doi.org/10.1016/j.crte.2006.12.006
