Eocene transitional basalts of the Bamoun Plateau, evidences of an enriched mantle reservoir below the Cameroon volcanic line

• Published in: Comptes rendus. Geoscience Vol. 339; no. 6; pp. 396 - 406
• Main Authors: Moundi, Amidou, Wandji, Pierre, Bardintzeff, Jacques-Marie, Menard, Jean-Jacques, Atouba, Lise Carole Okomo, Mouncherou, Oumar Farouk, Reusser, Eric, Bellon, Herve, Tchoua, Felix M
• Format: Journal Article
• Language: English; French
• Published: 01.05.2007
• ISSN: 1631-0713; 1778-7025
• DOI: 10.1016/j.crte.2007.04.001

Transitional basalts of Eocene age crop out on the western part of the Bamoun Plateau. Basalts of this type are rather scarce in the Cameroon Volcanic Line (LVC). These olivine-free basalts (BSO) lack olivine and have the oldest ages (51.8+/-1.2Ma) of the entire LVC. They differ from the olivine-bearing basalts (BAO, 46.7+/-1.1Ma) on the same plateau, as well as from the typical alkali basalts found elsewhere on the LVC. They closely resemble the rocks of the East-African rifts and Kerguelen Island. They are characterized by the scarcity of modal olivine, a relatively high Y/Nb ratio (1), but low LaN/YbN (10) and CeN/YbN (7) ratios. Moreover, 87Sr/86Sr (0.7044) and 143Nd/144Nd (0.5126) isotopic ratios of BSO are respectively higher and lower than those of BAO (0.7034 and 0.5128) are. These data indicate a source in an enriched lithospheric mantle (EM) that produced the transitional basalts, in contrast to a source closer to HIMU, which could have produced alkali basalts.