Les basaltes éocènes à affinité transitionnelle du plateau Bamoun, témoins d’un réservoir mantellique enrichi sous la ligne volcanique du Cameroun

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• 作者：Amidou Moundi ; Pierre W ; ji ; Jacques-Marie Bardintzeff ; Jean-Jacques Mé ; nard ; Lise Carole Okomo Atouba ; Oumar Farouk Mouncherou ; É ; ric Reusser ; Hervé ; Bellon ; Fé ; lix M. Tchoua
• 关键词：Transitional basalts ; Bamoun Plateau ; Cameroon Volcanic Line ; WR K/Ar Ages ; Isotopes (Sr ; Nd) ; Mantle reservoir ; EM ; HIMU
• 刊名：Comptes Rendus Geoscience
• 出版年：2007
• 出版时间：May 2007
• 年：2007
• 卷：339
• 期：6
• 页码：396-406
• 全文大小：827 K

文摘

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 ± 1.2 Ma) of the entire LVC. They differ from the olivine-bearing basalts (BAO, 46.7 ± 1.1 Ma) 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 La_N/Yb_N (10) and Ce_N/Yb_N (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.