Petrochemical evidence for diversity of magma compositions at the northwestern Ethiopian volcanic province

概要

論文の詳細を見る
Petrographic characteristics and whole-rock major and trace element data are presented for the Bure volcanic rocks from the northwestern Ethiopian plateau of East Africa continental flood basalt province, to investigate the processes that involved in the genesis of the erupted magma and its source composition during plume-induced continental rifting. The Bure area is mainly composed of stratified basalts, recent basalts, scoria cones and trachyte plugs. The successions of the erupted basalts are from transitional tholeiites to alkaline basalts. The transitional tholeiites have higher Zr/Nb (8.88-21.86) and Rb/Nb (0.66-1.87) than those of the alkaline (Zr/Nb=2.19-6.21, Rb/Nb=0.26-0.74), indicating that they are originated from distinct magma sources. The compositional variation in the transitional tholeiites cannot be explainable in terms of fractional crystallization of common (or similar) primary magma; instead it reflects the involvement of various mantle and crustal components in their petrogenesis. By contrast, the variation in the alkali suite can be explained by dominant fractional crystallization process of OIB-like primary basalts that derived from the Afar mantle plume. The strong lithospheric signature observed in the transitional tholeiites suggests pronounce interaction between the Afar plume and the lithosphere at the initial stage of continental break-up.
琉球大学理学部の論文