Dispersion of the Afar plume: Implications from the Spatiotemporal Distribution of the Late Miocene to Recent Volcanics, Southwestern Arabian Peninsula

Forty-three new K-Ar dates from the Yemen inland volcanic fields (Amran-Sanaʹa, Dhamar-Rada, and Marib-Sirwah field) in the southwestern Arabian Peninsula reveal a progression that can be divided into four stages: Stage 1: 6.4-5.2 Ma, Stage 2: 3.6-2.9 Ma, Stage 3: 2.2-1.7 Ma and Stage 4: <1.3 Ma. It is clear from the data that the volcanic activity shifted northeastward, overlapping partly during Quaternary time. A similar shift has been recognized along the Aden Volcanic Line from Perim Island to the Aden volcanic field (10-5 Ma) [Mallick et al., 1990]. This study shows that the northeastward or eastward shift for the late Miocene to recent volcanic activity on southwestern Arabian Peninsula is about 3-5 cm/year (average: 4.1 cm/year). The rate of shift may reflect the rate of dispersion of an Afar plume head which impinged at 15 Ma on the base of the Arabian plate. We refine and further develop the Afar plume dispersion model proposed by Schilling et al. [1992]; we consider that two Afar plumes impinged on Afar province at 38 Ma and 15 Ma and that they are continuing to disperse under the Arabian lithosphere. The refined dispersion model we propose is consistent with the known geochemical and mantle tomographical features in the Afar-Arabian province and with the spatiotemporal distribution of late Miocene to recent volcanics in the southwestern Arabian Peninsula.