Magmatism of the eastern Red Sea margin in the northern part of Yemen from Oligocene to present

Abstract

The northern part of Yemen during the last 30 Ma has been the site of an intense magmatic activity which can be divided into three main episodes. The first episode lasted from 30 to 18 Ma and was characterized by two climaxes. Huge flood basalt eruptions between 30 to 26 Ma were succeeded by massive ignimbrite sheet deposits and intrusion of silicic subvolcanic masses 22 to 20 Ma ago. Contemporaneously, along the present-day western margin of the Yemen Plateau a basaltic dike swarm was emplaced. Additionally, alkaline and peralkaline granites were intruded at the end of the first climax and throughout the second. After a long quiescence, magmatic activity occurred again in Late Miocene time (about 10 Ma) with extrusion of lava flows in scattered areas (e.g. Al Harf, Wadi As Sirr, Maswar Al Hada, Jabal An Nar). The third magmatic episode has been concentrated in three well defined areas. It began about 6.5 Ma ago in the Dhamar Rada area and later in the San'a Amram and Sirwah Marib areas. New chemical and isotopic data on the magmatic products of North Yemen indicate that extensive crustal contamination, together with simple crystal fractionation processes, have been operating during the magmatic evolution. The most primitive products of each of the three episodes share isotopic and petrological features suggesting a similar mantle source. Isotope geochemistry indicates an important asthenospheric component in the mantle source for the magmas of all three episodes. Finally, a comparison between the coeval igneous rocks of the Yemen and Ethiopia plateaus is attempted.