The Neogene ash-flow caldera of A'ithayn: an eruptive centre upon the trap series in central North Yemen

Abstract

Abstract The main type of eruptive vents on the Yemen Plateau are dykes; monogenic and composite dykes are present. In addition, a morphologically well preserved ash-flow caldera with a diameter of 10 km is identified as the eruptive centre of extensive surrounding volcanics. It is situated in the centre of the Yemen Arab Republic, 40 km south of Sana'a and NW of Ma'bar. The caldera and its products are younger than the underlying Trap Series and perhaps of Pliocene age. In comparison to the 5–6.5 Ma old calderas in South Yemen the structure shows a much better state of preservation. Striking differences exist between the silicic rocks erupted from the caldera and those in the underlying Trap Series. We emphasise that a high proportion of silicic rocks is a feature of the central Yemen Trap Series. In contrast to the Ethiopian plateaus, a dominant role for basalts is not evident at the structural levels examined.