The geology of Socotra Island, Gulf of Aden

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Abstract
Basement rocks crop out in three main uplift areas; elsewhere they are overlain by a veneer of Cretaceous and Tertiary plateau limestones. The oldest basement rocks are amphibolite facies meta-sediments and meta-igneous rocks which have been intruded by synkinematic granites and late-kinematic gabbros; younger weakly metamorphosed tuffs and mudstones also occur. Post-kinematic igneous activity gave rise to a sequence of volcanic rocks, hornblende/biotite and peralkaline granites, gabbros and minor intrusions which make up the bulk of the Haggier mountains. Of these the large occurrence of peralkaline granites is considered in detail. Following a long period of basement peneplanation, sediments were deposited which consist of Lower and Middle Cretaceous limestones, with some basal sandstones, followed without apparent break by cliff-forming shelf limestones of Palaeocene-Eocene age. Oligo-Miocene chalky deposits are only preserved in structural depressions. Vertical movements were predominantly responsible for the structure which is simple in the east but dissected by wnw–ese block faulting in the west. Correlation with southern Arabia and Somalia suggests that the basement metamorphic association is Pre-Cambrian and the post-kinematic igneous rocks are early Palaeozoic; the sedimentary formations broadly correlate with those of southern Arabia and the Oligo-Miocene deposits in particular are most closely related to those of Dhufar.