Abstract
The western margin of northern Afar Depression constitutes various rock units of Neoproterozoic basement complex. Major oxide data of metavolcanic and granitoid rock samples from basement complex indicate significant variation in the concentration of major oxides (e.g. Fe 2 O 3 , TiO 2 , CaO, MgO). Metavolcanic rocks of Dallol demonstrate heterogeneous nature of magma source. The mafic metavolcanics indicate two distinct groups, (i) CaO-enriched and (ii) tholeiitic composition. Another group of magmatic series, the felsic metavolcanic group, shows a co-genetic relationship with the tholeiitic metavolcanics. Granitoids on the other hand have a wider range of SiO 2 (61.5 – 76.65 wt %) and are peraluminous to metaluminous in nature. Keywords : Geochemistry, Metavolcanics, Granitioids, Dallol, Northern Afar Depression, Ethiopia.
Highlights
The northern tip of Afar Depression/ Dallol area is interestingly comprised of the Neoproterozoic basement complex, Mesozoic sedimentary succession and thick Miocene to Quaternary evaporite deposits (Redfield et al, 2003)
The oldest clastic sediments (Lower Sandstone) are generally early Triassic or possibly Permian overlying the basement complexes, with younger formations (Upper Sandstone) extending into the early Cretaceous (Bosworth et al, 2005). These Mesozoic sedimentary successions correspond to a major transgressive–regressive cycle, which has been assigned to the Adigrat–Amba-Aradom formations
Out of 45 rock samples were collected from metavolcanics, metavolcaniclasts, phyllites, slates, laterites, basalts, and rhyolites, 32 from metavolcanics, volcanics and granite were selected for the study and geochemical analysis
Summary
The northern tip of Afar Depression/ Dallol area is interestingly comprised of the Neoproterozoic basement complex, Mesozoic sedimentary succession and thick Miocene to Quaternary evaporite deposits (Redfield et al, 2003). The Neoproterozoic basement, which represents part of the Arabian-Nubian Shield, is prevalent on the periphery of the Afar Depression. The Arabian-Nubian Shield covers vast terrain to the north and northwest of the Afar Depression and in eastern Eritrea (Beyene and Abdelsalam, 2005 and references therein). The fabric and nature of deformation of the metamorphic rocks at northern Afar is similar to the 850 Ma Tsaliet and 800-735 Ma Tambien Group rocks of Tigray region (Beyth, 1972; Teklay, 1997; Alene et al, 2006)
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