ACCRETION TECTONICS IN NORTHERN ERITREA REVEALED BY REMOTELY SENSED IMAGERY

New details from remotely sensed images of the structure and dispositi on of broad lithological variations in the Pan-African of northern Eri trea are discussed in the context of accretionary tectonics. The recog nition of major north-south structural discontinuities allows the area to be divided into three discrete terranes with apparently different histories of deformation and metamorphism, magmagenesis and sedimentat ion. The central Hagar Terrane is dominated by large ultramafic masses with a volcano-sedimentary layered sequence, and shows the effects of major sinistral transpression and lateral expulsion. It is bounded to the west by a major fault, the Barka suture, and abuts the older Bark a Terrane that comprises metasediments with evidence for polyphase duc tile deformation and pre-kinematic dyke emplacement. The Hagar Terrane is thrust against the eastern Nacfa Terrane, which is dominated by lo w-grade calc-alkaline metavolcanics and immature volcanoclastic sedime nts intruded by syn-kinematic plutons. These units are pre-dated by an earlier high-grade basement and post-dated by high-level unmetamorpho sed silicic volcanics and redbed sediments. The complex is suggested t o have been assembled by oblique accretion from the southeast after ar c volcanism in the Nacfa Terrane and back-arc extension in the Hagar T errane ended with the cease of subduction.