An inference of the tectonic setting of the Adola Belt of Southern Ethiopia from the geochemistry of magmatic rocks

Abstract

The Adola volcano-sedimentary belt of southern Ethiopia has been referred to as a late Proterozoic ophiolitic belt within the Mozambique belt of East Africa. The bulk chemistry of three units - an amphibolite, a tonalite and a calc-alkaline granite - to the west of the main axis of this belt indicate that they are related to an oceanic arc: the amphibolite and the tonalite are chemically similar to low-K tholeitic mafic rocks and calc-alkaline plutons in island arc settings respectively.

From these data, and previous regional works it is inferred that magmatic rocks in the Adola belt were emplaced in a late Proterozoic immature oceanic arc that appears to have evolved over a west dipping subduction zone.