Geochemistry and Geotectonic Setting of Neoproterozoic Rocks from Northern Ethiopia (Arabian-Nubian Shield)

Whole-rock geochemical analysis of metavolcanic and plutonic rocks from Mai Kenetal-Negash area, Tigrai, northern Ethiopia was carried out to evaluate their magma type and original tectonic environment. Their major element content has been modified by secondary alteration, and trace and rare-earth elements have been used to investigate their petrogenesis. The low content of compatible elements of the metavolcanic rocks and their relatively high content of incompatible elements and light REE point to a depleted source region, whereas the plutonic rocks show a more pronounced REE fractionation (LaN/LuN >4). Metavolcanic and plutonic rocks seem to be cogenetic. Discriminant diagrams suggest that the majority of the metavolcanic and all the plutonic rocks are members of a calc-alkaline suite developed in a volcanic arc setting. The overall geochemical characteristics of both sets of rocks are consistent with the arc accretion models postulated in Sudan, Egypt and Saudi Arabia for the Neoproterozoic evolution of the Arabian-Nubian Shield.