The Kabus ophiolitic melange, Sudan, and its bearing on the western boundary of the Nubian Shield

Abstract

The Precambrian high-grade gneisses of a continental terrane and the late Proterozoic (Pan-African) low-grade volcanogenic oceanic assemblage of northeastern Nuba Mountains are separated by the Kabus ophiolitic melange. This zone reflects a structural style of imbricate thrusting and strata1 disruption that is attributed to the collision of the Pan-African oceanic assemblage of the Nubian Shield against the pre-Pan-African continental crust to the west. The geological, structural, geochemical and geophysical data indicate that the melange zone marks a fossil plate boundary. The tectonic units of the region demonstrate in-situ deformational patterns that argue against the detached nature that had been previously suggested for the region. Hence, the low-grade assemblage of northeastern Nuba Mountains represent the southwestern extension of the ensimatic Nubian Shield. It is suggested here that the western margin of the Shield is marked by a N-S trending suture extending from the Bayuda Desert in northern Sudan up to the western margin of the Mozambique Orogenic Belt in northwestern Kenya. This suture passes through the Kabus ophiolitic melange.