Origin and geotectonic setting of lower Neoproterozoic Kelaat Mgouna detrital material [eastern Anti-Atlas, Morocco])

The Kelaat Mgouna lower Neoproterozoic group consisits of five siliciclasti c formations. It has been considered to have been deposited in a back-are b asin related to a subduction zone corresponding to the 'accident majeur de I'Anti-Atlas'. In this model, the detrital material would have evolved from a volcanic are. In fact, the modal composition of the greywackes and conglomerates and the analysis of the detrital zircon typology lead to a different model comprisi ng a continental passive margin backed by a pre-Neoproterozoic metamorphic basement and orogenic belt. The Kelaat Mgouna Neoproterozoic group was, the refore, deposited in a passive setting within an opening basin synchronous with the extensional pre-Pan-African episode. (C) 2000 Elsevier Science Lim ited. All rights reserved.