EVIDENCE FOR A PANAFRICAN VOLCANIC ARC AND WRENCH FAULT TECTONICS IN THE JBEL SAGHRO, ANTI-ATLAS, MOROCCO

The Saghro hills constitute the northern branch of the Panafrican mobi le belt in the eastern part of the Moroccan Anti-Atlas. The Precambria n terranes are predominantly composed of volcaniclastic and volcanic s eries witnessing a mainly explosive volcanism, intruded by diorites an d granites. Their age attribution is problematic, and has been reconsi dered in the present study based on structural evidence and Rb/Sr data of quartz-diorites: penetratively deformed volcano-sedimentaries intr uded by these plutons aged between 754 and 722 Ma are now considered a s Lower Precambrian II. The Upper PII series have been reattributed, a nd only formations overlying a basal conglomerate and angular disconfo rmity are considered PIII. Main schistosities are predominantly NE-SW, cut by conjugate sets of strike-slip shear zones. In the Saghro area NW-SE compression can explain the observed structures during this main Panafrican deformation phase, while fault kinematics and dike emplace ment related to late deformation events indicate rather a NE-SW compre ssion. The explosive volcanism of the Saghro area can be related to a volcanic arc, active during the subduction- and collision-related Pana frican deformations. This arc would be located on the upper plate in r espect to the northward dipping subduction zone evidenced in Bou Azzer - El Graara inlier (SAQUAQUE et al., 1989a).