Petrology, geochemistry, and geodynamic implications of the Ediacaran volcanism of the southwestern edge of the Saghro massif (Eastern Anti-Atlas, Morocco)

Abstract

The southwestern edge of the Saghro Massif experienced during the Ediacaran period an intense volcanic activity represented by basaltic andesites and acid rocks with ignimbritic dominance. The chemical characteristics of these rocks correspond to those of calc-alkaline orogenic magmatism related to a subduction zone. The genesis of these two rock groups does not seem to be controlled by the fractional crystallization process as a factor controlling their evolution. Partial melting of a lithospheric mantle still influenced by the Pan-African orogeny and a contaminated constituent of the lower continental crust is a likely source of the basaltic andesites. Ignimbrites represent the product of the anatexic melting of sialic material in contact with basic magmas. Despite the calc-alkaline and orogenic character, the genesis of the studied rocks would be linked to a Pan-African distensive postcollisional tectonic context.