Early Miocene strike-slip tectonics and granite emplacement in the Alboran Domain (Rif Chain, Morocco): Significance for the geodynamic evolution of Western Mediterranean

摘要

The Neogene tectonic evolution of the western Mediterranean region is accompanied and outlasted by diffuse magmatism. This study describes the tectonic setting, the petrography and geochemistry of the Early Miocene granitic dyke swarm that occurs in the Oued Amter area, in the core of the Alboran Domain of the Moroccan Rif. The structural setting indicates dyke intrusion assisted and controlled by strike-slip tectonics that operated through conjugate, NW-SE left-lateral and NE-SW right-lateral fault strands. The overall composition of the dykes (the high SiO_2 contents (69-77wt.%), coupled with low concentrations of TiO_2, MgO, FeO, CaO), the high ~(87)Sr/~(86)Sr (0.719-0.722) and the low ~(143)Nd/~(144)Nd (ca. 0.5120) values point to a predominantly crustal origin of these magmatic bodies, compatible with a process involving muscovite-(biotite) dehydration melting of fertile metasedimentary sources. The isotopic signature is similar to that of the basement rocks of the Alboran Sea, suggesting for a similar crustal source for the Early Miocene felsic magmatism of the Betic-Rif realm. When framed within the regional setting, these data are used to propose a synthetic geodynamic model for the Early Miocene tectonic and magmatic evolution of the western Mediterranean region.