Alkaline magmatic rocks from the Late Triassic to Early Cretaceous Qastal Almaaf Melange, northwest Syria

The Qastal Almaaf Mesozoic melange is one of several melange occurrences recording evidence of deep-water sedimentation and volcanism preserved in northwest Syria. The alkaline volcanic rocks constitute the majority of rocks in the upper part of the melange that is tectonically overlain by serpentinized ultramafic rocks belonging to the Baer-Bassit Ophiolite Complex. Petrographically, these alkaline rocks form a magmatic complex ranging from mafic to intermediate varieties. Phonolite-trachyte and biotite-augite basanite are the two most abundant lithologies.A major and minor elements analysis of the Qastal Almaaf alkaline magmatic rocks was carried out in order to characterize their salient geochemical features. The geochemical characteristics of the two most common rock types (i.e. the phonolite-trachyte and basanite) show that they are related by crystal fractionation processes. Major and trace element variations are interpreted to have resulted from the fractionation of alkali feldspar, nepheline, clinopyroxene and Fe-Ti oxides. Generation of the basanitic magma parental to the investigated alkaline magmatic complex is thought to have involved partial melting of upper mantle rocks related to plume interaction, at an intra-plate setting in northwest Syria during the Late Triassic to Early Cretaceous time.