Petrogenetic Evolution of Pleistocene Alkaline Basanites of Harrat Dahrat Humayyan,Northeast Arabian Shield,Saudi ArabiaOA

This study addresses the origin and evolution of Early Pleistocene basanites from Harrat Dahrat Humayyan(HDH)in the northeastern Arabian Shield,part of the Hutaymah volcanic field.Integrated mineralogical,geochemical and thermobarometric data are used to constrain magma genesis and mantle source characteristics beneath the Arabian Plate.The HDH basanites display features typical of anorogenic alkaline volcanism associated with continental rifting.Thermobarometric estimates indicate crystallization temperatures of 1420-714℃and pressures of 3.1-0.4 GPa,with early olivine crystallization followed by clinopyroxene and feldspar.Trace element modelling suggests that the magmas were derived from low degree partial melting(7%-12.5%)of a heterogeneous garnet-spinel peridotite mantle source.The rocks are enriched in incompatible elements and show rare-earth element(REE)patterns consistent with limited crustal contamination,implying rapid magma ascent.Their prevalent mantle(PREMA)-like geochemical signatures resemble those of other Cenozoic intraplate volcanic provinces in Arabia and elsewhere.These signatures are best explained by melting of a fusible mantle domain triggered by lithospheric extension associated with Red Sea rifting.Overall,the results support a model of passive mantle upwelling beneath an extending lithosphere and provide new insights into mantle heterogeneity and melting processes.