Petrology and Origin of Ultramfic Xenoliths from North Eastern Jordan Volcanoes

Abstract

The distribution of major, minor and trace elements in the Cenozoic alkali basalt from north-eastern Jordan indicates a homogeneous lava flow from a mantle source. These basaltic rocks contain abundant upper mantle xenoliths (spinal lherzolite, harzburgile and olivine- websterite). Theses xenoliths contain olivine, orthopyroxne, clinoporoxene and a few amounts of spinal. Their mineral assemblages, chemistry, texture and major elements abundances indicate they were derived and equilibrated under upper mantle conditions within temperature range for 970-1090°C. Pressure estimates based on the spinal lherzolite stability field restrict the xenoliths source depth to around 65 km. The concentrations of incompatible trace elements (Ba, Rb and Sr.) imply a derivation from ultramafic predictive source from the upper mantle with low degree of melting (<20%). Low concentration of Lithium and Rubidium in the basalt is used as an argument against the contamination of the basaltic magma during its journey to the surface.