THE NATURE OF PLEISTOCENE VOLCANISM IN NORTHEASTERN JORDAN

The distribution of major and minor elements in alkali basalt from Northeastern Jordan indicates homogeneous lava from a mantle source. The MgO and Mg-values (Mg/Mg+Fe) in samples from the volcanoes exhibit different degrees of fractionation which lead to the formation of these rocks. The low concentration of incompatible trace elements would imply derivation from partial melting of upper mantle spinel-l herzolite zone. The basalts include spinel-l herzolite xenoliths; this would indicate derivation and equilibration under upper mantle conditions with low degree of melting (<20%). The spinel-l herzolite did not equilibrate with the melt, indicating that transport from mantle to the surface was rapid, olivine in xenoliths show no zoning.