Petrography, Geochemistry and Petrogensis of Basal Flow from Ar-Rabba Area, Central Jordan

Abstract

Thirty basaltic rock samples collected from a central Jordan at Ar-Rabba area were studied. The samples cover about 20 km 2 from the Al-Rabba basalt flow. The Al-Rabba Basalt (RB) introduced Miocene to Pleistocene period. Petrography, Geochemistry and Petrogenesis investigations were carried out for the RB. The petrography analyses of the RB rocks are composed of plagioclase, pyroxene, olivine, opaque minerals (magnetite), and including secondary minerals calcite, iddingsite, and clay. The RB rocks have low range of major and trace elements concentrations, and under sodic alkaline magma series. The geochemical analysis data of RB indicated that RB was derived from a slightly fractionation magma as reflected by high MgO concentration range between (5.4 to 11.7 wt%), and Mg number from 42 to 63.8, and high concentration Cr (18 - 385 ppm), Ni (160 - 364 ppm) and low silica content ( 41.79 - 49.87 wt%). The chemical classification of RB is divided into basaltic, calc-alkaline to alkali basalt. The tectonic setting of RB is explained by using discrimination diagrams, Ti-Zr-Y, Ti-Zr-Sr and MgO-FeO (tot) -Al 2 O 3 , the RB plotted within the plate, calc-alkali and continental basalt respectively. The Rayleigh fractionation equation modeled for Sr and Ba vector diagram indicated the RB had fractionation for clinopyroxene, orthpyro-xene, olivine and trace of plagioclase.