ABSTRACT
Thirty basaltic rock
samples collected from a central Jordan at Ar-Rabba area were studied. The
samples cover about 20 km2 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)-Al2O3,
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.