Small volumes of peralkaline granites were generated as the final phase of a Pan African calc-alkaline igneous event which built the Arabian Peninsula. The peralkaline granites are closely associated with trends or sutures related to ophiolites. Peralkaline rocks are chemically heterogeneous, with anomalous abundances of Zr (average 2,150 ppm โข 2,600 1 a), Y (200 โข 190), and Nb (105 +_ 100), representing up to ten-fold enrichments of these elements relative to abundances in calc alkaline granite counterparts. Large enrichments of some rare earth elements and fluorine are also present.
The peralkaline granites have scattered whole rock 180 values, averaging 8.7 โข in the Hadb Aldyaheen Complex and 10.7 _+ 1~ in the Jabal Sayid Complex. Quartz-albite fractionations of 0.5 to 1.5% 0 signify that the heavier whole rock &values probably represent the oxygen isotope composition of the peralkaline magma. Small variable enrichments of 1sO, in conjunction with slightly elevated 87Sr/86Sr initial ratios relative to broadly contemporaneous calc alkaline granites, are both suggestive of a small degree of involvement of crustal, or crustal derived material in the peralkaline magmas. It is proposed that the peculiar magma genesis is associated with a relaxation event which followed continental collision and underthrusting of salt rich sediments.