THE GEOCHEMISTRY AND PETROGENESIS OF THE LATE CRETACEOUS ABU KHURUQ ALKALINE COMPLEX, EASTERN DESERT, EGYPT

The Late Cretaceous rocks of the Abu Khuruq ring complex (AKRC), exposed in the southern Eastern Desert, Egypt, comprise phonolite, trachyte, syenogabbro, essexite, nepheline syenite, and quartz syenite, as well as quartz- and nepheline-bearing pegmatites. The rocks of the complex are dominantly metaluminous and enriched in both large-ion lithophile (LIL) and high-field-strength (HFS) elements with a lack of a negative Nb anomaly. All rocks have high LREE content relative to HREE, show weak to steep fractionated REE patterns [5.6 n n n in the ranges 12.0–13.7 and 15.6–18.6, respectively]. They have relatively weakly fractionated HREE patterns [3.0 n n and Lu n values ( n n n in the range 0.5–1.1]. This marginal unit may well have been derived from the SiO 2 -undersaturated syenitic magma, but it was contaminated by crustal material.