Mantle-crustal Source of Mafic-felsic Magmas in the Dubr-Igla Intrusive Complex, Egypt: Inference from

ABSTRACT. The Dubr-Igla intrusive complex (DIC) is a composite batholith intruded into the Pan-African terrain of the Egyptian base-ment complex. It represents an uplifted tectonic block, comprising a diverse rock association ranging from gabbro to granite. These rocks belong to two distinct suites; the gabbroid-diorite (mafic-intermediate) and granodiorite-monzogranite (felsic) suites. The gab-broid-diorite suite has a calc-alkaline affinity and an overall depletion of Nb, Y, K, and Rb with slightly fractionated REE pattern (La/Ybn = 0.96-3.72). The granodiorite and monzogranites are late to post or-ogenic calc-alkaline rocks with metaluminous to mildly peraluminous character and are relatively enriched in LIL elements but depleted in HFS elements. They have fractionated REE patterns (La/Ybn =2.62-6.97), flat HREE (Gd/Ybn = 0.89-1.10) and well-developed negative Eu anomalies (Eu/Eu =0.74-3.0). The granitoid rocks of the DIC have trace element and REE signatures characteristic of I-type granites formed in subduction-related, arc environments. The whole-rock Rb-Sr isochron ages of the monzogranites and the diorite-quartz diorite from DIC are 644 ± 7 Ma and 704 ± 13 Ma, re-spectively. The diorite-quartz diorite shows a narrow range of tNd (+ 6.7- + 8.5) and initial 87Sr/86Sr ratio (0.7022-0.7025). These iso-topic characteristics and the overall depletion of the LIL elements and LREE and low Rb/Sr suggest that they had been derived from a de-pleted mantle source. The granodiorite and monzogranites have low initial 87Sr/86Sri ratio (0.7025- 0.7035) and positive spread tN