Post-collisional volcanism with adakitic signatures in the Arabian-Nubian Shield: A case study of calc-alkaline Dokhan volcanics in the Eastern Desert of Egypt

A volcano-sedimentary succession, including the Guruf volcanic series, is exposed at Gabal Um in north Eastern Desert of Egypt. series intermediate to silicic flows and associated pyroclastic deposits unconformably overlie quartz-diorite granodiorite plutons are intruded by high-level alkali feldspar granites. The metavolcanic xenoliths shown be unrelated volcanics. Two cycles can recognized. lower unit a high-K calc-alkaline with minor basaltic andesite mostly through dacite. upper consists rhyolite rhyodacite that transitional towards alkaline, A-type magma. Both units assigned Dokhan volcanics interpreted as post-collisional. REE patterns characterized slow progressive enrichment throughout suite, heavy apparently acting more incompatibly than light REE; concave-upwards basalt suggest residual amphibole source. Only displays prominent negative Eu anomalies (Eu/Eu* = 0.35–0.73). Apparent crystallization temperatures primary pyroxene 800–1000 °C amphiboles 781–944 °C. major trace element chemistry suite modeled single liquid line descent, pressure decreasing magma cools evolves, role for apatite sequestering CaO, P2O5, REE. Although crustal contamination mixing cannot ruled out, data do not require them. includes pyrophanite, an unusual Mn-rich ilmenite-group solid solution, previously recorded rocks Arabian-Nubian Shield (ANS). undeformed unmetamorphosed, unlike typical subduction-related ANS. geochemical characteristics consistent those many post-collisional ANS rocks. character other traits indicate active arc setting instead likely reflect remelting earlier arc-related material from pre-collisional stage (850–740 Ma). lava succession have adakitic characteristics, high Sr, low Y, Yb, Sr/Y, (La/Yb)n. This reflects influence or fractionated crust, rather slab melting during subduction. episode delamination heating tonalitic material, followed asthenospheric mantle, created andesite, amphibole. There no need either late subduction area long-term persistence subduction-influenced local convecting mantle.