Ediacaran anorogenic alkaline magmatism and wolframite mineralization linked to mantle plume activity in the north Arabian-Nubian Shield (Egypt)

Abstract

The termination of the collision between West and East Gondwana and the Pan-African orogeny is somewhat regarded as an endorsement for the generation and intrusion of alkaline magmatism in the Arabian-Nubian Shield. However, the current ages of the Abu Hamar-Abu Kharif alkaline granites have changed this endorsing connection. The Gebel Abu Hamr and Gebel Abu Kharif plutons, exposed in the northern Egyptian Eastern Desert, are anorogenic rift-related granite (A-type) and possess characteristics indicative of a within-plate tectonic setting. Their UPb ages (616.6 ± 6.4 and 614.6 ± 3.6 Ma) are remarkable and provide insight into the initial phase of the anorogenic alkaline magmatism within the shield. The zircon UPb dating, geochemical data, and zircon geochemistry together suggest that the primary magma was formed by the upwelling of a short-lived mantle plume. These alkaline granites subsequently intruded into the crustal mesozone at a thickness of 20–30 km with average temperatures of ~680 °C. The structural framework of the studied plutons reveals a noticeable correlation between their emplacement and the Najd left-lateral fault system. These alkaline granite plutons host wolframite-bearing quartz veins. The in-situ UPb dating of wolframite yielded a weighted mean age of 603.7 ± 7.4 Ma. The trace and rare earth elements of wolframite, zircon, and the hosting alkaline granites share significant geochemical similarities. Nevertheless, the proximity of the UPb age of wolframite and the associated granites suggests an epigenetic origin.