Neoproterozoic arc sedimentation, metamorphism and collision: Evidence from the northern tip of the Arabian-Nubian Shield and implication for the terminal collision between East and West Gondwana

摘要

In the Wadi Urn Had area, Central Eastern Desert, Egypt, NE-trending metapelitic and molasse-type successions are exposed. The metasediments bear the geochemical signature of a first depositional cycle in two distinct continental island arc settings that derived from incipiently-to moderately-weathered intermediate to felsic sources under generally warm and humid conditions. The metapelitic succession records three distinct episodes of metamorphism, M-1-M-3, whereas the molasse-type succession records only the last metamorphic episode, M-3. M-1/D-1 records an amphibolite facies tectono-metamorphic event that has been dated at 625 +/- 5 Ma, whereas M-2/D-2 records a greenschist facies subduction-related event. Collision of the two domains during a NE-SW shortening D-3, culminated in formation of the macroscopic NW-SE-trending folds. D-2 and D-3 correlate with the gneiss-forming event, which is constrained at <609 Ma, and doming of the nearby Meatiq gneiss dome, respectively. M-3 is a hornblende hornfels facies thermal metamorphism related to the intrusion of the post-orogenic, Neoproterozoic (596.3 Ma) Urn Had granite. This study records, for the first time, a tectono-metamorphic phase predating the gneiss -forming event in the Meatiq gneiss dome, and pushes the boundary of the Late Ediacaran terminal collision between East and West Gondwana to 5.600 Ma. (C) 2018 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.