The evolution of the Neoproterozoic Elat Metamorphic Complex, northernmost Arabian-Nubian Shield: Island arc to syncollisional stage and post-collisional magmatism

Abstract

The Elat Metamorphic Complex (EMC), part of the Arabian-Nubian Shield exposed at Elat and Taba areas (S. Israel and NE Sinai, Egypt), records a full orogenic cycle from island arc to syncollisional stages that extended ∼240 My. New SIMS U–Pb dating of zircons in five samples, combined with published U-Pb zircon data, enable precise timing of formation of metamorphic and magmatic rock units and associated tectonic events. The island arc stage extended from 870 to 740 Ma. The oldest rocks are metasediments derived from island arc volcanics, metamorphosed and penetratively deformed prior to intrusion of island arc tonalite and granite plutons. The island arc stage was followed by a non-active stage from 740 to 670 Ma. The collisional stage that terminated the orogenic cycle commenced with plutonic activity of basic rocks and granitoids from 670 to ∼635 Ma, followed by deformation and metamorphism of both island arc and syncollisional rocks. During the collisional stage, island arc rocks were uplifted, exhumed and eroded; the volcano-sedimentary rocks of the Gishron Formation were deposited on the erosional surface, and then were deformed. Early post-collisional high-K calc-alkaline plutonic activity immediately followed the syncollisional stage from 635 to 610 Ma, and was exhumed at the end of this stage. A late post-collisional within-plate alkaline magmatic stage ensued (610–530 Ma), beginning with basic and acid volcanism, followed by intrusion of alkaline granite plutons, and in the end by late sub-volcanic bodies and dikes. New geochemical data for 26 representative samples combined with 150 published chemical analyses reveal consistent compositional change of similar rock types over time. The most graphic example for this change is the sequential increase of K2O and HFSE content in similar magmatic rock types, basic rocks, intermediate rocks, low-silica granitoids, and granites, from the syncollisional to the end of late post-collisional within-plate stage, over 80–90 My. The ∼740 Ma island arc granitic gneisses are however chemically similar to the syncollisional granitic gneiss and post-collisional granites.