New constraints on the Neoproterozoic geological evolution of the SE corner of the Arabian Plate (NE Oman)

Abstract

The Saih Hatat Dome is a tectonic window in northeastern Oman with a NW–SE extent of c. 95 km and an east–west extent of c. 50 km, rimmed by the allochthonous Samail Ophiolite and the tectonically underlying nappes composed of sedimentary rocks from the Neo-Tethyan Hawasina Basin. Rocks within the window were affected by high pressure/low-temperature metamorphism during the latest Cretaceous. Stratigraphically, the Saih Hatat Dome contains a basal, several kilometre thick sequence, made up of low-grade metamorphic volcanosedimentary rocks (Hatat Formation). U–Pb zircon laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) data from a quartzdiorite dyke, intruding the basal part of the Hatat Formation yielded a crystallization age of 845 +2/−4 Ma, whereas zircons from a quartz keratorphyre have ages of 870 ± 5 Ma. Thus, the basal schists of the Hatat Formation are Tonian in age, similar to Tonian felsic volcanic rocks and a granodioritic intrusion in the Huqf area, 300 km to the south. Detrital zircons from the Hatat Formation show an age peak of 837 Ma with some Neoarchean and Paleoproterozoic grains, which have no potential source in the Arabian–Nubian Shield. Based on the new results, we propose that the Hatat Formation signifies a Tonian back-arc basin, contemporaneous with calc-alkaline igneous intrusions in the Jabal Ja'alan region. Similar calc-alkaline intrusions of comparable ages have been identified in the Mirbat area of Dhofar and the Huqf region in central eastern Oman. We interpret these outcrops as components of a cohesive island arc, characterized by calc-alkaline volcanic rocks and volcanosedimentary back-arc sedimentation. Our model situates these regions off the coast of NW India during the Tonian.