Estimating original thickness and extent of the Semail Ophiolite in the eastern Oman Mountains by paleothermal indicators

The sedimentary succession from the northern flank of the JAC shows a clay mineral assemblage characterized by long-range ordered mixed layer I-S with an illite content between 85% and 92% and the occurrence of pyrophyllite and/or paragonite, suggesting maximum paleotemperatures between 150° and 200 °C in deep diagenetic conditions. On the southern flank of the JAC, temperature dependent clay minerals indicate maximum paleotemperatures, ranging between 120° and 150 °C, indicating a reduced ophiolite thickness towards the south. Ooid strain analyses of the subophiolite rocks from the northern flank of JAC show a component of flattening and stretching in the z-x plane as a result of plastic deformation and pressure solution. On the southern flank, such ductile deformation is absent, suggesting a brittle rheology for the subophiolite carbonates and a reduced overburden. 1D thermal modeling reveals that the sub-ophiolite units of the JAC were overthrust by 4.5 km-thick Semail Ophiolite and Hawasina units during the Coniacian, and exhumed since the Campanian. The subophiolite rocks of the Jabal Salakh Range were buried under 1.35 km of synobduction clastics and overthrust by 2 km-thick Hawasina units, suggesting a decrease of the thickness of allochthonous units from NE to SW, consistent with strain analysis and their direction of emplacement.