Field survey, satellite image interpretation, geological map interpretation, literature review, GPlates reconstruction and LA-ICP-MS U-Pb dating of synkinematic calcites demonstrate that ~E/W-shortening in eastern Oman was significant and related to oblique convergence of Arabia and India from 32.5 to 20 Ma. Approximately N/S-oriented compressive structures, WNW to NNW-striking sinistral faults and ~E/W-oriented normal faults characterize a major shear zone in the eastern Oman Mountains (Hajar Shear Zone, HSZ) and its wrench-fault assemblage within an area spanning ~250 km x ~50 km. More than 10,000 mostly NW-striking lineaments as deduced from satellite image interpretation and numerous faults/folds indicate that strain of the HSZ is widely distributed but concentrated along WNW to NNW-striking major faults/fault zones at the SW margin of the Saih Hatat Dome. These faults/fault zones represent reactivated basement faults. GPlates reconstructions reveal that N-drifting India rotated 8° counter-clockwise with respect to fixed Arabia from 32.5 to 20 Ma, leading to ~100-135 km E/W-convergence between both plates (minimum value). This convergence created the sinistral HSZ with a displacement of a few to several tens of kilometers. Independently from the GPlates time constraints, two U-Pb ages of synkinematic calcites, crystallized along faults during HSZ movement, yield compatible ages of 30.08 ±0.47 and 22.31 ±2.15 Ma (2 standard error). E/W-shortening also affected the northern Oman Mountains, creating the ~N/S-oriented Hagab Thrust in the Musandam Peninsula and the Jabal Hafit Anticline.

Magmatic products of the Karoo Large Igneous Province can be divided into a volumetrically dominant, compositionally uniform low-Ti tholeiitic suite, and a subordinate, geographically restricted, compositionally diverse, incompatible-rich high-Ti suite. High-Ti picrites contain up to 2400 ppm Sr, 1900 ppm Ba and 550 ppm Zr, which seems unusual for olivine-enriched mafic rocks. We studied six Karoo picrites to determine the phase(s) in which Sr resides. Samples consist of 10–30% olivine phenocrysts in a groundmass of brown glass, augite, feldspar, ilmenite and apatite. Glass compositions vary, but are generally evolved, ranging from basaltic trachyandesite to trachyte to dacite. X-ray intensity maps demonstrate that most of the Sr resides in the glasses, and to a lesser extent, in feldspars, if present. The highest Sr (up to 9470 ppm) occurs in glasses adjacent to euhedral olivines, suggesting that phenocrysts are genetically related to evolved liquids represented by surrounding groundmasses. Compositional arrays formed by whole rocks (WRs) and bulk groundmasses represent liquid lines of descent. Calculated parental melts have much higher KO and incompatible trace elements (e.g. Sr or Ba >1200 ppm) relative to low-Ti tholeiites. Fractional crystallization modelling yields evolved residual liquid compositions corresponding to those of glasses, and closely follow liquid evolution predicted by mass balance calculations involving mineral and bulk groundmass compositions. The unusual parental melt compositions imply derivation by small degrees of partial melting from SCLM mantle sources enriched in Sr and other incompatibles, and suggest a possible petrogenetic link between the high-Ti Karoo magmas and carbonatites and kimberlites.