Forming and preserving aragonite in shear zones: First report of blueschist facies metamorphism in the Jabal Akhdar Dome, Oman Mountains

We report the first occurrence of high-pressure metamorphic aragonite in Precambrian carbonates of the Jabal Akhdar Dome in the Oman Mountains (northern Oman). We propose a model for both its formation at blueschist facies conditions and its subsequent preserva-tion to the surface within the tectonic framework of the Late Cretaceous obduction of the Semail Ophiolite. Aragonite formed at temperature similar to 350 degrees C and pressure >= 0.9 GPa and is preserved within mylonitic shear zones and in stretched-fiber dilational veins where the necessary conditions for its formation and preservation, such as plastic strain accommoda-tion, fluid-enhanced mineralogical reactions, and an anisotropic permeability structure, were preferentially met with respect to the surrounding rock. High-strain structural domains are ideal sites to look for and study prograde and retrograde high-pressure metamorphic histo-ries in deeply subducted and exhumed terrains.