Structure and metamorphism of rocks beneath the Semail ophiolite of Oman and their significance in ophiolite obduction.

Abstract

Metamorphic rocks showing an inverted metamorphic zonation from upper amphibolite facies immediately beneath the peridotite to greenschist facies at lower levels, crop out discontinuously along the base of the Semail ophiolite thrust sheet in the Oman Mountains of eastern Arabia. These metamorphic rocks show polyphase deformation, mylonitic fabrics, and have been disrupted, folded and imbricated, and in places form tectonic inclusions in a serpentinite melange. Relatively low pressures and temperatures of 670-750oC are suggested for the formation of the amphibolites, residual heat from the ophiolites being the dominant heat source. Metamorphism occurred during the Cenomanian-Turonian. The thrusts and other structural features are described. A model for ophiolite obducton is presented based on a palinspastic reconstruction of the allochthonous rocks on the Oman continental margin. -Authors