Petrochemistry and origin of sub-ophiolitic metamorphic and related rocks in the Oman Mountains.

Abstract

The Semail ophiolite complex was obducted during Cenomanian to Campanian times onto the Arabian continental margin. During this time schistose metamorphic rocks of amphibolite and greenschist facies showing polyphase deformation were formed and accreted below the ophiolite slice. Rock and mineral analyses confirm that the amphibolites were originally tholeiitic basalts comparable to present-day occurrences at mid-ocean ridges; however, their trace-element content is different from the rocks immediately associated and it is thus suggested that these amphibolites may have been derived from Jurassic or Lower Cretaceous oceanic basalts not recognized elsewhere in the Oman Mountains. Structurally beneath the amphibolites within the metamorphic sheet, greenschist-facies metasedimentary rocks, including quartzites and marbles, are interbanded with metabasic horizons containing actinolite and, less commonly, blue crossitic amphiboles.-R.A.H.