オフィオライトの応力構造 : サマイル・オフィオライトを例として

概要

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The stress history of Semail ophiolite, northern Oman mountains, is presented. The axial orientation of regional stress field is obtained using conjugated ductile shear zone pairs and sheeted dikes. The results are; the early E-W extension changing into the later E-W compression at 100Ma. The conversion of stress field is best interpreted by the initiation of a subduction; this model is not inconsistent with the petrological and geochemical data (UMINO et al. 1989). The subducting plate, the African plate, dipped gently to the north, and generated an arc, the Semail Arc, above it. The Semail Arc was topographical highs trended N30 W. Assuming that the A1 orientation in the Arc is controlled by the relative motion of converging plate, the subduction should be sinistrally oblique. The plate convergence was completed at the final Arabia Continent-Semail Arc collision.