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The Neyriz ophiolite in SW Iran includes a NNW-SSE-trending, steeply dipping oceanic palaeo-transform fault zone that consists mainly of deformed and sheared gabbros and peridotites. Mylonitic rocks within the fossil palaeo-transform fault display C-, C'-and S-band shear cleavages containing green hornblende-and feldspar-rich bands. Deformed hornblendemantled porphyroclasts have symmetrical tails or o-type porphyroclast systems, which show clockwise stair-stepping rotation and oblique foliation with asymmetrical complex stripes and wings. These microstructures indicate dextral shearing on the palaeo-transform fault. The caxes of hornblende in high-grade S-C mylonitic rocks exhibit strong lattice-preferred orientation (LPO) patterns with M-and G-type origin. These LPO patterns are asymmetrical with respect to the shear zone foliation and also indicate dextral shearing. The NNW-SSE trend of the palaeo-transform fault is perpendicular to the general NE strike of sheeted dykes and is parallel to the average harzburgite foliation. These observations suggest a noncoaxial shear orientation of mantle flow, which progressively rotated toward parallelism with the fossil fracture zone. This dextral transform fault is inferred to have connected ENE-trending oceanic spreading centre segments in a Neo-Tethyan ocean basin.

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