Detachment faulting in the Xigaze ophiolite southern Tibet: New constraints on its origin and implications

The structure and lithological sequences of ophiolites provide critical information for reconstructing their tectonic setting thus, the history paleo-oceanic basins in which they formed. Our systematic mapping three best-preserved massifs Xigaze ophiolite from middle segment Yarlung Zangbo Suture Zone (YZSZ) South Tibet, revealed a nearly intact ophiolitic sequence that has largely escaped emplacement post-emplacement dismemberment. One most important results is identification E-W striking, serpentinized shear zone (SPSZ) preserved within sequence. SPSZ rooted front upper mantle mainly composed meta-gabbroic rodingite lenses floating serpentinite matrix. Extensive talc-serpentinite metasomatism, shearing cataclastic deformation reveal complex interplay fluid metasomatism progressive ductile-brittle hundreds meters between crust. structural petrological features are very similar to those detachment faults modern situ oceanic core complexes (OCCs) Mid-Atlantic Ridge Southwest Indian Ridge. Zircon UPb ages footwall fault, age radiolarian chert overlying it suggest faulting took place ca. 125 123 Ma. Combined with stratigraphic geochronological relationships sediments, we developed supra-subduction on southern margin Lhasa terrane during rollback Neo-Tethyan slab. Recognition ophiolites, along other features, formed at spreading ridge, whereas large ultramafic YZSZ, may have an off-axis location slow-spreading ridge.