Seismic faults triggered early stage serpentinization of peridotites from the Samail Ophiolite, Oman

Serpentinization of mantle peridotites has first order effects on the rheology and tectonic behavior oceanic lithosphere, global water cycle, biosphere at mid-oceanic ridges. Investigating serpentinization abyssal is limited by scarce occurrences or close to ocean floor slow ultra-slow ridge environments where peridotite exposed long-lived detachments. The processes controlling hydration upper below a thick magmatic crust fast spreading ridges are poorly constrained. Here we present results based samples from cores drilled in Samail ophiolite obtained during Oman Drilling Project. We describe an early generation highly localized brittle faults ubiquitous through all investigate their relation main event represented mesh-textured serpentinites. combine microstructural observations with mineral bulk chemical analyses as well oxygen isotope microanalyses secondary ion mass spectrometry (SIMS). Asymmetric wall rock damage, weakening crystal preferred orientation (CPO) small fault clasts, intense fragmentation within zones even association very displacements suggest that stage represent seismic events predate mesh formation. Hydration texture formation follows wake this faulting. associated moderate enrichment fluid mobile elements including B, Li, Rb U, indicative interaction characterized relatively low fluid/rock ratios. This consistent scenario took place following earthquake-induced permeability increase. compositions serpentine off-axis temperatures range 200-250 °C