Serpentinized peridotite versus thick mafic crust at the Romanche oceanic transform fault

Abstract The crust beneath transform faults at slow-spreading ridges has been considered to be thin, comprising a thin mafic layer overlying serpentinized peridotite. Using wide-angle seismic data, we report the presence of Moho ?6 km depth and low-velocity anomaly extending down 9 20-km-wide Romanche valley floor in equatorial Atlantic Ocean. low crustal velocities above could due either highly mantle peridotite or fractured rocks. existence clear reflections occurrence large crustal-depth rupture during 2016 magnitude 7.1 earthquake suggest that likely consists material. Furthermore, below advocates for extensive serpentinization mantle, indicating reflection is unlikely produced by front. north fault material, but south appears more amagmatic, possibly containing Our results imply structure complex heterogeneous, thus would have significant influence on alteration processes.