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SUMMARY:Deep hydration and lithospheric thinning at oceanic transform plat
 e boundary - Zhikai Wang - Institut de Physique du Globe de Paris
DTSTART:20221102T160000Z
DTEND:20221102T170000Z
UID:TALK182075@talks.cam.ac.uk
CONTACT:Yihe Xu
DESCRIPTION:Transform faults accommodate the lateral motions between litho
 spheric plates\, producing large earthquakes. Away from active transform b
 oundaries\, former oceanic transform faults also form the fracture zones t
 hat cover the ocean floor. However\, the deep structure of these faults re
 mains enigmatic. Here we present ultra-long offset seismic data from the R
 omanche transform fault in the equatorial Atlantic Ocean that indicates th
 e presence of a low-velocity anomaly extending to about 60 km below sea le
 vel. We performed three-dimensional thermal modelling that suggests the an
 omaly is probably due to extensive serpentinization down to about 16 km\, 
 overlying a hydrated\, shear mylonite zone down to 32 km. The water is con
 sidered to be sourced from seawater-derived fluids that infiltrate deep in
 to the fault. Below 32 km is interpreted to be a low-temperature\, water-i
 nduced melting zone that elevates the lithosphere–asthenosphere boundary
 \, causing substantial thinning of the lithosphere at the transform fault.
  The presence of a thinned lithosphere at transform faults could explain o
 bservations of volcanism\, thickened\ncrust and intra-transform spreading 
 centres at transform faults. 
LOCATION:Wolfson Lecture Theatre
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