Abstract
THE west Galicia passive margin (Spain) is bounded by a continuous belt of serpentinized peridotite. Here we present the results of petrological studies of the peridotite, 39Ar–40Ar dating of high-temperature ductile shearing of a dioritic dyke crossing the peridotite and regional seismic stratigraphy which demonstrate that the uplift, ductile shearing and pervasive serpentinization of mantle rocks occurred at early Cretaceous time, during the rifting stage of the margin. The serpentinite layer resting on fresh peridotite is probably several kilometres thick. At present seismic data and gravity data cannot distinguish serpentinite from crustal material, but our results from the Galicia margin indicate that the seismic crust beneath rifted margin may include mantle material transformed into serpentinite by syn-rift hydrothermal activity. In some cases, this undercrusting process might explain the young age and mobility of the Moho beneath stretched continental basement.
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Boillot, G., Féraud, G., Recq, M. et al. Undercrusting by serpentinite beneath rifted margins. Nature 341, 523–525 (1989). https://doi.org/10.1038/341523a0
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DOI: https://doi.org/10.1038/341523a0
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