New Geophysical Model Suggests Rift-driven Serpentinization

A recent study discusses a new crustal model for the northern North Sea, where high magnetic anomalies combined with low gravity anomalies were found below the western Viking Graben and East Shetland Basin.

New modelA new crustal model for the northern North Sea is discussed in a recent study [1] where high magnetic anomalies combined with low gravity anomalies were found below the western Viking Graben and East Shetland Basin. These anomalies are interpreted to represent appreciable volumes of rocks with very high magnetic susceptibilities and low to intermediate densities. Such rock parameters may indicate serpentinites - as supported by the region's tectonic history. The area is likely the remnant of an island arc in the ancient Iapetus Ocean. In such a model, partly serpentinized peridotites and intermediate intrusives relate to slab dehydration of the subducting oceanic plate below the ancient island arc. Assembled during ocean closure, such serpentinites were expected to persist in the geothermal regime of the Caledonian Orogeny to a depth of at least 50 km. Increased heat flow by later rifting phases may have caused dehydration of the deepest remaining serpentinites. Such fluid release may have triggered further serpentinization of the partially serpentinized peridotites at shallower depths - arguing for rift-related serpentinization to be a more extensive and common process than previously thought.  An alternative origin for the suggested serpentinites, but valid only for the area under the western Viking Graben, may be synrift serpentinization due to the heavy faulting during the Jurassic rift phase.

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