Mantle wedge serpentinization and exhumation of eclogites: Insights from eastern Ladakh, northwest Himalaya

In eastern Ladakh, northwest Himalaya, serpentinite layers occur in close a ssociation with eclogites. The occurrence of metamorphic olivine and talc i n serpentinites suggests that the serpentinization and eclogitization took place under similar conditions (600 degrees C, 20 kbar), The serpentinites and eclogites show similar deformation, including the direction of normal s hearing. The highly refractory nature of the serpentinite protolith, as sho wn by the composition of bulk rocks and chromite and the concentrations of Re and platinum group elements, indicates their derivation from mantle wedg e. We propose that the serpentinites formed by hydration of the mantle wedg e as a result of dewatering of the subducted slab. The serpentinites then f acilitated exhumation of the subducted rocks by acting as a Lubricant. At s hallow depths, sediments are generally considered to be the lubricant for t he exhumation, but serpentinites may commonly take over this role at greate r depths, Under sediment-poor conditions, serpentinites may contribute to t he exhumation even at shallower depths, This mag explain the close spatial association of serpentinites and partially hydrated peridotites with many w ell-known high-pressure to ultrahigh-pressure metamorphic belts worldwide.