Istituto di Geoscienze e Georisorse     
Spengler D., Van Roermund H., Drury M., Ottolini L., Mason P., Davies G. Deep origin and hot melting of an archaean orogenic peridotite massif in Norway. In: Nature, vol. 440 pp. 913 - 917. Nature Publising Group, 2006.
The buoyancy and strength of sub-continental lithospheric mantle is thought to protect the oldest continental crust (cratons) from destruction by plate tectonic processes. The exact origin of the lithosphere below cratons is controversial, but seems clearly to be a residue remaining after the extraction of large amounts of melt1, 2. Models to explain highly melt-depleted but garnet-bearing rock compositions require multi-stage processes with garnet and clinopyroxene possibly of secondary origin1, 3. Here we report on orogenic peridotites (fragments of cratonic mantle incorporated into the crust during continent-continent plate collision4) from Otr°y, western Norway. We show that the peridotites underwent extensive melting during upwelling from depths of 350 kilometres or more, forming a garnet-bearing cratonic root in a single melting event. These peridotites appear to be the residue after Archaean aluminium depleted komatiite magmatism.
URL: http://www.nature.com/nature/index.html
Subject Norway
archean orogenesis
peridotite massif
rocks geochemistry

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