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Sinking intrusion model for the emplacement of garnet-bearing peridotites into continent collision orogens

Hannes K. Brueckner
Sinking intrusion model for the emplacement of garnet-bearing peridotites into continent collision orogens
Geology (Boulder) (July 1998) 26 (7): 631-634

Abstract

Garnet- (and probably spinel-) bearing ultramafic rocks that form tectonic lenses within high-metamorphic-grade gneisses in mountain core zones may intrude by moving downward or laterally into deeply subducted continental crust from the overlying mantle wedge. This model is most credible for garnet peridotites associated with ultrahigh-pressure metamorphic terranes in mountains formed by continent-continent collision. The extremely high pressures implied by ultrahigh-pressure metamorphism indicate that continental crust was subducted to mantle depths >100-120 km, where the mantle is in the garnet peridotite facies. Exchange between mantle and crust seems likely, particularly the transfer of mantle from the hanging wall into the crustal footwall. The mantle wedge overlying the subducted crustal terrane creates a denser over lighter configuration that is gravitationally unstable. If the interface becomes hot or wet enough so that peridotite can deform by ductile flow, it would sink as mantle blobs into the underlying crustal rocks. If not, the exchange presumably occurs through a brittle mechanism. The intruded bodies will be transported to the surface passively as the host crustal terrane is exhumed buoyantly toward the surface. This mechanism is proposed in particular to explain the intrusion of garnetiferous peridotites in the ultrahigh-pressure Western Gneiss region of the Norwegian Caledonides during the Caledonian orogeny.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 26
Serial Issue: 7
Title: Sinking intrusion model for the emplacement of garnet-bearing peridotites into continent collision orogens
Affiliation: City University of New York, Queens College, New York, NY, United States
Pages: 631-634
Published: 199807
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 32
Accession Number: 1998-044257
Categories: Igneous and metamorphic petrologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Lamont-Doherty Earth Obs., Contrib. No. 5800
Illustration Description: illus. incl. sketch map
N62°00'00" - N62°19'60", E06°30'00" - E07°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 199817
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