Abstract
A metamorphic core complex in Northwest Payer Land, East Greenland Caledonides
Abstracts with programs - Geological Society of America, Vol.31(7), p.370
Geological Society of America, 1999 annual meeting
1999
Abstract
A regional HP granulite facies gneiss complex occurs in northwest Payer Land (74 degrees 28'-74 degrees 47'N, 22 degrees 30'-23 degrees 40) in the central part of the East Greenland Caledonides. The main lithologies are granitic orthogneisses, aluminous paragneisses, and metabasites. The mafic rocks are present as dikes swarms, massive coronitic metagabbros, small pods, and larger mappable units. Rare ultramafic pods contain the diagnostic HP assemblage garnet + olivine + clinopyroxene + orthopyroxene + amphibole + spinel; mafic rocks contain well-equilibrated garnet + clinopyroxene + amphibole + quartz + rutile + or - plagioclase, and granitic orthogneisses contain orthopyroxene + garnet + perthite. Peak pressure estimated from anorthite (in plagioclase) = grossular (in garnet) + kyanite + quartz in coronitic metagabbros is 1.5-1.6 GPa, while peak temperature from garnet-clinopyroxene thermometry is approx. 850 degrees C. SHRIMP U-Pb dating of zircons from a granitic granulite yields 207Pb/206Pb ages of 2.6-2.85 Ga on igneous cores, and a weighted mean 207Pb/206Pb age of 1871+ or -49 Ma on clean metamorphic rims. In the southern part of the area, low-grade metasedimentary rocks of the Neoproterozoic Eleonore Bay Supergroup are separated from the underlying gneiss complex by a 1500 m thick mylonite zone. The intensity of deformation increases towards the fault, while the metamorphic grade of the tectonites decreases from amphibolite to greenschist facies upwards in the footwall. A 2-3 m thick zone of cataclasite is found at the contact between the two units. The mylonitic foliation dips shallowly to the SE, lineations plunge shallowly to the NE and SW, and displacement sense is top-to-the-southwest. The Payer Land deformation zone is interpreted as a Late Caledonian extensional detachment that exhumes a Precambrian HP granulite facies core complex. The Payer Land gneisses do not appear to be extensively reworked by Caledonian deformation and metamorphism. The Payer Land deformation zone is one of a number of extensional detachments now recognized in the central East Greenland Caledonides, but the preservation and exhumation of HP granulites is unique.
Details
- Title: Subtitle
- A metamorphic core complex in Northwest Payer Land, East Greenland Caledonides
- Creators
- Jane A Gilotti - University of IowaSynnove ElvevoldKristine Thrane
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.31(7), p.370
- Conference
- Geological Society of America, 1999 annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 1999 annual meeting
- Language
- English
- Date published
- 1999
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240791502771
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