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GEOREF RECORD

Ordovician magmatism, deformation, and exhumation in the Caledonides of central Norway; an orphan of the Taconic Orogeny?

Aaron S. Yoshinobu, Calvin G. Barnes, Oystein Nordgulen, Tore Prestvik, Mark Fanning and R. B. Pedersen
Ordovician magmatism, deformation, and exhumation in the Caledonides of central Norway; an orphan of the Taconic Orogeny?
Geology (Boulder) (October 2002) 30 (10): 883-886

Abstract

Magmatism, contractional deformation, and extension associated with the exhumation of high-pressure rocks in the Scandinavian Caledonides are commonly attributed to the Silurian-Devonian Scandian orogeny, in which eastward thrusting of allochthonous terranes over Baltica was followed by extensional collapse and exhumation. New fieldwork and U-Pb geochronology coupled with recent pressure-temperature estimates within the highest thrust sequence of the Caledonian orogen indicate that an earlier phase of west-directed contractional deformation was punctuated by migmatite-producing events and voluminous magmatism ca. 477-466 Ma and ca. 447 Ma, followed by exhumation in the Late Ordovician. Al-in-hornblende and GASP thermobarometry indicate that emplacement of a suite of 448-445 Ma plutons caused partial migmatization at pressures of 700-800 MPa. Subsequent isothermal exhumation to pressures of 400 MPa occurred while the host rocks were still partially molten. Rates of exhumation may have ranged from 2 to 11 mm.yr (super -1) or greater. These data provide evidence for a previously unrecognized phase of exhumation in the Caledonides and for aerially extensive west-vergent deformation. Deformation and magmatism associated with these events may be related to Taconic-age orogenesis near Laurentia, where the highest nappe sequences of the Scandinavian Caledonides probably resided during early Paleozoic time.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 30
Serial Issue: 10
Title: Ordovician magmatism, deformation, and exhumation in the Caledonides of central Norway; an orphan of the Taconic Orogeny?
Affiliation: Texas Tech University, Department of Geosciences, Lubbock, TX, United States
Pages: 883-886
Published: 200210
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 24
Accession Number: 2002-075304
Categories: Structural geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2002106
Illustration Description: illus. incl. sketch map
N65°00'00" - N65°45'00", E12°04'60" - E12°45'00"
Secondary Affiliation: Norwegian Geological Survey, NOR, NorwayNorwegian University of Science and Technology, NOR, NorwayAustralian National University, AUS, AustraliaUniversity of Bergen, NOR, Norway
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200223
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