Trace element signature and U–Pb geochronology of eclogite-facies zircon, Bergen Arcs, Caledonides of W Norway

Bingen, Bernard; Austrheim, Håkon; Whitehouse, Martin J.; Davis, W J

doi:10.1007/s00410-004-0585-z

Cited by 173 publications

(103 citation statements)

References 59 publications

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“…Newly grown or recrystallized zircon is recognized from Cl-brightness. Similar zircon CL patterns have been described from the Bergen Arcs eclogites, Norway (Bingen et al, 2004), which experienced a similar metamorphic history. The discordia upper intercept age of 958 ± 7 Ma (Fig.…”

Section: Age Of Granulite Facies Metamorphismsupporting

confidence: 76%

Diffusion versus recrystallization processes in Rb–Sr geochronology: Isotopic relics in eclogite facies rocks, Western Gneiss Region, Norway

Glodny

Kühn

Austrheim

2008

Geochimica et Cosmochimica Acta

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104

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Section: Age Of Granulite Facies Metamorphismsupporting

confidence: 76%

Diffusion versus recrystallization processes in Rb–Sr geochronology: Isotopic relics in eclogite facies rocks, Western Gneiss Region, Norway

Glodny

Kühn

Austrheim

2008

Geochimica et Cosmochimica Acta

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104

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“…They have manifold reasons, including isotopic inheritance (cf. Villa 2004 and references therein), incorporation of excess Ar into HP minerals (Scaillet 1998), persistence of zircon cores through metamorphism (Bingen et al 2004), limited isotopic homogenization during metamorphic mineral reactions (Thöni andJagoutz 1992, Romer andSiegesmund 2003), or incipient retrograde mineral reactions (Di Vincenzo and Palmeri 2001). Post-eclogite-facies exhumation of the Lindås nappe was accompanied by local amphibolite facies overprint of granulites and eclogites .…”

Section: Introductionmentioning

confidence: 99%

“…Numerous attempts have been made at isotopic dating of the eclogite metamorphism. Published 40 Ar- 39 Ar, Rb-Sr, Sm-Nd, and U-Pb based age results, employing various mineral systems, scatter between roughly 460 and 420 Ma (Cohen et al 1988, Bingen et al 2001, Bingen et al 2004Boundy et al , 1997b. Inconsistency between the existing age data appears to relate to isotopic disequilibria in and among minerals of some of the studied eclogites.…”

Section: Introductionmentioning

confidence: 99%

Geochronology of fluid-induced eclogite and amphibolite facies metamorphic reactions in a subduction–collision system, Bergen Arcs, Norway

Glodny

Kühn

Austrheim

2007

Contrib Mineral Petrol

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115

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Rb-Sr multimineral isochron data for metamorphic veins allow to date separate increments of the mineral reaction history of polymetamorphic terranes. Granulite facies rocks of the Lindås nappe, Bergen Arcs, Norway, were subducted and exhumed during the Caledonian orogeny. The rocks show petrographic evidence for two distinct events of local fluid infiltration and vein formation, along fractures and shear zones. The first occurred at eclogite facies (15-21 kbar, 650-750 °C) and a later one at amphibolite facies conditions (8-10 kbar, 600°C). The presence of fluids enabled local metamorphic equilibration only near fluid pathways. In fluid-absent domains, preexisting assemblages were metastably preserved. This resulted in a heterogeneity of metamorphic signatures on m-to µm-scales. Well-preserved granulite facies rocks preserve their Proterozoic Rb-Sr mineral ages, as does the U-Pb system of zircon in most lithologies. Six Rb/Sr multimineral isochron ages for eclogite facies veins and their immediate wallrocks date the fluid-induced eclogitization at 429.9 ± 3.5 Ma (2σ, weighted average, MSWD = 0.39). An eclogite facies vein has yield metamorphic zircon with concordant U-Pb ages of 429 ± 3 Ma, identical to the U-Pb age of 427.4 ± 0.9 Ma for zircon xenocrysts in an amphibolite facies vein. Seven Rb/Sr mineral isochron ages date amphibolite-facies fluid infiltration at 414.2 ± 2.8 Ma (MSWD = 1.5), an age value testifying to residence of the rocks in the deep orogenic crust at temperatures >600°C for nearly 15 Ma. The new data show that Rb-Sr mineral isochron ages effectively date fluid-induced (re)crystallization events rather than stages of cooling. The direct link between isotopic ages and distinct petrographic equilibrium assemblages aids to constrain the evolution of rocks in the P-T-reaction-time space, which is essential for understanding exhumation histories and the internal dynamics of orogens in general.

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“…2). The final stage of this orogeny-called the Scandian Orogeny-included the following: i) closure of the Iapetus ocean and emplacement of allochthons onto Baltica from~430 to 410 Ma (Tucker et al, 2004;Hacker and Gans, 2005); ii) Baltica-Laurentia collision and westward subduction of the Baltica basement and portions of the allochthons to ultrahighpressure depths from~425 to 400 Ma (Andersen et al, 1991;Andersen, 1998;Bingen et al, 2004;Root et al, 2004;Terry and Robinson, 2004;Root et al, 2005;Kylander-Clark et al, 2007;Kylander-Clark et al, 2008); and iii) exhumation to shallow crustal levels from~400 to~385 Ma (Andersen, 1998;Terry et al, 2000a;Tucker et al, 2004;Walsh et al, 2007). The WGC is locally imbricated with Caledonian nappe units-as suggested by the presence of a structurally lower gneiss-quartzite unit (Gee, 1980;Krill, 1980) in the northeastern part of the study area (Storli thrust of Tucker et al, 2004) (Fig.…”

Section: The Western Gneiss Regionmentioning

confidence: 99%

Ultra High Pressure Metamorphism☆

Massonne

2016

Reference Module in Earth Systems and Environmental Sciences

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A new dataset for the high-pressure to ultrahigh-pressure Western Gneiss Region allows the definition of distinct structural and petrological domains. Much of the study area is an E-dipping homocline with E-plunging lineations that exposes progressively deeper, more strongly deformed, more eclogite-rich structural levels westward. Although eclogites crop out across the WGR, Scandian deformation is weak and earlier structures are well preserved in the southeastern half of the study area. The Scandian reworking increases westward, culminating in strong Scandian fabrics with only isolated pockets of older structures; the dominant Scandian deformation was coaxial E-W stretching. The sinistrally sheared Møre-Trøndelag Fault Complex and Nordfjord Mylonitic Shear Zone bound these rocks to the north and south. There was moderate top-E, amphibolite-facies deformation associated with translation of the allochthons over the basement along its eastern edge, and the Nordfjord-Sogn Detachment Zone underwent strong lower amphibolite-facies to greenschist-facies top-W shearing. A northwestward increase in exhumation-related melting is indicated by leucosomes with hornblende, plagioclase, and Scandian sphene. In the western 2/3 of the study area, exhumation-related, amphibolite-facies symplectite formation in quartzofeldspathic gneiss postdated most Scandian deformation; further deformation was restricted to slip along biotite-rich foliation planes and minor local folding. That the Western Gneiss Region quartzofeldspathic gneiss exhibits a strong gradient in degree of deformation, implies that continental crust in general need not undergo pervasive deformation during subduction.

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Trace element signature and U–Pb geochronology of eclogite-facies zircon, Bergen Arcs, Caledonides of W Norway

Cited by 173 publications

References 59 publications

Diffusion versus recrystallization processes in Rb–Sr geochronology: Isotopic relics in eclogite facies rocks, Western Gneiss Region, Norway

Diffusion versus recrystallization processes in Rb–Sr geochronology: Isotopic relics in eclogite facies rocks, Western Gneiss Region, Norway

Geochronology of fluid-induced eclogite and amphibolite facies metamorphic reactions in a subduction–collision system, Bergen Arcs, Norway

Ultra High Pressure Metamorphism☆

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