UHP metamorphism recorded by kyanite-bearing eclogite in the Seve Nappe Complex of northern Jämtland, Swedish Caledonides

Janák, Marian; Roermund, Herman van; Majka, Jarosław; Gee, David G.

doi:10.1016/j.gr.2012.06.012

Cited by 77 publications

(72 citation statements)

References 86 publications

(97 reference statements)

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“…During the last 4 years of preparation for the drilling, following the initial COSC workshop in 2010 (Lorenz et al, 2011), investigations of the Seve Nappe Complex in the Jämtland area have improved our understanding of the subduction systems that existed along the Baltoscandian margin during Ordovician closure of the Iapetus Ocean. Ultra-high-pressure metamorphism was recognized in both the lower and middle parts of the Seve Nappe Complex in northern Jämtland (Janák et al, 2013) and the Middle Ordovician age confirmed (Root and Corfu, 2012). In central Jämtland, both in the Åreskutan Nappe and 50 km farther west in the correlative Snashögarna Nappe Klonowska et al, 2015), microdiamonds were discovered in garnets of the "granulite facies" migmatitic gneisses.…”

Section: Scientific Objectivesmentioning

confidence: 96%

COSC-1 – drilling of a subduction-related allochthon in the Palaeozoic Caledonide orogen of Scandinavia

et al. 2015

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Abstract. The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project focuses on mountain building processes in a major mid-Palaeozoic orogen in western Scandinavia and its comparison with modern analogues. The project investigates the subduction-generated Seve Nape Complex. These in part under ultra-high-pressure conditions metamorphosed outer continental margin and continent-ocean transition zone assemblages were emplaced onto the Baltoscandian platform and there influenced the underlying allochthons and the basement. COSC-1 is the first of two ca. 2.5 km deep, fully cored drill holes located in the vicinity of the abandoned Fröå mine, close to the town of Åre in Jämtland, central Sweden. It sampled a thick section of the lower part of the Seve Complex and was planned to penetrate its basal thrust zone into the underlying lowergrade metamorphosed allochthon. The drill hole reached a depth of 2495.8 m and nearly 100 % core recovery was achieved. Although planning was based on existing geological mapping and new high-resolution seismic surveys, the drilling resulted in some surprises: the Lower Seve Nappe proved to be composed of rather homogenous gneisses, with only subordinate mafic bodies, and its basal thrust zone was unexpectedly thick (> 800 m). The drill hole did not penetrate the bottom of the thrust zone. However, lower-grade metasedimentary rocks were encountered in the lowermost part of the drill hole together with garnetiferous mylonites tens of metres thick. The tectonostratigraphic position is still unclear, and geological and geophysical interpretations are under revision. The compact gneisses host only eight fluid conducting zones of limited transmissivity between 300 m and total depth. Downhole measurements suggest an uncorrected average geothermal gradient of ∼ 20 • C km −1 . This paper summarizes the operations and preliminary results from COSC-1 (ICDP 5054-1-A), drilled from early May to late August 2014, and is complemented by a detailed operational report and the data repository.Published by Copernicus Publications on behalf of the IODP and the ICDP.

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Section: Scientific Objectivesmentioning

confidence: 96%

COSC-1 – drilling of a subduction-related allochthon in the Palaeozoic Caledonide orogen of Scandinavia

et al. 2015

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“…The Seve Nappe Complex (SNC) is a key allochthon for understanding the evolution of the Scandinavian Caledonides. Several recent studies of the Ordovician metamorphic rocks in the SNC in Jämtland have revealed higher pressures than previously known suggesting a deeper subduction of the Baltoscandian margin (Janák et al 2013, Klonowska et al 2014, Majka et al 2014a, b, Rosén 2014. Geochronological data indicate that the (ultra)-high pressure event occurred at c. 460 Ma (Brueckner & Van Roermund 2007).…”

mentioning

confidence: 93%

Age and metamorphic conditions of the Tjeliken garnet – phengite gneiss (Swedish Caledonides) [abstract]

Andersson

2015

geol

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“…A 30 cm thick, boudinaged dyke of garnet pyroxenite, locally containing the eclogitic Ky+Ph+Omp+Grt assemblage (Janák et al, 2013), is concordant with the main foliation of the body. All lithologies are well preserved, without any substantial weathering.…”

Section: Previous Investigations Of the Friningen Garnet Peridotitementioning

confidence: 88%

“…1) to determine the pre-Caledonian mantle conditions of the FGP, 2) to construct a definitive PTt-d path for the FGP and 3) to compare this PTt-d path with that of the associated metabasic rocks (Janák et al,2013). New results are obtained from thermodynamic modelling.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

The Friningen Garnet Peridotite (central Swedish Caledonides). A good example of the characteristic PTt path of a cold mantle wedge garnet peridotite

Gilio

Clos

Roermund

2015

Lithos

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UHP metamorphism recorded by kyanite-bearing eclogite in the Seve Nappe Complex of northern Jämtland, Swedish Caledonides

Cited by 77 publications

References 86 publications

COSC-1 – drilling of a subduction-related allochthon in the Palaeozoic Caledonide orogen of Scandinavia

COSC-1 – drilling of a subduction-related allochthon in the Palaeozoic Caledonide orogen of Scandinavia

Age and metamorphic conditions of the Tjeliken garnet – phengite gneiss (Swedish Caledonides) [abstract]

The Friningen Garnet Peridotite (central Swedish Caledonides). A good example of the characteristic PTt path of a cold mantle wedge garnet peridotite

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