scholarly journals The great eclogite debate of the Western Gneiss Region, Norwegian Caledonides: The in situ crustalv. exotic mantle origin controversy

2018 ◽  
Vol 36 (5) ◽  
pp. 517-527 ◽  
Author(s):  
Hannes K. Brueckner
Keyword(s):  
Western Gneiss Region ◽  
Mantle Origin ◽  
Norwegian Caledonides

Eclogites and eclogites in the Western Gneiss Region, Norwegian Caledonides

Lithos ◽  
2000 ◽  
Vol 52 (1-4) ◽  
pp. 165-195 ◽  
Author(s):  
S.J Cuthbert ◽  
D.A Carswell ◽  
E.J Krogh-Ravna ◽  
A Wain
Keyword(s):  
Western Gneiss Region ◽  
Norwegian Caledonides

In-situ laser ablation Lu–Hf geochronology of garnet across the Western Gneiss Region: Campaign-style dating of metamorphism

2021 ◽  
pp. jgs2021-094
Author(s):  
Renée Tamblyn ◽  
Martin Hand ◽  
Alexander Simpson ◽  
Sarah Gilbert ◽  
Ben Wade ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Ultrahigh Pressure ◽  
Western Gneiss Region ◽  
Content Type ◽  
Link Type ◽  
Geological Processes ◽  
History Of ◽  
Supplementary Material ◽  
Wilson Cycle

The development of in-situ laser ablation Lu–Hf geochronology of apatite, xenotime and garnet has opened avenues to quickly and directly date geological processes. We demonstrate the first use of campaign-style in-situ Lu–Hf geochronology of garnet across the high- to ultrahigh-pressure Western Gneiss Region in Norway. Mafic eclogites from this region have been the focus of much work, and were clearly formed during continental subduction during the Caledonian Orogen. However, abundant quartzofeldspathic and pelitic lithologies record a more complex history, with some preserving polymetamorphic age data, and most containing no indication of high-pressure mineral assemblages formed during subduction. Twenty metapelitic and felsic samples spanning 160 lateral kilometers across the Western Gneiss Region have been analysed using garnet Lu–Hf geochronology. The results reveal Caledonian ages for the majority of the garnets, suggesting some quartzofeldspathic and metapelitic lithologies were reactive and grew garnet during high- to ultrahigh-pressure metamorphism. However, two ultrahigh-pressure eclogite locations, Verpeneset and Fjørtoft, preserve both Caledonian and Neoproterozoic-aged garnets. Despite significant uncertainties on some of the Lu–Hf geochronologic ages, laser ablation Lu–Hf efficiently identifies the polymetamorphic history of parts of the Western Gneiss Region, illustrating the effectiveness of this novel analytical method for rapid mapping of metamorphic ages.Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/cc/caledonian-wilson-cycleSupplementary material:https://doi.org/10.6084/m9.figshare.c.5715453

The mantle and crustal evolution of two garnet peridotite suites from the Western Gneiss Region, Norwegian Caledonides: An isotopic investigation

Lithos ◽  
2010 ◽  
Vol 117 (1-4) ◽  
pp. 1-19 ◽  
Author(s):  
H.K. Brueckner ◽  
D.A. Carswell ◽  
W.L. Griffin ◽  
L.G. Medaris ◽  
H.L.M. Van Roermund ◽  
...  
Keyword(s):  
Garnet Peridotite ◽  
Crustal Evolution ◽  
Western Gneiss Region ◽  
Norwegian Caledonides ◽  
Isotopic Investigation

In-situ U-(Th-)Pb dating and REE analysis of zircon and monazite in the Grt-bearing gneisses from Gossa: Tracing early subduction into the highest-grade domains of the Western Gneiss Region, Norway

2021 ◽  
Author(s):  
Pauline Jeanneret ◽  
Katarzyna Walczak ◽  
Jarosław Majka ◽  
Michał Bukała ◽  
Simon Cuthbert ◽  
...  
Keyword(s):  
Metamorphic Overprint ◽  
Western Gneiss Region ◽  
Zircon Age ◽  
Multi Stage ◽  
Science Centre ◽  
Growth Features ◽  
Early Neoproterozoic

<p>To better understand the subduction–exhumation cycles of the Baltoscandian margin that reached (U)HP depths during the Caledonian orogeny, we have performed in-situ U-(Th-)Pb dating coupled with REE analysis of zircon and ± monazite in four samples from the supracrustal rocks of the Blåhø Nappe on Gossa island in the Western Gneiss Region (WGR) of Norway. We dated two garnet-plagioclase-biotite gneisses and two garnet-plagioclase-amphibole gneisses. Our research focused on deciphering the early metamorphic evolution of these complex rocks that have been overprinted by exhumation-related structures and pervasive retrogressive metamorphism.</p><p>The dated zircon grains are spherical or slightly elongated in shape, some of which display clear multi-stage growth features. Only one grain armored by garnet preserved an older detrital core that yielded early Neoproterozoic dates between 1.1-1.0 Ga. This grain does not provide any Caledonian signal. Younger individual <sup>20</sup><sup>6</sup>Pb/<sup>2</sup><sup>38</sup>U dates show three distinct populations that yield three concordia ages, each obtained from distinctly different compositional domains, the oldest from cores and the two youngest from overgrowths. The cores are characterized by HREE enrichment (high Lu/Gd ratios ca. 14.5), high Th/U ratios (> 0.1), and large Eu anomalies. They yield a concordia age of 474 ± 6.4 Ma. These cores can be rimmed by two different types of zircon overgrowth. The first overgrowth type (1) displays the same REE pattern as the cores and gives a concordia age of 444± 4.3 Ma. The second overgrowth type (2) shows a very weak Eu anomaly, no HREE enrichment (low Lu/Gd ratios ca. 2.37) and a very low Th/U ratios (<0.1). These yield a concordia age of 416± 3.7 Ma. The two older U–Pb zircon age populations are tentatively interpreted as reflecting two distinct metamorphic events or a prolonged episode of metamorphism. The youngest concordant metamorphic zircon dates a high grade, probably (U)HP, metamorphic overprint at ca. 416 Ma, subsequent to the previous events. Analyses performed on monazite provided complementary age records to those obtained on zircon. Monazite grains are weakly zoned, exhibit wormy shapes and are aligned with the youngest foliation. Th–U–total Pb dating of monazite, coupled with major and trace element mapping of monazite, yielded a very homogeneous age of 382 ± 1.6 Ma (n=65) interpreted to date the late shearing, which possibly accommodated a late stage of exhumation.</p><p>Funded by the National Science Centre (Poland) project no. 2014/14/E/ST10/00321.</p><p> </p>

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