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Exhumation of an eclogite terrane as a hot migmatitic nappe, Sveconorwegian orogen

Möller, Charlotte LU ; Andersson, Jenny; Brendan, Dyck LU and Lundin, Ildiko Antal (2015) In Lithos 226. p.147-168
Abstract
We demonstrate a case of eclogite exhumation in a partially molten, low-viscosity fold nappe within high-grade metamorphosed crust in the Eastern Segment of the Sveconorwegian orogen. The nappe formed during tectonic extrusion, melt-weakening assisted exhumation and foreland-directed translation of eclogitized crust, and stalled at 35-40 km depth within the collisional belt. The eclogites are structurally restricted to a regional recumbent fold in which stromatic orthogneiss with pods of amphibolitized eclogite make up the core. High-temperature mylonitic gneiss with remnants of kyanite eclogite (P > 15 kbar) composes a basal shear zone 50 km long and <4 km wide. Heterogeneously sheared and partly migmatized augen gneiss forms a... (More)
We demonstrate a case of eclogite exhumation in a partially molten, low-viscosity fold nappe within high-grade metamorphosed crust in the Eastern Segment of the Sveconorwegian orogen. The nappe formed during tectonic extrusion, melt-weakening assisted exhumation and foreland-directed translation of eclogitized crust, and stalled at 35-40 km depth within the collisional belt. The eclogites are structurally restricted to a regional recumbent fold in which stromatic orthogneiss with pods of amphibolitized eclogite make up the core. High-temperature mylonitic gneiss with remnants of kyanite eclogite (P > 15 kbar) composes a basal shear zone 50 km long and <4 km wide. Heterogeneously sheared and partly migmatized augen gneiss forms a tectonostratigraphic marker in front of and beneath the nappe, and is in turn structurally enveloped by a composite sequence of orthogneisses and metabasites. The entire tectonostratigraphic pile underwent near-pervasive deformation and recrystallization under high-pressure granulite and upper amphibolite conditions. U-Pb SIMS metamorphic zircon ages of eclogite and stromatic orthogneiss constrain the time of eclogitization at 988 +/- 6 Ma and 978 +/- 7 Ma. Migmatization, concomitant deformation, and exhumation are dated at 976 +/- 6 Ma, and crystallization of post-kinematic melt at 956 +/- 7 Ma. Orthogneiss protoliths are dated at 1733 +/- 11 and 1677 +/- 10 Ma (stromatic gneiss) and 1388 +/- 7 Ma (augen gneiss in footwall), demonstrating origins indigenous to the Eastern Segment. Eclogitization and exhumation were coeval with the Rigolet phase of the Grenvillian orogeny, reflecting the late stage of continental collision during construction of the supercontinent Rodinia. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Eclogite, Exhumation, Extrusion, Partial melting, Migmatite, Precambrian
in
Lithos
volume
226
pages
147 - 168
publisher
Elsevier
external identifiers
  • wos:000356207000011
  • scopus:84939417033
ISSN
0024-4937
DOI
10.1016/j.lithos.2014.12.013
language
English
LU publication?
yes
id
a96bb1dc-107c-4d31-8976-e71f6765331a (old id 7601781)
date added to LUP
2015-07-23 13:57:24
date last changed
2017-07-02 03:14:00
@article{a96bb1dc-107c-4d31-8976-e71f6765331a,
  abstract     = {We demonstrate a case of eclogite exhumation in a partially molten, low-viscosity fold nappe within high-grade metamorphosed crust in the Eastern Segment of the Sveconorwegian orogen. The nappe formed during tectonic extrusion, melt-weakening assisted exhumation and foreland-directed translation of eclogitized crust, and stalled at 35-40 km depth within the collisional belt. The eclogites are structurally restricted to a regional recumbent fold in which stromatic orthogneiss with pods of amphibolitized eclogite make up the core. High-temperature mylonitic gneiss with remnants of kyanite eclogite (P &gt; 15 kbar) composes a basal shear zone 50 km long and &lt;4 km wide. Heterogeneously sheared and partly migmatized augen gneiss forms a tectonostratigraphic marker in front of and beneath the nappe, and is in turn structurally enveloped by a composite sequence of orthogneisses and metabasites. The entire tectonostratigraphic pile underwent near-pervasive deformation and recrystallization under high-pressure granulite and upper amphibolite conditions. U-Pb SIMS metamorphic zircon ages of eclogite and stromatic orthogneiss constrain the time of eclogitization at 988 +/- 6 Ma and 978 +/- 7 Ma. Migmatization, concomitant deformation, and exhumation are dated at 976 +/- 6 Ma, and crystallization of post-kinematic melt at 956 +/- 7 Ma. Orthogneiss protoliths are dated at 1733 +/- 11 and 1677 +/- 10 Ma (stromatic gneiss) and 1388 +/- 7 Ma (augen gneiss in footwall), demonstrating origins indigenous to the Eastern Segment. Eclogitization and exhumation were coeval with the Rigolet phase of the Grenvillian orogeny, reflecting the late stage of continental collision during construction of the supercontinent Rodinia. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).},
  author       = {Möller, Charlotte and Andersson, Jenny and Brendan, Dyck and Lundin, Ildiko Antal},
  issn         = {0024-4937},
  keyword      = {Eclogite,Exhumation,Extrusion,Partial melting,Migmatite,Precambrian},
  language     = {eng},
  pages        = {147--168},
  publisher    = {Elsevier},
  series       = {Lithos},
  title        = {Exhumation of an eclogite terrane as a hot migmatitic nappe, Sveconorwegian orogen},
  url          = {http://dx.doi.org/10.1016/j.lithos.2014.12.013},
  volume       = {226},
  year         = {2015},
}