Fabric development during exhumation from ultrahigh-pressure in an eclogite-bearing shear zone, Western Gneiss Region, Norway

Renedo, Roxanne; Nachlas, William O.; Whitney, Donna L.; Teyssier, Christian; Piazolo, Sandra; Gordon, Stacia M.; Fossen, Haakon

doi:10.1016/j.jsg.2014.09.012

Cited by 23 publications

(16 citation statements)

References 48 publications

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“…Eclogite foliation and lineation during this stage reflect ductile rock's flow planes and directions [ Ábalos et al, ; Kurz et al, ; Neufeld et al, ; Keppler et al, ]. These exhibit a directional consistency at a regional scale in rocks of similar metamorphic grade in spite of their different lithology, and we interpret it reflects the frozen tectonic transport direction based upon the same grounds other authors have done so considering low‐T eclogite petrofabrics [ Davis and Whitney , ; Whitney et al, ; Renedo et al, ].…”

Section: Discussionsupporting

confidence: 57%

Eclogite inclusions from subducted metaigneous continental crust (Malpica‐Tui Allochthonous Complex, NW Spain): Petrofabric, geochronology, and calculated seismic properties

et al. 2017

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This study describes the strain geometry, crystal‐plastic deformational features, isotopic age of metamorphism, and calculated seismic properties of two medium‐temperature eclogite types from the Malpica‐Tui Allochthonous Complex of Variscan NW Iberia. The eclogite types are eclogites with coronitic garnets and eclogites with a planolinear fabric. Both of them were buried, deformed and recrystallized under maximum pressure and temperature of 2.6 GPa and 610–640°C, and subsequently exhumed in a late Devonian subduction channel. The metamorphic peak of the subduction‐exhumation cycle occurred ~375 Ma ago. Omphacite petrofabric ties eclogites with coronitic garnet to noncoaxial constrictional strain and eclogites with planolinear fabrics to noncoaxial flattening strain and stretching along the lineation. We also used omphacite crystallographic preferred orientations to calculate and constrain the seismic properties of the eclogites. The slight variations in petrophysical properties observed are interpreted to result from variations in the strain regime recorded by pristine eclogites, or from variations in the modal proportions of the constituent high‐pressure minerals. We foresee that eclogite in subduction metamorphic complexes might be either seismically undetectable or detected as planar features with high impedance contrasts relative to their host rocks.

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Section: Discussionsupporting

confidence: 57%

Eclogite inclusions from subducted metaigneous continental crust (Malpica‐Tui Allochthonous Complex, NW Spain): Petrofabric, geochronology, and calculated seismic properties

et al. 2017

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“…LS‐ to L‐type fabrics, documented from the Western Gneiss Region (Norway) by Renedo et al . (), have also been interpreted as recording the early stages of exhumation. Neufeld et al .…”

Section: Discussionmentioning

confidence: 99%

“…A key to understanding the mechanics of subduction (oceanic and continental) and the exhumation of (U)HP rocks is the microstructural analysis of mineral fabrics (clinopyroxene and amphibole) which can provide information about deformation regime (constriction, plane strain or flattening) and intensity of deformation (e.g. Mauler et al ., ; Kurz et al ., ; Kurz, ; Renedo et al ., ; Soldner et al ., ). These data can be interpreted in terms of the degree of mechanical coupling between the upper and lower plate during subduction and character of flow in subduction channels (Gerya et al ., ; Warren et al ., ; Agard et al ., ).…”

Section: Introductionmentioning

confidence: 98%

Dynamics of Saxothuringian subduction channel/wedge constrained by phase‐equilibria modelling and micro‐fabric analysis

Collett

Štípská

Kusbach

et al. 2016

Journal Metamorphic Geology

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“…Strain patterns consistent with transtensional exhumation (e.g., constrictional strain, lineation-parallel upright folds) developed under amphibolite-facies conditions during the final stages of WGR exhumation (Krabbendam and Dewey, 1998;Dewey and Strachan, 2003;Fossen et al, 2013), but the switch from transpression to transtension may have occurred even earlier, potentially at (U)HP conditions (Renedo et al, 2015). Previous work (Fossen and Dunlap, 1998) suggests that the switch occurred around 405 Ma, assuming that it is recorded by the kinematic switch form thrusting to back-sliding (eduction) of the overlying orogenic wedge represented by the Jotun Nappe.…”

Section: Comparison Of the Southern To The Northern Wgrmentioning

confidence: 99%

Geochronology and geochemistry of zircon from the northern Western Gneiss Region: Insights into the Caledonian tectonic history of western Norway

Gordon

Teyssier

Fossen

et al. 2016

Lithos

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The Western Gneiss Region (WGR) of Norway is divided by the Møre-Trøndelag shear zone (MTSZ) into a southern region that contains domains of Caledonian ultrahigh-pressure (UHP) metamorphic rocks (>2.5 GPa) and a northern area of similar Caledonian-aged rocks that record a maximum pressure reported thus far of ~ 1.5 GPa. Although both regions contain similar lithologies (primarily migmatitic quartzofeldspathic gneiss containing mafic lenses) and structural relationship of basement rocks to infolded nappes, this difference in maximum pressure implies a difference in tectonic history (continental subduction south of the shear zone, none to the north) and raises questions about the role of the MTSZ in the metamorphic history (including exhumation) of the WGR. Previous geochronology results indicated a difference in timing of peak metamorphism (older in north, younger in south). In order to better understand the tectonic history of the northern WGR and the MTSZ, and in particular the late-to post-Caledonian tectonic history, U-Pb zircon geochronology and trace-element abundances were obtained using the split-stream, laser-ablation ICPMS technique from metabasaltic lenses and migmatitic quartzofeldspathic host rocks from the structurally lowest exposed region of the northern WGR (Roan Peninsula basement), as well as leucosomes from an intercalated portion of the Seve Nappe Complex and a pegmatite in the MTSZ. Zircon from Roan gneiss and metabasite yield metamorphic ages of ca. 410-406 Ma, and zircon from a variety of migmatite samples (foliation-parallel leucosome to dikes) indicate melt crystallization at ca. 410 to 405 Ma. The Seve Nappe leucosomes yield only early Caledonian dates that cluster at ca. 437 Ma and ca. 465 Ma, suggesting that the allochthons in this region did not experience (or record) the same Scandian tectonic history as the basement rocks. Zircon from a weakly deformed pegmatite dike within the MTSZ crystallized at ca. 404 Ma, indicating that this shear zone was active during the 3 end-stages of high-grade metamorphism in both the southern and northern WGR domains. Results of this study show that the northern and southern WGR experienced a coeval Scandian metamorphic, magmatic and deformation history, despite a possible difference in maximum P-T conditions.

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Fabric development during exhumation from ultrahigh-pressure in an eclogite-bearing shear zone, Western Gneiss Region, Norway

Cited by 23 publications

References 48 publications

Eclogite inclusions from subducted metaigneous continental crust (Malpica‐Tui Allochthonous Complex, NW Spain): Petrofabric, geochronology, and calculated seismic properties

Eclogite inclusions from subducted metaigneous continental crust (Malpica‐Tui Allochthonous Complex, NW Spain): Petrofabric, geochronology, and calculated seismic properties

Dynamics of Saxothuringian subduction channel/wedge constrained by phase‐equilibria modelling and micro‐fabric analysis

Geochronology and geochemistry of zircon from the northern Western Gneiss Region: Insights into the Caledonian tectonic history of western Norway

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