Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)

Petrological study and pseudosection modelling have been carried out in high-grade orthogneisses of the southern domain of the Orlica- Snieznik Dome (NE Bohemian Massif). The studied samples are from an outcrop dominated by two deformation fabrics, a sub-horizontal S1 foliation defined by bands of r...

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Autores: Aguilar Gil, Carmen María, Chopin, Francis, Stípská, Pavla, Schulmann, Karel, Závada, Prokop, Racek, Martin, Martelat, Jean-Emmanuel, Pitra, Pavel
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2019
País:España
Institución:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
Repositorio:Recercat. Dipósit de la Recerca de Catalunya
OAI Identifier:oai:recercat.cat:2445/183375
Acceso en línea:https://hdl.handle.net/2445/183375
Access Level:acceso abierto
Palabra clave:Geologia estructural
Granit
Petrologia
Structural geology
Granite
Petrology
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dc.title.none.fl_str_mv Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
title Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
spellingShingle Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
Aguilar Gil, Carmen María
Geologia estructural
Granit
Petrologia
Structural geology
Granite
Petrology
title_short Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
title_full Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
title_fullStr Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
title_full_unstemmed Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
title_sort Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)
dc.creator.none.fl_str_mv Aguilar Gil, Carmen María
Chopin, Francis
Stípská, Pavla
Schulmann, Karel
Závada, Prokop
Racek, Martin
Martelat, Jean-Emmanuel
Pitra, Pavel
author Aguilar Gil, Carmen María
author_facet Aguilar Gil, Carmen María
Chopin, Francis
Stípská, Pavla
Schulmann, Karel
Závada, Prokop
Racek, Martin
Martelat, Jean-Emmanuel
Pitra, Pavel
author_role author
author2 Chopin, Francis
Stípská, Pavla
Schulmann, Karel
Závada, Prokop
Racek, Martin
Martelat, Jean-Emmanuel
Pitra, Pavel
author2_role author
author
author
author
author
author
author
dc.subject.none.fl_str_mv Geologia estructural
Granit
Petrologia
Structural geology
Granite
Petrology
topic Geologia estructural
Granit
Petrologia
Structural geology
Granite
Petrology
description Petrological study and pseudosection modelling have been carried out in high-grade orthogneisses of the southern domain of the Orlica- Snieznik Dome (NE Bohemian Massif). The studied samples are from an outcrop dominated by two deformation fabrics, a sub-horizontal S1 foliation defined by bands of recrystallized K-feldspar, quartz and plagioclase folded by centimetre- to several metre-scale close to isoclinal folds associated with development of a new subvertical N-S trending foliation S2. Based on field features and textural observations, a gradual transition from banded mylonitic orthogneiss (Type I) to stromatitic (Type II), schlieren (type III) and nebulitic (type IV) textures typical of migmatities can be distinguished. The banded orthogneiss is composed of almost monomineral recrystallized K-feldspar layers (2 to 10 mm thick) alternating with layers of plagioclase and quartz (1 to 4mm thick), parallel to the S1 limb and the axial planar S2 foliation. The stromatitic migmatite shows 1 to 4 mm thick layers with macroscopically diffuse boundaries between plagioclase, quartz and K-feldspar rich domains. Boundaries between quartz and feldspar layers are poorly defined and interlobed with adjacent minerals. The schlieren migmatite is almost isotropic preserving small K-feldspar-rich domains within a matrix characterized by random distribution of phases, whereas in the nebulitic migmatite the microstructure is completely isotropic characterized by random distribution of phases. The transition from the Type I to IV is characterized by increasing nucleation of interstitial phases along like-like grain boundaries, by a decrease of grain size of all phases and by progressive disintegration of recrystallized K-feldspar grains by embayments of fine-grained myrmekite. The mineral assemblage of all types consists of biotite, white micas, garnet, quartz, K-feldspar and plagioclase, and accessory apatite, ilmenite, zircon and monazite. In the mineral equilibria modelling, the core of garnet (alm0.58, py0.02-0.03, grs0.34, sps0.05) and phengite (Si = 3.38-3.20 p.f.u) is consistent with a P-T peak at 10-13 kbar and 720-750 C in the dominant grt-bt-ph-rt-qtz-pl-kfs mineral assemblage. The garnet rim (alm0.68, py0.02-0.03, grs0.11, sps0.21), white mica rim (Si = 3.10 p.f.u) together with unzoned biotite (XFe = 0.76-0.78) match the modelled isopleths in the middle-P part of the grt-bt-ph-ilm-qtz-pl-kfs field to reach the solidus at 78 kbar and 630650 C. In addition, the absence of prograde garnet zoning in the Type I to III suggests that the garnet was completely re-equilibrated during the retrograde history, whereas in the Type IV the HP garnet chemistry was preserved. This is discussed in frame of melt presence in different migmatite types along their P-T path. Based on mineral equilibria modelling it is argued for fluid/melt-fluxed melting at HP conditions and on exhumation. The migmatite textural types are a result of grain-scale melt migration process and not of a localized melt transport in dykes as known from metasediments.
publishDate 2019
dc.date.none.fl_str_mv 2019
2022
2022
2022
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv https://hdl.handle.net/2445/183375
url https://hdl.handle.net/2445/183375
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Reproducció del document publicat a: https://meetingorganizer.copernicus.org/EGU2019/EGU2019-18012-2.pdf
Geophysical Research Abstracts, 2019, vol. 21, num. EGU2019-18012
dc.rights.none.fl_str_mv cc-by (c) Aguilar Gil, Carmen et al., 2019
https://creativecommons.org/licenses/by/4.0/
info:eu-repo/semantics/openAccess
rights_invalid_str_mv cc-by (c) Aguilar Gil, Carmen et al., 2019
https://creativecommons.org/licenses/by/4.0/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv 1 p.
application/pdf
application/pdf
dc.publisher.none.fl_str_mv European Geosciences Union (EGU)
publisher.none.fl_str_mv European Geosciences Union (EGU)
dc.source.none.fl_str_mv Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)
reponame:Recercat. Dipósit de la Recerca de Catalunya
instname:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
instname_str Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)
reponame_str Recercat. Dipósit de la Recerca de Catalunya
collection Recercat. Dipósit de la Recerca de Catalunya
repository.name.fl_str_mv
repository.mail.fl_str_mv
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spelling Migmatite formation in a crustal-scale shear zone during continental subduction: an example from a high-pressure granitic orthogneiss from the Orlica-Śnieżnik Dome (NE Bohemian Massif)Aguilar Gil, Carmen MaríaChopin, FrancisStípská, PavlaSchulmann, KarelZávada, ProkopRacek, MartinMartelat, Jean-EmmanuelPitra, PavelGeologia estructuralGranitPetrologiaStructural geologyGranitePetrologyPetrological study and pseudosection modelling have been carried out in high-grade orthogneisses of the southern domain of the Orlica- Snieznik Dome (NE Bohemian Massif). The studied samples are from an outcrop dominated by two deformation fabrics, a sub-horizontal S1 foliation defined by bands of recrystallized K-feldspar, quartz and plagioclase folded by centimetre- to several metre-scale close to isoclinal folds associated with development of a new subvertical N-S trending foliation S2. Based on field features and textural observations, a gradual transition from banded mylonitic orthogneiss (Type I) to stromatitic (Type II), schlieren (type III) and nebulitic (type IV) textures typical of migmatities can be distinguished. The banded orthogneiss is composed of almost monomineral recrystallized K-feldspar layers (2 to 10 mm thick) alternating with layers of plagioclase and quartz (1 to 4mm thick), parallel to the S1 limb and the axial planar S2 foliation. The stromatitic migmatite shows 1 to 4 mm thick layers with macroscopically diffuse boundaries between plagioclase, quartz and K-feldspar rich domains. Boundaries between quartz and feldspar layers are poorly defined and interlobed with adjacent minerals. The schlieren migmatite is almost isotropic preserving small K-feldspar-rich domains within a matrix characterized by random distribution of phases, whereas in the nebulitic migmatite the microstructure is completely isotropic characterized by random distribution of phases. The transition from the Type I to IV is characterized by increasing nucleation of interstitial phases along like-like grain boundaries, by a decrease of grain size of all phases and by progressive disintegration of recrystallized K-feldspar grains by embayments of fine-grained myrmekite. The mineral assemblage of all types consists of biotite, white micas, garnet, quartz, K-feldspar and plagioclase, and accessory apatite, ilmenite, zircon and monazite. In the mineral equilibria modelling, the core of garnet (alm0.58, py0.02-0.03, grs0.34, sps0.05) and phengite (Si = 3.38-3.20 p.f.u) is consistent with a P-T peak at 10-13 kbar and 720-750 C in the dominant grt-bt-ph-rt-qtz-pl-kfs mineral assemblage. The garnet rim (alm0.68, py0.02-0.03, grs0.11, sps0.21), white mica rim (Si = 3.10 p.f.u) together with unzoned biotite (XFe = 0.76-0.78) match the modelled isopleths in the middle-P part of the grt-bt-ph-ilm-qtz-pl-kfs field to reach the solidus at 78 kbar and 630650 C. In addition, the absence of prograde garnet zoning in the Type I to III suggests that the garnet was completely re-equilibrated during the retrograde history, whereas in the Type IV the HP garnet chemistry was preserved. This is discussed in frame of melt presence in different migmatite types along their P-T path. Based on mineral equilibria modelling it is argued for fluid/melt-fluxed melting at HP conditions and on exhumation. The migmatite textural types are a result of grain-scale melt migration process and not of a localized melt transport in dykes as known from metasediments.European Geosciences Union (EGU)2022202220192022info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersion1 p.application/pdfapplication/pdfhttps://hdl.handle.net/2445/183375Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)reponame:Recercat. Dipósit de la Recerca de Catalunyainstname:Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya)InglésReproducció del document publicat a: https://meetingorganizer.copernicus.org/EGU2019/EGU2019-18012-2.pdfGeophysical Research Abstracts, 2019, vol. 21, num. EGU2019-18012cc-by (c) Aguilar Gil, Carmen et al., 2019https://creativecommons.org/licenses/by/4.0/info:eu-repo/semantics/openAccessoai:recercat.cat:2445/1833752026-05-29T05:05:01Z
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