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Garnet amphibolite in the internal Eastern Segment, Sveconorwegian Province : monitors of metamorphic recrystallization at high temperature and pressure during Sveconorwegian orogeny

Hernnäs, Tove LU (2018) In Dissertations in Geology at Lund University GEOR02 20181
Department of Geology
Abstract
The analyzed area exposes a deep underthrusting lower plate of the Sveconorwegian orogen and facilitates studying of an elsewhere hidden portion of the Earth. Petrographic and structural studies of different metamorphic rock types within the southern Eastern Segment, Sveconorwegian Province, Sweden, were carried out to better understand the regional metamorphism and deformation history. The analyzed rock types are migmatitic garnet amphibolite, migmatitic garnet poor amphibolite, quartz feldspar rich gneisses and metagranites, leucocratic granitic gneiss and coronitic metagabbro.
Analyzed microtextures within the metagabbroic rock include coronitic textures. Such textures reveal the metamorphic history of the rocks and implies solid-state... (More)
The analyzed area exposes a deep underthrusting lower plate of the Sveconorwegian orogen and facilitates studying of an elsewhere hidden portion of the Earth. Petrographic and structural studies of different metamorphic rock types within the southern Eastern Segment, Sveconorwegian Province, Sweden, were carried out to better understand the regional metamorphism and deformation history. The analyzed rock types are migmatitic garnet amphibolite, migmatitic garnet poor amphibolite, quartz feldspar rich gneisses and metagranites, leucocratic granitic gneiss and coronitic metagabbro.
Analyzed microtextures within the metagabbroic rock include coronitic textures. Such textures reveal the metamorphic history of the rocks and implies solid-state reactions forming such prominent coronites. Furthermore, penetrative coronitic texture together with a preserved igneous texture in metagabbroic rocks is an indicator of high-grade metamorphism in dry conditions, reaching granulite facies. Previous studies imply that the coronitic metagabbro and the migmatitic garnet amphibolite have an identical protholith, and that such can be traced throughout the Eastern Segment. The relict igneous texture of the coronitic metagabbro confirms dry conditions within the rock complex. Fluids did not percolate the system and the reactions where therefore inhibited and did not run to completion.
Additionally, a regional scale fold within the garnet amphibolite, with the coronitic metagabbro located in the hinge zone, is suggested to cause a lack of fluid percolation due to deformational differences. Differences in deformation and metamorphism may be affected by folding as the hinge zone can be less deformed than the limbs of the fold. Conclusively, the coronitic metagabbro with its peculiar texture has been of substantial importance to monitor the metamorphic conditions and recrystallization processes. It supports previous studies within the region, that the rocks experienced high-grade metamorphism and deformation. (Less)
Abstract (Swedish)
Det undersökta området blottar en djupare del av den underskjutande undre kontinentalplattan som är en del av den Svekonorvegiska orogenesen och möjliggör studier av en normalt dold del av en orogenes. Petrografi- och strukturstudier av metamorfa bergarter inom den södra delen av det Östra Segmentet, Svekonorvegiska provinsen, Sverige, genomfördes för att bättre förstå den regionala metamorfosen och tidigare deformationer. Undersökta bergarter inkluderar migmatitisk granatamfibolit, migmatitisk granatfattig amfibolit, kvarts-, feldspatrika gnejser och metagraniter, leukokratiska granitiska gnejser och koronitisk metagabbro.
Analyserade mikrotekturer inom den metagabbroida bergarten innefattar koronitiska texturer. Sådana texturer avslöjar... (More)
Det undersökta området blottar en djupare del av den underskjutande undre kontinentalplattan som är en del av den Svekonorvegiska orogenesen och möjliggör studier av en normalt dold del av en orogenes. Petrografi- och strukturstudier av metamorfa bergarter inom den södra delen av det Östra Segmentet, Svekonorvegiska provinsen, Sverige, genomfördes för att bättre förstå den regionala metamorfosen och tidigare deformationer. Undersökta bergarter inkluderar migmatitisk granatamfibolit, migmatitisk granatfattig amfibolit, kvarts-, feldspatrika gnejser och metagraniter, leukokratiska granitiska gnejser och koronitisk metagabbro.
Analyserade mikrotekturer inom den metagabbroida bergarten innefattar koronitiska texturer. Sådana texturer avslöjar berggrundens metamorfa historia och antyder på förening i fast fas. Genomgående koronitiska texturer tillsammans med en bevarad vulkanisk textur i metagabbroida bergarter är en indikator på en hög metamorf grad i torra förhållanden som uppnått granulit facies. Tidigare studier visar på att den koronitiska metagabbron och den migmatitiska granatamfiboliten har en gemensam protolit och att denna kan spåras över hela det Östra Segmentet. Den bevarade vulkaniska texturen i den koronitiska metagabbron är ett bevis på torra förhållanden inom berggrunds komplexet eftersom fluider inte perkolerade och reaktionerna avstannade.
Ett regionalt veck i granatamfiboliten, där den koronitiska metagabbron är belägen i veckzonen kan tyda på att fluider inte kunnat tränga in och veckstrukturen har därför i sin tur påverkat berggrunden olika. Ett veck är både komprimerat och utsträckt i veckzonen och detta kan leda till förändringar i fluider som sedan har stor inverkan vid metamorfos. Den särskilda texturen hos den koronitisk metagabbron har varit en betydande faktor för att förstå de metamorfa förhållandena som påverkat området. Studien styrker tidigare forskning i området och visar på att berg-grunden påverkats av höggradig metamorfos och deformation. (Less)
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author
Hernnäs, Tove LU
supervisor
organization
course
GEOR02 20181
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Sveconorwegian, metamorphic petrology, mapping, coronitic metagabbro, microtextures, Eastern Segment
publication/series
Dissertations in Geology at Lund University
report number
553
language
English
id
8964900
date added to LUP
2019-01-07 09:58:19
date last changed
2019-01-07 09:58:19
@misc{8964900,
  abstract     = {The analyzed area exposes a deep underthrusting lower plate of the Sveconorwegian orogen and facilitates studying of an elsewhere hidden portion of the Earth. Petrographic and structural studies of different metamorphic rock types within the southern Eastern Segment, Sveconorwegian Province, Sweden, were carried out to better understand the regional metamorphism and deformation history. The analyzed rock types are migmatitic garnet amphibolite, migmatitic garnet poor amphibolite, quartz feldspar rich gneisses and metagranites, leucocratic granitic gneiss and coronitic metagabbro.
Analyzed microtextures within the metagabbroic rock include coronitic textures. Such textures reveal the metamorphic history of the rocks and implies solid-state reactions forming such prominent coronites. Furthermore, penetrative coronitic texture together with a preserved igneous texture in metagabbroic rocks is an indicator of high-grade metamorphism in dry conditions, reaching granulite facies. Previous studies imply that the coronitic metagabbro and the migmatitic garnet amphibolite have an identical protholith, and that such can be traced throughout the Eastern Segment. The relict igneous texture of the coronitic metagabbro confirms dry conditions within the rock complex. Fluids did not percolate the system and the reactions where therefore inhibited and did not run to completion.
Additionally, a regional scale fold within the garnet amphibolite, with the coronitic metagabbro located in the hinge zone, is suggested to cause a lack of fluid percolation due to deformational differences. Differences in deformation and metamorphism may be affected by folding as the hinge zone can be less deformed than the limbs of the fold. Conclusively, the coronitic metagabbro with its peculiar texture has been of substantial importance to monitor the metamorphic conditions and recrystallization processes. It supports previous studies within the region, that the rocks experienced high-grade metamorphism and deformation.},
  author       = {Hernnäs, Tove},
  keyword      = {Sveconorwegian,metamorphic petrology,mapping,coronitic metagabbro,microtextures,Eastern Segment},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {Garnet amphibolite in the internal Eastern Segment, Sveconorwegian Province : monitors of metamorphic recrystallization at high temperature and pressure during Sveconorwegian orogeny},
  year         = {2018},
}