Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway
The Lofoten Islands in northern Norway represent the lower crust in the Baltica- Laurentia collision during the Caledonian Orogeny -460 Ma. The island of Flakstadoy consists o f -1.8 Ga granulite-facies gneisses and AMCG units cut by discrete Caledonian shear zones, some containing pseudotachylite v...
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San Francisco State University
2012
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ftcalifstateuniv:oai:scholarworks:mg74qn69b 2024-09-30T14:38:18+00:00 Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway Deborah Joy Shulman Mary Leech Karen Grove Christopher Gerbi 2012 http://hdl.handle.net/10211.3/125564 English eng San Francisco State University Science & Engineering Geosciences http://hdl.handle.net/10211.3/125564 Copyright by Deborah Joy Shulman, 2012 AS36 2012 GEOL .S58 Masters Thesis 2012 ftcalifstateuniv 2024-09-10T17:06:15Z The Lofoten Islands in northern Norway represent the lower crust in the Baltica- Laurentia collision during the Caledonian Orogeny -460 Ma. The island of Flakstadoy consists o f -1.8 Ga granulite-facies gneisses and AMCG units cut by discrete Caledonian shear zones, some containing pseudotachylite veins. A combination of petrography, mineral chemistry, and electron backscatter diffraction analyses show a spatial relationship between pseudotachylite formation, shear zone development, fluid infiltration, and metamorphism. Microfractures and backscatter imaging indicate that pseudotachylite-forming processes seismically shattered the rocks, reducing grain sizes and opening fluid pathways. Evidence of eclogite-facies metamorphism in omphacite and/or albite-diopside symplectite is found exclusively in the shear zones. A strong amphibolite-facies overprint in the shear zones replaced eclogite with amphibolite; a strong alignment of amphibole 0 0 1 parallel to the shear zone fabric indicates fluid availability during shearing. A lack of amphibole growth in the host rock indicates they remained effectively dry. I propose that co-seismic pseudotachylite formation opened fluid pathways in an otherwise effectively dry, impermeable granulitic crust. The advection of fluids led to localized strain and eclogite-facies metamorphism in otherwise metastable granulites. Permeability was maintained through localized strain during exhumation leading to a nearly complete amphibolite-facies overprint in the shear zones. Master Thesis Lofoten Northern Norway Scholarworks from California State University Lofoten Norway Flakstadøy ENVELOPE(13.299,13.299,68.067,68.067) |
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Scholarworks from California State University |
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English |
description |
The Lofoten Islands in northern Norway represent the lower crust in the Baltica- Laurentia collision during the Caledonian Orogeny -460 Ma. The island of Flakstadoy consists o f -1.8 Ga granulite-facies gneisses and AMCG units cut by discrete Caledonian shear zones, some containing pseudotachylite veins. A combination of petrography, mineral chemistry, and electron backscatter diffraction analyses show a spatial relationship between pseudotachylite formation, shear zone development, fluid infiltration, and metamorphism. Microfractures and backscatter imaging indicate that pseudotachylite-forming processes seismically shattered the rocks, reducing grain sizes and opening fluid pathways. Evidence of eclogite-facies metamorphism in omphacite and/or albite-diopside symplectite is found exclusively in the shear zones. A strong amphibolite-facies overprint in the shear zones replaced eclogite with amphibolite; a strong alignment of amphibole 0 0 1 parallel to the shear zone fabric indicates fluid availability during shearing. A lack of amphibole growth in the host rock indicates they remained effectively dry. I propose that co-seismic pseudotachylite formation opened fluid pathways in an otherwise effectively dry, impermeable granulitic crust. The advection of fluids led to localized strain and eclogite-facies metamorphism in otherwise metastable granulites. Permeability was maintained through localized strain during exhumation leading to a nearly complete amphibolite-facies overprint in the shear zones. |
author2 |
Mary Leech Karen Grove Christopher Gerbi |
format |
Master Thesis |
author |
Deborah Joy Shulman |
spellingShingle |
Deborah Joy Shulman Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway |
author_facet |
Deborah Joy Shulman |
author_sort |
Deborah Joy Shulman |
title |
Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway |
title_short |
Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway |
title_full |
Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway |
title_fullStr |
Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway |
title_full_unstemmed |
Fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, Flakstadøy, northern Norway |
title_sort |
fluid controlled metamorphism of eclogitic pseudotachylite-bearing shear zones, flakstadøy, northern norway |
publisher |
San Francisco State University |
publishDate |
2012 |
url |
http://hdl.handle.net/10211.3/125564 |
long_lat |
ENVELOPE(13.299,13.299,68.067,68.067) |
geographic |
Lofoten Norway Flakstadøy |
geographic_facet |
Lofoten Norway Flakstadøy |
genre |
Lofoten Northern Norway |
genre_facet |
Lofoten Northern Norway |
op_source |
AS36 2012 GEOL .S58 |
op_relation |
http://hdl.handle.net/10211.3/125564 |
op_rights |
Copyright by Deborah Joy Shulman, 2012 |
_version_ |
1811640985943277568 |