Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides
Strain in the lithosphere localises into weakened regions known as shear zones, which are often sites of repeated reactivation, reworking and poly-metamorphism. Mature shear zones are composite areas that include spatially and temporally heterogeneous combinations of coaxial and non-coaxial deformat...
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ftunidurhamethes:oai:etheses.dur.ac.uk:14299 2023-05-15T16:30:23+02:00 Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides ARMITAGE, TIMOTHY,BRENDAN 2021 application/pdf application/vnd.ms-excel http://etheses.dur.ac.uk/14299/ http://etheses.dur.ac.uk/14299/1/TimothyArmitage_CorrectedThesis.pdf http://etheses.dur.ac.uk/14299/2/Armitage000720772_AppendicesA.xlsx http://etheses.dur.ac.uk/14299/3/Armitage000720772_AppendicesB.xlsx unknown oai:etheses.dur.ac.uk:14299 http://etheses.dur.ac.uk/14299/1/TimothyArmitage_CorrectedThesis.pdf http://etheses.dur.ac.uk/14299/2/Armitage000720772_AppendicesA.xlsx http://etheses.dur.ac.uk/14299/3/Armitage000720772_AppendicesB.xlsx http://etheses.dur.ac.uk/14299/ Structural Geology Fault zones Shear Zones Transpression Transtension Ductile Deformation Field Geology Microstructures Geochronology Shetland Caledonian Scotland Thesis NonPeerReviewed 2021 ftunidurhamethes 2022-09-23T14:17:44Z Strain in the lithosphere localises into weakened regions known as shear zones, which are often sites of repeated reactivation, reworking and poly-metamorphism. Mature shear zones are composite areas that include spatially and temporally heterogeneous combinations of coaxial and non-coaxial deformation, such as transpression and transtension. Due to their heterogeneous nature, determining the structural evolution and regional significance of shear zones is challenging. Such areas of ductile deformation are associated with the SE-dipping North Roe Nappe and the N-S striking Walls Boundary Fault (WBF) on NW Mainland Shetland. Here, the metamorphic basement and bounding strike-slip WBF provide pre-Permian geological links between the Scottish, Norwegian and Greenland sectors of the Caledonian orogen. Field mapping, microstructural characterisation and Rb-Sr geochronology in combination with other published work in the area show that NW Mainland Shetland was subject to Neoarchaean (c. 2800 – 2700 Ma), Neoproterozoic (827 Ma – 697 Ma) and Caledonian (487 – 404 Ma) deformation. Weakly-defined Neoarchaean deformation is preserved in the structurally lowest sections of the Uyea Gneiss Complex below the North Roe Nappe. Within the North Roe Nappe, Neoproterozoic deformation is mainly found in coaxially-deformed decimetre-scale horizons. The main ductile fabrics found on NW Mainland Shetland formed during top-to-the NW thrusting and top-to-the N/sinistral shearing, dated to be broadly Caledonian in age. Bounding the coaxially-deformed Neoproterozoic horizons are decimetre-scale horizons of non-coaxial top-to-the W thrusting and NNE-SSW sinistral shearing interleaved with antithetic top-to-the E extensional and NNE-SSW dextral shears. Due to a lack of overprinting evidence and overlapping geochronological ages, non-coaxial deformation in the North Roe Nappe is interpreted to have developed broadly coevally during the Caledonian (c. 440-404 Ma). The results from this study suggest that Shetland was subject to inclined ... Thesis Greenland Durham University: Durham e-Theses Greenland |
institution |
Open Polar |
collection |
Durham University: Durham e-Theses |
op_collection_id |
ftunidurhamethes |
language |
unknown |
topic |
Structural Geology Fault zones Shear Zones Transpression Transtension Ductile Deformation Field Geology Microstructures Geochronology Shetland Caledonian Scotland |
spellingShingle |
Structural Geology Fault zones Shear Zones Transpression Transtension Ductile Deformation Field Geology Microstructures Geochronology Shetland Caledonian Scotland ARMITAGE, TIMOTHY,BRENDAN Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides |
topic_facet |
Structural Geology Fault zones Shear Zones Transpression Transtension Ductile Deformation Field Geology Microstructures Geochronology Shetland Caledonian Scotland |
description |
Strain in the lithosphere localises into weakened regions known as shear zones, which are often sites of repeated reactivation, reworking and poly-metamorphism. Mature shear zones are composite areas that include spatially and temporally heterogeneous combinations of coaxial and non-coaxial deformation, such as transpression and transtension. Due to their heterogeneous nature, determining the structural evolution and regional significance of shear zones is challenging. Such areas of ductile deformation are associated with the SE-dipping North Roe Nappe and the N-S striking Walls Boundary Fault (WBF) on NW Mainland Shetland. Here, the metamorphic basement and bounding strike-slip WBF provide pre-Permian geological links between the Scottish, Norwegian and Greenland sectors of the Caledonian orogen. Field mapping, microstructural characterisation and Rb-Sr geochronology in combination with other published work in the area show that NW Mainland Shetland was subject to Neoarchaean (c. 2800 – 2700 Ma), Neoproterozoic (827 Ma – 697 Ma) and Caledonian (487 – 404 Ma) deformation. Weakly-defined Neoarchaean deformation is preserved in the structurally lowest sections of the Uyea Gneiss Complex below the North Roe Nappe. Within the North Roe Nappe, Neoproterozoic deformation is mainly found in coaxially-deformed decimetre-scale horizons. The main ductile fabrics found on NW Mainland Shetland formed during top-to-the NW thrusting and top-to-the N/sinistral shearing, dated to be broadly Caledonian in age. Bounding the coaxially-deformed Neoproterozoic horizons are decimetre-scale horizons of non-coaxial top-to-the W thrusting and NNE-SSW sinistral shearing interleaved with antithetic top-to-the E extensional and NNE-SSW dextral shears. Due to a lack of overprinting evidence and overlapping geochronological ages, non-coaxial deformation in the North Roe Nappe is interpreted to have developed broadly coevally during the Caledonian (c. 440-404 Ma). The results from this study suggest that Shetland was subject to inclined ... |
format |
Thesis |
author |
ARMITAGE, TIMOTHY,BRENDAN |
author_facet |
ARMITAGE, TIMOTHY,BRENDAN |
author_sort |
ARMITAGE, TIMOTHY,BRENDAN |
title |
Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides |
title_short |
Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides |
title_full |
Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides |
title_fullStr |
Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides |
title_full_unstemmed |
Structural and Geochronological Investigations into Mid-Crustal Shear Zones, Shetland, Scottish Caledonides |
title_sort |
structural and geochronological investigations into mid-crustal shear zones, shetland, scottish caledonides |
publishDate |
2021 |
url |
http://etheses.dur.ac.uk/14299/ http://etheses.dur.ac.uk/14299/1/TimothyArmitage_CorrectedThesis.pdf http://etheses.dur.ac.uk/14299/2/Armitage000720772_AppendicesA.xlsx http://etheses.dur.ac.uk/14299/3/Armitage000720772_AppendicesB.xlsx |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland |
genre_facet |
Greenland |
op_relation |
oai:etheses.dur.ac.uk:14299 http://etheses.dur.ac.uk/14299/1/TimothyArmitage_CorrectedThesis.pdf http://etheses.dur.ac.uk/14299/2/Armitage000720772_AppendicesA.xlsx http://etheses.dur.ac.uk/14299/3/Armitage000720772_AppendicesB.xlsx http://etheses.dur.ac.uk/14299/ |
_version_ |
1766020110367064064 |