{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/139786"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/139786","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Tectonic Transport Directions and Timing of Metamorphism in the southern part of the Northern Highlands Terrane, Scotland","abstract":"The metasedimentary rocks of the Northern Highlands Terrane (NHT) in NW Scotland were deformed and metamorphosed during a series of orogenic events which occurred from the Neoproterozoic (Knoydartian orogeny) to the Ordovician-early Devonian (Caledonian orogeny). Previous kinematic studies in the northern and central parts of the NHT indicate that tectonic transport changed from top to the N in the core of the orogen at 450-440 Ma to top to the W in the foreland margin at ~437-430 Ma. Here we extend these studies to the southern part of the NHT using microstructural, quartz crystal fabric, and isotopic analysis on oriented samples collected from four E-W transects across the Sgurr Beag thrust (SBT) in the Steep Belt and from multiple sites in the Flat Belt. These samples record at least two Caledonian metamorphic and deformational events with a nebulous early high temperature event and a later lower temperature event, although it is not clear if these are distinct events or parts of continuous metamorphism and deformation during early progressive cooling of the orogen. Early high temperatures of mineral crystallization and deformation (< c.675 °C) are indicated by Zr-in-titanite thermometry and microstructural evidence for both quartz and feldspar grains dynamically recrystallizing by grain boundary migration processes. These early high temperature microstructures are partially-completely overprinted by lower temperature (490-650 °C) D2-D3 microstructures and quartz crystal fabrics associated with the macroscopic foliation and mineral stretching lineation present in each sample. In the Flat Belt the D2 lineation plunges gently to the SSE, but in the Steep Belt the composite D2-D3 lineation plunges more steeply (to almost vertical) towards the SE/SSE on the SE dipping foliation. Quartz c-axis fabric indicate top to the NNE shearing at deformation temperatures of 550-650 °C in the Flat Belt, top down to the SW shearing at 540-590 °C in the Steep Belt transect across the SBT at Loch Monar, and top down to the SE/SSE shearing at ~490-650 °C in more southerly positioned Steep Belt transects at Glen Shiel, Kinloch Hourn, and Lochailort-Loch Eilt. U-Pb isotopic ages collected from titanite, monazite, and xenotime indicate that mineral growth occurred during the Knoydartian - late Neoproterozoic (765-638 Ma), the Grampian II (460–437 Ma), and late/post-Scandian events (418–412 Ma). Some of the older Caledonian (Grampian-Scandian) ages are compatible with geologic constraints for cessation of D3 shearing (Steep Belt) and buckle folding (Flat Belt) at c. 432-425 Ma and mineral growth may have occurred during D2 and/or D3 deformation. Younger Scandian mineral ages are problematic and could, for example, be explained by periods of fluid flow and associated mineral growth (perhaps associated with strike-slip faulting) that post-dates D2-D3 deformation within the NHT.","abstract_html":"The metasedimentary rocks of the Northern Highlands Terrane (NHT) in NW Scotland were deformed and metamorphosed during a series of orogenic events which occurred from the Neoproterozoic (Knoydartian orogeny) to the Ordovician-early Devonian (Caledonian orogeny). Previous kinematic studies in the northern and central parts of the NHT indicate that tectonic transport changed from top to the N in the core of the orogen at 450-440 Ma to top to the W in the foreland margin at ~437-430 Ma. Here we extend these studies to the southern part of the NHT using microstructural, quartz crystal fabric, and isotopic analysis on oriented samples collected from four E-W transects across the Sgurr Beag thrust (SBT) in the Steep Belt and from multiple sites in the Flat Belt. These samples record at least two Caledonian metamorphic and deformational events with a nebulous early high temperature event and a later lower temperature event, although it is not clear if these are distinct events or parts of continuous metamorphism and deformation during early progressive cooling of the orogen. Early high temperatures of mineral crystallization and deformation (&lt; c.675 °C) are indicated by Zr-in-titanite thermometry and microstructural evidence for both quartz and feldspar grains dynamically recrystallizing by grain boundary migration processes. These early high temperature microstructures are partially-completely overprinted by lower temperature (490-650 °C) D2-D3 microstructures and quartz crystal fabrics associated with the macroscopic foliation and mineral stretching lineation present in each sample. In the Flat Belt the D2 lineation plunges gently to the SSE, but in the Steep Belt the composite D2-D3 lineation plunges more steeply (to almost vertical) towards the SE/SSE on the SE dipping foliation. Quartz c-axis fabric indicate top to the NNE shearing at deformation temperatures of 550-650 °C in the Flat Belt, top down to the SW shearing at 540-590 °C in the Steep Belt transect across the SBT at Loch Monar, and top down to the SE/SSE shearing at ~490-650 °C in more southerly positioned Steep Belt transects at Glen Shiel, Kinloch Hourn, and Lochailort-Loch Eilt. U-Pb isotopic ages collected from titanite, monazite, and xenotime indicate that mineral growth occurred during the Knoydartian - late Neoproterozoic (765-638 Ma), the Grampian II (460–437 Ma), and late/post-Scandian events (418–412 Ma). Some of the older Caledonian (Grampian-Scandian) ages are compatible with geologic constraints for cessation of D3 shearing (Steep Belt) and buckle folding (Flat Belt) at c. 432-425 Ma and mineral growth may have occurred during D2 and/or D3 deformation. Younger Scandian mineral ages are problematic and could, for example, be explained by periods of fluid flow and associated mineral growth (perhaps associated with strike-slip faulting) that post-dates D2-D3 deformation within the NHT.","abstract_has_math":false,"creators":["Davis, Ella Fae"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Geosciences","degree_department":"Geosciences","school":null,"contributors":[],"advisors":[],"committee_chairs":["Law, Richard D."],"committee_members":["Spotila, James A.","Caddick, Mark James"],"year":2025,"date_issued":"2025-12-01","date_published":"2025-12-01","updated_at":"2026-07-22T22:19:18Z","subjects":["deformation","metamorphism","microstructures","dynamic recrystallization","monazite geochronology","titanite geochronology","titanite thermometry","Scotland"],"languages":["en"],"rights":["Creative Commons Attribution 4.0 International"],"rights_urls":["http://creativecommons.org/licenses/by/4.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:44714"],"render_values":[{"text":"vt_gsexam:44714","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/139786","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Law, Richard D."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Spotila, James A.","Caddick, Mark James"]},{"key":"dc:contributor.department","label":"Department","values":["Geosciences"]},{"key":"dc:creator","label":"Author","values":["Davis, Ella Fae"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-12-02T09:00:16Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2025-12-02T09:00:16Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-12-01"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Geosciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["deformation","metamorphism","microstructures","dynamic recrystallization","monazite geochronology","titanite geochronology","titanite thermometry","Scotland"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Creative Commons Attribution 4.0 International"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://creativecommons.org/licenses/by/4.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:44714"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/139786"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The metasedimentary rocks of the Northern Highlands Terrane (NHT) in NW Scotland were deformed and metamorphosed during a series of orogenic events which occurred from the Neoproterozoic (Knoydartian orogeny) to the Ordovician-early Devonian (Caledonian orogeny). Previous kinematic studies in the northern and central parts of the NHT indicate that tectonic transport changed from top to the N in the core of the orogen at 450-440 Ma to top to the W in the foreland margin at ~437-430 Ma. Here we extend these studies to the southern part of the NHT using microstructural, quartz crystal fabric, and isotopic analysis on oriented samples collected from four E-W transects across the Sgurr Beag thrust (SBT) in the Steep Belt and from multiple sites in the Flat Belt. These samples record at least two Caledonian metamorphic and deformational events with a nebulous early high temperature event and a later lower temperature event, although it is not clear if these are distinct events or parts of continuous metamorphism and deformation during early progressive cooling of the orogen. Early high temperatures of mineral crystallization and deformation (< c.675 °C) are indicated by Zr-in-titanite thermometry and microstructural evidence for both quartz and feldspar grains dynamically recrystallizing by grain boundary migration processes. These early high temperature microstructures are partially-completely overprinted by lower temperature (490-650 °C) D2-D3 microstructures and quartz crystal fabrics associated with the macroscopic foliation and mineral stretching lineation present in each sample. In the Flat Belt the D2 lineation plunges gently to the SSE, but in the Steep Belt the composite D2-D3 lineation plunges more steeply (to almost vertical) towards the SE/SSE on the SE dipping foliation. Quartz c-axis fabric indicate top to the NNE shearing at deformation temperatures of 550-650 °C in the Flat Belt, top down to the SW shearing at 540-590 °C in the Steep Belt transect across the SBT at Loch Monar, and top down to the SE/SSE shearing at ~490-650 °C in more southerly positioned Steep Belt transects at Glen Shiel, Kinloch Hourn, and Lochailort-Loch Eilt. U-Pb isotopic ages collected from titanite, monazite, and xenotime indicate that mineral growth occurred during the Knoydartian - late Neoproterozoic (765-638 Ma), the Grampian II (460–437 Ma), and late/post-Scandian events (418–412 Ma). Some of the older Caledonian (Grampian-Scandian) ages are compatible with geologic constraints for cessation of D3 shearing (Steep Belt) and buckle folding (Flat Belt) at c. 432-425 Ma and mineral growth may have occurred during D2 and/or D3 deformation. Younger Scandian mineral ages are problematic and could, for example, be explained by periods of fluid flow and associated mineral growth (perhaps associated with strike-slip faulting) that post-dates D2-D3 deformation within the NHT."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["The metasedimentary rocks of the Northern Highlands Terrane (NHT) in NW Scotland were deformed and metamorphosed over a series of mountain building events which occurred from the Neoproterozoic (870-720 Ma, known as the Knoydartian orogeny) to the Ordovician-early Devonian (480-420 Ma, known as the Caledonian orogeny). Previous studies on the history of deformation which occurred during these events conducted in the northern and central parts of the NHT indicate that tectonic motion changed from northward motion in the eastern NHT in the early Caledonian (450-440 Ma) to westward motion along the Moine thrust in the western NHT in the mid-Caledonian (437-430 Ma). Here we use microstructural and isotopic analysis to extend these studies to the southern part of the NHT using oriented samples collected from four E-W transects across the Sgurr Beag thrust (SBT) in the Steep Belt and from multiple sites in the Flat Belt. These samples record at least two phases of metamorphism and deformation during the Caledonian orogeny. An earlier high temperature event (< c.675 °C) is recorded by high temperature titanite growth and quartz and feldspar grains which show evidence of high temperature deformation. This was followed by a lower temperature event during which the mineral fabrics have been partially-completely overprinted by lower temperature (490-650 °C) deformation which we have used to constrain the mid-Caledonian shear senses in the southern NHT. In the eastern Flat Belt, samples record a reverse sense of motion towards the NW, while to the west in the Steep Belt a normal sense of motion is recorded directed to the SW at Loch Monar and to the SE at Glen Shiel, Kinloch Hourn, and Lochailort-Loch Eilt. U-Pb isotopic ages collected from titanite, monazite, and xenotime grains indicate that mineral growth occurred throughout the southern NHT during the Knoydartian (765-638 Ma), the mid-Caledonian (Grampian II, 460–437 Ma), and the late Caledonian (Scandian, 418-412 Ma) events. The mid-Caledonian events are compatible with the timing of large scale folding and shearing in the Steep Belt, however the late mineral ages (418-412 Ma) are problematic and could be explained by periods of high temperature fluid flow."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Tectonic Transport Directions and Timing of Metamorphism in the southern part of the Northern Highlands Terrane, Scotland"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Law, Richard D."],"dc:contributor.committeemember":["Spotila, James A.","Caddick, Mark James"],"dc:contributor.department":["Geosciences"],"dc:creator":["Davis, Ella Fae"],"dc:date.accessioned":["2025-12-02T09:00:16Z"],"dc:date.available":["2025-12-02T09:00:16Z"],"dc:date.issued":["2025-12-01"],"dc:description.abstract":["The metasedimentary rocks of the Northern Highlands Terrane (NHT) in NW Scotland were deformed and metamorphosed during a series of orogenic events which occurred from the Neoproterozoic (Knoydartian orogeny) to the Ordovician-early Devonian (Caledonian orogeny). Previous kinematic studies in the northern and central parts of the NHT indicate that tectonic transport changed from top to the N in the core of the orogen at 450-440 Ma to top to the W in the foreland margin at ~437-430 Ma. Here we extend these studies to the southern part of the NHT using microstructural, quartz crystal fabric, and isotopic analysis on oriented samples collected from four E-W transects across the Sgurr Beag thrust (SBT) in the Steep Belt and from multiple sites in the Flat Belt. These samples record at least two Caledonian metamorphic and deformational events with a nebulous early high temperature event and a later lower temperature event, although it is not clear if these are distinct events or parts of continuous metamorphism and deformation during early progressive cooling of the orogen. Early high temperatures of mineral crystallization and deformation (< c.675 °C) are indicated by Zr-in-titanite thermometry and microstructural evidence for both quartz and feldspar grains dynamically recrystallizing by grain boundary migration processes. These early high temperature microstructures are partially-completely overprinted by lower temperature (490-650 °C) D2-D3 microstructures and quartz crystal fabrics associated with the macroscopic foliation and mineral stretching lineation present in each sample. In the Flat Belt the D2 lineation plunges gently to the SSE, but in the Steep Belt the composite D2-D3 lineation plunges more steeply (to almost vertical) towards the SE/SSE on the SE dipping foliation. Quartz c-axis fabric indicate top to the NNE shearing at deformation temperatures of 550-650 °C in the Flat Belt, top down to the SW shearing at 540-590 °C in the Steep Belt transect across the SBT at Loch Monar, and top down to the SE/SSE shearing at ~490-650 °C in more southerly positioned Steep Belt transects at Glen Shiel, Kinloch Hourn, and Lochailort-Loch Eilt. U-Pb isotopic ages collected from titanite, monazite, and xenotime indicate that mineral growth occurred during the Knoydartian - late Neoproterozoic (765-638 Ma), the Grampian II (460–437 Ma), and late/post-Scandian events (418–412 Ma). Some of the older Caledonian (Grampian-Scandian) ages are compatible with geologic constraints for cessation of D3 shearing (Steep Belt) and buckle folding (Flat Belt) at c. 432-425 Ma and mineral growth may have occurred during D2 and/or D3 deformation. Younger Scandian mineral ages are problematic and could, for example, be explained by periods of fluid flow and associated mineral growth (perhaps associated with strike-slip faulting) that post-dates D2-D3 deformation within the NHT."],"dc:description.abstractgeneral":["The metasedimentary rocks of the Northern Highlands Terrane (NHT) in NW Scotland were deformed and metamorphosed over a series of mountain building events which occurred from the Neoproterozoic (870-720 Ma, known as the Knoydartian orogeny) to the Ordovician-early Devonian (480-420 Ma, known as the Caledonian orogeny). Previous studies on the history of deformation which occurred during these events conducted in the northern and central parts of the NHT indicate that tectonic motion changed from northward motion in the eastern NHT in the early Caledonian (450-440 Ma) to westward motion along the Moine thrust in the western NHT in the mid-Caledonian (437-430 Ma). Here we use microstructural and isotopic analysis to extend these studies to the southern part of the NHT using oriented samples collected from four E-W transects across the Sgurr Beag thrust (SBT) in the Steep Belt and from multiple sites in the Flat Belt. These samples record at least two phases of metamorphism and deformation during the Caledonian orogeny. An earlier high temperature event (< c.675 °C) is recorded by high temperature titanite growth and quartz and feldspar grains which show evidence of high temperature deformation. This was followed by a lower temperature event during which the mineral fabrics have been partially-completely overprinted by lower temperature (490-650 °C) deformation which we have used to constrain the mid-Caledonian shear senses in the southern NHT. In the eastern Flat Belt, samples record a reverse sense of motion towards the NW, while to the west in the Steep Belt a normal sense of motion is recorded directed to the SW at Loch Monar and to the SE at Glen Shiel, Kinloch Hourn, and Lochailort-Loch Eilt. U-Pb isotopic ages collected from titanite, monazite, and xenotime grains indicate that mineral growth occurred throughout the southern NHT during the Knoydartian (765-638 Ma), the mid-Caledonian (Grampian II, 460–437 Ma), and the late Caledonian (Scandian, 418-412 Ma) events. The mid-Caledonian events are compatible with the timing of large scale folding and shearing in the Steep Belt, however the late mineral ages (418-412 Ma) are problematic and could be explained by periods of high temperature fluid flow."],"dc:description.degree":["Master of Science"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:44714"],"dc:identifier.uri":["https://hdl.handle.net/10919/139786"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["Creative Commons Attribution 4.0 International"],"dc:rights.uri":["http://creativecommons.org/licenses/by/4.0/"],"dc:subject":["deformation","metamorphism","microstructures","dynamic recrystallization","monazite geochronology","titanite geochronology","titanite thermometry","Scotland"],"dc:title":["Tectonic Transport Directions and Timing of Metamorphism in the southern part of the Northern Highlands Terrane, Scotland"],"dc:type":["Thesis"],"thesis:degree_discipline":["Geosciences"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:18Z"}