Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska
Thesis (M.S.) University of Alaska Fairbanks, 2022 Understanding the relationship of accreted terranes with pericratonic North America is critical for unraveling the complex, polydeformational history of the North American Cordillera. The Cordillera represents a multi-accretionary system that has be...
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ftunivalaska:oai:scholarworks.alaska.edu:11122/13094 2023-05-15T18:48:40+02:00 Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska Wildland, Alec D. Regan, Sean Nadin, Elisabeth Jones, James V. III 2022-08 http://hdl.handle.net/11122/13094 en_US eng http://hdl.handle.net/11122/13094 Department of Geosciences Shear zones Structural geology Intrusions Master of Science in Geoscience Thesis ms 2022 ftunivalaska 2023-02-23T21:38:03Z Thesis (M.S.) University of Alaska Fairbanks, 2022 Understanding the relationship of accreted terranes with pericratonic North America is critical for unraveling the complex, polydeformational history of the North American Cordillera. The Cordillera represents a multi-accretionary system that has been fundamentally active since the Jurassic. The allochthonous Yukon-Tanana Terrane is an extensive and heterogeneous accreted terrane in the northern Cordillera. The tectonic boundary separating the Yukon-Tanana Terrane from pericratonic North America is exposed in eastern Alaska and is defined by a northward-dipping and low-angle ductile shear zone. This shear zone is interpreted to have exposed the structurally lower assemblages of parautochthonous North America during top-to-the-southeast directed exhumation in the Cretaceous. This interpretation is based on muscovite, biotite, and hornblende metamorphic cooling ages (ca. 100-120) of amphibolitefacies rock samples collected within the parautochthon. Historically, ⁴⁰Ar/³⁹Ar thermochronology has been a major resource, along with quartz c-axis petrofabric analysis, in identifying the boundaries of the shear zone. However, temporal relationships between shear zone formation, exhumation, and magmatism have remained incompletely understood. Targeted geologic mapping and petrochronology using a more robust chronometer, such as monazite, can aid these previous radiometric and kinematic interpretations. U-Th-Pb monazite petrochronology of samples within and outside the shear zone have placed better constraints on the age of shearing and exhumation. These analyses and observations support that exhumation of the parautochthonous assemblages occurred during the Cretaceous. Additionally, the ductile shear zone which facilitated juxtaposition of allochthonous and parautochthonous assemblages was active ca. 108 Ma. The northern Cordillera is also home to widespread Cretaceous, voluminous, and metallogenically important magmatism in both Alaska and the Yukon Territory. U-Pb ... Thesis Alaska Yukon University of Alaska: ScholarWorks@UA Fairbanks Yukon |
institution |
Open Polar |
collection |
University of Alaska: ScholarWorks@UA |
op_collection_id |
ftunivalaska |
language |
English |
topic |
Shear zones Structural geology Intrusions Master of Science in Geoscience |
spellingShingle |
Shear zones Structural geology Intrusions Master of Science in Geoscience Wildland, Alec D. Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska |
topic_facet |
Shear zones Structural geology Intrusions Master of Science in Geoscience |
description |
Thesis (M.S.) University of Alaska Fairbanks, 2022 Understanding the relationship of accreted terranes with pericratonic North America is critical for unraveling the complex, polydeformational history of the North American Cordillera. The Cordillera represents a multi-accretionary system that has been fundamentally active since the Jurassic. The allochthonous Yukon-Tanana Terrane is an extensive and heterogeneous accreted terrane in the northern Cordillera. The tectonic boundary separating the Yukon-Tanana Terrane from pericratonic North America is exposed in eastern Alaska and is defined by a northward-dipping and low-angle ductile shear zone. This shear zone is interpreted to have exposed the structurally lower assemblages of parautochthonous North America during top-to-the-southeast directed exhumation in the Cretaceous. This interpretation is based on muscovite, biotite, and hornblende metamorphic cooling ages (ca. 100-120) of amphibolitefacies rock samples collected within the parautochthon. Historically, ⁴⁰Ar/³⁹Ar thermochronology has been a major resource, along with quartz c-axis petrofabric analysis, in identifying the boundaries of the shear zone. However, temporal relationships between shear zone formation, exhumation, and magmatism have remained incompletely understood. Targeted geologic mapping and petrochronology using a more robust chronometer, such as monazite, can aid these previous radiometric and kinematic interpretations. U-Th-Pb monazite petrochronology of samples within and outside the shear zone have placed better constraints on the age of shearing and exhumation. These analyses and observations support that exhumation of the parautochthonous assemblages occurred during the Cretaceous. Additionally, the ductile shear zone which facilitated juxtaposition of allochthonous and parautochthonous assemblages was active ca. 108 Ma. The northern Cordillera is also home to widespread Cretaceous, voluminous, and metallogenically important magmatism in both Alaska and the Yukon Territory. U-Pb ... |
author2 |
Regan, Sean Nadin, Elisabeth Jones, James V. III |
format |
Thesis |
author |
Wildland, Alec D. |
author_facet |
Wildland, Alec D. |
author_sort |
Wildland, Alec D. |
title |
Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska |
title_short |
Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska |
title_full |
Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska |
title_fullStr |
Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska |
title_full_unstemmed |
Temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern Cordillera, Alaska |
title_sort |
temporal links between ductile shearing, widespread plutonism, and tectonic exhumation near the boundary of parautochthonous and allochthonous terranes in the northern cordillera, alaska |
publishDate |
2022 |
url |
http://hdl.handle.net/11122/13094 |
geographic |
Fairbanks Yukon |
geographic_facet |
Fairbanks Yukon |
genre |
Alaska Yukon |
genre_facet |
Alaska Yukon |
op_relation |
http://hdl.handle.net/11122/13094 Department of Geosciences |
_version_ |
1766241873257562112 |