Detrital zircon U-Pb geochronology and Hf isotope geochemistry of Labrador and Curling group strata, Humber zone, Newfoundland Appalachians

Soukup, Maya Anna (2022) Detrital zircon U-Pb geochronology and Hf isotope geochemistry of Labrador and Curling group strata, Humber zone, Newfoundland Appalachians. Masters thesis, Memorial University of Newfoundland.

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The Humber zone of the western Newfoundland Appalachians formed during the protracted (200 Myr) breakup of the supercontinent Rodinia and the opening of the Iapetus Ocean along NE Laurentia (ancestral North America). Deep-marine strata of the Humber Arm allochthon (Curling Group) and shallow-marine strata of the parautochthonous Humber platform (Labrador Group) record changes in Ediacaran to Cambrian paleogeography and sediment dispersal in NE Laurentia during and after breakup. While ion-microprobe-based detrital zircon U-Pb age results exist for some these rock units, recent advancements in high-n, laser ablation microanalytical techniques allow for more robust assessment of their provenance and new constraints on the geology of the rift-drift transition, relationships between coeval syn- and post-rift shelf and slope strata, and types of continental rift mechanisms in western Newfoundland. New high-n detrital zircon U-Pb (~300 analyses per sample) and Hf (~50 analyses per sample) isotope results from 11 rock samples from the Curling and Labrador groups confirm an early Cambrian rift-drift transition, indicate Ediacaran to early Cambrian maximum depositional ages, and support low-angle detachment style rift models for the NE Laurentian margin. Margin-normal transform fault systems that were active during continental extension divided sediment source areas between upper-plate and lower-plate margin settings. Syn-rift, shallow-to-transitional marine (Bradore Formation) strata deposited along upper-plate margin segments mostly yield underlying Grenville basement-derived (950 – 1400 Ma) detrital zircon grains, whereas coeval continental slope debris flow (Summerside and Blow Me Down Brook formations) strata deposited along lower-plate margins contain well-mixed, polycyclic Mesoproterozoic to Neoarchean detrital zircon grains sourced from the Canadian Shield and Grenville province and minor input from rift-related igneous rocks. The late early Cambrian onset of thermal subsidence resulted in similar sediment sources deposited across the shelf and slope regions of both upper- and lower-plate margins and point to the decreased role of marginnormal fault systems after lithospheric breakup. Post-rift, continental slope debris flow (Irishtown Formation) and tidal marine (Hawke Bay Formation) strata mostly yield well-mixed, Proterozoic and Archean detrital zircon populations from the Canadian Shield and Grenville province. Minor Ediacaran (558 – 620 Ma) detrital zircon grains in Labrador and Curling group strata have superchondritic Hf isotope signatures that overlap in age with rift-related magmatism in the western Newfoundland - Quebec Appalachians and likely indicate repeated partial melting of enriched continental lithosphere during polyphase extension.

Item Type: Thesis (Masters)
Item ID: 15840
Additional Information: Includes bibliographical references
Keywords: detrital zircon, U-Pb geochronology, Hf isotopic geochemistry, Humber Zone, Iapetus Ocean
Department(s): Science, Faculty of > Earth Sciences
Date: October 2022
Date Type: Submission
Digital Object Identifier (DOI):
Library of Congress Subject Heading: Zircon--Newfoundland and Labrador--Humber Arm; Geological time; Isotope geology--Newfoundland and Labrador--Humber Arm

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