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Geochronological and pressure-temperature record of a psammopelitic gneiss in the Upper Deck of the Tantato Domain, northern Saskatchewan, Canada

University of British Columbia

The Upper Deck of the Tantato Domain in Northern Saskatchewan is situated within the southern Snowbird Tectonic Zone, at the southeastern margin of the Rae Province. The terrane comprises Archean-aged granulite-grade sedimentary and felsic to mafic igneous rocks which have been pervasively migmatized and mylonitized. Geological mapping with the Saskatchewan Geological Survey in 2014 and 2015 documented four to five stages of deformation, outlined by differences in folding styles and orientations. This thesis was carried out to test for a record of these deformation events in a psammopelite, a major map unit in the Upper Deck, using U-Pb-Th dating of monazite and associated pressure-temperature history reconstruction. Detailed U-Pb Laser Ablation Split Stream – Multi-Collector – Inductively Coupled Plasma – Mass Spectrometer (LASS-MC-ICP-MS) age dating of monazite from a psammopelitic rock unit revealed four distinct age populations: 1) ca. 2600 Ma crystallization of source material, consistent with similarly aged plutonic rocks adjacent to the study area; 2) ca. 2550 to 2520 Ma, broadly coeval with the regionally important MacQuoid orogen and consistent with a recognized high-P event in the Upper Deck; 3) a previously unrecognized ca. 2500 to 2300 Ma spread of ages indicating growth during the Arrowsmith orogeny, and 4) ca. 2000 to 1900 Ma period of monazite rim growth consistent with the ages of the Taltson-Thelon orogen as well as reactivation of the Snowbird Tectonic Zone, and consistent with another recognized high-P event in the Upper Deck. These different age populations are interpreted to approximately correspond to the multiple generations of structures recognized during initial field work. Metamorphic phase equilibria modelling was used to outline a decompression pathway for an Upper Deck specimen from ~800 to 850°C and 1.0 to 1.4 GPa to ~750 to 800°C and 0.65 to 0.90 GPa, coeval with monazite rim growth from ca. 1950 to 1900 Ma. This decompression pathway is consistent with previous work that recognized a similar pathway followed by an eclogite hosted in the Upper Deck (Baldwin et al., 2007).

Text

2019-08-09

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/71263

Earth and Environmental Sciences

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/