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Petrology, Geochemistry, and Geochronology of the Pikoo Kimberlites, Saskatchewan
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- Author / Creator
- Smyth, Denelle
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The Pikoo kimberlites of east-central Saskatchewan are a relatively recent discovery, comprising at least ten discreet bodies thought to erupt through the Sask Craton, a small Archean microcontinent enclosed within the Paleoproterozoic Trans-Hudson Orogen. Since the Sask Craton also plays host to the 70+ bodies of the diamondiferous Cretaceous Fort à la Corne kimberlites, which are among the largest kimberlites in the world, significant interest lay in unraveling the genesis of the Pikoo bodies. This study presents the first detailed examination of the petrology and geochronology of the Pikoo kimberlites. A combination of detailed petrography, major and minor element chemistry analyzed by EPMA, and trace element determinations measured via LA-ICP-MS was employed to characterize the Pikoo samples as archetypal coherent (hypabyssal) kimberlite. Traditional criteria for diamond preservation potential were applied to the Pikoo ilmenite by assessing their Fe2O3 and MgO contents. The results indicated high MgO and low Fe2O3 within the grain interiors and rims with elevated MgO and MnO in PK150, PK151, PK314, and variably in PK312. The high-Fe mineral compositions of PK346 contradict the trends of the other intrusions, suggesting PK346 formed from an oxidized, high-carbonate late pulse of previously fractionated magma. The differences in magma evolution can explain the striking petrographic and chemical distinctions highlighted between the two most significant intrusions of PK150 and PK346, as well as the notably less favourable microdiamond results North Arrow reported for PK346. A robust U-Pb age of 417 ± 14 Ma was determined from PK150 perovskite analyzed in situ via LA-ICP-MS. The data were processed using two approaches to confirm the perovskite represented a single population with a uniform common Pb composition. This age is distinctly different from the nearby FALC kimberlites but overlaps with occurrences in the Slave Craton, the United States, Russia, and Namibia. This may suggest more widespread diamond-bearing kimberlite activity in circa Silurian times. Tracer isotopes were also measured in situ via LA-MC-ICP-MS on PK150 perovskite. The dominant range in εNdi (+1.8 to -2.0) is near chondritic, suggesting a deep mantle source isolated from contamination.
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- Subjects / Keywords
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- Graduation date
- Spring 2020
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.