GEOLOGICAL SETTING AND FLUID HISTORY OF THE CENTENNIAL UNCONFORMITY-RELATED URANIUM DEPOSIT, AND IMPLICATIONS OF POST MACKENZIE DIABASE FLUID EVENTS
Date
2018-04-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
The first discovery of high-grade unconformity-related uranium mineralization at Rabbit Lake in 1978 shifted the Athabasca Basin to the forefront of uranium exploration and production. The work presented in this thesis is centered on the Centennial unconformity-related uranium deposit but many of the features studied have basin wide implications.
The Centennial unconformity-related uranium deposit represents the first significant uranium mineralization along the Snowbird tectonic zone in the south central part of the Athabasca Basin. The deposit is associated with a steeply WNW-dipping contact between Virgin Schist Group rocks and mylonitic granite of uncertain age. A detailed paragenetic study of the deposit area reveals a protracted history that is related to the episodic reactivation of brittle structures and associated fluid movement along this significant structural corridor. Quartz overgrowths, illite(±kaolinite), sudoite, and aluminum phosphate sulphate minerals appear to pre-date or are contemporaneous with uraninite precipitation, whereas magnesiofoitite and euhedral quartz precipitated after. Intrusion of diabase dykes (ca. 1270 Ma) is linked to the formation of clinochlore, euhedral quartz, pyrite, apatite and carbonate. The event to affect the mineralized zone at the Centennial deposit is the formation of kaolinite and Fe-oxyhydroxides.
Large zoned aluminum phosphate sulphate minerals indicate that conditions near the mineralized trend were more reduced relative to a more distal location. Differences in middle rare earth element contents from early zones to later formed zones indicate that there is a change in the availability of these elements temporally.
Oxygen and hydrogen isotopes of sudoite, clinochlore and late kaolinite indicate that fluids at the Centennial deposit have evolved through time. Basinal brines are present in the basin from ca. 1750 Ma until after 1270 Ma, whereas late kaolinite formed from meteoric water. Fluid flow associated with diabase emplacement and meteoric water incursion both represents significant
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metasomatic events which influence the composition of uraninite at the Centennial deposit and likely uraninite throughout the basin.
Description
Keywords
Athabasca Basin, uranium, unconformity, aluminum phosphate sulphate minerals, hydrothermal alteration, diabase, diagenesis
Citation
Degree
Master of Science (M.Sc.)
Department
Geological Sciences
Program
Geology