Abstract
Porphyry-epithermal-skarn deposits are key sources of Cu, Au, and other critical metals. However, the temporal evolution of magmatic-hydrothermal processes within these systems remains unclear. This thesis focuses on two fault-controlled case study mineralized systems within the Yukon-Tanana terrane in northwestern British Columbia and south-central Yukon, within the Canadian Cordillera. These deposits formed during the mid- to Late Cretaceous and Paleocene and provide an ideal setting to examine the temporal controls on mineralizing hydrothermal fluid activity occurring at the intersection of magmatic, metamorphic, and structural processes.Firstly, detailed field mapping and sampling combined with a multi-phase petrochronological approach links high-temperature magmatic processes and lower-temperature hydrothermal activity. U-Pb dating of zircon and Re–Os molybdenite is integrated with more recently developed chronometers, including U-Pb garnet, titanite, apatite, and carbonate, to capture processes occurring across a broad temperature range. This approach facilitates the reconstruction of ore-forming events from early intrusive activity through prograde skarn formation to late barren hydrothermal fluid circulation along (re)activated brittle fault networks. Secondly, the systematics of U-Pb carbonate geochronology is investigated in detail to constrain the duration and evolution of low-temperature hydrothermal systems. To address current uncertainties in U incorporation and retention in carbonate minerals, in-situ geochronology, EPMA, and trace element analyses are combined with synchrotron spectroscopy. Controls on U
behaviour including redox conditions, fluid chemistry, and mineral growth dynamics are tracked though time within a long-lived magmatic-hydrothermal system. These datasets provide new insight into U mobility in geological fluids, uptake and retention in carbonate minerals, and implications for the reliability of this geochronometer.
Results demonstrate that hydrothermal activity within porphyry-style ore
deposits can persist significantly longer than associated magmatism and is closely linked to episodic reactivation of crustal-scale structures. The integration of multiple U-Pb datasets, compositional information, and detailed analysis of dynamic redox conditions within hydrothermal fluids highlights the importance of applying petrochronological techniques to hydrothermal processes. Further, structurally controlled, pulsed fluid flow, alongside local reduction processes, is shown to be central to both ore mineralization and U mobility. These findings have direct implications for mineral exploration strategies and assessments of ore deposit system longevity.
| Date of Award | 8 Jun 2026 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Catherine Mottram (Supervisor), James Darling (Supervisor) & Dawn Kellet (Supervisor) |
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