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Thesis Defence: Trace-element Geochemistry, Isotopic and Geochronological Results from the Ridge Zone at the Burgundy Cu-Au Alkalic Porphyry Prospect, Golden Triangle, Northwestern British Columbia, Canada
February 28 at 9:00 am - 1:00 pm
Joanna Dlugosz, supervised by Dr. Kyle Larson, will defend their thesis titled “Trace-element Geochemistry, Isotopic and Geochronological Results from the Ridge Zone at the Burgundy Cu-Au Alkalic Porphyry Prospect, Golden Triangle, Northwestern British Columbia, Canada” in partial fulfillment of the requirements for the degree of Master of Science in Earth and Environmental Sciences.
An abstract for Joanna Dlugosz’s thesis is included below.
Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.
ABSTRACT
Critical raw materials (CRM) are key in the transition to green economies. Therefore, emphasis has been placed on the research of geologic deposits hosting economically significant amounts of CRM, such as alkalic porphyry deposits. As such, elucidating the characteristics of known alkalic porphyry deposits will aid in prospecting for this potentially CRM-rich deposit type.
The Burgundy prospect is a silica-undersaturated Cu-Au alkalic porphyry prospect located on the Enduro Metals’ Newmont Lake property in the Golden Triangle of British Columbia. In situ LA-ICP-MS trace-element mapping and sulphur isotope analyses of pyrite and chalcopyrite, along with in situ LA-ICP-MS Rb-Sr geochronology of biotite, provide a better understanding of the mineral paragenesis of mineralization at this poorly characterized prospect. Map results demonstrate that grain boundaries and fractures are enriched in trace elements, indicating that Au, Ag, and CRM concentrations were upgraded by overprinting hydrothermal fluids. Sulphur isotope analyses of pyrite yield depleted rims (i.e., -6.2 ± 2.8‰ n = 62) and slightly more enriched cores (i.e., -4.2 ± 2.0‰ n = 34). Chalcopyrite grains yield marginally more enriched δ34S values than pyrite (i.e., -3.9 ± 2.8‰; n = 168/172), but with no systematic rim and core zonation. Overall, the negative δ34S values are indicative of sulphide mineralization from oxidized fluids. Results from Rb-Sr geochronology of biotite interpreted to be cogenetic with pyrite and chalcopyrite yield isochron dates ranging between 220.1 ± 1.2 and 196.6 ± 4.6 Ma. The youngest dates (197.8 ± 1.0 Ma and 196.6 ± 4.6 Ma) are interpreted to reflect late fluid alteration due to the chloritization of biotite in these samples. The remaining dates (220.1 ± 1.2 and 204.9 ± 1.2) are considered to record the timing of mineralization for the Burgundy prospect.
The results from this study indicate that mineralization in the Burgundy prospect occurred during infiltration of late, oxidized low-temperature hydrothermal-magmatic fluids between 220 to 205 Ma. The timing and sulphur isotope results are broadly similar to those of the nearby Galore Creek deposit and highlight the potential for discovering other alkalic porphyries in the Golden Triangle.
