Hannah Eaton-Tessier, MSc
H. Eaton-Tessier1, D. Gregory1, E. Hastie2
1Earth Sciences Department, University of Toronto, Toronto, Ontario, Canada
2Ontario Geologic Survey, Sudbury, Ontario, Canada
Northwestern Ontario is host to dozens of highly enriched orogenic gold deposits. Enriched in critical metals alongside gold, these deposits also have potential as economic sources of nickel, cobalt, antimony, and tellurium. Despite the economic importance of these deposits, the ore forming processes and fluid sources that formed these deposits are not fully understood.
This study employs morphological and geochemical analysis of pyrite samples from 17 orogenic gold deposits across Northwestern Ontario to better understand the formation of the deposits. Reflected light microscopy and scanning electron microscopy (SEM) was used for detailed imaging of the pyrite grains, detailing the generations and morphologies present in the pyrite grains to develop a paragenesis for each sample. Following this, the geochemical composition of the pyrite grains was analyzed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The geochemistry of pyrite is essential to understanding deposit formation as it reveals information regarding the ore-forming fluid, including the temperature, pH, salinity, and oxidation state. The data collected in this project will allow for comparison of the depositional mechanisms and fluid sources throughout the deposits in the study, creating associations between the trace element assemblages and the stages of gold deposition. The trace element assemblages will also allow for predicting at a larger scale which gold deposits may have economic potential as critical metal sources.