Abstract
Talon Nickel (USA) LLC is seeking to advance the Tamarack Project to extract high-grade Ni-Cu-PGE ore from the Tamarack Deposit in Minnesota, USA, via an underground mine and surface facilities. Comprehensive material characterization is integral to the environmental review and permitting process for the Project. The peridotite host rock of the Tamarack deposit, emplaced in association with the Midcontinent Rift, has undergone different degrees of alteration, including serpentinization, over ~1.1 billion years, leading to widespread replacement of original olivine grains. Quantitative mineralogy reports serpentine contents in peridotites range from 10 to > 50%. However, the interpretation of standard mineral characterization data is confounded by variable chemistry and, potentially, by variable crystallinity of rock samples, requiring the integration of seemingly contradictory results from multiple characterization methods. Specialized characterization techniques may be considered when working in serpentinized deposits. For example, Raman may be used to distinguish between multiple co-existing serpentine polytypes. Concerning acid-base accounting, modified Sobek neutralization potential measurements have suggested a correlation with the degree of serpentinization in the peridotites. However, silicate mineral reactivity is highly sensitive to preparation and test method. Integrating understanding across multiple data streams in concert is necessary to understand serpentinization and implications for waste rock management planning at the Project.