Summary:
The Project is located in the northwest portion of the McDermitt Caldera, a Tertiary-aged volcanic structure. The lithium mineralisation is hosted within a sequence of flat-lying paleo-lake sediments that overlie a basaltic volcanic basement (Unit 1). Recent geological work (post-February 2023 MRE) has defined a consistent stratigraphic sequence, comprising 12 distinct units of interbedded mudstones and tuffs, along with overlying colluvium.
Four of these units (Units 4, 6, 8, and 10) contain elevated lithium grades above 1,000ppm, with only Units 4 and 6 considered for processing in the PFS due to their higher head grades and more favourable recovery characteristics.
Unit 4 has an average thickness of 37m (but ranges up to 73m thick) and is dominated by interbedded mudstone and ash tuffs. Lithium values in Unit 4 are typically 1,000ppm to 2,000ppm with local zones greater than 3,000ppm Li. Unit 6 has an average thickness of 28m (maximum thickness of 49m) and is predominantly laminated mudstone and ash tuff. Lithium grades range from 1,000ppm to 2,000ppm with occasional zones greater than 2,500ppm Li.
Local geological knowledge has significantly advanced through a five-year drilling campaign, which included 62 holes (29 diamond core and 33 reverse circulation), resulting in over 5,400 lithium assays. This data, along with the refined stratigraphic understanding, forms the basis of the current McDermitt resource model.
At a 1,000 ppm Li cut-off grade, the MRE has the following approximate extent:
- 6.4 km in the north-south direction,
- 6.5 km in the east-west direction,
- 0-200m below surface, locally with a thin layer of barren colluvium.