| Line Item | Jun 30, 2026 | Mar 31, 2026 | Dec 31, 2025 | Sep 30, 2025 | Jun 30, 2025 | Mar 31, 2025 | Dec 31, 2024 | Sep 30, 2024 | Jun 30, 2024 | Mar 31, 2024 | Dec 31, 2023 | Sep 30, 2023 | Jun 30, 2023 | Mar 31, 2023 | Dec 31, 2022 | Sep 30, 2022 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Operating expenses | ||||||||||||||||
| Exploration and evaluation expenses | ||||||||||||||||
| General and administrative expenses | ||||||||||||||||
| Operating loss | ||||||||||||||||
| Other items | ||||||||||||||||
| Charge on Allseas settlement | — | — | — | |||||||||||||
| Nauru warrant cost | — | — | ||||||||||||||
| Equity-accounted investment (income) loss | ||||||||||||||||
| Gain on dilution of investment | ||||||||||||||||
| Change in fair value of warrant liability | ||||||||||||||||
| Foreign exchange loss (gain) | ||||||||||||||||
| Interest income | ||||||||||||||||
| Fees and interest on borrowings and credit facilities | ||||||||||||||||
| Loss and comprehensive loss for the period, before tax | ||||||||||||||||
| Income tax expense | ||||||||||||||||
| Net loss and comprehensive loss for the period, after tax | ||||||||||||||||
| Net loss per share - Basic (in dollars per share) | ||||||||||||||||
| Net loss per share - Diluted (in dollars per share) |