American Rare Earths (ASX:ARR) updated its scoping study for the Halleck Creek rare earth elements project in Wyoming, according to a Friday Australian bourse filing.

In its 3 million tonnes per annum base case, it expects annual production of around 4,169 metric tons of total rare earths oxide, including 1,833 metric tonnes of a mixed oxide of neodymium and praseodymium, with a capital expenditure of $456 million, with a 2.7-year payback period.

In the 6 million tonnes per annum case, it expects around 7,661 metric tonnes of total rare earth oxides in annual production, including 3,344 metric tonnes of mixed oxide of neodymium and praseodymium. It expects capital expenditure of $737 million, with a 1.8-year payback period.

The company is evaluating further studies in the light of increasing demand for rare earths, as Halleck Creek could support a much larger, long-term operation, with a potential for extended mine life and increased production capacity, the filing said.

It is looking at ways to fast-track development, including plans to start a first-phase pilot plant for the beneficiation process.

It needs funding of $380 million as well as $76 million of contingency to achieve project production outcomes as outlined in the study.

The firm's shares rose almost 2% in recent trading on Friday.