Production would average 238,314oz/y from a 3,100tonnes per day operation at an all-in sustaining cost of $610/oz compared with 218,000oz at $704/oz in the prior study, with the capital efficiency of the project improving to $130/oz of production from $207/oz previously.

The updated project would yield an after-tax net present value of C$1.5 billion and an internal rate of return of 39.3% compared with C$413.2 million and 32.7% previously. The payback shortens from 3.7 years to 2.2 years. The first seven years of production would see Windfall produce 300,000oz/y at an 8.1g/t average diluted grade, peaking at 328,000oz in year six.

The measured and indicated resources tripled to about 1.8 million ounces with a further 4.2Moz in inferred resources at a US$1,500 per ounce gold reference price, compared with 601,000oz and 2.3Moz at $1,300/oz in the initial PEA.

"We believe this highly positive PEA is conservative," said Osisko Mining president and CEO John Burzynski.

"The eventual inclusion of high-grade infill results received since November 2020, and the results we anticipate as we complete the infill drilling for the feasibility study by the early fall of 2021, should convert a significant number of additional high-grade mineral resource estimate inferred ounces to the measured and indicated categories.

"In the next 12 months we are focused on completing drilling, the feasibility, optimising the capital programme and operating plans, and securing project financing, as we advance our goal to move the project to first production in 2024."

Shares in Osisko Mining are trading at C$2.95, valuing the company at $1.1 billion.