Orion, which currently holds a 20.4% stake in Dalradian, will buy the rest of the shares that it does not already own.
Dalradian shareholders will receive a cash consideration of C$1.47 for each of their shares, representing a 62% premium to Wednesday’s closing price.
"Orion and Osisko are showing great confidence in Northern Ireland, our high grade Curraghinalt project and our West Tyrone workforce,” said Dalradian chief executive Patrick Anderson.
“Their goals as strategic investors are completely aligned with ours - to secure planning permission for an underground gold mine and continue advancing the project in a way that benefits all our stakeholders."
Dalradian said the Curraghinalt gold project is in permitting with exploration ongoing to build on a positive feasibility study released in January.
Orion chief investment officer, Oskar Lewnowski said the company is “very pleased” to expand its ownership in “one of the world's best undeveloped gold deposits”.
“Curraghinalt gets more exciting as additional exploration and engineering work is completed, the recent positive resource update being just the latest example,” he said.
“The Dalradian team has done an outstanding job of growing the deposit and advancing it through the feasibility stage.
“We look forward to working with the core Dalradian management team to secure planning permission for a world class mine using best-in-class mining, processing and environmental standards."