The companies say the combination will create an Americas-focused copper mining company with an operating portfolio of three long-life mines, as well as a pipeline of copper expansion and development projects.

Under the agreement, Copper Mountain shareholders will receive 0.381 of a Hudbay share for each Copper Mountain common share held.

The companies say the proposal represents a 23 per cent premium based on Hudbay's and Copper Mountain's 10-day volume-weighted-average share prices on April 12.

The deal, which requires approval by a two-thirds majority vote by Copper Mountain shareholders and a simple majority vote by Hudbay shareholders, is also subject to closing conditions including regulatory and court approvals.

Once the transaction is complete, Hudbay shareholders will own about 76 per cent of the combined company, while Copper Mountain shareholders will hold 24 per cent.