TORONTO Dec 18 (Reuters) - Canada's Inmet Mining Corp closed a $500 million debt offer on Tuesday with the proceeds of the deal to be used to fund the construction of its massive Cobre Panama copper project in Central America.

The base metal miner said funds raised through the issue of senior unsecured notes will be used for the development and potential expansion of the Panama project. The notes have a 7.5 percent coupon rate and will mature in 2021.

Inmet, the subject of a hostile C$5.1 billion ($5.2 billion) takeover bid by First Quantum Minerals Ltd, holds an 80 percent stake in Cobre Panama, one of the largest undeveloped copper deposits in the world.

The remaining 20 percent stake is owned by a South Korean consortium that includes Korea Resources Corp.

Cobre Panama is expected to cost some $6.2 billion to build. The company announced a $1 billion financing deal with Franco-Nevada Corp in August and closed a $1.5 billion debt deal in May.