The C$3.30 per share offer represents a premium of 42 percent over the Trelawney stock’s Thursday close of C$2.32 on the Toronto Venture Exchange.
Trelawney is developing Cote Lake deposit that has 0.9 million ounces of indicated gold and 5.9 million ounces of inferred gold.
Iamgold’s inferred resources will increase by 95 percent and measured and indicated resources will rise by 5 percent after the deal, the mid-tier gold company said in a statement.
The company, which has operations in North America, South America and Africa, recorded production from continuing operations of 896,000 ounces for 2011.
GMP Securities is the financial adviser of Iamgold.
Reporting by Aftab Ahmed in Bangalore; Editing by Sayantani Ghosh and Joyjeet Das