The Eagle project, which was discovered by Rio in 2002, is located in Upper Peninsula of Michigan, US.
The construction of the Eagle project is underway on the mill and mine sites, which includes earthworks, concrete installation and steel erection, and is more than 55% complete.
Initial production is expected to commence in the fourth quarter of 2014.
The total cash consideration comprises $250m as acquisition amount in addition to project expenditures of $65m from 1 January 2013 until closure of the transaction.
Lundin noted that the acquisition has been completely funded from its net cash balance as well as its current $350m revolving credit facility.
During its eight-year life, the mine is expected to produce 300 million lbs of nickel, 250 million lbs of copper and small amounts of other metals.
Annual production during 2015-17 is expected to average around 23,000t of nickel and 20,000t of copper, in addition to by-product credits of precious metals and cobalt.
Lundin Mining president and CEO Paul Conibear said: "We are very pleased to close the acquisition of this high-quality asset early, and especially pleased to see the high level of activity on site already as construction ramps up."
Lundin Mining is a diversified base metals company with operations across Portugal, Sweden, US and Spain.
Image: Eagle Mine is located in Marquette County in the Upper Peninsula of Michigan. Photo: courtesy of Rio Tinto Company.