Under the deal, Mawson will sell 100% of the copper concentrate produced at its operating Dikulushi mine and its development project, Kapulo, both in the Democratic Republic of Congo.

The contract covers 48 months from the time commercial production is declared at Kapulo.

Trafigura has provided Mawson with a $US50 million ($A53.5 million) facility to be prepaid to the company immediately.

The facility will have eight repayment instalments starting from March 2015.

The funds will cover the remaining $48 million worth of construction work at Kapulo, with around $77 million spent to date.

Commissioning should begin in the December quarter.

"Completion of the offtake agreement and funding with Trafigura for our production from Dikulushi and Kapulo is a key milestone for Mawson West and provides a strong endorsement of our strategy and assets in the Democratic Republic of Congo," Mawson CEO Bruce McFadzean said.

"The prepayment of $50 million means the remaining capital expenditure required for the finalisation of development at the Kapulo project is now secured.

"With a strong balance sheet, underground production currently ramping up at Dikulushi and final development funding now secured for Kapulo, 2014 is poised to be another exciting year for Mawson West."