The Pesos 570m ($US 132.9m) contract has been awarded to a joint venture of Skanska and local partners Chediack and Milicic. Skanska's share of the contract is worth around Pesos 190m, and covers all civil works including embankments, drainage, and 29 bridges.
Construction will begin next month and the line will be completed in the first quarter of 2014.
The Pesos 25.5bn Rio Colorado mine is expected to generate an output of 2.4 million tonnes in its first phase, and capacity is expected to increase to 4.3m tonnes in the second phase of the project. Ferrosur Roca has been awarded the concession to operate the trains, which will cover a distance of 756km between the mine and a new purpose-built export terminal at the port of Bahia Blanca near Buenos Aires.