As part of the contract, GR will install secondary grinding equipment at the plant to boost throughput to 3.2 million tonnes per annum.
The existing carbon-in-leach circuit will also be tweaked and upgrades will be carried out on other process infrastructure.
GR managing director Geoff Jones said work would start immediately and wind up in the first half of 2021.
Jones said GR was involved in the initial development of Carosue Dam back in 2000 and the team looked forward to achieving positive outcomes for Saracen through the safe and successful delivery of the expansion works.
GR shares closed 1.3% higher at 76c, valuing the company at $116.8 million.
