It will provide around a fifth of the energy to keep the South Deep mine running.
Gold Fields CEO Nick Holland hailed the move as a "strong, positive" message to miners and investors.
Gold Fields has been given a given the green light by the energy regulator to develop a 40MW solar plant in Westonaria, it was announced on Thursday.
The National Energy Regulator of South Africa (Nersa) said it has granted a licence to a to GFI Joint Venture Holdings and Gold Fields to develop the facility on the mine's South Deep operation, after the company first made an application in 2017.