The anti-apartheid activist chairwoman of Gold Fields (NYSE:GFI) today announced her resignation from the position, along with her relinquishment of all her other private sector directorships and positions, to pursue political and socioeconomic goals.

Dr. Mamphela Ramphele was immediately replaced by Cheryl Carolus, the miner's non-executive director, who also serves as the executive chair of Peotona Group Holdings Ltd. and is a director of Investec and diamond giant De Beers. Ramphele was appointed to the Gold Fields board in July 2010 and had chaired the board since November 2010. Carolus was appointed a Gold Fields director in March 2009.

Ramphele's resignation comes two days after Gold Fields spun out two of its South African mining operations into Sibanye Gold. Until the spinoff, Gold Fields was the world's fourth-largest gold miner, relying on South Africa for 50% of its revenues. That exposure has now been reduced to 15%. Ramphele, a former managing director of the World Bank, is expected to soon announce the formation of a new political party to challenge the ruling African National Congress.