Clarke has over 40 years of mining experience and was previously CEO of Central Asia before its IPO in 2010. He became chairman in June 2016.
He was previously managing director of Oriel Resources until its acquisition by Mechel in 2008, and was also managing director at Wardell Armstrong International, where he managed a number of consulting projects in the resource sector.
Pouroulis stepped down from the Toro board after a decade.
He is the founder and chairman of Petra Diamonds, and is also non-executive chairman at Benzu Resources, Alufer Mining, Rainbow Rare Earths, Chariot Oil & Gas and Desert Lion Energy.