Geopacific chairman Ian Clyne will assume day-to-day management of the company until the new MD appointment is made.
Heeks told the board that it was "time for some fresh energy to carry Geopacific and the Woodlark Island gold project forward".
Clyne said that Heeks had been instrumental in the identification of the Woodlark for Geopacific and all of its positive developments to date.
"The board wishes to publicly acknowledge and thank Ron for his extremely valuable contribution to the company. We wish Ron every success for his future endeavours," Clyne said.
The company added that the Geopacific board remained fully committed to delivering a successful gold project on Woodlark Island in Milne Bay Province.
"Geopacific will immediately start an executive search process to identify an experienced senior executive with the desired skill sets and proven track record appropriate to leading our near-term exploration, development, construction and production objectives on Woodlark Island, and our executive support team in Perth.
"The board's priority is to work with management, as appropriate, to ensure that Geopacific has all the resources necessary to safely and successfully deliver a de-risked, viable project, which delivers a successful outcome for the benefit of all stakeholders - shareholders, employees, local residents of Woodlark Island and for Papua New Guinea," Geopacific said.