TSX-listed Marimaca said Locke would work alongside CEO Luis Tondo and executive chairman Michael Haworth.
Locke said he was "delighted" to join Marimaca, and said the company's exploration potential - highlighted by the discovery last week of a large magnetic anomaly - was "extremely compelling".
Locke was appointed CEO of Emmerson in early 2018, before which he was head of corporate for ASX-listed gold developer Papillon Resources, which was acquired by B2Gold in late 2014 for US$600 million.
Locke remains on the board of Emmerson as a director.