Riley was appointed as the company's CEO on February 1, 2019, and has demonstrated strong capacity to provide the technical expertise and leadership to drive the company forward to fulfil its dual strategy of monetising the Sorpresa deposit and the pursuit for large copper-gold discoveries.
He replaces former managing director Kaminsky who retired from the role earlier this year and has been serving as a non-executive director.
The company said: "Over the last 15 years, John has been a driving force behind many of Rimfire’s achievements, including providing the platform of success that led to the greenfields discovery of Sorpresa at Fifield in 2010 and the subsequent JORC resource in 2014.
"The board, management and Rimfire team, including employees and contractors, wish John every success going forward and thank him for his valuable and substantial contribution throughout his tenure."
He will remain a substantial shareholder of the company.