Hawley, who is also chairman and founder of Scorpio Gold (CN:SGN), has been with the company since July 2016.
In addition to founding Scorpio, he has also held roles at Teck Resources (CN:TECK/B), Noranda (now part of Glencore (LN:GLEN), Placer Dome and, later on, its acquirer Barrick Gold (CN:ABX).
Hawley said he and his team were focused on advancing the San Acacio project in Zacatecas, Mexico.
The change comes after Roy Bonnell stood down as president and CEO of Defiance at the end of last year. He had been with the company for less than six months.