The appointment means the board is now split equally between men and women.
Moroney is Barrick's vice president, new exploration opportunities and is responsible for pipeline growth.
She has been with Barrick since 2002 and has over 25 years of experience in gold and copper exploration.
Moroney was on the board of PDAC over the 2014-17 period and was also named as one of "100 Global Inspirational Women in Mining" in 2015.
Barrick has the right to nominate one person to Reunion's board, as long as it holds at least a 10% stake in the company.
Reunion's board now has 10 members, eight of which are independent.