Gowans, who was previously the head of Arizona Mining before it was acquired last year by South32, was appointed to Detour's board in August during the miner's protracted and costly battle with activist investor Paulson & Co which resulted in a board overhaul in December.
Detour said Gowans had resigned "to focus on his other professional commitments".
Director Dawn Whittaker, who was one of Paulson's board nominees, was appointed interim chair until the AGM on June 5.
Detour said the cost of the proxy contest was a cash outlay of US$19.8 million, including the settlement of $12.3 million in payments to certain and former employees, $4.9 million for engaging third party advisors and $2.6 million for reimbursing certain Paulson costs after both parties agreed to dismiss court action in February.
The company is also on the hunt for both a permanent CEO and CFO after James Mavor resigned as CFO last month and is set to leave the company in April.
Meanwhile, Detour reported 2018 revenue of US$776 million on the sale of 610,672 ounces of gold, at an average realised gold price of $1,268/oz, produced at an all-in sustaining cost of $1,158/oz sold.
Detour said AISC was 9% higher than in 2017 but below guidance of $1,200-$1,280/oz - saying it had increased because of higher sustaining capex and total cash costs but was below guidance due to delays in construction Cell 2 of the tailings facility, deferral of other discretionary capital and a weaker Canadian dollar than budgeted.
It reported a net loss for the year of $1 million, or 1c per basic share, and adjusted net earnings of $64.2 million or 37c per share.
The company had recently reported its "best ever" quarterly production of 158,200oz for the December period.
It said mineral reserves for its Detour Lake mine in Ontario at December 31 were 15.4 million ounces of gold, which provided for a further 22 years of operation based on expected throughput.
The company ended the year with $131.9 million in cash and equivalents and $221.3 million available from its $500 million credit facility.
Its shares - which have ranged from C$15.40-$9.11 over the past year - fell to $12.50 intraday but recovered to close at $12.87 to capitalise it at $2.26 billion.