The PEA outlines an openpit mine for the gold camp with preproduction capex of US$380 million, an after-tax NPV (5% discount) of $367 million and an IRR of 25% with a 2.8-year payback.
It estimates an average annual production over the initial 10 years of the 11-year mine-life of 188,500 ounces, at an all-in sustaining cost of $595/oz over the life of mine.
President and CEO Phillip Walford said the results demonstrated a very robust, low cost operation was possible.
He said the project also had further potential, including additional openpit resources at the Sprite deposit and bog extension area and the underground resource at the Marathon deposit, that was not drilled sufficiently to include in a mine plan.
"The cost of finding a new ounce of gold on the property remains at $10 per new ounce so our exploration program continues to be highly cost-effective," he said.
Earlier this month, Marathon updated its Valentine Lake resource which comprises four deposits - Marathon, Leprechaun, Victory and Sprite - but Sprite was excluded from mine development plans until further drilling increased its resource.
The company has said it expected to progress towards development and was planning metallurgical testwork, further drilling and work on approvals, subject to financing.
It had C$4.1 million (US$3.2 million) in cash and equivalents at the end of March.
Marathon shares, which hit a 52-week low of C85c at the end of April, closed down 1c on Friday to $1.03, valuing it at $150.5 million.