PMI said Asanko is offering 0.21 of a common share for each PMI share, which would value PMI shares at just over 44 cents apiece, a 79 per cent premium to their 20-day volume weighted average.
Following completion of deal, PMI and Asanko shareholders would each hold about 50 of the combined company.
On the Toronto Stock Exchange, PMI shares closed up 12.5 cents, or 44.64 per cent, at 40.5 cents on very heavy volume of more than 12.7 million shares, making it the most active issue on the TSX.
Asanko stock dropped six cents , or 2.86 per cent, to $2.04.
Both companies have assets in Ghana.