Bayshore Minerals was described as a private, BC-based explorer focused on the exploration and development of the Elk property.
It was founded by SRK Canada mining division consultant Grant Carlson.
"Bayshore plans to continue to grow its portfolio of gold properties as opportunities arise," the Equinox statement said.
Equinox said the deal comprised $1 million (US$744,000) in cash, which had been received, and $9 million in a first-ranking secured promissory note, payable in annual instalments of $3 million, starting two years from closing.
It said the amount due under the note might be adjusted if Bayshore paid $8 million within two years from closing, or $9.5 million within three years, which would represent full and final payment.
Bayshore bought the project by acquiring the shares of Equinox subsidiary Gold Mountain Mining Corp.
Trek Mining's past-producing Elk project became part of the Equinox portfolio in the 2017 three-way merger of Trek, NewCastle Gold and Anfield Gold.
Equinox is honing its focus on gold production, spinning out its copper assets last year into the as-yet unlisted Solaris Copper.
Equinox poured first gold at its Aurizona mine in Brazil mid-month, is producing gold at its Mesquite mine in California and is aiming for production at its Castle Mountain mine, also in California, in the first half of next year.
Equinox shares closed up 1.87% or 2c yesterday to $1.09, valuing it at $602.8 million.