The premiums, paid on top of benchmark three-month London Metal Exchange (LME) prices, fell 10.7% from Friday's levels to $62.50 a tonne, the lowest since June 2017.
Detour is under pressure from two other investors, investment company Coast Capital Management L.P.and hedge fund Livermore Partners, to overhaul its board and consider a sale.
The support ship will be used at the company's Solwara 1 gold, copper and silver project, off the coast of Papua Guinea, set to be the world’s first commercial deep-sea mine.
The Toronto-based miner reported that the updated resource estimate has resulted in the addition of approximately 38,000 gold ounces in the Inferred category.