taux élevé d'extraction de métal

OBS: Il a été démontré que des taux élevés d'extraction (...) ne peuvent être obtenus que par la production de concentrés collectifs (...)

CONT: To obtain high metal recoveries from such ores requires the production of bulk rather than selective concentrates.
OBS: It has been demonstrated that high recoveries, which are essential for the economic viability of many of the N.B. deposits, can only be achieved through the production of bulk concentrates....