GEOLOGY OF THE CARGILL PHOSPHATE DEPOSIT IN NORTHERN ONTARIO.

The Cargill phosphate deposit, located 32km. southwest of Kapuskasing, was discovered in 1975 and has been evaluated through an extensive program of 190 drill holes, numerous chemical analyses, metallurgical tests, and engineering and economic studies. The alkalic complex, comprising principally carbonatite and pyroxenite-amphibolite rocks, has been interpreted to have been intruded into the rift system of the Kapuskasing High during late Precambrian near the intersection of northeast- and northwest-trending faults. The complex is one of at least ten known alkalic complexes in or close to the magnetic-gravity-high system and is expressed by an elongated, northeast-oriented, three-part magnetic anomaly 7. 2km. long by 2. 3km. wide. Vermiculite, columbium-bearing minerals, clay minerals and quartz sand are present in quantities that suggest the possibility of commercial development. Uranium is absent or occurs only in very minor amounts. A tentative open-pit mine, designed for preliminary feasibility studies, is estimated to contain a probable phosphate-bearing deposit of 62. 5 million metric tons at an average grade of 19. 6 per cent P//2O//5.