On the Formation Temperature of Carbonatite from the Oka, Quebec, Canada

The Oka, carbonatite complex is located 32km west of Montreal, Quebec, Canada, and is situated west end of “Monteregian Hills alkaline rock petrographic province”.The St. Lawrence Columbium and Metals Corporation Mine is situated near the center of the Oka carbonatite complex. The main ore mineral is pyrochlore, and the annual production is about 2250 tons of pyrochore concentration containing about 52% Nb2O5.Many of polyphase inclusions having very small size are found in calcite, apatite and biotite from the Oka carbonatite.The filling temperatures of fluid inclusions in calcite and apatite from carbonatite were determined under heating stage. From these results, the range of the filling temperatures of calcite is from 395°C to 275°C. 320°C in average, the range of apatite, from 350°C to 260°C, 300°C in average.The solid phases in polyphase inclusions in calcite and apatite show an interference color between crossed nicols, however, it does not melt at upper temperature than filling temperature of fluid inclusions. Mineral species of solid phase are not yet been determined.The analyses of experimental data allow to assume that the range of formation temperature of the Oka carbonatite is considered from 800v to 600°C.