Pegmatitic lithium deposits in Canada

Abstract

Granitic pegmatites containing lithium minerals occur in the Yellow-knife-Beaulieu district, Northwest Territories; the Cat Lake-Winnipeg River, the Herb Lake, and East Braintree-West Hawk Lake districts, Manitoba; and the Preissac-Lacorne district, Quebec.Several general characteristics are exhibited: 1. The pegmatites occur in medium- to high-grade metamorphic rocks or in plutonic rocks. 2. They are associated spatially and perhaps genetically with bodies of granite that contain 20 to 40 percent microcline and 20 to 40 percent albite or oligoclase. 3. They are marginal and exterior pegmatites. 4. In districts where regional zonation of granitic pegmatites is present, the pegmatites richest in lithium minerals are farthest from the center of the associated body of granite. 5. In pegmatite bodies that contain spodumene from wall to wall except for discontinuous, narrow border and, or, wall zones, many or almost all of the spodumene crystals are oriented with their long axes perpendicular to the walls, and are too fine-grained to be hand-sorted on a commercial scale. 6. Cleavelandite is generally a principal component of the wall zones. 7. In a given internal structure unit, spodumene is one of the early minerals to form. 8. Replacement bodies containing spodumene have not been found. 9. Amblygonite and montebrasite have been found only in intermediate zones.Spodumene is the most abundant lithium mineral and it occurs in intermediate zone deposits, in thinly lenticular pods, and in pegmatite bodies that are essentially spodumene-bearing from wall to wall.The bulk of the present lithium reserves in Canada is contained in pegmatite bodies that are essentially spodumene-bearing from wall to wall. These bodies are typically dike-like or thinly lenticular in shape. The grade and grain size of the spodumene in deposits of this type are remarkably uniform. At present, two companies are considering the development of such deposits in the Preissac-Lacorne district, Quebec.