GRANITIC PEGMATITES OF THE CANADIAN CORDILLERA

Cordilleran pegmatites in the United States have been significant producers of strategic raw minerals and gemstones for over a century, but pegmatites in the Canadian Cordillera have, until recently, been largely overlooked. Improved access over the last two decades has led to a number of discoveries and an increasing volume of scientific research.

The pegmatites at Mt. Begbie, ~12 km south Revelstoke in British Columbia, have been known since the late 1880s. At least 55 pegmatite dikes and bodies, ranging from barren to beryl-columbite, beryl-columbite-phosphate, and lepidolite subtype pegmatites, occur over an area of 0.5 km² within metapelites. Fractionation within the pegmatite group increases from the SE to the NW.

Beryl- and tourmaline-bearing pegmatites associated with the Bayonne Batholith in southeastern British Columbia have been known since at least the early 1940s.

The Little Nahanni Pegmatite Group, discovered in 1960 along the border between the Yukon and Northwest Territories, consists of a swarm of subvertically dipping, cm- to m-scale LCT-type pegmatites extending over a 15 km strike length. Varying degrees of albitization and phyllic alteration of the dikes are associated with ore-grade Ta-Nb and Sn-W mineralization.

Deformed NYF pegmatites were discovered on the Kin property, 95 km northeast of Revelstoke in 1987. The pegmatites occur with a series of syenite sills related to the nearby Trident Creek alkaline complex. The pegmatites are enriched in REE, Nb, and Mo, and contain mainly monazite, allanite, aeschynite, molybdenite, and ferrocolumbite.

Pegmatites were discovered within the hornblende-bearing, composite O’Grady batholith, ~ 100 km north of Tungsten in the western Northwest Territories, in 1993. The pegmatites belong to the elbaite subtype of rare-element granitic pegmatite. Since 2006 the pegmatites have produced small amounts of gem tourmaline.

The Rau pegmatite field was discovered ca. 2006 ~100 km northeast of Mayo in the Yukon Territory. The field lies between the Rackla plutonic rock and the Au-Ag Rau deposit. The majority of pegmatites occur in two groups that lie 0.3 km apart. Preliminary work suggests that the rare-element-rich Dike 1 of the first group may be the most evolved pegmatite dike in the field and may be an example of pegmatite contamination in situ.