Ijolite sample (5.1 cm) with calcite, nepheline, pyroxene, and titanium mineral(s).

The Oka Carbonatite Complex is located in Quebec, Canada. It’s a large body of alkaline igneous rocks intruded through Precambrian metamorphics. The Oka occurs in the western part of the Canadian Shield’s Monteregian Hills Province. Published research indicates that Oka rocks cooled from magma produced by partial melting of upper mantle rocks (inferred to be metasomatized garnet lherzolites). The rocks in the complex contain some rare elements, including economic concentrations of niobium (Nb). Several mines exploit Oka rocks for their Nb content. Oka rocks include coarsely-crystalline calciocarbonatites (a.k.a. sövites; a.k.a. C1 calciocarbonatites), alnoites, ijolites, and okaites.

Age: mid-Barremian Stage, mid-Early Cretaceous, 124-125 million years.