The Shawmere Anorthosite of Archean Age in the Kapuskasing Belt, Ontario

The Shawmere anorthosite occurs in the Kapuskasing belt of high-grade metamorphic rocks in northern Ontario. Reconnaissance mapping revealed that the $$780-km^{2}$$ body consists of massive, foliated, metamorphosed anorthosite to gabbroic anorthosite. Tonalitic bands are abundant near the margins. The K-Ar age on hornblende is 2,519 m.y.; this is interpreted to be the age of metamorphism and is consistent with determinations on other rocks of the Superior structural province which have been subjected to the Kenoran orogeny or thermal event.