The Ellison Lake Pluton; a cordierite-bearing monzogranitic intrusive body in southwestern Nova Scotia

The Ellison Lake pluton, located 3km NW of the South Mountain batholith in southwestern Nova Scotia. is a small intrusive body of porphyritic monzogranite containing the aluminous minerals cordierite, garnet and tourmaline. Cordierite and garnet are considered of magmatic and xenocrystic origin, respectively, whereas the tourmaline is probably metasomatic. The SiOr content and most other chemical characteristics of the m6nzogranite are similar to those of the biotite ganodiorite of the South Mountain b,atholith, except that the monzogranite has higher Al2O3, K2O and P2O5, consistent with its greater abundance df aluminous minerals, K-feldspar and apatite. The monzogranite may have formed from the same magma as the South Mountain granodiorite but with more extensive assimilation of pelitic material; a K-Ar age determination of 346 + 12 Ma indicates that it is younger than the South Mountain granodiorite, but may reflect thermal evenrs related to Cu-U mineralization in the Ellison Lake pluton.