Significance of tourmaline-rich rocks in the Grenville Complex of St. Lawrence County, New York.

The composition of tourmalines in the metasedimentary and metaigneous lithologies in the Grenville lowlands was studied, and compared with those from mineralised districts for which chemical data are available. The range in the composition of tourmaline found in rocks of different bulk compositions in a possible evaporitic setting is documented, but because of the absence of published analyses of tourmaline in stratabound deposits within evaporitic terranes, the comparisons rely for the most part on tourmaline compositions from the Sullivan Mine, British Columbia. These comparisons and the geologic setting of the study area allow speculation on the genesis of tourmaline-rich rocks and their possible economic implications.
The composition of tourmalines in the metasedimentary and metaigneous lithologies in the Grenville lowlands was studied, and compared with those from mineralised districts for which chemical data are available. The range in the composition of tourmaline found in rocks of different bulk compositions in a possible evaporitic setting is documented, but because of the absence of published analyses of tourmaline in stratabound deposits within evaporitic terranes, the comparisons rely for the most part on tourmaline compositions from the Sullivan Mine, British Columbia. These comparisons and the geologic setting of the study area allow speculation on the genesis of tourmaline-rich rocks and their possible economic implications.