﻿234 Canadian Record of Science. 



The results of the analysis show that the aiiorthosite 

 from the mouth of the Seine is one of the most basic of 

 the massive rocks, having about 8 per cent, less silica than 

 the typical rocks of eastern Canada, but it is probably 

 wiser to include it among the anorthosites, since the some- 

 what more acid rock from Bad Vermilion Lake links it to 

 the eastern ones. 



It would, perhaps, be most logical to name the whole 

 series of rocks consisting essentially of plagioclase anortho- 

 sites or plagioclasites,^ adopting a binomial nomenclature 

 like that tacitly admitted in the classification of other 

 rocks, such as the granites. We should then speak of 

 anorthite, bytownite, and labradorite anorthosites or plagi- 

 oclasites ; and the list might require to be extended to 

 include andesine and oligoclase rocks, perhaps also albite 

 rocks. The albitites described by Turner from California, 

 under the head of syenites, are dike rocks apparently, and 

 should, perhaps, not be classed with the plutonic rocks 

 referred to here.'' The name anorthosite has priority, but 

 has a very tautological sound in the term describing the 

 rock just discussed, anorthite anorthosite. 



Lawson looks on the anorthosite and granite areas of 

 Bad Vermilion Lake as representing the truncated base of 

 a Keewatin volcano which served as one of the vents for 

 the pyroclastic materials so widely found in the Keewatin 

 rocks of the region, the basic rock coming first and the 

 acid afterwards.'^ In this he is probably not correct, for 

 there is good evidence to show that the anorthosite, which 

 probably solidified under a considerable thickness of super- 

 incumbent rock, was so far exposed by denudation that 

 fragments of it could be rolled into boulders and become 

 part of a conglomerate before the eruption of the granite. 

 The latter rock has sent apophyses into the anorthosite^ 



1 See Viola as quoted by Roseubiiscli in Massige Ge.steiiic, Eiste Halfte, p. 298. 



2 American Geologist, June, 1896, p. 379, etc. 



3 Geol. Sur. Can., loc. cit. 



