. PRE-CAM BRIAN ROCKS OF NEWFOUNDLAND 461 



Basalts attain a tremendous development along Colliers Bay, 

 extending south toward Brigus Junction. They are associated 

 with a great development of basaltic breccias and often exhibit 

 amygdaloidal or flowage structures. The flows are very much 

 altered throughout and may be chloritized with resultant green- 

 gray rocks, or hydrated and thoroughly impregnated with iron oxide 

 giving purplish- or reddish-brown hues. These alterations are 

 probably due to thermal waters, as they occur independent of what 



Fig. 7. — Coarse rhyolite breccia; about two and one-half miles south of Man- 

 uels, Conception Bay. Photograph by G. v. I. 



might be expected as the result of weathering. In texture they 

 vary from felsitic to finely porphyritic, and in thin section show a 

 felt of plagioclase laths or microlites with a distinct fluxion structure 

 in a chloritic or indistinct altered groundmass. Chlorite pseudo- 

 morphs, replacements of some ferromagnesian mineral, possibly 

 augite, occur as abundant minute phenocrysts in some flows. 



The breccia beds exhibit a varied assortment of colors and a wide 

 range in the diameter of their component fragments ; but by far the 

 predominant portion of the rhyolitic breccias are various hues and 

 tones of reddish- and purplish-gray, whereas the basaltic breccias 



