THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 39 



localities. Plate 4, upper figure, shows a very tight fold with numer- 

 ous associated minor crenulations. In another case, its viscosity 

 was locally low enough to allow^ it to surround a small piece of 

 limestone which was broken from a thin interbedded calcareous 

 stratum (see figure 6). The garnet gneiss in this case is itself a 

 xenolith, or nearly so, in granite gneiss. 



The plasticity of the garnet gneiss is therefore seen to be its most 

 prominent physical feature, imposed upon it by the conditions of the 

 zone of flowage in which the deformation took place. Under these 

 conditions its deformability has always proved itself to be greater 

 than that of amphibolite, and on a rare occasion, as just described, 

 even exceeds that of limestone. Accordingly, the probability of the 

 sedimentary origin of the garnet gneiss, established on purely litho- 

 logic grounds, is not diminished by the pseudo-igneous relations 

 occasionally assumed by the formation toward its associated am- 

 phibolite " inclusions." These relations are seen to be a function 

 of the physical conditions of the zone of flowage in which the 

 Grenville rocks were deformed ; and the ability of the garnet gneiss 

 formation to simulate igneous relations toward the more competent 

 basic intrusive sheets, would seem to be amply demonstrated. 



The admixture of the belt of garnet gneiss with later granitic 

 material is much closer than with the amphibolitic ; it is even so 

 minute as to affect almost every ledge within its area. Indeed, 

 much of the quartz and feldspar of the light-colored streaks in the 

 occurrence already described as typical garnet gneiss, may have 

 originated in subsequent pegmatitic injection during the granite in- 

 trusion, although in the cases cited the rock is as free as may be 

 from such igneous contamination. 



Practically all the garnet gneiss throughout the entire flexure is 

 in reality a soaked rock. Plate 7, upper figure, where the white is 

 fine-grained pegmatite in garnetiferous country rock, illustrates the 

 minuteness to which the injection may be carried. There is evidence 

 that this admixture may even be of microscopic fineness in much of 

 the area. If this is so, the introduction of such a large quantity of 

 granitic material into the garnet gneiss may well have operated to 

 decrease the viscosity of this rock during the process of deforma- 

 tion, and to have facilitated the flowage to which in its purer phase3 

 it seems naturally to have been prone. 



It seems particularly unsafe, in view of the extreme deformation 

 to which tectonic disturbances have subjected the Precambrian rocks 

 of this quadrangle, to attempt a correlation of any of the separate 

 garnet gneiss areas described above. There is, however, a feature 

 in the distribution of certain of these isolated occurrences which is 



