THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 6/ 



island one-quarter of a mile down stream from the lower bridge in 

 Canton village, with a white, tourmaline-bearing pegmatite exposed 

 on the west side of the Canton-Eddy road nine-tenths of a mile 

 northeast of Eddy. 



It should also be noted, however, that a number of white dikes 

 and '' flammen " are found in noncalcareous country rocks as, for 

 example, in those garnet gneisses which are more or less soaked 

 with white or grayish pegmatitic material ; and that therefore lime- 

 stone may not be the only cause capable of producing this effect. 

 It is possible that the hydatogenic activity postulated to account for 

 the red hematitic pigment coloring the granite took place anterior 

 to the introduction of some of the pegmatite dikes, and accordingly 

 the latter were protected from discoloration by reason of their 

 slightly younger age. That there are at least two distinct periods of 

 pegmatite intrusion is pointed out elsewhere (see page 85), and 

 although it is impossible to establish the hypothesis, a subdivision 

 of the older set might be made, if based on the presence or absence 

 of hematite pigment ; the red pegmatites being separated from the 

 white by a period of circulation of heated iron-bearing solutions 

 which permeated and colored the rock already intruded. 



That there is difficulty, however, in the way of applying this in- 

 tensely hypothetical explanation to a general discrimination of red 

 and white nontourmaline-bearing pegmatites must not be over- 

 looked. The ferromagnesian country rocks, and especially the 

 amphibolite inclusions, have often exerted a marked decolorizing 

 influence on the surrounding granite, as noted above, and the 

 extent to which a similar action may have taken place on the net- 

 work of interlacing pegmatite stringers, assuming them to have 

 carried hematite, is indeterminable, though probably not wholly 

 negligible. 



Locally, especially in the smaller lenticles which are of such fre- 

 quent occurrence in the sigmoidal area in the southeastern part of 

 the sheet, the granite is distinctly banded ; layers of normal grain 

 alternate with others that are of coarse, almost pegmatitic texture. 

 This is evidently indicative of primary flow, that is, motion in the 

 intruding magma during the process of crystalhzation. During this 

 time the mother liquor, it is thought, was squeezed irregularly into 

 the partially crystallized mass ; the relatively greater concentration 

 of mineralizing agents in these juices favored crystallization, with 

 the resulting alternations in texture. Plates 10, lower figure, and 

 II, upper figure, show typical occurrences of this phenomenon. 

 5 



