THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 87 



at this stage of its consolidation, was easily forced into the spaces 

 which the disruption of the xenolith tended to produce. An even 

 earlier stage in the fracturing of a xenolith can be observed on the 

 same road a few rods southwest of this outcrop. The schist occurs 

 in a narrow band about 50 feet long and 2 to 2^ feet wide, inclosed 

 in normal pink granite gneiss. The conditions are generalized in 

 figure 19. A great number of transverse cracks have developed in 

 the amphibolite, and into these the pegmatitic material was squeezed 

 and crystallized in veinlets up to 3 inches in width. The numerous 

 parts of the inclusion -have not as yet been pulled apart by move- 

 ments in the magma, and in consequence the general structure and 

 appearance is that of a ladder, the rounds of which are of white or 

 pink quartz-orthoclase pegmatite. 









a 





b 



¥m 













Fig. 19 Early stage in the breaking up of a sheetlike xenolith of amphi- 

 tolite. A number of regularly spaced cracks have occurred which have 

 opened a few inches on one side and allowed the pegmatitic juices to strain 

 into them; the second half is generally closed or nearly so, and extends 

 at right angles to the first. Near one end of the exposure slipping has 

 taken place in the xenolith with displacement of a few inches, and pegmatite 

 has accumulated here, as in the other fractures. The granite is not faulted, 

 and a wide difference in the viscosity of the two rocks is indicated. Inclusion 

 is about 2 feet wide, and strikes northeast, (a) Pink granite gneiss, grading 

 into pegmatite; (b) amphibolite. 



One and one-third miles east of Eddy, at roadside one-fourth of a mile 

 southwest of schoolhouse. 



An intermediate stage, and an even more striking illustration of 

 this phenomenon than either of these occurrences, is to be seen on 

 the east wall of Tupper's quarry, in the middle of the granite area, 

 three-tenths of a mile northeast of the north edge of Canton village. 

 Here the east or footwall of the quarry exposes the westward-dip- 

 ping surface of a thin fractured mass of black hornblende schist 

 (see plate t6, upper figure). The sharp angular fragmentation of 

 the latter, and the filling of the rectilinear interspaces with coarse 

 granitic material, is as good an indication as is to be found in the 

 quadrangle of the xenolithic character of the black amphibolite. 



