296 DEPARTMENT OF TEE INTERIOR 



2 GEORGE V, A. 1912 



very numerous, so that hundreds of minute clear lenses or droplets of that 

 mineral are contained in a single crystal of the staurolite. The inclusions are 

 almost invariably arranged with their longer axes parallel to each other and, 

 at the same time, parallel to the plane of schistosity of the rock. This orienta- 

 tion of the inclusions appears to indicate that they are residuals of the quartz 

 grains composing the schist before it was thermally metamorphosed; the stauro- 

 lite crystals grew quietly in the rock without causing mechanical disturbance 

 of the pre-existing, schistose structure. Sericitic muscovite, biotite, and quartz 

 form the matrix in which the abundant staurolite lies. These relations of the 

 staurolites to the ground mass find full analogy in the rocks illustrated in 

 figures 88 and 89 of Rosenbusch's Elemente der Gesteinslehre, 1898, p. 498. 

 Abundant twinned crystals of disthene, which do not show inclusions of the- 

 ground-mass often accompany the staurolites. 



Even from the foregoing brief account of the contact action of the Bayonne 

 batholith, it is clear that the exomorphic collar is unusually broad and that the 

 action was correspondingly powerful. To the future geologist who plans to 

 make a thorough study of the collar, interesting results may be promised. 

 The different beds which have been altered should be identified and followed, 

 so as to determine the whole gamut of changes involved in the metamorphism 

 of each, and to find the relation of these changes to distance from the grano- 

 diorite. This work would entail the expenditure of much more time than 

 could be devoted to the study during the Boundary belt survey. The mountains 

 are very rough; the work must, in any case, be time-consuming and arduous, 

 but the result would amply repay the effort. 



SATELLITIC STOCKS ON THE DIVIDE. 



On the main water-parting of the range and just south of the Dewdney 

 trail a granite stock, cutting the middle members of the upturned Summit 

 series, is well exposed. In ground-plan this body is an ellipse with a north- 

 south major axis of 2-5 miles and a width of one mile. One-half mile west of 

 this stock there occurs a small intrusive mass of the same granite which sends 

 a long dike-like tongue northeastward across the Dewdney trail, where the rock 

 is easily studied. 



Petrography. — This granite is medium-grained, of a light pinkish-gray tint, 

 and is noticeably poor in dark-coloured constituents. Quartz, microperthite, 

 orthoclase, a little microcline, and considerable oligoclase, Ab 4 An 1? with a 

 quite subordinate amount of biotite are the essentials; titanite, magnetite, 

 apatite, and zircon are sparingly present. Primary muscovite is accessory and 

 is often regularly intergrown with the biotite. Along the western contact of 

 the larger stock the muscovite becomes so important that the rock may be 

 called a two-mica granite; its structure in this contact zone tends to the panidio- 

 morphic. The average specific gravity of four fresh specimens of the granite 

 Is 2-628. 



