BY M. AUROUSSEAU. 2ff3 



contorted; it is then often associated with pegmatites, and may 

 be intruded lit par-lit by amphibolite. The contortion is well 

 shown in some cliffs on tlie north side of the Brunswick River 

 Valley, near post 1997 on the Narrogin railway. A zone of con- 

 tortion seems to run S.W. through this point, as it is met in 

 several places south of the river too. 



l^he Pegmatites are widely distributed, but are not abundant. 

 In the hills south-east of Olive Hill Siding, they are associated 

 with masses of a green, actinolitic mineral, and an earlier, talcose 

 mineral, both as yet undetermined, the latter probably being a 

 pseudomorph. These minerals also occur in the pegmatite-out- 

 crops on the south side of the small valley beyond Flaherty 

 Brook, S.E. of Roelands quarry. 



The relations between the granodiorite, gneiss, and basic 

 dykes, were most clearly shown in the Roelands quarry. Numer- 

 ous dykes were exposed, some of which wei'e foliated. In many 

 places, in the main quarry, the granodiorite Was seen to pass, in 

 the direction of a basic dyke, by imperceptible gradations, into 

 a fine-grained gneiss bordering the dyke, its foliations running 

 parallel to the dyke, which was also slightly foliated, the edges 

 being biotite-schist. Undoubtedly the gneiss is derived locally 

 from the granodiorite, and its formation is connected with the 

 basic dykes. At the south end of the quarry, a section was ex- 

 posed showing three parallel dykes; between the first and second 

 from the east, the granodiorite was unaltered, but between the 

 second and third was a highly contorted gneiss, with a few 

 felspar- phenocrysts. 



The change from porphyritic granodiorite to fine-grained gneiss 

 is very definitely shown by the felspar-phenocrysts, in the follow- 

 ing; arbitrary stages in the transition : — 



1. Unaltered, porphyritic granodiorite; phenocrysts not 

 oriented. 



2. Phenocrysts fluidally oriented. 



3. Phenocrysts fiuidally oriented, and crushed peripherally. 



4. Phenocrysts fluidally oriented, elongated and distorted. 



5. Phenocrysts dragged out, and crushed into long streaks of 

 granular felspar. 



