Vol. 52.] FOLIATED GRANITES IN EASTERN SUTHERLAND. 637 



is sparingly developed. They contain orthoclase, oligoclase, quartz, 

 and occasionally biotite. Indeed, the remarkable feature of the 

 granitoid rocks as a whole, both in the case of the larger masses 

 and in the granitoid folia, is the abundance of oligoclase. A 

 specimen taken from a locality about 100 yards from the edge of the 

 cliff S.S.E. of Kirktomy Point, in which the granite-bands can 

 be seen cutting across the folia of the darker granulitic rock, 

 shows under the microscope that the granitic bands consist of 

 quartz, oligoclase, and orthoclase, with garnet and apatite as 

 accessories. So minute are these layers of granitic materials that 

 in some instances they do not exceed J inch in breadth : and hence 

 in a specimen, say a foot across, there may be several granitoid 

 bands alternating with layers rich in biotite or with granulitic bands 

 containing quartz, felspar, and mica. It is further observable that 

 the granitoid folia follow the various folds, and even the minute 

 puckerings of the biotite-gneiss and the granulitic gneiss, without 

 any apparent crushing or deformation of the constituents. The size 

 of the grains does not vary with reference to the margin of the band, 

 and there is no trace of chilled margins. Still more noteworthy is 

 the fact that along the junction-line separating the granitoid from 

 the other folia the minerals interlock just as they do in the interior 

 of the different folia. 



It is obvious that these phenomena do not resemble those of an 

 igneous rock penetrating pre-existing strata along cracks and 

 fissures where chilled margins may be readily detected. Indeed, an 

 unbiased observer would almost infer at first sight that the 

 granitoid bands are not in reality later than the gneisses and schists 

 which they traverse. But in many excellent sections the quartzo- 

 felspathic folia, which are identical in structure and composition 

 with the quartzo-felspathic portions of the larger granite-masses, 

 can be seen branching from the latter and following the contorted 

 foliation-planes of the pre-existing strata. It seems reasonable to 

 infer, therefore, that these igneous materials were introduced when 

 earth-movements were in progress and when the pre-existing rocks 

 were at a high temperature. 



Throughout the area, numerous lenticles of granulitic schist occur 

 as isolated masses in the foliated granite, the foliation of the schist 

 being parallel to that of the granite. An excellent example is met 

 with on the shore south of Uamh Dhom near Pollsain, east of 

 Kirktomy Point. Here small lenticles of highly siliceous schist of 

 the ' Moine ' type occur, with the planes of schistosity parallel to 

 that of the granite. This instance further shows minute granitoid 

 folia branching from the main mass and traversing the foliation- 

 planes of the inclusions of granulitic gneiss. Under the microscope 

 this siliceous schist or gneiss is composed of quartz, felspar, and 

 biotite, with garnet as an accessory. Some of the quartz occurs as 

 irregular patches. 



In the belt of garnetiferous biotite-schist or gneiss extending 

 southward from Kirktomy Bay to Creag Meadie, foliated granite 

 and pegmatite occur as lenticular masses varying from a few feet 



2 x 2 



