DISTURBANCE AND ITS EFFECTS. 319 



scales and also feldspar are usually present in small quantities. A speci- 

 men of this rock was obtained from the north shore of Archie bay, four 

 miles from the contact, which might be regarded as a typical specimen 

 of the less altered rock. A thin slice of this Avas examined under the 

 microscope by Dr A. C. Lawson, who says: 



"A tine-grained, light yellowish-gray qnartzite, rust-stained in places ; under the 

 microscope it is seen to be a crashed quartz sandstone; a cataclastic condition is 

 seen to have been induced upon the original epiclastic grains of quartz ; wavy ex- 

 tinction is common. There is a rude parallel arrangement of the quartz grains in 

 long areas, and between the constituent grains is a fine cement which is largely 

 made up of a felt- work of muscovite. In some portions of the slide this felt-work 

 of muscovite is mixed with clastic grains of quartz and forms a base in which the 

 larger clastic grains are embedded. Besides quartz, there is present a notable pro- 

 portion of fragments of feldspar." 



Disturbance causes Change of Strike. — About three miles from the contact 

 with the gneiss these Huronian quartzites show signs of great disturbance, 

 and the strike which has hitherto been nearly east and west turns 

 abruptly to the southeast, this change being still further continued till 

 the strata have assumed a southwesterly strike, thus corresponding with 

 the line of outcrop of the gneiss in this direction. A little to the north 

 of the eastern end of Lake Panache and emptying into it is Gabodin 

 lake, about two miles in length. At the western end or outlet of this 

 lake micaceous quartzites were noticed with a strike of N. 75° E., which 

 curves around quickly, for on the islands in the eastern part of the lake 

 quartzose mica schists were seen striking N. 15° E., these rocks being thus 

 conformable with the line of outcrop of the gneiss in its northerly con- 

 tinuation. 



Alteration in Character of Rocks accompanies Change of Strike. — This 

 rapid change in the strike of the quartzites is accompanied by a very 

 marked alteration in the character of the rocks themselves. The gran- 

 ular quartzites and sandstones which have previously shown no further 

 signs of alteration than a hardening consequent on the addition of sec- 

 ondary silica are now metamorphosed into very typical quartzose mica 

 schists. The change is gradual but marked and extends to a distance 

 of three miles from the line of junction. 



Microscopic Examination of altered Quartzite. — Dr Lawson examined two 

 slides of this qnartzite under the microscope. Of the first he says : 



"A light gray, fine-textured, somewhat micaceous quartzite, with occasional 

 'sheen surfaces' along shear planes. Under the microscope the rock is seen to be 

 an aggregate of subangular or rounded quartz grains with a subordinate proportion 

 of feldspar grains, most of the latter being quite fresh and showing the multiple 

 twinning of plagioclase. Some of this plagioclase is clearly in original clastic grains, 

 but some appears to be of secondary interstitial growth. Scattered throughout the 



