PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 317 



Arkose. Quartz.] 



One of the variations of the rock of the region. 



One section. 



Age. Archean (igneous). N. H. w. 



No. 322. ARKOSE. 



Oak portage, on the international boundary at the west end of Saganaga lake; S. E. 'X N. E. % sec. 24, 

 T. 66-6 W. 



Ref. Annual Report, ix, page 85. Same as No. 565 (W.) ; Annual Report, xvii,page 213; Nos. 2031-2045, 

 Annual Report, xxiv, pages 18-22. 



Meg. Rather fine grained; composed of angular grains of quartz and feldspar 

 in an apparently feldspathic background. 



Mic. The section shows angular grains of quartz, also some of much decayed 

 feldspar. Between these grains is a dirty, almost opaque, isotropic, gray or yellowish 

 material. It in part appears like decayed feldspar and sometimes the feldspar grains 

 are not sharply set off from this material but seem to grade into it. A little pijrite 

 is present. 



One poor section. 



Age. Archean (Keewatin). 



Remarks. This rock is regarded as an arkose, whose elements have been 

 obtained from the adjoining granite, and it may thus be termed a recomposed granite. 

 This is not the place to discuss the relations of the Saganaga granite to the sur- 

 rounding rocks. It may, however, be stated that here (west side of Saganaga lake) 

 the rocks change from granite to elastics (slates, graywackes and recomposed 

 granite). These elastics are of a later date than the granite and the rock here 

 described (No. 322) represents part of the base of the elastics composed of debris 

 derived immediately from the adjoining granite, and not water- worn. The granite 

 may have been in a semi-decayed state when this rock was formed from it. u. s. G. 



No. 323. QUARTZ SCHIST. 



Oak lake, north side, which is the first lake west of Saganaga lake on the international boundary. The 

 shores of this lake are composed of this rock. 

 Ref. Annual Report, ix, page 85. 



Meg. Gray or greenish-gray schist, having a structure which is due apparently 

 to pressure and shearing. 



Mic. The section is largely made up of microgranulitic clastic quartz, in the 

 midst of which is strewn a large amount of chlorite, which, being in shreds or fibro- 

 lamellar, renders the field nearly dark constantly between crossed nicols. There is 

 also some calcite and some hematite. The structure may have been produced in part 

 by shearing, but the rock is evidently a clastic one. 



Two sections. 



Age. Upper Keewatin. 



