PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 877 



Chlorite schist. Granite.] 



No. 2262. CHLORITE SCHIST. 



A part of rock No. 22GO, on its more northern extension. 

 Ref. Annual Report, xxiv, page 80. 



Meg. A rather fine-grained, greenish-gray schist, with a few larger feldspars 

 disseminated. 



Mic. The section shows a much decayed clastic debris, which originally was 

 constituted of the same materials -as No. 2260, but now is darkened by the prevalence 

 of chlorite, leucoxene and some iron oxide. But it is also lightened by calcite and a 

 little quartz. The " porphyritic " feldspars were chiefly, if not wholly, of plagioclase, 

 but are altered beyond specific determination. The quartz is in fine grains, sharply 

 angular. In places it can be seen that the coarser feldspars have undergone an 

 incipient loose micro-granulitization, with a scant development of fine epidote, but 

 for the most part the feldspars and the finer parts seem to be darkened and disin- 

 tegrated with development of a fine, highly refractive substance which is granular 

 or irregularly spreading. This is in part chlorite, which embraces calcite. Apatite 

 as clastic grains also exists in the rock in small amount, also an isotropic but 

 perfectly transparent mineral, not determined. One section. 



Age. Upper Keewatin. N. H. w. 



No. 2263. GRANITE. 



Near Moose lake, north from the last, on the section line. 

 Ref. Annual Report, xxiv, page 80. 



Meg. Rather fine-grained for granite, gray. 



Mic. The scant coloring elements are chlorite, mingled with some hornblende. 

 There is, besides, a nearly colorless amphibole disseminated in minute fibres through- 

 out the rock. There is a feldspathic and quartzitic background which is closely 

 interlocked, embracing the few dark minerals and a notable quantity of calcite 

 and numerous fine scales of Muscovite. A considerable number of the feldspars 

 are microlitic plagioclase, with nearly parallel extinction and negative elonga- 

 tion as cut, consisting of two to four albite macles; but both these and the 

 larger feldspars, which may be orthoclase, are so related to the muscovite and 

 the calcite that they surround them and appear to be of later date. One 

 section. 



Age. Intrusive in the Upper Keewatin. 



Remark. This fine-grained, holocrystalline rock, with its curious petrology, is 

 believed to be due to a recrystallization of a fine and clastic debris, a transformation 

 which must have taken place simultaneously with the dynamic action which thrust 

 it in the manner of an intrusive amongst its neighboring fragmentals where they 

 were broken or bent so as to give it entrance. N. H. w. 



