PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 869 



Conglomerate. Granite. Porphyry.] 



moreover, there are evidences that this new growth has penetrated and occasionally 

 fresh areas are seen within them, which are like the fresh borders. Two sections. 



Age. Archean. 



Remark. This rock has the characters of several other granites, and especially 

 that at Kekequabic lake, which indicate a recrystallization of an old debris. N. H. w. 



No. 2240. CONGLOMERATE. 



Same place at- No. 2235, north line of sec. 8, T. G3-9, a quarter of a mile east of the northeast corner of the 

 section, and at the same stratigraphie horizon as No. 2230. 

 Ref. Annual Report, xxiv, page I'l. 



Meg. Has a speckled aspect, due to the abundant dissemination of pebbles of 

 quartz-porphyry and of jaspilyte (mostly the former) through a finer matrix of 

 green. Some of the pebbles are also green. Illustrated by figure 1, plate Z, vol. iv. 

 No section. 



Age. Perhaps the base of the Upper Keewatin. N. H. w. 



No. 2243. GRANITE. (Hicropm-phyritic. ) 



On the section line between sees. 4 and 5, T. G3-9, northward from the corner of section 8. 

 Ref. Annual Report, xxiv, page 75. 



Meg. Fine grained, gray, subgranitic; except in the absence of porphyritic 

 phenocrysts of feldspar this rock resembles rock No. 2239. A narrow dike running 

 with the structure in slate and graywacke. 



Mic. In thin section there appear a few scattered porphyritic phenocrysts, one 

 of which, happening to be cut perpendicular to n s and showing the basal cleavage 

 (001), affords an angle of extinction of about 13 which, according to the method of 

 Fouque,* indicates a feldspar between albite and oligoc/ase-albite, n f also being in the 

 acute angle of the optic plane. This particular section shows no albite twinning, 

 but other sections in the same slide show an occasional coarse albite twinning. The 

 rock is considerably altered from -its condition at original consolidation. This is 

 evinced not only by the prevalence of various secondary minerals, notably epidote 

 and mica, but by the microperthitic growth of fresh feldspars in the fissures of the 

 old feldspars. One section. 



Age. Archean (perhaps Upper Keewatin). N. H. w. 



No. 2244. PORPHYRY. (Hombtendic.) 



Near the quarter-section post between sees. 4 and 5, T. 63-9, before crossing the creek at " Nelson's cabins." 

 Ref. Annual Report, xxiv, page 76. 



Meg. Grain and color similar to No. 2243, except that this rock shows a contrast 

 between the fine matrix and the porphyritic crystals. Spreads irregularly as an 

 intrusive in hardened graywackes and slates. 



Contribution a r ttude dos feldspaths des roches volcanic. Bulletin Sncietf Frttit..i<ix< <l< Mineralogie, vol. 17, p. 283, 1894. 



