PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 667 



Syenyte.] 



Mic. Has a great abundance of augite, considerable biotite, sphene, and large 

 cqifitites. In this slide, where the augites are numerous, not only are some of the 

 small ones entirely enclosed in the old feldspars, but several of the larger augites are 

 seen to break the feldspar boundaries in a poikilitic manner, and the biotite does the 

 same, while the biotites are pierced by spicules of actinolite, and broken by the 

 augite. One section. 



Age. Archean (Keewatin). N. 11. w. 



Iteiiia >/.-. This rock represents the " poikilitic phase " of the granite as described 

 by Grant in the Twenty-first Annual Report, page 50 (compare No. 574G). While 

 the rocks Nos. 1105 and 1106 have certain characters that show them closely related 

 petrographically, they are seen in the field to be one intrusive in the other, as thus 

 described in the Twentieth Annual Report, page 74: 



There is an island in the N. W. '4 X. W. % sec. 2, T. 64-7, which is made up mostly of the pyroxene granite 

 (Xo. 573G); this varies somewhat in grain, but none was seen as tine as No. 571G; it is noticeably porphyritic 

 with reddish feldspars. On the west side of the island near the north end is a rock with a green aphanitic 

 groundmass in which are numerous glistening biotite scales (No. 574G). This rock is seen in contact with the. 

 granite: the contact line is sharp and distinct. The green rock is cut by many vein-like forms of a purple rock 

 which is seen to be part of the granite, but they were not actually traced into the granite. No. 575G shows this 

 rock in contact with the green rock. On a microscopic examination No. 575G is seen to be part of the granite 

 The two rocks were not apparently changed near the contact. Many angular and rounded fragments of the 

 green rock are seen in the granite and a few fragments, or what appear to be such, of the latter are seen in the 

 green rock. The evidence of this exposure points to the more recent age of the granite. 



The rocks about Kekequabic lake can be divided petrographically into three 

 groups, as follows: Group I, Nos. 1061, 1094, 1105, which are distinctly porphyritic 

 with augite (and hornblende) and feldspar. These are at the narrows of the lake 

 and on the little island northeast of Animikie island. There is reason to believe, 

 contrary to the opinion of the writer when the Held observations were made, that this 

 is an igneous rock in its present structural relations, and that it originally existed in 

 other regions adjacent. It is probably a phase of the granite represented by the 

 first numbers of group II, below, both being intrusive in the green schists of Keke- 

 quabic lake, and into the crystalline conditions of that green schist. 



The second group includes Nos. 1044, 1045, 1046, 1051, 1052, 1100, 1101, 1104, 1106. 

 These are rather granitic in texture, and, judging from their geographic distribution, 

 which is nearest the strike of the gabbro, as well as from their petrographic features, 

 they may be referred to a recrystallization of older elastics more or less mingled with 

 volcanic detritus, perhaps at the time of the gabbro revolution. These may again 

 be separated into two sub-groups by excluding Nos. 1101, 1104 and 1106, which are 

 green with much hornblende. 



The third group is non-crystalline debris, or less crystalline than the last, and 

 includes the following: Nos. 1047, 1048, 1049, 1050, 1055, 1057, 1058, 1059, 1060, 1093, 

 1098 and 1099. 



