PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 917 



Greenwacke. Dioryte.] 



Age. Archean (Keewatin). 



Remark. The field relations show that this rock was intrusive in the gray wacke 

 of the region. Its great alteration shows to what extent original diabases or dolerytes 

 are transformed; /. e., unless the rock be a regenerated basic debris compelled to act 

 as an intrusive by dynamic folding and fracture. N. H. w. 



No. 12H. GREENWACKE. 



South side of the island in S. W. % sec. 32, T. 63-16, Vermilion lake. 

 Ref. Annual Report, xv, pages 299, 414. 



Meg. Cut by dikes of greenstone; a green, coarse rock. 



Mic. Uralitized and chloritized augites, lie in a debris of the same material. 

 In the finest material is apparently a little feldspar and a noticeable amount of cpidote. 

 One section. 



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



No. 15H. DIORYTE. 



Near the township line, in N. W. % sec. 7, T. 62-16, Vermilion lake. 

 Ref. Annual Report, xv, pages 284, 285, 415. 



Meg. Heavy, massive, greenish black, probably a dike. 



Mir. Principally composed of coarse hornblende and of feldspar interlocked in 

 a somewhat igneous fashion. The feldspar is considerably broken and reconstructed 

 by new growths, but shows still, in the main, the sizes and forms of the original 

 crystals. The hornblendes are secondary after pyroxene, and in numerous instances 

 they show the usual differences of polarization which indicate approximately the 

 forms of the original pyroxene grains. Calcite, epidote, magnetite, biotite and Muscovite 

 appear in accessory amounts. One section. 



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



No. 17H. GREENWACKE. 



S. W. y S. E. % sec. 1, T. 62-17, from the point, Vermilion lake. 

 Ref. Annual Report, xv, pages 285, 415. 



Meg. Greenish, siliceous schist. 



Mic. Schistose. The rock is quite fine grained, but long-drawn bands of horn- 

 blendic debris give it a strong parallelism of schistosity, while epidote in fine, gran- 

 ular, mostly isolated individuals, is very numerously distributed, but somewhat in 

 lines parallel with the schistosity. The finely granulitic matrix is of quartz and 

 feldspar of later date than the hornblendes, but the epidote is earlier than the horn- 

 blende. There are but very few, if any, sericite scales. One section. 



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



No. 19H. DIORYTE (with sphene). 



Sec. 3, T. 62-17, Vermilion lake. 



Ref. Annual Report, xv, pages 286, 287, 415. 



Meg. In hills and ridges that alternate with hills of mica schist along the shore. 



