THE GOWGANDA LAKE DISTRICT, ONTARIO 



665 



tion by some sort of "transfusion."^ It has the same composition 

 (albite and quartz, with some chlorite and garnets) as the adinole. 

 In the' diabase near this contact aplitic veins, consisting essentially 

 of albite and quartz, are especially numerous. 



LILY LAKE SILL 



The diabase to the southwest of Lily Lake has often a high pro- 

 portion of "red spots." On the north boundary of H.S. 646,^ 

 (A, Fig. 3) is found a variety which in the hand specimen would be 

 termed a syenite. It is, in fact, composed almost entirely of the 

 granophyric material which forms the "red spots." Under the 

 microscope it shows phenocrysts of albite in a graphic intergrowth of 

 quartz and feldspar, with a tendency to radial arrangement about the 

 phenocrysts. The feldspar of the graphic growth is often in con- 



FiG. 3. — Ideal section at Lily Lake. si. = slate; di. = diabase 



tinuous orientation with the phenocrysts. Sometimes the albite 

 twinning lamellae pass from the phenocrysts into the feldspar of the 

 micropegmatite without interruption. A very small proportion of 

 the feldspar of the graphic material is a microperthite. Chlorite, 

 apatite, iron ore, and calcite are present in small amount. The 

 rock is a typical granophyre. 



There is a small patch of thinly laminated graywacke slate within 

 thirty feet of the outcrop of this granophyre. It evidently overlies 

 the granophyre, but the two could not be found in contact. Some 

 of the slate is altered by the intrusive into a rock with alternating 

 dark greenish chloritic and reddish feldspathic laminae. Other 

 parts of the slate are less altered and some apparently unaltered. 

 Some chemical determinations made in samples of the altered slate 

 will be given later. 



1 A. Harker, Natural History of the Igneous Rocks (1909), 304. 



2 See map by A. G. Burrows, Ontario Bureau of Mines, 1910. 



