386 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
ites and quartz-slates. In the Animikie Group these alternate with great 
interbedded flows of diabase and gabbro, and are intersected by great num- 
bers of dikes of the same rock, the equivalents of which are to be found in 
the interbedded and intersecting diabases of the South Shore Huronian. The 
thickness of the Animikie rocks is a great one, and is comparable only with 
that of the South Shore Huronian. The affinity of the Animikie rocks is 
especially strong with the schists of the Penokee Range of Wisconsin, and 
these I have elsewhere shown to be essentially the same as the iron-bearing 
schists of Marquette. The Animikie series presents the smallest number of 
rock kinds, the Penokee series a larger number, and the Marquette and Me- 
nominee Huronian the most. Some of these differences may be made to 
disappear on closer study of the still quite imperfectly known Animikie rocks; 
while much of the greater variety in rock kinds on the South Shore is the 
result of metasomatic change upon the included eruptive rocks. Even the 
“diorites” of the South Shore Huronian are in all probability merely altered 
diabases. The greater variety in the kinds of schistose rocks is directly 
connected with greater amount of disturbance, and is the result of the obscure 
and ill-understood process known as metamorphism. 
THE ORIGINAL HURONIAN. 
The original Huronian of Logan and Murray forms the north shore of 
Lake Huron from the Saint Mary’s River eastward. Logan’s description of 
1863' makes the rocks have a total thickness of 18,000 feet, composed as 
indicated in the following scheme, which is given in ascending order:* 
Feet. 
1. Gray quartzite, thin bedded in some parts; the thickness is very doubtful, 500 
2. Greenish, red-weathering chloritic and epidotic slates, interstratified with 
trap-like beds; of this mass also the thickness is very doubtful,..... 2, 000 
3. White quartzite, the color sometimes passing into gray; the rock is princi- 
pally fine grained, but the granular texture is often lost, and great 
masses of it become vitreous quartzite. The rock on the other hand 
often becomes coarse grained and assumes the character of a conglom- 
erate from the presence of pebbles, consisting chiefly of white quartz, 
varying from the size of duck-shot to that of musket-balls. The beds, 
which are generally massive, are frequently separated by layers of 
fine grained greenish-gray siliceous slate, and considerable masses of 
greenstone are frequently intercalated in different parts of the whole 
thickness, 266+ 262.5 line viaieleclee ech See Eee ee eee eee 1, 000 
1 Geology of Canada, 1863, p. 55. 
