CRYSTALLINE SCHISTS OF DOUBTFUL RELATIONS, 395 
the rocks in these districts, as compared with the unfolded condition of the 
Penokee and Animikie beds. 
CRYSTALLINE SCHISTS OF DOUBTFUL RELATIONS. 
The original Huronian, the Animikie slates, the Penokee iron rocks, 
and the iron-bearing rocks of the Marquette and Menominee regions, ap- 
pear to me, then, in all probability to belong together, and I may hence 
properly call them all Huronian. In each of the regions mentioned the areas 
of Huronian schists are limited by granite and gneiss. Commonly, when a 
contact of the schists with the gneiss and granite is to be seen there is more 
or less strong evidence of unconformity, and in all cases—save that of the 
so-called Huronian granite of Brooks and Wright, in the Menominee region 
of Wisconsin—the gneiss and granite plainly rise from beneath the schists. 
There are, however, a number of other areas and belts of crystalline schists, 
on all sides of Lake Superior, whose relations to the Huronian and to the 
older gneisses are in greater or less doubt. The doubt arises in some cases 
from a very imperfect knowledge of the rocks in question; but in others 
comes either from the structural difficulties involved in connecting these 
areas with the undoubted Huronian; or from greater or less contrast litho- 
logically with the recognized Huronian; or from the difficulty in distin- 
guishing between eruptive and non-eruptive granites. It is wholly pos- 
sible that some of the granites are eruptive and relatively new, while others, 
and especially those distinctly connected with the gneisses, may be of some 
sort of not understood metamorphic origin. 
The whole question of the nature and relations of these ancient rocks 
is in great confusion. It seems to be an open question as to whether there 
are schistose rocks belonging with the so-called Laurentian gneisses and 
granites in the Lake Superior region or not. The later Canadian geologists 
—especially Robert Bell—have worked on the latter view, and have de- 
scribed and mapped as Huronian all schistose rocks not distinetly gneissic, 
whether in apparent conformity to the gneiss or not. Nearly complete 
ignorance as to the true mineralogical nature of many of these doubtful 
schists adds another element of uncertainty to the question. ‘The diorites 
and diorite-slates described by Bell as occurring in the Huronian north 
