394 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
one point near Marquette, their descriptions show to be a mere phase of the 
diorite rich in orthoclase, and therefore, inferentially, a uralitic orthoclase- 
gabbro or diabase. Gneiss may be excluded from the list as being more 
than doubtfully Huronian, when a true gneiss,’ or as being a mere phase 
of the mica-schist such as occurs also in the Penokee upper mica-schists. 
Granite occurs in large areas only in the Menominee region, where it has 
not been satisfactorily shown to be Huronian, and may be eruptive. The 
sericite-schist appears to be very close to some of the rocks of formation IIT 
in my descriptions of the Penokee Huronian,” and is very probably repre- 
sented among the slates of the Animikie Group on Pigeon River. The jas- 
per- and chert-schists are of course found also both in the Animikie and the 
original Huronian. Of the amphibolites the actinolite-schists and magnetitic 
actinolite-schists are known also in the Penokee region. Hornblende-rocks 
have also been described as occurring in the Penokee region,’ but a schistose 
hornblende-rock has not been noticed there. Whether any of the massive 
hornblende-rocks here included are altered or uralitic diabases I am at pres- 
ent unable to say. Augite-schist is also mentioned as occurring at one 
point in the Marquette region.* Whether the hornblende-schists have any 
relation to it is not known. The chlorite-schists of the Marquette region 
belong to two distinct classes, of which one type plainly belongs with the 
greenstones as an alteration form, while the other may possibly be con- 
nected with the micaceous and hornblendic schists. 
It thus appears that the Marquette and Menominee iron-bearing schists 
are essentially the same, lithologically, with those of the Animikie Group of 
the North Shore. Of the few unusual kinds of the Marquette and Menom- 
inee regions some may be attributed merely to metasomatic changes, while 
the remaining ones are possibly to be attributed to the processes of meta- 
morphism,° which in turn may be connected with the complex folding of 
1 Geology of Wisconsin, Vol. III, p. 529. 
2? Geology of Wisconsin, Vol. III, p. 111. 
3 Geology of Wisconsin, Vol. III, pp. 137, 252, 288. 
*Geology of Wisconsin, Vol. III, p. 645. 
’ Brooks (Geology of Wisconsin, Vol. III, p. 521) regards these greenstones as metamorphic, but 
Wichmann has shown plainly (bid., p. 627) that this position is untenable; and I have convinced 
myself from my study of the Keweenawan and Animikie greenstones that all are of the same origin and 
all eruptive. 
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