228 
Wisconsin Academy of Sciences , Arts and Letters. 
DESCRIPTION OF PLATE VII. 
Fig. 1. Cross-section of Penokee series. Showing its relations to the 
underlying Archean, the overlying Keweenawan, and the conformable 
succession of its three members. 
Fig. 2. Cross-section of Pence mine, Penokee series, showing the re¬ 
lations of the dike-rock, quartzite, ore-deposit, and drift material. 
Fig. 3. Longitudinal section of a Penokee deposit, looking south. 
The figure shows how, as a consequence of the pitch of the dikes, the 
ore-bodies which reach the rock surface soon pass under the furruginous 
chert. The figure also shows, when one dike is parallel to another or 
nearly so, that the ore-body of the lower dike may pass under that of 
the upper. The vertical distance between the two deposits depends 
upon the horizontal distance between the outcrop of the two dikes and 
upon their pitch. The irregular way in which the ore passes above into 
the chert is seen, as well as a horse of rock at the west end of the west 
open pit. 
Fig. 4. Generalized section of Lower Marquette ores, showing the 
relations of the deposits to the associated formations. Ore is seen at 
the contact of the Upper and Lower Huronion, above a folded mass of 
diorite, upon one or both sides of intersecting dikes, and in a trough 
formed by the union of a dike and a mass of diorite. 
Fig. 5. Vertical cross-section of an ore-deposit of the Marquette dis¬ 
trict. This is bounded below by a synclinal of soapstone grading into 
diorite and above by ferruginous chert. The change from ore to chert 
is not so sharp as drawn. In longitudinal section this body shows a 
considerable pitch. 
Fig. 6. Vertical cross-section of an ore-deposit of Marquette district. 
At the left the ore rests upon soapstone grading into diorite. At the 
right it is upon one side of a dike-rock, the latter being an off-shoot of 
the diorite. At the contact of the two a pitching trough is formed in 
which the ore-body becomes of large size. 
Fig. 7. Horizontal section of ore-deposit on east side of Republic horse¬ 
shoe, Marquette district. The left side of the ore is bounded by a cross 
joint. The right side is bounded in part by a sharp flexure passing 
into a joint, and in part grades into the lean banded jasper and ore. 
