. The Crystal Falls iron-bearing district of Michigan. Iron ores; Geology; Geology, Stratigraphic; Geology, Stratigraphic. THICKNESS OF MANSFIELD SLATF. 65 Till- i'.vi'i-aj^-o dip of tliu beds is 80^, and this gives a maxiumm thickuess (if l,!lO() feet. Toward the south the belt rapidly narrows, initil it is cut out l)y tile intruding (hilerites. A thickness of 1,500 feet is probably not tar from the average. To the east of the ^Mansfield slates is a belt, varying in width up to about 1,200 feet, in which are found large masses of metamorphosed slates, surrounded by intrusive dolerite. In this
. The Crystal Falls iron-bearing district of Michigan. Iron ores; Geology; Geology, Stratigraphic; Geology, Stratigraphic. THICKNESS OF MANSFIELD SLATF. 65 Till- i'.vi'i-aj^-o dip of tliu beds is 80^, and this gives a maxiumm thickuess (if l,!lO() feet. Toward the south the belt rapidly narrows, initil it is cut out l)y tile intruding (hilerites. A thickness of 1,500 feet is probably not tar from the average. To the east of the ^Mansfield slates is a belt, varying in width up to about 1,200 feet, in which are found large masses of metamorphosed slates, surrounded by intrusive dolerite. In this belt the slate masses still show a general north-south strike, with slight variations to the east or west, and a westward dip. One might, perhaps, consider this a slate area which has been ciHn])letely saturated with intrusives. If it should be so considered, this thickness should lie added to the estimated thickness of the slates as above given, but as intrusives predominate in it, the slate being, as it were, merely incidental, I have preferred not to include it in the belt with the slate. t)RK DEPOSITS. Although a great deal of exploring for iron ore has been done in the Mansfield slates, only one lai-ge body of ore has thus far been discovered, in which is the Mansfield mine. This mine is situated on the west liank of the Michi- gamme River, in sees. 17 and 20, T. 43 N., E. 31 W. The mine was apparently prospering wlien, on the nigdit of Septeni- ber 28, 1893, a cave-in occurred, letting in the waters of the jMichigamme River and drowning' 28 miners. N MAI,N SHAFT. For two Lours after the caving occurred, the bed of the river below the mine was bare, the water tlowing into the mine worlviugs. The accompanying tigure, fig. C, prepared by J. Parke Channing, October 8, 1893, shows the relative position of the shaft and the river, and the couceutric- cracks caused by the caving of the mine. (Plan copied from address of presi- dent: Proc. Lake Superior Inst. Min. Eng., Vol. Ill
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishe, booksubjectgeology
