. The Vermilion iron-bearing district of Minnesota : with an atlas . y corresponds in trend with the strike of tlie formation itself,and on its south and west sides lies next to the iron formation, the bandedjaspers. As the ore body is followed westward, the ore is gradually moreand more mixed with jasper, becoming lean ore, and then the stringers of «The iron-ore deposits of the Lake Superior region, by C. R. Van Hise: Twenty-tirst . U. S. Geol. Survey, Pt. Ill, 1901, pp. cit., fig. 8, p. 42. SOUDAN FORMATION. 231 ore continue into the jasper, grower fewer and thinner,
. The Vermilion iron-bearing district of Minnesota : with an atlas . y corresponds in trend with the strike of tlie formation itself,and on its south and west sides lies next to the iron formation, the bandedjaspers. As the ore body is followed westward, the ore is gradually moreand more mixed with jasper, becoming lean ore, and then the stringers of «The iron-ore deposits of the Lake Superior region, by C. R. Van Hise: Twenty-tirst . U. S. Geol. Survey, Pt. Ill, 1901, pp. cit., fig. 8, p. 42. SOUDAN FORMATION. 231 ore continue into the jasper, grower fewer and thinner, until finally the ironformation consists almost exclusively of jasper and chert, with but isolatednarrow layers of ore in it. The banding of the jasper is seen to be con-tinuous with that of the ore, which still possesses a banding, though animperfect one. At one place on Soudan Hill, north of open pit No. 6, a contortedbanded iron formation is cut by a dike which runs nearly north and south,cutting across the bands of the formation (fig. 12). On the east side of. Fig. 12.—Reproduction of sketch showing replacement oi jasper by iron ore. After Smyth and Finlay. the dike and between the dike and the jaspers and cherts there has beenformed a small ore deposit. Here the banding in the adjacent jaspers andcherts appears to run right on through the ore, and although interrupted bythe dike is found to be continuous beyond this. At Ely the rock has been very much brecciated, but even there thebanding in the ores and their intimate mixture with the bands of jasperseem to show very conclusively that their relation is essentially the sameas that of the ores and jaspers at Tower and Soudan which have been a Reproduced from The geological structure of the western part, of the yermilion range, Minne-sota, by Smyth and Finlay: Trans. Am. Inst. Min. Eng., Vol. XXV, October, 1895, p. 643. 232 THE VERMILION IRON-BEARING DISTRICT. described above. The only explanation as to the origin of the
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