E/MJ : engineering and mining journal . ocks of formation lyingbetween dikes and between traverse faults have mostprobably acted as units. They can be regarded as theindividual gigantic stones making up a great piece ofmasonry. As this masonry was tilted and settledand sheared, the resulting stresses on the individualunits would break some of them and possibly compressothers; some would be made more porous and someless so. The effect of this action cannot be observed;it can only be deduced from a mechanical considera-tion of what must have happened when the formationwas faulted. However, it se
E/MJ : engineering and mining journal . ocks of formation lyingbetween dikes and between traverse faults have mostprobably acted as units. They can be regarded as theindividual gigantic stones making up a great piece ofmasonry. As this masonry was tilted and settledand sheared, the resulting stresses on the individualunits would break some of them and possibly compressothers; some would be made more porous and someless so. The effect of this action cannot be observed;it can only be deduced from a mechanical considera-tion of what must have happened when the formationwas faulted. However, it serves to explain why cer-tain blocks of the formation contain ore and othersdo not; why between one pair of dikes there is goodore and between the next pair there is none, and whyan orebody extends a certain distance along the strike,and the same beds which carried the ore are utterlyunleached a few hundred feet farther along the mechanical effect on the various blocks of theformation cannot be foretold at present. It simply. FIG. 33. CROSS-SECTION SHOWING AN OREBODY DE-VELOPED ALONG THE GREAT BEDDING FAULT aids in understanding the facts after they are dis-covered. In concluding the discussion of the origin and oc-currence of the ore deposits, it may be well to sum-marize the matter briefly. In form the orebodies arelong, spindle-shaped bodies, or flat tabular are found chiefly in six different horizons, butany part of the iron formation may alter to ore. Theprincipal factors controlling form and localizationare: First, the character of individual beds, porosityand original richness in iron; second, the structuralfactors, dikes, foot wall, and faults; and, third, thetopography and climate of the geologic time just afterthe formation was tilted to its present these controlled the water circulation, which hasbeen the effective agent in altering the iron formationto ore. Most of the exploration on the Gogebic Range isdone by underground work,
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectmineralindustries
