E/MJ : engineering and mining journal . culation more vigorous, on account of the greaterhydrostatic head. The climate of those times wasalso much more arid than at present, and the watertable consequently relatively lower, so that more ofthe formation was doubtless above the permanent levelof the ground water and subject to the action of anabundance of oxygen. Influence of Various Beds on Localization andForm of Ore Deposits The porous or impervious nature of the iron forma-tion, and the amount of the iron oxide originallypresent, are facts which relate themselves to particu-lar beds and stru
E/MJ : engineering and mining journal . culation more vigorous, on account of the greaterhydrostatic head. The climate of those times wasalso much more arid than at present, and the watertable consequently relatively lower, so that more ofthe formation was doubtless above the permanent levelof the ground water and subject to the action of anabundance of oxygen. Influence of Various Beds on Localization andForm of Ore Deposits The porous or impervious nature of the iron forma-tion, and the amount of the iron oxide originallypresent, are facts which relate themselves to particu-lar beds and structural conditions. Some beds arerelatively very porous and permit ready circulationof water. Others are tight and impervious, and thecirculation of water is relatively impeded. Some bedscontained much iron originally, and some little. Someare porous and had much iron in them. Others areporous and contained little iron. Some are tight and FI G. 31. PL.\N OF anOREBODY EXTENDING ALMOST CONTINUOUSLYFROII FOOT TO THE MINE. had much iron, and others are tight and had Httle characteristics of the beds may be tabulatedas follows: 1. Porous with high original iron content. 2. Porous with low original iron content. 3. Impervious with high original iron content. 4. Impervious with low original iron content. In similar structural situations beds of these typesare altered to ore in the order given. It must beborne in mind that any part of the iron formation iscapable of alteration to ore, but it is obvious that atight, lean bed will be the last to be so completelyaltered. In the most favorable situations the whole forma-tion from foot to hanging is altered to ore on a an orebody is shown in Fig. 30, which shows avertical cross-section in the Aurora mine. In planan orebody of this sort has the appearance shown inFig. 31, which shows part of one level in the Pabstmine. It will be noted that the capping of slightlyleached iron formation is irregular in f
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Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectmineralindustries
