The deposits of the useful minerals & rocks; their origin, form, and content . ng frequently arranged in basin shape. The deposits have then theform of large troughs, the axes of which are often much inclined constitutingthe so-called pitching troughs of which the sections by Van Hise andLeith given in Fig. 433 and 434 afford typical examples. From the com-prehensive monograph by Van Hise and colleagues upon Marquette, 1897, THE IRON ORE-BEDS IN CRYSTALLINE SCHISTS 1065 Fig. J:35, representing diagrammatically the following positions of richore, has likewise been taken: 1. In V-shaped troughs
The deposits of the useful minerals & rocks; their origin, form, and content . ng frequently arranged in basin shape. The deposits have then theform of large troughs, the axes of which are often much inclined constitutingthe so-called pitching troughs of which the sections by Van Hise andLeith given in Fig. 433 and 434 afford typical examples. From the com-prehensive monograph by Van Hise and colleagues upon Marquette, 1897, THE IRON ORE-BEDS IN CRYSTALLINE SCHISTS 1065 Fig. J:35, representing diagrammatically the following positions of richore, has likewise been taken: 1. In V-shaped troughs between the schist and a dyke of soapstone ;(2) along decomposed eruptive dykes in jasper ; (3) in jasper, immediatelybelow overlying quartzite ; (4) at the contact of jasper and the underlyingsoapstone, where the contours of the latter form a trough. Van Hise and Leith emphasize the fact that the siderite- and greenalite-schists, which frequently reach a thickness of 100-300 m., occur with sharplydefined contacts either upon quartzite, conglomerate, and altered clay-slate,. Fig. 431.—Thiu section of siderite troin tlie Peuokee district ; magnified 40 times. Van Hise. or upon basic eruptive sheets. In the ferruginous schists there are noclayey sediments. On this and other grounds it follows that these arenot mechanical, but chemical sediments. Deposition took place in fairlyshallow water, possibly in large lagoons, though owing to the abundanceof FeCOg and FeSiOg, that is, of iron originally chiefly in the ferrous andnot in the ferric condition, these ferruginous schists may not be com-pared with lake ore. The siderite- and greenalite-schists are invariably in the hanging-wallof particularly extensive and thick sheets of principally basic eruptives—basalts—which nuist be regarded as submarine outpourings. From thesesubmarine sheets the iron content of the schists has probably in greaterpart been derived. In addition to iron, a little manganese, and silica. 1066 OEE-DEPOSI
Size: 1581px × 1581px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
