The Genesis of Ore DepositsThe Institute, 1902 - 806 Seiten |
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acid alteration andesite ascending waters beds belt bornite calcite carbonates cassiterite cavities chalcopyrite channels chemical chlorides chlorite circulation Comstock Comstock Lode concentration containing copper country-rock crustification crusts crystalline crystals deposits depth descending diabase dikes diorite district Emmons enrichment eruptive rocks feet feldspar filled fissure-veins fissures flowage fluorite formation formed fracture galena Geology gold granite groundwater igneous rocks instance iron kaolin later level of groundwater lime limestone Lindgren lode magma mass material metallic metamorphism metasomatic meters mineral springs mining observed occur openings ore-bearing ore-bodies ore-deposits ore-veins original oxidized polybasite porphyry Posepny precipitation present pressure probably produced Prof Przibram pyrite pyrrhotite quartz Raibl reactions region replacement result rich salts sandstone schists secondary sedimentary sericite siderite silicates silver slate soluble solutions strata substances sulphate sulphides sulphur surface Surv temperature tion Trans U. S. Geol underground water upper vadose veins wall-rock water-level zinc zinc-blende zone
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Seite 353 - A conspicuous illustration of ore-deposits of this class which may be mentioned are the metallic copper deposits of the Lake Superior region. The copper was in all probability reduced and precipitated directly as metallic copper from upward moving cupriferous solutions. The reducing agents were the ferrous compounds in the solid form, in part as magnetite and as solutions derived from the iron-bearing silicates.
Seite 145 - Some of the attempted explanations assume, in my opinion correctly, as the cause of the first ore-depositions, the action of hot springs — in which connection it is only to be emphasized that these thermal effects occurred long after the intrusion of the eruptive flows between the sedimentary strata, so that the ores were brought, not by or in the eruptives themselves, but by the later springs, from great depths and perhaps from considerable distances. This explanation, applicab'e to all the deposits,...
Seite 717 - The ore-minerals are specularite, magnetite, bornite, chalcopyrite, pyrite, pyrrhotite, and, more rarely, galena and zinc-blende. The sulphides may carry some gold and silver, usually more of the latter than of the former, but are rarely rich. Tellurides are unknown. The characteristic feature is the association of the oxides of iron with sulphides, and the presence of various silicates of lime, magnesia, and iron. The deposits are throughout metasomatic, having been formed by the replacement of...
Seite 18 - ... towards the deepest point of the surface of the region, or towards a point where an impermeable rock outcrops. The ground-water is not stagnant, but moves, though with relative slowness, according to the difference in height and the size of the interstitial spaces, down the plane mentioned, and finds its way, in the first instance, directly into the nearest surface-stream, or, in the second instance, forms a spring, which takes indirectly a similar course.
Seite 145 - ... the eruptive flows between the sedimentary strata, so that the ores were brought, not by or in the eruptives themselves, but by the later springs, from great depths and perhaps from considerable distances. This explanation, applicable to all the deposits, suits also the exceptional case cited by R. I). Irving, namely, the Nonesuch copper-bed in the sandstone of Porcupine Mountain, far from an eruptive outflow.
Seite 200 - ... ground-water lying below water-level is not stagnant, but descends by capillarity, and, since it cannot be simply consumed in depth, receives there through a higher temperature a tendency to return towards the surface, which tendency is most easily satisfied through open channels. Stated summarily : The ground-water descends in the deep regions also through the capillaries of the rocks ; at a certain depth it probably moves laterally towards open conduits, and, reaching these, it ascends through...
Seite 189 - ... may have come up through a passage not yet exposed, and even that fault fissures and eruptive dikes exist which have not been discovered. From the fact that he refers in this connection only to Whitney's report of 1862, we conclude that he has not had access to the later and more exhaustive works of Strong and Chamberlin. Perhaps, with the full light conveyed by these reports and accompanying maps, Professor Posepny might have attached more importance to the objections raised.
Seite 6 - Gash-veins may cross the formation at any angle, but are limited to one particular group of strata, and are peculiar to the unaltered sedimentary rocks. True veins are aggregations of mineral matter, accompanied by metalliferous ores, within a crevice or fissure, which had its origin in some deep-seated cause, and which may be presumed to extend for an indefinite distance downwards.
Seite 731 - ... that is, it is thought highly probable that under sufficient pressure and at a high temperature there are all gradations between heated waters containing mineral material in solution and a magma containing water in solution.