Economic Geology, Volume 19Economic Geology Publishing Company, 1924 - Geology |
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Common terms and phrases
abundant alteration amount angular appear associated Australia bands basin Beatson beds biotite bodies braunite calcite carbonate cent chalcocite chalcopyrite chemical chlorite coal contain copper country rock crystalline crystals deposits depth diabase dikes diorite district dolomite ECON ECONOMIC GEOLOGY evidence fault feet feldspar field fissures folding formation formed fractures fragments gabbro galena gangue Geol geologists grains granite granodiorite gypsum hausmannite heavy minerals hematite hornblende igneous rocks inches intrusive iron later limestone limonite lode magma magnetite manganese manganite masses metallic metamorphism microscope mines nickel eruptive nickel mineral norite occur origin oxidation pegmatites pentlandite petroleum polished surface polydymite present psilomelane pyrite pyrolusite pyroxene pyrrhotite quartz veins region replacement samples sand sandstone schist sedimentary sediments shale silicates solutions specimens sphalerite structure Sudbury sulphate sulphide sulphur temperature thick thin sections tion tube U. S. Geological Survey veinlets wall rock writer zone
Popular passages
Page 620 - ... having altered it in one or other of the manners above mentioned. The alteration products of the first class may be considered as due to the heated waters or vapours given off by the cooling magma, that is, to be of pneumatolytic origin; while the alteration products of the second class result from the more immediate action of the molten magma itself. The products of these two classes of alteration have much in common, however, and naturally pass one into the other. The evidence of the alterations...
Page ii - Economic Geology: with which Is Incorporated the American Geologist; a semiquarterly Journal devoted to geology as applied to mining and allied Industries and official medium of publication for Society of economic geologists.
Page 346 - Magnesite deposits which are being or have been worked can be divided into four types: (1) Magnesite as a sedimentary rock, (2) magnesite as an alteration of serpentine, (3) magnesite as a vein filling, and (4) magnesite as a replacement of limestone. Of these only the second and fourth are of economic importance at the present time. The most important and most complex is that which has been termed the replacement type. Deposits of the replacement type in at least two cases (Styria and Quebec) are...
Page 346 - Magnesite as a vein filling, 4. Magnesite as a replacement of limestone. Of these only the second and fourth are of economic importance at the present time. The most important and most complex is that which has been termed the replacement type. Deposits of the replacement type in at least two cases, (Styria and Quebec) are normal limestones replaced by magnesia-bearing solutions emanating from a granite magma. A similar origin seems to apply to the lesser known Washington occurrence.
Page 346 - The solutes at a certain stage precipitated out as serpentine and talc rather than us anhydrous minerals as is usually believed to be the case. Almost simultaneously any anhydrous minerals already formed became hydrated. Reaction between the limestones and dolomites and the silicate-bearing solutions formed magnesite or dolomite, depending upon whether the rock traversed by the solutions was a dolomite or a limestone. The wollastonite formed during the reaction was carried away in solution as in...
Page 177 - Orstrand of the United States Geological Survey. Some of his observations have been published (Discussion of the Records of some very deep wells in the Appalachian Oil Fields, etc., by IC White. State Geologist, West Virginia, and CE van Orstrand, 1918; IC White, West Virginia's Second Deepest Well of the World, Ohio Gas and Oil Man's Journal, September, 1919).
Page 139 - ... later. Regarding the Sudbury ores in particular these authors state that the ore bodies were not formed by the sinking of the ores in the molten magma. Summing up their conclusions in respect of the Sudbury ores Tolman and Rogers say: "Although the ores are believed to be magmatic they have been formed at the end of the magmatic period by the replacement of the silicates.
Page 382 - Zappfe, C., 1912, Effects of a basic igneous intrusion on a Lake Superior iron-bearing formation: Econ.
Page 382 - GROUT, FF, and BRODERICK, TM, The magnetite deposits of the eastern Mesabi range: Minnesota Geol.
Page 449 - ... as patches within, the pyroxene. The hornblende is in parallel position with the pyroxene, and is doubtless a magmatic alteration product. Small tremolite prisms replace the pyroxene and plagioclase. Another alteration product is calcite, which occurs in veinlets and occasionally in zonal crystals. The polished sections of the massive ores consist largely of pyrrhotite with residual spots of silicates. Associated with the pyrrhotite is a considerable amount of pentlandite. Calkins reported this...