The Origin of Igneous RocksA manuscript copy, with corrections and editor's notations in red, of the article published in the Philosophical Society of Washington Bulletin, volume 12, 1892. |
Common terms and phrases
Absaroka Absaroka range acid alkalies alumina analyses andesite augite basalt basic rocks biotite body of magma Bunsen Camptonite center of eruption character chemical composition chemical differentiation considered constituents Crandall basin crust crystalline crystallization dacite diagram dike rocks dikes Dolerite Durocher earth Electric peak eruptive rocks extreme extrusive feldspar feldspathic Felsite fissures flows fusion gabbro ganggesteine Geol geological granite granular groundmass groups of rocks hornblende igneous rocks intermediate iron oxide Kersantite kinds of rock lamprophyric lavas less silicious leucite Leucite-basalt Leucitophyre lime localities magnesia mass mica mineralogical Minette molecules molten magma Nephelinite occur olivine order of succession original magma Pantelleria peak and Sepulchre Phil porphyrites portion potash pressure quartz region reservoir rhyolite ROCKS OF TABLE Rosenbusch Scrope separation Sepulchre mountain series of rocks silica silicious end SiO2 soda solution specific gravity surface temperature theory tion trachyte variable variation various volcanic activity volcanic rocks Waltershausen Yellowstone Park
Popular passages
Page 145 - The general succession is from a rock of average composition through less silicious and more silicious ones to rocks extremely low in silica and others extremely high in silica, that is, the series commences with a mean and ends with the extremes.
Page 143 - The constant recurrence of particular series of rocks, often with a certain order of eruption in different localities, and the frequent occurrence of such series at neighboring centers of volcanic activity, would be enough to justify the belief that there was a definite connection between the members of a group.
Page 129 - Bohemia, and was afterwards clearly expressed by him in denning petrographical provinces as districts "within which the rocks erupted during any particular geological period present certain well-marked peculiarities in mineralogical composition and microscopical structure, serving at once to distinguish them from the rocks belonging to the same general group, which were simultaneously erupted in other petrographical provinces.
Page 112 - We know of no natural processes capable of separating the more acid parts of such a magma except the chemistry of the atmosphere acting at temperatures far below the meltingpoints of the silicates. We have the results of that process in the quartzites, granites, gneisses, and syenites among the silicious rocks: and the limestones and SESSIONAL PAPER No.
Page 90 - The object of (he present paper is to give the writer's reasons for concluding that all of the volcanic and other igneous rocks of any region are so intimately connected together by mineralogical and chemical relations that the}' must have originated from some single magma whose composition may be different in different regions; and, further, that it is the chemical differentiation of this primary magma which has given rise to the various kinds of igneous rocks.
Page 90 - that among the theories recently proposed upon the subjects specified above [namely. the nature, origin, and mode of eruption of igneous rocks], there is not one which has not already had its prototype in the phantasmagoria of the time of the dawn of geological science, and that it is these which have been constantly reproduced, enlarged, diversified, remodeled according to the advance of science, and supported by continuous accumulation of evidence.
Page 101 - ... the infusible ones solidified, and contracted in consequence of that solidification. This action might take place in spite of the greater specific gravity of the more fusible minerals, since the difference in the specific gravities would probably be small compared with the power of the eruptive force.
Page 96 - Under these conditions the ascending vapors voulcl urge the feldspar upward much less freely than the more liquid part of the lava, for the latter would yield more readily to the inflating vapors and thus become lighter and rise to the surface. This process, going on throughout the whole progress of...
Page 101 - From the very same stream of igneous matter, proceeding from the interior to the surface of the earth, the more readily fusible portions might be successively squeezed out, äs it were, äs the infusible ones solidified and contracted in consequence of that solidification. This action might take place in spite of the greater specific gravity of the more fusible minerals, since the difference of the specific gravity would probably be small compared with the power of the...
Page 194 - ... solution, the difference being one of solvent." Die Thatsache, dass bei der Verfestigung eines Silicatschmelzflusses keine plötzliche Änderung des elektrischen Widerstandes stattfindet, beweist ferner, dass auch ein festes in this direction. Until the establishment of definite knowledge concerning the nature of molten magmas we must proceed along the lines of analogy by applying to them such laws äs may be found applicable to Solutions that exist at lower temperatures and pressures.