A Treatise on Metamorphism |
Other editions - View all
Common terms and phrases
abundant acid actinolite alkalies alteration amount average batholiths belt of cementation belt of weathering calcite calcium carbonate carbon dioxide cent chemical composition chert chlorite circulation cleavage compounds constituents crystals decomposed decomposition deformation dehydration depth disintegration dissolved district dolomite explained extent favorable feldspar ferric flowage formations fractures geological gneisses grains granite granulation greater ground water grünerite heat hematite Hise hydration igneous rocks illustrated important injection instance intrusive iron iron-bearing katamorphism Lake level of ground limestone limonite magma magnesium magnetite mainly marble mass material mechanical metamorphism metasomatism meters mica mineral particles occur openings orogenic movements oxidation oxygen pegmatites plants porphyritic precipitation pressure probably produced proportion quantity quartz quartzite reactions recrystallization regions result salts sands sandstone saturated schistose schists sedimentary rocks sediments shales silicates slates soil soluble solution and deposition strain structures surface Survey take place temperature textures tion U. S. Geol underground zone of anamorphism
Popular passages
Page 723 - ... 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.
Page 724 - It, therefore, is probable that at considerable depths we have, on the one hand, material which all would ca.ll water solution, and on the other hand material which all would call liquid rock, with no sharp division-line between the two. If this be so, there are all stages of gradation between true igneous injection and aqueous cementation, and all the various phases of pegmatization may thus be fully explained...
Page 752 - ... elongation in the direction of least stress, and shortening or elongation in the direction of mean stress. Consequently the shape of the modified particle may be that which would be produced if a plastic grain were rolled out, the sides being confined in one direction, but with liberty to elongate in another direction...
Page 705 - IV., 241; 14 plates, of which 2 are colored; 2 figures in the text. Sold at the price of $1.50 in paper and $2.00 bound. Bulletin No. III. Scientific Series No. 2. A Contribution to the Geology of the Pre-Cambrian Igneous Rocks of the Fox River Valley, Wisconsin.
Page 778 - ... that this arrangement is caused, first, and most important, by parallel development of new minerals ; second, by the flattening and parallel rotation of old and new mineral particles; and third, and of least importance, by the rotation into approximately parallel positions of random original particles.
Page 418 - ... fall for days upon a pile of dry manure and not wet the mass deeper than a few inches. Water may likewise fall upon a dry dust pile and not spread through the mass, but be contained near the surface, unless it continues to fall, in which case the whole mass of the dusty material may become saturated. Water does not readily spread through a previously dry soil, because the tension or contracting power of the surface of the water is greater than the attraction of the soil grains, which tends to...
Page 751 - Indeed, to explain the phenomena in the case of crystalline schists which have been developed during a continuous process of deformation it does not seem necessary to suppose that complete recrystallization of all of the material is necessary. If the case of a large grain of quartz or feldspar in a recrystallizing rock be taken, we may suppose the process to go on somewhat as follows: Because of the lack of homogeneity of the rock the stresses are irregularly distributed. At the most exposed places...
Page 577 - C, impervious beds below and above A, acting as confining strata ; F, the height of the water level...
Page 751 - ... rather than more than the time required for most mountain-making movements, during this period, at the slow rate suggested, the rocks could be recrystallized 50,000 times by 1 per cent of water, and this number certainly seems adequate to fulfill the requirement that at any given moment the crystalline rock shall exhibit but a slight strain effect. Of course, it is not thought probable that any rock has completely recrystallized 50,000 times. Indeed, it is well known that many of the rocks in...
Page 753 - In proportion as the movement involves shearing motion or scission the mineral particles are rotated from a position in which the direction of greatest elongation is at right angles to the direction of greatest pressure, although at any given time the mineral particles tend to develop with their longer axes at right angles to the maximum pressure.