Professional Paper - United States Geological Survey, Issues 87-88The Survey, 1915 - Geology |
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abundant adjacent albite alkalic altered amount amphibole analyses andesite apatite aplite augite basalt batholiths beds belt biotite bodies calcite cent chalcopyrite chlorite Coast Range color composition conglomerate contact deposits contact rock contact zone Copper Mountain Copper Mountain area country rock crosscuts crystals developed Devonian diabase diopside diorite elevation epidote exposed feet wide feldspar gabbro gangue garnet grains granitic intrusives granodiorite graywacke Green Monster groundmass Hawaiian Hetta Inlet hornblende igneous rocks intrusive mass intrusive rock Jumbo Basin Jumbo claim Kasaan Bay Kasaan Peninsula Ketchikan Ketchikan district Kilauea labradorite Lake lavas limestone magma magnetite Mauna Mesozoic metamorphism miles minerals mining nephelite normative occur olivine orthoclase pegmatite petrographic phenocrysts plagioclase porphyry Prince of Wales pyrite pyroxene pyrrhotite quartz quartzite rock containing schists sedimentary rocks siliceous slate slope smelter southeastern Alaska Specimen strata sulphide surface Survey syenite texture titanite tuff tunnel U. S. Geol volcanic Wales Island
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Page 32 - ... kind, very slightly vesicular or hardly at all so, very sparingly chrysolitic, and frequently having on the worn exterior a faint banded appearance from alternating variations in compactness of texture. Another kind varies in color from faintly reddish to gray, is more or less vesicular, and contains a large amount of chrysolite.
Page 21 - In other words, the inland rocks were then above the zone of deep seated metamorphism (rock flowage) and were, therefore, profoundly affected by the invading intrusives and accompanying pneumatolytic solutions. Furthermore, the mineralbearing solutions emanating from the granite encountered new conditions of temperature and pressure on...
Page 43 - ... numerous igneous dykes, and it seems probable that the deposit is the result of contact metamorphism of the limestone by the dyke rocks, resembling closely in this respect the epidote occurrence with copper ore in the Seven Devils Mts. in Idaho.* The specimens at hand consist of several loose crystals and a magnificent cluster of large crystals implanted on massive epidote. The only associated mineral is quartz in small clear crystals of later formation than the epidote. The epidote is very dark...
Page 11 - The bluff is traversed by small veins full of nephelite, granular melilite, and augite. Either of these minerals may form a layer of crystals, closely crowded together, all standing vertically to the plane of occurrence. Veins 3 inches wide or less abound in these minerals, mixed with a multitude of acicular crystals of kaliophilite.
Page 19 - ... arranged parallel to the brachypinacoid and hence showing no other kind of twinning. The form of one of these groups is shown in fig. 12. The cleavage marks the position of the basal plane and the angle of the section (about 80°) shows that it is bounded by the planes c (001) and y (201). The extinction makes an angle of a few degrees with the basal edge, varying + or — with a slight change in the direction of the section. This optical character and the further fact that the acute bisectrix...
Page 81 - ... of the table on page 87, it seems that during the more active period of each volcano differentiation was seldom if ever able to produce partial magmas of extremely salic or femic character. This might be due to short periods of quiet in the magma chamber or reservoir, insufficient to produce great differentiation. Even between eruptive periods there might be internal movements of the magma, accompanying changes of temperature, sufficient to again mingle parts of somewhat different composition.
Page 95 - From vents like Mont Pelee, which in periods of explosive outbreaks yield no molten lava, the vapors rise in such volume that cubic miles become our standards of measurement. There is no reason to believe that many of the igneous rocks which do not reach the surface are any less rich, and when they rise so near to the upper world that their emissions may attain the surface we must assign to the resulting waters a very important part in the underground economy. This general question has attracted...
Page 20 - On the coastal side the metamorphism near the contact is usually of the deep-seated type; gneisses and schists predominate and are cut by innumerable pegmatite dikes ramifying from the granite. Mineralization by sulphides is not pronounced near the contact.
Page 32 - ... character of Kilauean lavas of older date than any flows now visible. JD Dana,4 who examined the tuff-breccia with care in 1887, has briefly described the megascopic appearance of the rock fragments as follows: The ejected stones vary in size up to several cubic feet. Those of 1 or 2 cubic feet are common, many are 20 to 30, and one seen by the author on the west side of Kilauea measured 100 cubic feet and must have weighed over 8 tons.