Geology topics

W. W. Brannock

Publications and source records attributed to W. W. Brannock.

7 recordsLinked to original sources

USGS2014

Volcanic activity on Umnak and Great Sitkin Islands, 1946–1948

As part of the United States Geological Survey's volcano program in the Aleutian volcanic arc during 1946–1948, the volcanoes and thermal areas on Umnak and Great Sitkin Islands were studied. In addition to observation of the volcanoes, temperatures of fumaroles were measured and some products of the volcanic activity were collected and analyzed. After an eruption in 1945, Cone A in Okmok Caldera on northeastern Umnak Island remained relatively quiet during the period 1946–1948. The fumarole gases contained water vapor, carbon dioxide, and sulfur dioxide. The incrustations associated with the sulfur dioxide fumaroles are the sulfate minerals halotrichite, gypsum, and soda alum. Temperatures of lava fumaroles at the source of the December, 1945 lava flow from Cone A dropped from an average of 320°C on July 19, 1946, to 90°C on September 5, 1946. With exception of the large central fumarole which reached red heat in 1947, the extra crater fumaroles of Cone A ranged from 96° to 98° C in temperature Cone C, another cone in Okmok Caldera was in the solfataric stage and emitted water vapor, hydrogen sulfide, and probably carbon dioxide. Incrustations associated with fumaroles on this cone consisted of sulfur, pyrite, and aragonite. The temperatures of the fumaroles ranged from 95° to 96°C and were probably kept within this narrow range partly by the heat supplied during condensation of steam. Sixteen large thermal springs emerging from the base of Cone D in Okmok Caldera had an aggregate discharge of approximately 115 cfs and gave off approximately 21,000 kcal of heat per second on September 7, 1946. Water samples of thermal springs on Umnak Island contained as high as 159 ppm of boron expressed as B 2 0 3 and a few parts per million of arsenic and antimony. Several of the thermal springs in southwestern Umnak Island were slightly superheated with respect to the boiling point of water and behaved as small geysers. As has been found elsewhere, the discharge, temperature, and composition of the emanations from a spring is modified by surface conditions of topography and drainage. Thermal springs and fumaroles on Great Sitkin Island occurred at an altitude of about 2000 ft near the head of the west fork of Big Fox Creek. All the fumaroles were at or near a temperature of 100°C. The large crater fumarole in the center of the 1945 crater dome was unapproachable. No change in the activity of Great Sitkin volcano was observed between 1946 and August 1948.

Alaska↗

USGS2002

Rapid determination of water in silicate rocks

A rapid and simple method for the determination of total water in silicate rocks has been developed by modifying the Penfield procedure. In this method, the time required for a single determination has been reduced to less than 10 minutes. Comparison of the data obtained by this modification and the Penfield method indicates the same degree of accuracy.

Analytical Chemistry↗

USGS2002

Automatic photometric titrations of calcium and magnesium in carbonate rocks

Rapid nonsubjective methods have been developed for the determination of calcium and magnesium in carbonate rocks. From a single solution of the sample, calcium is titrated directly, and magnesium is titrated after a rapid removal of R2O3 and precipitation of calcium as the tungstate. A concentrated and a dilute solution of disodium ethylenediamine tetraacetate are used as titrants. The concentrated solution is added almost to the end point, then the weak solution is added in an automatic titrator to determine the end point precisely.

Analytical Chemistry↗

USGS1965

Isotopic ages of minerals from granitic rocks of the central Sierra Nevada and Inyo Mountains, California

Potassium-argon ages of biotite and hornblende from specimens of 17 granitic plutons in the central Sierra Nevada and the western Inyo Mountains, California, range from 69 to 183 m. y. The Mount Givens, Lamarck. and Round Valley Peak Granodiorites and related younger and more felsic quartz monzonites represent a pulse of magma emplaced in the general time interval of 80-90 million years ago, during Cretaceous time. Mineral ages of granitic rocks that flank these plutons on both the east and the west have been reduced during the emplacement of the Cretaceous intrusive rocks and are minimum ages for the time of crystallization. The ages of hornblende from the Tinemaha Granodiorite (150 to 180 m. y.) may approach crystallization dates. In conjunction with ages for other intrusive rocks in the Sierra Nevada and adjacent desert ranges they strongly suggest a magmatic episode during the Early Jurassic.

California↗

USGS1965

Eclogites and eclogites: Their differences and similarities

Eclogites are divisible into three groups based on mode of occurrence: Group A, inclusions in kimberlites, basalts, or layers in ultramafic rocks; Group B, bands or lenses within migmatite gneissic terrains; Group C, bands or lenses within alpine-type metamorphic rocks. The compositions range from olivine basalt for Group A to tholeiitic basalts for Group C. New analytical data on six eclogites from glaucophane schist terrains in California and New Caledonia now permit comparisons among the three eclogite types. The pyrope content of the garnets is distinctive for each group as follows: Group A, greater than 55 per cent py; Group B, 30–55 per cent py; Group C, less than 30 percent py. Pyroxenes coexisting with these garnets also reflect a compositional change related to their occurrence. The jadeite content progressively increases from Group A through Group B, whereas the diopside content decreases. A comparison of eclogites from different geologic occurrences but with similar bulk compositions demonstrates variation in Ca-Mg partition between coexisting garnet and pyroxene. The Ca/Mg ratio increases in garnet and decreases in pyroxene from Group A through Group B eclogites. This obvious difference in the Ca-Mg partition between coexisting garnet-pyroxene in eclogites of the same bulk composition indicates a broad range of pressure-temperature conditions obtained during crystallization. Experimental synthesis of eclogite-like material at high pressures and temperatures demonstrates that some eclogites may form in the earth's mantle, but naturally occurring Group C eclogites have coexisting garnet-pyroxene with distinct Ca/Mg ratios when compared to Group A or B eclogites of similar bulk composition. This difference in the Ca/Mg ratio must reflect the pressure-temperature conditions characterizing the glaucophane schist facies.

GSA Bulletin↗

USGS1956

Silica in hot-spring waters

The silica in hot-spring waters and in a few cold waters was studied by moans of the colorimetrie ammonium-molybdate method of analysis. Murata found in 1947 that only a part of the total silica in aged samples of high-silica waters was determinable by the colorimetric method. Weitz , franck And schuchard later showed that ammonium molybdate reacts readily with the monomeric form of silica (probably H 4 SiO 4 ) but very slowly with polymeric silica. If the colorimetric measurement is completed in two or three minutes, only the monomer is determined. Nearly all silica of hot springs is in the monomeric form. Solubility equilibrium exists between dissolved (monomeric) and amorphous silica. For the hot springs that were studied, the solubility is about 315 p.p.m. at 90°C and 110 p.p.m. at 25°C, which is very similar to Krauskopf's experimental data. Monomeric silica polymerizes so slowly to colloidal silica that many waters are supersaturated with respect to amorphous silica. The rate of polymerization is influenced by pH, temperature, degree of supersaturation, presence of previously formed colloidal and gelatinous silica and contact with opal and other substances. Supersaturated acid waters and alkaline waters with less than 100% supersaturation tend to remain supersaturated almost indefinitely, with little or no change. Precipitation of colloidal silica is favoured by high temperature and contact with opal. Many connate and other ground waters, including some thermal springs, are much below saturation with respect to amorphous silica, probably because low-solubility quartz and chalcedony have been precipitating. Quartz is favoured by relatively high temperature, slow rale of precipitation, and low degree of supersaturation, and is believed to form by deposition of monomeric molecules. Chalcedony is probably deposited when the degree of supersaturation is moderately high and the rate of deposition is relatively fast. The ranges of temperature over which quartz and chalcedony deposit no doubt overlap, but, if other factors are equal, quartz is favoured by high temperature. Opal is favoured by relatively low temperature and rapid rate of precipitation. Although opal has probably been deposited at temperatures as high as 140°C, it is unstable and is slowly converted to chalcedony or quartz. Water that is saturated with respect to opal is highly supersaturated with respect to quartz. Opal is probably formed from monomeric or more probably, the smaller polymeric molecules of silica, retaining some of their water content. Evidence is lacking for the direct conversion of gelatinous silica to opal. Some differences in solubility probably exist between amorphous opal and opal that shows X-ray patterns like that of cristobalite. The suggestion is made that clay minerals form by combination of monomeric silica and a comparable form of monomeric alumina, which must have very low solubility in waters within the pH range of 5 to 9. Because of the abundance and relatively high solubility of silica, the proposed reaction, dissolved alumina + dissolved silica ⇌ clay, is ordinarily displaced strongly to the right in hydrothermal alteration and in ordinary soil formation. With removal of free silica, aided by tropical rainfall and temperatures, the reaction may be displaced to the left by dissolution and removal of silica from the system. Alumina, because of its very low solubility, remains as bauxite.

Geochimica et Cosmochimica Acta↗

USGS1955

Rapid determination of carbon dioxide in silicate rocks

In the development of rapid methods for silicate rock analysis, a simpler and faster means was needed for the determination of carbon dioxide than the conventional "train" procedures. With the method presented here, which involves measurement of the volume of carbon dioxide evolved, the time required for a determination is about 5 minutes per sample. It provides a saving of 30 to 40 minutes for each determination without significant loss of accuracy.

Analytical Chemistry↗