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Sample records for horonobe siliceous rocks

  1. Relationship Between Faults Oriented Parallel and Oblique to Bedding in Neogene Massive Siliceous Mudstones at The Horonobe Underground Research Laboratory, Japan

    NASA Astrophysics Data System (ADS)

    Hayano, Akira; Ishii, Eiichi

    2016-10-01

    This study investigates the mechanical relationship between bedding-parallel and bedding-oblique faults in a Neogene massive siliceous mudstone at the site of the Horonobe Underground Research Laboratory (URL) in Hokkaido, Japan, on the basis of observations of drill-core recovered from pilot boreholes and fracture mapping on shaft and gallery walls. Four bedding-parallel faults with visible fault gouge, named respectively the MM Fault, the Last MM Fault, the S1 Fault, and the S2 Fault (stratigraphically, from the highest to the lowest), were observed in two pilot boreholes (PB-V01 and SAB-1). The distribution of the bedding-parallel faults at 350 m depth in the Horonobe URL indicates that these faults are spread over at least several tens of meters in parallel along a bedding plane. The observation that the bedding-oblique fault displaces the Last MM fault is consistent with the previous interpretation that the bedding- oblique faults formed after the bedding-parallel faults. In addition, the bedding-parallel faults terminate near the MM and S1 faults, indicating that the bedding-parallel faults with visible fault gouge act to terminate the propagation of younger bedding-oblique faults. In particular, the MM and S1 faults, which have a relatively thick fault gouge, appear to have had a stronger control on the propagation of bedding-oblique faults than did the Last MM fault, which has a relatively thin fault gouge.

  2. Evolution of permeability and microstructure of experimentally-created shear zones in Neogene siliceous mudstones from Horonobe, Japan

    NASA Astrophysics Data System (ADS)

    Uehara, Shin-ichi; Takahashi, Miki

    2014-03-01

    We report experimental measurements of bulk permeability changes due to a shear zone that is induced in siliceous mudstones collected from the Koetoi and Wakkanai Formations, northern Hokkaido, which are known to show different relationships between fault/fracture distribution and groundwater flow. We evaluate distributions of volumetric deformation in the induced shear zones by using micro-focus X-ray computed tomography. Measured permeability evolution while achieving the peak axial stress for specimens differed for the samples of the two formations. Permeability did not change obviously during shear for the Koetoi Fm. specimens, but in the Wakkanai Fm. specimens, the bulk permeability increased by a factor of 2.5 after reaching the peak stress. The difference in permeability change in these experiments can explain the differences in relationships between in situ groundwater flow and fracture distribution for the two formations. Analyses of the X-ray images reveal that this difference should reflect the differences of the volumetric deformation in the induced shear zones. Pore collapse occurred in the shear zone in the Koetoi Fm. specimen, which leads to porosity reduction, whereas fracture damages developed in the Wakkanai Fm. specimen, increasing porosity. These differences in the microstructure may reflect differences in yielding criteria for these host rocks.

  3. Peralkaline silicic volcanic rocks in northwestern nevada.

    PubMed

    Noble, D C; Chipman, D W; Giles, D L

    1968-06-21

    Late Tertiary silicic ashflow tuffs and lavas peralkaline in chemical character (atomic Na + K greater than Al), mainly comendites, occur over wide areas in northwestern Nevada and appear to be widespread in southeastern Oregon. Such peralkaline rocks-which are not uncommon in the western United States-and other chemically unusual silicic rocks are found near the margins rather than toward the center of the Great Basin.

  4. Determination of chlorine in silicate rocks

    USGS Publications Warehouse

    Peck, L.C.

    1959-01-01

    In a rapid accurate method for the determination of chlorine in silicate rocks, the rock powder is sintered with a sodium carbonate flux containing zinc oxide and magnesium carbonate. The sinter cake is leached with water, the resulting solution is filtered, and the filtrate is acidified with nitric acid. Chlorine is determined by titrating this solution with mercuric nitrate solution using sodium nitroprusside as the indicator. The titration is made in the dark with a beam of light shining through the solution. The end point of the titration is found by visually comparing the intensity of this beam of light with that of a similar beam of light in a reference solution.

  5. Lithologic mapping of silicate rocks using TIMS

    NASA Technical Reports Server (NTRS)

    Gillespie, A. R.

    1986-01-01

    Common rock-forming minerals have thermal infrared spectral features that are measured in the laboratory to infer composition. An airborne Daedalus scanner (TIMS) that collects six channels of thermal infrared radiance data (8 to 12 microns), may be used to measure these same features for rock identification. Previously, false-color composite pictures made from channels 1, 3, and 5 and emittance spectra for small areas on these images were used to make lithologic maps. Central wavelength, standard deviation, and amplitude of normal curves regressed on the emittance spectra are related to compositional information for crystalline igneous silicate rocks. As expected, the central wavelength varies systematically with silica content and with modal quartz content. Standard deviation is less sensitive to compositional changes, but large values may result from mixed admixture of vegetation. Compression of the six TIMS channels to three image channels made from the regressed parameters may be effective in improving geologic mapping from TIMS data, and these synthetic images may form a basis for the remote assessment of rock composition.

  6. U.S. Geological Survey silicate rock standards

    USGS Publications Warehouse

    Flanagan, F.J.

    1967-01-01

    The U.S. Geological Survey has processed six silicate rocks to provide new reference samples to supplement G-1 and W-1. Complete conventional, rapid rock, and spectrochemical analyses by the U.S. Geological Survey are reported for a granite (replacement for G-1), a granodiorite, an andesite, a peridotite, a dunite, and a basalt. Analyses of variance for nickel, chromium, copper, and zirconium in each rock sample showed that for these elements, the rocks can be considered homogeneous. Spectrochemical estimates are given for the nickel, chromium, copper, and zirconium contents of the samples. The petrography of five of the six rocks is described and CIPW norms are presented. ?? 1967.

  7. Loss of halogens from crystallized and glassy silicic volcanic rocks

    USGS Publications Warehouse

    Noble, D.C.; Smith, V.C.; Peck, L.C.

    1967-01-01

    One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

  8. Silicate versus trace mineral susceptibility in metamorphic rocks

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham; MacKenzie, Allan; Jensen, Eleanor

    1990-06-01

    Rates of change of magnetic susceptibility during leaching can characterize the presence of certain common types of magnetic minerals in metamorphic rocks. In this study the results of leaching are confirmed by mineral separation, optical microscopy, scanning electron microscopy (SEM) and microchemical analysis under SEM. Leaching curves provide a simple, rapid way of determining the relative roles of oxides, sulfides, and silicates in carrying the susceptibility in metamorphic rocks.

  9. Rapid determination of nanogram amounts of tellurium in silicate rocks

    USGS Publications Warehouse

    Greenland, L.P.; Campbell, E.Y.

    1976-01-01

    A hydride-generation flameless atomic-absorption technique is used to determine as little as 5 ng g-1 tellurium in 0.25 g of silicate rock. After acid decomposition of the sample, tellurium hydride is generated with sodium borohydride and the vapor passed directly to a resistance-heated quartz cell mounted in an atomic-absorption spectrophotometer. Analyses of 11 U.S. Geological Survey standard rocks are presented. ?? 1976.

  10. Spectrophotometric determination of fluorine in silicate rocks

    USGS Publications Warehouse

    Peck, L.C.; Smith, V.C.

    1964-01-01

    The rock powder is sintered with a sodium carbonate flux containing zinc oxide and magnesium carbonate, the sinter-cake leached with water and the resulting solution filtered. Fluorine is separated from the acidified filtrate by steam distillation and determined spectrophotometrically by means of a zirconium-SPADNS reagent. If a multiple-unit distillation apparatus is used, 12 determinations can be completed per man-day. ?? 1964.

  11. Lunar highland melt rocks - Chemistry, petrology and silicate mineralogy

    NASA Technical Reports Server (NTRS)

    Vaniman, D. T.; Papike, J. J.

    1980-01-01

    A selected suite containing several of the largest samples of lunar highland melt rocks includes impact melt specimens (anorthositic gabbro, low-K Fra Mauro) and volcanic specimens (intermediate-K Fra Mauro). Although previous assumptions of LKFM volcanism have fallen into disfavor, no fatal arguments against this hypothesis have been presented, and the evidence of a possibly 'inherited igneous' olivine-plagioclase cosaturation provides cause for keeping a volcanic LKFM hypothesis viable. Comparisons of silicate mineralogy with melt rock compositions provide information on the specimen's composition and cooling history. Plagioclase-rock compositions can be matched to the experimentally determined equilibria for appropriate samples to identify melt rocks with refractory anorthitic clasts. Olivine-rock compositions indicate that melt rock vitrophyres precipitate anomalously Fe-rich olivine; the cause of this anomaly is not immediately evident. The Al-Ti and Ca-Fe-Mg zonation in pyroxene provide information on relative cooling rates of highland melt rocks, but Cr- and Al-content (where Al-rich low-Ca pyroxene cores are preserved in rapidly cooled samples) can be correlated with composition of the host rock.

  12. Age and speciation of iodine in groundwater and mudstones of the Horonobe area, Hokkaido, Japan: Implications for the origin and migration of iodine during basin evolution

    NASA Astrophysics Data System (ADS)

    Togo, Yoko S.; Takahashi, Yoshio; Amano, Yuki; Matsuzaki, Hiroyuki; Suzuki, Yohey; Terada, Yasuko; Muramatsu, Yasuyuki; Ito, Kazumasa; Iwatsuki, Teruki

    2016-10-01

    This paper reports the concentration, speciation and isotope ratio (129I/127I) of iodine from both groundwater and host rocks in the Horonobe area, northern Hokkaido, Japan, to clarify the origin and migration of iodine in sedimentary rocks. Cretaceous to Quaternary sedimentary rocks deposited nearly horizontally in Tenpoku Basin and in the Horonobe area were uplifted above sea level during active tectonics to form folds and faults in the Quaternary. Samples were collected from the Pliocene Koetoi and late Miocene Wakkanai formations (Fms), which include diatomaceous and siliceous mudstones. The iodine concentration in groundwater, up to 270 μmol/L, is significantly higher than that of seawater, with the iodine enrichment factor relative to seawater reaching 800-1500. The iodine concentration in the rocks decreases from the Koetoi to Wakkanai Fms, suggesting that iodine was released into the water from the rocks of deeper formations. The iodine concentration in the rocks is sufficiently high for forming iodine-rich groundwater as found in this area. X-ray absorption near edge structure (XANES) analysis shows that iodine exists as organic iodine and iodide (I-) in host rocks, whereas it exists mainly as I- in groundwater. The isotope ratio is nearly constant for iodine in the groundwater, at [0.11-0.23] × 10-12, and it is higher for iodine in rocks, at [0.29-1.1] × 10-12, giving iodine ages of 42-60 Ma and 7-38 Ma, respectively. Some iodine in groundwater must have originated from Paleogene and even late Cretaceous Fms, which are also considered as possible sources of oil and gas, in view of the old iodine ages of the groundwater. The iodine ages of the rocks are older than the depositional ages, implying that the rocks adsorbed some iodine from groundwater, which was sourced from greater depths. The iodine concentration in groundwater decreases with decreasing chlorine concentration due to mixing of iodine-rich connate water and meteoric water. A likely scenario

  13. Precise determination of ferrous iron in silicate rocks

    NASA Astrophysics Data System (ADS)

    Yokoyama, Tetsuya; Nakamura, Eizo

    2002-03-01

    We have developed a highly precise method for the determination of ferrous iron (Fe 2+) in silicate rocks. Our new method is based on Wilson's procedure (1955) in which surplus V 5+ is used to oxidize Fe 2+ into Fe 3+ while equivalently reducing V 5+ into V 4+. Because V 4+ is more resistant to atmospheric oxidation than Fe 2+, Fe 2+ in the sample can be determined by measuring unreacted V 5+ by adding excess Fe 2+ after sample decomposition and then titrating the unreacted Fe 2+ with Cr 6+. With our method, which involves conditioning the sample solution with 5 M H 2SO 4 in a relatively small beaker (7 mL), the oxidation of Fe 2+ or V 4+ that leads to erroneous results can be completely avoided, even in 100-h sample decompositions at 100°C. We have measured the concentration of FeO in 15 standard silicate rock powders provided by the Geological Survey of Japan (GSJ). Analytical reproducibility was better than 0.5% (1σ) for all but those samples that had small amounts of Fe 2+ (<1.5 wt.% of FeO). Fourteen of these samples gave FeO contents significantly higher than the GSJ reference values. This likely indicates that the GSJ reference values, obtained by compiling previously published data, contain a large number of poor-quality data obtained by methods with lower recovery of Fe 2+ caused by oxidation or insufficient sample decomposition during analyses. To achieve accurate determinations of Fe 2+ in our method, several factors besides the oxidation must be considered, including: (1) long-term variations in the concentration of Fe 2+ solution must be corrected; (2) excess use of the indicator must be avoided; and (3) the formation of inert FeF + complex must be avoided during titration when using boric acid as a masking agent.

  14. Impedance spectra of hot, dry silicate minerals and rocks: qualitative interpretation of spectra

    USGS Publications Warehouse

    Huebner, J.S.; Dillenburg, R.G.

    1995-01-01

    Impedance spectroscopy helps distinguish the contributions that grain interiors and grain boundaries make to electrical resistance of silicate minerals and rocks. Olivine, orthopyroxene, clinopyroxenes, and both natural and synthetic clinopyroxenite were measured. A network of electrical elements is presented for use in interpreting impedance spectra and conductive paths in hot or cold, wet or dry, minerals and rocks at any pressure. In dry rocks, a series network path predominates; in wet rocks, aqueous pore fluid and crystals both conduct. Finite resistance across the sample-electrode interface is evidence that electronic charge carriers are present at the surface, and presumably within, the silicate minerals and rocks measured. -from Authors

  15. Testing the Role of Silicic Acid and Bioorganic Materials in the Formation of Rock Coatings

    SciTech Connect

    Kolb, Vera; Philip, Ajish I.; Perry, Randall S.

    2004-12-01

    Silica, amino acids, and DNA were recently discovered in desert varnish. In this work we experimentally test the proposed role of silicic acid and bio-chemicals in the formation of desert varnish and other rock coatings. We have developed a protocol in which hte rocks were treated with a mixture of silicic acid, sugars, amino acids, metals and clays, under the influence of heat and UV light. This protocol reflects the proposed mechanism of hte polymerization of silicic acid with the bioorganic materials, and the laboratory model for the natural conditions under which the desert varnish is formed. Our experiments produced coatings with a hardness and morphology that resemble the nature ones. These results provide a support for the role of silicic acid in the formation of rock coatings. Since the hard silica-based coatings preserve organic compounds in them, they may serve as a biosignature for life, here or possibly Mars.

  16. Evolution of peralkaline silicic complexes: Lessons from the extrusive rocks

    NASA Astrophysics Data System (ADS)

    Macdonald, Ray

    2012-11-01

    Young (< 1 Ma) volcanic complexes in the Kenya Rift Valley are used to outline recent progress in our understanding of how peralkaline silicic systems evolve. Such systems are all to some degree unique, varying in their structural development, the interplay of petrogenetic complexes, and the range of lithologies. Peralkaline silicic reservoirs vary greatly in size and form (even beneath volcanoes of roughly similar size) but all are basalt-driven, in that basaltic magma is the fundamental source of heat and volatiles in the magmatic system. Fractional crystallisation of basaltic magma is the dominant differentiation mechanism but important contributions are made by magma mixing, remobilisation of crystal mushes and feldspar resorption, exsolution of carbonate phases and various volatile-magma interactions. Peralkaline silicic magmas are water-rich (> 4 wt.%) and the rhyolitic varieties evolve to temperatures < 800 °C at oxygen fugacities largely within the range ∆FMQ 0 to - 1. They can be categorised as of cold-wet-reduced type. Low viscosities (< 104-106 Pa s) result in rapid growth of volcanic edifices, highly efficient crystal-melt separation and the ubiquitous development of compositionally zoned caps to reservoirs. No peralkaline equivalent of the monotonous intermediate ignimbrites found in some calc-alkaline systems has yet been found.

  17. Darkening of silicate rock powders by solar wind sputtering.

    NASA Technical Reports Server (NTRS)

    Hapke, B.

    1973-01-01

    Hydrogen ion irradiation of powdered igneous rocks, including Apollo rocks, has been observed in the laboratory to darken the powders and to make their optical properties similar to the moon's. An extensive series of investigations shows that this darkening is not spurious. These results are consistent with those of other investigators, including Nash (1967). Darkening of lunar igneous rock powders by the formation of solar wind-sputtered glass films is a real process which occurs on the moon. The time scale for darkening of undisturbed lunar soil is of the order of 50,000-100,000 yr. Comparison of the rates of the formation of glasses on the lunar surface by solar wind sputter-deposition, meteorite impact melting, and impact vaporization-deposition indicates that these processes are of comparable importance under the present flux of meteorites.

  18. Petrographic and crystallographic study of silicate minerals in lunar rocks

    NASA Technical Reports Server (NTRS)

    Carmichael, I. S. E.; Turner, F. J.; Wenk, H. R.

    1974-01-01

    Optical U-stage measurements, chemical microprobe data, and X-ray procession photographs of a bytownite twin group from rock 12032,44 are compared. Sharp but weak b and no c-reflections were observed for this An89 bytownite indicating a partly disordered structure. Euler angles, used to characterize the orientation of the optical indicatrix, compare better with values for plutonic than for volcanic plagioclase. This indicates that structural and optical properties cannot be directly correlated.

  19. Characterizing silicic rocks in the Parana Magmatic Province: an update in their origin and emplacement

    NASA Astrophysics Data System (ADS)

    Luchetti, A. F.; Nardy, A. R.; Machado, F. B.; Gravley, D. M.; Gualda, G. A.

    2013-12-01

    The Paraná Magmatic Province (PMP), a large igneous province in southern Brazil (with correlative rocks in western Africa), includes 800,000 km3 of flood basalts generated during the rifting that ultimately led to the opening of the South Atlantic and covers nearly 75% of the surface of the Paraná Basin. Towards the top of the volcanic pile, silicic rocks are observed in many areas. They comprise a small proportion of the total erupted volume (2.5%), yet correspond to a significant flare-up of silicic volcanism over a period of only a few million years. In Brazil, the silicic rocks are divided into two groups, the Chapecó Member, which appears more northerly and includes porphyritic, crystal-rich, high-Ti dacites and trachydacites; and the Palmas Member, which includes fine-grained, crystal-poor, low-Ti dacites and rhyolites. The mode of emplacement (lavas vs. pyroclastic flows) of the volcanic units has been the subject of much controversy. The aim of this project is to better understand the origin and evolution of the PMP silicic rocks. We are combining information from the regional to the thin section scale to better characterize eruption dynamics and magma distribution prior to eruption. In both Palmas and Chapecó units, we observe features consistent with emplacement in the form of pyroclastic density currents, e.g. fiamme, variable weathering patterns consistent with local variations in welding at the outcrop scale, vertical gas-escape structures, sedimentary dykes, and lythophysae. Some ignimbrite units can be traced for 10's of kilometers and with more research on their spatial distribution could reveal the location of eruptive centers. In the Palmas, ignimbrites can be observed juxtaposed against or overlying discrete eruptive centers in the form of discordant structures that resemble domes and coulees typical of lava extrusion and flow. However, many of the silicic rocks are ambiguous and difficult to characterize, with features that could be related

  20. Simulated Lunar Environment Spectra of Silicic Volcanic Rocks: Application to Lunar Domes

    NASA Astrophysics Data System (ADS)

    Glotch, T. D.; Shirley, K.; Greenhagen, B. T.

    2016-12-01

    Lunar volcanism was dominated by flood-style basaltic volcanism associated with the lunar mare. However, since the Apollo era it has been suggested that some regions, termed "red spots," are the result of non-basaltic volcanic activity. These early suggestions of non-mare volcanism were based on interpretations of rugged geomorphology resulting from viscous lava flows and relatively featureless, red-sloped VNIR spectra. Mid-infrared data from the Diviner Lunar Radiometer Experiment on the Lunar Reconnaissance Orbiter have confirmed that many of the red spot features, including Hansteen Alpha, the Gruithuisen Domes, the Mairan Domes, Lassell Massif, and Compton Belkovich are silicic volcanic domes. Additional detections of silicic material in the Aristarchus central peak and ejecta suggest excavation of a subsurface silicic pluton. Other red spots, including the Helmet and Copernicus have relatively low Diviner Christiansen feature positions, but they are not as felsic as the features listed above. To date, the SiO2 content of the silicic dome features has been difficult to quantitatively determine due to the limited spectral resolution of Diviner and lack of terrestrial analog spectra acquired in an appropriate environment. Based on spectra of pure mineral and glass separates, preliminary estimates suggest that the rocks comprising the lunar silicic domes are > 65 wt.% SiO2. In an effort to better constrain this value, we have acquired spectra of andesite, dacite, rhyolite, pumice, and obsidian rock samples under a simulated lunar environment in the Planetary and Asteroid Regolith Spectroscopy Environmental Chamber (PARSEC) at the Center for Planetary Exploration at Stony Brook University. This presentation will discuss the spectra of these materials and how they relate to the Diviner measurements of the lunar silicic dome features.

  1. Carbonate and silicate rock standards for cosmogenic 36Cl

    NASA Astrophysics Data System (ADS)

    Mechernich, Silke; Dunai, Tibor J.; Binnie, Steven A.; Goral, Tomasz; Heinze, Stefan; Dewald, Alfred; Benedetti, Lucilla; Schimmelpfennig, Irene; Phillips, Fred; Marrero, Shasta; Akif Sarıkaya, Mehmet; Gregory, Laura C.; Phillips, Richard J.; Wilcken, Klaus; Simon, Krista; Fink, David

    2017-04-01

    The number of studies using cosmogenic nuclides has increased multi-fold during the last two decades and several new dedicated target preparation laboratories and Accelerator Mass Spectrometry (AMS) facilities have been established. Each facility uses sample preparation and AMS measurement techniques particular to their needs. It is thus desirable to have community-accepted and well characterized rock standards available for routine processing using identical target preparation procedures and AMS measurement methods as carried out for samples of unknown cosmogenic nuclide concentrations. The usefulness of such natural standards is that they allow more rigorous quality control, for example, the long-term reproducibility of results and hence measurement precision, or the testing of new target preparation techniques or newly established laboratories. This is particularly pertinent for in-situ 36Cl studies due to the multiplicity of 36Cl production pathways that requires a variety of elemental and isotopic determinations in addition to AMS 36Cl assay. We have prepared two natural rock samples (denoted CoCal-N and CoFsp-N) to serve as standard material for in situ-produced cosmogenic 36Cl analysis. The sample CoCal-N is a pure limestone prepared from pebbles in a Namibian lag deposit, while the alkali-feldspar CoFsp-N is derived from a single crystal in a Namibian pegmatite. The sample preparation took place at the University of Cologne, where first any impurities were removed manually from both standards. CoCal-N was leached in 10 % HNO3 to remove the outer rim, and afterwards crushed and sieved to 250-500 μm size fractions. CoFsp-N was crushed, sieved to 250-500 μm size fractions and then leached in 1% HNO3 / 1% HF until 20% of the sample were removed. Both standards were thoroughly mixed using a rotating sample splitter before being distributed to other laboratories. To date, a total of 28 CoCal-N aliquots (between 2 and 16 aliquots per facility) and 31 Co

  2. Oxygen isotopes of some trondhjemites, siliceous gneisses, and associated mafic rocks

    USGS Publications Warehouse

    Barker, F.; Friedman, I.; Hunter, D.R.; Gleason, J.D.

    1976-01-01

    Analyses of oxygen isotopes in whole-rock samples of 58 Precambrian and Phanerozoic trondhjemites and siliceous gneisses and of 28 cogenetic mafic to intermediate rocks from North America, Fennoscandia, and southern Africa give the following results: 1. (1) 47 trondhjemites, tonalites, and mostly Archean acidic gneisses that apparently are not isotopically disturbed show an overage ?? 15O of +7.3??? and a range of 5.2-8.9???; 11 other samples are slightly to moderately disturbed and show higher values; and 2. (2) the mafic rocks show a wide range of ??-values, from about 0-9??? but the undisturbed ones give an average ?? 18O of 5.2???. The ?? 18O values of the trondhjemitic intrusives and siliceous gneisses of similar composition are lower than those of most granitic rocks and support models for derivation of these rocks from basaltic parents. This approach, however, cannot be used to determine if individual bodies formed by differentiation or by partial melting. ?? 1976.

  3. Late Cretaceous intraplate silicic volcanic rocks from the Lake Chad region: An extension of the Cameroon volcanic line?

    NASA Astrophysics Data System (ADS)

    Shellnutt, J. G.; Lee, T.-Y.; Torng, P.-K.; Yang, C.-C.; Lee, Y.-H.

    2016-07-01

    Silicic volcanic rocks at Hadjer el Khamis, near Lake Chad, are considered to be an extension of the Cameroon volcanic line (CVL) but their petrogenetic association is uncertain. The silicic rocks are divided into peraluminous and peralkaline groups with both rock types chemically similar to within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206Pb/238U age of 74.4 ± 1.3 Ma indicating the magmas erupted ˜10 million years before the next oldest CVL rocks (i.e., ˜66 Ma). The Sr isotopes (i.e., ISr = 0.7021-0.7037) show a relatively wide range but the Nd isotopes (i.e., 143Nd/144Ndi = 0.51268-0.51271) are uniform and indicate that the rocks were derived from a moderately depleted mantle source. Thermodynamic modeling shows that the silicic rocks likely formed by fractional crystallization of a mafic parental magma but that the peraluminous rocks were affected by low temperature alteration processes. The silicic rocks are more isotopically similar to Late Cretaceous basalts identified within the Late Cretaceous basins (i.e., 143Nd/144Ndi = 0.51245-0.51285) of Chad than the uncontaminated CVL rocks (i.e., 143Nd/144Ndi = 0.51270-0.51300). The age and isotopic compositions suggest the silicic volcanic rocks of the Lake Chad region are related to Late Cretaceous extensional volcanism in the Termit basin. It is unlikely that the silicic volcanic rocks are petrogenetically related to the CVL but it is possible that magmatism was structurally controlled by suture zones that formed during the opening of the Central Atlantic Ocean and/or the Pan-African Orogeny.

  4. Geochemistry of silicate-rich rocks can curtail spreading of carbon dioxide in subsurface aquifers.

    PubMed

    Cardoso, S S S; Andres, J T H

    2014-12-11

    Pools of carbon dioxide are found in natural geological accumulations and in engineered storage in saline aquifers. It has been thought that once this CO2 dissolves in the formation water, making it denser, convection streams will transport it efficiently to depth, but this may not be so. Here, we assess theoretically and experimentally the impact of natural chemical reactions between the dissolved CO2 and the rock formation on the convection streams in the subsurface. We show that, while in carbonate rocks the streaming of dissolved carbon dioxide persists, the chemical interactions in silicate-rich rocks may curb this transport drastically and even inhibit it altogether. These results challenge our view of carbon sequestration and dissolution rates in the subsurface, suggesting that pooled carbon dioxide may remain in the shallower regions of the formation for hundreds to thousands of years. The deeper regions of the reservoir can remain virtually carbon free.

  5. Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry

    USGS Publications Warehouse

    Elsheimer, H.N.; Fries, T.L.

    1990-01-01

    A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of tricotylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 ??g l-1 of tin in the MIBK solution or 0.2-0.3 ??g g-61 in the rock. The concentration range is linear between 2.5 and 500 ??g l-1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 ??g l-1 level and < 7% at the 10-30 ??g l-1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 ??g g-1 or less.

  6. Spectrofluorimetric determination of thallium in silicate rocks with rhodamine b in the presence of aluminum chloride

    USGS Publications Warehouse

    Shnepfe, M.M.

    1975-01-01

    A sensitive spectrofluorimetric procedure with rhodamine B in the presence of aluminum chloride is given for determining submicrogram and microgram quantities of thallium in silicate rocks. Samples are decomposed with a mixture of hydrofluoric and nitric acids and then treated with hydrochloric acid. Thallium is extracted as its dithizonate with chloroform from an alkaline medium containing ascorbate, citrate, and cyanide and then back-extracted with dilute nitric acid. After destruction of the organic matter and treatment with bromine, hydrochloric acid, aluminum chloride, and rhodamine B, the {A table is presented}. ?? 1975.

  7. Study on the order degree and geochemical characteristics of major elements of siliceous rock in eastern Qinling area, China.

    PubMed

    Ming, Lü; Li, Hong-Zhong; Zhao, Ming-zhen; Ma, Ming-wu; Yang, Zhi-Jun; Liang, Jin

    2014-11-01

    Siliceous rocks were extensively distributed in the marine volcanic sedimentary formation of Erlangping Group in the Early Paleozoic in eastern Qinling area. These siliceous rocks formed in the same age, but had differences in the degree of crystallization and order because of the late diagenetic evolution. In the present study, the major elements and order degree of the siliceous rocks were studied, which were from the Erlangping Group in Xixia area, Songxian area and Nanzhao area of eartern Qinling orogenic belt. As shown in the results, the siliceous rocks contained SiO2 with percentage between 84.75% and 94.12% and average of 89.09%. The SiO2/(K2O+Na2O) values were from 26.69 to 114.78 with 65.67 as its average, and the values of SiO2/Al2O3 were from 10.48 to 61.52 with average of 30.58. These above characteristics excellently agreed with the geochemical characteristics of hydrothermal siliceous rocks, which deposited in the continental margin environment. In the Raman analytical results, the quartz contributed to the characteristic Raman shifts at 394, 464, 465 and 467 cm(-1). In the results of Gaussian fitting the degrees of order increased with the order of siliceous rocks of Songxian area, Nanzhao area and Xixia area, which were witnessed by the descending in FWHM values of quartz in the siliceous rocks of Songxian area, Nanzhao area and Xixia area orderly. Disagreeing with the FWHM values of Gaussian fitting, the silica contents of the siliceous rocks had a rising trend of Songxian (87.36%), Nanzhao (89.57%), Xixia area (90.35%), which meant a descending in impurity elements with the order of Songxian area, Nanzhao area and Xixia areas. According to this, there was high agreement between lower crystallinity degree and higher purity of silica, and this denoted that the rising in order degree of silica would result in lower impurity in siliceous rocks. Although the crystallinity degrees could change with the influences of temperature, pressure and its

  8. Stable isotope fractionation by thermal diffusion through partially molten wet and dry silicate rocks

    NASA Astrophysics Data System (ADS)

    Bindeman, I. N.; Lundstrom, C. C.; Bopp, C.; Huang, F.

    2013-03-01

    Water plays a fundamental role in affecting geochemical transport and physical properties of magmas. Here we show the previously undocumented behavior of water within partially molten silicate resting in a temperature gradient, producing O, Li and H isotope redistribution by thermal diffusion leading to enrichment of light isotopes at the hot end of the gradient. After weeks to months, fully molten as well as mostly crystalline portions of water-bearing experiments develop remarkably large isotope and chemical redistributions: up to 28‰ for δ18O, 144‰ for δD, and 18‰ for δ7Li. In contrast, long-term dry experiments develop smaller (˜5‰ δ18O) isotopic fractionations only in the hotter end where it is molten or partially molten. Isotope fractionation of oxygen is linearly related to temperature, and the magnitude of isotopic separation per °C is ˜2× larger for wet experiments than dry ones. We explain this by water de-polymerizing the silicate structure leading to a smaller size of diffusing SiOx fragments. The magnitude of isotope separation between the hot and cold ends for Li, Mg, Fe, O, and H isotopes increases linearly with ΔMheavy-light/Mlight. These relationships provide predictive tests for natural rocks and highlight the role of water in isotope and compositional redistribution during temperature gradient mediated processes. We discuss the implications to natural environments in which the lightest stable isotopes (H, Li, O) with the greatest ΔMheavy-light/Mlight and fastest diffusion coefficients are capable of achieving mass-dependent redistribution in a transient temperature gradient. These experiments underscore the importance of solution-reprecipitation in wet subsolidus systems and demonstrate that isotopic redistribution can be established ˜6 orders of magnitude quicker than by diffusion through a traditional silicate melt at higher temperature. This has important implications for timescales of natural isotope and chemical

  9. Photoelectrochemical reduction of CO{sub 2} by silicate rock powders

    SciTech Connect

    Ohta, Kiyohisa; Ohguchi, Youko; Kaneco, Satoshi; Mizuno, Takayuki

    1999-06-01

    The reduction in CO{sub 2} emissions by photoelectrochemical conversion of the CO{sub 2} to formic acid and methanol using silicate rock (andesite) powders suspended in water is presented. For photoelectrochemical reduction of CO{sub 2}, a homemade cell with a platinum and a copper electrode was used. 0.1 M KHCO{sub 3} solution was used as the electrolyte. In the photoelectrochemical reduction of CO{sub 2} with a copper cathode in the catholyte dispersing andesite powder, mainly formic acid, methanol, methane, ethylene, carbon monoxide, and hydrogen were produced. Consequently, it was found that this method using a copper electrode was effective for formic acid and methanol formations from carbon dioxide.

  10. Distribution, Microfabric, and Geochemical Characteristics of Siliceous Rocks in Central Orogenic Belt, China: Implications for a Hydrothermal Sedimentation Model

    PubMed Central

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch.

    2014-01-01

    Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian—Ordovician, and Carboniferous—Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08–95.30%), Ba (42.45–503.0 ppm), and ΣREE (3.28–19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb)N, and (La/Ce)N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics. PMID:25140349

  11. Distribution, microfabric, and geochemical characteristics of siliceous rocks in central orogenic belt, China: implications for a hydrothermal sedimentation model.

    PubMed

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch

    2014-01-01

    Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian--Ordovician, and Carboniferous--Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08-95.30%), Ba (42.45-503.0 ppm), and ΣREE (3.28-19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb) N, and (La/Ce) N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics.

  12. The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer

    USGS Publications Warehouse

    Kramer, Henry

    1956-01-01

    A method has been developed for the determination of calcium in phosphate, carbonate, and silicate rocks using the Beckman flame photometer, with photomultiplier attachement. The sample is dissolved in hydrofluoric, nitric, and perchloric acids, the hydrofluoric and nitric acids are expelled, a radiation buffer consisting of aluminum, magnesium, iron, sodium, potassium, phosphoric acid, and nitric acid is added, and the solution is atomized in an oxy-hydrogen flame with an instrument setting of 554 mµ. Measurements are made by comparison against calcium standards, prepared in the same manner, in the 0 to 50 ppm range. The suppression of calcium emission by aluminum and phosphate was overcome by the addition of a large excess of magnesium. This addition almost completely restores the standard curve obtained from a solution of calcium nitrate. Interference was noted when the iron concentration in the aspirated solution (including the iron from the buffer) exceeded 100 ppm iron. Other common rock-forming elements did not interfere. The results obtained by this procedure are within ± 2 percent of the calcium oxide values obtained by other methods in the range 1 to 95 percent calcium oxide. In the 0 to 1 percent calcium oxide range the method compares favorably with standard methods.

  13. Spatial distribution of microbial populations and carbon cycle in the subsurface environment of the Horonobe area, Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Amano, Y.; Ise, K.; Terashima, M.; Sasaki, Y.; Amamiya, H.; Yoshikawa, H.

    2014-12-01

    Microorganisms are widely distributed in the subsurface environments. However, the distribution, role and rate of metabolisms, and the source of their activity are not well known. In this study, we investigated deep groundwater samples from sedimentary rocks, containing saturated methane and CO2, using boreholes at the Horonobe Underground Research Laboratory (URL), northern Hokkaido, Japan. The hydrochemical conditions of groundwaters, such as in-situ water pressure, temperature, electric conductivity, pH, redox potential, were monitored without degassing at multiple intervals along the borehole. Groundwater samples were taken periodically and chemical composition was analyzed using ICP-MS, etc. Cell counts were in the range of 103 to 105 cells ml-1. Molecular analyses revealed the spatial distribution and heterogeneity of the microbial population. Abundant methanogens were detected in the groundwater, and 80% of them were related to either Methanoregula boonei or Methanobacterium flexile that can utilize H2/CO2 by methanogenesis. Phylotypes clustered within the phylum Firmicutes, beta-Proteobacteria, delta-Proteobacteria and candidate division TM7 were dominant in the groundwater samples. Laboratory experiments using a culture technique showed that humic substances purified from the groundwater at Horonobe area appear to be degraded by microorganisms. Our results suggest that microbial spatial distributions in the subsurface environment were correlated closely with geochemical conditions, such as redox condition and carbon sources. In addition, it is inferred that humic substances are one of the important carbon sources for the subsurface microbial redox processes in the environment. This study was partly funded by the Ministry of Economy, Trade and Industry of Japan.

  14. Thick sequences of silicate and carbonate rocks of sedimentary origin in North America an interim report

    USGS Publications Warehouse

    Love, John David

    1956-01-01

    Thick sequences of silicate and carbonate rocks of sedimentary origin have been investigated in 64 areas in North America. The areas containing the thickest and most homogeneous stratigraphic sections more than 1,000 feet thick, buried at depths greater than 10,000 feet are: 1. Uinta Basin, Utah, where the Mancos shale is 1,300 to 5,000 feet thick, the Weber sandstone is 1,000 to 1,600 feet thick, and Mississippian limestones are 1,000 to 1,500 feet thick. 2. Washakie Basin, Wyoming, and Sand Wash Ba.sin, Colorado, where the Lewis shale is 1,000 to 2,000 feet thick and the Cody-Mancos shale is 4,500 to 5,500 feet thick. 3. Green River Basin, Wyoming, where the Cody-Hilliard-Baxter-Mancos shale sequence averages more than 3,000 feet, the siltstone and shale of the Chugwater formation totals 1,000 feet, and the Madison limestone ranges from 1,000 to 1,400 feet thick. 4. Red Desert (Great Divide) Basin, Wyoming, where the Cody shale is 4,000 feet thick. 5. Hanna Basin, Wyoming, where the Steele shale is 4,500 feet thick. 6. Wind River Basin, Wyoming, where the Cody shale is 3,600 to 5,000 feet thick. Geochemical characteristics of these rocks in these areas are poorly known but are being investigated. A summary of the most pertinent recent ana1yses is presented.

  15. Photoelectrochemical reduction of CO{sub 2} using silicate rock powder

    SciTech Connect

    Ohta, Kiyohisa; Ohguchi, Youko; Kaneco, Satochi

    1996-12-31

    Until now, numerous investigators have reported chemical fixation of carbon dioxide, such as electrochemical, photochemical and photoelectrochemical reductions. In these methods, relatively, a few studies on the photoelectrochemical conversion of CO{sub 2} have been reported. We have recently presented a photochemical reduction of carbon dioxide and hydrogen formation by using andesite sands as a photocatalyst under sunlight irradiation. At ambient temperature and atmospheric pressure, 6.5 {times} 10{sup -2} ml g{sup -1} methane and 7.0 {times} 10{sup -2} ml g{sup -1} of hydrogen were formed from carbon dioxide and water on the andesite. This report presents the photoelectrochemical reduction of CO{sub 2} using silicate rock (andesite) powder suspended in water. Carbon dioxide is the end product to complete combustion of all fossil fuels. The generation of carbon dioxide is the primary cause for the greenhouse effect. However, carbon dioxide is a potential carbon source. To utilize such a plentiful carbon source, it has been considered carbon dioxide as a feedstock for organic synthesis of carbonyl- and carboxyl-containing compounds or as an oxidant for oxidative synthesis of more valuable organics.

  16. Deep carbon cycle recorded by calcium-silicate rocks (rodingites) in a subduction-related ophiolite

    NASA Astrophysics Data System (ADS)

    Dai, J. G.; Wang, C. S.; Liu, S. A.; Qian, X. Y.; Zhu, D. C.; Ke, S.

    2016-11-01

    Carbon cycling in subduction zones remains poorly constrained due to the lack of relevant geological records. Here we report magnesium isotope data (δ26MgDSM3) from calcium-silicate rocks (rodingites) from the Xigaze ophiolite, southern Tibet, which is thought to represent remnants of Neo-Tethyan oceanic lithosphere. Behaviors of immobile trace elements in rodingites resemble those of their mafic dike protoliths, showing subduction-related signatures. The majority of rodingites exhibits low δ26Mg values of -0.72‰ to -0.33‰ with a weighted average of -0.47 ± 0.11‰ (2 SD), significantly lighter than that of their protoliths (-0.31 ± 0.03‰). This difference likely reflects the interaction of the protolith with isotopically light carbonate fluids. Modeling indicates that this hypothesis requires the input of 5 to 15 wt % carbonates during rodingitization. Our study suggests that rodingite may represent a previously unrecognized reservoir of dissolved Ca from subducted carbonates.

  17. Oxygen isotope geochemistry of the silicic volcanic rocks of the Etendeka-Parana province: Source constraints

    SciTech Connect

    Harris, C.; Milner, S.C.; Armstrong, R.A. ); Whittingham, A.M. )

    1990-11-01

    Oxygen isotope ratios of pyroxene phenocrysts in the silicic volcanic rocks from the Cretaceous Etendeka-Parana flood basalt province (Namibia, South America) are believed to reflect the {delta}{sup 18}O values of the original magmas. The authors recognize a high {delta}{sup 18}O value type ({delta}{sup 18}O pyroxene {approximately} +10{per thousand}) found in the south of both regions, and a low {delta}{sup 18}O value type ({delta}{sup 18}O pyroxene {approximately} +6.5{per thousand}) found in the north. Other differences between thee two rhyolite types include higher concentrations of incompatible elements and lower initial {sup 87}Sr/{sup 86}Sr ratios in the low {delta}{sup 18}O value type. The authors suggest that the regional distribution of rhyolite types reflects differences in source composition, which can best be explained if the sources are lower crustal, Late Proterozoic mobile belt material (high {delta}{sup 18}O) and Archean lower crust (low {delta}{sup 18}O).

  18. The Distribution and Composition Characteristics of Siliceous Rocks from Qinzhou Bay-Hangzhou Bay Joint Belt, South China: Constraint on the Tectonic Evolution of Plates in South China

    PubMed Central

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Zhou, Yongzhang; Yang, Zhijun; He, Junguo; Liang, Jin; Zhou, Liuyu

    2013-01-01

    The Qinzhou Bay-Hangzhou Bay joint belt is a significant tectonic zone between the Yangtze and Cathaysian plates, where plentiful hydrothermal siliceous rocks are generated. Here, the authors studied the distribution of the siliceous rocks in the whole tectonic zone, which indicated that the tensional setting was facilitating the development of siliceous rocks of hydrothermal genesis. According to the geochemical characteristics, the Neopalaeozoic siliceous rocks in the north segment of the Qinzhou Bay-Hangzhou Bay joint belt denoted its limited width. In comparison, the Neopalaeozoic Qinzhou Bay-Hangzhou Bay joint belt was diverse for its ocean basin in the different segments and possibly had subduction only in the south segment. The ocean basin of the north and middle segments was limited in its width without subduction and possibly existed as a rift trough that was unable to resist the terrigenous input. In the north segment of the Qinzhou Bay-Hangzhou Bay joint belt, the strata of hydrothermal siliceous rocks in Dongxiang copper-polymetallic ore deposit exhibited alternative cycles with the marine volcanic rocks, volcanic tuff, and metal sulphide. These sedimentary systems were formed in different circumstances, whose alternative cycles indicated the release of internal energy in several cycles gradually from strong to weak. PMID:24302882

  19. The distribution and composition characteristics of siliceous rocks from Qinzhou Bay-Hangzhou Bay joint belt, South China: constraint on the tectonic evolution of plates in South China.

    PubMed

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Zhou, Yongzhang; Yang, Zhijun; He, Junguo; Liang, Jin; Zhou, Liuyu

    2013-01-01

    The Qinzhou Bay-Hangzhou Bay joint belt is a significant tectonic zone between the Yangtze and Cathaysian plates, where plentiful hydrothermal siliceous rocks are generated. Here, the authors studied the distribution of the siliceous rocks in the whole tectonic zone, which indicated that the tensional setting was facilitating the development of siliceous rocks of hydrothermal genesis. According to the geochemical characteristics, the Neopalaeozoic siliceous rocks in the north segment of the Qinzhou Bay-Hangzhou Bay joint belt denoted its limited width. In comparison, the Neopalaeozoic Qinzhou Bay-Hangzhou Bay joint belt was diverse for its ocean basin in the different segments and possibly had subduction only in the south segment. The ocean basin of the north and middle segments was limited in its width without subduction and possibly existed as a rift trough that was unable to resist the terrigenous input. In the north segment of the Qinzhou Bay-Hangzhou Bay joint belt, the strata of hydrothermal siliceous rocks in Dongxiang copper-polymetallic ore deposit exhibited alternative cycles with the marine volcanic rocks, volcanic tuff, and metal sulphide. These sedimentary systems were formed in different circumstances, whose alternative cycles indicated the release of internal energy in several cycles gradually from strong to weak.

  20. Fluid and rock interactions in silicate and aluminosilicate systems at elevated pressure and temperature

    NASA Astrophysics Data System (ADS)

    Davis, Mary Kathleen

    Understanding fluid chemistry in the subduction zone environment is key to unraveling the details of element transport from the slab to the surface. Solubilities of cations, such as silicon, in water strongly affect both the physical and chemical properties of supercritical metamorphic fluids. Modeling the thermodynamics of fluid-rock interactions requires therefore a profound understanding of cation dissolution and aqueous speciation. In situ Raman experiments of the silica-water, alumina-water, and alumina water systems were performed in an externally heated Bassett-type diamond-anvil cell at the Department of Geological Sciences, University of Michigan. Natural quartz samples and synthetic ruby samples were used in the experiments. Samples were loaded in the sample chamber with a water pressure medium. All experiments used rhenium gaskets of uniform thickness with a 500 mum drill hole for the sample chamber. Temperature was measured using K-type thermocouples encompassing both the upper and lower diamond anvils. Pressures are obtained on the basis of the Raman shift of the 464 cm-1 quartz mode where possible or the Raman shift of the tips of the diamond anvils according to a method developed in this work. This work characterizes the state of stress in the diamond anvil cell, which is used as the basis for the pressure calibration using only the diamond anvils. Raman measurements of silicate fluid confirm the presence of H4 SiO4 and H6Si2O7 in solution and expand the pressure range for in-situ structural observations in the silica-water system. Additionally, we identify the presence of another silica species present at mantle conditions, which occurs at long time scales in the diamond cell. This study provides the first in situ data in the alumina-water and alumina-silica-water systems at pressures and temperatures relevant to the slab environment. Al(OH) 3 appears to be the dominant form of alumina present under these conditions and in the alumina

  1. Paleoceanographic and tectonic controls on deposition of the Monterey formation and related siliceous rocks in California

    USGS Publications Warehouse

    Barron, J.A.

    1986-01-01

    The timing of paleoceanographic and tectonic events that shaped the deposition of the Monterey Formation of California and related siliceous rocks has been determined by application of a refined biochronology. The base of the Monterey at 17.5 Ma coincides with rising global sea level and a switch in biogenous silica deposition from the Caribbean and low-latitude North Atlantic to the North Pacific. Major polar cooling, which began at 15 Ma, postdates the base of the Monterey by more than 2 Ma and cannot be invoked to cause the deposition of diatomaceous sediments occurring in the lowermost Monterey. Later polar cooling in the early late Miocene, however, apparently caused increased upwelling and deposition of purer diatomites in the upper Monterey. The top of the Monterey at about 6 Ma coincides with a major sea level drop and is commonly marked by an unconformity. Equivalent unconformities are widespread around the rim of the North Pacific and typically separate more pelagic sediments from overlying sediments with a greater terrigenous component. Above the Monterey, diatoms persist in California sediments to 4.5-4.0 m.y., where their decline coincides with increased deposition of diatoms in the Antarctic. Carbon isotope records in the Pacific and Indian Oceans record storage of 12C in the Monterey Formation and equivalent organic-rich sediments around the rim of the North Pacific. A +1.0??? excursion in ?? 13C beginning at 17.5 Ma coincides with rising sea level and probably reflects storage of organic material in Monterey-like marginal reservoirs. A reverse -1.0??? shift at 6.2 Ma closely approximates the top of the Monterey and may represent erosion of these marginal reservoirs and reintroduction of stored organic carbon into the ocean-atmosphere system. Initiation of transform faulting and extension in the California margin in the latest Oligocene and early Miocene caused the subsidence of basins which later received Monterey sediments. A major tectonic event

  2. Glacial-interglacial variability of atmospheric CO2 due to changing continental silicate rock weathering: A model study

    NASA Astrophysics Data System (ADS)

    Munhoven, Guy; FrançOis, Louis M.

    1996-09-01

    An 11-box model of the oceanic carbon cycle including sedimentary processes is used to explore the role chemical weathering of continental silicate rocks might play in driving atmospheric CO2 levels on glacial-interglacial timescales. Histories for the consumption of CO2 by silicate rock weathering processes are derived from the marine Ge/Si record. Taking the major uncertainties in the knowledge of the Ge and Si cycles into account, several histories for the evolution of the riverine dissolved silica fluxes are calculated from this record. The investigation of the systematics between riverine dissolved silica and bicarbonate fluxes under different weathering regimes leads us to the tentative conclusion that although there is no correlation between dissolved silica and total bicarbonate concentrations in the major rivers, there may exist a negative correlation between weathering intensity and the ratio of dissolved silica to bicarbonate derived from silicate weathering alone. With this correlation as a working hypothesis, it is possible to interpret the dissolved silica fluxes in terms of equivalent CO2 consumption rates. The calculated histories indicate that glacial rates of CO2 consumption by chemical silicate rock weathering could have been twice, and possibly up to 3.5 times, as high as they are today. When used to force the carbon cycle model, they are responsible for glacial-interglacial pCO2 variations in the atmosphere of typically 50-60 ppm and up to 95-110 ppm. These variations are superimposed to a basic oscillation of 60 ppm generated by the model, mainly in response to coral reef buildup and erosion processes. The total pCO2 signal has an amplitude of about 80-90 ppm and up to 125-135 ppm. Although these large amplitudes indicate that silicate weathering processes should be taken into account when studying glacial-interglacial changes of CO2 in the atmosphere, it also raises new problems, such as too high CO2 levels during the period from 110-70 kyr B

  3. Primary relationships of basaltic intrusive rocks and siliceous sedimentary rocks in the Northern Chichibu Belt, Shikoku Island, southwest Japan

    NASA Astrophysics Data System (ADS)

    Tsuji, Tomohiro; Sakakibara, Masayuki; Hori, Rie S.

    2014-01-01

    Understanding the primary relationships between basaltic rocks and fossiliferous sedimentary rocks provides direct information on the timing and geologic setting of past oceanic igneous activity. Though the basalts associate with cherts in the Northern Chichibu Belt have been petrographically identified as OIA/OIT or MORB, such primary relationships of them are not well understood.

  4. Chemistry of the rock-forming silicates: Multiple-chain, sheet, and framework structures

    NASA Astrophysics Data System (ADS)

    Papike, J. J.

    1988-08-01

    The crystal chemistry of 16 groups of multiple-chain, sheet, and framework silicates is reviewed. Crystal structure drawings are presented to illustrate crystal chemical features necessary to interpret chemical data for each mineral group. The 16 silicate groups considered in this review are the amphibole; nonclassical, ordered pyriboles; mica; pyrophyllite-talc; chlorite; greenalite; minnesotaite; stilpnomelane; prehnite; silica polymorphs; feldspar; nepheline-kalsilite; leucite-analcite; sodalite group; cancrinite group; and scapolite. Electron microprobe analyses should be augmented by independent determinations of Fe2+/Fe3+ and H2O for many of the silicate groups discussed and by determinations of CO32-, SO42-, S2-, and Li in some of the others. However, microprobe data augmented as suggested will still be ambiguous for some of the silicate groups considered here because the structures are not completely determined or are variable, with disparate domains and/or structural modulations, e.g., pyriboles, greenalite, minnesotaite, and stilpnomelane. Nevertheless, the most rigorous way to interpret silicate mineral chemical data is based on the crystal structures involved.

  5. Lithium isotope ratios measured in scottish rivers and weathering of old silicate rocks.

    NASA Astrophysics Data System (ADS)

    Vigier, N.; Reynolds, B. C.; Burton, K. W.; Rogers, N. W.

    2003-04-01

    Silicate weathering is often considered as one of the most important sinks of atmospheric CO2 over geological timescales, but the palaeovariations of the silicate weathering rates are still debated and depend on the reliability of the chosen proxies. It has recently been suggested that Li isotopes significantly fractionate during continental erosion (Huh et al., 1999), and that 7Li measured in large rivers could mainly reflect the degree of silicate weathering at large scales. Two main reasons have been proposed, the high Li contents in silicate minerals relative to carbonates, and the preferential uptake of 6Li by secondary clay minerals. Nevertheless, very few measurements have been made either on source minerals or on weathering products. In principle, the study of small silicated catchments should allow us to better constrain the factors controlling the fractionation of Li isotopes. A previous study has shown that 7Li measured in Icelandic basaltic rivers displays a large range (from 10 to 25.3) which correlates well with estimated weathering rates (Gislason et al., 1996). Here we present results for about 15 rivers located in Northern Scotland, which show little evidence for anthropogenic contamination, and draining mainly old silicated terrains (>500Ma). These rivers have been sampled twice, in May and in October 2002, in order to constrain the seasonal variations of the Li signature. Major and trace elements have also been measured, as well as the dissolved organic carbon. All rivers have very low Ca/Na and Mg/Na ratios (average of 0.38 and 0.17 respectively), that corresponds to the end-member previously defined for silicate rivers (Gaillardet et al, 1999), suggesting negligible contribution from carbonate dissolution. Li contents range between 0.2 and 1.2 ppb and are significantly greater than in Iceland rivers (up to 0.09 ppb). First results for the May 2002 samples show a restricted range in 7Li (from 16 to 22

  6. Exploring Iron Silicate Precursors of Ancient Iron Formations through Rock Record, Laboratory and Field Analogue Investigations

    NASA Astrophysics Data System (ADS)

    Johnson, J. E.; Rasmussen, B.; Muhling, J.; Benzerara, K.; Jezequel, D.; Cosmidis, J.; Templeton, A. S.

    2016-12-01

    In direct contrast to today's oceans, iron-rich chemical precipitates dominate the deep marine sedimentary record > 2.3 billion years ago. The deposition of these minerals resulted in massive iron formations and indicate that the ocean was previously ferruginous and largely anoxic. To precipitate and concentrate iron in the sediments, many hypotheses have centered on the oxidation of soluble Fe(II) to solid Fe(III)-oxyhydroxides; these ideas have stimulated extensive research using iron-oxidizing bacteria to produce Fe(III)-oxides and trace metal sorption experiments on Fe(III)-oxides, leading to inferences of trace metal availability and implications for enzymatic and microbial evolution as well as pO2 levels and seawater chemistry. However, recent discoveries of disseminated iron-silicate nanoparticles in early-silicifying chert indicate that iron-silicates may have instead been the primary precipitates from these Archean ferruginous oceans (Rasmussen et al, 2015). Considering the significant paradigm shift this discovery implies for interpretations of Archean elemental cycling, redox state and potential microbial metabolisms, we investigated these iron-silicate inclusions and their implications for ancient seawater chemistry in a multi-faceted approach using spectroscopic- and diffraction-based techniques. The crystal structure, Fe oxidation state and Fe coordination environment of iron-silicate nanoparticles have been interrogated using microscale X-ray absorption spectroscopy, TEM and nanoscale scanning transmission X-ray microscopy. To further explore the chemical and potential biological controls on iron-silicate formation, we have also performed laboratory experiments to mimic Archean seawater and precipitate iron-bearing silicate minerals under abiotic conditions and in the presence of iron-oxidizing bacteria. In a complementary study, sediments from a natural Archean analogue system were sampled to determine if iron-silicate minerals form in Mexican

  7. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS

    NASA Astrophysics Data System (ADS)

    Gualda, G. A.; Ghiorso, M. S.; Begue, F.; Pamukcu, A. S.; Gravley, D. M.

    2013-12-01

    Constraining the pressure of crystallization of magmas is an important but elusive task. We propose here a method to derive crystallization pressures for rocks that preserve glass compositions (either glass inclusions or matrix glass) representative of equilibration between melt, quartz, and 1 or 2 feldspars. The method relies on the shift of the quartz-feldspar saturation surface towards higher silica with decreasing pressure. The critical realization is that melt, quartz and feldspars need to be in equilibrium at the liquidus for the melt composition of interest. Thus, this method consists of calculating the saturation surfaces for quartz and feldspars using rhyolite-MELTS over a range of pressures, and searching for the pressure at which the expected assemblage (quartz+1 feldspar or quartz+2 feldspars) is found at the liquidus. We evaluate errors resulting from uncertainties in glass composition using Monte Carlo simulations, which reveal errors of ~20-45 MPa for the quartz+2 feldspars constraint and of ~25-100 MPa for the quartz+1 feldspar constraint; actual errors are likely closer to the lower bounds of these ranges. We demonstrate that the effect of fluid-saturation is more important at higher pressures (~300 MPa) than at lower pressures (~100 MPa), but reasonable pressure estimates can be derived irrespective of fluid saturation for geologically relevant H2O concentrations (>3 wt. %). And, we show that pressures calculated using the rhyolite-MELTS geobarometer compare well with those resulting from H2O-CO2 glass inclusion barometry and Al-in-hornblende barometry for an array of natural systems for which data has been compiled from the literature. We apply the rhyolite-MELTS barometer to three systems we are currently studying in detail: (1) For the Bishop Tuff (CA, USA), we find that quartz-hosted glass inclusion compositions yield indistinguishable crystallization pressures for early-erupted and late-erupted pumice, consistent with the Bishop Tuff having

  8. La-Ce and Sm-Nd systematics of siliceous sedimentary rocks: A clue to marine environment in their deposition

    SciTech Connect

    Hiroshi Shimizu; Masayo Amano; Akimasa Masuda )

    1991-04-01

    La-Ce isotopic data, together with Sm-Nd isotopic data, were determined on siliceous sedimentary rocks (cherts) in order to elucidate the rare earth element (REE) character of their sources and the nature of their depositional environments. The cherts studied are a late Archean chert from the Gorge Creek Group in the Pilbara block of Western Australia, Triassic cherts from central Japan, and Cretaceous and Paleogene deep-sea cherts from the central Pacific and the Caribbean Sea. The Archean chert from the Gorge Creek Group shows chondritic Ce and Nd isotope ratios at its sedimentation age which indicate that its sources had a time-integrated chondritic REE pattern. Triassic cherts from Japan have initial Ce and Nd isotope ratios that show a direct derivation from their continental source. On the other hand, for Cretaceous and Paleogene deep-sea cherts having negative Ce anomalies in their REE patterns, two different sources for Ce and Nd are revealed from their initial Ce and Nd isotope data: Ce from long-term light-REE-depleted oceanic volcanic rocks and Nd from light-REE-enriched continental rocks. The reverse nature observed for deep-sea cherts is considered to be a reflection of their depositional environment far from a continent. These results confirm that the La-Ce isotope system is highly useful in determining the nature and cause of Ce anomalies observed in marine sedimentary rocks such as chert.

  9. The flame photometric determination of calcium in phosphate, carbonate, and silicate rocks

    USGS Publications Warehouse

    Kramer, H.

    1957-01-01

    A flame photometric method of determining calcium in phosphate, carbonate, and silicate locks has been developed Aluminum and phosphate interference was overcome by the addition of a large excess of magnesium. The method is rapid and suitable for routine analysis Results obtained are within ?? 2% of the calcium oxide content. ?? 1957.

  10. Experimental high strain-rate deformation products of carbonate-silicate rocks: Comparison with terrestrial impact materials

    NASA Astrophysics Data System (ADS)

    van der Bogert, C. H.; Schultz, P. H.; Spray, J. G.

    2008-09-01

    Introduction. The response of carbonate to impact processes has thus far been investigated using a combination of thermodynamic modelling, shock experiments, and impact experiments. Localized shear deformation was suggested to play an important role in the failure of carbonate during some shock experiments [1,2], and was invoked to explain significant degassing of carbonates during oblique impact experiments [3]. The results of the impact experiments are at odds with experiments [4] that show back-reaction of CO2 with CaO and MgO could significantly reduce CO2 degassing during impact events. We performed a frictional-welding experiment in order to investigate the effects of high strain-rate deformation on carbonate-silicate target materials, exclusive of shock deformation effects, and to investigate the differing results of other experiments. Samples and Techniques. A frictional melting experiment was performed using dolomitic marble and quartzite samples to simulate conditions during an impact into carbonate-silicate target rocks. The experiment followed the method of Spray (1995) [5]. The 1.5 cm3 samples were mounted onto separate steel cylinders with epoxy. Using a Blacks FWH-3 axial friction-welding rig, the samples were brought into contact at room temperature and under dry conditions with ~5 MPa applied pressure. Contact was maintained for two seconds at 750 rpm for a sustained strain-rate of 102 to 103 s-1. Results. Vapor or fine dust escaped from the interface during the experiment. Immediately after sample separation, the interfaces were incandescent. Once cooled, opaque white material adhered to both the quartzite and dolomitic marble samples. Quartzite sample. Material was injected into cracks that formed in the quartzite sample. Cooling and crystallization of the friction products resulted in the formation of submicron-sized minerals such as periclase and Ca- and Ca,Mg-silicates (Fig. 1) including merwinite and åkermanite. While periclase was observed

  11. Trace Elements in Olivine in Italian Potassic Volcanic Rocks Distinguish Between Mantle Metasomatism by Carbonatitic and Silicate Melts

    NASA Astrophysics Data System (ADS)

    Foley, S. F.; Ammannati, E.; Jacob, D. E.; Avanzinelli, R.; Conticelli, S.

    2014-12-01

    The Italian Peninsula is the site of intense subduction-related potassic magmatism with bimodal character in terms of silica activity: Ca-poor silica-saturated lamproitic rocks and Ca-enriched silica-undersaturated leucitites. Lamproitic magmas formed in the early phases of magmatic activity and were followed by leucititic magmas. The primary magmas are generated in the sub-continental lithospheric mantle at the destructive plate margin, and both series have olivine as the first crystallizing phenocrysts. Trace elements in olivine phenocrysts are important in recognizing metasomatic effects on the mineralogy of the mantle source. Since Ni is the most compatible trace element in olivine, particularly in alkaline melts, modal changes of olivine in the source strongly affect its bulk partition coefficient, and therefore its content in primary melts and in olivine that crystallizes from them.The concentration of other compatible trace elements (e.g. Mn, Co) in olivine phenocrysts also depends on the abundance of olivine in the magma source. Ni contents in olivine of the Italian rocks show a clear bimodal distribution. Olivine from lamproitic samples has systematically higher Fo and Ni contents, whereas olivine from leucititic rocks never exceeds Fo92 and has markedly lower Ni, reaching among the lowest levels ever observed in olivine phenocrysts in primitive melts. The Mn/Fe ratio of olivine is also sensitive to changes of the modal abundance of olivine in the source, 100*Mn/Fe of olivine from lamproitic rocks never exceeds 2, while it is always >1.8 in leucititic rocks, meaning that the leucitite source regions are much richer in olivine. Lithium is generally enriched in the crust and in sediments compared to the lithospheric mantle and to mantle-derived melts,so that Li in olivine above 10 ppm is suggested to indicate recycled sediments. Li contents are up to 35 ppm in leucititic olivines and up to >50 ppm in lamproitic olivines, confirming the recycling of crustal

  12. Dissolution of glass wool, rock wool and alkaline earth silicate wool: morphological and chemical changes in fibers.

    PubMed

    Campopiano, Antonella; Cannizzaro, Annapaola; Angelosanto, Federica; Astolfi, Maria Luisa; Ramires, Deborah; Olori, Angelo; Canepari, Silvia; Iavicoli, Sergio

    2014-10-01

    The behavior of alkaline earth silicate (AES) wool and of other biosoluble wools in saline solution simulating physiological fluids was compared with that of a traditional wool belonging to synthetic vitreous fibers. Morphological and size changes of fibers were studied by scanning electron microscopy (SEM). The elements extracted from fibers were analyzed by inductively coupled plasma atomic emission spectrometry. SEM analysis showed a larger reduction of length-weighted geometric mean fiber diameter at 4.5 pH than at 7.4 pH. At the 7.4 pH, AES wool showed a higher dissolution rate and a dissolution time less than a few days. Their dissolution was highly non-congruent with rapid leaching of calcium. Unlike rock wool, glass wool dissolved more rapidly at physiological pH than at acid pH. Dissolution of AES and biosoluble rock wool is accompanied by a noticeable change in morphology while by no change for glass wool. Biosoluble rock wool developed a leached surface with porous honeycomb structure. SEM analysis showed the dissolution for glass wool is mainly due to breakage transverse of fiber at pH 7.4. AES dissolution constant (Kdis) was the highest at pH 7.4, while at pH 4.5 only biosoluble rockwool 1 showed a higher Kdis.

  13. Petrogenesis of mafic magma and associated silicic magma for calk-alkaline rocks in the Shirataka volcano, NE Japan

    NASA Astrophysics Data System (ADS)

    Hirotani, S.; Ban, M.; Nakagawa, M.

    2009-12-01

    Eruptive products of Shirataka volcano (0.9-0.7 Ma) in NE Japan are calc-alkaline andesite-dacite (57-66% SiO2), and are divided into six petrologic groups (G1-6). Mafic inclusions (48-58% SiO2) are always observed in G1, G2, G5 and G6. The host rocks as well as inclusions are mixed rocks formed between mafic and silicic end-members judging from many petrologic aspects. Based on petrologic data of more than 30 mafic inclusion-host pairs in these groups, we revealed the petrologic features of the end-member magmas and examined their petrogenesis. The mixing trends defined by hosts and inclusions are divided into high- and low-Cr types. Both types coexist in G1, G2 and G5, while G6 lacks high-Cr type. In the same group, the mafic end-member for high-Cr type shows more primitive features (e.g. in G5; 1140-1160°C, 50% SiO2, Fo-rich olv + Mg-rich cpx + An-rich plg phenocrysts) than that for the low-Cr type (e.g. in G5; c. 1100°C, 51% SiO2, Mg-rich cpx + An-rich plg phenocrysts). The silicic end-members for the two types show similar mineral assemblage (e.g. in G5; hbl + qtz + Mg-poor px + An-poor plg phenocrysts) but are different in bulk compositions (e.g. in G5; high-Cr type, 67% SiO2; low-Cr type, 66% SiO2). Significantly, in a petrologic group, the high-Cr type mafic and corresponding silicic end-members have lower values in 87Sr/86Sr ratio than the low-Cr type ones. Further, the bulk compositions of each type end-members show slight variability among petrologic groups. For example, Sr isotopic ratios and SiO2 contents of high-Cr type mafic end-members are 0.7037 and 48% in G1, 0.7039 and 51% in G2, and 0.7042 and 50% in G5, respectively. The MELTS and geochemical model calculations have shown that the low-Cr type mafic end-member magma can be produced through c. 20% fractional crystallization (olv + plg) from the high-Cr type mafic end-member magma accompanied with the assimilation of basement plutonic rocks (r=0.02-0.05) in the case of G5. In terms of associated

  14. Tungsten residence in silicate rocks: implications for interpreting W isotopic compositions

    NASA Astrophysics Data System (ADS)

    Liu, J.; Pearson, G. D.; Chacko, T.; Luo, Y.

    2015-12-01

    High-precision measurements of W isotopic ratios have boosted recent exploration of early Earth processes from the small W isotope anomalies observable in some Hadean-Archean rocks. However, before applying W isotopic data to understand the geological processes responsible for the formation of these rocks, it is critical to evaluate whether the rocks' present W contents and isotopic compositions reflect that of the protolith or the effects of secondary W addition/mobilization. To investigate this issue, we have carried out in situ concentration measurements of W and other HFSEs in mineral phases and alteration assemblages within a broad spectrum of rocks using LA-ICP-MS. Isotope dilution whole-rock W concentration measurements are used along with modes calculated from mineral and bulk rock major element data to examine the mass balance for W and other elements. In general, W is positively correlated with Nb, Ta, Ti, Sn, Mo and U, indicating similar geochemical behavior. Within granitic gneisses and amphibolites, biotite, hornblende, titanite and ilmenite control the W budget, while plagioclase and k-feldspar have little effect. For granulites, pyroxenites and eclogites, titanite, rutile, ilmenite, magnetite and sulfide, as well as grain boundary alteration assemblages dominate the W budget, while garnet, clinopyroxene, orthopyroxene and plagioclase have little or no W. Within mantle harzburgites and dunites, major phases such as olivine, clinopyroxene, orthopyroxene and spinel/chromite have very low concentrations of W, Nb, Ta, Sn and Mo. Instead, these elements are concentrated along grain boundaries and within sulfide/mss. Mass balance shows that for granitic gneisses and amphibolites, the rock-forming minerals can adequately account for the whole-rock W budget, whereas for ultramafic rocks such as pyroxenites, eclogites and harzburgites and dunites, significant W is hosted along grain boundaries, indicating that metamorphism and melt/fluid metasomatism can

  15. Petrogenesis of siliceous high-Mg series rocks as exemplified by the Early Paleoproterozoic mafic volcanic rocks of the Eastern Baltic Shield: enriched mantle versus crustal contamination

    NASA Astrophysics Data System (ADS)

    Bogina, Maria; Zlobin, Valeriy; Sharkov, Evgenii; Chistyakov, Alexeii

    2015-04-01

    The Early Paleoproterozoic stage in the Earth's evolution was marked by the initiation of global rift systems, the tectonic nature of which was determined by plume geodynamics. These processes caused the voluminous emplacement of mantle melts with the formation of dike swarms, mafic-ultramafic layered intrusions, and volcanic rocks. All these rocks are usually considered as derivatives of SHMS (siliceous high-magnesian series). Within the Eastern Baltic Shield, the SHMS volcanic rocks are localized in the domains with different crustal history: in the Vodlozero block of the Karelian craton with the oldest (Middle Archean) crust, in the Central Block of the same craton with the Neoarchean crust, and in the Kola Craton with a heterogeneous crust. At the same time, these rocks are characterized by sufficiently close geochemical characteristics: high REE fractionation ((La/Yb)N = 4.9-11.7, (La/Sm)N=2.3-3.6, (Gd/Yb)N =1.66-2.74)), LILE enrichment, negative Nb anomaly, low to moderate Ti content, and sufficiently narrow variations in Nd isotope composition from -2.0 to -0.4 epsilon units. The tectonomagmatic interpretation of these rocks was ambiguous, because such characteristics may be produced by both crustal contamination of depleted mantle melts, and by generation from a mantle source metasomatized during previous subduction event. Similar REE patterns and overlapping Nd isotope compositions indicate that the studied basaltic rocks were formed from similar sources. If crustal contamination en route to the surface would play a significant role in the formation of the studied basalts, then almost equal amounts of contaminant of similar composition are required to produce the mafic rocks with similar geochemical signatures and close Nd isotopic compositions, which is hardly possible for the rocks spaced far apart in a heterogeneous crust. This conclusion is consistent with analysis of some relations between incompatible elements and their ratios. In particular, the

  16. The determination of silver in silicate rocks by electrothermal atomic absorption spectrometry

    USGS Publications Warehouse

    Aruscavage, P. J.; Campbell, E.Y.

    1979-01-01

    Silver is extracted from a 20% tartaric acid solution by using butyl acetate and diphenylthiourea, and the organic layer is analyzed directly by the graphite-furnace technique. The precisions is ca. 8% as estimated from multiple analysis of 13 standard rocks; there are no systematic errors. The detection limit is 2.4 ppb for 250-mg samples. ?? 1979.

  17. Measurement of femtogram quantities of protactinium in silicate rock samples by multicollector inductively coupled plasma mass spectrometry.

    PubMed

    Regelous, Marcel; Turner, Simon P; Elliott, Tim R; Rostami, Kia; Hawkesworth, Chris J

    2004-07-01

    We describe a new method for the chemical separation and analysis of Pa in silicate rock samples by isotope dilution. Our new technique has the following advantages over previous methods: (a) The initial separation of Pa from the rock matrix is carried out using anionic exchange resin and HCl-HF mixtures, avoiding the need to remove F(-) quantitatively from the sample solution prior to this step, (b) Efficient ionization of Pa is achieved using a multicollector inductively coupled plasma mass spectrometer, so that smaller sample sizes and shorter measurement times are required, compared to previous methods using thermal ionization mass spectrometry or alpha spectrometry. (c) Plasma ionization requires less efficient separation of the high field strength elements from Pa, thus reducing reagent volumes, blanks, and sample preparation times. Instrumental mass fractionation can be corrected for using admixed U of known isotopic composition. Using this method, Pa concentrations can be measured to a precision of approximately 0.5% and an accuracy of approximately 1% using only a few tens of femtograms of Pa.

  18. Determination of thorium concentrations and activity ratios in silicate rocks by alpha spectrometry.

    PubMed

    dos Santos, R N; Marques, L S; Nicolai, S H A; Ribeiro, F B

    2004-01-01

    A detailed radiochemical procedure for alpha spectrometry measurements of thorium concentrations and of 230Th/232Th activity ratios in silicates is presented. The Th behaviour, during each step of the chemical process, was investigated by using a 234Th tracer, which is a gamma-ray emitter. The described chemical processing provides relatively high thorium yields, which varied between 56% and 88%, in the analysis of GB-1 (granite) and BB-1 (basalt) Brazilian geological standards. Also, the application of the established radiochemical method allowed a determination of both Th concentrations and activity ratios with high reproducibility, on the order of 2%. The estimation of the concentration result accuracy is also about 2%, which was calculated by using published data obtained from neutron activation analysis as reference values.

  19. Origin of karst conduits in calcareous sandstone and carbonate-silicate rocks: Complex role of insoluble material

    NASA Astrophysics Data System (ADS)

    Bruthans, Jiri; Balak, Frantisek; Schweigstillova, Jana; Vojtisek, Jan

    2017-04-01

    Carbonate karst is best developed in high-grade limestones and majority of the studies is focused on these rocks. Features developed by dissolution of calcite cement in quartz sandstones and dissolution of various carbonate-silicate rocks are studied far less frequently. Unlike in common karst, the insoluble residuum has to be washed out after dissolution to create high-permeability conduits in these rocks. Aquifers in a Bohemian Cretaceous Basin (BCB), the most important hydrogeological basin in the Czech Republic, consist mainly of quartz and calcareous sandstones to siltstones. These rocks are intercalated by thin layers of calcite-cemented sandstone and low-grade limestone, the latter sometimes partly impregnated by a secondary silica. Results of tracer tests show a high flow velocity in some of the aquifers. Springs with flow rate up to 500 l/s and wells with yield up to 200 l/s occur in these rocks. Dissolution features in BCB were however not yet studied in detail. For identification and characterization of rocks prone to karstification, 350 cores were sampled mostly from boreholes but also from rock outcrops in several areas of BCB. Cores were taken from intervals where: (i) high carbonate content was expected, (ii) conduits and enlarged porosity was observed in rock outcrops or wells, (iii) inflows to boreholes were determined by well logging. Calcium carbonate content was determined by calcimetry in all cores. All cores were leached in hydrochloric acid to observe the degree of disintegration after removal of calcite, which was far dominating portion of total carbonate. Polished sections were prepared from selected cores and Ca, Si, Na, K, Al content was automatically mapped by microprobe to visualize the calcium, silica, feldspar and clay mineral distribution in cores. Conduits were photo documented in the field. Two types of sediments with distinct disintegration characteristics were observed: (i) In sandstone composed of quartz grains cemented by

  20. Petrochemistry of late miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia

    USGS Publications Warehouse

    Morgan, VI G.B.; London, D.; Luedke, R.G.

    1998-01-01

    Late Miocene peraluminous volcanic rocks of the Morococala field, Bolivia, define a layered stratigraphy of basal andalusite-, biotite-(?? Muscovite)-bearing rhyolite tuffs (AR), overlain by cordierite-, biotite-bearing rhyolite tuffs (CR), and capped by biotite-beanng quartz latite tuffs, lavas, and late domal flows (QL). Mineral and whole-rock compositions become more evolved from top to bottom, with differentiation reflected by decreasing Ca, Ba, Mg, Fe, and rare earth elements (REE) versus increasing F, Na/K, and aluminosity from QL to AR. Mineral, whole-rock, and glass inclusion compositions are consistent with derivation of all three rock types from a single stratified magma reservoir, but age and spatial relations between the three units make this unlikely. Genesis of the QL involved biotite-dehydration melting of an aluminous source at T > 750??C and P ??? 4-6 kbar. If not co-magmatic with QL, the other units were generated primarily by muscovite-dehydration melting at T = 730-750??C and P ??? 3??5-4??5 kbar for CR, and T ??? 750??C for AR with pre-emptive residence at low pressure (1??5-3??0 kbar). Low hematite contents (XHem ??? 0??06) of ilmenite grains in AR, CR, and early grains (as inclusions in plagioclase and sanidine cores) in QL indicate reduced conditions imposed by a graphite-bearing source. Compositional variability among texturally later oxides (ilmenite with XHem = 0??06-0??50, primary magnetite), however, apparently records progressive increases in pre-eruptive f(O2) in QL. Plagioclase-melt equilibria and electron microprobe analysis difference for quartz-hosted glass inclusions suggest pre-emptive melt H2O contents ??? 5-7 wt % for the AR, ???4-6 wt % for the CR, and ???3-5 wt % for the QL.

  1. SilMush: A procedure for modeling of the geochemical evolution of silicic magmas and granitic rocks

    NASA Astrophysics Data System (ADS)

    Hertogen, Jan; Mareels, Joyce

    2016-07-01

    A boundary layer crystallization modeling program is presented that specifically addresses the chemical fractionation in silicic magma systems and the solidification of plutonic bodies. The model is a Langmuir (1989) type approach and does not invoke crystal settling in high-viscosity silicic melts. The primary aim is to model a granitic rock as a congealed crystal-liquid mush, and to integrate major element and trace element modeling. The procedure allows for some exploratory investigation of the exsolution of H2O-fluids and of the fluid/melt partitioning of trace elements. The procedure is implemented as a collection of subroutines for the MS Excel spreadsheet environment and is coded in the Visual Basic for Applications (VBA) language. To increase the flexibility of the modeling, the procedure is based on discrete numeric process simulation rather than on solution of continuous differential equations. The program is applied to a study of the geochemical variation within and among three granitic units (Senones, Natzwiller, Kagenfels) from the Variscan Northern Vosges Massif, France. The three units cover the compositional range from monzogranite, over syenogranite to alkali-feldspar granite. An extensive set of new major element and trace element data is presented. Special attention is paid to the essential role of accessory minerals in the fractionation of the Rare Earth Elements. The crystallization model is able to reproduce the essential major and trace element variation trends in the data sets of the three separate granitic plutons. The Kagenfels alkali-feldspar leucogranite couples very limited variation in major element composition to a considerable and complex variation of trace elements. The modeling results can serve as a guide for the reconstruction of the emplacement sequence of petrographically distinct units. Although the modeling procedure essentially deals with geochemical fractionation within a single pluton, the modeling results bring up a

  2. A Clinopyroxene-Plagioclase Geobarometer for A-type Silicic Volcanic Rocks

    NASA Astrophysics Data System (ADS)

    Wolff, J.; Iveson, A. A.; Davis, K.; Johnson, T. A.; Gahagan, S.; Ellis, B. S.

    2015-12-01

    Constraining the crustal storage depths of magmas is important in understanding volcanism. The reaction: anorthite (pl) = Ca-Tschermak's (cpx) + silica (Q or liq) has a large volume change and hence offers potential as a geobarometer, but has not been extensively exploited as such. One of the chief barriers to its wide application is consistent estimation of melt silica activity for assemblages that lack quartz. We have skirted this problem by confining attention to metaluminous silicic compositions (SiO2 > 60% by weight), for which silica activity during crystallization is presumed to be close to 1, and calibrated the barometer for the range 0 - 2 GPa using the LEPR database and additional experiments from the literature. Additional improvement is obtained by excluding hydrous phase-bearing assemblages. Despite the analytical uncertainties present in older experimental investigations, with knowledge of temperature, and clinopyroxene, plagioclase and host melt compositions, pressures for amphibole- and biotite-free dacites and rhyolites can be estimated to ±0.17 GPa (1 sigma). The limitations of the barometer render it most applicable to intraplate, A-type rhyolites. Application to one such system, the Snake River Plain rhyolites, indicate that both melt-hosted phenocrysts and clinopyroxene-plagioclase aggregate grains found in these rhyolites formed at low pressures, <0.5 GPa. This is consistent with isotopic evidence for a shallow crustal origin for Snake River Plain rhyolites.

  3. Interaction of rare earth elements and components of the Horonobe deep groundwater.

    PubMed

    Kirishima, Akira; Kuno, Atsushi; Amamiya, Hiroshi; Kubota, Takumi; Kimuro, Shingo; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki; Sato, Nobuaki

    2017-02-01

    To better understand the migration behavior of minor actinides in deep groundwater, the interactions between doped rare earth elements (REEs) and components of Horonobe deep groundwater were investigated. Approximately 10 ppb of the REEs, i.e. Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb were doped into a groundwater sample collected from a packed section in a borehole drilled at 140 m depth in the experiment drift of Horonobe Underground Research Laboratory in Hokkaido, Japan. The groundwater sample was sequentially filtered with a 0.2 μm pore filter, and 10 kDa, 3 kDa and 1 kDa nominal molecular weight limit (NMWL) ultrafilters with conditions kept inert. Next, the filtrate solutions were analyzed with inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of the REEs retained in solution at each filtration step, while the used filters were analyzed through neutron activation analysis (NAA) and TOF-SIMS element mapping to determine the amounts and chemical species of the trapped fractions of REEs on each filter. A strong relationship between the ratios of REEs retained in the filtrate solutions and the ionic radii of the associated REEs was observed; i.e. smaller REEs occur in larger proportions dissolved in the solution phase under the conditions of the Horonobe groundwater. The NAA and TOF-SIMS analyses revealed that portions of the REEs were trapped by the 0.2 μm pore filter as REE phosphates, which correspond to the species predicted to be predominant by chemical equilibrium calculations for the conditions of the Horonobe groundwater. Additionally, small portions of colloidal REEs were trapped by the 10 kDa and 3 kDa NMWL ultrafilters. These results suggest that phosphate anions play an important role in the chemical behavior of REEs in saline (seawater-based) groundwater, which may be useful for predicting the migration behavior of trivalent actinides released from radioactive waste repositories in the far

  4. Geochemistry and diagenesis of Miocene lacustrine siliceous sedimentary and pyroclastic rocks, Mytilinii basin, Samos Island, Greece

    USGS Publications Warehouse

    Stamatakis, M.G.; Hein, J.R.; Magganas, A.C.

    1989-01-01

    A Late Miocene non-marine stratigraphic sequence composed of limestone, opal-CT-bearing limestone, porcelanite, marlstone, diatomaceous marlstone, dolomite, and tuffite crops out on eastern Samos Island. This lacustrine sequence is subdivided into the Hora Beds and the underlying Pythagorion Formation. The Hora Beds is overlain by the clastic Mytilinii series which contains Turolian (Late Miocene) mammalian fossils. The lacustrine sequence contains volcanic glass and the silica polymorphs opal-A, opal-CT, and quartz. Volcanic glass predominantly occurs in tuffaceous rocks from the lower and upper parts of the lacustrine sequence. Opal-A (diatom frustules) is confined to layers in the upper part of the Hora Beds. Beds rich in opal-CT underlie those containing opal-A. The occurrence of opal-CT is extensive, encompassing the lower Hora Beds and the sedimentary rocks and tuffs of the Pythagorion Formation. A transition zone between the opal-A and opal-CT zones is identified by X-ray diffraction patterns that are intermediate between those of opal-CT and opal-A, perhaps due to a mixture of the two polymorphs. Diagenesis was not advanced enough for opal-CT to transform to quartz or for volcanic glass to transform to opal-C. Based on geochemical and mineralogical data, we suggest that the rate of diagenetic transformation of opal-A to opal-CT was mainly controlled by the chemistry of pore fluids. Pore fluids were characterized by high salinity, moderately high alkalinity, and high magnesium ion activity. These pore fluid characteristics are indicated by the presence of evaporitic salts (halite, sylvite, niter), high boron content in biogenic silica, and by dolomite in both the opal-A and opal-CT-bearing beds. The absence of authigenic K-feldspar, borosilicates, and zeolites also support these pore fluid characteristics. Additional factors that influenced the rate of silica diagenesis were host rock lithology and the relatively high heat flow in the Aegean region from

  5. Diagenetic and compositional controls of wettability in siliceous sedimentary rocks, Monterey Formation, California

    NASA Astrophysics Data System (ADS)

    Hill, Kristina M.

    Modified imbibition tests were performed on 69 subsurface samples from Monterey Formation reservoirs in the San Joaquin Valley to measure wettability variation as a result of composition and silica phase change. Contact angle tests were also performed on 6 chert samples from outcrop and 3 nearly pure mineral samples. Understanding wettability is important because it is a key factor in reservoir fluid distribution and movement, and its significance rises as porosity and permeability decrease and fluid interactions with reservoir grain surface area increase. Although the low permeability siliceous reservoirs of the Monterey Formation are economically important and prolific, a greater understanding of factors that alter their wettability will help better develop them. Imbibition results revealed a strong trend of decreased wettability to oil with increased detrital content in opal-CT phase samples. Opal-A phase samples exhibited less wettability to oil than both opal-CT and quartz phase samples of similar detrital content. Subsurface reservoir samples from 3 oil fields were crushed to eliminate the effect of capillary pressure and cleansed of hydrocarbons to eliminate wettability alterations by asphaltene, then pressed into discs of controlled density. Powder discs were tested for wettability by dispensing a controlled volume of water and motor oil onto the surface and measuring the time required for each fluid to imbibe into the sample. The syringe and software of a CAM101 tensiometer were used to control the amount of fluid dispensed onto each sample, and imbibition completion times were determined by high-speed photography for water drops; oil drop imbibition was significantly slower and imbibition was timed and determined visually. Contact angle of water and oil drops on polished chert and mineral sample surfaces was determined by image analysis and the Young-Laplace equation. Oil imbibition was significantly slower with increased detrital composition and faster

  6. The integration of physical rock properties, mineralogy and geochemistry for the exploration of large zinc silicate deposits: A case study of the Vazante zinc deposits, Minas Gerais, Brazil

    NASA Astrophysics Data System (ADS)

    McGladrey, Alexandra J.; Olivo, Gema Ribeiro; Silva, Adalene Moreira; Oliveira, Gustavo Diniz; Neto, Basilio Botura; Perrouty, Stéphane

    2017-01-01

    The Vazante deposit, which is the world's largest zinc silicate deposit, occurs in brecciated dolomite and comprises mainly willemite with various proportions of hematite, Fe-carbonate, minor franklinite and magnetite. Exploration for this type of deposit is more challenging than zinc sulfide deposits, as they do not exhibit similar geophysical anomalies. To improve the application of geophysical surveys to the exploration of hypogene silicate zinc deposits, data from 475 samples were investigated from drill holes representative of the various types of ore and host rocks as well as barren zones of known geophysical anomalies in the Vazante District. Lithogeochemical and mineralogical (optical, SEM and MLA) data were integrated with physical rock properties (density, magnetic susceptibility and Ksbnd Usbnd Th gamma-ray spectrometry) to assist in exploring for this type of deposit. The most distinct physical property of the ore is density, compared with the host rocks due to high proportion of denser minerals (hematite and willemite). However, barren hematite breccias also have high densities. The zinc ore and hematite breccias yielded higher magnetic susceptibilities than the surrounding host rocks, with the highest values associated with greater proportions of franklinite and magnetite. The density and magnetic susceptibility contrasts are a result of hydrothermal fluids interacting with and altering the carbonate host rocks. Zinc ore also yielded elevated U concentrations relative to the various host rocks, yielding higher gamma-ray spectrometric values. The results of this investigation indicate that an integration of magnetic, gravimetric and radiometric surveys would be required to identify zinc silicate ore zones.

  7. Chemical weathering of silicate rocks as a function of elevation in the southern Swiss Alps

    NASA Astrophysics Data System (ADS)

    Drever, James I.; Zobrist, Jürg

    1992-08-01

    Surface water and soil samples were collected from a series of small catchments on granitic gneiss in the Canton of Ticino in southern Switzerland. Elevations of the sampling points ranged from 220 to 2400 m; vegetation varied correspondingly from deciduous forest through coniferous forest to alpine pasture and essentially unvegetated rock and talus. Annual precipitation averaged 1.9 to 2.4 m. The concentrations of the major cations and silica in surface waters decreased more or less exponentially with elevation. The cationic denudation rate decreased from about 500 meq/m 2 · y at the lower elevations to about 20 meq/m 2 · y at the highest. Alkalinity decreased from 250 to about -7 μeq/1. Although total concentrations decreased with elevation, there were no clear systematic trends in the ratios of the concentrations of the major cations and silica. This suggests that the nature of the secondary minerals formed during weathering in the area does not change with elevation, despite great changes in soil type and environmental conditions. The clay mineralogy of the soils is dominated by unweathered and slightly weathered bedrock minerals: mica and chlorite, hydrobiotite, and poorly characterized mixed-layer material. Small amounts of kaolinite and smectite were observed in a few samples, but there do not appear to be any systematic trends in clay mineralogy with elevation. Mass-balance arguments suggest that the major (in terms of solute generation) weathering product is either kaolinite or a mixture of A1(OH) 3 and 2:1 clays. The lack of dependence of weathering stoichiometry on elevation (a surrogate for several environmental variables) or solute concentrations perhaps reflects the importance of local relief, which did not vary systematically with elevation.

  8. Quantitative analysis of major and trace elements in NH4HF2-modified silicate rock powders by laser ablation - inductively coupled plasma mass spectrometry.

    PubMed

    Zhang, Wen; Hu, Zhaochu; Liu, Yongsheng; Yang, Wenwu; Chen, Haihong; Hu, Shenghong; Xiao, Hongyan

    2017-08-29

    In this paper, we described a NH4HF2 digestion method as sample preparation for the rapid determination of major and trace elements in silicate rocks using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Sample powders digested by NH4HF2 at 230 °C for 3 h form ultrafine powders with a typical grain size d80 < 8.5 μm, and various silicate rocks have a consistent grain morphology and size, allowing us to produce pressed powder pellets that have excellent cohesion and homogeneity suitable for laser ablation micro-analysis without the addition of binder. The influences of the digestion parameters were investigated and optimized, including the evaporation stage of removing residual NH4HF2, sample homogenization, selection of the digestion vessel and calibration strategy of quantitative analysis. The optimized NH4HF2 digestion method was applied to dissolve six silicate rock reference materials (BCR-2, BHVO-2, AGV-2, RGM-2, GSP-2, GSR-1) covering a wide range of rock types. Ten major elements and thirty-five trace elements were simultaneously analyzed by LA-ICP-MS. The analytical results of the six reference materials generally agreed with the recommended values, with discrepancies of less than 10% for most elements. The analytical precision is within 5% for most major elements and within 10% for most trace elements. Compared with previous methods of LA-ICP-MS bulk analysis, our method enables the complete dissolution of refractory minerals, such as zircon, in intermediate-acidic intrusive rocks and limits contamination as well as the loss of volatile elements. Moreover, there are many advantages for the new technique, including reducing matrix effects between reference materials and samples, spiking the internal standard simply and feasibly and sample batch processing. The applicability filed of the new technique in this study was focused on the whole-rock analysis of igneous rock samples, which are from basic rocks to acid rocks (45%

  9. Sr isotopic characteristics in two small watersheds draining typical silicate and carbonate rocks: implication for the studies on seawater Sr isotopic evolution

    NASA Astrophysics Data System (ADS)

    Wu, W. H.; Zheng, H. B.; Yang, J. D.

    2013-06-01

    We systematically investigated Sr isotopic characteristics of small silicate watershed - the tributary Xishui River of the Yangtze River, and small carbonate watershed - the tributary Guijiang River of the Pearl River. The results show that the Xishui River has relatively high Sr concentrations (0.468-1.70 μmol L-1 in summer and 1.30-3.17 μmol L-1 in winter, respectively) and low 87Sr/86Sr ratios (0.708686-0.709148 in summer and 0.708515-0.709305 in winter), which is similar to the characteristics of carbonate weathering. The Guijiang River has low Sr concentrations (0.124-1.098 μmol L-1) and high 87Sr/86Sr ratios (0.710558-0.724605), being characterized by silicate weathering. In the Xishui River catchment, chemical weathering rates in summer are far higher than those in winter, indicating significant influence of climate regime. However, slight differences of 87Sr/86Sr ratios between summer and winter show that influence of climate on Sr isotope is uncertainty owing to very similar Sr isotope values in silicate and carbonate bedrocks. As 87Sr/86Sr ratios in the Xishui River are lower than those in seawater, they will decrease 87Sr/86Sr ratio of seawater after transported into oceans. Previous studies also showed that some basaltic watersheds with extremely high chemical weathering rates reduced the seawater Sr isotope ratios. In other words, river catchments with high silicate weathering rates do not certainly transport highly radiogenic Sr into oceans. Therefore, it may be questionable that using the variations of seawater 87Sr/86Sr ratio to indicate the continental silicate weathering intensity. In the Guijiang River catchment, 87Sr/86Sr ratios of carbonate rocks and other sources (rainwater, domestic and industrial waste water, and agricultural fertilizer) are lower than 0.71. In comparison, some non-carbonate components, such as, sand rocks, mud rocks, shales, have relatively high Sr isotopic compositions. Moreover, granites accounted for only 5% of the

  10. Carbonate- and silicate-rich globules in the kimberlitic rocks of northwestern Tarim large igneous province, NW China: Evidence for carbonated mantle source

    NASA Astrophysics Data System (ADS)

    Cheng, Zhiguo; Zhang, Zhaochong; Santosh, M.; Hou, Tong; Zhang, Dongyang

    2014-12-01

    We report carbonate- and silicate-rich globules and andradite from the Wajilitage kimberlitic rocks in the northwestern Tarim large igneous province, NW China. The carbonate-rich globules vary in size from 1 to 3 mm, and most have ellipsoidal or round shape, and are composed of nearly pure calcite. The silicate-rich globules are elliptical to round in shape and are typically larger than the carbonate-rich globules ranging from 2 to several centimeters in diameter. They are characterized by clear reaction rims and contain several silicate minerals such as garnet, diopside and phlogopite. The silicate-rich globules, reported here for the first time, are suggested to be related to the origin of andradite within the kimberlitic rocks. Our results show that calcite in the carbonate-rich globules has a high XCa (>0.97) and is characterized by extremely high concentrations of the total rare earth elements (up to 1500 ppm), enrichment in Sr (8521-10,645 ppm) and LREE, and remarkable depletion in Nd, Ta, Zr, Hf and Ti. The calcite in the silicate-rich globules is geochemically similar to those in the carbonate-rich globules except the lower trace element contents. Garnet is dominantly andradite (And59.56-92.32Grs5.67-36.03Pyr0.36-4.61Spe0-0.33) and is enriched in light rare earth elements (LREEs) and relatively depleted in Rb, Ba, Th, Pb, Sr, Zr and Hf. Phlogopite in the silicate-rich globules has a high Mg# ranging from 0.93 to 0.97. The composition of the diopside is Wo45.82-51.39En39.81-49.09Fs0.88-0.95 with a high Mg# ranging from 0.88 to 0.95. Diopside in the silicate-rich globules has low total rare earth element (REE) contents (14-31 ppm) and shows middle REE- (Eu to Gd), slight light REE- and heavy REE-enrichment with elevated Zr, Hf and Sr contents and a negative Nb anomaly in the normalized diagram. The matrix of the kimberlitic rocks are silica undersaturated (27.92-29.31 wt.% SiO2) with low Al2O3 (4.51-5.15 wt.%) and high CaO (17.29-17.77 wt.%) contents. The

  11. The Effect of Confining Pressure on the Chemical Osmotic Property of Sedimentary Rock

    NASA Astrophysics Data System (ADS)

    Takeda, M.; Manaka, M.; Ito, K.

    2011-12-01

    In coastal, sedimentary formations, salinity gradients may induce chemical osmosis, leading to fluid pressure anomalies from hydrostatic pressures. For the precise characterization of the groundwater flow and mass transport systems with heterogeneous salinity distributions, the possibility of chemical osmosis needs to be identified. In order to test the ability of rock to generate pressure anomalies under salinity gradient, the authors developed a laboratory apparatus for measuring the chemically induced osmotic pressure within a rock sample under confining pressure. A series of experiments were performed on a disc-shaped siliceous mudstone, taken from Horonobe area in Hokkaido, under confining pressures ranging from 1 to 20 MPa. The salinity differences between the boundaries of sample are almost consistent in the experiments, and range from 0.110 to 0.118 M NaCl. The differential pressures between the boundaries of sample reached the quasi-steady state within 3 hours in each experiment, and their averaged values range from 9.1 to 26.4 kPa. The reflection coefficients approximated from the salinity and pressure differences using van't Hoff equation range from 0.020 to 0.049, and show the correlation with the confining pressure.

  12. Long-term migration of iodine in sedimentary rocks based on iodine speciation and 129I/127I ratio

    NASA Astrophysics Data System (ADS)

    Togo, Y.; Takahashi, Y.; Amano, Y.; Matsuzaki, H.; Suzuki, Y.; Muramatsu, Y.; Iwatsuki, T.

    2012-12-01

    [Introduction] 129I is one of the available indexes of long-term migration of groundwater solutes, because of its long half-life (15.7 million years) and low sorption characteristics. The Horonobe underground research center (Japan Atomic Energy Agency), at which are conducted research and development of fundamental techniques on geological disposal of high-level radioactive waste, is an appropriate site for natural analogue studies, because iodine concentration in groundwater is high in this area. To predict iodine behavior in natural systems, speciation of iodine is essential because of different mobility among each species. In this study, we determined iodine speciation and129I/127I isotope ratios of rock and groundwater samples to investigate long term migration of iodine. [Methods] All rock and groundwater samples were collected at Horonobe underground research center. The region is underlain mainly by Neogene to Quaternary marine sedimentary rocks, the Wakkanai Formation (Wk Fm, siliceous mudstones), and the overlying Koetoi Formation (Kt Fm, diatomaceous mudstones). Iodine species in rock samples were determined by iodine K-edge X-ray absorption near edge structure (SPring-8 BL01B1). Thin sections of rock samples were prepared, and iodine mapping were obtained by micro-XRF analysis (SPring-8 BL37XU). Iodine species (IO3-, I-, and organic I) in groundwater were separately detected by high performance liquid chromatography connected to ICP-MS. The 129I/127I ratios in groundwater and rock samples were measured by accelerator mass spectrometry (MALT, Univ. of Tokyo). Iodine in rock samples were separated by pyrohydrolysis and water extraction. [Results and discussion] Concentration of iodine in groundwater varied widely and was much higher than that of seawater showing a high correlation with that of chlorine (R2 = 0.90). Species of iodine in groundwater was mainly I-. Iodine in rock samples decreased near the boundary between Wk and Kt Fms. Iodine K-edge XANES

  13. Petrogenesis of mafic and associated silicic end-member magmas for calc-alkaline mixed rocks in the Shirataka volcano, NE Japan

    NASA Astrophysics Data System (ADS)

    Hirotani, Shiho; Ban, Masao; Nakagawa, Mitsuhiro

    2009-06-01

    Eruptive products of the Shirataka volcano (0.9-0.7 Ma) in NE Japan are calc-alkaline andesite-dacite, and are divisible into six petrologic groups (G1-G6). Shirataka rocks possess mafic inclusions—basalt-basaltic andesite, except for G3 and G4. All rocks show mixing and mingling of the mafic and silicic end-members, with trends defined by hosts and inclusions divided into high-Cr and low-Cr types; both types coexist in G1, G2, and G5. Estimated mafic end-members are high-Cr (1120-1170°C, 48-51% SiO2, olv ± cpx ± plg) and low-Cr type magmas (49-52% SiO2, cpx ± plg) except for the Sr isotopic composition. In contrast, the silicic end-members of both types have similar petrologic features (790-840°C, 64-70% SiO2, hbl ± qtz ± px + plg). High-Cr type mafic and corresponding silicic end-members have lower 87Sr/86Sr ratios than the low-Cr ones in each group. The trace element model calculations suggest that the low-Cr type mafic end-member magma is produced through ca. 20% fractional crystallization (olv ± cpx ± plg) from the high-Cr type one with assimilation of granitoids ( r = 0.02-0.05). The silicic magmas are producible through <30% partial remelting of previously emplaced basaltic magma with assimilation of crustal components. The compositional difference between the low-K and medium-K basalts in the Shirataka volcano is mainly attributed to the different degrees of the effect of subduction derived fluid by dehydration of phlogopite.

  14. Origin of silicic volcanic rocks in Central Costa Rica: a study of a chemically variable ash-flow sheet in the Tiribí Tuff

    NASA Astrophysics Data System (ADS)

    Hannah, Rachel; Vogel, Thomas; Patino, Lina; Alvarado, Guillermo; Pérez, Wendy; Smith, Diane

    2002-01-01

    Chemical heterogeneities of pumice clasts in an ash-flow sheet can be used to determine processes that occur in the magma chamber because they represent samples of magma that were erupted at the same time. The dominant ash-flow sheet in the Tiribí Tuff contains pumice clasts that range in composition from 55.1 to 69.2 wt% SiO2. It covers about 820 km2 and has a volume of about 25 km3 dense-rock equivalent (DRE). Based on pumice clast compositions, the sheet can be divided into three distinct chemical groupings: a low-silica group (55.1-65.6 wt% SiO2), a silicic group (66.2-69.2 wt% SiO2), and a mingled group (58.6-67.7 wt% SiO2; all compositions calculated 100% anhydrous). Major and trace element modeling indicates that the low-silica magma represents a mantle melt that has undergone fractional crystallization, creating a continuous range of silica content from 55.1-65.6 wt% SiO2. Eu/Eu*, MREE, and HREE differences between the two groups are not consistent with crystal fractionation of the low-silica magma to produce the silicic magma. The low-silica group and the silicic group represent two distinct magmas, which did not evolve in the same magma chamber. We suggest that the silicic melts resulted from partial melting of relatively hot, evolved calc-alkaline rocks that were previously emplaced and ponded at the base of an over-thickened basaltic crust. The mingled group represents mingling of the two magmas shortly before eruption. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00445-001-0188-8.

  15. Selective Precipitation of Thorium lodate from a Tartaric Acid-Hydrogen Peroxide Medium Application to Rapid Spectrophotometric Determination of Thorium in Silicate Rocks and in Ores

    USGS Publications Warehouse

    Grimaldi, F.S.

    1957-01-01

    This paper presents a selective iodate separation of thorium from nitric acid medium containing d-tartaric acid and hydrogen peroxide. The catalytic decomposition of hydrogen peroxide is prevented by the use of 8quinolinol. A few micrograms of thorium are separated sufficiently clean from 30 mg. of such oxides as cerium, zirconium, titanium, niobium, tantalum, scandium, or iron with one iodate precipitation to allow an accurate determination of thorium with the thoronmesotartaric acid spectrophotometric method. The method is successful for the determination of 0.001% or more of thorium dioxide in silicate rocks and for 0.01% or more in black sand, monazite, thorite, thorianite, eschynite, euxenite, and zircon.

  16. Application of epithermal neutron activation in multielement analysis of silicate rocks employing both coaxial Ge(Li) and low energy photon detector systems

    USGS Publications Warehouse

    Baedecker, P.A.; Rowe, J.J.; Steinnes, E.

    1977-01-01

    The instrumental activation analysis of silicate rocks using epithermal neutrons has been studied using both high resolution coaxial Ge(Li) detectors and low energy photon detectors, and applied to the determination of 23 elements in eight new U.S.G.S. standard rocks. The analytical use X-ray peaks associated with electron capture or internal conversion processes has been evaluated. Of 28 elements which can be considered to be determinable by instrumental means, the epithermal activation approach is capable of giving improved sensitivity and precision in 16 cases, over the normal INAA procedure. In eleven cases the use of the low energy photon detector is thought to show advantages over convertional coaxial Ge(Li) spectroscopy. ?? 1977 Akade??miai Kiado??.

  17. Immiscibility between calciocarbonatitic and silicate melts and related wall rock reactions in the upper mantle: a natural case study from Romanian mantle xenoliths

    NASA Astrophysics Data System (ADS)

    Chalot-Prat, Françoise; Arnold, Michel

    1999-04-01

    This paper presents the textural, mineralogical and chemical study of veinlets cross-cutting peridotite xenoliths from the lithospheric mantle and brought to the surface by alkaline basalts (Persani Mountains, Romania). The veinlets utilized pre-existing zones of weakness in the host rocks or display a random distribution, lining grain boundaries or cross-cutting any mineral, and always forming an interconnected network. They are filled with carbonate patches included in a silicate matrix. Both products are holocrystalline. Carbonate products have alkali-poor calciocarbonatitic to sövitic compositions, while the silicate matrix composition ranges from monzodioritic to monzonitic and alkali feldspar syenitic, depending on the host-sample, i.e., within a rather alkaline silica-saturated series. The mineral phases present in the silicate matrix (F-apatite, armalcolite, chromite, diopside-enstatite series, plagioclase-sanidine series) are usually present in the carbonate zones, where forsterite is also found. Some minerals cross-cut the interface between both types of zones. Only the matrix is different, feldspathic (oligoclase to sanidine) in the former and pure calcite in the latter. Thus, mineralogical and textural relationships between both products are consistent with an origin with equilibrium liquid immiscibility. Mantle minerals cross-cut by veinlets are sometimes resorbed at grain boundaries, and at the contact of the most alkaline silicate and carbonate melts, subhedral diopside/augite formed at the expense of mantle enstatite or olivine. In terms of mineral chemistry, the compositional variations recorded by vein minerals vary along a continuous trend. They generally superpose to those observed from lherzolites to harzburgites, and exhibit the same range of composition as that observed between rims and cores of mantle minerals cross-cut by veinlets. In detail, the Ca-rich pyroxenes of veinlets are Al-poor and Mg-rich; cpx in the carbonate zones are slightly

  18. The separation of platinum, palladium and gold from silicate rocks by the anion exchange separation of chloro complexes after a sodium peroxide fusion: an investigation of low recoveries.

    PubMed

    Enzweiler, J; Potts, P J

    1995-10-01

    A series of experiments was undertaken to measure the recovery efficiency of platinum, palladium and gold from silicate rocks using a sodium peroxide fusion followed by anion exchange separation of the analytes as chloro complexes. Results obtained by graphite furnace atomic absorption spectrometric analysis of standard solutions prepared in dilute HCl or HCl-acidified sodium peroxide solution showed that recoveries were near quantitative. However, when standard solutions were added to an alkaline sodium peroxide solution, which was then acidified, low results were obtained for platinum and gold (46% and 76% respectively). Low and variable results were also obtained when standard solutions were added to a peridotite sample that had been dissolved by the state procedure, and in the analysis of the South African Bureau of Standards certified reference material, SARM 7. Various experiments were undertaken to investigate these low recoveries, but the reason proposed here is the formation of hydroxychloro compounds in alkaline solution which are not, on acidification with HCl, converted quantitatively to the chloro complex necessary for quantitative anion exchange separation. It is concluded that a sodium peroxide fusion followed by an anion-exchange separation does not appear to form the basis of a successful technique for the determination of platinum, palladium and gold in silicate rocks.

  19. Reaction textures in scapolite wollastonite grossular calc-silicate rock from the Kerala Khondalite Belt, Southern India: evidence for high-temperature metamorphism and initial cooling

    NASA Astrophysics Data System (ADS)

    Satish-Kumar, M.; Harley, Simon L.

    1998-11-01

    Scapolite-wollastonite-grossular bearing calc-silicate rocks from the Vellanad area in the Kerala Khondalite Belt (KKB) of Southern India preserve a number of reaction textures which help to deduce their P- T-fluid history. Textures include calcite+plagioclase±quartz symplectites after scapolite, grossular+quartz coronas between wollastonite and plagioclase, grossular coronas between wollastonite and plagioclase+calcite that replace former scapolite, and grossular blebs replacing anorthite+calcite+quartz pseudomorphs of scapolite. Garnet coronas are also observed between clinopyroxene and wollastonite or scapolite or plagioclase. The reactions, apart from those involving clinopyroxene, can be modelled in the simple CaO-Al 2O 3-SiO 2-CO 2 system and interpreted using partial reaction grids constructed for the activities of end-members in the analysed phases. The reaction topologies produced are good approximations for the peak as well as retrograde mineral assemblages and reaction textures. For the compositions of the phases present in this study, the medium pressure calc-silicate assemblages are defined by the stable pseudo-invariant points [Qtz], [Mei] and [Grs]. The textural features interpreted using these activity-corrected grids indicate a phase of isobaric cooling from about 835°C to 750°C at 6 kbar in the Vellanad area. This is inconsistent with earlier studies on other lithologies from the KKB, most of which imply a post-peak P- T path involving near-isothermal decompression. However, as the temperatures obtained for the KKB from the calc-silicates are higher than those previously deduced from metapelites and garnet-orthopyroxene assemblages, the phase of near-isobaric cooling reported here is inferred to have proceeded prior to the onset of the decompression documented from studies of other rock types.

  20. Ar-Ar ages, Sr-Nd isotope geochemistry, and implications for the origin of the silicate rocks of the Jacupiranga ultramafic-alkaline complex (Brazil)

    NASA Astrophysics Data System (ADS)

    Chmyz, Luanna; Arnaud, Nicolas; Biondi, João Carlos; Azzone, Rogério Guitarrari; Bosch, Delphine; Ruberti, Excelso

    2017-08-01

    The Jacupiranga Complex is one of several Meso-Cenozoic alkaline intrusive complexes along the margins of the intracratonic Paraná Basin in southern Brazil. The complex encompasses a wide range of rock-types, including dunites, wehrlites, clinopyroxenites, melteigites-ijolites, feldspar-bearing rocks (diorites, syenites, and monzonites), lamprophyres and apatite-rich carbonatites. While carbonatites have been extensively investigated over the last decades, little attention has been paid to the silicate rocks. This study presents new geochonological and geochemical data on the Jacupiranga Complex, with particular emphasis on the silicate lithotypes. 40Ar/39Ar ages for different lithotypes range from 133.7 ± 0.5 Ma to 131.4 ± 0.5 Ma, while monzonite zircon analyzed by SHRIMP yields a U-Pb concordia age of 134.9 ± 1.3 Ma. These ages indicate a narrow time frame for the Jacupiranga Complex emplacement, contemporaneous with the Paraná Magmatic Province. Most of the Jacupiranga rocks are SiO2-undersaturated, except for a quartz-normative monzonite. Based on geochemical compositions, the Jacupiranga silicate lithotypes may be separated into two magma-evolution trends: (1) a strongly silica-undersaturated series, comprising part of the clinopyroxenites and the ijolitic rocks, probably related to nephelinite melts and (2) a mildly silica-undersaturated series, related to basanite parental magmas and comprising the feldspar-bearing rocks, phonolites, lamprophyres, and part of the clinopyroxenites. Dunites and wehrlites are characterized by olivine compositionally restricted to the Fo83-84 interval and concentrations of CaO (0.13-0.54 wt%) and NiO (0.19-0.33 wt%) consistent with derivation by fractional crystallization, although it is not clear whether these rocks belong to the nephelinite or basanite series. Lamprophyre dikes within the complex are considered as good representatives of the basanite parental magma. Compositions of calculated melts in equilibrium with

  1. Acid-fog deposition at Kilauea volcano: A possible mechanism for the formation of siliceous-sulfate rock coatings on Mars

    NASA Astrophysics Data System (ADS)

    Schiffman, Peter; Zierenberg, Robert; Marks, Naomi; Bishop, Janice L.; Darby Dyar, M.

    2006-11-01

    On the summit of Kilauea volcano, sulfur dioxide, which is continuously emitted from Halemaumau crater and rapidly sequestered into sulfuric-acid rich aerosol entrained in the prevailing trade winds, is subsequently precipitated as acid fog immediately downwind from Kilauea caldera in the Kau Desert. The characteristic pH of surface tephra deposits is <4.0 in Sand Wash, a region of nearly continuous, acidic aerosol fallout immediately southwest of the caldera. Vertical exposures of unconsolidated tephras of the Keanakakoi Ash found within fissures and small, dry gullies are coated with thin rock coatings of amorphous silica and jarosite. These rock coatings are formed via an evaporative mechanism whereby acidic pore fluids, circulating in the upper few meters within the highly porous tephra, are wicked toward the walls of the gullies. Geochemical modeling of the rock coating formation process implies that the sulfate formation via evaporation occurs subsequent to minimal interaction of acidic pore fluids with the basaltic tephra. This also suggests that the cycle from acid-fog fallout to precipitation of the siliceous-sulfate rock coatings must occur quite rapidly. Acid-fog deposition of sulfate and silica at Kilauea may provide one mechanism for the origin of jarosite-bearing outcrops on Mars.

  2. Insights into Oceanic Crust Accretion from a Comparison of Rock Magnetic and Silicate Fabrics from Lower Crustal Gabbros from Hess Deep Rift

    NASA Astrophysics Data System (ADS)

    Horst, A. J.; Morris, A.; Friedman, S. A.; Cheadle, M. J.

    2014-12-01

    between silicate and magnetic fabric data suggests that AMS is a good proxy for bulk silicate fabrics in these samples from Hess Deep. By integrating AMS and EBSD, both sensitive indicators of magnetic and silicate fabrics in gabbroic rocks, we seek a better understanding of the formation of gabbro in oceanic crust.

  3. Anoxic and Oxic Oxidation of Rocks Containing Fe(II)Mg-Silicates and Fe(II)-Monosulfides as Source of Fe(III)-Minerals and Hydrogen. Geobiotropy.

    NASA Astrophysics Data System (ADS)

    Bassez, Marie-Paule

    2017-03-01

    In this article, anoxic and oxic hydrolyses of rocks containing Fe (II) Mg-silicates and Fe (II)-monosulfides are analyzed at 25 °C and 250-350 °C. A table of the products is drawn. It is shown that magnetite and hydrogen can be produced during low-temperature (25 °C) anoxic hydrolysis/oxidation of ferrous silicates and during high-temperature (250 °C) anoxic hydrolysis/oxidation of ferrous monosulfides. The high-T (350 °C) anoxic hydrolysis of ferrous silicates leads mainly to ferric oxides/hydroxides such as the hydroxide ferric trihydroxide, the oxide hydroxide goethite/lepidocrocite and the oxide hematite, and to Fe(III)-phyllosilicates. Magnetite is not a primary product. While the low-T (25 °C) anoxic hydrolysis of ferrous monosulfides leads to pyrite. Thermodynamic functions are calculated for elementary reactions of hydrolysis and carbonation of olivine and pyroxene and E-pH diagrams are analyzed. It is shown that the hydrolysis of the iron endmember is endothermic and can proceed within the exothermic hydrolysis of the magnesium endmember and also within the exothermic reactions of carbonations. The distinction between three products of the iron hydrolysis, magnetite, goethite and hematite is determined with E-pH diagrams. The hydrolysis/oxidation of the sulfides mackinawite/troilite/pyrrhotite is highly endothermic but can proceed within the heat produced by the exothermic hydrolyses and carbonations of ferromagnesian silicates and also by other sources such as magma, hydrothermal sources, impacts. These theoretical results are confirmed by the products observed in several related laboratory experiments. The case of radiolyzed water is studied. It is shown that magnetite and ferric oxides/hydroxides such as ferric trihydroxide, goethite/lepidocrocite and hematite are formed in oxic hydrolysis of ferromagnesian silicates at 25 °C and 350 °C. Oxic oxidation of ferrous monosulfides at 25 °C leads mainly to pyrite and ferric oxides/hydroxides such as

  4. Anoxic and Oxic Oxidation of Rocks Containing Fe(II)Mg-Silicates and Fe(II)-Monosulfides as Source of Fe(III)-Minerals and Hydrogen. Geobiotropy.

    PubMed

    Bassez, Marie-Paule

    2017-03-31

    In this article, anoxic and oxic hydrolyses of rocks containing Fe (II) Mg-silicates and Fe (II)-monosulfides are analyzed at 25 °C and 250-350 °C. A table of the products is drawn. It is shown that magnetite and hydrogen can be produced during low-temperature (25 °C) anoxic hydrolysis/oxidation of ferrous silicates and during high-temperature (250 °C) anoxic hydrolysis/oxidation of ferrous monosulfides. The high-T (350 °C) anoxic hydrolysis of ferrous silicates leads mainly to ferric oxides/hydroxides such as the hydroxide ferric trihydroxide, the oxide hydroxide goethite/lepidocrocite and the oxide hematite, and to Fe(III)-phyllosilicates. Magnetite is not a primary product. While the low-T (25 °C) anoxic hydrolysis of ferrous monosulfides leads to pyrite. Thermodynamic functions are calculated for elementary reactions of hydrolysis and carbonation of olivine and pyroxene and E-pH diagrams are analyzed. It is shown that the hydrolysis of the iron endmember is endothermic and can proceed within the exothermic hydrolysis of the magnesium endmember and also within the exothermic reactions of carbonations. The distinction between three products of the iron hydrolysis, magnetite, goethite and hematite is determined with E-pH diagrams. The hydrolysis/oxidation of the sulfides mackinawite/troilite/pyrrhotite is highly endothermic but can proceed within the heat produced by the exothermic hydrolyses and carbonations of ferromagnesian silicates and also by other sources such as magma, hydrothermal sources, impacts. These theoretical results are confirmed by the products observed in several related laboratory experiments. The case of radiolyzed water is studied. It is shown that magnetite and ferric oxides/hydroxides such as ferric trihydroxide, goethite/lepidocrocite and hematite are formed in oxic hydrolysis of ferromagnesian silicates at 25 °C and 350 °C. Oxic oxidation of ferrous monosulfides at 25 °C leads mainly to pyrite and ferric oxides

  5. Drilling effect on subsurface microbial community structure in groundwater from the -250 m gallery at the Horonobe Underground Research Laboratory, Japan

    NASA Astrophysics Data System (ADS)

    Ise, K.; Amano, Y.; Sasaki, Y.; Yoshikawa, H.

    2014-12-01

    The deep geological disposal system is regarded as the most secure and practical disposal method of high-level radioactive waste in the world. In this disposal system, preservation of reducing condition is one of the key requirements, because most of radionuclides have low solubilities in such condition. However, the host rocks near the shafts and galleries would be affected by oxidization during the construction and operation period of a repository (for about 50 years). Therefore, the recovery of reducing condition after closing the repository should be verified. During the recovery processes, it is considered that microbial activities play important roles, but the mechanisms are poorly understood. In this study, we monitored the changes in microbial communities by molecular method to evaluate microbial response toward the oxygen stress. The groundwater samples were collected from a borehole of 250 m depth at the Horonobe Underground Research Laboratory, for two years immediately after drilling of a borehole without any contamination as much as possible. Immediately after drilling of the borehole, the phylotype related to Arcobacter spp. was dominated about 65 % of the total clone library. Arcobacter spp. is known as sulfide oxidizer and which can growth chemoautotrophically. Half a year later, the phylotype related to Azoarcus spp. and Pseudomonas spp. known as nitrate reducing bacteria increased, instead of the phylotype related to Arcobacter spp. One year later, in addition to nitrate reducing bacteria, phylotype related to Dethiobacterspp. known as thiosulfate reducing bacteria was dominantly detected. Two years later, most of detected clones were related to uncultured species such as candidate division WS6 and JS1 which are detected frequently in deep-sea sediments. Our results indicate that these redox sequential reactions could contribute to the recovery and maintenance of reducing conditions and provide a conceptual model for evaluating the capacity to

  6. Rocks.

    ERIC Educational Resources Information Center

    Lee, Alice

    This science unit is designed for limited- and non-English speaking students in a Chinese bilingual education program. The unit covers rock material, classification, characteristics of types of rocks, and rock cycles. It is written in Chinese and simple English. At the end of the unit there is a list of main terms in both English and Chinese, and…

  7. A legacy of Hadean silicate differentiation inferred from Hf isotopes in Eoarchean rocks of the Nuvvuagittuq supracrustal belt (Québec, Canada)

    NASA Astrophysics Data System (ADS)

    Guitreau, Martin; Blichert-Toft, Janne; Mojzsis, Stephen J.; Roth, Antoine S. G.; Bourdon, Bernard

    2013-01-01

    New Lu-Hf isotopic data for mafic and felsic rocks from the Nuvvuagittuq supracrustal belt (NSB) in northern Québec (Canada) yield an Eoarchean age of 3864±70 Ma consistent with both zircon U-Pb and whole-rock 147Sm-143Nd chronology, but in disagreement with ca. 4400 Ma ages inferred from the 146Sm-142Nd chronometer (O'Neil et al., 2008, 2012). The Lu-Hf result is interpreted as the mean emplacement age of the different autochthonous units of the NSB. An observed alignment of the data along a Lu-Hf "scatterchron" precludes a Hadean age for the NSB because its isotopic characteristics appear to be controlled by long-term radiogenic ingrowth. Emplacement of the NSB in the Hadean (e.g., 4362-54+35 Ma if the decay constant of 146Sm of Kinoshita et al. (2012) is used with the O'Neil et al., 2008 data) should instead have caused age differences of hundreds of millions of years to manifest as strong deviations from the Lu-Hf scatterchron. Combined Lu-Hf and Sm-Nd data on the same NSB amphibolite samples (Ca-poor cummingtonite- and hornblende-bearing) define a mixing hyperbola at ca. 3800 Ma with end-member compositions representative of the compositional groups identified for these lithologies (O'Neil et al., 2011). Anomalously low 142Nd/144Nd values relative to Bulk Silicate Earth are endemic to a group of rocks in the NSB termed "low-TiO2" amphibolites; this is attributable to an ancient multi-stage history of their mantle source. Modeling shows that the 142Nd/144Nd deficits could have developed in response to a re-fertilization episode within a previously fractionated mantle domain at 4510 Ma.

  8. Green and Fast Laser Fusion Technique for Bulk Silicate Rock Analysis by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Zhang, Chenxi; Hu, Zhaochu; Zhang, Wen; Liu, Yongsheng; Zong, Keqing; Li, Ming; Chen, Haihong; Hu, Shenghong

    2016-10-18

    Sample preparation of whole-rock powders is the major limitation for their accurate and precise elemental analysis by laser ablation inductively-coupled plasma mass spectrometry (ICPMS). In this study, a green, efficient, and simplified fusion technique using a high energy infrared laser was developed for major and trace elemental analysis. Fusion takes only tens of milliseconds for each sample. Compared to the pressed pellet sample preparation, the analytical precision of the developed laser fusion technique is higher by an order of magnitude for most elements in granodiorite GSP-2. Analytical results obtained for five USGS reference materials (ranging from mafic to intermediate to felsic) using the laser fusion technique generally agree with recommended values with discrepancies of less than 10% for most elements. However, high losses (20-70%) of highly volatile elements (Zn and Pb) and the transition metal Cu are observed. The achieved precision is within 5% for major elements and within 15% for most trace elements. Direct laser fusion of rock powders is a green and notably simple method to obtain homogeneous samples, which will significantly accelerate the application of laser ablation ICPMS for whole-rock sample analysis.

  9. Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater.

    PubMed

    Morris, Richard V; Vaniman, David T; Blake, David F; Gellert, Ralf; Chipera, Steve J; Rampe, Elizabeth B; Ming, Douglas W; Morrison, Shaunna M; Downs, Robert T; Treiman, Allan H; Yen, Albert S; Grotzinger, John P; Achilles, Cherie N; Bristow, Thomas F; Crisp, Joy A; Des Marais, David J; Farmer, Jack D; Fendrich, Kim V; Frydenvang, Jens; Graff, Trevor G; Morookian, John-Michael; Stolper, Edward M; Schwenzer, Susanne P

    2016-06-28

    Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity The tridymitic mudstone has ∼40 wt.% crystalline and ∼60 wt.% X-ray amorphous material and a bulk composition with ∼74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (∼17 wt.% of bulk sample), tridymite (∼14 wt.%), sanidine (∼3 wt.%), cation-deficient magnetite (∼3 wt.%), cristobalite (∼2 wt.%), and anhydrite (∼1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (∼39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides-perchlorates-chlorates), and has minor TiO2 and Fe2O3T oxides (∼5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a "Lake Gale" catchment environment can account for Buckskin's tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill.

  10. Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

    PubMed Central

    Morris, Richard V.; Vaniman, David T.; Blake, David F.; Gellert, Ralf; Chipera, Steve J.; Rampe, Elizabeth B.; Ming, Douglas W.; Morrison, Shaunna M.; Downs, Robert T.; Treiman, Allan H.; Yen, Albert S.; Grotzinger, John P.; Achilles, Cherie N.; Bristow, Thomas F.; Crisp, Joy A.; Des Marais, David J.; Farmer, Jack D.; Fendrich, Kim V.; Graff, Trevor G.; Morookian, John-Michael; Stolper, Edward M.; Schwenzer, Susanne P.

    2016-01-01

    Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ∼40 wt.% crystalline and ∼60 wt.% X-ray amorphous material and a bulk composition with ∼74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (∼17 wt.% of bulk sample), tridymite (∼14 wt.%), sanidine (∼3 wt.%), cation-deficient magnetite (∼3 wt.%), cristobalite (∼2 wt.%), and anhydrite (∼1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (∼39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides−perchlorates−chlorates), and has minor TiO2 and Fe2O3T oxides (∼5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a “Lake Gale” catchment environment can account for Buckskin’s tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill. PMID:27298370

  11. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 2: application to Taupo Volcanic Zone rhyolites

    NASA Astrophysics Data System (ADS)

    Bégué, Florence; Gualda, Guilherme A. R.; Ghiorso, Mark S.; Pamukcu, Ayla S.; Kennedy, Ben M.; Gravley, Darren M.; Deering, Chad D.; Chambefort, Isabelle

    2014-11-01

    Constraining the pressure of crystallisation of large silicic magma bodies gives important insight into the depth and vertical extent of magmatic plumbing systems; however, it is notably difficult to constrain pressure at the level of detail necessary to understand shallow magmatic systems. In this study, we use the recently developed rhyolite-MELTS geobarometer to constrain the crystallisation pressures of rhyolites from the Taupo Volcanic Zone (TVZ). As sanidine is absent from the studied deposits, we calculate the pressures at which quartz and feldspar are found to be in equilibrium with melt now preserved as glass (the quartz +1 feldspar constraint of Gualda and Ghiorso, Contrib Mineral Petrol 168:1033. doi:10.1007/s00410-014-1033-3. 2014). We use glass compositions (matrix glass and melt inclusions) from seven eruptive deposits dated between ~320 and 0.7 ka from four distinct calderas in the central TVZ, and we discuss advantages and limitations of the rhyolite-MELTS geobarometer in comparison with other geobarometers applied to the same eruptive deposits. Overall, there is good agreement with other pressure estimates from the literature (amphibole geobarometry and H2O-CO2 solubility models). One of the main advantages of this new geobarometer is that it can be applied to both matrix glass and melt inclusions—regardless of volatile saturation. The examples presented also emphasise the utility of this method to filter out spurious glass compositions. Pressure estimates obtained with the new rhyolite-MELTS geobarometer range between ~250 to ~50 MPa, with a large majority at ~100 MPa. These results confirm that the TVZ hosts some of the shallowest rhyolitic magma bodies on the planet, resulting from the extensional tectonic regime and thinning of the crust. Distinct populations with different equilibration pressures are also recognised, which is consistent with the idea that multiple batches of eruptible magma can be present in the crust at the same time and

  12. Silicic volcanism on Mars evidenced by tridymite in high-SiO2 sedimentary rock at Gale crater

    NASA Astrophysics Data System (ADS)

    Morris, Richard V.; Vaniman, David T.; Blake, David F.; Gellert, Ralf; Chipera, Steve J.; Rampe, Elizabeth B.; Ming, Douglas W.; Morrison, Shaunna M.; Downs, Robert T.; Treiman, Allan H.; Yen, Albert S.; Grotzinger, John P.; Achilles, Cherie N.; Bristow, Thomas F.; Crisp, Joy A.; Des Marais, David J.; Farmer, Jack D.; Fendrich, Kim V.; Frydenvang, Jens; Graff, Trevor G.; Morookian, John-Michael; Stolper, Edward M.; Schwenzer, Susanne P.

    2016-06-01

    Tridymite, a low-pressure, high-temperature (>870 °C) SiO2 polymorph, was detected in a drill sample of laminated mudstone (Buckskin) at Marias Pass in Gale crater, Mars, by the Chemistry and Mineralogy X-ray diffraction instrument onboard the Mars Science Laboratory rover Curiosity. The tridymitic mudstone has ˜40 wt.% crystalline and ˜60 wt.% X-ray amorphous material and a bulk composition with ˜74 wt.% SiO2 (Alpha Particle X-Ray Spectrometer analysis). Plagioclase (˜17 wt.% of bulk sample), tridymite (˜14 wt.%), sanidine (˜3 wt.%), cation-deficient magnetite (˜3 wt.%), cristobalite (˜2 wt.%), and anhydrite (˜1 wt.%) are the mudstone crystalline minerals. Amorphous material is silica-rich (˜39 wt.% opal-A and/or high-SiO2 glass and opal-CT), volatile-bearing (16 wt.% mixed cation sulfates, phosphates, and chlorides-perchlorates-chlorates), and has minor TiO2 and Fe2O3T oxides (˜5 wt.%). Rietveld refinement yielded a monoclinic structural model for a well-crystalline tridymite, consistent with high formation temperatures. Terrestrial tridymite is commonly associated with silicic volcanism, and detritus from such volcanism in a “Lake Gale” catchment environment can account for Buckskin's tridymite, cristobalite, feldspar, and any residual high-SiO2 glass. These cogenetic detrital phases are possibly sourced from the Gale crater wall/rim/central peak. Opaline silica could form during diagenesis from high-SiO2 glass, as amorphous precipitated silica, or as a residue of acidic leaching in the sediment source region or at Marias Pass. The amorphous mixed-cation salts and oxides and possibly the crystalline magnetite (otherwise detrital) are primary precipitates and/or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions, temperatures, and acidities. Anhydrite is post lithification fracture/vein fill.

  13. Zircon U-Th and U-Pb Ages From Quaternary Silicic Volcanic and Plutonic Rocks, and Their Bearing on Granitoid Batholiths

    NASA Astrophysics Data System (ADS)

    Bacon, C. R.

    2007-12-01

    In the ten years since publication of M. Reid et al.'s seminal paper on zircon ages from rhyolites (EPSL 150:2-39, 1997) >20 papers have appeared on SIMS 238U-230Th and 238U-206Pb geochronology of zircon from silicic volcanic rocks, plutonic xenoliths, and young intrusions. In some cases, as well as for U-Pb studies of Tertiary granitoids, plutonic samples are interpreted in the context of related volcanism. These geochronologic data have advanced conceptual models of silicic magma genesis and pluton construction. Of fundamental importance are discoveries that zircons in volcanic rocks typically pre-date eruption by 10's to 100's of kyr and that multiple zircon populations are common; these crystals are "antecrysts" recycled from intrusive rocks or crystal mush of the system that vented. Resolving such age differences is possible with U-Th at <300 ka but is challenging with U-Pb, where SIMS precision limits resolution of differences on the order of 100 kyr for Pleistocene-Miocene zircons. Cathodoluminescence (CL) imaging of polished crystals guides beam placement but leads to sampling bias that favors high-U regions. Thus, although model-age histograms and relative probability plots identify zircon age populations, they are unlikely to accurately define relative abundances of age groups. Microbeam analysis collects data for the entire volume sampled but only SIMS depth-profiling into crystal faces can spatially resolve fine zones. ID-TIMS analysis of CL-imaged zircon fragments can improve U-Pb precision. SIMS complements geochronology with trace element fingerprints of zircon growth environments and enables Ti-in-zircon thermometry. Literature examples illustrate recent findings: (1) rhyodacite lava at Crater Lake contains zircons derived from late Pleistocene granodiorite represented by blocks ejected in the caldera-forming eruption; (2) zircons in Mount St. Helens dacites grew at sub-eruption temperatures and pre-date eruptions by up to 250 kyr; (3) Miocene

  14. A legacy of Hadean silicate differentiation inferred from Hf isotopes in Eoarchean rocks of the Nuvvuagittuq supracrustal belt (Québec, Canada)

    NASA Astrophysics Data System (ADS)

    Guitreau, Martin; Blichert-Toft, Janne; Mojzsis, Stephen J.; Roth, Antoine S. G.; Bourdon, Bernard

    2013-04-01

    New Lu-Hf isotopic data for mafic and felsic rocks from the Nuvvuagittuq supracrustal belt (NSB) in northern Québec (Canada) yield an Eoarchean age of 3864 ± 70 Ma consistent with both zircon U-Pb and whole-rock 147Sm-143Nd chronology, but in disagreement with ca. 4400 Ma ages inferred from the 146Sm-142Nd chronometer (O'Neil et al., 2008). The Lu-Hf result is interpreted as the mean emplacement age of the different autochthonous units of the NSB. An observed alignment of the data along a Lu-Hf "scatterchron" precludes a Hadean age for the NSB because its isotopic characteristics appear to be controlled by long-term radiogenic ingrowth. Emplacement of the NSB in the Hadean (e.g., 4362 Ma; re-calculated in Kinoshita et al., 2012) should have caused age differences of hundreds of millions of years to manifest as strong deviations from the Lu-Hf scatterchron. Combined Lu-Hf and Sm-Nd data on the same NSB amphibolite samples (Ca-poor cummingtonite- and hornblende-bearing) define a mixing hyperbola at ca. 3800 Ma with end-member compositions representative of the compositional groups identified for these lithologies (O'Neil et al., 2011). Anomalously low 142Nd/144Nd values relative to Bulk Silicate Earth are endemic to "low-TiO2" amphibolites; this is attributable to an ancient multi-stage history of their mantle source as indicated by rare-earth element patterns. Modeling shows that the 142Nd/144Nd deficits could have developed in response to a re-fertilization episode within a mantle domain depleted by primordial crust extraction at 4510 Ma.

  15. Scheelite and coexisting F-rich zoned garnet, vesuvianite, fluorite, and apatite in calc-silicate rocks from the Mogok metamorphic belt, Myanmar: Implications for metasomatism in marble and the role of halogens in W mobilization and mineralization

    NASA Astrophysics Data System (ADS)

    Guo, Shun; Chen, Yi; Liu, Chuan-Zhou; Wang, Jian-Gang; Su, Bin; Gao, Yi-Jie; Wu, Fu-Yuan; Sein, Kyaing; Yang, Yue-Heng; Mao, Qian

    2016-03-01

    Scheelite, which is an important ore of tungsten and colored gemstone, is well developed in the calc-silicate rocks from the Mogok metamorphic belt (MMB), Myanmar. In this study, the textural, mineralogical, and compositional characteristics of scheelite and its associated minerals were systematically investigated to constrain the petrogenesis of scheelite-bearing calc-silicate rocks and the tungsten transfer and mineralization mechanism in a hydrothermal-metasomatic system. The petrological evidence, bulk and mineral geochemical signatures, and mass-transfer calculations indicate that the calc-silicate rocks formed by local metasomatism of marble via the introduction of an externally derived Si-Al-Fe-W-F-bearing, H2O-rich fluid phase. The distinct compositional zonations [F, Fe, Ca, and heavy rare earth elements (HREEs)] of garnet in the calc-silicate rocks record a two-stage metasomatic process and significant compositional variation in the associated fluid. The late-stage metasomatic fluid that led to the formation of the F-rich garnet rims, scheelite, and most of the calc-silicate minerals has noticeably higher fluorine activity (aF-), oxygen fugacity (fo2), and HREE content than the early-stage metasomatic fluid responsible for the garnet cores. The MMB scheelite exhibits typical "skarn-type" compositional characteristics with a high LaN/YbN ratio (100-180), a negative Eu anomaly (δEu = 0.3-0.5), and a high Mo content (1100-1330 ppm). These geochemical signatures are primarily controlled by the protolith, metasomatic fluid, redox conditions, and coexisting mineral phases. The enrichment of rare earth elements (REEs) and high field strength elements (HFSEs) in the MMB scheelite was dominated by two substitution reactions: Ca2+ + W6+ = REE3+ + HFSE5+ and 3Ca2+ = 2REE3+ + □Ca (where □Ca is a Ca-site vacancy). Considerable amounts of F and OH in the metasomatic fluid substituted for O in the garnet via the substitute reaction 4(F, OH)- = 4O2- + Si4+, leading

  16. Early differentiation of the silicate Earth : new constraints from isotopic investigation of rocks from the lunar highlands

    NASA Astrophysics Data System (ADS)

    Boyet, M.; Carlson, R.; Borg, L.; Connelly, J.; Horan, M.

    2012-04-01

    The isotopic similarity in O, Mo, W, Si, and Fe between lunar and terrestrial samples suggests that the two planetary bodies were equilibrated in the energetic aftermath of the giant impact that gave birth to the Moon [1]. Coupled 142Nd-143Nd isotope systematics of lunar samples including both low-Ti and high-Ti mare basalts along with KREEP basalts have been used to constrain the age of crystallization of the lunar interior [2-5]. These studies show that the Sm-Nd system in the lunar mantle closed in the interval of 180-250 Ma after the beginning of solar system formation, depending on the model considered for lunar mantle differentiation (1 or 2 stage-model and initial lunar Sm/Nd ratio). Does this age represent the age of Moon formation? A prolonged lunar magma ocean (LMO) might be expected given the insulating effect of the thick plagioclase crust, so closure of the Sm-Nd system in the lunar mantle, particularly in a late stage LMO component like KREEP, might substantially post-date lunar formation. We have recently determined a new age of 4360±3 Ma for the ferroan anorthosite (FAN) 60025 using the 207Pb-206Pb, 147Sm-143Nd and 146Sm-142Nd isotope systems [6]. This study is the first in which a single sample of FAN yielded consistent ages from multiple isotope dating techniques, strongly suggesting that this age indicates the time at which the sample crystallized. In order to pursue the question of whether Moon formation occurred over 100 Ma after solar system formation, we have investigated a number of lunar rocks sampling the highland crust from both the FAN and the Mg-suite groups. Internal Sm-Nd isochron on the norite 77215 yields an age of 4296±20 Ma, in agreement with the young age determined on 60025. We will show that our new data obtained on the 146Sm-142Nd systematics of the lunar crust support the scenario of a relative young age for the Moon. Thus, these results offer a unique opportunity to better constrain the composition of the terrestrial

  17. MONITORING OF PORE WATER PRESSURE AND WATER CONTENT AROUND A HORIZONTAL DRIFT THROUGH EXCAVATION - MEASUREMENT AT THE 140m GALLERY IN THE HORONOBE URL -

    NASA Astrophysics Data System (ADS)

    Yabuuchi, Satoshi; Kunimaru, Takanori; Kishi, Atsuyasu; Komatsu, Mitsuru

    Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. Pore water pressure and water content around a horizontal drift in the URL have been monitored for over 18 months since before the drift excavation was started. During the drift excavation, both pore water pressure and water content were decreasing. Pore water pressure has been still positive though it continued to decrease with its gradient gradually smaller after excavation, while water content turned to increase about 6 months after the completion of the excavation. It turned to fall again about 5 months later. An unsaturated zone containing gases which were dissolved in groundwater may have been formed around the horizontal drift.

  18. The origin of muddy sand sediments associated with mud volcanism in the Horonobe area of northern Hokkaido, Japan

    NASA Astrophysics Data System (ADS)

    Miyakawa, Kazuya; Tokiwa, Tetsuya; Murakami, Hiroaki

    2013-12-01

    The origin of muddy sand and gas in muddy sand sediments in the Horonobe area of northern Hokkaido, Japan, was investigated by analyzing the mineralogical and chemical compositions of the sediments and the chemical/isotopic compositions of the gas. X-ray fluorescence and X-ray diffraction analyses indicate that chemically, the muddy sand is derived from a mixing of components from the Hakobuchi and overlying formations, and that the characteristic mineral of the muddy sand is heulandite, which, in the study area, has been detected only in the Hakobuchi Formation. These results suggest that the sediments ascended from depths of at least 2200-2400 m. The δ13CCH4 values and the methane/(ethane + propane) ratios of the gas indicate that the primary origin of the methane is by thermogenic decomposition of coal-bearing beds in the Haboro or Hakobuchi formations, or further deep sources. This study provides new data on processes of onshore mud volcanism in Japan, and contributes to an understanding of processes of subsurface mass transport in regions of mud-volcanic activity.

  19. Characterization of saline groundwater at Horonobe, Hokkaido, Japan by SEC-UV-ICP-MS: speciation of uranium and iodine.

    PubMed

    Kozai, Naofumi; Ohnuki, Toshihiko; Iwatsuki, Teruki

    2013-03-15

    The saline groundwater collected at a depth of about 500 m in Horonobe, Japan, where an underground research laboratory (URL) has been built, is rich in saline (Na 4900 ppm, Cl 7600 ppm), iodine (42 ppm), and methane gas. We analyzed the colloids and ions of this groundwater mainly by employing a size exclusion chromatography (SEC) coupled on-line to ultraviolet-visible (UV-Vis) detection and inductively coupled plasma mass spectrometry (ICP-MS) technique and focused on the speciation of uranium and iodine, both of which are of particular importance for radioactive waste disposal. For this purpose, the groundwater sample was introduced to SEC columns after being passed through a 0.45 μm filter but without further pretreatment, such as isolation of colloids. The chromatographic profiles obtained with two different SEC columns were compared. This study revealed that uranium present in the groundwater at several tens of ppt was associated with low molecular weight silica species with neutral charge. The silica species were virtually free of metal elements such as Na, K, Mg, Ca, and Al. This study also found that almost all of the iodine in the groundwater was iodide (I(-)). The groundwater contained an unidentified organic colloid that was not a carrier for the radioactive waste-relevant elements Se, Sr, I, Cs, Th, and U. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Magmatic evolution of lunar highland rocks estimated from trace elements in plagioclase: A new bulk silicate Moon model with sub-chondritic Ti/Ba, Sr/Ba, and Sr/Al ratios

    NASA Astrophysics Data System (ADS)

    Togashi, Shigeko; Kita, Noriko T.; Tomiya, Akihiko; Morishita, Yuichi

    2017-08-01

    The compositions of host magmas of ferroan anorthosites (FAN-host magmas) were estimated from secondary ion mass spectrometry analyses of plagioclase in lunar highland rocks. The evolution of the magmas was investigated by considering phase relations based on the MELTS algorithm and by re-examining partition coefficients for trace elements between plagioclase and melts. Data little affected by post-magmatic processes were selected by using plagioclase with relatively primitive Sc and Co contents. The FAN-host magma contained 90-174 ppm Sr, 40-119 ppm Ba and 0.5-1.3% TiO2, and had sub-chondritic Sr/Ba and Ti/Ba ratios. It is difficult to account for the formation of FAN-host magma on the basis of magma evolution processes of previously proposed bulk silicate Moon models with chondritic ratios for refractory elements at global scale. Therefore, the source of the FAN-host magma must have had primordial sub-chondritic Sr/Ba and Ti/Ba ratios. The FAN-host magmas were consistent in refractory elements with the estimated host mafic magma for feldspathic crust based on lunar meteorites, and some very-low-Ti mare rocks from lunar meteorites. Here, we propose an alternative bulk silicate Moon model (the cBSM model), which is enriched in crustal components of proto-bodies relative to the present whole Earth-Moon system.

  1. Development and application of laser microprobe techniques for oxygen isotope analysis of silicates, and, fluid/rock interaction during and after granulite-facies metamorphism, highland southwestern complex, Sri Lanka

    SciTech Connect

    Elsenheimer, D.W.

    1992-01-01

    The extent of fluid/rock interaction within the crust is a function of crustal depth, with large hydrothermal systems common in the brittle, hydrostatically pressured upper crust, but restricted fluid flow in the lithostatically pressured lower crust. To quantify this fluid/rock interaction, a Nd-YAG/CO[sub 2] laser microprobe system was constructed to analyze oxygen isotope ratios in silicates. Developed protocols produce high precision in [sigma][sup 18]O ([+-]0.2, 1[sigma]) and accuracy comparable to conventional extraction techniques on samples of feldspar and quartz as small as 0.3mg. Analysis of sub-millimeter domains in quartz and feldspar in granite from the Isle of Skye, Scotland, reveals complex intragranular zonation. Contrasting heterogeneous and homogeneous [sigma][sup 18]O zonation patterns are revealed in samples <10m apart. These differences suggest fluid flow and isotopic exchange was highly heterogeneous. It has been proposed that granulite-facies metamorphism in the Highland Southwestern Complex (HSWC), Sri Lanka, resulted from the pervasive influx of CO[sub 2], with the marbles and calc-silicates within the HSWC a proposed fluid source. The petrologic and stable isotopic characteristic of HSWC marbles are inconsistent with extensive decarbonation. Wollastonite calc-silicates occur as deformed bands and as post-metamorphis veins with isotopic compositions that suggest vein fluids that are at least in part magmatic. Post-metamorphic magmatic activity is responsible for the formation of secondary disseminated graphite growth in the HSWC. This graphite has magmatic isotopic compositions and is associated with vein graphite and amphibolite-granulite facies transitions zones. Similar features in Kerela Khondalite Belt, South India, may suggest a common metamorphic history for the two terranes.

  2. Basaltic injections into floored silicic magma chambers

    NASA Astrophysics Data System (ADS)

    Wiebe, R. A.

    Recent studies have provided compelling evidence that many large accumulations of silicic volcanic rocks erupted from long-lasting, floored chambers of silicic magma that were repeatedly injected by basaltic magma. These basaltic infusions are commonly thought to play an important role in the evolution of the silicic systems: they have been proposed as a cause for explosive silicic eruptions [Sparks and Sigurdsson, 1977], compositional variation in ash-flow sheets [Smith, 1979], mafic magmatic inclusions in silicic volcanic rocks [Bacon, 1986], and mixing of mafic and silicic magmas [Anderson, 1976; Eichelberger, 1978]. If, as seems likely, floored silicic magma chambers have frequently been invaded by basalt, then plutonic bodies should provide records of these events. Although plutonic evidence for mixing and commingling of mafic and silicic magmas has been recognized for many years, it has been established only recently that some intrusive complex originated through multiple basaltic injections into floored chambers of silicic magma [e.g., Wiebe, 1974; Michael, 1991; Chapman and Rhodes, 1992].

  3. Experimental rock-water interactions at temperatures to 300/sup 0/C: implications for fluid flow, solute transport, and silicate mineral zoning in crustal geothermal systems

    SciTech Connect

    Potter, J.M.

    1982-01-01

    Geothermal reservoirs commonly occur in permeable volcanic rock (rhyolite, andesite, basalt) or sedimentary (sandstone) strata at temperatures below 300/sup 0/C. Knowledge of how these reservoirs develop chemically and physically has been based almost entirely on field studies. Four types of experiments were conducted to supplement available data on the chemistry, mineralogy, and fluid flow aspects of hydrothermal processes occurring in crustal geothermal systems: (1) agitated rock-water experiments; (2) high temperature flow through experiments; (3) low temperature permeability experiments; and (4) corrosion monitoring experiments. Initial experiments reacted rhyolite glass and holocrystalline basalt with water-NaCl solutions at 300/sup 0/C in agitated hydrothermal equipment. Concentrations of components in solution depend on initial salinity, rock type, and particle size. The secondary phases consist of zeolites, clay, and feldspar minerals and the alteration assemblage is dependent on both initial salinity, rock type, and duration of the experiment. A second set of experiments were conducted at 300/sup 0/C using the rhyolite glass in a flow through type of apparatus. Compositions of outlet fluids show a dependence of fluid flow rate and core length.

  4. Nd, Sr, and O isotopic variations in metaluminous ash-flow tuffs and related volcanic rocks at the Timber Mountain/Oasis Valley Caldera, Complex, SW Nevada: implications for the origin and evolution of large-volume silicic magma bodies

    USGS Publications Warehouse

    Farmer, G.L.; Broxton, D.E.; Warren, R.G.; Pickthorn, W.

    1991-01-01

    Nd, Sr and O isotopic data were obtained from silicic ash-flow tuffs and lavas at the Tertiary age (16-9 Ma) Timber (Mountain/Oasis Valley volcanic center (TMOV) in southern Nevada, to assess models for the origin and evolution of the large-volume silicic magma bodies generated in this region. The large-volume (>900 km3), chemically-zoned, Topopah Spring (TS) and Tiva Canyon (TC) members of the Paintbrush Tuff, and the Rainier Mesa (RM) and Ammonia Tanks (AT) members of the younger Timber Mountain Tuff all have internal Nd and Sr isotopic zonations. In each tuff, high-silica rhyolites have lower initial e{open}Nd values (???1 e{open}Nd unit), higher87Sr/86Sr, and lower Nd and Sr contents, than cocrupted trachytes. The TS, TC, and RM members have similar e{open}Nd values for high-silica rhyolites (-11.7 to -11.2) and trachytes (-10.5 to -10.7), but the younger AT member has a higher e{open}Nd for both compositional types (-10.3 and -9.4). Oxygen isotope data confirm that the TC and AT members were derived from low e{open}Nd magmas. The internal Sr and Nd isotopic variations in each tuff are interpreted to be the result of the incorporation of 20-40% (by mass) wall-rock into magmas that were injected into the upper crust. The low e{open}Nd magmas most likely formed via the incorporation of low ??18O, hydrothermally-altered, wall-rock. Small-volume rhyolite lavas and ash-flow tuffs have similar isotopic characteristics to the large-volume ash-flow tuffs, but lavas erupted from extracaldera vents may have interacted with higher ??18O crustal rocks peripheral to the main magma chamber(s). Andesitic lavas from the 13-14 Ma Wahmonie/Salyer volcanic center southeast of the TMOV have low e{open}Nd (-13.2 to -13.8) and are considered on the basis of textural evidence to be mixtures of basaltic composition magmas and large proportions (70-80%) of anatectic crustal melts. A similar process may have occurred early in the magmatic history of the TMOV. The large-volume rhyolites

  5. Determination of scandium, yttrium and lanthanides in silicate rocks and four new canadian iron-formation reference materials by flame atomic-absorption spectrometry with microsample injection.

    PubMed

    Sen Gupta, J G

    1984-12-01

    Enhancement of sensitivity by factors of up to 1.5 by use of the microsampling technique, coupled with the advantage of using small samples in small solution volumes, permits rapid flame AAS determination of traces of Sc, Y, Nd, Eu, Dy, Ho, Er, Tm and Yb in ultramafic and most other rocks of low rare-earth content, which would be either impossible or very difficult to analyse by direct aspiration because of the need for much larger sample weights and solution volumes. The rare-earths are separated by a modified ion-exchange or a double calcium oxalate and single hydrous ferric oxide co-precipitation procedure, and ultimately determined in an ethanolic perchlorate solution, buffered with 1% lanthanum, by the flame microsample injection technique, with a nitrous oxide-acetylene flame. The results obtained by this technique for six international reference rocks SY-2 (syenite), BCR-1 (basalt), BHVO-1 (Hawaiian basalt), SCo-1 (cody shale), MAG-1 (marine mud) and STM-1 (syenite) are compared with those obtained previously by the direct aspiration method and with other reported data. Results are given for four new Canadian iron formation reference materials FeR-1 to FeR-4.

  6. A Tale of Two Melt Rocks: Equilibration and Metal/Sulfide-Silicate Segregation in the L7 Chondrites PAT 91501 and LEW 88663

    NASA Astrophysics Data System (ADS)

    Harvey, R. P.

    1993-07-01

    Type 7 ordinary chondrites have experienced temperatures near or beyond those necessary for partial melting. Two recently collected Antarctic specimens, PAT91501 (PAT) and LEW88663 (LEW), have been tentatively identified as L7 chondrites based on mineral and oxygen isotope compositions [1,2]. The petrology and mineralogy of these meteorites suggests that they have undergone significant metal/sulfide-silicate segregation, with implications for meteorite parent bodies. PAT consists of an equigranular contact-framework of nearly euhedral olivine grains, with interstitial spaces filled by plagioclase, pyroxenes, and several minor phases. Ortho- and clinopyroxene occur in an exsolution relationship. Olivine and pyroxene are highly equilibrated, varying <<1% in Fe-endmember content. Pyroxene equilibration temperatures calculated for PAT using the methods of [3] are self-consistent at about 1180 degrees C. In thin section, PAT contains only traces of metal, as tiny isolated blebs in sulfide grains; large (>1 cm) globular sulfide inclusions are seen in hand-sample [1], but are not present in the section examined. LEW was originally classified as an achondrite with olivine and pyroxene compositions similar to those in L chondrites [2]. Metal is absent in LEW, although the specimen is small and heavily rusted, making it impossible to gauge the original metal content. Olivine grains are commonly rounded in shape and seldom in contact with more than a few other grains. LEW olivine and pyroxene are also highly equilibrated. Veins of Ni-bearing metal oxides and sulfides are common. Both low- and high-Ca pyroxene occur as discrete grains, orthopyroxene often poikilitically enclosing olivine. Pyroxene equilibration temperatures for LEW are more variable than those for PAT and consistently lower, with an average around 900 degrees C. The various textural and compositional characteristics of PAT and LEW suggest they have experienced partial melting to varying degrees. Both visually

  7. Trace element and isotopic composition of apatite in carbonatites from the Blue River area (British Columbia, Canada) and mineralogy of associated silicate rocks

    NASA Astrophysics Data System (ADS)

    Mitchell, Roger; Chudy, Thomas; McFarlane, Christopher R. M.; Wu, Fu-Yuan

    2017-08-01

    Apatites from the Verity, Fir, Gum, Howard Creek and Felix carbonatites of the Blue River (British Columbia, Canada) area have been investigated with respect to their paragenesis, cathodoluminescence, trace element and Sr-Nd isotopic composition. Although all of the Blue River carbonatites were emplaced as sills prior to amphibolite grade metamorphism and have undergone deformation, in many instances magmatic textures and mineralogy are retained. Attempts to constrain the U-Pb age of the carbonatites by SIMS, TIMS and LA-ICP-MS studies of zircon and titanite were inconclusive as all samples investigated have experienced significant Pb loss during metamorphism. The carbonatites are associated with undersaturated calcite-titanite amphibole nepheline syenite only at Howard Creek although most contain clasts of disaggregated phoscorite-like rocks. Apatite from each intrusion is characterized by distinct, but wide ranges, in trace element composition. The Sr and Nd isotopic compositions define an array on a 87Sr/86Sr vs²Nd diagram at 350 Ma indicating derivation from depleted sub-lithospheric mantle. This array could reflect mixing of Sr and Nd derived from HIMU and EM1 mantle sources, and implies that depleted mantle underlies the Canadian Cordillera. Although individual occurrences of carbonatites in the Blue River region are mineralogically and geochemically similar they are not identical and thus cannot be considered as rocks formed from a single batch of parental magma at the same stage of magmatic evolution. However, a common origin is highly probable. The variations in the trace element content and isotopic composition of apatite from each occurrence suggest that each carbonatite represents a combination of derivation of the parental magma(s) from mineralogically and isotopically heterogeneous depleted mantle sources coupled with different stages of limited differentiation and mixing of these magmas. We do not consider these carbonatites as primary direct

  8. Correlation and petrogenesis of silicic pyroclastic rocks in the Northern Pannonian Basin, Eastern-Central Europe: In situ trace element data of glass shards and mineral chemical constraints

    NASA Astrophysics Data System (ADS)

    Harangi, Szabolcs; Mason, Paul R. D.; Lukács, Réka

    2005-05-01

    The Neogene volcanism of the Carpathian-Pannonian Region, Eastern-Central Europe started with repeated explosive eruption of silicic magmas. Volcanic products consist mostly of non-welded and partially to densely welded ignimbrites, which cover large areas in the Pannonian Basin. Since this volcanism occurred during a long time interval, from 21 Ma to 13.5 Ma ago, these pyroclastic deposits have great stratigraphic importance, as well as providing valuable information about petrogenetic processes during the formation of the back-arc basin area. In this study, we used in situ trace element data of glasses (glass shards, pumice and fiamme glass) determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), combined with microprobe geochemical data of the main mineral phases (plagioclase, biotite), to correlate the scattered outcrops of the ignimbrite units. Based on these data, we distinguished four ignimbrite units in the Bükkalja Volcanic Field, Northern Pannonian Basin. Each of these units is characterized by specific geochemical fingerprints. Thorium, Nb, Y and the rare earth elements are the most effective discriminator elements in glasses. The modal composition of mineral phases (occurrence or lack of certain minerals) and chemistry of plagioclases and biotites are also good correlation tools, especially the Fe, Mg and Ti contents of biotites. We suggest that these correlation criteria, particularly the grain-specific LA-ICP-MS data, could be effectively used also in other ignimbrite fields and in wider tephrochronological studies. The in situ trace element composition of glasses, representing the liquid part of the erupted magma, can be also used to constrain the petrogenesis of the rhyolitic magmas. Trace element ratios such as La/Nb, La/Y and Th/Nb suggest the importance of minor (e.g., hornblende and ilmenite) and accessory (e.g., zircon, allanite) minerals controlling the composition of the erupted melt. Rhyolitic magmas probably

  9. Rapid quantitative determination of major and trace elements in silicate rocks and soils employing fused glass discs using wavelength dispersive X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Krishna, A. Keshav; Khanna, Tarun C.; Mohan, K. Rama

    2016-08-01

    This paper introduces a calibration procedure and provides the data achieved for accuracy, precision, reproducibility and the detection limits for major (Si, Al, Fe, Mn, Mg, Ca, Na, K, Ti, P) and trace (Ba, Cr, Cu, Hf, La, Nb, Ni, Pb, Rb, Sr, Ta, Th, U, Y, Zn, Zr) elements in the routine analysis of geological and environmental samples. Forty-two rock and soil reference materials were used to calibrate and evaluate the analytical method using a sequential wavelength dispersive X-ray fluorescence spectrometer. Samples were prepared as fused glass discs and analysis performed with a total measuring time of thirty-one minutes. Another set of twelve independent reference materials were analyzed for the evaluation of accuracy. The detection limits and accuracy obtained for the trace elements (1-2 mg/kg) are adequate both for geochemical exploration and environmental studies. The fitness for purpose of the results was also evaluated by the quality criteria test proposed by the International Global Geochemical Mapping Program (IGCP) from which it can be deduced that the method is adequate considering geochemical mapping application and accuracy obtained is within the expected interval of certified values in most cases.

  10. High-Temperature, Perhaps Silicic, Volcanism on Mars Evidenced by Tridymite Detection in High-SiO2 Sedimentary Rock at Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Vaniman, D. T.; Blake, D. F.; Gellert, R.; Chipera, S. J.; Rampe, E. B.; Ming, D. W.; Morrison, S. M.; Downs, R. T.; Treiman, A. H.; hide

    2016-01-01

    The Mars Science Laboratory (MSL) rover, Curiosity, has been exploring sedimentary rocks within Gale crater since landing in August, 2012. On the lower slopes of Aeolis Mons (a.k.a. Mount Sharp), drill powder was collected from a high-silica (74 wt% SiO2) outcrop named Buckskin (BK). It was a surprise to find that the Buckskin sample contained significant amounts of the relatively rare silica polymorph tridymite. We describe the setting of the Buckskin sample, the detection of tridymite by the MSL Chemistry and Mineralogy (CheMin) X-ray diffraction instrument, and detection implications. Geologic setting: The Buckskin outcrop is part of the Murray formation exposed in the Marias Pass area. The formation was previously studied by CheMin in the Pahrump Hills member [1] where three samples of drill fines were analyzed (Confidence Hills (CH), Mojave2 (MJ) and Telegraph Peak (TP) [2]). Assuming approximately horizontal bedding, the Buckskin outcrop is approx.15 m stratigraphically above the bottom of the Pahrump Hills member. Mudstone, generally characterized by fine lamination, is the dominant depositional facies [1]. Buckskin Mineralogical and Chemical Composition: The CheMin instrument and XRD pattern analysis procedures have been previously discussed [3-6]. The diffraction pattern used for quantitative XRD analysis (Fig. 1) is the sum of the first 4 of 45 diffraction images. The remaining images are all characterized by both on-ring and off-ring diffraction spots that we attributed to poor grain motion and particle clumping. Coincident with particle clumping was a significant decrease in the intensity of the tridymite diffraction peaks (Fig. 2a). The derived mineralogical composition of the crystalline component (derived from the first 4 diffraction images) is given in Table 1. The tridymite is well-crystalline and its pattern is refined as monoclinic tridymite (Fig 1). Mineral chemical compositions were derived from XRD unit cell parameters or obtained from

  11. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS—Part 3: Application to the Peach Spring Tuff (Arizona-California-Nevada, USA)

    NASA Astrophysics Data System (ADS)

    Pamukcu, Ayla S.; Gualda, Guilherme A. R.; Ghiorso, Mark S.; Miller, Calvin F.; McCracken, Reba G.

    2015-03-01

    Peach Spring samples are due to alteration. Use of altered whole-pumice compositions in rhyolite-MELTS simulations is likely the cause of the incorrect crystallization sequence reported previously for Peach Spring compositions. Using the rhyolite-MELTS geobarometer, we estimate a more realistic composition for Peach Spring Tuff high-silica rhyolite, and the calculated composition finds close matches with some analyzed rocks and results in the expected sequence of crystallization.

  12. Highly silicic compositions on the Moon.

    PubMed

    Glotch, Timothy D; Lucey, Paul G; Bandfield, Joshua L; Greenhagen, Benjamin T; Thomas, Ian R; Elphic, Richard C; Bowles, Neil; Wyatt, Michael B; Allen, Carlton C; Donaldson Hanna, Kerri; Paige, David A

    2010-09-17

    Using data from the Diviner Lunar Radiometer Experiment, we show that four regions of the Moon previously described as "red spots" exhibit mid-infrared spectra best explained by quartz, silica-rich glass, or alkali feldspar. These lithologies are consistent with evolved rocks similar to lunar granites in the Apollo samples. The spectral character of these spots is distinct from surrounding mare and highlands material and from regions composed of pure plagioclase feldspar. The variety of landforms associated with the silicic spectral character suggests that both extrusive and intrusive silicic magmatism occurred on the Moon. Basaltic underplating is the preferred mechanism for silicic magma generation, leading to the formation of extrusive landforms. This mechanism or silicate liquid immiscibility could lead to the formation of intrusive bodies.

  13. Magnetic fabric interpretation complicated by inclusions in mafic silicates

    NASA Astrophysics Data System (ADS)

    Lagroix, France; Borradaile, Graham J.

    2000-10-01

    The expected relationships between anisotropy of low-field magnetic susceptibility (AMS) and crystal symmetry of mafic silicates are disturbed by the presence of magnetite inclusions. Measurements of AMS, anisotropy of anhysteretic remanence (AARM) and theoretically predicted bulk susceptibilities from chemical composition all favour the exercise of great caution in the interpretation of preferred orientation distributions of silicates from a rock's AMS. These results pertain mainly to the mafic silicates of lower crustal rocks (pyroxene, orthopyroxene, amphibole) and some of their low-grade metamorphic alterations (serpentine, epidote).

  14. Reaction of silicate minerals to form tetramethoxysilane.

    PubMed

    Lewis, Larry N; Schattenmann, Florian J; Jordan, Tracey M; Carnahan, James C; Flanagan, William P; Wroczynski, Ronald J; Lemmon, John P; Anostario, Joseph M; Othon, Michelle A

    2002-05-06

    Several silicon dioxide sources were used as reagents in the base-mediated reaction with dimethyl carbonate (DMC) to make tetramethoxysilane (Q'). Several commercially available diatomaceous earth materials were investigated. High throughput screening was employed to explore over 200 silicate rocks and minerals as alternative silicon dioxide sources for formation of Q' from DMC and base. Amorphous silicon dioxide materials are effective reagents for the Q' forming reaction. Effective silicon dioxide sources in addition to the diatomaceous earth materials include opal and various synthetic silicates (Li, Co, and Ca).

  15. Phosphorus Equilibria Among Mafic Silicate Phases

    NASA Technical Reports Server (NTRS)

    Berlin, Jana; Xirouchakis, Dimitris

    2002-01-01

    Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet > olivine > orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The

  16. Multiple tracer study in Horonobe, northern Hokkaido, Japan: 2. Depletion of chlorofluorocarbons (CFCs) estimated using 3H/3He index and lumped parameter models

    NASA Astrophysics Data System (ADS)

    Kashiwaya, Koki; Hasegawa, Takuma; Nakata, Kotaro; Tomioka, Yuichi; Mizuno, Takashi

    2015-05-01

    The conservativeness of chlorofluorocarbons (CFC-12, CFC-11, and CFC-113) in an environment rich in organic carbon was evaluated using multiple tracer analyses and lumped parameter models (LPMs). Wells on a coastal plain in Horonobe, northern Hokkaido, Japan, were studied. The CFC concentrations in groundwater from 22 wells were measured, converted into atmospheric mixing ratios (CARs), and compared with estimated ratios (EARs) obtained from 3H/3He values and LPMs. The degree of CFC depletion was expressed as the percentage of the CAR relative to the EAR, and was less than 43% for CFC-12 and 28% for CFC-11 (but one well had unusual values). CFC-113 was depleted more than the other CFCs, and could not be detected in most wells. The CFC depletion mechanisms were different in each of the three well groups. Groundwater of northern Shimonuma wells (NSW) was oxic and oxidative, so CFC depletion in the NSW could be attributed to sorption by organic carbon in the lignite and peat in the aquifers. Groundwater of southern Shimonuma wells (SSW) was anoxic and reductive. The northerly SSW are supplied from the aquifer that supplies the most of the NSW, so CFC depletion in the SSW was caused by degradation under sulfate-reducing and methanogenic conditions, in addition to sorption by lignite in the northerly SSW. Gas stripping, contamination from a local source, and methane interfering with the CFC analysis were found in groundwater of Hamasato wells (HW). One well of HW was not affected by these problems, but the CFCs were depleted by microbial degradation. Assuming that the CFC depletion mechanisms follow first-order reaction kinetics, reaction rate constants of 2.7 y-1 for CFC-12 and 2.8 y-1 for CFC-11 were estimated. Microbial degradation, sorption, gas stripping of CFCs, and methane formation processes are enhanced in environments rich in organic carbon. Special attention is required when CFCs are used as transient tracers in such environments. The combination of multiple

  17. Multiple tracer study in Horonobe, northern Hokkaido, Japan: 1. Residence time estimation based on multiple environmental tracers and lumped parameter models

    NASA Astrophysics Data System (ADS)

    Kashiwaya, Koki; Hasegawa, Takuma; Nakata, Kotaro; Tomioka, Yuichi; Mizuno, Takashi

    2014-11-01

    A multiple tracer study was conducted in the coastal plain of Horonobe, northern Hokkaido, Japan. To accomplish reliable estimates of groundwater residence time, multiple tracer approach, employing both gaseous and nongaseous environmental tracers, and lumped parameter models (LPMs) were applied in combination. Environmental tracers including 3H, 3H/3He, 36Cl, and SF6 were analyzed and compared with values estimated from LPMs to select the most appropriate tracer and models to describe groundwater flow regime in the study area. Time series of 36Cl/Cl input in the study area were reconstructed and used in the LPMs. From comparison of the analyzed and modeled results, an index of 3H/3He was selected as the most appropriate for investigation of the study area. The relationship between the 3H/3He index and 36Cl/Cl indicated reliability of the 3H/3He index, but 36Cl/Cl values of the samples were lower than the models. This discrepancy was caused by underestimation of Cl- concentration of recharging water in the calculation of 36Cl/Cl input. SF6 mixing ratios of the samples were slightly higher than the models and it suggested involvement of terrigenic SF6. Three well groups, northern Shimonuma wells (NSW), southern Shimonuma wells (SSW), and Hamasato wells (HW), were respectively consistent with exponential piston flow model (EPM), binary mixing model (BMM), and exponential mixing model (EMM). Relational expressions between the 3H/3He index and mean residence time or mixing fraction of young groundwater (assumed to contain no tritiogenic 3He) with old groundwater (all 3H decayed to tritiogenic 3He) were obtained based on the models. The mean residence time determined from the 3H/3He index and the expressions were 19-78 years for NSW and 1-648 years for HW. The mixing fraction of young groundwater was less than 10% at all SSW. Nongaseous tracers, including 36Cl are not influenced by factors specific for gaseous tracers, such as excess air and degassing. Analyses of

  18. Lithium metaborate flux in silicate analysis

    USGS Publications Warehouse

    Ingamells, C.O.

    1970-01-01

    Lithium metaborate is an effective flux for silicates and other rock-forming minerals. The glass resulting from fusion is mechanically strong, reasonably nonhygroscopic, and is readily soluble in dilute acids. These characteristics lead to its use in X-ray spectrography and in methods which require whole-rock solutions, such as atomic absorption and emission spectrometry. Difficulties have been encountered in the use of such techniques : a high-quality reagent has been difficult to obtain ; fusion conditions must be rather closely controlled; graphite crucibles used in the fusions need special treatment. Methods for overcoming these difficulties are outlined. Selected procedures for various instrumental methods of analysis are described. ?? 1970.

  19. Cumulate Fragments in Silicic Ignimbrites

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Ellis, B. S.; Wolff, J.

    2014-12-01

    Increasingly, studies are concluding that silicic ignimbrites are the result of the amalgamation of multiple discrete magma batches. Yet the existence of discrete batches presents a conundrum for magma generation and storage; if silicic magma batches are not generated nearly in situ in the upper crust, they must traverse, and reside within, a thermally hostile environment with large temperature gradients, resulting in low survivability in their shallow magmatic hearths. The Snake River Plain (Idaho, USA) is a type example of this 'multi-batch' assembly with ignimbrites containing multiple populations of pyroxene crystals, glass shards, and crystal aggregates. The ubiquitous crystal aggregates hint at a mechanism to facilitate the existence of multiple, relatively small batches of rhyolite in the upper crust. These aggregates contain the same plagioclase, pyroxene, and oxide mineral compositions as single phenocrysts of the same minerals in their host rocks, but they have significantly less silicic bulk compositions and lack quartz and sanidine, which occur as single phenocrysts in the deposits. This implies significant crystallization followed by melt extraction from mushy reservoir margins. The extracted melt then continues to evolve (crystallizing sanidine and quartz) while the melt-depleted margins provide an increasingly rigid and refractory network segregating the crystal-poor batches of magma. The hot, refractory, margins insulate the crystal-poor lenses, allowing (1) extended residence in the upper crust, and (2) preservation of chemical heterogeneities among batches. In contrast, systems that produce cumulates richer in low-temperature phases (quartz, K-feldspars, and/or biotite) favour remelting upon recharge, leading to less segregation of eruptible melt pockets and the formation of gradationally zoned ignimbrites. The occurrence of similar crystal aggregates from a variety of magmatic lineages suggests the generality of this process.

  20. Nanoscale zinc silicate from phytoliths

    NASA Astrophysics Data System (ADS)

    Qadri, S. B.; Gorzkowski, E. P.; Rath, B. B.; Feng, C. R.; Amarasinghe, R.; Freitas, J. A.; Culbertson, J. C.; Wollmershauser, J. A.

    2017-10-01

    We report a faster, less expensive method of producing zinc silicate nanoparticles. Such particles are used in high volume to make phosphors and anti-corrosion coatings. The approach makes use of phytoliths (plant rocks), which are microscopic, amorphous, and largely silicate particles embedded in plants, that lend themselves to being easily broken down into nanoparticles. Nanoparticles of Zn2SiO4 were produced in a two stage process. In the refinement stage, plant residue, mixed with an appropriate amount of ZnO, was heated in an argon atmosphere to a temperature exceeding 1400 °C for four to six hours and then heated in air at 650 °C to remove excess carbon. TEM shows 50-100 nm nanoparticles. Raman scattering indicates that only the -Zn2SiO4 crystalline phase was present. X-ray analysis indicated pure rhombohedral R 3 bar phase results from using rice/wheat husks. Both samples luminesced predominantly at 523 nm when illuminated with X-rays or UV laser light.

  1. Origin of silicic magma in Iceland revealed by Th isotopes

    SciTech Connect

    Sigmarsson, O.; Condomines, M. ); Hemond, C. ); Fourcade, S. ); Oskarsson, N. )

    1991-06-01

    Th, Sr, Nd, and O isotopes have been determined in a suite of volcanic rocks from Hekla and in a few samples from Askja and Krafla volcanic centers in Iceland. Although {sup 87}Sr/{sup 86}Sr and {sup 143}Nd/{sup 144}Nd ratios are nearly the same for all compositions at Hekla, the ({sup 230}Th/{sup 232}Th) ratios differ and thus clearly show that the silicic rocks cannot be derived from fractional crystallization of a more primitive magma. Similar results are obtained for the Krafla and Askja volcanic centers, where the {delta}{sup 18}O values are much lower in the silicic magma than in the mafic magma. These data suggest that large volumes of silicic rocks in central volcanoes of the neovolcanic zones in Iceland are produced by partial melting of the underlying crust.

  2. Silicic volcanism in Iceland: Composition and distribution within the active volcanic zones

    NASA Astrophysics Data System (ADS)

    Jónasson, Kristján

    2007-01-01

    Silicic volcanic rocks within the active volcanic zones of Iceland are mainly confined to central volcanoes. The volcanic zones of Iceland can be divided into rift zones and flank zones. Each of these zones contains several central volcanoes, most of which have produced minor amounts of silicic rocks. The silicic rocks occur as lavas and domes or as tephra layers, welded tuffs and ignimbrites, formed both in effusive and explosive eruptions. They tend to be glassy or very fine-grained, containing small amounts of phenocrysts. Plagioclase (andesine-oligoclase), anorthoclase or occasionally sanidine coexist with minerals such as augite, fayalite, pigeonite, orthopyroxene and magnetite. Quartz phenocrysts are exceedingly rare. Zoning of phenocrysts is limited and the pattern is variable. A set of 90 samples representing all active central volcanoes that have erupted silicic rocks was analysed for major- and trace-elements. The silicic rocks can be classified as dacites, trachytes, low-alkali rhyolites and alkalic rhyolites. Some of the trachytes and alkalic rhyolites are peralkaline (mostly comenditic). Trachytes and alkalic rhyolites are only found within the flank zones, while dacites and low-alkali rhyolites are mostly confined to the rift zones. The Icelandic rhyolites plot close to the thermal minimum in the "granite" system, while dacites and trachytes plot within the plagioclase field and towards the alkali feldspar temperature minimum. The silicic rocks are relatively Fe-rich and Ca-poor indicating low water pressure in the source. Trace element concentrations follow similar patterns in most central volcanoes. Exceptions are Torfajökull where silicic rocks display a negative correlation of Ba to Th and unusually high Th-contents, and the western flank zone where Ba-concentrations are highly variable. The ratios of different high field-strength elements are generally similar within each central volcano or region, which probably reflects different ratios in the

  3. Geometries and Facies Distributions in Yellowstone's Siliceous Hotsprings: Implications for Martian Exploration

    NASA Technical Reports Server (NTRS)

    Guidry, S. A.; Chafetz, H. S.

    2001-01-01

    Synthesis of features from several siliceous hotsprings yields a relatively simple facies model. This model facilitates our ability to recognize these hotsprings in the terrestrial and probably extraterrestrial rock record. Additional information is contained in the original extended abstract.

  4. Geometries and Facies Distributions in Yellowstone's Siliceous Hotsprings: Implications for Martian Exploration

    NASA Technical Reports Server (NTRS)

    Guidry, S. A.; Chafetz, H. S.

    2001-01-01

    Synthesis of features from several siliceous hotsprings yields a relatively simple facies model. This model facilitates our ability to recognize these hotsprings in the terrestrial and probably extraterrestrial rock record. Additional information is contained in the original extended abstract.

  5. Voluminous silicic eruptions during late Permian Emeishan igneous province and link to climate cooling

    NASA Astrophysics Data System (ADS)

    Yang, Jianghai; Cawood, Peter A.; Du, Yuansheng

    2015-12-01

    Silicic eruptive units can constitute a substantive component in flood-basalts-dominated large igneous provinces, but usually constitute only a small proportion of the preserved volume due to poor preservation. Thus, their environmental impact can be underestimated or ignored. Establishing the original volume and potential climate-sensitive gas emissions of silicic eruptions is generally lacking for most large igneous provinces. We present a case study for the ∼260 Ma Emeishan province, where silicic volcanic rocks are a very minor component of the preserved rock archive due to extensive erosion during the Late Permian. Modal and geochemical data from Late Permian sandstones derived from the province suggest that silicic volcanic rocks constituted some ∼30% by volume of the total eroded Emeishan volcanic source rocks. This volume corresponds to > 3 ×104 km3 on the basis of two independent estimate methods. Detrital zircon trace element and Hf isotopic data require the silicic source rocks to be formed mainly by fractional crystallization from associated basaltic magmas. Based on experimental and theoretical calculations, these basalt-derived ∼104 km3 silicic eruptions released ∼1017 g sulfur gases into the higher atmosphere and contribute to the contemporaneous climate cooling at the Capitanian-Wuchiapingian transition (∼260 Ma). This study highlights the potentially important impact on climate of silicic eruptions associated with large igneous province volcanism.

  6. Petrogenesis of Western Cascades Silicic Volcanics Near Sweet Home, Oregon

    NASA Astrophysics Data System (ADS)

    Cook, G. W.; White, C. M.

    2002-12-01

    Silicic lavas in the Menagerie Wilderness east of Sweet Home, Oregon are Oligocene to Miocene in age and range in composition from dacite (low K) to trachydacite (high K) and rhyolite (medium K). Three distinct silicic centers have been distinguished through a combination of field observation, chemistry and petrography. Phenocryst assemblages in rocks of the centers are plagioclase-hornblende-magnetite (Rooster Rock rhyolite), plagioclase-quartz-magnetite (Soda Fork rhyolite) and quartz-plagioclase-biotite-hornblende-magnetite (Moose Mt. rhyolite). The silicic volcanics in the study area are similar in terms of mineral content and overall chemical composition. Despite this, chemical evidence suggests that the three centers are petrologically unrelated. REE variations and least squares modeling of major element compositions are consistent with fractionation of plagioclase and hornblende. The rhyolites have moderate Eu anomalies and have flat MREE and HREE signatures. Least squares models and bivariate plots of major and trace elements also suggest fractionation of the aforementioned phases for both the andesite to dacite, and dacite to rhyolite steps. Comparisons with similar silicic centers show the Menagerie rocks share affinities with High Cascades rocks thought to have been derived through fractional crystallization (Crater Lake and South Sister). Plots of ratios of incompatible trace elements were utilized to determine if assimilation played some role alongside fractional crystallization in differentiation. Plots of Ba/La vs. Ba, Rb/Zr vs. Rb and Rb/Th vs. Rb show systematic positive increases in the ratios between a plausible parent magma (icelandite) and the rhyolites. These increases are not easily explained by fractional crystallization but can be modeled by assimilation of silicic crust. Overall, it seems likely that the three centers evolved independently through similar petrogenetic processes from an andesitic parent. The most plausible petrogenetic

  7. Calcium silicate insulation structure

    DOEpatents

    Kollie, Thomas G.; Lauf, Robert J.

    1995-01-01

    An insulative structure including a powder-filled evacuated casing utilizes a quantity of finely divided synthetic calcium silicate having a relatively high surface area. The resultant structure-provides superior thermal insulating characteristics over a broad temperature range and is particularly well-suited as a panel for a refrigerator or freezer or the insulative barrier for a cooler or a insulated bottle.

  8. Silicates in Alien Asteroids

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  9. Silicates in Alien Asteroids

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  10. Thermochemistry of Silicates

    NASA Technical Reports Server (NTRS)

    Costa, Gustavo; Jacobson, Nathan

    2015-01-01

    The thermodynamic properties of vapor and condensed phases of silicates are crucial in many fields of science. These quantities address fundamental questions on the formation, stability, transformation, and physical properties of silicate minerals and silicate coating compositions. Here the thermodynamic activities of silica and other species in solid solution have been measured by the analysis of the corresponding high temperature vapors using Knudsen Effusion Mass Spectrometry (KEMS). In first set of experiments KEMS has been used to examine the volatility sequence of species (Fe, SiO, Mg, O2 and O) present in the vapor phase during heating of fosterite-rich olivine (Fo93Fa7) up to 2400 C and to measure the Fe, SiO and Mg activities in its solid solution. The data of fosterite-rich olivine are essential for thermochemical equilibrium models to predict the atmospheric and surface composition of hot, rocky exoplanets (Lava Planets). In the second set of experiments the measured thermodynamic activities of the silica in Y2O3-SiO2 and Yb2O3-SiO2 systems are used to assess their reactivity and degradation recession as environmental barrier coatings (EBCs) in combustion environments (e.g. non-moveable parts of gas turbine engine).

  11. Phosphorus partitioning among mantle silicate phases

    NASA Astrophysics Data System (ADS)

    Xirouchakis, D.; Draper, D. S.

    2002-05-01

    In the absence of a phosphate phase, phosphorus may be considered to behave as an incompatible element during partial melting of mantle mineral assemblages and/or crystallization of residual basaltic liquids. Thus, phosphorus can give valuable constraints on the extent of partial melting and/or magma crystallization, providing that crystal-liquid partition coefficients for P2O5 are known with confidence. In phosphate-normative rocks most of P2O5 is likely contained in phosphate minerals, however, in rocks containing only trace amounts of this oxide, as is often the case of mantle peridotites, silicate minerals can apparently host a large proportion of the bulk P2O5 content. Considering the small differences in the ionic radii of tetrahedrally coordinated P5+ (0.31 Å), Si4+ (0.26 Å), and Al3+ (0.39 Å) the potential for phosphorus incorporation into crystalline silicates is perhaps unsurprising. Although silicate and phosphate phases can be isostructural (e.g., (Fe, Mg)2SiO4 vs. LiMgPO4 or SiO2 vs. AlPO4), this does not warranty mutual solubility (Bradley et al 1966; Brunet et al. 2000). Neglecting the rare reports of significant (2-4 wt%) but also poorly understood P2O5 enrichment in olivine and pyroxene grains in a few extraterrestrial and terrestrial samples (Buseck and Clark, 1984; Goodrich 1984), the overlap in the P2O5 content (wt%) in olivine, pyroxene(s), garnet, and plagioclase, regardless of differences in analytical techniques and compositions, suggests that incorporation of trace quantities of phosphorus in these minerals appears plausible. Parenthetically, there is also considerable overlap in the few published (Henderson 1968; Anderson & Greenland 1969; Thompson 1975; Libourel et al. 1994) or unpublished (Xirouchakis and Draper unpubl. data) partition coefficients for these minerals and mafic silicate liquids. The mechanisms that allow phosphorus to enter the silicate minerals of interest remain unclear or poorly understood, and certainly need to be

  12. Natural Weathering Rates of Silicate Minerals

    NASA Astrophysics Data System (ADS)

    White, A. F.

    2003-12-01

    Silicates constitute more than 90% of the rocks exposed at Earth's land surface (Garrels and Mackenzie, 1971). Most primary minerals comprising these rocks are thermodynamically unstable at surface pressure/temperature conditions and are therefore susceptible to chemical weathering. Such weathering has long been of interest in the natural sciences. Hartt (1853) correctly attributed chemical weathering to "the efficacy of water containing carbonic acid in promoting the decomposition of igneous rocks." Antecedent to the recent interest in the role of vegetation on chemical weathering, Belt (1874) observed that the most intense weathering of rocks in tropical Nicaragua was confined to forested regions. He attributed this effect to "the percolation through rocks of rain water charged with a little acid from decomposing vegetation." Chamberlin (1899) proposed that the enhanced rates of chemical weathering associated with major mountain building episodes in Earth's history resulted in a drawdown of atmospheric CO2 that led to periods of global cooling. Many of the major characteristics of chemical weathering had been described when Merrill (1906) published the groundbreaking volume Rocks, Rock Weathering, and Soils.The major advances since that time, particularly during the last several decades, have centered on understanding the fundamental chemical, hydrologic, and biologic processes that control weathering and in establishing quantitative weathering rates. This research has been driven by the importance of chemical weathering to a number environmentally and economically important issues. Undoubtedly, the most significant aspect of chemical weathering is the breakdown of rocks to form soils, a process that makes life possible on the surface of the Earth. The availability of many soil macronutrients such as magnesium, calcium, potassium, and PO4 is directly related to the rate at which primary minerals weather. Often such nutrient balances are upset by anthropogenic

  13. Evidence for seismogenic fracture of silicic magma.

    PubMed

    Tuffen, Hugh; Smith, Rosanna; Sammonds, Peter R

    2008-05-22

    It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of approximately 600 degrees C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

  14. Trace fossils of Ordovician radiolarian chert and siliceous mudstone in Newfoundland, Canada

    NASA Astrophysics Data System (ADS)

    Kakuwa, Yoshitaka

    2017-08-01

    Ordovician radiolarian chert and siliceous mudstone in Newfoundland are examined to elucidate the development of trace fossils in and on the Early Paleozoic ocean bottom. Chert sedimentation in the Shoal Arm Formation (SAF) is limited to a short interval, but its sedimentation rate is high with few siliciclastic materials. Trace fossils are common in chert in the SAF, but their development is interrupted by frequent anoxic events. The trace fossils are larger than trace fossils in the contemporary chert of other areas. In contrast, trace fossils in the Strong Island Chert (SIC) are moderately-sized to small, with a few sandstone beds interbedded with chert. Those characteristics reflect differences in the sedimentary environments. Rocks of the SIC were deposited in a basinal part of a back-arc basin; whereas, those in the SAF were deposited on a small isolated basin. Red chert or siliceous rocks that underlie grey cherts and siliceous rocks of the SIC and the SAF bear small and simple trace fossils. This is a common feature of ;oceanic red rocks.; Radiolarian chert and siliceous rocks in Newfoundland also showed that trace fossils are widespread by the Middle Ordovician in the deep-sea environment. The Great Ordovician Biodiversification Event is confirmed in the radiolarian siliceous rocks there.

  15. Electrochemistry of lunar rocks

    NASA Technical Reports Server (NTRS)

    Lindstrom, D. J.; Haskin, L. A.

    1979-01-01

    Electrolysis of silicate melts has been shown to be an effective means of producing metals from common silicate materials. No fluxing agents need be added to the melts. From solution in melts of diopside (CaMgSi2O6) composition, the elements Si, Ti, Ni, and Fe have been reduced to their metallic states. Platinum is a satisfactory anode material, but other cathode materials are needed. Electrolysis of compositional analogs of lunar rocks initially produces iron metal at the cathode and oxygen gas at the anode. Utilizing mainly heat and electricity which are readily available from sunlight, direct electrolysis is capable of producing useful metals from common feedstocks without the need for expendable chemicals. This simple process and the products obtained from it deserve further study for use in materials processing in space.

  16. Evolution of trees and mycorrhizal fungi intensifies silicate mineral weathering

    PubMed Central

    Quirk, Joe; Beerling, David J.; Banwart, Steve A.; Kakonyi, Gabriella; Romero-Gonzalez, Maria E.; Leake, Jonathan R.

    2012-01-01

    Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. Preferential hyphal colonization of the calcium silicate-bearing rock, basalt, progressively increased with advancement from arbuscular mycorrhizal (AM) to later, independently evolved ectomycorrhizal (EM) fungi, and from gymnosperm to angiosperm hosts with both fungal groups. This led to ‘trenching’ of silicate mineral surfaces by AM and EM fungi, with EM gymnosperms and angiosperms releasing calcium from basalt at twice the rate of AM gymnosperms. Our findings indicate mycorrhiza-driven weathering may have originated hundreds of millions of years earlier than previously recognized and subsequently intensified with the evolution of trees and mycorrhizas to affect the Earth's long-term CO2 and climate history. PMID:22859556

  17. Talking Rocks.

    ERIC Educational Resources Information Center

    Rice, Dale; Corley, Brenda

    1987-01-01

    Discusses some of the ways that rocks can be used to enhance children's creativity and their interest in science. Suggests the creation of a dramatic production involving rocks. Includes basic information on sedimentary, igneous, and metamorphic rocks. (TW)

  18. Talking Rocks.

    ERIC Educational Resources Information Center

    Rice, Dale; Corley, Brenda

    1987-01-01

    Discusses some of the ways that rocks can be used to enhance children's creativity and their interest in science. Suggests the creation of a dramatic production involving rocks. Includes basic information on sedimentary, igneous, and metamorphic rocks. (TW)

  19. 21 CFR 182.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  20. 21 CFR 582.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  1. 21 CFR 182.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  2. 21 CFR 582.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  3. 21 CFR 582.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  4. 21 CFR 182.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  5. 21 CFR 582.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  6. 21 CFR 182.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  7. 21 CFR 582.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Tricalcium silicate. (a) Product. Tricalcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This substance is generally recognized as safe when used in table salt...

  8. Contrasting siliceous replacement mineralization, east-central Nevada

    SciTech Connect

    Barton, M.D.; Ilchik, R.P. . Dept. of Geosciences); Seedorff, C.E. )

    1993-04-01

    Fine-grained siliceous replacement of carbonate-bearing rocks (jasperoid) occurs in most mineral districts in east-central Nevada. In most of these occurrences, jasperoid contains Au and(or) Ag and little or no base metals, although concentrations and ratios vary significantly. Broadly, two end-members are distinguished: (1) silicification as an intermediate- to late-stage part of complex alteration associated with igneous centers, and (2) jasperoids lacking other associated alteration and having few or no associated igneous rocks. Within this region, siliceous replacements are found with all metallic ([+-] magmatic) suites. No single factor in these occurrences relates the distribution, metal contents, fluid geochemistry, igneous rocks and associated alteration. Summarizing these characteristics: geochemical and fluid inclusion evidence shows that fluids in igneous-related jasperoids can be high-salinity magmatic (Ely), low-salinity magmatic (McCullough Butte), or metoric (Ward). Fluids in igneous-poor systems are low-salinity, exchanged meteoric waters from which a minor magmatic component can not be excluded. At this level of detail, the best predictor of Ag:Au are the district-scale alteration characteristics. Siliceous replacement takes place in many kinds systems and probably requires no more than a cooling, mildly acidic hydrothermal fluid. Metal suites, other fluid characteristics, and geological environment all need to be considered in evaluating the significance of any jasperoid.

  9. Analysis of a Sheet Silicate.

    ERIC Educational Resources Information Center

    Adams, J. M.; Evans, S.

    1980-01-01

    Describes a student project in analytical chemistry using sheet silicates. Provides specific information regarding the use of phlogopite in an experiment to analyze samples for silicon, aluminum, magnesium, iron, potassium, and fluoride. (CS)

  10. Analysis of a Sheet Silicate.

    ERIC Educational Resources Information Center

    Adams, J. M.; Evans, S.

    1980-01-01

    Describes a student project in analytical chemistry using sheet silicates. Provides specific information regarding the use of phlogopite in an experiment to analyze samples for silicon, aluminum, magnesium, iron, potassium, and fluoride. (CS)

  11. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  12. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  13. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 172.410 Section 172.410 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used in food in accordance with...

  14. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  15. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  16. THE BIOCOMPATIBILITY OF MESOPOROUS SILICATES

    PubMed Central

    Hudson, Sarah; Padera, Robert F.; Langer, Robert; Kohane, Daniel S.

    2008-01-01

    Micro- and nano- mesoporous silicate particles are considered potential drug delivery systems because of their ordered pore structures, large surface areas and the ease with which they can be chemically modified. However, few cytotoxicity or biocompatibility studies have been reported, especially when silicates are administered in the quantities necessary to deliver low-potency drugs. The biocompatibility of mesoporous silicates of particle sizes ~ 150 nm, ~ 800 nm and ~ 4 µm and pore sizes of 3 nm, 7 nm and 16 nm respectively are examined here. In vitro, mesoporous silicates showed a significant degree of toxicity at high concentrations with mesothelial cells. Following subcutaneous injection of silicates in rats, the amount of residual material decreased progressively over three months, with good biocompatibility on histology at all time points. In contrast, intra peritoneal and intra venous injections in mice resulted in death or euthanasia. No toxicity was seen with subcutaneous injection of the same particles in mice. Microscopic analysis of the lung tissue of the mice indicates that death may be due to thrombosis. Although local tissue reaction to mesoporous silicates was benign, they caused severe systemic toxicity. This toxicity could be mitigated by modification of the materials. PMID:18675454

  17. Tin in silicate melts

    NASA Astrophysics Data System (ADS)

    Paparoni, Guido

    An experimental technique that uses Re metal capsules as containers for tin-bearing systems has been developed and successfully used in the study of the compositional dependence of SnO2 solubility in silicate melts. These experiments have been performed in the absence of an aqueous fluid phase and oxygen fugacity (fO2) has been established by the addition of tin-metal to SnO2. This approach solves three long-standing problems in the study of SnO 2 solubility in silicate melts: (1) Alloying of noble-metal crucibles and corrosion of ceramic crucibles is avoided; (2) fO 2 is established by direct contact of a metal-oxide oxygen buffer; (3) Gaseous SnO is not lost to the furnace atmosphere. The Re-capsule technique, combined with evacuated silica-tube experiments, has been applied to the study of the system SnO-SiO2 at pressures of 1 atm and 10 kbar. SnO2 solubilities of up to 95 wt% SnO are reported. The system SnO-SiO2 is found to be a pseudo-binary of the ternary system Sn°-SnO2-SiO2. A revised phase diagram for the system SnO-SiO2 at a pressure ≈1 atm is provided, and a new phase diagram for the system SnOSiO2 at a pressure = 10 kbar has been constructed. These results are used to suggest the topology of the ternary system Sn°-SnO2SiO2. The Re-capsule technique has also been applied to the study of the subaluminous haplogranite system (SiO2NaAlSi3O8-KAlSi 3O8) at T = 1100°C, P = 10 kbar and fO 2 at Sn°-SnO2. Solubilities span the range of 41 to 80 wt% SnO. In the haplogranite system, the solubility of SnO2 increases with the proportion of normative SiO2, and SnO is found to expand the stability field of SiO2. In the feldspar join, Na-based melts dissolve a larger proportion of SnO than K-based melts. This effect is lost as SiO2 is progressively added to the feldspar join. Small amounts of F (1 wt%) are found to increase the solubility of SnO 2 by an equivalent 15 wt% normative quartz as shown with the Spor Mountain rhyolite. A comparison of SnO2 solubilities

  18. Thermochemistry of Silicate Speciation in Aqueous Sodium Silicate Solutions: Ionization and Polymerization of Small Silicate Ion

    DTIC Science & Technology

    1993-07-12

    reasonable success, but a number of simplifications were used. For instance, the polymerization equilibrium constants were assumed to be independent of...Another weakness lies in the functionality assumed for the ionization equilibrium constants . As will be discussed below, experimental data that the free...characterize silicate species in fairly complex alkaline silicate solutions and thereby to estimate a large number of equilibrium constants [27,28

  19. Application of direct-fitting, mass integral, and multirate methods to analysis of flowing fluid electric conductivity logs from Horonobe, Japan

    NASA Astrophysics Data System (ADS)

    Doughty, Christine; Tsang, Chin-Fu; Hatanaka, Koichiro; Yabuuchi, Satoshi; Kurikami, Hiroshi

    2008-08-01

    The flowing fluid electric conductivity (FFEC) logging method is an efficient way to provide information on the depths, salinities, and inflow strengths of individual conductive features intercepted by a borehole, without the use of specialized probes. Using it in a multiple-flow rate mode allows, in addition, an estimate of the transmissivities and inherent (far-field) hydraulic heads in each of the conductive features. The multirate method was successfully applied to a 500-m borehole in a granitic formation and reported recently. The present paper describes the application of the method to two zones within a 1000-m borehole in sedimentary rock, which produced, for each zone, three sets of logs at different pumping rates, each set measured over a period of about 1 day. The data sets involve several complications, such as variable well diameter, gradual water level decline in the well during logging, possible fluid flow through the unfractured rock matrix, and effects of drilling mud. Various techniques were applied to analyze the FFEC logs: direct-fitting, mass integral, and the multirate method mentioned above. In spite of complications associated with the tests, analysis was able to identify 44 hydraulically conducting fractures distributed over the depth interval 150-775 m below ground surface. The salinities (in FEC), and transmissivities and hydraulic heads (in dimensionless form) of these 44 features were obtained and found to vary significantly among one another. These results were compared with transmissivity and head values inferred from eight packer tests that were conducted in this borehole over the same depth interval. FFEC results were found to be consistent with packer test results, thus demonstrating the robustness of the FFEC logging method under nonideal conditions.

  20. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    NASA Astrophysics Data System (ADS)

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Flatt, Robert J.; D'Espinose de Lacaillerie, Jean-Baptiste

    2016-03-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured.

  1. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    PubMed Central

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Flatt, Robert J.; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  2. "Rock Garden"

    NASA Image and Video Library

    1997-10-14

    This false color composite image of the Rock Garden shows the rocks "Shark" and "Half Dome" at upper left and middle, respectively. Between these two large rocks is a smaller rock (about 0.20 m wide, 0.10 m high, and 6.33 m from the Lander) that was observed close-up with the Sojourner rover (see PIA00989). http://photojournal.jpl.nasa.gov/catalog/PIA00987

  3. Irreversible phase transitions and wave propagation in silicate geologic materials

    SciTech Connect

    Swegle, J.W. )

    1990-08-15

    Shock and unloading experiments on quartz and silicate rocks indicate that the release adiabats lie below the Hugoniot. The hysteresis and energy dissipation inherent in this situation have important wave propagation implications. On loading, there is a pressure-induced transition to the stishovite phase which does not occur under conditions of thermodynamic equilibrium, in that the Hugoniot passes through a metastable mixed-phase region for several tens of GPa. One interpretation of the unloading data is that the transition is not reversible, and the phase mixture remains frozen on unloading. However, material strength may also play a role. A complete thermodynamically consistent equation of state which includes phase transitions and strength effects has been developed and used to examine shock and release data on quartz and silicate rocks in order to quantify the kinetics of the reverse transition and to separate the hysteretic effects due to reverse phase transition kinetics from those due to material strength. The model allows quantitative determination of the effect of reverse transition kinetics on ground shock propagation in silicate materials.

  4. Irreversible phase transitions and wave propagation in silicate geologic materials

    SciTech Connect

    Swegle, J.W.

    1989-08-01

    Shock and unloading experiments on quartz and silicate rocks indicate that the release adiabats lie below the Hugoniot. The hysteresis and energy dissipation inherent in this situation have important wave propagation implications. On loading, there is a pressure-induced transition to the stishovite phase which is not abrupt, with the Hugoniot passing through a metastable mixed phase region for several tens of GPa. One interpretation of the unloading data is that the transition is not reversible, and the material remains in a frozen phase mixture on initial unloading. However, material strength may also play a role. A complete thermodynamically consistent EOS which includes phase transitions and strength effects has been developed and used to examine shock and release data on quartz and silicate rocks in order to quantify the kinetics of the reverse transition and to separate the hysteretic effects due to phase transition kinetics from those due to material strength. The model also allows quantitative determination of the effect of transition kinetics on ground shock propagation in silicate materials. 51 refs., 46 figs., 3 tabs.

  5. Irreversible phase transition and wave propagation in silicate geologic materials

    SciTech Connect

    Swegle, J.W.

    1989-01-01

    Shock and unloading experiments on quartz and silicate rocks indicate the release adiabats lie below the Hugoniot. The hysteresis and energy dissipation inherent in this situation have important wave propagation implications. On loading, there is pressure-induced transition to the stishovite phase which is not abrupt, with the Hugoniot passing through a metastable mixed phase region for several tens of GPa. One interpretation of the unloading data is that the transition is not reversible, and the material remains in a frozen phase mixture on initial unloading. However, material strength may also play a role. A complete thermodynamically consistent EOS which includes phase transitions and strength effects has been developed and used to examine shock and release data on quartz and silicate rocks in order to quantify the kinetics of the reverse transition and to separate the hysteretic effects due to phase transition kinetics from those due to material strength. The model allows quantitative determination of the effect of transition kinetics on ground shock propagation in silicate materials. 7 refs., 6 figs.

  6. Chemistry of the subalkalic silicic obsidians

    USGS Publications Warehouse

    MacDonald, Ray; Smith, Robert L.; Thomas, John E.

    1992-01-01

    Nonhydrated obsidians are quenched magmatic liquids that record in their chemical compositions details of the tectonic environment of formation and of the differentiation mechanisms that affected their subsequent evolution. This study attempts to analyze, in terms of geologic processes, the compositional variations in the subalkalic silicic obsidians (Si02≥70 percent by weight, molecular (Na2O+K20)>Al2O3). New major- and trace-element determinations of 241 samples and a compilation of 130 published major-element analyses are reported and interpreted. Obsidians from five different tectonic settings are recognized: (1) primitive island arcs, (2) mature island arcs, (3) continental margins, (4) continental interiors, and (5) oceanic extensional zones. Tectonomagmatic discrimination between these groups is successfully made on Nb-Ta, Nb-FeOt and Th-Hf-Ta plots, and compositional ranges and averages for each group are presented. The chemical differences between groups are related to the type of crust in which magmas were generated. With increasingly sialic (continental type) crust, the obsidians show overall enrichment in F, Be, Li, Mo, Nb, Rb, Sn, Ta, U, W, Zn, and the rare-earth elements, and depletion in Mg, Ca, Ba, Co, Sc, Sr, and Zr. They become more potassic, have higher Fe/Mg and F/Cl ratios, and lower Zr/Hf, Nb/Ta, and Th/U ratios. Higher values of total rare-earth elements are accompanied by light rare-earth-element enrichment and pronounced negative Eu anomalies. An attempt is made to link obsidian chemistry to genetic mechanlism. Two broad groups of rocks are distinguished: one generated where crystal-liquid processes dominated (CLPD types), which are the products of crustal anatexis, possibly under conditions of low halogen fugacity, ± crystal fractionation ± magma mixing; and a second group represented by rocks formed in the upper parts of large magma chambers by interplays of crystal fractionation, volatile transfer, magma mixing, and possibly various

  7. Science Rocks!

    ERIC Educational Resources Information Center

    Prestwich, Dorothy; Sumrall, Joseph; Chessin, Debby A.

    2010-01-01

    It all began one Monday morning. Raymond could not wait to come to large group. In his hand, he held a chunk of white granite he had found. "Look at my beautiful rock!" he cried. The rock was passed around and examined by each student. "I wonder how rocks are made?" wondered one student. "Where do they come from?"…

  8. Rock Finding

    ERIC Educational Resources Information Center

    Rommel-Esham, Katie; Constable, Susan D.

    2006-01-01

    In this article, the authors discuss a literature-based activity that helps students discover the importance of making detailed observations. In an inspiring children's classic book, "Everybody Needs a Rock" by Byrd Baylor (1974), the author invites readers to go "rock finding," laying out 10 rules for finding a "perfect" rock. In this way, the…

  9. Rock Art

    ERIC Educational Resources Information Center

    Henn, Cynthia A.

    2004-01-01

    There are many interpretations for the symbols that are seen in rock art, but no decoding key has ever been discovered. This article describes one classroom's experiences with a lesson on rock art--making their rock art and developing their own personal symbols. This lesson allowed for creativity, while giving an opportunity for integration…

  10. Collecting Rocks.

    ERIC Educational Resources Information Center

    Barker, Rachel M.

    One of a series of general interest publications on science topics, the booklet provides those interested in rock collecting with a nontechnical introduction to the subject. Following a section examining the nature and formation of igneous, sedimentary, and metamorphic rocks, the booklet gives suggestions for starting a rock collection and using…

  11. Science Rocks!

    ERIC Educational Resources Information Center

    Prestwich, Dorothy; Sumrall, Joseph; Chessin, Debby A.

    2010-01-01

    It all began one Monday morning. Raymond could not wait to come to large group. In his hand, he held a chunk of white granite he had found. "Look at my beautiful rock!" he cried. The rock was passed around and examined by each student. "I wonder how rocks are made?" wondered one student. "Where do they come from?"…

  12. Rock Art

    ERIC Educational Resources Information Center

    Henn, Cynthia A.

    2004-01-01

    There are many interpretations for the symbols that are seen in rock art, but no decoding key has ever been discovered. This article describes one classroom's experiences with a lesson on rock art--making their rock art and developing their own personal symbols. This lesson allowed for creativity, while giving an opportunity for integration…

  13. Rock Finding

    ERIC Educational Resources Information Center

    Rommel-Esham, Katie; Constable, Susan D.

    2006-01-01

    In this article, the authors discuss a literature-based activity that helps students discover the importance of making detailed observations. In an inspiring children's classic book, "Everybody Needs a Rock" by Byrd Baylor (1974), the author invites readers to go "rock finding," laying out 10 rules for finding a "perfect" rock. In this way, the…

  14. Comparative pathology of silicate pneumoconiosis.

    PubMed Central

    Brambilla, C.; Abraham, J.; Brambilla, E.; Benirschke, K.; Bloor, C.

    1979-01-01

    A simple pneumoconiosis with lamellar birefringent crystals was observed in animals dying in the San Diego Zoo. We studied 100 autopsies from 11 mammalian and eight avian species. In mammals, mild pulmonary lesions comprised crystal-laden macrophages in alveoli and lymphatics. Interstitial fibrosis was present in 20% of cases. There were no nodules. In birds, dust retention produced large granulomas around tertiary bronchi without fibrosis. Mineralogic analysis using scanning and transmission electron microscopy showed most of the crystals to be silicates. Ninety percent were complex silicates, with aluminum-potassium silicates comprising 70% of the analyzed particles. Electron and x-ray diffraction showed the silicates to be muscovite mica and its hydrothermal degradation product, ie, illite clay. This mica was also present on filtration membranes of atmospheric air samples obtained from the San Diego Zoo. The amount of dust retention was related to the animal's age, anatomic or ecologic variances, and length of stay in the San Diego Zoo. Its semidesert atmosphere is rich in silicates, which are inhaled and deposited in the lungs. Similar mica-induced lesions are found in humans living in this region or the Southwest of the USA. This simple pneumoconiosis is likely to be widespread in human populations living in desert or semidesert climates. Images Figure 9 Figure 10 Figure 7 Figure 8 Figure 5 Figure 6 Figure 1 Figure 2 Figure 3 Figure 4 PMID:223447

  15. Uranium-bearing coal and carbonaceous rocks in the Fall Creek area, Bonneville County, Idaho

    USGS Publications Warehouse

    Vine, James D.; Moore, George Winfred

    1952-01-01

    Uraniferous coal, carbonaceous shale, and carbonaceous limestone occur in the Bear River formation of Early Cretaceous age at the Fall Creek prospect, in the Fall Creek area, Bonneville County, Idaho. The uranium compounds are believed to have been derived from mildly radioactive silicic volcanic rocks of Tertiary age that rest unconformably on all older rocks and once overlay the Bear River formation and its coal. Meteoric water, percolating downward through the silicic volcanic rocks and into the older rocks along joints and faults, is believed to have brought the uranium compounds into contact with the coal and carbonaceous rocks in which the uranium was absorbed.

  16. Erosion and the rocks of Venus

    NASA Technical Reports Server (NTRS)

    Sagan, C.

    1976-01-01

    Photographs of the surface of Venus returned by the Venera 9 and 10 spacecraft have revealed the presence of smooth and angular rockline forms. Two mechanisms previously suggested (Sagan, 1975) for erosion of crater ramparts on the surface of Venus might also explain the erosion of rocks. Chemical weathering by the hydrochloric, hydrofluoric, and sulfuric acids present in the atmosphere of Venus may have been sufficient to erode angular projections of silicous rocks. Alternatively, the contours of rocks containing such low-melting materials as NaOH, KOH, HgS and KNO2 may have softened as the result of exposure to the high surface temperatures of the planet.

  17. LOW VELOCITY SHPERE IMPACT OF SODA LIME SILICATE GLASS

    SciTech Connect

    Morrissey, Timothy G; Fox, Ethan E; Wereszczak, Andrew A; Vuono, Daniel J

    2012-01-01

    This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity ( 30 m/s or 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations.

  18. Application of direct-fitting, mass-integral, and multi-ratemethods to analysis of flowing fluid electric conductivity logs fromHoronobe, Japan

    SciTech Connect

    Doughty, C.; Tsang, C.-F.; Hatanaka, K.; Yabuuchi, S.; Kurikami, H.

    2007-08-01

    The flowing fluid electric conductivity (FFEC) loggingmethod is an efficient way to provide information on the depths,salinities, and transmissivities of individual conductive featuresintercepted by a borehole, without the use of specialized probes. Usingit in a multiple-flow-rate mode allows, in addition, an estimate of theinherent "far-field" pressure heads in each of the conductive features.The multi-rate method was successfully applied to a 500-m borehole in agranitic formation and reported recently. The present paper presents theapplication of the method to two zones within a 1000-m borehole insedimentary rock, which produced, for each zone, three sets of logs atdifferent pumping rates, each set measured over a period of about oneday. The data sets involve a number of complications, such as variablewell diameter, free water table decline in the well, and effects ofdrilling mud. To analyze data from this borehole, we apply varioustechniques that have been developed for analyzing FFEC logs:direct-fitting, mass-integral, and the multi-rate method mentioned above.In spite of complications associated with the tests, analysis of the datais able to identify 44 hydraulically conducting fractures distributedover the depth interval 150-775 meters below ground surface. Thesalinities (in FEC), and transmissivities and pressure heads (indimensionless form) of these 44 features are obtained and found to varysignificantly among one another. These results are compared with datafrom eight packer tests with packer intervals of 10-80 m, which wereconducted in this borehole over the same depth interval. They are foundto be consistent with these independent packer-test data, thusdemonstrating the robustness of the FFEC logging method under non-idealconditions.

  19. Final report on the safety assessment of aluminum silicate, calcium silicate, magnesium aluminum silicate, magnesium silicate, magnesium trisilicate, sodium magnesium silicate, zirconium silicate, attapulgite, bentonite, Fuller's earth, hectorite, kaolin, lithium magnesium silicate, lithium magnesium sodium silicate, montmorillonite, pyrophyllite, and zeolite.

    PubMed

    Elmore, Amy R

    2003-01-01

    This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium, and Zirconium Silicates, Magnesium Trisilicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite as used in cosmetic formulations. The common aspect of all these claylike ingredients is that they contain silicon, oxygen, and one or more metals. Many silicates occur naturally and are mined; yet others are produced synthetically. Typical cosmetic uses of silicates include abrasive, opacifying agent, viscosity-increasing agent, anticaking agent, emulsion stabilizer, binder, and suspending agent. Clay silicates (silicates containing water in their structure) primarily function as adsorbents, opacifiers, and viscosity-increasing agents. Pyrophyllite is also used as a colorant. The International Agency for Research on Cancer has ruled Attapulgite fibers >5 microm as possibly carcinogenic to humans, but fibers <5 microm were not classified as to their carcinogenicity to humans. Likewise, Clinoptilolite, Phillipsite, Mordenite, Nonfibrous Japanese Zeolite, and synthetic Zeolites were not classified as to their carcinogenicity to humans. These ingredients are not significantly toxic in oral acute or short-term oral or parenteral toxicity studies in animals. Inhalation toxicity, however, is readily demonstrated in animals. Particle size, fibrogenicity, concentration, and mineral composition had the greatest effect on toxicity. Larger particle size and longer and wider fibers cause more adverse effects. Magnesium Aluminum Silicate was a weak primary skin irritant in rabbits and had no cumulative skin irritation in guinea pigs. No gross effects were reported in any of these studies. Sodium Magnesium Silicate had no primary skin irritation in rabbits and had no cumulative skin irritation in guinea pigs. Hectorite was nonirritating to the skin of rabbits in a Draize primary skin

  20. 'Escher' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Chemical Changes in 'Endurance' Rocks

    [figure removed for brevity, see original site] Figure 1

    This false-color image taken by NASA's Mars Exploration Rover Opportunity shows a rock dubbed 'Escher' on the southwestern slopes of 'Endurance Crater.' Scientists believe the rock's fractures, which divide the surface into polygons, may have been formed by one of several processes. They may have been caused by the impact that created Endurance Crater, or they might have arisen when water leftover from the rock's formation dried up. A third possibility is that much later, after the rock was formed, and after the crater was created, the rock became wet once again, then dried up and developed cracks. Opportunity has spent the last 14 sols investigating Escher, specifically the target dubbed 'Kirchner,' and other similar rocks with its scientific instruments. This image was taken on sol 208 (Aug. 24, 2004) by the rover's panoramic camera, using the 750-, 530- and 430-nanometer filters.

    The graph above shows that rocks located deeper into 'Endurance Crater' are chemically altered to a greater degree than rocks located higher up. This chemical alteration is believed to result from exposure to water.

    Specifically, the graph compares ratios of chemicals between the deep rock dubbed 'Escher,' and the more shallow rock called 'Virginia,' before (red and blue lines) and after (green line) the Mars Exploration Rover Opportunity drilled into the rocks. As the red and blue lines indicate, Escher's levels of chlorine relative to Virginia's went up, and sulfur down, before the rover dug a hole into the rocks. This implies that the surface of Escher has been chemically altered to a greater extent than the surface of Virginia. Scientists are still investigating the role water played in influencing this trend.

    These data were taken by the rover's alpha particle X-ray spectrometer.

  1. 'Escher' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Chemical Changes in 'Endurance' Rocks

    [figure removed for brevity, see original site] Figure 1

    This false-color image taken by NASA's Mars Exploration Rover Opportunity shows a rock dubbed 'Escher' on the southwestern slopes of 'Endurance Crater.' Scientists believe the rock's fractures, which divide the surface into polygons, may have been formed by one of several processes. They may have been caused by the impact that created Endurance Crater, or they might have arisen when water leftover from the rock's formation dried up. A third possibility is that much later, after the rock was formed, and after the crater was created, the rock became wet once again, then dried up and developed cracks. Opportunity has spent the last 14 sols investigating Escher, specifically the target dubbed 'Kirchner,' and other similar rocks with its scientific instruments. This image was taken on sol 208 (Aug. 24, 2004) by the rover's panoramic camera, using the 750-, 530- and 430-nanometer filters.

    The graph above shows that rocks located deeper into 'Endurance Crater' are chemically altered to a greater degree than rocks located higher up. This chemical alteration is believed to result from exposure to water.

    Specifically, the graph compares ratios of chemicals between the deep rock dubbed 'Escher,' and the more shallow rock called 'Virginia,' before (red and blue lines) and after (green line) the Mars Exploration Rover Opportunity drilled into the rocks. As the red and blue lines indicate, Escher's levels of chlorine relative to Virginia's went up, and sulfur down, before the rover dug a hole into the rocks. This implies that the surface of Escher has been chemically altered to a greater extent than the surface of Virginia. Scientists are still investigating the role water played in influencing this trend.

    These data were taken by the rover's alpha particle X-ray spectrometer.

  2. 21 CFR 872.6670 - Silicate protector.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6670 Silicate protector. (a) Identification. A silicate... system regulation in part 820 of this chapter, with the exception of § 820.180, with respect to general...

  3. Battery components employing a silicate binder

    DOEpatents

    Delnick, Frank M [Albuquerque, NM; Reinhardt, Frederick W [Albuquerque, NM; Odinek, Judy G [Rio Rancho, NM

    2011-05-24

    A battery component structure employing inorganic-silicate binders. In some embodiments, casting or coating of components may be performed using aqueous slurries of silicates and electrode materials or separator materials.

  4. Circumstellar Crystalline Silicates: Evolved Stars

    NASA Astrophysics Data System (ADS)

    Tartar, Josh; Speck, A. K.

    2008-05-01

    One of the most exciting developments in astronomy in the last 15 years was the discovery of crystalline silicate stardust by the Short Wavelength Spectrometer (SWS) on board of ISO; discovery of the crystalline grains was indeed one of the biggest surprises of the ISO mission. Initially discovered around AGB stars (evolved stars in the range of 0.8 > M/M¤>8) at far-infrared (IR) wavelengths, crystalline silicates have since been seen in many astrophysical environments including young stellar objects (T Tauri and Herbig Ae/Be), comets and Ultra Luminous Infrared Galaxies. Low and intermediate mass stars (LIMS) comprise 95% of the contributors to the ISM, so study of the formation of crystalline silicates is critical to our understanding of the ISM, which is thought to be primarily amorphous (one would expect an almost exact match between the composition of AGB dust shells and the dust in the ISM). Whether the crystalline dust is merely undetectable or amorphized remains a mystery. The FORCAST instrument on SOFIA as well as the PACS instrument on Herschel will provide exciting observing opportunities for the further study of crystalline silicates.

  5. 'Earhart' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image taken by NASA's Mars Exploration Rover Opportunity shows a rock informally named 'Earhart' on the lower slopes of 'Endurance Crater.' The rock was named after the pilot Amelia Earhart. Like 'Escher' and other rocks dotting the bottom of Endurance, scientists believe fractures in Earhart could have been formed by one of several processes. They may have been caused by the impact that created Endurance Crater, or they might have arisen when water leftover from the rock's formation dried up. A third possibility is that much later, after the rock was formed, and after the crater was created, the rock became wet once again, then dried up and developed cracks. Rover team members do not have plans to investigate Earhart in detail because it is located across potentially hazardous sandy terrain. This image was taken on sol 219 (Sept. 4) by the rover's panoramic camera, using its 750-, 530- and 430-nanometer filters.

  6. Amended Silicated for Mercury Control

    SciTech Connect

    James Butz; Thomas Broderick; Craig Turchi

    2006-12-31

    Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where fly

  7. Apatite: A new redox proxy for silicic magmas?

    NASA Astrophysics Data System (ADS)

    Miles, A. J.; Graham, C. M.; Hawkesworth, C. J.; Gillespie, M. R.; Hinton, R. W.; Bromiley, G. D.

    2014-05-01

    The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this paper we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apatite in granitic rocks from the zoned Criffell granitic pluton (southern Scotland) correlate with decreasing Fe2O3 (Fe3+) and Mn in the whole-rock and likely reflect increased Mn2+/Mn3+ and greater compatibility of Mn2+ relative to Mn3+ in apatite under reduced conditions. Fe3+/Fe2+ ratios in biotites have previously been used to calculate oxygen fugacities (fO2) in the outer zone granodiorites and inner zone granites where redox conditions have been shown to change from close to the magnetite-hematite buffer to close to the nickel-nickel oxide buffer respectively (Stephens et al., 1985). This trend is apparent in apatite Mn concentrations from a range of intermediate to silicic volcanic rocks that exhibit varying redox states and are shown to vary linearly and negatively with log fO2, such that logfO=-0.0022(±0.0003)Mn(ppm)-9.75(±0.46) Variations in the Mn concentration of apatites appear to be largely independent of differences in the Mn concentration of the melt. Apatite Mn concentrations may therefore provide an independent oxybarometer that is amenable to experimental calibration, with major relevance to studies on detrital mineral suites, particularly those containing a record of early Earth redox conditions, and on the climatic impact of historic volcanic eruptions.

  8. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  9. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  10. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  11. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  12. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  13. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  14. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  15. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  16. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions...

  17. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  18. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  19. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  20. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  1. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  2. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  3. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  4. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  5. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  6. Rock flows

    NASA Technical Reports Server (NTRS)

    Matveyev, S. N.

    1986-01-01

    Rock flows are defined as forms of spontaneous mass movements, commonly found in mountainous countries, which have been studied very little. The article considers formations known as rock rivers, rock flows, boulder flows, boulder stria, gravel flows, rock seas, and rubble seas. It describes their genesis as seen from their morphological characteristics and presents a classification of these forms. This classification is based on the difference in the genesis of the rubbly matter and characterizes these forms of mass movement according to their source, drainage, and deposit areas.

  7. Carbonatization effect on basaltic glass and silicate minerals

    NASA Astrophysics Data System (ADS)

    Stockmann, G. J.; Wolff-Boenisch, D.; Gislason, S.; Oelkers, E. H.

    2013-12-01

    Combined silicate dissolution and carbonatization experiments were conducted on basaltic glass and five different silicate minerals (augite, diopside, enstatite, labradorite, olivine) using mixed-flow reactors at 25 and 70°C. The aim of the study was to see if a) dissolving silicates acting as the Ca-source lead to calcium carbonate precipitation in the presence of a carbonate-bearing aqueous solution, b) whether different crystallographical properties of the silicates play a role for how much calcite is precipitating, and finally c) whether carbonate coatings affect the silicate dissolution rates. All experiments were conducted within the context of ';CarbFix', an international CO2 sequestration project in Iceland with the aim to trap CO2 through mineral carbonatization in basaltic rocks. A substantial part of the Icelandic lithology comprises basaltic glass. This glass is rich in divalent cations and easily dissolved compared to basaltic silicate minerals, which makes it interesting for CO2 mineralization efforts. In the crystalline basalt, the dominant minerals are plagioclase (labradorite), clinopyroxene (augite), and Mg-rich olivine, which were therefore chosen for this study. Diopside (cpx) and enstatite (opx) were included because more literature data are available for these pyroxenes than for augite. Basaltic glass proved viable as a Ca-source to form calcium carbonates at pH 8-10 at both 25 and 70°C. However, at 70°C the formation of zeolites competed with the carbonates for the Ca. Both calcite and aragonite were forming and co-existing in the case of basaltic glass. In all other experiments, calcite was the only carbonate phase found. To maximize the effect of carbonate coatings, a mixed-reactor with two inlets was developed; a Ca-bearing and a CO3-bearing. In two different sets of experiments at 25°C the saturation index of calcite in the mixed inlet solution was 1) 0.6 and 2) ~1.8, respectively. The high-saturation experiments 2) were tested on

  8. Effects of ionization on silicate glasses. [Silicate glasses

    SciTech Connect

    Primak, W.

    1982-02-01

    This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures.

  9. Immiscible silicate liquids and phosphoran olivine in Netschaëvo IIE silicate: Analogue for planetesimal core-mantle boundaries

    NASA Astrophysics Data System (ADS)

    Van Roosbroek, Nadia; Hamann, Christopher; McKibbin, Seann; Greshake, Ansgar; Wirth, Richard; Pittarello, Lidia; Hecht, Lutz; Claeys, Philippe; Debaille, Vinciane

    2017-01-01

    We have investigated a piece of the Netschaëvo IIE iron meteorite containing a silicate inclusion by means of electron microprobe analysis (EMPA) and transmission electron microscopy (TEM). Netschaëvo contains chondrule-bearing clasts and impact melt rock clasts were also recently found. The examined inclusion belongs to the latter and is characterized by a porphyritic texture dominated by clusters of coarse-grained olivine and pyroxene, set in a fine-grained groundmass that consists of new crystals of olivine and a hyaline matrix. This matrix material has a quasi-basaltic composition in the inner part of the inclusion, whereas the edge of the inclusion has a lower SiO2 concentration and is enriched in MgO, P2O5, CaO, and FeO. Close to the metal host, the inclusion also contains euhedral Mg-chromite crystals and small (<2 μm), Si-rich globules. A TEM foil was cut from this glassy, silico-phosphate material. It shows that the material consists of elongated olivine crystallites containing up to 14 wt% P2O5, amorphous material, and interstitial Cl-apatite crystals. The Si-rich silicate glass globules show a second population of Fe-rich silicate glass droplets, indicating they formed by silicate liquid immiscibility. Together with the presence of phosphoran olivine and quenched Cl-apatite, these textures suggest rapid cooling and quenching as a consequence of an impact event. Moreover, the enrichment of phosphorus in the silicate inclusion close to the metal host (phosphoran olivine and Cl-apatite) indicates that phosphorus re-partitioned from the metal into the silicate phase upon cooling. This probably also took place in pallasite meteorites that contain late-crystallizing phases rich in phosphorus. Accordingly, our findings suggest that oxidation of phosphorus might be a general process in core-mantle environments, bearing on our understanding of planetesimal evolution. Thus, the Netschaëvo sample serves as a natural planetesimal core-mantle boundary experiment

  10. Microwave dielectric properties of dry rocks

    NASA Technical Reports Server (NTRS)

    Ulaby, Fawwaz T.; Dobson, Myron C.; East, Jack R.; Bengal, Thomas H.; Garvin, James B.; Evans, Diane L.

    1990-01-01

    A combination of techniques was used to measure the dielectric properties of 80 rock samples in the microwave region. The real part (RP) of the relative dielectric constant was measured in 0.1-GHz steps from 0.5 to 18 GHz, and the imaginary part (IP) was measured at five frequencies between 1.6 and 16 GHz. The bulk density rho(b) was also measured for all the samples, and the bulk chemical composition (BCC) was determined for 56 of the samples. RP is found to be frequency-independent at 0.5-18 GHz for all samples, and rho(b) accounts for about 50 percent of the observed variance. For silicate rocks, as much as 78 percent of the variance is explained by the combination of rho(b) and the fractional contents of oxides when the silicates are subgrouped by genesis. In contrast, IP decreases with increasing frequency for most rock samples, and no statistically significant relationships are found between IP and rho(b). For subgrouped silicate rocks, 60 percent of the variance in IP can be explained by BCC.

  11. Cometary Silicates: Interstellar and Nebular Materials

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.

    2002-01-01

    Evidence for interstellar material in comets is deduced from IR spectra, insitu measurements of Halley, and chondritic porous interplanetary dust particles (CP IDPs). IR spectra of comets reveal the spectrally active minerals: amorphous carbon, amorphous silicates, and (in some comets) crystalline silicates. Evidence suggests amorphous silicates are of interstellar origin while crystalline silicates are of nebular origin. 10 microns spectra of comets and submicron amorphous silicate spherules in CP IDPs have shapes similar to lines-of-sight through the ISM. Thermal emission models of cometary IR spectra require Fe-bearing amorphous silicates. Fe-bearing amorphous silicates may be Fe-bearing crystalline silicates formed in AGB outflows that are amorphized through He+ ion bombardment in supernova shocks in the ISM. Crystalline silicates in comets, as revealed by IR spectra, and their apparent absence in the ISM, argues for their nebular origin. The high temperatures (less than l000 K) at which crystals form or are annealed occur in the inner nebula or in nebular shocks in the 5-10 AU region. Oxygen isotope studies of CP IDPs show by mass only 1 % of the silicate crystals are of AGB origin. Together this suggests crystalline silicates in comets are probably primitive grains from the early solar nebula.

  12. Surface characterization of silicate bioceramics.

    PubMed

    Cerruti, Marta

    2012-03-28

    The success of an implanted prosthetic material is determined by the early events occurring at the interface between the material and the body. These events depend on many surface properties, with the main ones including the surface's composition, porosity, roughness, topography, charge, functional groups and exposed area. This review will portray how our understanding of the surface reactivity of silicate bioceramics has emerged and evolved in the past four decades, owing to the adoption of many complementary surface characterization tools. The review is organized in sections dedicated to a specific surface property, each describing how the property influences the body's response to the material, and the tools that have been adopted to analyse it. The final section introduces the techniques that have yet to be applied extensively to silicate bioceramics, and the information that they could provide.

  13. Modifying Silicates for Better Dispersion in Nanocomposites

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi

    2005-01-01

    An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces

  14. Silicate melt metasomatism in the lithospheric mantle beneath SW Poland

    NASA Astrophysics Data System (ADS)

    Puziewicz, Jacek; Matusiak-Małek, Magdalena; Ntaflos, Theodoros; Grégoire, Michel; Kukuła, Anna

    2014-05-01

    The xenoliths of peridotites representing the subcontinental lithospheric mantle (SCLM) beneath SW Poland and adjacent parts of Germany occur in the Cenozoic alkaline volcanic rocks. Our study is based on detailed characterization of xenoliths occurring in 7 locations (Steinberg in Upper Lusatia, Księginki, Pilchowice, Krzeniów, Wilcza Góra, Winna Góra and Lutynia in Lower Silesia). One of the two major lithologies occurring in the xenoliths, which we call the "B" lithology, comprises peridotites (typically harzburgites) with olivine containing from 90.5 to 84.0 mole % of forsterite. The harzburgites contain no clinopyroxene or are poor in that mineral (eg. in Krzeniów the group "B" harzburgites contain < 1 vol. % of the mineral). They exhibit significant variation in orthopyroxene contents, which varies from 25 to 10 vol. %. Some of the xenoliths are more impoverished in orthopyroxene and have dunitic compositions. The ortho- and clinopyroxene exhibit mg# similar to that of olivine, and typically are low aluminous (Al < 0.10 atom pfu in ortho-, and < 0.20 atom pfu in clinopyroxene). The exception are xenoliths from Księginki, which contain pyroxenes characterised by negative correlation between mg# and Al. The REE patterns of both ortho- and clinopyroxene in the group "B" peridotites suggest equilibration with silicate melt. The rocks of "B" lithology were formed due to alkaline silicate melt percolation in the depleted peridotitic protolith. The basaltic melts formed at high pressure are usually undersaturated in both ortho- and clinopyroxene at lower pressures (Kelemen et al. 1992). Because of cooling and dissolution of ortho- and clinopyroxene the melts change their composition and become saturated in one or both of those phases. Experimental results (e.g. Tursack & Liang 2012 and references therein) show that the same refers to alkaline basaltic silicate melts and that its reactive percolation in the peridotitic host leads to decrease of Mg

  15. Longevity of silicate ceramic restorations.

    PubMed

    Beier, Ulrike Stephanie; Dumfahrt, Herbert

    2014-09-01

    The demand for esthetic restorations has resulted in an increased use of dental ceramics as a biocompatible and functionally sufficient alternative to conventional restorative materials. Silicate ceramic restorations are widely used for veneers, inlays, onlays, and crowns in dentistry. Long-term data are of crucial importance to optimize clinical practice. The purpose of the present article is to summarize data of the Innsbruck ceramic evaluation up to 261 months with the focus on longevity and failure characteristics.

  16. Properties of Tricalcium Silicate Sealers.

    PubMed

    Khalil, Issam; Naaman, Alfred; Camilleri, Josette

    2016-10-01

    Sealers based on tricalcium silicate cement aim at an interaction of the sealer with the root canal wall, alkalinity with potential antimicrobial activity, and the ability to set in a wet field. The aim of this study was to characterize and investigate the properties of a new tricalcium silicate-based sealer and verify its compliance to ISO 6876 (2012). A new tricalcium silicate-based sealer (Bio MM; St Joseph University, Beirut, Lebanon), BioRoot RCS (Septodont, St Maure de Fosses, France), and AH Plus (Dentsply, DeTrey, Konstanz, Germany) were investigated. Characterization using scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis was performed. Furthermore, sealer setting time, flow, film thickness, and radiopacity were performed following ISO specifications. pH and ion leaching in solution were assessed by pH analysis and inductively coupled plasma. Bio MM and BioRoot RCS were both composed of tricalcium silicate and tantalum oxide in Bio MM and zirconium oxide in BioRoot RCS. In addition, the Bio MM contained calcium carbonate and a phosphate phase. The inorganic components of AH Plus were calcium tungstate and zirconium oxide. AH Plus complied with the ISO norms for both flow and film thickness. BioRoot RCS and Bio MM exhibited a lower flow and a higher film thickness than that specified for sealer cements in ISO 6876. All test sealers exhibited adequate radiopacity. Bio MM interacted with physiologic solution, thus showing potential for bioactivity. Sealer properties were acceptable and comparable with other sealers available clinically. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  17. Apatite: a new redox proxy for silicic magmas?

    NASA Astrophysics Data System (ADS)

    Miles, Andrew; Graham, Colin; Hawkesworth, Chris; Gillespie, Martin; Bromiley, Geoff; Hinton, Richard

    2015-04-01

    The oxidation states of magmas provide valuable information about the release and speciation of volatile elements during volcanic eruptions, metallogenesis, source rock compositions, open system magmatic processes, tectonic settings and potentially titanium (Ti) activity in chemical systems used for Ti-dependent geothermometers and geobarometers. In this presentation we explore the use of Mn in apatite as an oxybarometer in intermediate and silicic igneous rocks. Increased Mn concentrations in apatite in granitic rocks from the zoned Criffell granitic pluton (southern Scotland) correlate with decreasing Fe2O3 (Fe3+) and Mn in the whole-rock and likely reflect increased Mn2+/Mn3+and greater compatibility of Mn2+ relative to Mn3+ in apatite under reduced conditions. Fe3+/Fe2+ ratios in biotites have previously been used to calculate oxygen fugacities (fO2) in the outer zone granodiorites and inner zone granites where redox conditions have been shown to change from close to the magnetite-hematite buffer to close to the nickel-nickel oxide buffer respectively[1]. This trend is apparent in apatite Mn concentrations from a range of intermediate to silicic volcanic rocks that exhibit varying redox states and are shown to vary linearly and negatively with log fO2, such that logfO2=-0.0022(±0.0003)Mn(ppm)-9.75(±0.46) Variations in the Mn concentration of apatites appear to be largely independent of differences in the Mn concentration of the melt. Apatite Mn concentrations may therefore provide an independent oxybarometer that is amenable to experimental calibration, with major relevance to studies on detrital mineral suites, particularly those containing a record of early Earth redox conditions, and on the climatic impact of historic volcanic eruptions[2]. [1] Stephens, W. E., Whitley, J. E., Thirlwall, M. F. and Halliday, A. N. (1985) The Criffell zoned pluton: correlated behaviour of rare earth element abundances with isotopic systems. Contributions to Mineralogy and

  18. Art Rocks with Rock Art!

    ERIC Educational Resources Information Center

    Bickett, Marianne

    2011-01-01

    This article discusses rock art which was the very first "art." Rock art, such as the images created on the stone surfaces of the caves of Lascaux and Altimira, is the true origin of the canvas, paintbrush, and painting media. For there, within caverns deep in the earth, the first artists mixed animal fat, urine, and saliva with powdered minerals…

  19. Art Rocks with Rock Art!

    ERIC Educational Resources Information Center

    Bickett, Marianne

    2011-01-01

    This article discusses rock art which was the very first "art." Rock art, such as the images created on the stone surfaces of the caves of Lascaux and Altimira, is the true origin of the canvas, paintbrush, and painting media. For there, within caverns deep in the earth, the first artists mixed animal fat, urine, and saliva with powdered minerals…

  20. Carbonate-silicate liquid immiscibility in the mantle propels kimberlite magma ascent

    NASA Astrophysics Data System (ADS)

    Kamenetsky, Vadim S.; Yaxley, Gregory M.

    2015-06-01

    Kimberlite is a rare volcanic rock renowned as the major host of diamonds and originated at the base of the subcontinental lithospheric mantle. Although kimberlite magmas are dense in crystals and deeply-derived rock fragments, they ascend to the surface extremely rapidly, enabling diamonds to survive. The unique physical properties of kimberlite magmas depend on the specific compositions of their parental melts that, in absence of historical eruptions and due to pervasive alteration of kimberlite rocks, remain highly debatable. We explain exceptionally rapid ascent of kimberlite magma from mantle depths by combining empirical data on the essentially carbonatite composition of the kimberlite primary melts and experimental evidence on interaction of the carbonate liquids with mantle minerals. Our experimental study shows that orthopyroxene is completely dissolved in a Na2CO3 melt at 2.0-5.0 GPa and 1000-1200 °C. The dissolution of orthopyroxene results in homogeneous silicate-carbonate melt at 5.0 GPa and 1200 °C, and is followed by unmixing of carbonate and carbonated silicate melts and formation of stable magmatic emulsion at lower pressures and temperatures. The dispersed silicate melt has a significant capacity for storing a carbonate component in the deep mantle (13 wt% CO2 at 2.0 GPa). We envisage that this component reaches saturation and is gradually released as CO2 bubbles, as the silicate melt globules are transported upwards through the lithosphere by the carbonatite magma. The globules of unmixed, CO2-rich silicate melt are continuously produced upon further reaction between the natrocarbonatite melt and mantle peridotite. On decompression the dispersed silicate melt phase ensures a continuous supply of CO2 bubbles that decrease density and increase buoyancy and promote rapid ascent of the magmatic emulsion.

  1. Terby's Rocks

    NASA Technical Reports Server (NTRS)

    2006-01-01

    27 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the light-toned, layered, sedimentary rock outcrops in northern Terby Crater. Terby is located along the north edge of Hellas Planitia. The sedimentary rocks might have been deposited in a greater, Hellas-filling sea -- or not. Today, the rocks are partly covered by dark-toned sediment and debris.

    Location near: 27.2oS, 285.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  2. Opportunity Rocks!

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This high-resolution image captured by the Mars Exploration Rover Opportunity's panoramic camera shows in superb detail a portion of the puzzling rock outcropping that scientists are eagerly planning to investigate. Presently, Opportunity is on its lander facing northeast; the outcropping lies to the northwest. These layered rocks measure only 10 centimeters (4 inches) tall and are thought to be either volcanic ash deposits or sediments carried by water or wind. The small rock in the center is about the size of a golf ball.

  3. A Quantitative Geochemical, Mineralogical and Physical Study of Some Selected Rock Weathering Profiles from Brazil

    DTIC Science & Technology

    1977-08-17

    weather to gibbsite (plus or minus iron oxides) in well-drained, and smectite in poorly-drained, environments. Kaolinite found in the vicinity of quartz...rock and completely weathered saprolite. Quartz-rich rock types exhibit wide, gradational weathered zones and usually form kaolinite or halloysite in...free rocks is either formed by re-silication of gibbsite , or is of secondary origin (transported). Texture of the rock (aphanitic vs. phaneric) has

  4. Dehydroxylated clay silicates on Mars: Riddles about the Martian regolith solved with ferrian saponites

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.

    1992-01-01

    Clay silicates, resulting from the chemical weathering of volcanic glasses and basaltic rocks of Mars, are generally believed to be major constituents of the martian regolith and atmospheric dust. Because little attention has been given to the role, if any, of Mg-bearing clay silicates on the martian surface, the crystal chemistry, stability, and reactivity of Mg-Fe smectites are examined. Partially dehydroxylated ferrian saponites are suggested to be major constituents of the surface of Mars, regulating several properties of the regolith.

  5. Dehydroxylated clay silicates on Mars: Riddles about the Martian regolith solved with ferrian saponites

    NASA Technical Reports Server (NTRS)

    Burns, Roger G.

    1992-01-01

    Clay silicates, resulting from the chemical weathering of volcanic glasses and basaltic rocks of Mars, are generally believed to be major constituents of the martian regolith and atmospheric dust. Because little attention has been given to the role, if any, of Mg-bearing clay silicates on the martian surface, the crystal chemistry, stability, and reactivity of Mg-Fe smectites are examined. Partially dehydroxylated ferrian saponites are suggested to be major constituents of the surface of Mars, regulating several properties of the regolith.

  6. White Rock

    NASA Image and Video Library

    2002-05-21

    White Rock is the unofficial name for this unusual landform which was first observed during NASA Mariner 9 mission in the early 1970 and is now shown here in an image from NASA Mars Odyssey spacecraft.

  7. Rock Garden

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This false color composite image of the Rock Garden shows the rocks 'Shark' and 'Half Dome' at upper left and middle, respectively. Between these two large rocks is a smaller rock (about 0.20 m wide, 0.10 m high, and 6.33 m from the Lander) that was observed close-up with the Sojourner rover (see PIA00989).

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  8. 'Lutefisk' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1

    NASA's Mars Exploration Rover Spirit used its panoramic camera to take this image of a rock called 'Lutefisk' on the rover's 286th martian day (Oct. 22, 2004). The surface of the rock is studded with rounded granules of apparently more-resistant material up to several millimeters (0.1 inch) or more across. The visible portion of Lutefisk is about 25 centimeters (10 inches) across.

  9. Scenario of Growing Crops on Silicates in Lunar Gargens

    NASA Astrophysics Data System (ADS)

    Kozyrovska, N.; Kovalchuk, M.; Negutska, V.; Lar, O.; Korniichuk, O.; Alpatov, A.; Rogutskiy, I.; Kordyum, V.; Foing, B.

    Self-perpetuating gardens will be a practical necessity for humans, living in permanently manned lunar bases. A lunar garden has to supplement less appetizing packaged food brought from the Earth, and the ornamental plants have to serve as valuable means for emotional relaxation of crews in a hostile lunar environment. The plants are less prone to the inevitable pests and diseases when they are in optimum condition, however, in lunar greenhouses there is a threat for plants to be hosts for pests and predators. Although the lunar rocks are microorganism free, there will be a problem with the acquired infection (pathogens brought from the Earth) in the substrate used for the plant growing. On the Moon pests can be removed by total fumigation, including seed fumigation. However, such a treatment is not required when probiotics (biocontrol bacteria) for seed inoculation are used. A consortium of bacteria, controlling plant diseases, provides the production of an acceptable harvest under growth limiting factors and a threatening infection. To model lunar conditions we have used terrestrial alumino-silicate mineral anorthosite (Malyn, Ukraine) which served us as a lunar mineral analog for a substrate composition. With the idea to provide a plant with some essential growth elements siliceous bacterium Paenibacillus sp. has been isolated from alumino-silicate mineral, and a mineral leaching has been simulated in laboratory condition. The combination of mineral anorthosite and siliceous bacteria, on one hand, and a consortium of beneficial bacteria for biocontrol of plant diseases, on the other hand, are currently used in model experiments to examine the wheat and potato growth and production in cultivating chambers under controlled conditions.

  10. Combined effect of carbonate and biotite dissolution in landslides biases silicate weathering proxies

    NASA Astrophysics Data System (ADS)

    Emberson, R.; Galy, A.; Hovius, N.

    2017-09-01

    Long-term estimates of the dissolution of silicate rock are generally derived from a range of isotopic proxies, such as the radiogenic strontium isotope ratio (87Sr/86Sr), which are preserved in sediment archives. For these systems to fairly represent silicate weathering, the changes in isotopic ratios in terrestrial surface waters should correspond to changes in the overall silicate dissolution. This assumes that the silicate mineral phases that act as sources of a given isotope dissolve at a rate that is proportional to the overall silicate weathering. Bedrock landsliding exhumes large quantities of fresh rock for weathering in transient storage, and rapid weathering in these deposits is controlled primarily by dissolution of the most reactive phases. In this study, we test the hypothesis that preferential weathering of these labile minerals can decouple the dissolution of strontium sources from the actual silicate weathering rates in the rapidly eroding Western Southern Alps (WSA) of New Zealand. We find that rapid dissolution of relatively radiogenic calcite and biotite in landslides leads to high local fluxes in strontium with isotopic ratios that offer no clear discrimination between sources. These higher fluxes of radiogenic strontium are in contrast to silicate weathering rates in landslides that are not systematically elevated. On a mountain belt scale, radiogenic strontium fluxes are not coupled to volumes of recent landslides in large (>100 km2) catchments, but silicate weathering fluxes are. Such decoupling is likely due first to the broad variability in the strontium content of carbonate minerals, and second to the combination of radiogenic strontium released from both biotite and carbonate in recent landslides. This study supports previous work suggesting the limited utility of strontium isotopes as a system to study silicate weathering in the WSA. Crucially however, in settings where bedrock landsliding is a dominant erosive process there is

  11. Adsorption kinetics of silicic acid on akaganeite.

    PubMed

    Naren, Gaowa; Ohashi, Hironori; Okaue, Yoshihiro; Yokoyama, Takushi

    2013-06-01

    As part of a series of studies on the interaction between ferric ions and silicic acid in the hydrosphere, the adsorption of silicic acid on akaganeite was investigated kinetically at various pH values. The adsorption of silicic acid increased with increasing pH over an initial pH range of 4-11.5. In the kinetic experiment, the Cl(-) was released from akaganeite much faster than silicic acid was adsorbed. From this result, we concluded that chloride ions bound on the surface of akaganeite are released and Fe-OH or Fe-O(-) sites are formed, which then acts as an adsorption site for silicic acid. The uptake mechanism of silicic acid by akaganeite is significantly different from that by schwertmannite, despite the presence of the same tunnel structure.

  12. The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs

    NASA Astrophysics Data System (ADS)

    Schoenberg, Ronny; Merdian, Alexandra; Holmden, Chris; Kleinhanns, Ilka C.; Haßler, Kathrin; Wille, Martin; Reitter, Elmar

    2016-06-01

    The depletion of chromium in Earth's mantle (∼2700 ppm) in comparison to chondrites (∼4400 ppm) indicates significant incorporation of chromium into the core during our planet's metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions - expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) - of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of -0.124 ± 0.101‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth's silicate reservoirs. Further and more detailed studies are required to investigate whether silicate

  13. Thermodynamics of rock forming crystalline solutions

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1971-01-01

    Analysis of phase diagrams and cation distributions within crystalline solutions as means of obtaining thermodynamic data on rock forming crystalline solutions is discussed along with some aspects of partitioning of elements in coexisting phases. Crystalline solutions, components in a silicate mineral, and chemical potentials of these components were defined. Examples were given for calculating thermodynamic mixing functions in the CaW04-SrW04, olivine-chloride solution, and orthopyroxene systems.

  14. Silicate stabilization studies in propylene glycol

    SciTech Connect

    Schwartz, S.A.

    1999-08-01

    In most North American and many European coolant formulations, the corrosion inhibition of heat-rejecting aluminum surfaces is provided by alkali metal silicates. But, their tendency towards polymerization, leading to gelation and/or precipitation, can reduce the effectiveness of a coolant. This paper presents the results of experiments which illustrate formulation-dependent behavior of inorganic silicate in propylene glycol compositions. Specific examples of the effects of glycol matrix, stabilizer type, and hard water on silicate stabilization are provided.

  15. Getting lunar ilmenite: From soils or rocks

    SciTech Connect

    Vaniman, D.T.; Heiken, G.H.

    1989-01-01

    Lunar soils or rocks can be mined as sources of ilmenite for producing oxygen. However, separable crystals of loose ilmenite in lunar soils are rare (<2%) and small (<200 {mu}); most ilmenite in the regolith is locked together with silicate minerals as rock fragments. Since fragmentation of rock sources must be attempted to win appreciable amounts of ilmenite ({approximately}10% or more), selective collection of high-Ti basalt fragments larger than 1 cm for fragmentation and ilmenite beneficiation may be advantageous over extensive processing of fine lunar soil. Many alternative processing schemes for fragmenting rocks on the Moon have been proposed; one process which was tested early in the Apollo program successfully disaggregated lunar and terrestrial basalts by passive exposure to low-pressure alkali (K) vapor. This process is worthy of reinvestigation. 14 refs., 3 figs.

  16. Flowing fluid electric conductivity logging for a deep artesian well in fractured rock with regional flow

    NASA Astrophysics Data System (ADS)

    Doughty, Christine; Tsang, Chin-Fu; Yabuuchi, Satoshi; Kunimaru, Takanori

    2013-03-01

    SummaryThe flowing fluid electric conductivity (FFEC) logging method is a well-logging technique that may be used to estimate flow rate, salinity, transmissivity, and hydraulic head of individual fractures or high-permeability zones intersected by a wellbore. Wellbore fluid is first replaced with fluid of a contrasting electric conductivity, then repeated FEC logging is done while the well is pumped. Zones where fluid flows into the wellbore show peaks in the FEC logs, which may be analyzed to infer inflow rate and salinity of the individual fractures. Conducting the procedure with two or more pumping rates (multi-rate FFEC logging) enables individual fracture transmissivity and hydraulic head to be determined. Here we describe the first application of the multi-rate FFEC logging method to an artesian well, using a 500-m well in fractured rock at Horonobe, Japan. An additional new factor at the site is the presence of regional groundwater flow, which heretofore has only been studied with synthetic data. FFEC logging was conducted for two different pumping rates. Several analysis techniques had to be adapted to account for the artesian nature of the well. The results were subsequently compared with independent salinity measurements and transmissivity and hydraulic head values obtained from packer tests in the same well. Despite non-ideal operating conditions, multi-rate FFEC logging successfully determined flow rate, salinity, and transmissivity of 17 conducting fractures intercepted by the logged section of the borehole, including two fractures with regional groundwater flow. Predictions of hydraulic head were less accurate, a not unexpected result in light of operational problems and the form of the equation for hydraulic head, which involves the difference between two uncertain quantities. This study illustrates the strengths and weaknesses of the multi-rate FFEC logging method applied to artesian wells. In conjunction with previous studies, it demonstrates the

  17. A review of bioactive silicate ceramics.

    PubMed

    Wu, Chengtie; Chang, Jiang

    2013-06-01

    Silicate bioceramics, as a new family of biomaterials, have received significant attention in their application to hard tissue regeneration. Some silicate bioceramics have shown excellent apatite mineralization in simulated body fluids and their ionic products have been shown to enhance the proliferation, osteogenic differentiation and gene expression of stem cells. In this paper, we review the advances in the research of silicate system bioceramics, including preparation methods, mechanical strength, apatite mineralization, dissolution and in vitro and in vivo biological properties. The biological properties and the corresponding mechanism have been highlighted. A look forward to the application of silicate bioceramics to bone regeneration is further suggested.

  18. Tailoring polymer properties with layered silicates

    NASA Astrophysics Data System (ADS)

    Xu, Liang

    Polymer layered silicate nanocomposites have found widespread applications in areas such as plastics, oil and gas production, biomedical, automotive and information storage, but their successful commercialization critically depends on consistent control over issues such as complete dispersion of layered silicate into the host polymer and optimal interaction between the layered silicates and the polymers. Polypropylene is a commercially important polymer but usually forms intercalated structures with organically modified layered silicate upon mixing, even it is pre-treated with compatibilizing agent such as maleic anhydride. In this work, layered silicate is well dispersed in ammonium modified polypropylene but does not provide sufficient reinforcement to the host polymer due to poor interactions. On the other hand, interactions between maleic anhydride modified polypropylene and layered silicate are fine tuned by using a small amount of maleic anhydride and mechanical strength of the resultant nanocomposites are significantly enhanced. In particular, the melt rheological properties of layered silicate nanocomposites with maleic anhydride functionalized polypropylene are contrasted to those based on ammonium-terminated polypropylene. While the maleic anhydride treated polypropylene based nanocomposites exhibit solid-like linear dynamic behavior, consistent with the formation of a long-lived percolated nanoparticle network, the single-end ammonium functionalized polypropylene based nanocomposites demonstrated liquid-like behavior at comparable montmorillonite concentrations. The differences in the linear viscoelasticity are attributed to the presence of bridging interaction in maleic anhydride functionalized nanocomposites, which facilitates formation of a long-lived silicate network mediated by physisorbed polymer chains. Further, the transient shear stress of the maleic anhydride functionalized nanocomposites in start-up of steady shear is a function of the shear

  19. Thermal-infrared spectra and chemical analyses of twenty-six igneous rock samples

    USGS Publications Warehouse

    Vincent, R.K.; Rowan, L.C.; Gillespie, R.E.; Knapp, C.

    1975-01-01

    Emittance spectra in the 7.5 ??m to 14 ??m wavelength region and chemical compositions of 26 igneous rocks are reported. Experimental measurements on the rocks were made under simulated daytime field conditions. Some surface silicate contaminants, such as clayey silt, significantly altered the spectral emittance of a fresh sample, whereas, for these samples, hydrous and anhydrous ferric oxide weathering products did not mask important silicate spectral information. In the 11.75 ??m to 13.75 ??m wavelength region, the mean emittance of all the silicate samples was 0.956 ?? 0.008, except for periodtite, which had an average emittance of 0.895. This region of uniform emittance should be useful in remote sensing experiments for the separation of the effects of temperature and chemical composition on the spectral emittance of silicate rocks. ?? 1976.

  20. Calc-silicate assemblages from the Kerala Khondalite Belt, southern India: implications for pressure-temperature-fluid histories

    NASA Astrophysics Data System (ADS)

    Satish-Kumar, M.; Santosh, M.; Harley, S. L.; Yoshida, M.

    This paper reports several new localities of wollastonite- and scapolite-bearing calc-silicate assemblages from the granulite-facies supracrustal Kerala Khondalite Belt (KKB), southern India. Based on mineralogy, these calc-silicate rocks are classified into four types: Type I, lacking wollastonite and grossular; Type II, wollastonite-bearing but grossular-absent; Type III, wollastonite- and grossular-bearing; and Type IV, dolomitic marbles. Detailed petrographic studies reveal a variety of reaction textures overprinting the polygonal granoblastic peak metamorphic assemblages in these rocks. The Type II calc-silicate rocks preserve reaction textures, including meionite breaking down to anorthite-calcite-quartz, wollastonite breaking down to calcite-quartz and meionite-quartz symplectites after K-feldspar and wollastonite. Type III calc-silicate rocks have porphyroblastic and coronal grossular. Grossular-quartz coronas separating wollastonite and anorthite and the development of grossular within the anorthite-calcite-quartz pseudomorphs of meionite form important retrograde reaction textures in this type. In Type IV dolomitic marble assemblages, meionite forming in grain boundaries of calcite and feldspars, forsterite rimmed by diopside-dolomite and the formation of grossular in feldspar-rich zones are the important textures. Calculated partial petrogenetic grids in the CaOAl 2O 3SiO 2CO 2 system are used to deduce the pressure-temperature-fluid evolution of the calc-silicate rocks. The Type II assemblages provide CO 2 activity estimates of > 0.5, with a peak metamorphic temperature of about 790°C. Initial cooling followed by later CO 2 influx can be deduced from reaction modelling in these calc-silicate rocks. Type III assemblages are characterized by internal fluid buffering throughout their tectonic history. The formation of coronal grossular indicates an initial cooling from peak metamorphic temperatures of about 830°C deduced from vapour

  1. 'Wopmay' Rock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This approximate true-color image taken by NASA's Mars Exploration Rover Opportunity shows an unusual, lumpy rock informally named 'Wopmay' on the lower slopes of 'Endurance Crater.' The rock was named after the Canadian bush pilot Wilfrid Reid 'Wop' May. Like 'Escher' and other rocks dotting the bottom of Endurance, scientists believe the lumps in Wopmay may be related to cracking and alteration processes, possibly caused by exposure to water. The area between intersecting sets of cracks eroded in a way that created the lumpy appearance. Rover team members plan to drive Opportunity over to Wopmay for a closer look in coming sols. This image was taken by the rover's panoramic camera on sol 248 (Oct. 4, 2004), using its 750-, 530- and 480-nanometer filters.

  2. Evidence for the reversal of gradients in the uppermost parts of silicic magma reservoirs

    USGS Publications Warehouse

    Duffield, W.A.; Ruiz, J.

    1992-01-01

    Evidence from large-volume ignimbrites indicates that the source-magma reservoirs for most of these voluminous silicic pyroclastic deposits contained monotonic vertical chemical gradients at the time of eruption. However, gradients from a large-volume magma reservoir that produced a group of penecontemporaneous silicic lava domes, but no ignimbrite, show a reversal of the usual ignimbrite pattern. This reversal originated by modification of the usual pattern through minor assimilation of partially melted roof rocks. Eruptions that produced these domes apparently just tapped the uppermost part of their source reservoir. They thereby provide a high-resolution instantaneous view of this variably contaminated part of the magma system. The long-standing paradigm for monotonic zoning in large-volume reservoirs of silicic magma may require modification. -from Authors

  3. Volcanic rock petrochemistry as an exploration technique for geothermal energy

    SciTech Connect

    Fultz, L.A.; Bell, E.J.; Trexler, D.T.

    1983-12-01

    Large high-level silicic magma chambers offer a high potential for economically viable geothermal systems. While purely basic volcanic systems rarely form thermal anomalies, they may provide the necessary long-term heat input to silicic systems, by underplating, to sustain a high-temperature geothermal system. Petrographic and microprobe, geochemical, geochronologic, and isotopic data on young volcanic rocks in west-central Nevada indicate compositions that may result from magmatic differentiation, crystal fractionation, variation in magmatic source regions and in particular, magma mixing. Analysis of the petrochemistry and the recognition of magma mixing textures of extrusive rocks may indicate interacting mafic magma with buried shallow silicic magma systems. These systems may provide a shallow heat source for development of geothermal resources.

  4. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2437 Magnesium silicate. (a) Product. Magnesium...

  5. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2227 Calcium silicate. (a) Product. Calcium...

  6. Classic Rock

    ERIC Educational Resources Information Center

    Beem, Edgar Allen

    2004-01-01

    While "early college" programs designed for high-school-age students are beginning to proliferate nationwide, a small New England school has been successfully educating teens for nearly four decades. In this article, the author features Simon's Rock, a small liberal arts college located in the Great Barrington, Massachusetts, that has…

  7. Chemical Variation of Silicate Mineral Phases in Lunar Feldspathic Granulitic Impactites: Implications for Thermal Histories and Provenances

    NASA Technical Reports Server (NTRS)

    Fincke, E. M.; Ryder, G.

    2001-01-01

    We report on the internal variation and abundances of minor elements of silicate phases in lunar granulitic impactites to assess their thermal histories and the pre-metamorphic provenances of the minerals and the process that assembled the rocks. Additional information is contained in the original extended abstract.

  8. Comment on "Apatite: A new redox proxy for silicic magmas?" [Geochimica et Cosmochimica Acta 132 (2014) 101-119

    NASA Astrophysics Data System (ADS)

    Marks, Michael A. W.; Scharrer, Manuel; Ladenburger, Sara; Markl, Gregor

    2016-06-01

    Recently Miles et al. (2014) proposed that a negative correlation between oxygen fugacity (expressed as logfO2 and the Mn content of apatite from a range of intermediate to silicic igneous rocks could be used as an oxybarometer (Eq. (1)).

  9. Chemical Variation of Silicate Mineral Phases in Lunar Feldspathic Granulitic Impactites: Implications for Thermal Histories and Provenances

    NASA Technical Reports Server (NTRS)

    Fincke, E. M.; Ryder, G.

    2001-01-01

    We report on the internal variation and abundances of minor elements of silicate phases in lunar granulitic impactites to assess their thermal histories and the pre-metamorphic provenances of the minerals and the process that assembled the rocks. Additional information is contained in the original extended abstract.

  10. The importance of the Maillard-metal complexes and their silicates in astrobiology

    NASA Astrophysics Data System (ADS)

    Liesch, Patrick J.; Kolb, Vera M.

    2007-09-01

    The Maillard reaction occurs when sugars and amino acids are mixed together in the solid state or in the aqueous solution. Since both amino acids and sugar-like compounds are found on meteorites, we hypothesized that they would also undergo the Maillard reaction. Our recent work supports this idea. We have shown previously that the water-insoluble Maillard products have substantial similarities with the insoluble organic materials from the meteorites. The Maillard organic materials are also part of the desert varnish on Earth, which is a dark, shiny, hard rock coating that contains iron and manganese and is glazed in silicate. Rocks that are similar in appearance to the desert varnish have been observed on the Martian surface. They may also contain the organic materials. We have undertaken study of the interactions between the Maillard products, iron and other metals, and silicates, to elucidate the role of the Maillard products in the chemistry of desert varnish and meteorites. Specifically, we have synthesized a series of the Maillard-metal complexes, and have tested their reactivity towards silicates. We have studied the properties of these Maillard-metal-silicate products by the IR spectroscopy. The astrobiological potential of the Maillard-metal complexes is assessed.

  11. Mesoporous Silicate Materials in Sensing

    PubMed Central

    Melde, Brian J.; Johnson, Brandy J.; Charles, Paul T.

    2008-01-01

    Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through co-condensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules. PMID:27873810

  12. Tectonic and climatic controls on long-term silicate weathering in Asia since 5 Ma

    NASA Astrophysics Data System (ADS)

    Wan, Shiming; Clift, Peter D.; Li, Anchun; Yu, Zhaojie; Li, Tiegang; Hu, Dengke

    2012-08-01

    Determining the interplay between tectonic deformation, climate, atmospheric CO2 concentrations and continental weathering and erosion is key to understanding the mechanisms that forced Cenozoic global cooling. In contrast with studies of paleo-climate and pCO2, the history of long-term silicate weathering in the Himalaya and Tibetan Plateau (HTP) during the late Cenozoic remains unclear. We reconstruct 5 m.y. of silicate sedimentary records at Ocean Drilling Program (ODP) Site 1143 in the South China Sea to explore the weathering history of the Mekong River basin that supplied the sediment. Coherent variation of weathering proxies from the South China Sea, Bay of Bengal, Loess Plateau, as well as the Yangtze and Yellow Rivers, indicates weakening chemical weathering intensity since the late Pliocene, as the climate cooled. This cooling, coupled with tectonic activity, shifted the dominant weathering regime from more transport-limited to more weathering-limited, causing less chemical depletion of silicate minerals. While silicate weathering rates became strongly correlated to erosion rates, they were decoupled from chemical weathering intensity. Physical denudation and associated silicate weathering rates in the HTP area increased in the Pliocene, driven by both rock uplift and stronger monsoon precipitation, decreasing atmospheric CO2 concentrations, and so contributing to Northern Hemisphere Glaciation (NHG).

  13. Tectonic and climatic controls on long-term silicate weathering in Asia since 5 Ma

    NASA Astrophysics Data System (ADS)

    Wan, S.; Clift, P. D.; Li, A.; Yu, Z.; Li, T.; Hu, D.

    2012-12-01

    Determining the interplay between tectonic deformation, climate, atmospheric CO2 concentrations and continental weathering and erosion is key to understanding the mechanisms that forced Cenozoic global cooling. In contrast with studies of paleo-climate and pCO2, the history of long-term silicate weathering in the Himalaya and Tibetan Plateau (HTP) during the late Cenozoic remains unclear. We reconstruct 5 m.y. of silicate sedimentary records at Ocean Drilling Program (ODP) Site 1143 in the South China Sea to explore the weathering history of the Mekong River basin that supplied the sediment. Coherent variation of weathering proxies from the South China Sea, Bay of Bengal, Loess Plateau, as well as the Yangtze and Yellow Rivers, indicates weakening chemical weathering intensity since the late Pliocene, as the climate cooled. This cooling, coupled with tectonic activity, shifted the dominant weathering regime from more transport-limited to more weathering-limited, causing less chemical depletion of silicate minerals. While silicate weathering rates became strongly correlated to erosion rates, they were decoupled from chemical weathering intensity. Physical denudation and associated silicate weathering rates in the HTP area increased in the Pliocene, driven by both rock uplift and stronger monsoon precipitation, decreasing atmospheric CO2 concentrations, and so contributing to Northern Hemisphere Glaciation (NHG).

  14. CHEMISTRY OF IMPACT-GENERATED SILICATE MELT-VAPOR DEBRIS DISKS

    SciTech Connect

    Visscher, Channon; Fegley, Bruce Jr.

    2013-04-10

    In the giant impact theory for lunar origin, the Moon forms from material ejected by the impact into an Earth-orbiting disk. Here we report the initial results from a silicate melt-vapor equilibrium chemistry model for such impact-generated planetary debris disks. In order to simulate the chemical behavior of a two-phase (melt+vapor) disk, we calculate the temperature-dependent pressure and chemical composition of vapor in equilibrium with molten silicate from 2000 to 4000 K. We consider the elements O, Na, K, Fe, Si, Mg, Ca, Al, Ti, and Zn for a range of bulk silicate compositions (Earth, Moon, Mars, eucrite parent body, angrites, and ureilites). In general, the disk atmosphere is dominated by Na, Zn, and O{sub 2} at lower temperatures (<3000 K) and SiO, O{sub 2}, and O at higher temperatures. The high-temperature chemistry is consistent for any silicate melt composition, and we thus expect abundant SiO, O{sub 2}, and O to be a common feature of hot, impact-generated debris disks. In addition, the saturated silicate vapor is highly oxidizing, with oxygen fugacity (f{sub O{sub 2}}) values (and hence H{sub 2}O/H{sub 2} and CO{sub 2}/CO ratios) several orders of magnitude higher than those in a solar-composition gas. High f{sub O{sub 2}} values in the disk atmosphere are found for any silicate composition because oxygen is the most abundant element in rock. We thus expect high oxygen fugacity to be a ubiquitous feature of any silicate melt-vapor disk produced via collisions between rocky planets.

  15. Shock-enhanced dissolution of silicate minerals: An important planetary surface process

    SciTech Connect

    Boslough, M.B.; Cygan, R.T.

    1987-01-01

    This study was undertaken to examine the effect of shock loading on rock-water interactions and on the dissolution of silicate phases. Shock-recovery experiments were carried out on oligoclase, hornblende, and labradorite. No additional crystalline phases or glass were produced, although mean grain size was decreased and specific surface area increased. Dissolution experiments were conducted; the extracted solutions are being analyzed. (DLC)

  16. Uranium series, volcanic rocks

    USGS Publications Warehouse

    Vazquez, Jorge A.

    2014-01-01

    Application of U-series dating to volcanic rocks provides unique and valuable information about the absolute timing of crystallization and differentiation of magmas prior to eruption. The 238U–230Th and 230Th-226Ra methods are the most commonly employed for dating the crystallization of mafic to silicic magmas that erupt at volcanoes. Dates derived from the U–Th and Ra–Th methods reflect crystallization because diffusion of these elements at magmatic temperatures is sluggish (Cherniak 2010) and diffusive re-equilibration is insignificant over the timescales (less than or equal to 10^5 years) typically associated with pre-eruptive storage of nearly all magma compositions (Cooper and Reid 2008). Other dating methods based on elements that diffuse rapidly at magmatic temperatures, such as the 40Ar/39Ar and (U–Th)/He methods, yield dates for the cooling of magma at the time of eruption. Disequilibrium of some short-lived daughters of the uranium series such as 210Po may be fractionated by saturation of a volatile phase and can be employed to date magmatic gas loss that is synchronous with volcanic eruption (e.g., Rubin et al. 1994).

  17. Geomagnetic field strength 3.2 billion years ago recorded by single silicate crystals.

    PubMed

    Tarduno, John A; Cottrell, Rory D; Watkeys, Michael K; Bauch, Dorothy

    2007-04-05

    The strength of the Earth's early geomagnetic field is of importance for understanding the evolution of the Earth's deep interior, surface environment and atmosphere. Palaeomagnetic and palaeointensity data from rocks formed near the boundary of the Proterozoic and Archaean eons, some 2.5 Gyr ago, show many hallmarks of the more recent geomagnetic field. Reversals are recorded, palaeosecular variation data indicate a dipole-dominated morphology and available palaeointensity values are similar to those from younger rocks. The picture before 2.8 Gyr ago is much less clear. Rocks of the Archaean Kaapvaal craton (South Africa) are among the best-preserved, but even they have experienced low-grade metamorphism. The variable acquisition of later magnetizations by these rocks is therefore expected, precluding use of conventional palaeointensity methods. Silicate crystals from igneous rocks, however, can contain minute magnetic inclusions capable of preserving Archaean-age magnetizations. Here we use a CO2 laser heating approach and direct-current SQUID magnetometer measurements to obtain palaeodirections and intensities from single silicate crystals that host magnetite inclusions. We find 3.2-Gyr-old field strengths that are within 50 per cent of the present-day value, indicating that a viable magnetosphere sheltered the early Earth's atmosphere from solar wind erosion.

  18. Biological and Organic Chemical Decomposition of Silicates. Chapter 7.2

    NASA Technical Reports Server (NTRS)

    Sliverman, M. P.

    1979-01-01

    The weathering of silicate rocks and minerals, an important concern of geologists and geochemists for many years, traditionally has been approached from strictly physical and chemical points of view. Biological effects were either unrecognized, ignored, or were mentioned in passing to account for such phenomena as the accumulation of organic matter in sediments or the generation of reducing environments. A major exception occurred in soil science where agricultural scientists, studying the factors important in the development of soils and their ability to nourish and sustain various crops, laid the foundation for much of what is known of the biological breakdown of silicate rocks and minerals. The advent of the space age accelerated the realization that many environmental problems and geochemical processes on Earth can only be understood in terms of ecosystems. This in turn, spurred renewed interest and activity among modem biologists, geologists and soil scientists attempting to unravel the intimate relations between biology and the weathering of silicate rocks and minerals of the earth's surface.

  19. Biological and Organic Chemical Decomposition of Silicates. Chapter 7.2

    NASA Technical Reports Server (NTRS)

    Silverman, M. P.

    1979-01-01

    The weathering of silicate rocks and minerals, an important concern of geologists and geochemists for many years, traditionally has been approached from strictly physical and chemical points of view. Biological effects were either unrecognized, ignored, or were mentioned in passing to account for such phenomena as the accumulation of organic matter in sediments or the generation of reducing environments. A major exception occurred in soil science where agricultural scientists, studying the factors important in the development of soils and their ability to nourish and sustain various crops, laid the foundation for much of what is known of the biological breakdown of silicate rocks and minerals. The advent of the space age accelerated the realization that many environmental problems and geo- chemical processes on Earth can only be understood in terms of ecosystems. This in turn, spurred renewed interest and activity among modem biologists, geologists and soil scientists attempting to unravel the intimate relations between biology and the weathering of silicate rocks and minerals of the earth surface.

  20. Biological and Organic Chemical Decomposition of Silicates. Chapter 7.2

    NASA Technical Reports Server (NTRS)

    Silverman, M. P.

    1979-01-01

    The weathering of silicate rocks and minerals, an important concern of geologists and geochemists for many years, traditionally has been approached from strictly physical and chemical points of view. Biological effects were either unrecognized, ignored, or were mentioned in passing to account for such phenomena as the accumulation of organic matter in sediments or the generation of reducing environments. A major exception occurred in soil science where agricultural scientists, studying the factors important in the development of soils and their ability to nourish and sustain various crops, laid the foundation for much of what is known of the biological breakdown of silicate rocks and minerals. The advent of the space age accelerated the realization that many environmental problems and geo- chemical processes on Earth can only be understood in terms of ecosystems. This in turn, spurred renewed interest and activity among modem biologists, geologists and soil scientists attempting to unravel the intimate relations between biology and the weathering of silicate rocks and minerals of the earth surface.

  1. Biological and Organic Chemical Decomposition of Silicates. Chapter 7.2

    NASA Technical Reports Server (NTRS)

    Sliverman, M. P.

    1979-01-01

    The weathering of silicate rocks and minerals, an important concern of geologists and geochemists for many years, traditionally has been approached from strictly physical and chemical points of view. Biological effects were either unrecognized, ignored, or were mentioned in passing to account for such phenomena as the accumulation of organic matter in sediments or the generation of reducing environments. A major exception occurred in soil science where agricultural scientists, studying the factors important in the development of soils and their ability to nourish and sustain various crops, laid the foundation for much of what is known of the biological breakdown of silicate rocks and minerals. The advent of the space age accelerated the realization that many environmental problems and geochemical processes on Earth can only be understood in terms of ecosystems. This in turn, spurred renewed interest and activity among modem biologists, geologists and soil scientists attempting to unravel the intimate relations between biology and the weathering of silicate rocks and minerals of the earth's surface.

  2. Poohbear Rock

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image, taken by Sojourner's front right camera, was taken when the rover was next to Poohbear (rock at left) and Piglet (not seen) as it looked out toward Mermaid Dune. The textures differ from the foreground soil containing a sorted mix of small rocks, fines and clods, from the area a bit ahead of the rover where the surface is covered with a bright drift material. Soil experiments where the rover wheels dug in the soil revealed that the cloudy material exists underneath the drift.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  3. White Rock

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 19 April 2002) The Science 'White Rock' is the unofficial name for this unusual landform which was first observed during the Mariner 9 mission in the early 1970's. As later analysis of additional data sets would show, White Rock is neither white nor dense rock. Its apparent brightness arises from the fact that the material surrounding it is so dark. Images from the Mars Global Surveyor MOC camera revealed dark sand dunes surrounding White Rock and on the floor of the troughs within it. Some of these dunes are just apparent in the THEMIS image. Although there was speculation that the material composing White Rock could be salts from an ancient dry lakebed, spectral data from the MGS TES instrument did not support this claim. Instead, the White Rock deposit may be the erosional remnant of a previously more continuous occurrence of air fall sediments, either volcanic ash or windblown dust. The THEMIS image offers new evidence for the idea that the original deposit covered a larger area. Approximately 10 kilometers to the southeast of the main deposit are some tiny knobs of similarly bright material preserved on the floor of a small crater. Given that the eolian erosion of the main White Rock deposit has produced isolated knobs at its edges, it is reasonable to suspect that the more distant outliers are the remnants of a once continuous deposit that stretched at least to this location. The fact that so little remains of the larger deposit suggests that the material is very easily eroded and simply blows away. The Story Fingers of hard, white rock seem to jut out like icy daggers across a moody Martian surface, but appearances can be deceiving. These bright, jagged features are neither white, nor icy, nor even hard and rocky! So what are they, and why are they so different from the surrounding terrain? Scientists know that you can't always trust what your eyes see alone. You have to use other kinds of science instruments to measure things that our eyes can

  4. Poohbear Rock

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image, taken by Sojourner's front right camera, was taken when the rover was next to Poohbear (rock at left) and Piglet (not seen) as it looked out toward Mermaid Dune. The textures differ from the foreground soil containing a sorted mix of small rocks, fines and clods, from the area a bit ahead of the rover where the surface is covered with a bright drift material. Soil experiments where the rover wheels dug in the soil revealed that the cloudy material exists underneath the drift.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  5. Meridiani Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    16 September 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the complex surfaces of some of the light- and intermediate-toned sedimentary rock exposed by erosion in eastern Sinus Meridiani. Similar rocks occur at the Mars Exploration Rover, Opportunity, site, but they are largely covered by windblown sand and granules. The dark feature with a rayed pattern is the product of a meteor impact.

    Location near: 0.8oN, 355.2oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  6. Terby's Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    25 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows light-toned, layered, sedimentary rock outcrops in the crater, Terby. The crater is located on the north rim of Hellas Basin. If one could visit the rocks in Terby, one might learn from them whether they formed in a body of water. It is possible, for example, that Terby was a bay in a larger, Hellas-wide sea.

    Location near: 27.9oS, 285.7oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  7. White Rock

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 19 April 2002) The Science 'White Rock' is the unofficial name for this unusual landform which was first observed during the Mariner 9 mission in the early 1970's. As later analysis of additional data sets would show, White Rock is neither white nor dense rock. Its apparent brightness arises from the fact that the material surrounding it is so dark. Images from the Mars Global Surveyor MOC camera revealed dark sand dunes surrounding White Rock and on the floor of the troughs within it. Some of these dunes are just apparent in the THEMIS image. Although there was speculation that the material composing White Rock could be salts from an ancient dry lakebed, spectral data from the MGS TES instrument did not support this claim. Instead, the White Rock deposit may be the erosional remnant of a previously more continuous occurrence of air fall sediments, either volcanic ash or windblown dust. The THEMIS image offers new evidence for the idea that the original deposit covered a larger area. Approximately 10 kilometers to the southeast of the main deposit are some tiny knobs of similarly bright material preserved on the floor of a small crater. Given that the eolian erosion of the main White Rock deposit has produced isolated knobs at its edges, it is reasonable to suspect that the more distant outliers are the remnants of a once continuous deposit that stretched at least to this location. The fact that so little remains of the larger deposit suggests that the material is very easily eroded and simply blows away. The Story Fingers of hard, white rock seem to jut out like icy daggers across a moody Martian surface, but appearances can be deceiving. These bright, jagged features are neither white, nor icy, nor even hard and rocky! So what are they, and why are they so different from the surrounding terrain? Scientists know that you can't always trust what your eyes see alone. You have to use other kinds of science instruments to measure things that our eyes can

  8. White Rock

    NASA Technical Reports Server (NTRS)

    2005-01-01

    14 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of the famous 'White Rock' feature in Pollack Crater in the Sinus Sabaeus region of Mars. The light-toned rock is not really white, but its light tone caught the eye of Mars geologists as far back as 1972, when it was first spotted in images acquired by Mariner 9. The light-toned materials are probably the remains of a suite of layered sediments that once spread completely across the interior of Pollack Crater. Dark materials in this image include sand dunes and large ripples.

    Location near: 8.1oS, 335.1oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Southern Summer

  9. Low-(18)O Silicic Magmas: Why Are They So Rare?

    SciTech Connect

    Balsley, S.D.; Gregory, R.T.

    1998-10-15

    LOW-180 silicic magmas are reported from only a small number of localities (e.g., Yellowstone and Iceland), yet petrologic evidence points to upper crustal assimilation coupled with fractional crystallization (AFC) during magma genesis for nearly all silicic magmas. The rarity of 10W-l `O magmas in intracontinental caldera settings is remarkable given the evidence of intense 10W-l*O meteoric hydrothermal alteration in the subvolcanic remnants of larger caldera systems. In the Platoro caldera complex, regional ignimbrites (150-1000 km3) have plagioclase 6180 values of 6.8 + 0.1%., whereas the Middle Tuff, a small-volume (est. 50-100 km3) post-caldera collapse pyroclastic sequence, has plagioclase 8]80 values between 5.5 and 6.8%o. On average, the plagioclase phenocrysts from the Middle Tuff are depleted by only 0.3%0 relative to those in the regional tuffs. At Yellowstone, small-volume post-caldera collapse intracaldera rhyolites are up to 5.5%o depleted relative to the regional ignimbrites. Two important differences between the Middle Tuff and the Yellowstone 10W-180 rhyolites elucidate the problem. Middle Tuff magmas reached water saturation and erupted explosively, whereas most of the 10W-l 80 Yellowstone rhyolites erupted effusively as domes or flows, and are nearly devoid of hydrous phenocrysts. Comparing the two eruptive types indicates that assimilation of 10W-180 material, combined with fractional crystallization, drives silicic melts to water oversaturation. Water saturated magmas either erupt explosively or quench as subsurface porphyrins bejiire the magmatic 180 can be dramatically lowered. Partial melting of low- 180 subvolcanic rocks by near-anhydrous magmas at Yellowstone produced small- volume, 10W-180 magmas directly, thereby circumventing the water saturation barrier encountered through normal AFC processes.

  10. Rafted Rock

    NASA Image and Video Library

    2016-11-09

    This area of Amazonis Planitia to the west of the large volcano Olympus Mons was once flooded with lava. A huge eruption flowed out across the relatively flat landscape. Sometimes called "flood basalt," the lava surface quickly cooled and formed a thin crust of solidified rock that was pushed along with the flowing hot liquid rock. Hills and mounds that pre-dated the flooding eruption became surrounded, forming obstructions to the relentless march of lava. In this image, these obstructions appeared to have poked up and sliced through the lava crust as the molten rock and crust moved together from west to east, over and past the stationary mounds. The result is a series of parallel grooves or channels with the obstructing mound remaining at the western end as the flow came to rest. From such images scientists can reconstruct the direction of the lava flow, potentially tracing it back to the source vent. http://photojournal.jpl.nasa.gov/catalog/PIA21204

  11. Gels composed of sodium-aluminium silicate, lake magadi, kenya.

    PubMed

    Eugster, H P; Jones, B F

    1968-07-12

    Sodium-aluminum silicate gels are found in surficial deposits as thick as 5 centimeters in the Magadi area of Kenya. Chemical data indicate they are formed by the interaction of hot alkaline springwaters (67 degrees to 82 degrees C; pH, about 9) with alkali trachyte flows and their detritus, rather than by direct precipitation. In the process, Na(2)O is added from and silica is released to the saline waters of the springs. Algal mats protect the gels from erosion and act as thermal insulators. The gels are probably yearly accumulates that are washed into the lakes during floods. Crystallization of these gels in the laboratory yields analcite; this fact suggests that some analcite beds in lacustrine deposits may have formed from gels. Textural evidence indicates that cherts of rocks of the Pleistocene chert series in the Magadi area may have formed from soft sodium silicate gels. Similar gels may have acted as substrates for the accumulation and preservation of prebiological organic matter during the Precambrian.

  12. Boron in chert and Precambrian siliceous iron formations

    NASA Astrophysics Data System (ADS)

    Truscott, Marilyn G.; Shaw, Denis M.

    1984-11-01

    In order to assess the importance of siliceous sediments as a sink for oceanic B and to determine the effect of diagenesis on the mobilization of B, samples were analysed from chert nodules, bedded cherts, and siliceous banded iron formations from a variety of sedimentary environments and geologic ages. Boron analyses on bulk samples were made by prompt gamma neutron activation analysis. The distribution of B in rocks was mapped using α-track methods. Nodular Phanerozoic cherts typically contain 50-150 ppm B, and bedded cherts somewhat less. The B is initially concentrated in tests of silica-secreting organisms, but some is lost in early diagenesis as silica progressively recrystallises to quartz. Banded iron formation silica of Archean and Proterozoic age usually contains < 2 ppm B. This conforms with the view that such silica is not of biogenic origin but, since many iron formations are undoubtedly of marine origin, raises the question whether Precambrian oceans were impoverished in B. Analyses of Precambrian marine argillaceous sediments, averaging 70 ppm B, do not resolve this question.

  13. Iron-magnesium silicate bioweathering on Earth (and Mars?).

    PubMed

    Fisk, M R; Popa, R; Mason, O U; Storrie-Lombardi, M C; Vicenzi, E P

    2006-02-01

    We examined the common, iron-magnesium silicate minerals olivine and pyroxene in basalt and in mantle rocks to determine if they exhibit textures similar to bioweathering textures found in glass. Our results show that weathering in olivine may occur as long, narrow tunnels (1-3 microm in diameter and up to 100 microm long) and as larger irregular galleries, both of which have distinctive characteristics consistent with biological activity. These weathering textures are associated with clay mineral by-products and nucleic acids. We also examined olivine and pyroxene in martian meteorites, some of which experienced preterrestrial aqueous alteration. Some olivines and pyroxenes in the martian meteorite Nakhla were found to contain tunnels that are similar in size and shape to tunnels in terrestrial iron-magnesium silicates that contain nucleic acids. Though the tunnels found in Nakhla are similar to the biosignatures found in terrestrial minerals, their presence cannot be used to prove that the martian alteration features had a biogenic origin. The abundance and wide distribution of olivine and pyroxene on Earth and in the Solar System make bioweathering features in these minerals potentially important new biosignatures that may play a significant role in evaluating whether life ever existed on Mars.

  14. Gels composed of sodium-aluminum silicate, Lake Magadi, Kenya

    USGS Publications Warehouse

    Eugster, H.P.; Jones, B.F.

    1968-01-01

    Sodium-aluminum silicate gels are found in surftcial deposits as thick as 5 centimeters in the Magadi area of Kenya. Chemical data indicate they are formed by the interaction of hot alkaline springwaters (67?? to 82??C; pH, about 9) with alkali trachyte flows and their detritus, rather than by direct precipitation. In the process, Na2O is added from and silica is released to the saline waters of the springs. Algal mats protect the gels from erosion and act as thermal insulators. The gels are probably yearly accumulates that are washed into the lakes during floods. Crystallization of these gels in the laboratory yields analcite; this fact suggests that some analcite beds in lacustrine deposits may have formed from gels. Textural evidence indicates that cherts of rocks of the Pleistocene chert series in the Magadi area may have formed from soft sodium silicate gels. Similar gels may have acted as substrates for the accumulation and preservation of prebiological organic matter during the Precambrian.

  15. Authigenic Mineralization of Silicates at the Organic-water Interface

    NASA Astrophysics Data System (ADS)

    McEvoy, B.; Wallace, A. F.

    2015-12-01

    It is relatively common for some fraction of organic material to be preserved in the sedimentary rock record as disseminated molecular fragments. The survival of wholly coherent tissues from primarily soft-bodied organisms is far more unusual. However, the literature is now well- populated with spectacular examples of soft-tissue preservation ranging from a 2,600 year old human brain to the tissues of the Ediacaran biota that have survived ~600 million years. Some of the most exceptional examples of soft tissue preservation are from the Proterozoic-Cambrian transition, however, nearly all modes of fossil preservation during this time are debated. Clay mineral templates have been implicated as playing a role in several types of soft tissue preservation, including Burgess Shale and Beecher's Trilobite-type preservation, and more recently, Bitter Springs-type silicification. Yet, there is still much debate over whether these clay mineral coatings form during early stage burial and diagenesis, or later stage metamorphism. This research addresses this question by using in situ fluid cell Atomic Force Microscopy (AFM) to investigate the nucleation and growth of silicate minerals on model biological surfaces. Herein we present preliminary results on the deposition of hydrous magnesium silicates on self-assembled monolayers (-OH, -COOH, -CH3, and -H2PO3 terminated surfaces) at ambient conditions.

  16. Alkali Silicate Vehicle Forms Durable, Fireproof Paint

    NASA Technical Reports Server (NTRS)

    Schutt, John B.; Seindenberg, Benjamin

    1964-01-01

    The problem: To develop a paint for use on satellites or space vehicles that exhibits high resistance to cracking, peeling, or flaking when subjected to a wide range of temperatures. Organic coatings will partially meet the required specifications but have the inherent disadvantage of combustibility. Alkali-silicate binders, used in some industrial coatings and adhesives, show evidence of forming a fireproof paint, but the problem of high surface-tension, a characteristic of alkali silicates, has not been resolved. The solution: Use of a suitable non-ionic wetting agent combined with a paint incorporating alkali silicate as the binder.

  17. Late Cretaceous intraplate silicic volcanism in the Lake Chad region: incipient continental rift volcanism vs. Cameroon Line volcanism

    NASA Astrophysics Data System (ADS)

    Shellnutt, G.; Lee, T. Y.; Torng, P. K.; Yang, C. C.

    2015-12-01

    The crustal evolution of west-central Africa during the Cretaceous was directly related to plate motion associated with the opening of the central Atlantic Ocean. Late Cretaceous (~66 Ma) to recent magmatism related to the Cameroon Line stretches from Northern Cameroon (i.e. Golda Zuelva) to the Gulf of Guinea (i.e. Pagalu) and is considered to be due to mantle-crust interaction. The volcanic rocks at Hadjer el Khamis, west-central Chad, are considered to be amongst the oldest volcanic rocks of the Cameroon Line but their relationship is uncertain because they erupted during a period of a regional extension associated with the opening of the Late Cretaceous (~75 Ma) Termit basin. The silicic volcanic rocks can be divided into a peraluminous group and a peralkaline group with both rock types having similar chemical characteristics as within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206Pb/238U age of 74.4 ± 1.3 Ma and indicates the rocks erupted ~10 million years before the next oldest eruption attributed to the Cameroon Line. The Sr isotopes (i.e. ISr = 0.7050 to 0.7143) show a wide range but the Nd isotopes (i.e. 143Nd/144Ndi = 0.51268 to 0.51271) are more uniform and indicate that the rocks were derived from a moderately depleted mantle source. Major and trace elemental modeling show that the silicic rocks likely formed by shallow fractionation of a mafic parental magma where the peraluminous rocks experienced crustal contamination and the peralkaline rocks did not. The silicic rocks are more isotopically similar to Late Cretaceous basalts in the Doba and Bongor basins (i.e. ISr = 0.7040 to 0.7060; 143Nd/144Ndi = 0.51267 to 0.51277) of southern Chad than to rocks of the Cameroon Line (i.e. ISr = 0.7026 to 0.7038; 143Nd/144Ndi = 0.51270 to 0.51300). Given the age and isotopic compositions, it is likely that the silicic volcanic rocks of the Lake Chad area are related to Late Cretaceous extensional tectonics rather than to Cameroon Line magmatism.

  18. Low Velocity Sphere Impact of a Soda Lime Silicate Glass

    SciTech Connect

    Wereszczak, Andrew A; Fox, Ethan E; Morrissey, Timothy G; Vuono, Daniel J

    2011-10-01

    This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity (< 30 m/s or < 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate glass, soda-lime silicate glass, steel, silicon nitride, and alumina. A gas gun was fabricated to produce controlled velocity delivery of the spheres against Starphire tile targets. Minimum impact velocities to initiate fracture in the Starphire were measured and interpreted in context to the kinetic energy of impact and the elastic property mismatch between the any of the five sphere-Starphire-target combinations. The primary observations from this low velocity (< 30 m/s or < 65 mph) testing were: (1) Frictional effects contribute to fracture initiation. (2) Spheres with a lower elastic modulus require less force to initiate fracture in the Starphire than spheres with a higher elastic modulus. (3) Contact-induced fracture did not initiate in the Starphire SLS for impact kinetic energies < 150 mJ. Fracture sometimes initiated or kinetic energies between {approx} 150-1100 mJ; however, it tended to occur when lower elastic modulus spheres were impacting it. Contact-induced fracture would always occur for impact energies > 1100 mJ. (4) The force necessary to initiate contact-induced fracture is higher under dynamic or impact conditions than it is under quasi-static indentation conditions. (5) Among the five used sphere materials, silicon nitride was the closest match to 'rock' in terms of both density and (probably) elastic modulus.

  19. The role of silicate surfaces on calcite precipitation kinetics

    NASA Astrophysics Data System (ADS)

    Stockmann, Gabrielle J.; Wolff-Boenisch, Domenik; Bovet, Nicolas; Gislason, Sigurdur R.; Oelkers, Eric H.

    2014-06-01

    The aim of this study is to illuminate how calcite precipitation depends on the identity and structure of the growth substrate. Calcite was precipitated at 25 °C from supersaturated aqueous solutions in the presence of seeds of either calcite or one of six silicate materials: augite, enstatite, labradorite, olivine, basaltic glass and peridotite rock. Calcite saturation was achieved by mixing a CaCl2-rich aqueous solution with a NaHCO3-Na2CO3 aqueous buffer in mixed-flow reactors containing 0.5-2 g of mineral, rock, or glass seeds. This led to an inlet fluid calcite saturation index of 0.6 and a pH equal to 9.1. Although the inlet fluid composition, flow rate, and temperature were identical for all experiments, the onset of calcite precipitation depended on the identity of the seeds present in the reactor. Calcite precipitated instantaneously and at a constant rate in the presence of calcite grains. Calcite precipitated relatively rapidly on labradorite, olivine, enstatite, and peridotite (mainly composed of Mg-olivine) surfaces, but more slowly on augite and basaltic glass. Calcite precipitation rates, however, became independent of substrate identity and mass over time, and all rates approach 10-9.68 ± 0.08 mol/s for ∼10 day long experiments and 10-9.21 ± 0.2 mol/s for ∼70 day long experiments. Scanning Electron Microscope images showed olivine, enstatite and peridotite surfaces to be covered extensively with calcite coatings at the end of the experiments. Less calcite was found on labradorite and augite, and the least on basaltic glass. In all cases, calcite precipitation occurs on the mineral, rock or glass surfaces. Calcite precipitation on these surfaces, however, negligibly affects the dissolution rates of the silicate grains. These results support ultramafic and basalt carbonation as a long-term carbon storage strategy, as calcite readily precipitates on the surfaces of minerals contained in these rocks without inhibiting their dissolution.

  20. New insights on the occurrence of peperites and sedimentary deposits within the silicic volcanic sequences of the Paraná Magmatic Province, Brazil

    NASA Astrophysics Data System (ADS)

    Luchetti, A. C. F.; Nardy, A. J. R.; Machado, F. B.; Madeira, J. E. O.; Arnosio, J. M.

    2014-03-01

    The PMP (Paraná Magmatic Province) is characterized by lava flows of the Early Cretaceous Serra Geral Formation which covers about 75% of the Paraná Basin (southern and southeastern Brazil), composed of a thick (up to 1600 m) volcanic sequence formed by a succession of petrographically and geochemically distinct units of basic and silicic composition. The whole package must have been emplaced during approximately 3 million years of nearly uninterrupted activity. A few aeolian sandstone layers, indicating arid environmental conditions (the Botucatu Formation), are interlayered in the lower basalts. Above the basalts, the Palmas and Chapecó Members are composed of silicic volcanic rocks (quartz latites, dacites, rhyodacites and rhyolites) and basalts. This paper presents new evidence of sedimentation episodes separating silicic volcanic events, expressed by the occurrence of sedimentary deposits. Interaction between the volcanic bodies and the coeval unconsolidated sediments formed peperites. The sediments were observed between basaltic lava flows and silicic rocks or interlayered in the Palmas-type rocks, between the Chapecó-type rocks and overlying basaltic flows, between silicic bodies of the Palmas and Chapecó types, and interlayered within Palmas-type units. The observed structures indicate that the sediments were still wet and unconsolidated, or weakly consolidated, at the time of volcanism, which, coupled with the sediment features, reflect environmental conditions that are different from those characterizing the Botucatu arid conditions.

  1. Laser processing of siliceous materials

    NASA Astrophysics Data System (ADS)

    Panzner, Michael; Lenk, Andreas; Wiedemann, Guenter R.; Hauptmann, Jan; Weiss, Hans J.; Ruemenapp, Thomas; Morgenthal, Lothar; Beyer, Eckhard

    2000-08-01

    Laser processing of siliceous materials becomes increasingly important. Analogous to the laser processing of conventional materials there are applications in the fields of cleaning, surface processing, cutting, etc. The present paper concerns the state of the art and new applications: (1) Laser cleaning of natural stone surfaces. The good disability allows restoration work to be carried out conveniently, as for example the complete removal of crusts or the removal to such degree that moisture is not trapped beneath. (2) Non-slip finish of polished natural stone surfaces: The excellent focusing of laser beams on spots as small as 100 micrometer and below can be exploited to produce macroscopically invisible structures on the surfaces of different materials. This permits microscopically small craters and lentil shaped depressions to be generated on the stone surface. Therefore it is possible to provide a non-slip finish to polished natural stone surfaces without noticeably impairing the gloss. (3) Concrete cutting: In Europe, and particularly in Germany, there is a growing demand for redevelopment of concrete apartment buildings, involving the removal of non-bearing walls and the cutting of openings. The temporal relocation of residents due to the noise and moisture from the use of diamond tools could be avoided by applying a laser cutting technology. With a 3 kW-Nd-YAG-laser, 70 mm concrete can be cut with rates up to 25 mm/min.

  2. Organically modified silicate aerogels, ``Aeromosils``

    SciTech Connect

    Kramer, S.J.; Mackenzie, J.D.; Rubio-Alonso, F.

    1996-12-31

    Aerogels derived from sol-gel oxides such as silica have become quite scientifically popular because of their extremely low densities, high surface areas, and their interesting optical, dielectric, thermal and acoustic properties. However, their commercial applicability has thus far been rather limited, due in great part to their brittleness and hydrophilicity. In prior work by the research group, modifying silicate gel structures with flexible, organic containing polymers such as polydimethylsiloxane imparted significant compliance (even rubbery behavior) and hydrophobicity. These materials have been referred to as Ormosils. This study expounds on the current effort to extend these desirable properties to aerogels, and in-so-doing, creating novel ``Aeromosils``. Reactive incorporation of hydroxy-terminal polydimethylsiloxane (PDMS) into silica sol-gels was made using both acid and two-step acid/base catalyzed processes. Aerogels were derived by employing the supercritical CO{sub 2} technique. Analyses of microstructure were made using nitrogen adsorption (BET surface area and pore size distribution), and some mechanical strengths were derived from tensile strength testing. Interesting Aeromosil properties obtained include optical transparency, surface areas of up to 1,200 m{sup 2}/g, rubberiness, and better strength than corresponding silica aerogels with elongations at break exceeding 5% in some cases.

  3. Thermal Inertia of Rocks and Rock Populations

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Jakosky, B. M.; Mellon, M. T.

    2001-01-01

    The effective thermal inertia of rock populations on Mars and Earth is derived from a model of effective inertia versus rock diameter. Results allow a parameterization of the effective rock inertia versus rock abundance and bulk and fine component inertia. Additional information is contained in the original extended abstract.

  4. Improved alkali-metal/silicate binders

    NASA Technical Reports Server (NTRS)

    Schutt, J.

    1978-01-01

    Family of inorganic binders utilizes potassium or sodium oxide/silicate dispersion and employs high mole ratio of silicon dioxide to alkali-metal binder. Binders are stable, inexpensive, extremely water resistant, and easy to apply.

  5. Prometheus Silicates/Sulfur dioxide/NIMS

    NASA Image and Video Library

    2000-05-18

    The Prometheus region of Jupiter moon Io was imaged by NASA Galileo spacecraft in 1999. The maps made from spectrometer data show the interplay between hot silicates on the surface and sulfur dioxide frost.

  6. Sedimentary Rocks

    NASA Technical Reports Server (NTRS)

    2005-01-01

    6 November 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows outcrops of sedimentary rocks in a crater located just north of the Sinus Meridiani region. Perhaps the crater was once the site of a martian lake.

    Location near: 2.9oN, 359.0oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  7. Origin of silicic crust by rifting and bimodal plume volcanism in the Afar Depression

    NASA Astrophysics Data System (ADS)

    Ghatak, A.; Basu, A. R.; Ebinger, C. J.

    2010-12-01

    The youngest mantle plume province worldwide occurs at the seismically and volcanically active East African - Red Sea - Gulf of Aden (Afar) triple junction, where one or more upwellings has impinged the thick cratonic lithosphere since ~45 Ma. A spectacular example of magmatism in the Afar depression is seen in the present to < 2 Ma old bimodal fissural mafic and peralkaline silicic eruptions in the ~60 km-long Dabbahu-Manda Hararo (DMH) Rift. In this study we report major, trace elements, and Nd-Sr-Pb isotopes in recent basaltic and silicic rocks originating from the center of the DMH rift segment, exposed along the rift axis and flanks of this segment. The rare earth element (REE) patterns of the silicic rocks and basalts are different in two significant ways: (1) the silicic rocks show a prominent positive Ce-anomaly that is extremely rare in volcanic rocks; and (2) this positive Ce-anomaly is accompanied by a strong negative Eu-anomaly. These anomalies are absent in the basaltic rocks. The positive Ce-anomaly is probably due to interaction in a magma chamber, similar in composition to the basalts, with deep saline aquifer or brines that typically show positive Ce-anomaly. The REE patterns of the two lava groups are interpreted to be due to fractional crystallization of plagioclase in a magma chamber similar in REE composition as the basalts that erupted in the DMH segments. We interpret the silicic rocks to be residues after ~20% fractional crystallization of plagioclase in the DMH basalts. The Nd-Pb isotopic composition of the basalts and rhyolites of the DMH are similar to the Ethiopian plume as defined by the ~30 Ma old Ethiopian flood basalts. Based on their high 3He/4He ratios (R/RA ~30) and Nd-Sr-Pb isotopic data, the source of the Ethiopian plume is generally believed to be in the lower mantle. Therefore, the similarity of the Nd-Pb and Pb-Pb isotopic variations between the Ethiopian plume and the DMH lavas indicates that these lavas were sourced from

  8. Vanadium magnetite-melt oxybarometry of natural, silicic magmas: a comparison of various oxybarometers and thermometers

    NASA Astrophysics Data System (ADS)

    Arató, Róbert; Audétat, Andreas

    2017-07-01

    To test a recently developed oxybarometer for silicic magmas based on partitioning of vanadium between magnetite and silicate melt, a comprehensive oxybarometry and thermometry study on 22 natural rhyolites to dacites was conducted. Investigated samples were either vitrophyres or holocrystalline rocks in which part of the mineral and melt assemblage was preserved only as inclusions within phenocrysts. Utilized methods include vanadium magnetite-melt oxybarometry, Fe-Ti oxide thermometry and -oxybarometry, zircon saturation thermometry, and two-feldspar thermometry, with all analyses conducted by laser-ablation ICP-MS. Based on the number of analyses, the reproducibility of the results and the certainty of contemporaneity of the analyzed minerals and silicate melts the samples were grouped into three classes of reliability. In the most reliable ( n = 5) and medium reliable ( n = 10) samples, all fO2 values determined via vanadium magnetite-melt oxybarometry agree within 0.5 log units with the fO2 values determined via Fe-Ti oxide oxybarometry, except for two samples of the medium reliable group. In the least reliable samples ( n = 7), most of which show evidence for magma mixing, calculated fO2 values agree within 0.75 log units. Comparison of three different thermometers reveals that temperatures obtained via zircon saturation thermometry agree within the limits of uncertainty with those obtained via two-feldspar thermometry in most cases, whereas temperatures obtained via Fe-Ti oxide thermometry commonly deviate by ≥50 °C due to large uncertainties associated with the Fe-Ti oxide model at T- fO2 conditions typical of most silicic magmas. Another outcome of this study is that magma mixing is a common but easily overlooked phenomenon in silicic volcanic rocks, which means that great care has to be taken in the application and interpretation of thermometers and oxybarometers.

  9. Influence of Silicate Melt Composition on Metal/Silicate Partitioning of W, Ge, Ga and Ni

    NASA Technical Reports Server (NTRS)

    Singletary, S. J.; Domanik, K.; Drake, M. J.

    2005-01-01

    The depletion of the siderophile elements in the Earth's upper mantle relative to the chondritic meteorites is a geochemical imprint of core segregation. Therefore, metal/silicate partition coefficients (Dm/s) for siderophile elements are essential to investigations of core formation when used in conjunction with the pattern of elemental abundances in the Earth's mantle. The partitioning of siderophile elements is controlled by temperature, pressure, oxygen fugacity, and by the compositions of the metal and silicate phases. Several recent studies have shown the importance of silicate melt composition on the partitioning of siderophile elements between silicate and metallic liquids. It has been demonstrated that many elements display increased solubility in less polymerized (mafic) melts. However, the importance of silicate melt composition was believed to be minor compared to the influence of oxygen fugacity until studies showed that melt composition is an important factor at high pressures and temperatures. It was found that melt composition is also important for partitioning of high valency siderophile elements. Atmospheric experiments were conducted, varying only silicate melt composition, to assess the importance of silicate melt composition for the partitioning of W, Co and Ga and found that the valence of the dissolving species plays an important role in determining the effect of composition on solubility. In this study, we extend the data set to higher pressures and investigate the role of silicate melt composition on the partitioning of the siderophile elements W, Ge, Ga and Ni between metallic and silicate liquid.

  10. Rock mechanics. Second edition

    SciTech Connect

    Jumikis, A.R.

    1983-01-01

    Rock Mechanics, 2nd Edition deals with rock as an engineering construction material-a material with which, upon which, and within which civil engineers build structures. It thus pertains to hydraulic structures engineering; to highway, railway, canal, foundation, and tunnel engineering; and to all kinds of rock earthworks and to substructures in rock. Major changes in this new edition include: rock classification, rock types and description, rock testing equipment, rock properties, stability effects of discontinuity and gouge, grouting, gunite and shotcrete, and Lugeon's water test. This new edition also covers rock bolting and prestressing, pressure-grouted soil anchors, and rock slope stabilization.

  11. Sublithospheric Triggers for Episodic Silicic Magmatism in Subduction Zones

    NASA Astrophysics Data System (ADS)

    Gerya, T.; Vogt, K.; Schubert, M.

    2014-12-01

    The melt source and ascent mechanisms for crustal-scale silicic magmatism in subduction zones remain a matter of debate. Recent petrological-thermo-mechanical numerical experiments suggest that important physical controls of this process can be of sublithospheric origin. Firstly, deep sources of silicic magma can be related to episodic development of positively buoyant diapiric structures in the mantle wedge originated from deeply subducted rock mélanges (Gerya and Yuen, 2003; Castro and Gerya, 2008). Partial melting of these rapidly ascending lithologically mixed structures can produce silicic magmas with a relatively constant major element composition and variable time-dependent isotopic ratios inherited from the mélange (Vogt et al., 2013). Secondly, episodic injections of subduction-related mantle-derived mafic magmas into a partially molten hot zone of the arc lower crust can drive ascents of pre-existing felsic crustal magmas toward upper crustal levels. The injection of mafic magma induces overpressure in the lower crustal magma reservoir, which increases crustal stresses and triggers development of brittle/plastic fracture zones serving as conduits for the rapid episodic ascent of felsic magmas (Shubert et al., 2013). Our numerical results thus imply that subduction-related sublithospheric magma intrusions into the lower arc crust may both be the prime source for the generation of silicic magmas and the major physical driving mechanism for their episodic ascent toward upper crustal levels. References:Castro, A., and Gerya, T.V., 2008. Magmatic implications of mantle wedge plumes: experimental study. Lithos 103, 138-148. Gerya, T.V., and Yuen, D.A., 2003. Rayleigh-Taylor instabilities from hydration and melting propel "cold plumes" at subduction zones. Earth and Planetary Science Letters 212, 47-62.Schubert, M., Driesner, T., Gerya, T.V., Ulmer, P., 2013. Mafic injection as a trigger for felsic magmatism: A numerical study. Geochemistry, Geophysics

  12. Thermodynamics and Kinetics of Silicate Vaporization

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Costa, Gustavo C. C.

    2015-01-01

    Silicates are a common class of materials that are often exposed to high temperatures. The behavior of these materials needs to be understood for applications as high temperature coatings in material science as well as the constituents of lava for geological considerations. The vaporization behavior of these materials is an important aspect of their high temperature behavior and it also provides fundamental thermodynamic data. The application of Knudsen effusion mass spectrometry (KEMS) to silicates is discussed. There are several special considerations for silicates. The first is selection of an appropriate cell material, which is either nearly inert or has well-understood interactions with the silicate. The second consideration is proper measurement of the low vapor pressures. This can be circumvented by using a reducing agent to boost the vapor pressure without changing the solid composition or by working at very high temperatures. The third consideration deals with kinetic barriers to vaporization. The measurement of these barriers, as encompassed in a vaporization coefficient, is discussed. Current measured data of rare earth silicates for high temperature coating applications are discussed. In addition, data on magnesium-iron-silicates (olivine) are presented and discussed.

  13. Rock Driller

    NASA Technical Reports Server (NTRS)

    Peterson, Thomas M.

    2001-01-01

    The next series of planetary exploration missions require a method of extracting rock and soil core samples. Therefore a prototype ultrasonic core driller (UTCD) was developed to meet the constraints of Small Bodies Exploration and Mars Sample Return Missions. The constraints in the design are size, weight, power, and axial loading. The ultrasonic transducer requires a relatively low axial load, which is one of the reasons this technology was chosen. The ultrasonic generator breadboard section can be contained within the 5x5x3 limits and weighs less than two pounds. Based on results attained the objectives for the first phase were achieved. A number of transducer probes were made and tested. One version only drills, and the other will actually provide a small core from a rock. Because of a more efficient transducer/probe, it will run at very low power (less than 5 Watts) and still drill/core. The prototype generator was built to allow for variation of all the performance-effecting elements of the transducer/probe/end effector, i.e., pulse, duty cycle, frequency, etc. The heart of the circuitry is what will be converted to a surface mounted board for the next phase, after all the parameters have been optimized and the microprocessor feedback can be installed.

  14. Petrology and physical conditions of metamorphism of calcsilicate rocks from low- to high-grade transition area, Dharmapuri District, Tamil Nadu

    NASA Technical Reports Server (NTRS)

    Narayana, B. L.; Natarajan, R.; Govil, P. K.

    1988-01-01

    Calc-silicate rocks comprising quartz, plagioclase, diopside, sphene, scapolite, grossularite-andradite and wollastonite occur as lensoid enclaves within the greasy migmatitic and charnockitic gneisses of the Archaean amphibolite- to granulite-facies transition zone in Dharmapuri district, Tamil Nadu. The calc-silicate rocks are characterized by the absence of K-feldspar and primary calcite, presence of large modal quartz and plagioclase and formation of secondary garnet and zoisite rims around scapolite and wollastonite. The mineral distributions suggest compositional layering. The chemical composition and mineralogy of the calc-silicate rocks indicate that they were derived from impure silica-rich calcareous sediments whose composition is similar to that of pelite-limestone mixtures. From the mineral assemblages the temperature, pressure and fluid composition during metamorphism were estimated. The observed mineral reaction sequences require a range of X sub CO2 values demonstrating that an initially CO2-rich metamorphic fluid evolved with time towards considerably more H2O-rich compositions. These variations in fluid composition suggest that there were sources of water-rich fluids external to the calc-silicate rocks and that mixing of these fluids with those of calc-silicate rocks was important in controlling fluid composition in calc-silicate rocks and some adjacent rock types as well.

  15. Interpreting the 10 micron Astronomical Silicate Feature

    NASA Astrophysics Data System (ADS)

    Bowey, Janet E.

    1998-11-01

    10micron spectra of silicate dust in the diffuse medium towards Cyg OB2 no. 12 and towards field and embedded objects in the Taurus Molecular Cloud (TMC) were obtained with CGS3 at the United Kingdom Infrared Telescope (UKIRT). Cold molecular-cloud silicates are sampled in quiescent lines of sight towards the field stars Taurus-Elias 16 and Elias 13, whilst observations of the embedded young stellar objects HL Tau, Taurus-Elias 7 (Haro6-10) and Elias 18 also include emission from heated dust. To obtain the foreground silicate absorption profiles, featureless continua are estimated using smoothed astronomical and laboratory silicate emissivities. TMC field stars and Cyg OB2 no. 12 are modelled as photospheres reddened by foreground continuum and silicate extinction. Dust emission in the non-photospheric continua of HL Tau and Elias 7 (Haro6-10) is distinguished from foreground silicate absorption using a 10micron disk model, based on the IR-submm model of T Tauri stars by Adams, Lada & Shu (1988), with terms added to represent the foreground continuum and silicate extinction. The absorption profiles of HL Tau and Elias 7 are similar to that of the field star Elias 16. Fitted temperature indices of 0.43 (HL Tau) and 0.33 (Elias 7) agree with Boss' (1996) theoretical models of the 200-300K region, but are lower than those of IR-submm disks (0.5-0.61; Mannings & Emerson 1994); the modelled 10micron emission of HL Tau is optically thin, that of Elias 7 is optically thick. A preliminary arcsecond-resolution determination of the 10micron emissivity near θ1 Ori D in the Trapezium region of Orion and a range of emission temperatures (225-310K) are derived from observations by T. L. Hayward; this Ney-Allen emissivity is 0.6micron narrower than the Trapezium emissivity obtained by Forrest et al. (1975) with a large aperture. Published interstellar grain models, elemental abundances and laboratory studies of Solar System silicates (IDPs, GEMS and meteorites), the 10micron

  16. Contribution of forests to the carbon sink via biologically-mediated silicate weathering: A case study of China.

    PubMed

    Song, Zhaoliang; Liu, Hongyan; Strömberg, Caroline A E; Wang, Hailong; Strong, Peter James; Yang, Xiaomin; Wu, Yuntao

    2017-09-29

    During silicate weathering, atmospheric carbon dioxide (CO2) is consumed and base cations are released from silicate minerals to form carbonate and bicarbonate ions, which are finally deposited as carbonate complexes. Continental silicate weathering constitutes a stable carbon sink that is an important influence on long-term climate change, as it sequesters atmospheric carbon dioxide at a million-year time scale. Traditionally, CO2 sequestered through silicate weathering is estimated by measuring the flux of the base cations to watersheds. However, plants also absorb considerable amounts of base cations. Plant biomass is often removed from ecosystems during harvesting. The base cations are subsequently released after decomposition of the harvested plant materials, and thereby enhance CO2 consumption related to weathering. Here, we analyze plant biomass storage-harvest fluxes (production and removal of biomass from forests) of base cations in forests across China to quantify the relative contribution of forest trees to the terrestrial weathering-related carbon sink. Our data suggest that the potential CO2 consumption rate for biomass-related silicate weathering (from the combined action of with afforestation/reforestation, controlled harvesting and rock powder amendment) in Chinese forests is 7.9±4.1Tg CO2yr(-1). This represents ~34% of the chemical weathering rate in China. Globally, forests may increase CO2 sequestration through biologically-mediated silicate weathering by ~32%. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. A framework for predicting global silicate weathering and CO2 drawdown rates over geologic time-scales

    PubMed Central

    Hilley, George E.; Porder, Stephen

    2008-01-01

    Global silicate weathering drives long-time-scale fluctuations in atmospheric CO2. While tectonics, climate, and rock-type influence silicate weathering, it is unclear how these factors combine to drive global rates. Here, we explore whether local erosion rates, GCM-derived dust fluxes, temperature, and water balance can capture global variation in silicate weathering. Our spatially explicit approach predicts 1.9–4.6 × 1013 mols of Si weathered globally per year, within a factor of 4–10 of estimates of global silicate fluxes derived from riverine measurements. Similarly, our watershed-based estimates are within a factor of 4–18 (mean of 5.3) of the silica fluxes measured in the world's ten largest rivers. Eighty percent of total global silicate weathering product traveling as dissolved load occurs within a narrow range (0.01–0.5 mm/year) of erosion rates. Assuming each mol of Mg or Ca reacts with 1 mol of CO2, 1.5–3.3 × 108 tons/year of CO2 is consumed by silicate weathering, consistent with previously published estimates. Approximately 50% of this drawdown occurs in the world's active mountain belts, emphasizing the importance of tectonic regulation of global climate over geologic timescales. PMID:18952842

  18. A framework for predicting global silicate weathering and CO2 drawdown rates over geologic time-scales.

    PubMed

    Hilley, George E; Porder, Stephen

    2008-11-04

    Global silicate weathering drives long-time-scale fluctuations in atmospheric CO(2). While tectonics, climate, and rock-type influence silicate weathering, it is unclear how these factors combine to drive global rates. Here, we explore whether local erosion rates, GCM-derived dust fluxes, temperature, and water balance can capture global variation in silicate weathering. Our spatially explicit approach predicts 1.9-4.6 x 10(13) mols of Si weathered globally per year, within a factor of 4-10 of estimates of global silicate fluxes derived from riverine measurements. Similarly, our watershed-based estimates are within a factor of 4-18 (mean of 5.3) of the silica fluxes measured in the world's ten largest rivers. Eighty percent of total global silicate weathering product traveling as dissolved load occurs within a narrow range (0.01-0.5 mm/year) of erosion rates. Assuming each mol of Mg or Ca reacts with 1 mol of CO(2), 1.5-3.3 x 10(8) tons/year of CO(2) is consumed by silicate weathering, consistent with previously published estimates. Approximately 50% of this drawdown occurs in the world's active mountain belts, emphasizing the importance of tectonic regulation of global climate over geologic timescales.

  19. Hydrogen isotope fractionation and redox-controlled solution mechanisms in silicate-COH melt + fluid systems

    NASA Astrophysics Data System (ADS)

    Mysen, Bjorn

    2015-11-01

    The behavior of volatiles in silicate-COH melts and fluids and hydrogen isotope fractionation between melt and fluid were determined experimentally to advance our understanding of the role of volatiles in magmatic processes. Experiments were conducted in situ while the samples were at the desired temperature and pressure to 825°C and ~1.6 GPa and with variable redox conditions. Under oxidizing conditions, melt and fluid comprised CO2, CO3, HCO3, OH, H2O, and silicate components, whereas under reducing conditions, the species were CH4, H2, H2O, and silicate components. Temperature-dependent hydrogen isotope exchange among structural entities within coexisting fluids and melts yields ΔH values near 14 and 24 kJ/mol and -5 and -1 kJ/mol under oxidizing and reducing conditions, respectively. This temperature (and probably pressure)-dependent D/H fractionation is because of interaction between D and H and silicate and C-bearing species in silicate-saturated fluids and in COH fluid-saturated melts. The temperature- and pressure-dependent D/H fractionation factors suggest that partial melts in the presence of COH volatiles in the upper mantle can have δD values 100% or more lighter relative to coexisting silicate-saturated fluid. This effect is greater under oxidizing than under reducing conditions. It is suggested that δD variations of upper mantle mid-ocean ridge basalt (MORB) sources, inferred from the δD of MORB magmatic rocks, can be explained by variations in redox conditions during melting. Lower δD values of the MORB magma reflect more reducing conditions in the mantle source.

  20. Isotopic heterogeneity in volcanic rocks

    NASA Astrophysics Data System (ADS)

    Wolff, J. A.; Ramos, F. C.; Tollstrup, D. L.

    2003-04-01

    The growing microsample database on volcanic rocks is showing that isotopic disequilibrium between and among phenocryst phases, their melt inclusions, and groundmass is the rule rather than the exception. This applies even in cases of little or no petrographic evidence for disequilibrium. Erupted magmas must therefore be regarded, to some extent, as mechanical mixtures of isotopically distinct components assembled from different sources. The preservation of isotopic disequilibrium requires that the assembly takes place before diffusion can eradicate evidence of disequilibrium. For a wide range of magmas (mafic, intermediate and felsic, silica under- and oversaturated) from different volcano types (flood basalts, monogenetic cones, stratocones, silicic calderas) this timescale ranges from thousands of years down to one year or less, with no consistent pattern of mixing-to-eruption time vs. volcano or magma type. Among many issues arising from these findings, we note that estimation of magmatic temperatures from application of equilibrium thermodynamics to phenocryst assemblages in volcanic rocks should be approached with extreme caution. The isotope ratio variations observed among the components of a single volcanic rock sample, in most cases, indicate interaction between magma and the local wall-rock. This is consistent with the view that the vast majority of magmas undergo modification during transport through and residence within the crust. Three physical origins of heterogeneity have been proposed: melting of wallrock, magmatic recharge, and mixing of components within a magma chamber initially segregated into melt-rich and crystal-rich portions. Time constraints on preservation of disequilibrium imply either a causal link with eruption, or that these processes occur through the lifetime of a chamber.

  1. Dynamic crystallization of silicate melts

    NASA Technical Reports Server (NTRS)

    Russell, W. J.

    1984-01-01

    Two types of furnaces with differing temperature range capabilities were used to provide variations in melt temperatures and cooling rates in a study of the effects of heterogeneous nucleation on crystallization. Materials of chondrule composition were used to further understanding of how the disequilibrium features displayed by minerals in rocks are formed. Results show that the textures of natural chondrules were duplicated. It is concluded that the melt history is dominant over cooling rate and composition in controlling texture. The importance of nuclei, which are most readily derived from preexisting crystalline material, support an origin for natural chondrules based on remelting of crystalline material. This would be compatible with a simple, uniform chondrule forming process having only slight variations in thermal histories resulting in the wide range of textures.

  2. Rock comminution as a source of hydrogen for subglacial ecosystems

    NASA Astrophysics Data System (ADS)

    Telling, J.; Boyd, E. S.; Bone, N.; Jones, E. L.; Tranter, M.; Macfarlane, J. W.; Martin, P. G.; Wadham, J. L.; Lamarche-Gagnon, G.; Skidmore, M. L.; Hamilton, T. L.; Hill, E.; Jackson, M.; Hodgson, D. A.

    2015-11-01

    Substantial parts of the beds of glaciers, ice sheets and ice caps are at the pressure melting point. The resulting water harbours diverse subglacial microbial ecosystems capable of affecting global biogeochemical cycles. Such subglacial habitats may have acted as refugia during Neoproterozoic glaciations. However, it is unclear how life in subglacial environments could be supported during glaciations lasting millions of years because energy from overridden organic carbon would become increasingly depleted. Here we investigate the potential for abiogenic H2 produced during rock comminution to provide a continual source of energy to support subglacial life. We collected a range of silicate rocks representative of subglacial environments in Greenland, Canada, Norway and Antarctica and crushed them with a sledgehammer and ball mill to varying surface areas. Under an inert atmosphere in the laboratory, we added water, and measured H2 production with time. H2 was produced at 0 °C in all silicate-water experiments, probably through the reaction of water with mineral surface silica radicals formed during rock comminution. H2 production increased with increasing temperature or decreasing silicate rock grain size. Sufficient H2 was produced to support previously measured rates of methanogenesis under a Greenland glacier. We conclude that abiogenic H2 generation from glacial bedrock comminution could have supported life and biodiversity in subglacial refugia during past extended global glaciations.

  3. Rock type identification and abundance estimation from hyperspectral analysis

    NASA Astrophysics Data System (ADS)

    Feng, Jilu

    This study explores the usefulness of hyperspectral data to discriminate rock units and estimate the abundance of sulfides in rocks. Airborne visible-near infrared (VIS-NIR) hyperspectral data collected from northern Cape Smith, Quebec and laboratory thermal infrared reflectance (TIR) data measured on rock samples from eight different mines in the Sudbury Basin, Ontario are involved in the analysis. The study addressed four different geological application scenarios with the aim of retrieving useful lithological information from rock spectra while minimizing the influence of varying environmental factors. The research first examines the effects of topography on the selection of rock endmembers from airborne VIS_NIR spectra and demonstrates how a topographic correction process can improve the discrimination of rock units. It demonstrates that traditional ways of selecting spectral endmembers from hyperspectral data for areas of rugged terrain cannot provide representative rock unit signatures. The second part of the research targeted the mapping of wall rock in an underground environment using TIR spectra. Rock samples from mines of the Sudbury Basin in Ontario were measured using naturally broken surfaces both dry and wet to address environmental conditions encountered underground. An innovative method applying a spectral angle mapper on the 2nd derivative of rock spectra from 700--1300 cm-1 was proved to be robust to remove the effect of liquid water, local geometry and disseminated sulfide ores while preserving diagnostic rock signatures for mapping. The study then focuses on retrieving sulfide information from TIR to estimate ore (total sulfide abundance) grade on naturally broken rock faces and separate ore-bearing rocks from their host rocks in an underground environment regardless of rock types. An important finding is that reflectance at 1319 cm -1, where most silicate rocks demonstrate low reflectance, is related to total sulfide concentration in rocks

  4. A Rock Encyclopedia That Includes Rock Samples.

    ERIC Educational Resources Information Center

    Laznicka, Peter

    1981-01-01

    Described is a rock encyclopedia combining rock sample sets and encyclopedic word and picture entries which can be used as a realistic information resource for independent study or as a part of a course. (JT)

  5. Lunar Rocks

    NASA Technical Reports Server (NTRS)

    1969-01-01

    The second manned lunar landing mission, Apollo 12 launched from launch pad 39-A at Kennedy Space Center in Florida on November 14, 1969 via a Saturn V launch vehicle. The Saturn V vehicle was developed by the Marshall Space Flight Center (MSFC) under the direction of Dr. Wernher von Braun. Aboard Apollo 12 was a crew of three astronauts: Alan L. Bean, pilot of the Lunar Module (LM), Intrepid; Richard Gordon, pilot of the Command Module (CM), Yankee Clipper; and Spacecraft Commander Charles Conrad. The LM, Intrepid, landed astronauts Conrad and Bean on the lunar surface in what's known as the Ocean of Storms while astronaut Richard Gordon piloted the CM, Yankee Clipper, in a parking orbit around the Moon. Lunar soil activities included the deployment of the Apollo Lunar Surface Experiments Package (ALSEP), finding the unmanned Surveyor 3 that landed on the Moon on April 19, 1967, and collecting 75 pounds (34 kilograms) of rock samples, some of which can be seen in this photograph. Apollo 12 safely returned to Earth on November 24, 1969.

  6. Molybdenum Valence in Basaltic Silicate Melts

    NASA Technical Reports Server (NTRS)

    Danielson, L. R.; Righter, K.; Newville, M.; Sutton, S.; Pando, K.

    2010-01-01

    The moderately siderophile element molybdenum has been used as an indicator in planetary differentiation processes, and is particularly relevant to core formation [for example, 1-6]. However, models that apply experimental data to an equilibrium differentiation scenario infer the oxidation state of molybdenum from solubility data or from multivariable coefficients from metal-silicate partitioning data [1,3,7]. Partitioning behavior of molybdenum, a multivalent element with a transition near the J02 of interest for core formation (IW-2) will be sensitive to changes in JO2 of the system and silicate melt structure. In a silicate melt, Mo can occur in either 4+ or 6+ valence state, and Mo6+ can be either octahedrally or tetrahedrally coordinated. Here we present first XANES measurements of Mo valence in basaltic run products at a range of P, T, and JO2 and further quantify the valence transition of Mo.

  7. Hydrothermal Synthesis of Dicalcium Silicate Based Cement

    NASA Astrophysics Data System (ADS)

    Dutta, N.; Chatterjee, A.

    2017-06-01

    It is imperative to develop low energy alternative binders considering the large amounts of energy consumed as well as carbon dioxide emissions involved in the manufacturing of ordinary Portland cement. This study is on the synthesis of a dicalcium silicate based binder using a low temperature hydrothermal route.The process consists of synthesizing an intermediate product consisting of a calcium silicate hydrate phase with a Ca:Si ratio of 2:1 and further thermal treatment to produce the β-Ca2SiO4 (C2S) phase.Effect of various synthesis parameters like water to solid ratio, dwell time and temperature on the formation of the desired calcium silicate hydrate phase is reported along with effect of heating conditions for formation of the β-C2S phase. Around 77.45% of β-C2S phase was synthesized by thermal treatment of the intermediate phase at 820°C.

  8. ROCK PHYSICS. Rock physics of fibrous rocks akin to Roman concrete explains uplifts at Campi Flegrei Caldera.

    PubMed

    Vanorio, Tiziana; Kanitpanyacharoen, Waruntorn

    2015-08-07

    Uplifts in the Campi Flegrei caldera reach values unsurpassed anywhere in the world (~2 meters). Despite the marked deformation, the release of strain appears delayed. The rock physics analysis of well cores highlights the presence of two horizons, above and below the seismogenic area, underlying a coupled process. The basement is a calc-silicate rock housing hydrothermal decarbonation reactions, which provide lime-rich fluids. The caprock above the seismogenic area has a pozzolanic composition and a fibril-rich matrix that results from lime-pozzolanic reactions. These findings provide evidence for a natural process reflecting that characterizing the cementitious pastes in modern and Roman concrete. The formation of fibrous minerals by intertwining filaments confers shear and tensile strength to the caprock, contributing to its ductility and increased resistance to fracture.

  9. Core formation in silicate bodies

    NASA Astrophysics Data System (ADS)

    Nimmo, F.; O'Brien, D. P.; Kleine, T.

    2008-12-01

    Differentiation of a body into a metallic core and silicate mantle occurs most efficiently if temperatures are high enough to allow at least the metal to melt [1], and is enhanced if matrix deformation occurs [2]. Elevated temperatures may occur due to either decay of short-lived radio-isotopes, or gravitational energy release during accretion [3]. For bodies smaller than the Moon, core formation happens primarily due to radioactive decay. The Hf-W isotopic system may be used to date core formation; cores in some iron meteorites and the eucrite parent body (probably Vesta) formed within 1 My and 1-4~My of solar system formation, respectively [4]. These formation times are early enough to ensure widespread melting and differentiation by 26Al decay. Incorporation of Fe60 into the core, together with rapid early mantle solidification and cooling, may have driven early dynamo activity on some bodies [5]. Iron meteorites are typically depleted in sulphur relative to chondrites, for unknown reasons [6]. This depletion contrasts with the apparently higher sulphur contents of cores in larger planetary bodies, such as Mars [7], and also has a significant effect on the timing of core solidification. For bodies of Moon-size and larger, gravitational energy released during accretion is probably the primary cause of core formation [3]. The final stages of accretion involve large, stochastic collisions [8] between objects which are already differentiated. During each collision, the metallic cores of the colliding objects merge on timescales of a few hours [9]. Each collision will reset the Hf-W isotopic signature of both mantle and core, depending on the degree to which the impactor core re-equilibrates with the mantle of the target [10]. The re-equilibration efficiency depends mainly on the degree to which the impactor emulsifies [11], which is very uncertain. Results from N-body simulations [8,12] suggest that significant degrees of re- equilibration are required [4,10]. Re

  10. Formation of a low-crystalline Zn-silicate in a stream in SW Sardinia, Italy

    USGS Publications Warehouse

    Wanty, Richard B.; De Giudici, G.; Onnis, P.; Rutherford, D.; Kimball, B.A.; Podda, F.; Cidu, R.; Lattanzi, P.; Medas, D.

    2013-01-01

    n southwestern Sardinia, Italy, the Rio Naracauli drains a catchment that includes several abandoned mines. The drainage from the mines and associated waste rocks has led to extreme concentrations of dissolved Zn, but because of the near-neutral pH, concentrations of other metals remain low. In the reach from approximately 2300 to 3000 m downstream from the headwaters area, an amorphous Zn-silicate precipitates from the water. In this reach, concentrations of both Zn and silica remain nearly constant, but the loads (measured in mass/time) of both increase, suggesting that new Zn and silica are supplied to the stream, likely from emerging groundwater. Zinc isotope signatures of the solid are heavier than the dissolved Zn by about 0.5 permil in 66/64Zn, suggesting that an extracellular biologically mediated adsorption process may be involved in the formation of the Zn-silicate.

  11. Zircon from historic eruptions in Iceland: Reconstructing storage and evolution of silicic magmas

    USGS Publications Warehouse

    Carley, T.L.; Miller, C.F.; Wooden, J.L.; Bindeman, I.N.; Barth, A.P.

    2011-01-01

    Zoning patterns, U-Th disequilibria ages, and elemental compositions of zircon from eruptions of Askja (1875 AD), Hekla (1158 AD), ??r??faj??kull (1362 AD) and Torfaj??kull (1477 AD, 871 AD, 3100 BP, 7500 BP) provide insights into the complex, extended, histories of silicic magmatic systems in Iceland. Zircon compositions, which are correlated with proximity to the main axial rift, are distinct from those of mid-ocean ridge environments and fall at the low-Hf edge of the range of continental zircon. Morphology, zoning patterns, compositions, and U-Th ages all indicate growth and storage in subvolcanic silicic mushes or recently solidified rock at temperatures above the solidus but lower than that of the erupting magma. The eruptive products were likely ascending magmas that entrained a zircon "cargo" that formed thousands to tens of thousands of years prior to the eruptions. ?? 2011 Springer-Verlag.

  12. Experimental modeling of the interaction of subducted carbonates and sulfur with mantle silicates

    NASA Astrophysics Data System (ADS)

    Bataleva, Yu. V.; Palyanov, Yu. N.; Borzdov, Yu. M.; Zdrokov, E. V.; Sobolev, N. V.

    2016-09-01

    Experimental studies in the system Fe,Ni-olivine-carbonate-S ( P = 6.3 GPa, T = 1050-1550°C, t = 40-60 h) aimed at modeling of the interaction of subducted carbonates and sulfur with rocks of the silicate mantle and at investigation of the likely mechanism of the formation of mantle sulfides were performed. It is shown that an association of olivine + orthopyroxene + magnesite + pyrite coexisting with a sulfur melt/fluid with dissolved Fe, Ni, and O is formed at T ≤ 1250°C. An association of low-Fe olivine, orthopyroxene, and magnesite and two immiscible melts of the carbonate and S-Fe-Ni-O compositions are formed at T ≥ 1350°C. It is shown that the reduced S-bearing fluids may transform silicates and carbonates, extract metals from the solid-phase matrix, and provide conditions for generation of sulfide melts.

  13. Making Earth's earliest continental crust - an analogue from voluminous Neogene silicic volcanism in NE-Iceland

    NASA Astrophysics Data System (ADS)

    Berg, Sylvia E.; Troll, Valentin R.; Burchardt, Steffi; Riishuus, Morten S.; Deegan, Frances M.; Harris, Chris; Whitehouse, Martin J.; Gústafsson, Ludvik E.

    2014-05-01

    Borgarfjörður Eystri in NE-Iceland represents the second-most voluminous exposure of silicic eruptive rocks in Iceland and is a superb example of bimodal volcanism (Bunsen-Daly gap), which represents a long-standing controversy that touches on the problem of crustal growth in early Earth. The silicic rocks in NE-Iceland approach 25 % of the exposed rock mass in the region (Gústafsson et al., 1989), thus they significantly exceed the usual ≤ 12 % in Iceland as a whole (e.g. Walker, 1966; Jonasson, 2007). The origin, significance, and duration of the voluminous (> 300 km3) and dominantly explosive silicic activity in Borgarfjörður Eystri is not yet constrained (c.f. Gústafsson, 1992), leaving us unclear as to what causes silicic volcanism in otherwise basaltic provinces. Here we report SIMS zircon U-Pb ages and δ18O values from the region, which record the commencement of silicic igneous activity with rhyolite lavas at 13.5 to 12.8 Ma, closely followed by large caldera-forming ignimbrite eruptions from the Breiðavik and Dyrfjöll central volcanoes (12.4 Ma). Silicic activity ended abruptly with dacite lava at 12.1 Ma, defining a ≤ 1 Myr long window of silicic volcanism. Magma δ18O values estimated from zircon range from 3.1 to 5.5 (± 0.3; n = 170) and indicate up to 45 % assimilation of a low-δ18O component (e.g. typically δ18O = 0 ‰, Bindeman et al., 2012). A Neogene rift relocation (Martin et al., 2011) or the birth of an off-rift zone to the east of the mature rift associated with a thermal/chemical pulse in the Iceland plume (Óskarsson & Riishuus, 2013), likely brought mantle-derived magma into contact with fertile hydrothermally-altered basaltic crust. The resulting interaction triggered large-scale crustal melting and generated mixed-origin silicic melts. Such rapid formation of silicic magmas from sustained basaltic volcanism may serve as an analogue for generating continental crust in a subduction-free early Earth (e.g. ≥ 3 Ga, Kamber et

  14. Mafic silicates in the Orgueil carbonaceous meteorite

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.; Macdougall, J. D.

    1976-01-01

    Iron-bearing olivines and pyroxenes occurring in Orgueil may represent a separate population distinct from the magnesian varieties previously reported. Compositions of these iron-bearing silicates are inconsistent with an origin by direct equilibrium condensation in the nebula. Such an origin is more plausible for the magnesian silicates, but lacks conclusive evidence. An extra-solar system origin for either mafic population is possible, though similarly lacking in evidence. About 15% of the olivines, randomly distributed with respect to iron content, retain particle track evidence of a precompaction irradiation.

  15. Statistics of silicate units in binary glasses.

    PubMed

    Gaddam, Anuraag; Montagne, Lionel; Ferreira, José M F

    2016-09-28

    In this paper, we derive a new model to determine the distribution of silicate units in binary glasses (or liquids). The model is based on statistical mechanics and assumes grand canonical ensemble of silicate units which exchange energy and network modifiers from the reservoir. This model complements experimental techniques, which measure short range order in glasses such as nuclear magnetic resonance (NMR) spectroscopy. The model has potential in calculating the amounts of liquid-liquid phase segregation and crystal nucleation, and it can be easily extended to more complicated compositions. The structural relaxation of the glass as probed by NMR spectroscopy is also reported, where the model could find its usefulness.

  16. Hydrothermal synthesis of ytterbium silicate nanoparticles.

    PubMed

    Chen, Hongfei; Gao, Yanfeng; Liu, Yun; Luo, Hongjie

    2010-02-15

    A simple, low-cost hydrothermal method was developed to synthesize 20-nm-diameter single-crystalline ytterbium silicate (Yb(2)Si(2)O(7) and Yb(2)SiO(5)) nanoparticles at 200 degrees C. This is nearly 1000 degrees C lower than that for the typical sol-gel route to ytterbium silicate powders. Obtained powders showed very low thermal conductivity, a suitable thermal expansion coefficient, and excellent thermal/structural stability, suggesting a potential application to environmental and thermal barrier coatings. Special focus was placed on assessing the hydrothermal reaction mechanism for particle formation.

  17. Paleomagnetism and paleointensity recorded by single silicate crystals

    NASA Astrophysics Data System (ADS)

    Tarduno, J. A.

    2008-12-01

    Silicate minerals can contain minute magnetic inclusions that are well suited as recorders of the ancient magnetic field. In a magnetic hysteresis survey of natural minerals in 1997-1998, workers in the University of Rochester lab found that natural olivine and pyroxene separated from mafic lavas tended to contain multi- domain magnetic inclusions, whereas plagioclase feldspars hosted smaller single domain particles. These findings led to Thellier analyses of plagioclase crystals to define field strength for reversing and non- reversing (i.e. Superchron) time intervals; data available to date support an inverse relationship between field strength and reversal rate suggested by Cox (1968) and seen in some numerical simulations of the geodynamo that call upon mantle forcing. A key part of these studies are comparisons of single crystals and whole rock results; these show that bulk lava samples are often biased by alteration on geologic and laboratory time scales, and by the presence of non-ideal carriers. I will review the status of our efforts to further constrain field strength versus reversal rate, and the special challenges posed in the investigation of the earliest magnetic field. The latter work has motivated the development of new heating techniques and a further exploration of silicate carriers of magnetization. Although technically challenging, these studies have yielded the oldest field strength record based on a TRM (i.e. the field was within 50% of the modern value 3.2 billion-years-ago). Efforts to test for the presence of an even older dynamo will be discussed.

  18. Lithium isotopes in speleothems: Temperature-controlled variation in silicate weathering during glacial cycles

    NASA Astrophysics Data System (ADS)

    Pogge von Strandmann, Philip A. E.; Vaks, Anton; Bar-Matthews, Miryam; Ayalon, Avner; Jacob, Ezekiel; Henderson, Gideon M.

    2017-07-01

    Terrestrial chemical weathering of silicate minerals is a fundamental component of the global cycle of carbon and other elements. Past changes in temperature, rainfall, ice cover, sea-level and physical erosion are thought to affect weathering but the relative impact of these controls through time remains poorly constrained. This problem could be addressed if the nature of past weathering could be constrained at individual sites. In this study, we investigate the use of speleothems as local recorders of the silicate weathering proxy, Li isotopes. We analysed δ7 Li and [Li] in speleothems that formed during the past 200 ka in two well-studied Israeli caves (Soreq and Tzavoa), as well as in the overlying soils and rocks. Leaching and mass balance of these soils and rocks show that Li is dominantly sourced from weathering of the overlying aeolian silicate soils. Speleothem δ7 Li values are ubiquitously higher during glacials (∼23‰) than during interglacials (∼10‰), implying more congruent silicate weathering during interglacials (where ;congruent; means a high ratio of primary mineral dissolution to secondary mineral formation). These records provide information on the processes controlling weathering in Israel. Consideration of possible processes causing this change of weathering congruency indicates a primary role for temperature, with higher temperatures causing more congruent weathering (lower δ7Lispeleo). The strong relationship observed between speleothem δ7 Li and climate at these locations suggests that Li isotopes may be a powerful tool with which to understand the local controls on weathering at other sites, and could be used to assess the distribution of weathering changes accompanying climate change, such as that of Pleistocene glacial cycles.

  19. Geochemistry of large river suspended sediments: Silicate weathering or recycling tracer?

    SciTech Connect

    Gaillardet, J.; Dupre, B.; Allegre, C.J.

    1999-12-01

    This study focuses on the major and trace element composition of suspended sediments transported by the world's largest rivers. Its main purpose is to answer the following question: is the degree of weathering of modern river-borne particles consistent with the estimated river dissolved loads derived from silicate weathering? In agreement with the well known mobility of elements during weathering of continental rocks, the authors confirm that river sediments are systematically depleted in Na, K, Ba with respect to the Upper Continental Crust. For each of these mobile elements, a systematics of weathering indexes of river-borne solids is attempted. A global consistency is found between all these indexes. Important variations in weathering intensities exist. A clear dependence of weathering intensities with climate is observed for the rivers draining mostly lowlands. However, no global correlation exists between weathering intensities and climatic or relief parameters because the trend observed for lowlands is obscured by rivers draining orogenic zones. An inverse correlation between weathering intensities and suspended sediment concentrations is observed showing that the regions having the highest rates of physical denudation produce the least weathered sediments. Finally, chemical and physical weathering are compared through the use of a simple steady state model. The authors show that the weathering intensities of large river suspended sediments can only be reconciled with the (silicate-derived) dissolved load or rivers, by admitting that most of the continental rocks submitted to weathering in large river basins have already suffered previous weathering cycles. A simple graphical method is proposed for calculating the proportion of sedimentary recycling in large river basins. Finally, even if orogenic zones produce weakly weathered sediments, the authors emphasize the fact that silicate chemical weathering rates (and hence CO{sub 2} consumption rates by silicate

  20. The Lassell Massif - a Silicic Lunar Volcano

    NASA Astrophysics Data System (ADS)

    Ashley, J.; Robinson, M. S.; Stopar, J. D.; Glotch, T. D.; Hawke, B. R.; Lawrence, S. J.; Jolliff, B. L.; Greenhagen, B. T.; Paige, D. A.

    2013-12-01

    Lunar volcanic processes were dominated by mare-producing basaltic extrusions. However, limited occurrences of non-mare, geochemically evolved (Si-enriched) volcanic deposits have long been suspected on the basis of spectral anomalies (red spots), landform morphologies, and the occurrence of minor granitic components in Apollo sample suites [e.g., 1-5]. The LRO Diviner Lunar Radiometer Experiment (Diviner) measured thermal emission signatures considered diagnostic of highly silicic rocks in several red spot areas [6,7], within the Marius domes [8], and from the Compton-Belkovich feature on the lunar farside [9]. The present study focuses on the Lassell massif red spot (14.73°S, 350.97°E) located in northeastern Mare Nubium near the center of Alphonsus A crater. Here we use Diviner coverage co-projected with Lunar Reconnaissance Orbiter Camera (LROC) images [10] and digital elevation models to characterize the Lassell massif geomorphology and composition. Localized Diviner signatures indicating relatively high silica contents correlate with spatially distinct morphologic features across the Lassell massif. These features include sub-kilometer scale deposits with clear superposing relationships between units of different silica concentrations. The zone with the strongest signal corresponds to the southern half of the massif and the Lassell G and K depressions (formerly thought to be impact craters [11]). These steep-walled pits lack any obvious raised rims or ejecta blankets that would identify them as impact craters; they are likely explosive volcanic vents or collapse calderas. This silica-rich area is contained within the historic red spot area [4], but does not appear to fully overlap with it, implying compositionally distinct deposits originating from the same source region. Low-reflectance deposits, exposed by impact craters and mass wasting across the massif, suggest either basaltic pyroclastics or minor late-stage extrusion of basaltic lavas through vents

  1. New insights on the occurrence of peperites and sedimentary deposits within the silicic volcanic sequences of the Paraná Magmatic Province, Brazil

    NASA Astrophysics Data System (ADS)

    Luchetti, A. C. F.; Nardy, A. J. R.; Machado, F. B.; Madeira, J.; Arnosio, J. M.

    2013-12-01

    In the Paraná Basin (southern and southeastern Brazil), the stratigraphy of the Paraná Magmatic Province (PMP) is composed of a thick (up to 1600 m) volcanic sequence formed by a succession of petrographically and geochemically distinct units of basic and acidic composition. The whole package may have been emplaced in approximately 3 million yr of almost uninterrupted activity. A few aeolian sandstone layers, indicating arid environmental conditions (Botucatu Formation), are interlayered in the lower basalts. Above the basalts, the Palmas and Chapecó Members of the Early Cretaceous Serra Geral Formation, are composed of silicic volcanic rocks (trachydacites, dacites, rhyolites, and rhyodacites) and basalts. This paper presents new evidence of episodes of sedimentation separating silicic volcanic events, expressed by occurrences of sedimentary deposits. Interaction between the volcanic bodies and the coeval unconsolidated sediments formed peperites. The sediments were observed between basaltic lava flows and silicic rocks or interlayered in the Palmas type rocks, between Chapecó type rocks and underlying basaltic flows, between silicic bodies of Palmas and Chapecó types, and interlayered with Palmas type units. The observed structures indicate that the sediments were still wet and unconsolidated, or weakly consolidated, at the time of volcanism, which coupled with the sediment features reflect environmental conditions that are different from those characterizing the Botucatu arid conditions.

  2. Modern estuarine siliceous spiculites, Tasmania, Australia: A non-polar link to Phanerozoic spiculitic cherts

    NASA Astrophysics Data System (ADS)

    Reid, C. M.; James, N. P.; Kyser, T. K.; Barrett, N.; Hirst, A. J.

    2008-02-01

    Biosiliceous sedimentary rocks are well known from the geologicrecord and many are correctly interpreted to have formed indeep-water or cold-water environments. Shallow non-polar spiculitesare also known from the rock record, yet no modern analog hasbeen documented for such environments. Bathurst Harbour, anestuarine system in southwest Tasmania, provides this much-neededmodern analog. In this system a sharp halocline separates tannin-richlow-salinity surface waters from clear marine bottom waters.Tannins supply few nutrients and substantially reduce lightpenetration to bottom environments, resulting in a thinned photiczone and the mixing of deeper-water sub-photic biotas of softcorals, bryozoans, and sponges with other organisms more typicalof this temperate shallow-water environment. The well-definedhalocline allows a typically marine biota, including echinoderms,to live in bottom waters of this estuarine setting. The bioclasticfactory, producing both carbonate and siliceous particles, existsin marine subphotic bottom waters of incised channel and shallowrocky environments along the shoreline. Extensive organic-richsoft sediments in protected embayments generate few bioclasts,but contain allochthonous sponge spicules transported from theadjacent bioclastic factory. Trapping of organic material withinthe estuarine system lowers sediment pH and promotes dissolutionof carbonate biofragments, resulting in preferential preservationof siliceous sponge spicules. This situation implies that manybiosiliceous neritic deposits in the rock record may be theresult of similar preferential preservation.

  3. Discovery of Ni-smectite-rich saprolite at Loma Ortega, Falcondo mining district (Dominican Republic): geochemistry and mineralogy of an unusual case of "hybrid hydrous Mg silicate - clay silicate" type Ni-laterite

    NASA Astrophysics Data System (ADS)

    Tauler, Esperança; Lewis, John F.; Villanova-de-Benavent, Cristina; Aiglsperger, Thomas; Proenza, Joaquín A.; Domènech, Cristina; Gallardo, Tamara; Longo, Francisco; Galí, Salvador

    2017-07-01

    Hydrous Mg silicate-type Ni-laterite deposits, like those in the Falcondo district, Dominican Republic, are dominated by Ni-enriched serpentine and garnierite. Recently, abundant Ni-smectite in the saprolite zone have been discovered in Loma Ortega, one of the nine Ni-laterite deposits in Falcondo. A first detailed study on these Ni-smectites has been performed (μXRD, SEM, EPMA), in addition to a geochemical and mineralogical characterisation of the Loma Ortega profile (XRF, ICP-MS, XRD). Unlike other smectite occurrences in laterite profiles worldwide, the Loma Ortega smectites are trioctahedral and exhibit high Ni contents never reported before. These Ni-smectites may be formed from weathering of pyroxene and olivine, and their composition can be explained by the mineralogy and the composition of the Al-depleted, olivine-rich parent ultramafic rock. Our study shows that Ni-laterites are mineralogically complex, and that a hydrous Mg silicate ore and a clay silicate ore can be confined to the same horizon in the weathering profile, which has significant implications from a recovery perspective. In accordance, the classification of "hybrid hydrous Mg silicate - clay silicate" type Ni-laterite deposit for Loma Ortega would be more appropriate.

  4. Microfabrics in Siliceous Hotsprings: Yellowstone National Park, Wyoming

    NASA Technical Reports Server (NTRS)

    Guidry, S. A.; Chafetz, H. S.; Westall, F.

    2001-01-01

    Microfabrics shed light on the mechanisms governing siliceous sinter precipitation, the profound effects of microorganisms, as well as a conventional facies model for siliceous hotsprings. Additional information is contained in the original extended abstract.

  5. Microfabrics in Siliceous Hotsprings: Yellowstone National Park, Wyoming

    NASA Technical Reports Server (NTRS)

    Guidry, S. A.; Chafetz, H. S.; Westall, F.

    2001-01-01

    Microfabrics shed light on the mechanisms governing siliceous sinter precipitation, the profound effects of microorganisms, as well as a conventional facies model for siliceous hotsprings. Additional information is contained in the original extended abstract.

  6. Sulfide in the core and the composition of the silicate Earth

    NASA Astrophysics Data System (ADS)

    Burton, K. W.

    2015-12-01

    The chemical composition of the Earth is traditionally explained in terms of evolution from a solar-like composition, similar to that found in primitive 'chondritic' meteorites. It now appears, however, that the silicate Earth is not 'chondritic', but depleted in incompatible elements, including refractory lithophile and heat-producing elements. Either Earth lost material during planet-building due to collisional erosion or else internal differentiation processes produced a hidden reservoir deep in the early Earth. Sulfide in the core may provide a reservoir capable of balancing the composition of the silicate Earth. Recent experimental work suggests that the core contains a significant proportion of sulfide, added during the final stages of accretion and new data suggests that at high pressures sulfide can incorporate a substantial amount of refractory lithophile and heat-producing elements [1]. Pioneering work using the short-lived 146Sm-142Nd system strongly suggests that Earth's silicate mantle is non-chondritic [e.g. 2]. The drawback of such radiogenic isotope systems is that it is not possible to distinguish the fractionation of Sm/Nd that occurs during silicate melting from that occurring during the segregation of a sulfide-melt to form the core. Neodymium stable isotopes have the potential to provide just such a tracer of sulfide segregation, because there is a significant contrast in bonding environment between sulfide and silicate, where heavy isotopes should be preferentially incorporated into high force-constant bonds involving REE3+ (i.e. the silicate mantle). Preliminary data indicate that mantle rocks do indeed possess heavier 146Nd/144Nd values than chondritic meteorites, consistent with the removal of light Nd into sulfide in the core, driving the residual mantle to heavy values. Overall, our isotope and elemental data indicate that the rare earths and other incompatible elements are substantially incorporated into sulfide. While Nd Stable isotope

  7. Metal-silicate partitioning of lithophile elements at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Chidester, B.; Rahman, Z.; Righter, K.; Campbell, A. J.

    2015-12-01

    Trace element abundances in Earth's core were established during core-mantle differentiation and metal-silicate equilibration processes early in the planet's history. The core has been suggested as a possible reservoir in which the presence of nominally lithophile elements can explain the observance of non-chondritic ratios of some of these elements in surface rocks (e.g. Nb/Ta, Th/U and Mg/Si)[1-2]. Additionally, several of these elements (U, Th and K) are long-lived sources of radiogenic heat and could be important for explaining the geomagnetic field early in Earth's history. Based on their metal-silicate partitioning behavior at near ambient conditions, it is frequently assumed that uranium and other strongly lithophile elements are present in the core at only trivial abundances. However, core formation took place at a variety of conditions, reaching pressures and temperatures well above those in which most metal-silicate partitioning measurements were obtained[3]. Here we report metal-silicate partitioning data of lithophile elements such as U and Mg, as well as partially siderophile elements Si and S, at conditions more relevant to metal segregation and core formation in a magma ocean. Laser heated diamond anvil methods were used to obtain pressures of 30-70 GPa and temperatures up to 5200 K. FIB/EM methods were used to section the recovered samples and measure the quenched metal and silicate melt compositions. We find that even strongly lithophile elements such as U and Mg partition measurably into the metal phase under extreme P-T conditions. References: [1]Wade, J. and Wood, B. J., Nature, 109 (2001) [2]Allegre et al. EPSL, 134 (1995) [3]Rubie, et al. Icarus, 248 (2015)

  8. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

  9. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

  10. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

  11. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

  12. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive...

  13. Dynamic Fatigue of a Titanium Silicate Glass

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Nettles, Alan T.; Cagle, Holly A.; Smith, W. Scott (Technical Monitor)

    2002-01-01

    A dynamic fatigue study was performed on a Titanium Silicate Glass in order to assess its susceptibility to delayed failure. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for optical elements made from this material. The material has reasonably good resistance (N=23 to stress corrosion in ambient conditions).

  14. Chemically bonded phospho-silicate ceramics

    DOEpatents

    Wagh, Arun S.; Jeong, Seung Y.; Lohan, Dirk; Elizabeth, Anne

    2003-01-01

    A chemically bonded phospho-silicate ceramic formed by chemically reacting a monovalent alkali metal phosphate (or ammonium hydrogen phosphate) and a sparsely soluble oxide, with a sparsely soluble silicate in an aqueous solution. The monovalent alkali metal phosphate (or ammonium hydrogen phosphate) and sparsely soluble oxide are both in powder form and combined in a stochiometric molar ratio range of (0.5-1.5):1 to form a binder powder. Similarly, the sparsely soluble silicate is also in powder form and mixed with the binder powder to form a mixture. Water is added to the mixture to form a slurry. The water comprises 50% by weight of the powder mixture in said slurry. The slurry is allowed to harden. The resulting chemically bonded phospho-silicate ceramic exhibits high flexural strength, high compression strength, low porosity and permeability to water, has a definable and bio-compatible chemical composition, and is readily and easily colored to almost any desired shade or hue.

  15. Lithium Manganese Silicate Positive Electrode Material

    NASA Astrophysics Data System (ADS)

    Yang, Qiong

    As the fast development of the electronic portable devices and drastic fading of fossil energy sources. The need for portable secondary energy sources is increasingly urgent. As a result, lithium ion batteries are being investigated intensely to meet the performance requirements. Among various electrode materials, the most expensive and capacity limiting component is the positive materials. Based on this, researches have been mostly focused on the development of novel cathode materials with high capacity and energy density and the lithium transition metal orthosilicates have been identified as possible high performance cathodes. Here in, we report the synthesis of a kind of lithium transition metal orthosilicates electrode lithium manganese silicate. Lithium manganese silicate has the advantage of high theoretical capacity, low cost raw material and safety. In this thesis, lithium manganese silicate are prepared using different silicon sources. The structure of silicon sources preferred are examined. Nonionic block copolymers surfactant, P123, is tried as carbon source and mophology directing agent. Lithium manganese silicate's performances are improved by adding P123.

  16. Dopant penetration studies through Hf silicate

    NASA Astrophysics Data System (ADS)

    Quevedo-Lopez, M. A.; Visokay, M. R.; Chambers, J. J.; Bevan, M. J.; LiFatou, A.; Colombo, L.; Kim, M. J.; Gnade, B. E.; Wallace, R. M.

    2005-02-01

    We present a study of the penetration of B, P, and As through Hf silicate (HfSixOy) and the effect of N incorporation in Hf silicate (HfSixOyNz) on dopant penetration from doped polycrystalline silicon capping layers. The extent of penetration through Hf silicate was found to be dependent upon the thermal annealing budget for each dopant investigated as follows: B(T⩾950°C/60s), P(T⩾1000°C/20s), and As (T⩾1050°C/60s). We propose that the enhanced diffusion observed for these dopants in HfSixOy, compared with that of SiO2 films, is related to grain boundary formation resulting from HfSixOy film crystallization. We also find that, as in the case of SiO2, N incorporation inhibits dopant (B, P, and As) diffusion through the Hf silicate and thus penetration into the underlying Si substrate. Only B penetration is clearly observed through HfSiON films for anneals at 1050 °C for durations of 10 s or longer. The calculated B diffusivity through the HfSixOyNz layer is D0=5.2×10-15cm2/s.

  17. Rollerjaw Rock Crusher

    NASA Technical Reports Server (NTRS)

    Peters, Gregory; Brown, Kyle; Fuerstenau, Stephen

    2009-01-01

    The rollerjaw rock crusher melds the concepts of jaw crushing and roll crushing long employed in the mining and rock-crushing industries. Rollerjaw rock crushers have been proposed for inclusion in geological exploration missions on Mars, where they would be used to pulverize rock samples into powders in the tens of micrometer particle size range required for analysis by scientific instruments.

  18. A mid-Permian chert event: widespread deposition of biogenic siliceous sediments in coastal, island arc and oceanic basins

    USGS Publications Warehouse

    Murchey, B.L.; Jones, D.L.

    1992-01-01

    Radiolarian and conodont of Permian siliceous rocks from twenty-three areas in teh the circum-Pacific and Mediterranean regions reveal a widespread Permian Chert Event during the middle Leonardian to Wordian. Radiolarian- and (or) sponge spicule-rich siliceous sediments accumulated beneath high productivity zones in coastal, island arc and oceanic basins. Most of these deposits now crop out in fault-bounded accreted terranes. Biogenic siliceous sediments did not accumulate in terranes lying beneath infertile waters including the marine sequences in terranes of northern and central Alaska. The Permian Chert Event is coeval with major phosphorite deposition along the western margin of Pangea (Phosphoria Formation and related deposits). A well-known analogue for this event is middle Miocene deposition of biogenic siliceous sediments beneath high productivity zones in many parts of the Pacific and concurrent deposition of phosphatic as well as siliceous sediments in basins along the coast of California. Interrelated factors associated with both the Miocene and Permian depositional events include plate reorientations, small sea-level rises and cool polar waters. ?? 1992.

  19. Thermoset polymer-layered silicic acid nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Zhen

    Nanocomposites are formed when phase mixing occurs on a nanometer length scale. Due to the improved phase morphology and interfacial properties, nanocomposites exhibit mechanical properties superior to conventional composites. Toyota researchers first demonstrated that organoclay could be exfoliated in a nylon-6 matrix to greatly improve the thermal and mechanical properties of the polymer, which has resulted in a practical application in the automobile industry. A great deal of research has been conducted on organic-inorganic hybrid composites in which smectite clays are used as reinforcement agents. However, little work has been devoted to derivatives of other layered inorganic solids. In the present work, the first examples of organic polymer-layered silicic acid nanocomposites have been prepared by formation of a cured epoxy polymer network in the presence of organo cation exchange forms of magadiite. The exfoliation of silicate nanolayers in the epoxy matrix was achieved by in-situ intragallery polymerization during the thermosetting process. In general, the tensile properties, solvent resistance, barrier properties and chemical stability of the polymer matrix are greatly improved by the embedded silicate nanolayers when the matrix is flexible (sub-ambient Tg). The improvement of properties are dependent on the silicate loading, the degree of nanolayer separation and interfacial properties. Interestingly, the exfoliation also affects the polymer elasticity in a favorable way. The mechanism leading to nanocomposite formation is proposed. One exfoliated epoxy-magadiite nanocomposite/composition possessed unique transparent optical properties. The exfoliation chemistry was successfully extended to the other members of the layered silicic acid family. A new approach also was developed to prepare thermoset epoxy polymer-layered silicate nanocomposites in which curing agents can be directly intercalated into the intragallery without the need for alkylammonium ions

  20. Accelerated Weathering of Rocks.

    DTIC Science & Technology

    1977-08-01

    Dry tests en polished specimens with alternating heating and co- oling actions; ii) Wet tests in destilled water, with alternating...Rock-type Dry tests KxlO2 Wet tests KxlO2 Sound rock SR 3.64 8.31 Medium altered rock MAR 4.96 31.58 Very altered rock VAR 8.89 116.20 TABLE X...Sound rock SR Medium altered rock Very altered rock" KAR VAR ’ Reflectivity R (%) dry test wet test dry test wet test dry test wet

  1. Physical and chemical weathering. [of Martian surface and rocks

    NASA Technical Reports Server (NTRS)

    Gooding, James L.; Arvidson, Raymond E.; Zolotov, Mikhail IU.

    1992-01-01

    Physical and chemical weathering processes that might be important on Mars are reviewed, and the limited observations, including relevant Viking results and laboratory simulations, are summarized. Physical weathering may have included rock splitting through growth of ice, salt or secondary silicate crystals in voids. Chemical weathering probably involved reactions of minerals with water, oxygen, and carbon dioxide, although predicted products vary sensitively with the abundance and physical form postulated for the water. On the basis of kinetics data for hydration of rock glass on earth, the fate of weathering-rind formation on glass-bearing Martian volcanic rocks is tentatively estimated to have been on the order of 0.1 to 4.5 cm/Gyr; lower rates would be expected for crystalline rocks.

  2. Physical and chemical weathering. [of Martian surface and rocks

    NASA Technical Reports Server (NTRS)

    Gooding, James L.; Arvidson, Raymond E.; Zolotov, Mikhail IU.

    1992-01-01

    Physical and chemical weathering processes that might be important on Mars are reviewed, and the limited observations, including relevant Viking results and laboratory simulations, are summarized. Physical weathering may have included rock splitting through growth of ice, salt or secondary silicate crystals in voids. Chemical weathering probably involved reactions of minerals with water, oxygen, and carbon dioxide, although predicted products vary sensitively with the abundance and physical form postulated for the water. On the basis of kinetics data for hydration of rock glass on earth, the fate of weathering-rind formation on glass-bearing Martian volcanic rocks is tentatively estimated to have been on the order of 0.1 to 4.5 cm/Gyr; lower rates would be expected for crystalline rocks.

  3. High chloride content calcium silicate glasses.

    PubMed

    Chen, Xiaojing; Karpukhina, Natalia; Brauer, Delia S; Hill, Robert G

    2017-03-08

    Chloride is known to volatilize from silicate glass melts and until now, only a limited number of studies on oxychloride silicate glasses have been reported. In this paper we have synthesized silicate glasses that retain large amounts of CaCl2. The CaCl2 has been added to the calcium metasilicate composition (CaO·SiO2). Glasses were produced via a melt quench route and an average of 70% of the chloride was retained after melting. Up to 31.6 mol% CaCl2 has been successfully incorporated into these silicate glasses without the occurrence of crystallization. (29)Si MAS-NMR spectra showed the silicon being present mainly as a Q(2) silicate species. This suggests that chloride formed Cl-Ca(n) species, rather than Si-Cl bonds. Upon increasing the CaCl2 content, the Tg reduced markedly from 782 °C to 370 °C. Glass density and glass crystallization temperature decreased linearly with an increase in the CaCl2 content. However, both linear regressions revealed a breakpoint at a CaCl2 content just below 20 mol%. This might be attributed to a significant change in the structure and is also correlated with the nature of the crystallizing phases formed upon heat treatment. The glasses with less than 19.2 mol% CaCl2 crystallized to wollastonite, whilst the compositions with CaCl2 content equal to or greater than 19.2 mol% are thought to crystallize to CaCl2. In practice, the crystallization of CaCl2 could not occur until the crystallization temperature fell below the melting point of CaCl2. The implications of the results along with the high chloride retention are discussed.

  4. Grain Growth and Silicates in Dense Clouds

    NASA Technical Reports Server (NTRS)

    Pendeleton, Yvonne J.; Chiar, J. E.; Ennico, K.; Boogert, A.; Greene, T.; Knez, C.; Lada, C.; Roellig, T.; Tielens, A.; Werner, M.; Whittet, D.

    2006-01-01

    Interstellar silicates are likely to be a part of all grains responsible for visual extinction (Av) in the diffuse interstellar medium (ISM) and dense clouds. A correlation between Av and the depth of the 9.7 micron silicate feature (measured as optical depth, tau(9.7)) is expected if the dust species are well 'mixed. In the di&se ISM, such a correlation is observed for lines of sight in the solar neighborhood. A previous study of the silicate absorption feature in the Taurus dark cloud showed a tendency for the correlation to break down at high Av (Whittet et al. 1988, MNRAS, 233,321), but the scatter was large. We have acquired Spitzer Infrared Spectrograph data of several lines of sight in the IC 5 146, Barnard 68, Chameleon I and Serpens dense clouds. Our data set spans an Av range between 2 and 35 magnitudes. All lines of sight show the 9.7 micron silicate feature. The Serpens data appear to follow the diffuse ISM correlation line whereas the data for the other clouds show a non-linear correlation between the depth of the silicate feature relative to Av, much like the trend observed in the Taurus data. In fact, it appears that for visual extinctions greater than about 10 mag, tau(9.7) begins to level off. This decrease in the growth of the depth of the 9.7 micron feature with increasing Av could indicate the effects of grain growth in dense clouds. In this poster, we explore the possibility that grain growth causes an increase in opacity (Av) without causing a corresponding increase in tau(9.7).

  5. Silicate Dust in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Xie, Yanxia; Li, Aigen; Hao, Lei

    2017-01-01

    The unification theory of active galactic nuclei (AGNs) hypothesizes that all AGNs are surrounded by an anisotropic dust torus and are essentially the same objects but viewed from different angles. However, little is known about the dust that plays a central role in the unification theory. There are suggestions that the AGN dust extinction law appreciably differs from that of the Galaxy. Also, the silicate emission features observed in type 1 AGNs appear anomalous (i.e., their peak wavelengths and widths differ considerably from that of the Galaxy). In this work, we explore the dust properties of 147 AGNs of various types at redshifts z≲ 0.5, with special attention paid to 93 AGNs that exhibit the 9.7 and 18 μm silicate emission features. We model their silicate emission spectra obtained with the Infrared Spectrograph aboard the Spitzer Space Telescope. We find that 60/93 of the observed spectra can be well explained with “astronomical silicate,” while the remaining sources favor amorphous olivine or pyroxene. Most notably, all sources require the dust to be micron-sized (with a typical size of ∼1.5 ± 0.1 μm), much larger than submicron-sized Galactic interstellar grains, implying a flat or “gray” extinction law for AGNs. We also find that, while the 9.7 μm emission feature arises predominantly from warm silicate dust of temperature T ∼ 270 K, the ∼5–8 μm continuum emission is mostly from carbon dust of T ∼ 640 K. Finally, the correlations between the dust properties (e.g., mass, temperature) and the AGN properties (e.g., luminosity, black hole mass) have also been investigated.

  6. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  7. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  8. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  9. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  10. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Aluminum calcium silicate. 182.2122 Section 182...) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c) Limitations, restrictions, or explanation. This...

  11. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  12. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  13. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  14. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  15. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  16. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  17. 21 CFR 582.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  18. 21 CFR 182.2122 - Aluminum calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  19. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  20. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section...

  1. 40 CFR 721.10495 - Metal silicate (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Metal silicate (generic). 721.10495... Substances § 721.10495 Metal silicate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as metal silicate (PMN P-05-634) is subject...

  2. 40 CFR 721.10495 - Metal silicate (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Metal silicate (generic). 721.10495... Substances § 721.10495 Metal silicate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as metal silicate (PMN P-05-634) is subject...

  3. Simultaneous determination of tantalum and hafnium in silicates by neutron activation analysis

    USGS Publications Warehouse

    Greenland, L.P.

    1968-01-01

    A neutron activation procedure suitable for the routine determination of tantalum and hafnium in silicates is described. The irradiated sample is fused with sodium peroxide and leached, and the insoluble hydroxides are dissolved in dilute hydrofluoric acid-hydrochloric acid. After LaF3 and AgCl scavenges, tantalum and hafnium are separated by anion exchange. Tantalum is obtained radiochemically pure; 233Pa and 95Zr contaminants in the hafnium fraction are resolved by ??-ray spectrometry. The chemical yield of the procedure is detemined after counting by re-irradiation. Values for the 8 U.S. Geological Survey standard rocks are reported. ?? 1968.

  4. Opening-mode fracture in siliceous mudstone at high homologous temperature—effect of surface forces

    NASA Astrophysics Data System (ADS)

    Eichhubl, Peter; Aydin, Atilla; Lore, Jason

    In analogy to high-temperature sintering of ceramics and metal powder compacts, the formation of opening-mode fractures in siliceous mudstone during natural in-situ combustion of hydrocarbons is attributed to contractile surface forces between mineral grains and an interstitial melt phase. A comparison between bulk density increase during sintering and created fracture space indicates that fracturing resulted from contraction of the rock matrix due to porosity reduction, grain-scale mass transfer, and high-temperature mineral formation. It is suggested that contractile surface forces between mineral grains and between mineral grains and pore fluid contribute to subcritical fracture formation under a wide range of subsurface conditions.

  5. A physical basis for remote rock mapping of igneous rocks using spectral variations in thermal infrared emittance

    NASA Technical Reports Server (NTRS)

    Walter, L. S.; Labovitz, M. L.

    1980-01-01

    Results of a theoretical investigation of the relation between spectral features in the 8-12 micrometer region and rock type are presented. Data on compositions of a suite of rocks and measurements of their spectral intensities in 8.2-10.9 and 9.4-12.1 micrometer bands published by Vincent (1973) were subjected to various quantitative procedures. There was no consistent direct relationship between rock group names and the relative spectral intensities. However, there is such a relationship between the Thornton-Tuttle (1960) Differentiation Index and the relative spectral intensities. This relationship is explicable on the basis of the change in average Si-O bond length which is a function of the degree of polymerization of the SiO4 tetrahedra of the silicate minerals in the igneous rocks.

  6. Experimental calibration of a new oxybarometer for silicic magmas based on vanadium partitioning between magnetite and silicate melt

    NASA Astrophysics Data System (ADS)

    Arató, Róbert; Audétat, Andreas

    2017-07-01

    Partition coefficients of vanadium between magnetite and rhyolitic silicate melt, DVmgt/melt, were experimentally determined as a function of oxygen fugacity (0.7-4.0 log units above the fayalite-magnetite-quartz buffer), temperature (800-1000 °C), melt alumina saturation index (ASI = 0.74-1.14), magnetite composition (0.2-14 wt% TiO2) and pressure (1-5 kbar; at H2O saturation). Experiments were performed by equilibrating small (≤20 μm), V-free magnetite grains in V-doped silicate melts (∼100 ppm V) and then analyzing both phases by LA-ICP-MS. Attainment of equilibrium was demonstrated by several reversal experiments. The results suggest that DVmgt/melt depends strongly on fO2, increasing by 1.5-1.7 log units from the MnO-Mn3O4 buffer to the Ni-NiO buffer, and to lesser (but still considerable) extents on melt alumina saturation index (ASI; increasing by 0.3-0.7 log units over 0.4 ASI units) and temperature (increasing by 0.3-0.7 log units over a 200 °C interval at a fixed fO2 buffer). Magnetite composition and melt water content seem to have negligible effects. The data were fitted by the following linear regression equation: in which temperature is given in K, ASI refers to molar Al2O3/(CaO + Na2O + K2O) and ΔFMQ refers to the deviation of fO2 (in log units) from the fayalite-magnetite-quartz buffer. This equation reproduces all of our data within 0.3 log units, and 89% of them within 0.15 log units. The main advantages of this new oxybarometer over classical magnetite-ilmenite oxybarometry are (1) that it can be applied to rocks that do not contain ilmenite, and (2) that it is easier to apply to slowly-cooled rocks such as granites.

  7. Generation of Icelandic rhyolites: silicic lavas from the Torfajökull central volcano

    NASA Astrophysics Data System (ADS)

    Gunnarsson, Björn; Marsh, Bruce D.; Taylor, Hugh P.

    1998-07-01

    The Torfajökull central volcano in south-central Iceland contains the largest volume of exposed silicic extrusives in Iceland (˜225 km 3). Within SW-Torfajökull, postglacial mildly alkalic to peralkalic silicic lavas and lava domes (67-74 wt.% SiO 2) have erupted from a family of fissures 1-2.5 km apart within or just outside a large caldera (12×18 km). The silicic lavas show a fissure-dependent variation in composition, and form five chemically distinct units. The lavas are of low crystallinity (0-7 vol.%) and contain phenocrysts in the following order of decreasing abundance: plagioclase (An 10-40), Na-rich anorthoclase (rocks of broadly intermediate composition. The δ 18O values of the silicic lavas are in the range 3.6-4.4, and these are lower than the δ 18O values of comagmatic, contemporaneous basaltic extrusives within SW-Torfajökull, implying that the former can not be derived from the latter by simple fractional crystallization. FeTi-oxide geothermometry reveals temperatures as low as 750-800°C. To explain the fissure-dependent chemical variations, 18O depletions, low FeTi-oxide temperatures and pervasive crystal-melt disequilibrium, we propose the extraction and collection of small parcels of silicic melt from originally heterogeneous basaltic crustal rock through heterogeneous melting and wall rock collapse (solidification front instability, SFI). The original compositional heterogeneity of the source rock is due to (1) silicic segregations, in the form of pods and lenses characteristically formed in the upper parts of gabbroic intrusives

  8. Scattering from Rock and Rock Outcrops

    DTIC Science & Technology

    2014-09-30

    slope was determined from high-resolution interferometric bathymetry so that the global grazing angle of the 5 ideal mean seafloor could be mapped to...from exposed rock on the seafloor , (i.e., individual rocks and rock outcrops) presents some of the most difficult challenges for modern MCM and ASW...classification tools. Inverse models based on forward models would be essential for using sonar systems for remote sensing of seafloor properties. An

  9. Amorphous Silicates in Primitive Meteoritic Materials: Acfer 094 and IDPs

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Nakamura-Messenger, K.; Messenger, S.; Walker, Robert M.

    2009-01-01

    The abundance of presolar grains is one measure of the primitive nature of meteoritic materials. Presolar silicates are abundant in meteorites whose matrices are dominated by amorphous silicates such as the unique carbonaceous chondrite Acfer 094. Presolar silicates are even more abundant in chondritic-porous interplanetary dust particles (CP-IDPs). Amorphous silicates in the form of GEMS (glass with embedded metal and sulfides) grains are a major component of CP IDPs. We are studying amorphous silicates in Acfer 094 matrix in order to determine whether they are related to the GEMS grains in CPIDPs

  10. Characterizing Amorphous Silicates in Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Fu, X.; Wang, A.; Krawczynski, M. J.

    2015-12-01

    Amorphous silicates are common in extraterrestrial materials. They are seen in the matrix of carbonaceous chondrites as well as in planetary materials. Tagish Lake is one of the most primitive carbonaceous meteorites in which TEM and XRD analyses found evidence for poorly crystalline phyllosilicate-like species; Raman spectra revealed amorphous silicates with variable degree of polymerization and low crystallinity. On Mars, CheMin discovered amorphous phases in all analyzed samples, and poorly crystalline smectite in mudstone samples. These discoveries pose questions on the crystallinity of phyllosilicates found by remote sensing on Mars, which is directly relevant to aqueous alteration during geologic history of Mars. Our goal is to use spectroscopy to better characterize amorphous silicates. We use three approaches: (1) using silicate glasses synthesized with controlled chemistry to study the effects of silicate polymerization and (2) using phyllosilicates synthesized with controlled hydrothermal treatment to study the effect of crystallinity on vibrational spectroscopy, finally (3) to use the developed correlations in above two steps to study amorphous phases in meteorites, and those found in future missions to Mars. In the 1st step, silicate glasses were synthesized from pure oxides in a range of NBO/T ratios (from 0 to 4). Depending on the targeted NBO/T and composition of mixed oxides, temperatures for each experiment fell in a range from 1260 to 1520 °C, run for ~ 4 hrs. The melt was quenched in liquid N2 or water. Homogeneity of glass was checked under optical microscopy. Raman spectra were taken over 100 spots on small chips free of bubbles and crystals. We have observed that accompanying an increase of NBO/T, there is a strengthening and a position shift of the Raman peak near 1000 cm-1 (Si-Onon-bridging stretching mode), and the weakening of broad Raman peaks near 500 cm-1 (ring breathing mode) and 700cm-1 (Si-Obridging-Si mode). We are building the

  11. Viscosity of rock-ice mixtures and applications to the evolution of icy satellites

    NASA Technical Reports Server (NTRS)

    Friedson, A. J.; Stevenson, D. J.

    1983-01-01

    Theory and experiments are used to establish lower and upper bounds on the ratio of actual viscosity to pure ice viscosity for a suspension of rock particles in a water ice matrix. A rheological model for rock-ice mixtures is described, establishing bounds for the range of possible viscosity enhancements provided by a suspension of silicate spheres in an ice matrix. A parametrized thermal convection model is described and used to determine a criterion for criticality, defined as the heat flow and/or silicate volume fraction for which the satellite temperature profile intercepts the melting curve of water ice. The consequences of achieving this critical state are examined, and it is shown that under certain circumstances a 'runaway' differentiation can occur in which the silicates settle to form a core and extensive melting of water ice takes place, the latent heat being supplied by the gravitational energy of differentiation. A possible application of these results to Ganymede and Callisto is described.

  12. Identifying the Crystal Graveyards Remaining After Large Silicic Eruptions

    NASA Astrophysics Data System (ADS)

    Gelman, S. E.; Deering, C. D.; Bachmann, O.; Huber, C.; Gutiérrez, F. J.

    2014-12-01

    The accumulation of voluminous crystal-poor rhyolites from an upper crustal mush environment inherently necessitates the complementary formation of unerupted silicic cumulates. However, identification of such frozen cumulates remains controversial. This has motivated us to develop of a new geochemical model aimed at better constraining the behavior of trace elements in a magma reservoir concurrently tracking crystallization and imperfect segregation of melt. We use a numerical method to solve our model equations rather than seek analytical solutions, thereby relieving overly simplistic assumptions for the dependencies between partition coefficient or melt segregation rate as functions of crystallinity. Our model allows partition coefficient to vary depending on the crystallinizing mineralogy at any particular stage in magma cooling, as well as the ability to test different rates and efficiencies of crystal-melt segregation. We apply our model first to the Searchlight Pluton as a well-constrained case study, which allows us to quantitatively test existing interpretations of that pluton. Building on this, we broaden our model to better understand the relationship between volcanic and plutonic rocks utilizing the NAVDAT database. Our results produce unambiguous fractionation signatures for segregated melts, while those signatures are muted for their cumulate counterparts. These models suggest that some large granitiods may represent accumulations of crystals, having lost melt in some cases to volcanic eruptions or to higher level evolved plutonic units, although the trace element signature of this process is expected to be subtle.

  13. Final report on the safety assessment of potassium silicate, sodium metasilicate, and sodium silicate.

    PubMed

    Elmore, Amy R

    2005-01-01

    Potassium Silicate, Sodium Metasilicate, and Sodium Silicate combine metal cations with silica to form inorganic salts used as corrosion inhibitors in cosmetics. Sodium Metasilicate also functions as a chelating agent and Sodium Silicate as a buffering and pH adjuster. Sodium Metasilicate is currently used in 168 formulations at concentrations ranging from 13% to 18%. Sodium Silicate is currently used in 24 formulations at concentrations ranging from 0.3% to 55%. Potassium Silicate and Sodium Silicate have been reported as being used in industrial cleaners and detergents. Sodium Metasilicate is a GRAS (generally regarded as safe) food ingredient. Aqueous solutions of Sodium Silicate species are a part of a chemical continuum of silicates based on an equilibrium of alkali, water, and silica. pH determines the solubility of silica and, together with concentration, determines the degree of polymerization. Sodium Silicate administered orally is readily absorbed from the alimentary canal and excreted in the urine. The toxicity of these silicates has been related to the molar ratio of SiO2/Na2O and the concentration being used. The Sodium Metasilicate acute oral LD50 ranged from 847 mg/kg in male rats to 1349.3 mg/kg in female rats and from 770 mg/kg in female mice to 820 mg/kg in male mice. Gross lesions of variable severity were found in the oral cavity, pharynx, esophagus, stomach, larynx, lungs, and kidneys of dogs receiving 0.25 g/kg or more of a commercial detergent containing Sodium Metasilicate; similar lesions were also seen in pigs administered the same detergent and dose. Male rats orally administered 464 mg/kg of a 20% solution containing either 2.0 or 2.4 to 1.0 ratio of sodium oxide showed no signs of toxicity, whereas doses of 1000 and 2150 mg/kg produced gasping, dypsnea, and acute depression. Dogs fed 2.4 g/kg/day of Sodium Silicate for 4 weeks had gross renal lesions but no impairment of renal function. Dermal irritation of Potassium Silicate, Sodium

  14. Ultralow compressibility silicate without highly coordinated silicon.

    PubMed

    Scott, Henry P; Williams, Quentin; Knittle, Elise

    2002-01-07

    The bulk modulus of scheelite-structured ZrSiO(4) is 301.4+/-12.5 GPa, as derived from static compression experiments to 52.5 GPa. It is as stiff as the most incompressible known silicate, SiO(2) stishovite. This high incompressibility indicates that octahedrally coordinated silicon is not required to generate ultrastiff silicates: ZrSiO(4) scheelite is the most incompressible material containing SiO(4) tetrahedra. Its incompressibility is in accord with a semitheoretical relation we derive for the bulk modulus of scheelite-structured materials. Based upon correlations between incompressibility and hardness, scheelite-structured oxides may thus represent a new family of ultrahard materials.

  15. Tailored Nanocomposites of Polypropylene with Layered Silicates

    SciTech Connect

    Xu, L.; Nakajima, H; Manias, E; Krishnamoorti, R

    2009-01-01

    The melt rheological properties of layered silicate nanocomposites with maleic anhydride (MA) functionalized polypropylene are contrasted to those based on ammonium-terminated polypropylene. While the MA functionalized PP based nanocomposites exhibit solid-like linear viscoelastic behavior, consistent with the formation of a long-lived percolated nanoparticle network, the single-end ammonium functionalized PP based nanocomposites demonstrated liquid-like behavior at comparable montmorillonite concentrations. The differences in the linear viscoelasticity are attributed to the presence of bridging interactions in MA functionalized nanocomposites. Further, the transient shear stress of the MA functionalized nanocomposites in start-up of steady shear is a function of the shear strain alone, and the steady shear response is consistent with that of non-Brownian systems. The weak dependence of the steady first normal stress difference on the steady shear stress suggests that the polymer chain mediated silicate network contributes to such unique flow behavior.

  16. Photoemission study of cerium silicate model systems

    NASA Astrophysics Data System (ADS)

    Skála, Tomáš; Matolín, Vladimír

    2013-01-01

    Interaction of silicon with cerium oxide was studied by photoelectron spectroscopy using two model systems CeOx/Si(1 1 1) and Si/CeO2(1 1 1)/Cu(1 1 1) which can be used for fundamental studies in the field of microelectronics and heterogeneous catalysis. The interaction was found to be strong and lead to a formation of cerium silicate films of the proposed stoichiometry Ce4.67Si3O13. Their maximum thickness was limited by diffusion of silicon. Beside silicate other compounds were growing on the surface - SiO2, Si2O, Si, and CeO2. The assignment of the formed species is based on the interpretation of photoemission spectra involving the measurements of various reference O/Si and Sisbnd O/Cu systems.

  17. Topological Control on Silicates' Dissolution Kinetics.

    PubMed

    Pignatelli, Isabella; Kumar, Aditya; Bauchy, Mathieu; Sant, Gaurav

    2016-05-10

    Like many others, silicate solids dissolve when placed in contact with water. In a given aqueous environment, the dissolution rate depends on the composition and the structure of the solid and can span several orders of magnitude. Although the kinetics of dissolution depends on the complexities of both the dissolving solid and the solvent, a clear understanding of which structural descriptors of the solid control its dissolution rate is lacking. By pioneering dissolution experiments and atomistic simulations, we correlate the dissolution rates-ranging over 4 orders of magnitude-of a selection of silicate glasses and crystals to the number of chemical topological constraints acting between the atoms of the dissolving solid. The number of such constraints serves as an indicator of the effective activation energy, which arises from steric effects, and prevents the network from reorganizing locally to accommodate intermediate units forming over the course of the dissolution.

  18. Nature of basalt-deep crust interaction in the petrogenesis of a potassium-rich, silicic-dominated eruptive system, Davis Mountain volcanic field, west Texas

    SciTech Connect

    Ward, R.L.; Walker, J.A. . Dept. of Geology)

    1993-04-01

    The Davis Mountain volcanic field (DMVF) is one of several silicic-dominated eruptive centers that constitute the bulk of the Trans Pecos volcanic province (TPVP). New major-, trace element, and Pb-O isotope data on local granulite-facies xenoliths and the DMVF are used in evaluating the extent of basalt-deep crust interaction to produce voluminous silicic lavas and -ignimbrites. The DMVF (39.3--35.4 Ma) is a high-K, alkali basalt-potassic trachybasalt-shoshonite-latite-trachyte-rhyolite volcanoplutonic series with the evolved members being silica-saturated. DMF silicic rocks are characterized by high concentrations of Rb, Th, U, and K, low-[sup 18]O and have a broad range in Pb isotopes. These characteristics are inconsistent with an origin by partial melting of a Rb-Th-U depleted, unradiogenic Pb granulitic deep crust. However, distinctly different Pb isotope compositions between mafic and silicic rocks preclude an origin by fractional crystallization alone. Multistage-AFC involving a mantle-source, various proportions of OL-CPX-PLAG-KSPAR-MAG-AP-BIO-QTZ-aenigmatite-ZR differentiation, limited (<10%) amounts of deep and upper crustal contamination, and mixing between mafic and silicic magmas can satisfactorily account for the observed chemical and isotopic variation in the DMVF.

  19. Crystallization from a vapor phase in igneous rocks -- A conceptual model

    SciTech Connect

    Kleck, W.D. )

    1993-04-01

    Euhedral, late-stage crystals in pocket pegmatite and in vesicles of volcanic rocks are commonly cited as examples of crystallization from a vapor phase. If, however, crystallization takes place only from the cavity forming vapor, that vapor cannot contain sufficient material for the formation of the observed crystals. The approximate amount of H[sub 2]O vapor and percentage of dissolved silicate matter (1) for shallow pocket pegmatite is 0.5 g/cm[sup 3] and 0.3 percent; (2) for vesicles is 0.002 g/cm[sup 3] and [much lt]1 percent. These values show that the silicate matter dissolved in the vapor is insufficient for the formation of the observed crystals. No (or little) recharge of the vapor is an unstated assumption in most discussions of enclosed cavities. This, however, is not quite correct. For a simplified system, four phases will exist in equilibrium: (1) mineral grains growing from liquid, (2) late-stage, H[sub 2]O-enriched, silicate liquid, (3) vapor, (4) crystals growing from vapor. The total system (for transferal of silicate matter) is given. Little silicate matter is dissolved in the vapor at any one time, but it is replenished as the crystals grow. The vapor becomes a continuously resupplied reservoir of dissolved silicate matter; crystallization from the vapor continues until the silicate liquid is depleted.

  20. Rock-type discrimination from ratioed infrared scanner images of Pisgah Crater, California.

    NASA Technical Reports Server (NTRS)

    Vincent, R. K.; Thomson, F. J.

    1972-01-01

    The radiances in two thermal infrared channels of an airborne scanner system were ratioed to produce images that recorded compositionally diagnostic emittance variations for several silicate rock types near Pisgah Crater, California. The images demonstrate that the ratio method is capable of enhancing emittance variations in the presence of temperature extremes that differ by no more than 25 C, with no temperature corrections.

  1. Highly Shocked Low Density Sedimentary Rocks from the Haughton Impact Structure, Devon Island, Nunavut, Canada

    NASA Technical Reports Server (NTRS)

    Osinski, G. R.; Spray, J. G.

    2001-01-01

    We present the preliminary results of a detailed investigation of the shock effects in highly shocked, low density sedimentary rocks from the Haughton impact structure. We suggest that some textural features can be explained by carbonate-silicate immiscibility. Additional information is contained in the original extended abstract.

  2. Biodegradable Polyester/Layered Silicate Nanocomposites

    DTIC Science & Technology

    2003-01-01

    compatible with the polymer [5-9]. In this paper we report the synthesis and properties of both PLA and PHB nanocomposites with different nanoclays...hydroxy polyester, polylactide (PLA) and fl-hydroxy polyester, polyhydroxybutyrate ( PHB ) with layered silicates have been successfully prepared by melt...extrusion of PLA and PHB with organically modified montmorillonite (MMT) and fluoromica. The mechanical properties of the nanocomposites are improved

  3. Polymorphism in silicate-postperovskite reviewed (Invited)

    NASA Astrophysics Data System (ADS)

    Tschauner, O. D.

    2010-12-01

    Early on in the examination of postperovskite(ppv)-type magnesium metasilicate it had been debated if this potential deep mantle mineral can be subject to further structural transformation as function of composition, pressure, and temperature within the range of conditions in the lower mantle. MgSiO3-perovskite accommodates minor elements through local lattice distortions by tilt of the corner-sharing octahedral framework. The CaIrO3-type ppv structure does not seem to possess a similar mechanism of local relaxation of lattice strain. Instead minor elements may rather be accommodated by periodic kinks in this layered structure (1). This kinking-mechanism allows for generating a plethora of polymorphs similar in structure and free energy (1,2). However, the elastic properties of ppv may be strongly affected by this type of structural modification. While structural analogues of silicate-ppv exhibit this type of polymorphism (3,4) previous attempts to examine polymorphism in silicate-ppv remained suggestive (2,5). This is mostly owed to the severe constraints imposed on powder diffraction studies conducted under the extreme conditions of stability of MgSiO3-ppv. Here I present new results on silicate-ppv based on different experimental strategies which shed more light on this complex yet important issue of structural modifications in minor-element bearing silicate-ppv. (1) Oganov et al. Nature 438, 1142 (2005);(2) Tschauner et al. Am. Min. 93, 533 (2008); (3) Shirako et al. Phys. Chem. Min. 36, 455 (2009); Yakovlev et al. J. Sol. Stat. Chem. 182, 1545 (2009) Work supported through NNSA Cooperative Agreement DOE-FC88-01NV14049

  4. Conductimetric determination of decomposition of silicate melts

    NASA Technical Reports Server (NTRS)

    Kroeger, C.; Lieck, K.

    1986-01-01

    A description of a procedure is given to detect decomposition of silicate systems in the liquid state by conductivity measurements. Onset of decomposition can be determined from the temperature curves of resistances measured on two pairs of electrodes, one above the other. Degree of decomposition can be estimated from temperature and concentration dependency of conductivity of phase boundaries. This procedure was tested with systems PbO-B2O3 and PbO-B2O3-SiO2.

  5. SILICATE EVOLUTION IN BROWN DWARF DISKS

    SciTech Connect

    Riaz, B.

    2009-08-10

    We present a compositional analysis of the 10 {mu}m silicate spectra for brown dwarf disks in the Taurus and Upper Scorpius (UppSco) star-forming regions, using archival Spitzer/Infrared Spectrograph observations. A variety in the silicate features is observed, ranging from a narrow profile with a peak at 9.8 {mu}m, to nearly flat, low-contrast features. For most objects, we find nearly equal fractions for the large-grain and crystalline mass fractions, indicating both processes to be active in these disks. The median crystalline mass fraction for the Taurus brown dwarfs is found to be 20%, a factor of {approx}2 higher than the median reported for the higher mass stars in Taurus. The large-grain mass fractions are found to increase with an increasing strength in the X-ray emission, while the opposite trend is observed for the crystalline mass fractions. A small 5% of the Taurus brown dwarfs are still found to be dominated by pristine interstellar medium-like dust, with an amorphous submicron grain mass fraction of {approx}87%. For 15% of the objects, we find a negligible large-grain mass fraction, but a >60% small amorphous silicate fraction. These may be the cases where substantial grain growth and dust sedimentation have occurred in the disks, resulting in a high fraction of amorphous submicron grains in the disk surface. Among the UppSco brown dwarfs, only usd161939 has a signal-to-noise ratio high enough to properly model its silicate spectrum. We find a 74% small amorphous grain and a {approx}26% crystalline mass fraction for this object.

  6. Neutron Diffraction Study of Silicate Perovskites

    NASA Astrophysics Data System (ADS)

    Mao, H. K.; van Orman, J.; Fei, Y.; Hemley, R. J.; Loveday, J.; Nelmes, R.; Smith, R. I.

    2002-12-01

    The oxygen deficiency and cation-site distribution of silicate perovskite control its physical and chemical properties, including density, bulk modulus, defect mobility, ionic transport, flow behavior, oxidation states, hydration, and minor-element solubility. These properties of perovskite, in turn control the geophysical and geochemical processes of the Earth. The possibility of oxygen deficiency was first recognized in perovskite with minor amounts of Al replacing Mg and Si [1, 2], and its significance is compared to the analogous defect perovskite in ceramics [3]. Basic crystallographic characteristics of the silicate perovskite, including the lattice parameters of the orthorhombic unit cell, the Pbmn space group, and atomic positions, were previously determined by x-ray diffraction [4]. The defect crystallography of silicate perovskite, however, cannot be measured by x-rays because the relevant ions (Mg2+, Al3+, Si4+ and O2-) are isoelectronic. These ions have very different neutron cross-section and can be readily resolved by neutron diffraction. Using multianvil apparatus, we synthesized perovskite samples at 1700°C and 25-28 GPa. We perform multiple runs to accumulate 3 mm3 sample each for the MgSiO3 end member and MgSiO3 plus 5 weight %\\ Al2O3 in perovskite structure. Excellent powder diffraction data were collected at the POLARIS Beamline of ISIS, Rutherford Appleton Lab, and were subjected to Rietveld analysis. Neutron derived information sheds light on the unusual effects found for Al3+ substitution on the compressibility of the silicate perovskite [1]. 1. J. Zhang and D. J. Weidner, Science 284, 782 (1999). 2. J. P. Brodholt, Nature 407, 620 (2000). 3. A. Navrotsky, Science 284, 1788 (1999). 4. N. L. Ross and R. M. Hazen, Phys. Chem. Minerals 17, 228 (1990).

  7. Geotechnical Descriptions of Rock and Rock Masses.

    DTIC Science & Technology

    1985-04-01

    user of the field log can relate to the general class of rock being described. For example, the rock name " syenite " might be qualified by adding "the...FELDSPAR PRE-S---- Coarne Texture Granite Syenite Qts ononite Honzonite Cabbro Peridotite (Platonic or to Qtx Diorite to Diorite Pyroxenite intrusive

  8. Silicic ash beds bracket Emeishan Large Igneous province to < 1 m.y. at ~ 260 Ma

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Cawood, Peter A.; Hou, Ming-Cai; Yang, Jiang-Hai; Ni, Shi-Jun; Du, Yuan-Sheng; Yan, Zhao-Kun; Wang, Jun

    2016-11-01

    Claystone beds directly below and above the Emeishan basalts in SW China formed around the Guadalupian-Lopingian (G - L) boundary. Zircons from both levels give U-Pb ages of 260 Ma, and are identical within-error to ages reported for the Emeishan Large Igneous Province (LIP). The claystones lack Nb - Ta anomalies on primitive mantle normalized elemental diagrams; zircons from these claystones have a geochemical affinity to within-plate-type magmas. These features, combined with the strong negative Eu anomalies in the zircons and high Al2O3/TiO2 ratios, indicate that claystones around the G - L boundary have a silicic volcanic component related to Emeishan LIP. Zircons from the underlying claystone bed have much higher U/Yb and Th/Nb ratios and lower εHf(t) values than those overlying the LIP, suggesting that early-stage silicic volcanic rocks had a higher crustal contamination or assimilation during magmatic processes. In terms of stratigraphic correlation, our data demonstrate that silicic eruptions occurred not only at the end, but also at the beginning of the Emeishan LIP, and the overall duration of the main basaltic phase was short (< 1 m.y).

  9. Structure and properties of ITQ-8: a hydrous layer silicate with microporous silicate layers.

    PubMed

    Marler, Bernd; Müller, Melanie; Gies, Hermann

    2016-06-21

    ITQ-8 is a new hydrous layer silicate (HLS) with a chemical composition of [C4H8(C7H13N)2]8 [Si64O128(OH)16]·48H2O per unit cell. The synthesis of ITQ-8 was first described in 2002 by Díaz-Cabañas et al., the structure of this material, however, remained unsolved at that time. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and FTIR spectroscopy confirmed that ITQ-8 is a layer silicate. The XRD powder pattern was indexed in the monoclinic system with lattice parameters of a0 = 35.5168(5) Å, b0 = 13.3989(2) Å, c0 = 16.0351(2) Å, β = 106.74(2)°. The crystal structure was solved by simulated annealing. Rietveld refinement of the structure in space group C2/c converged to residual values of RBragg = 0.023, RF = 0.022 and chi(2) = 2.3 confirming the structure model. The structure of ITQ-8 contains silicate layers with a topology that resembles a (11-1) section of the framework of zeolite levyne. So far, this layer topology is unique among layer silicates. The layer can be regarded as made up of 4-, 6-, double-six and 8-rings which are interconnected to form cup-like "half-cages". Unlike other HLSs, which possess impermeable silicate layers, ITQ-8 contains 8-rings pores with a free diameter of 3.5 Å × 3.4 Å and can be regarded as a "small-pore layer silicate". In the crystal structure, the organic cations, 1,4-diquiniclidiniumbutane, used as structure directing agents during synthesis are intercalated between the silicate layers. Clusters (bands) of water molecules which are hydrogen bonded to each other and to the terminal Si-OH/Si-O(-) groups are located between the organic cations and interconnect the silicate layers. ITQ-8 is a very interesting material as precursor for the synthesis of microporous framework silicates by topotactic condensation or interlayer expansion reactions leading to 3D micro-pore systems which may be useful in applications as e.g. catalysts, catalyst supports and adsorbents of for separation.

  10. Water and the density of silicate glasses

    NASA Astrophysics Data System (ADS)

    Richet, Pascal; Whittington, Alan; Holtz, François; Behrens, Harald; Ohlhorst, Susanne; Wilke, Max

    A review of published and newly measured densities for 40 hydrous silicate glasses indicates that the room-temperature partial molar volume of water is 12.0+/-0.5cm3/mol. This value holds for simple or mineral compositions as well as for complex natural glasses, from rhyolite to tephrite compositions, prepared up to 10-20kbar pressures and containing up to 7wt% H2O. This volume does not vary either with the molar volume of the water-free silicate phase, with its degree of polymerization or with water speciation. Over a wide range of compositions, this constant value implies that the volume change for the reaction between hydroxyl ions and molecular water is zero and that, at least in glasses, speciation does not depend on pressure. Consistent with data from Ochs and Lange (1997, 1999), systematics in volume expansion for SiO2-M2O systems (M=H, Li, Na, K) suggests that the partial molar thermal expansion coefficient of H2O is about 4× 10-5 K-1 in silicate glasses.

  11. Premixed calcium silicate cement for endodontic applications

    PubMed Central

    Persson, Cecilia; Engqvist, Håkan

    2011-01-01

    Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and amount of calcium sulfate (added to control the setting time) were screened using a statistical model. In the second part of the study, the liquid-to-powder ratio was optimized for cements containing three different amounts of radiopacifier. Finally, the effect of using glycerol rather than water was evaluated in terms of radiopacity. The setting time was found to increase with the amount of radiopacifier when the liquid-to-powder ratio was fixed. This was likely due to the higher density of the radiopacifier in comparison to the calcium silicate, which gave a higher liquid-to-powder ratio in terms of volume. Using glycerol rather than water to mix the cements led to a decrease in radiopacity of the cement. In conclusion, we were able to produce premixed calcium silicate cements with acceptable properties for use in endodontic applications. PMID:23507729

  12. Adsorption of dimeric surfactants in lamellar silicates

    NASA Astrophysics Data System (ADS)

    Balcerzak, Mateusz; Pietralik, Zuzanna; Domka, Ludwik; Skrzypczak, Andrzej; Kozak, Maciej

    2015-12-01

    The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay - hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1‧-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d001) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH2 and CH3 groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  13. Lead-silicate glass optical microbubble resonator

    SciTech Connect

    Wang, Pengfei; Ward, Jonathan; Yang, Yong; Chormaic, Síle Nic; Feng, Xian; Brambilla, Gilberto; Farrell, Gerald

    2015-02-09

    Microbubble whispering gallery resonators have the potential to become key components in a variety of active and passive photonic circuit devices by offering a range of significant functionalities. Here, we report on the fabrication, optical characterization, and theoretical analysis of lead-silicate glass and optical microbubble resonators. Evanescent field coupling to the microbubbles was achieved using a 1 μm diameter, silica microfiber at a wavelength of circa 775 nm. High Q-factor modes were efficiently excited in both single-stem and two-stem, lead-silicate glass, and microbubble resonators, with bubble diameters of 38 μm (single-stem) and 48 μm (two-stem). Whispering gallery mode resonances with Q-factors as high as 2.3 × 10{sup 5} (single-stem) and 7 × 10{sup 6} (two-stem) were observed. By exploiting the high-nonlinearity of the lead-silicate glass, this work will act as a catalyst for studying a range of nonlinear optical effects in microbubbles, such as Raman scattering and four-wave mixing, at low optical powers.

  14. Rock physics of fibrous rocks akin to Roman concrete explains uplifts at Campi Flegrei Caldera

    NASA Astrophysics Data System (ADS)

    Vanorio, Tiziana; Kanitpanyacharoen, Waruntorn

    2015-08-01

    Uplifts in the Campi Flegrei caldera reach values unsurpassed anywhere in the world (~2 meters). Despite the marked deformation, the release of strain appears delayed. The rock physics analysis of well cores highlights the presence of two horizons, above and below the seismogenic area, underlying a coupled process. The basement is a calc-silicate rock housing hydrothermal decarbonation reactions, which provide lime-rich fluids. The caprock above the seismogenic area has a pozzolanic composition and a fibril-rich matrix that results from lime-pozzolanic reactions. These findings provide evidence for a natural process reflecting that characterizing the cementitious pastes in modern and Roman concrete. The formation of fibrous minerals by intertwining filaments confers shear and tensile strength to the caprock, contributing to its ductility and increased resistance to fracture.

  15. Sulfide in the core and the Nd isotopic composition of the silicate Earth

    NASA Astrophysics Data System (ADS)

    McCoy-West, A.; Millet, M. A.; Nowell, G. M.; Wohlers, A.; Wood, B. J.; Burton, K. W.

    2016-12-01

    The chemical composition of the Earth is traditionally explained in terms of evolution from a solar-like composition, similar to that found in primitive chondritic meteorites. It now appears, however, that the silicate Earth is not chondritic, but depleted in incompatible elements and a resovable 20 ppm excess is observed in 142Nd relative to chondirtes [1, 2]. This anomaly requires a process that occurred within 30 Myr of solar system formation and has been variably ascribed to: a complementary enriched reservoir in the deep Earth [1]; loss to space through collisional erosion [3]; or the inhertence of nucleosynthetic anomalies [4]. Sulfide in the core may provide a reservoir capable of balancing the composition of the silicate Earth. Recent experimental work suggests that the core contains a significant proportion of sulfide, added during the final stages of accretion and new data suggests that at high pressures sulfide can incorporate a substantial amount of refractory lithophile and heat-producing elements [5]. The drawback of the short-lived 146Sm-142Nd radiogenic isotope system is that it is not possible to distinguish between fractionations of Sm/Nd that occurs during silicate melting or segregation of a sulfide-melt. Neodymium stable isotopes have the potential to provide just such a tracer of sulfide segregation, because there is a significant contrast in bonding environment between sulfide and silicate, where heavy isotopes should be preferentially incorporated into high force-constant bonds involving REE3+ (i.e. the silicate mantle). Preliminary data indicate that mantle rocks do indeed possess heavier 146Nd/144Nd values than chondritic meteorites by 0.3 ‰, consistent with the removal of light Nd into sulfide in the core, driving the residual mantle to heavier values. Overall, our isotope and elemental data indicate that the rare earths and other incompatible elements are substantially incorporated into sulfide. While Nd stable isotope data for

  16. Zapped, Martian Rock

    NASA Image and Video Library

    2013-02-20

    This image from the Mars Hand Lens Imager MAHLI on NASA Mars rover Curiosity shows details of rock texture and color in an area where the rover Dust Removal Tool DRT brushed away dust that was on the rock.

  17. The Rock Cycle

    ERIC Educational Resources Information Center

    Singh, Raman J.; Bushee, Jonathan

    1977-01-01

    Presents a rock cycle diagram suitable for use at the secondary or introductory college levels which separates rocks formed on and below the surface, includes organic materials, and separates products from processes. (SL)

  18. Theory of wing rock

    NASA Technical Reports Server (NTRS)

    Hsu, C.-H.; Lan, C. E.

    1985-01-01

    Wing rock is one type of lateral-directional instabilities at high angles of attack. To predict wing rock characteristics and to design airplanes to avoid wing rock, parameters affecting wing rock characteristics must be known. A new nonlinear aerodynamic model is developed to investigate the main aerodynamic nonlinearities causing wing rock. In the present theory, the Beecham-Titchener asymptotic method is used to derive expressions for the limit-cycle amplitude and frequency of wing rock from nonlinear flight dynamics equations. The resulting expressions are capable of explaining the existence of wing rock for all types of aircraft. Wing rock is developed by negative or weakly positive roll damping, and sustained by nonlinear aerodynamic roll damping. Good agreement between theoretical and experimental results is obtained.

  19. Rocks in Our Pockets

    ERIC Educational Resources Information Center

    Plummer, Donna; Kuhlman, Wilma

    2005-01-01

    To introduce students to rocks and their characteristics, teacher can begin rock units with the activities described in this article. Students need the ability to make simple observations using their senses and simple tools.

  20. The Rock Cycle

    ERIC Educational Resources Information Center

    Singh, Raman J.; Bushee, Jonathan

    1977-01-01

    Presents a rock cycle diagram suitable for use at the secondary or introductory college levels which separates rocks formed on and below the surface, includes organic materials, and separates products from processes. (SL)

  1. Rocks and Minerals.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Provides background information on rocks and minerals, including the unique characteristics of each. Teaching activities on rock-hunting and identification, mineral configurations, mystery minerals, and growing crystals are provided. Reproducible worksheets are included for two of the activities. (TW)

  2. Rocks and Minerals.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Provides background information on rocks and minerals, including the unique characteristics of each. Teaching activities on rock-hunting and identification, mineral configurations, mystery minerals, and growing crystals are provided. Reproducible worksheets are included for two of the activities. (TW)

  3. Rocks in Our Pockets

    ERIC Educational Resources Information Center

    Plummer, Donna; Kuhlman, Wilma

    2005-01-01

    To introduce students to rocks and their characteristics, teacher can begin rock units with the activities described in this article. Students need the ability to make simple observations using their senses and simple tools.

  4. Silicate release from glass for pharmaceutical preparations.

    PubMed

    Bohrer, Denise; Bortoluzzi, Fabiana; Nascimento, Paulo Cícero; Carvalho, Leandro Machado; Ramirez, Adrian Gustavo

    2008-05-01

    Glass is made of polymeric silica and other minor components, which are necessary for turning the silica into a material more easily moldable and resistant to temperature changes. Glass containers for pharmaceutical usage are classified according to their resistance to a chemical attack, a test carried out in the presence of water and heat. The test is designed to show the released alkalinity, a variable dependent on the amount of sodium oxide, one of the minor components added to the glass mass. In this work, the release of silica from glass by action of constituents from pharmaceutical formulations was investigated. The study included products used in large volumes and usually stored in glass containers. Solutions of amino acids, electrolytes, glucose, oligoelements and others such as heparin and sodium bicarbonate were individually stored in glass containers and heated at 121 degrees C for 30min, as in the water attack test. The test was also carried out only with water, where the pH varied from 2 to 12. The released silicate was measured either by photometry or atomic absorption spectrometry, depending on the nature of the sample. The results showed that silicate is released during the heating cycle even if the contact is with pure water only. The pH exerts a considerable influence on the release, being that the higher the pH, the higher the silica dissolved. An elevated pH, however, is not the only factor responsible for silica dissolution. While in the solutions of NaCl, KCl, Mg Cl2 and ZnSO4 and in most of the amino acids, the concentration of silicate was as high as in pure water (0.1-1.0mg Si/L). In the solutions of sodium acetate, bicarbonate and gluconate, its concentration was much higher, over 30mg Si/L. These results were confirmed by the analysis of commercial products, where in solutions of amino acids the level of silicate ranged from 0.14 to 0.19mg Si/L. On the other hand, calcium gluconate, sodium bicarbonate and potassium phosphate presented

  5. Principles of rock deformation

    SciTech Connect

    Nicolas, A.

    1987-01-01

    This text focuses on the recent achievements in the analysis of rock deformation. It gives an analytical presentation of the essential structures in terms of kinetic and dynamic interpretation. The physical properties underlying the interpretation of rock structures are exposed in simple terms. Emphasized in the book are: the role of fluids in rock fracturing; the kinematic analysis of magnetic flow structures; the application of crystalline plasticity to the kinematic and dynamic analysis of the large deformation imprinted in many metamorphic rocks.

  6. A model for the origin of large silicic magma chambers: precursors of caldera-forming eruptions

    SciTech Connect

    Jellinek, A. Mark; DePaolo, Donald J.

    2002-01-02

    The relatively low rates of magma production in island arcs and continental extensional settings require that the volume of silicic magma involved in large catastrophic caldera-forming (CCF) eruptions must accumulate over periods of 10(5) to 10(6) years. We address the question of why buoyant and otherwise eruptible high silica magma should accumulate for long times in shallow chambers rather than erupt more continuously as magma is supplied from greater depths. Our hypothesis is that the viscoelastic behavior of magma chamber wall rocks may prevent an accumulation of overpressure sufficient to generate rhyolite dikes that can propagate to the surface and cause an eruption. The critical overpressure required for eruption is based on the model of Rubin (1995a). An approximate analytical model is used to evaluate the controls on magma overpressure for a continuously or episodically replenished spherical magma chamber contained in wall rocks with a Maxwell viscoelastic rheology. The governing parameters are the long-term magma supply, the magma chamber volume, and the effective viscosity of the wall rocks. The long-term magma supply, a parameter that is not typically incorporated into dike formation models, can be constrained from observations and melt generation models. For effective wall-rock viscosities in the range 10(18) to 10(20) Pa s(-1), dynamical regimes are identified that lead to the suppression of dikes capable of propagating to the surface. Frequent small eruptions that relieve magma chamber overpressure are favored when the chamber volume is small relative to the magma supply and when the wall rocks are cool. Magma storage, leading to conditions suitable for a CCF eruption, is favored for larger magma chambers (>10(2) km(3)) with warm wall rocks that have a low effective viscosity. Magma storage is further enhanced by regional tectonic extension, high magma crystal contents, and if the effective wall-rock viscosity is lowered by microfracturing, fluid

  7. 68. LITTLE ROCK AND PALMDALE IRRIGATION DISTRICT, LITTLE ROCK DAM: ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    68. LITTLE ROCK AND PALMDALE IRRIGATION DISTRICT, LITTLE ROCK DAM: STRESS SHEET, SHEET 4; MAY, 1918. Littlerock Water District files. - Little Rock Creek Dam, Little Rock Creek, Littlerock, Los Angeles County, CA

  8. Diseases associated with exposure to silica and nonfibrous silicate minerals. Silicosis and Silicate Disease Committee

    SciTech Connect

    Not Available

    1988-07-01

    Silicosis, a disease of historical importance, continues to occur cryptically today. Its pathogenesis is under ongoing study as new concepts of pathobiology evolve. In this article, the gross and microscopic features of the disease in the lungs and the lesions in lymph nodes and other viscera are described. These tissue changes are then discussed in the context of clinical disease and other possible or established complications of silica exposure (ie, scleroderma and rheumatoid arthritis, glomerulonephritis, and bronchogenic carcinoma). Silicates are members of a large family of common minerals, some of which have commercial importance. Silicates are less fibrogenic than silica when inhaled into the lungs, but cause characteristic lesions after heavy prolonged exposure. The features of these disease conditions are described herein. Various aspects of the mineralogy and tissue diagnosis of silicosis and lung disease due to silicates are reviewed. An overview of contemporary regulatory considerations is provided.204 references.

  9. An Evaluation of Ethyl Silicate-Based Grouts for Weathered Silicate Stones

    NASA Astrophysics Data System (ADS)

    Dolph, Brittany Helen

    Culturally significant monuments made of weathered siliceous stone often display sub-surface condition issues such as cracks and voids. These issues require grouts that are ideally compatible with the composition and properties of the substrate. Based on the successful application of ethyl silicates as consolidants in recent literature, this study examines possible formulation pathways for the development of a grout incorporating ethyl silicate. Tetraethylorthosilicate (TEOS), dibutyltin dilaurate (DBTL) as a catalyst, silicone oil (PDMS), various grades of ground quartz, sepiolite, and hollow glass spheres were used in differing concentrations to create samples. These were visually and physically assessed on workability, separation, shrinkage, cracking, strength, and flexibility. Quantitative analysis was performed on selected formulations using UV-Vis-NIR reflectance spectroscopy in coordination with a weight loss experiment to investigate kinetics, dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). Successful formulations tended to include oligomeric TEOS, crushed quartz of mixed grades, sepiolite powder, and PDMS, and show promise for future investigations.

  10. My Pet Rock

    ERIC Educational Resources Information Center

    Lark, Adam; Kramp, Robyne; Nurnberger-Haag, Julie

    2008-01-01

    Many teachers and students have experienced the classic pet rock experiment in conjunction with a geology unit. A teacher has students bring in a "pet" rock found outside of school, and the students run geologic tests on the rock. The tests include determining relative hardness using Mohs scale, checking for magnetization, and assessing luster.…

  11. My Pet Rock

    ERIC Educational Resources Information Center

    Lark, Adam; Kramp, Robyne; Nurnberger-Haag, Julie

    2008-01-01

    Many teachers and students have experienced the classic pet rock experiment in conjunction with a geology unit. A teacher has students bring in a "pet" rock found outside of school, and the students run geologic tests on the rock. The tests include determining relative hardness using Mohs scale, checking for magnetization, and assessing luster.…

  12. Silicate melt inclusions and glasses in lunar soil fragments from the Luna 16 core sample

    USGS Publications Warehouse

    Roedder, E.; Weiblen, P.W.

    1972-01-01

    More than 2000 fragments were studied microscopically, and electron microprobe analyses were made of 39 selected areas, from a few square mm of polished surface, through 75- to 425-??m fragments of lunar soil from two samples of the Luna 16 core. The silicate melt inclusions and glasses differ in important details from those observed earlier in the Apollo samples. Melt inclusions in olivine contain epitaxially oriented daughter crystals, but also show a similar epitaxy around the outside of the crystals not observed in previous lunar samples. Melt inclusions in ilmenite suggest trapping at successive stages in a differentiation sequence. There is abundant evidence for late-stage silicate liquid immiscibility, with melt compositions similar but not identical to those from Apollo 11 and 12. A comparison of the alkali ratio of any given bulk rock analysis with that of its late-stage, high-silica melt shows gross differences for different rocks. This is pertinent to understanding late-stage differentiation processes. Glass fragments and spherules exhibit a wide range of crystallization textures, reflecting their wide range of compositions and cooling histories. No significant differences were found between the two portions of core examined (Zones A and D). ?? 1972.

  13. [Sequential extraction experiments applied to study chemical mobility of fluorine in rocks].

    PubMed

    Xu, Li-Rong; Liang, Han-Dong; Luo, Kun-Li; Feng, Fu-Jian; Tan, Jian-An

    2006-11-01

    Sequential extraction experiments were used to study the chemical mobility of fluorine in rocks. The results show that there are quite big differences in chemical mobility of fluorine in rocks of different types. Fluorine in carbonate rock is very active, in which the proportion of leachable fluorine is generally more than 75%. Fluorine in black rocks of Lower Cambrian is closely related to their different metamorphosed grades, in which fluorine in black carbonaceous slate with higher metamorphosed grade mostly has lower leachability than black shale and black siliceous rock. Generally speaking, the leachable percentage of fluorine is high in phosphorite rocks and low in phyllite. The leachable fluorine in diabase is in direct proportion to its fluorine concentration. There are some differences in chemical mobility of fluorine in stone coal of different ages. Fluorine in stone coal of Silurian has higher leachability than stone coal of Cambrian.

  14. The Sm-Nd systematics of silicate inclusions in iron meteorites: Results from Caddo (IAB)

    NASA Technical Reports Server (NTRS)

    Stewart, Brian W.; Papanastassiou, D. A.; Wasserburg, G. J.

    1993-01-01

    The timing of events leading to the formation of silicate-rich and metal-rich regions in planetesimals remains an important problem in the study of planetary formation and differentiation in the early solar system. The IAB irons are especially important as they are considered to represent a magmatic differentiation series. Iron meteorites present a particular challenge for chronological studies, due to the relative paucity of phases serving as hosts for radioactive parent-daughter nuclides. Recent work using the Re-Os system, following on the pioneering work by Herr et al. and Luck and Allegre, appears promising, but investigators up to now have concentrated on whole rock isochrons. Silicate clasts enclosed within iron meteorites can provide information about the chronology and thermal history of irons. Extensive work on Rb-Sr, K-Ar, and I-Xe has been reported on silicate inclusions in iron meteorites. We report the initial results from our Sm-Nd study of an inclusion with the Caddo IAB iron, the first Sm-Nd isotopic study of a silicate clast embedded within an iron meteorite. Our results include measurements of the standard long-lived Sm-147/Nd-143 (tau = 152 AE) system, as well as the shorter-lived SM-146/Nd-142 (tau = 0.149 AE) system, which has been shown to be very useful in deciphering the history of the early solar system. The Caddo silicate clast was described by Palme et al., who kindly provided us with a major part of the inclusion. The inclusion is coarse-grained consisting predominantly of olivine, clinopyroxene, and plagioclase, with lesser amounts of orthopyroxene, Fe-Ni metal, sulfide, and phosphate. The relatively large grain size (up to 3 mm) and 120 degree grain boundaries suggest extensive metamorphism at high temperatures. Based on study of a thin section, there is evidence for metal invading along grain boundaries in some regions of the inclusion, suggesting that the Fe-Ni metal was molten when the silicate clast was incorporated. Metamorphic

  15. The time scale of the silicate weathering negative feedback on atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Colbourn, G.; Ridgwell, A.; Lenton, T. M.

    2015-05-01

    The ultimate fate of CO2 added to the ocean-atmosphere system is chemical reaction with silicate minerals and burial as marine carbonates. The time scale of this silicate weathering negative feedback on atmospheric pCO2 will determine the duration of perturbations to the carbon cycle, be they geological release events or the current anthropogenic perturbation. However, there has been little previous work on quantifying the time scale of the silicate weathering feedback, with the primary estimate of 300-400 kyr being traceable to an early box model study by Sundquist (1991). Here we employ a representation of terrestrial rock weathering in conjunction with the "GENIE" (Grid ENabled Integrated Earth system) model to elucidate the different time scales of atmospheric CO2 regulation while including the main climate feedbacks on CO2 uptake by the ocean. In this coupled model, the main dependencies of weathering—runoff, temperature, and biological productivity—were driven from an energy-moisture balance atmosphere model and parameterized plant productivity. Long-term projections (1 Myr) were conducted for idealized scenarios of 1000 and 5000 PgC fossil fuel emissions and their sensitivity to different model parameters was tested. By fitting model output to a series of exponentials we determined the e-folding time scale for atmospheric CO2 drawdown by silicate weathering to be ˜240 kyr (range 170-380 kyr), significantly less than existing quantifications. Although the time scales for reequilibration of global surface temperature and surface ocean pH are similar to that for CO2, a much greater proportion of the peak temperature anomaly persists on this longest time scale; ˜21% compared to ˜10% for CO2.

  16. Formation of monazite via prograde metamorphic reactions among common silicates: implications for age determinations

    NASA Astrophysics Data System (ADS)

    Kohn, Matthew J.; Malloy, Margaret A.

    2004-01-01

    Three lines of evidence from schists of the Great Smoky Mountains, NC, indicate that isogradic monazite growth occurred at the staurolite-in isograd at ˜600°C: (1) Monazite is virtually absent below the staurolite-in isograd, but is ubiquitous (several hundred grains per thin section) in staurolite- and kyanite-grade rocks. (2) Many monazite grains are spatially associated with biotite coronas around garnets, formed via the reaction Garnet + Chlorite + Muscovite = Biotite + Plagioclase + Staurolite + H 2O. (3) Garnets contain high-Y annuli that result from prograde dissolution of garnet via the staurolite-in reaction, followed by regrowth, and rare monazite inclusions occur immediately outside the annulus and in the matrix, but not in the garnet core. Larger monazite grains also exhibit quasi-continuous Th zoning with high Th cores and low Th rims, consistent with monazite growth via a single reaction and fractional crystallization during prograde growth. Common silicates may host sufficient P and LREEs that reactions among them can produce observable LREE phosphate. Specifically phosphorus contents of garnet and plagioclase are hundreds of parts per million, and dissolution of garnet and recrystallization of plagioclase could form thousands of phosphate grains several micrometers in diameter per thin section. LREEs may be more limiting, but sheet silicates and plagioclase can contain tens to ˜100 (?) ppm LREE, so recrystallization of these silicates to lower LREE contents could produce hundreds of grains of monazite per thin section. Monazite ages, determined via electron and ion microprobes, are ˜400 Ma, directly linking prograde Barrovian metamorphism of the Western Blue Ridge with the "Acadian" orogeny, in contrast to previous interpretations that metamorphism was "Taconian" (˜450 Ma). Interpretation of ages from metamorphic monazite grains will require prior chemical characterization and identification of relevant monazite-forming reactions, including

  17. Formation and Processing of Amorphous Silicates in Primitive Carbonaceous Chondrites and Cometary Dust

    NASA Technical Reports Server (NTRS)

    Keller, Lindsay P.; Messenger, S.

    2012-01-01

    Chondritic-porous interplanetary dust particles (CP IDPs) exhibit strongly heterogeneous and unequilibrated mineralogy at sub-micron scales, are enriched in carbon, nitrogen and volatile trace elements, and contain abundant presolar materials [1-4]. These observations suggest that CP IDPs have largely escaped the thermal processing and water-rock interactions that have severely modified or destroyed the original mineralogy of primitive meteorites. CP IDPs are believed to represent direct samples of the building blocks of the Solar System - a complex mixture of nebular and presolar materials largely unperturbed by secondary processing. The chemical and isotopic properties of CP IDPs and their atmospheric entry velocities are also consistent with cometary origins. GEMS (glass with embedded metal and sulfides) grains are a major silicate component of CP IDPs. GEMS grains are < 0.5 microns in diameter objects that consist of numerous 10 to 50 nm-sized Fe-Ni metal and Fe-Ni sulfide grains dispersed in a Mg-Si-Al-Fe amorphous silicate matrix [2, 5]. Based on their chemistry and isotopic compositions, most GEMS appear to be non-equilibrium condensates from the early solar nebula [2]. If GEMS grains are a common nebular product, then they should also be abundant in the matrices of the most physically primitive chondritic meteorites. Although amorphous silicates are common in the most primitive meteorites [6-9], their relationship to GEMS grains and the extent to which their compositions and microstructure have been affected by parent body processing (oxidation and aqueous alteration) is poorly constrained. Here we compare and contrast the chemical, microstructural and isotopic properties of amorphous silicates in primitive carbonaceous chondrites to GEMS grains in IDPs.

  18. Assessing in situ crystal-liquid separation in a fossil, large-volume, silicic, magma reservoir

    NASA Astrophysics Data System (ADS)

    Eddy, M. P.

    2016-12-01

    The origin of high-SiO2 rhyolites is controversial. Geochemical gradients in large ignimbrites and regional-scale variations in pluton geochemistry suggest that some of these magmas are generated through differentiation of silicic (>65 wt% SiO2) parent melts in upper crustal magma `mush' zones. This process predicts that large volumes of vertically stratified silicic cumulate should be present within the upper crustal plutonic record. Nevertheless, the number of individual plutons with this type of stratification is limited and geochronologic data has demonstrated that many large, upper crustal plutonic complexes were emplaced at rates too slow (< 0.003 km3/a) and durations too long (>> 1 Ma) to construct a large mush. These observations have led to an alternative hypothesis whereby high-SiO2rhyolites form within the middle or lower crust with little to no differentiation in the upper crust. The Eocene Golden Horn batholith, WA offers a unique opportunity to test the efficiency of crystal-liquid separation. This composite batholith was emplaced at 7-8 km depth and is composed of several distinct magmatic sheets. U-Pb zircon geochronology from the largest sheet, a >424 km3 body of granodiorite and granite with a distinctive rapakivi texture, suggests that it was built at magma emplacement rates compatible with building a large silicic mush. Initial field and geochemical evidence, including lenticular bodies of leucogranite at high elevations and systematic vertical variations in whole rock geochemistry in a short vertical section, suggest that this fossil magma reservoir may have undergone some degree of crystal-liquid separation. I expand on these initial results and present new detailed geologic mapping of textural and compositional variation within a 1 km vertical section coupled with new whole rock geochemical measurements and zircon trace element data to assess the degree to which in situ differentiation may have occurred within this fossil magma reservoir.

  19. Titanite petrochronology of ultrahigh-temperature (UHT) calc-silicates from southern Madagascar: laser-ablation split-stream ICP-MS spot analyses, depth profiles, and quantified trace-element x-ray maps

    NASA Astrophysics Data System (ADS)

    Holder, Robert; Hacker, Bradley

    2017-04-01

    Calc-silicate rocks are often overlooked as sources of pressure-temperature-time data in granulite-UHT metamorphic terranes due to the strong dependence of calc-silicate mineral assemblages on complex fluid compositions, as well as a lack of thermodynamic data on common high-temperature calc-silicate minerals such as scapolite. In the Ediacaran-Cambrian UHT rocks of southern Madagascar, clinopyroxene-scapolite-feldspar-quartz-titanite calc-silicate rocks are wide-spread. U-Pb dates of c. 540-520 Ma from unaltered portions of titanite correspond to cooling of the rocks through upper-amphibolite facies and indicate UHT metamorphism occurred before 540 Ma. Zr concentrations in these domains preserve growth temperatures of 900-950 C, consistent with peak temperatures calculated by pseudosection modeling of nearby pelitic rocks. Younger U-Pb dates (c. 510-490 Ma) correspond to fluid-mediated Pb loss from titanite grains, which occurred below their diffusive Pb-closure temperature, along fractures. The extent of fluid alteration is seen clearly in back-scattered electron images as well as Zr-, Al-, Fe-, Ce-, and Nb-concentration maps. Laser-ablation depth profiling of idioblastic titanite grains shows preserved Pb diffusion profiles at grain rims, but there is no evidence for Zr diffusion, indicating that it was effectively immobile even at UHT.

  20. Silicate-Sulfide-Oxide Phase Equilibria in Subduction Zones

    NASA Astrophysics Data System (ADS)

    Brown, J. L.; Ellis, D. J.; Christy, A. G.; Arculus, R. J.

    2008-12-01

    Classical O2- and S2-dependent equilibria have been extrapolated to high P, showing that fO2 and fS2 in a wide variety of geological environments can be gauged by comparison to fluid buffering reactions. Many of these equilibria involve magnetite, which in intermediate to mafic rock types is eliminated with increasing P during the gabbro to eclogite transition (Green and Ringwood, 1967). It is not generally recognized that traditional buffers, such as QFM (quartz-fayalite-magnetite), are not appropriate for evaluating fluid conditions in subduction zones. This paper will present new fS2 and fO2 equilibria that are consistent with silicate, oxide, and sulfide petrography of the blueschist-eclogite belt in northern New Caledonia (Brown, 2007), and are therefore appropriate for evaluating fluid conditions consistent with subduction zone metamorphism. We evaluate reactions, which are supported by textural evidence in natural specimens, between silicates, oxides, and sulfides (stable at low P) to form garnet (at higher P). Several analogues that eliminate plagioclase +/- magnetite to produce garnet are proposed. A consequence of reacting Fe in sulfide to produce garnet is the concentration of chalcophile elements in the remaining sulfide phase. This is consistent with petrographic observations in the New Caledonian high P belt. Implications of new equilibiria demonstrate that phase relations proposed with garnet cannot be related to classical fS2-fO2 phase diagrams involving QFM. The only reactions involving mineral phases commonly present throughout the range of PT conditions in subducted crust involve ilmenite-rutile-sulfide equilibria. These equilibria can be widely applied to evaluating fluid conditions in the crust and mantle, not just subduction zones. References Brown, J.L. (2007) The Deep Sulfur Cycle: Insights from sulfide metamorphism in blueschist and eclogite, NE New Caledonia. PhD Thesis, The Australian National University. Green, D.H. and Ringwood, A

  1. Spirit Guidepost, 'Plymouth Rock'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    NASA's Mars Exploration Rover Spirit took this panoramic camera image during Spirit's 152nd sol, on June 7, 2004. The rock, informally named 'Plymouth Rock,' is approximately 90 centimeters (35 inches) across and 50 centimeters (20 inches) tall. Spirit did not spend any time studying Plymouth Rock, but rover controllers used it as a guide to maneuver Spirit closer to the 'Columbia Hills.' Like most of the rocks found at the Gusev crater location, Plymouth is most likely a basalt. The tiny vesicles pitting the rock's surface further indicate its volcanic origin.

  2. Rock ramp design guidelines

    USGS Publications Warehouse

    Mooney, David M.; Holmquist-Johnson, Christopher L.; Broderick, Susan

    2007-01-01

    Rock ramps or roughened channels consist of steep reaches stabilized by large immobile material (riprap). Primary objectives for rock ramps include: Create adequate head for diversionMaintain fish passage during low-flow conditionsMaintain hydraulic conveyance during high-flow conditionsSecondary objectives for rock ramp design include:Emulate natural systemsMinimize costsThe rock ramp consists of a low-flow channel designed to maintain biologically adequate depth and velocity conditions during periods of small discharges. The remainder of the ramp is designed to withstand and pass large flows with minimal structural damage. The following chapters outline a process for designing rock ramps.

  3. Charge Generation and Propagation in Igneous Rocks

    NASA Technical Reports Server (NTRS)

    Freund, Friedemann

    2000-01-01

    Resistivity changes, ground potentials, electromagnetic (EM) and luminous signals prior to or during earthquakes have been reported, in addition to ground uplift and tilt, and to changes in the seismic wave propagation parameters. However, no physical model exists that ties these diverse phenomena together. Through time-resolved impacts experiments it has been observed that, when igneous rocks (gabbro, diorite, granite) are impacted at low velocities (approx. 100 m/sec), highly mobile electronic charge carriers are generated, spreading from a small volume near the impact point, causing electric potentials, EM and light emission. The rock becomes momentarily conductive. When impacted at higher velocities (approx. 1.5 km/sec), the propagation of the P and S waves is registered through the transient piezoelectric response of quartz. At the same time, the rock volume is filled with mobile charge carriers, and a positive surface potential is registered. During the next 1-2 msec the surface potential oscillates, due to electron injection from ground. These observations are consistent with positive holes, e.g. defect electrons in the O(2-) sublattice, that can travel via the O 2p-dominated valence band of the silicate minerals at the speed of a phonon-mediated charge transfer. Before activation, the positive hole charge carriers lay dormant in form of positive hole pairs, PHP, electrically inactive, chemically equivalent to peroxy links in the structures of constituent minerals. PHPs are introduced by way of hydroxyl (O3Si-OH) incorporated into nominally anhydrous minerals when they crystallize in water-laden environments. Given that sound waves of even relatively low intensity appear to cause PHPs dissociation, thus generating mobile positive holes, it is proposed that microfracturing during rock deformation cause PHP dissociation. Depending on where and how much the rock volume is stressed, the positive holes are expected to form fluctuating charge clouds in the

  4. Charge Generation and Propagation in Igneous Rocks

    NASA Technical Reports Server (NTRS)

    Freund, Friedemann

    2000-01-01

    Resistivity changes, ground potentials, electromagnetic (EM) and luminous signals prior to or during earthquakes have been reported, in addition to ground uplift and tilt, and to changes in the seismic wave propagation parameters. However, no physical model exists that ties these diverse phenomena together. Through time-resolved impacts experiments it has been observed that, when igneous rocks (gabbro, diorite, granite) are impacted at low velocities (approx. 100 m/sec), highly mobile electronic charge carriers are generated, spreading from a small volume near the impact point, causing electric potentials, EM and light emission. The rock becomes momentarily conductive. When impacted at higher velocities (approx. 1.5 km/sec), the propagation of the P and S waves is registered through the transient piezoelectric response of quartz. At the same time, the rock volume is filled with mobile charge carriers, and a positive surface potential is registered. During the next 1-2 msec the surface potential oscillates, due to electron injection from ground. These observations are consistent with positive holes, e.g. defect electrons in the O(2-) sublattice, that can travel via the O 2p-dominated valence band of the silicate minerals at the speed of a phonon-mediated charge transfer. Before activation, the positive hole charge carriers lay dormant in form of positive hole pairs, PHP, electrically inactive, chemically equivalent to peroxy links in the structures of constituent minerals. PHPs are introduced by way of hydroxyl (O3Si-OH) incorporated into nominally anhydrous minerals when they crystallize in water-laden environments. Given that sound waves of even relatively low intensity appear to cause PHPs dissociation, thus generating mobile positive holes, it is proposed that microfracturing during rock deformation cause PHP dissociation. Depending on where and how much the rock volume is stressed, the positive holes are expected to form fluctuating charge clouds in the

  5. Detection of anorthosite rocks on Mars

    NASA Astrophysics Data System (ADS)

    Carter, J.; Poulet, F.; Flahaut, J.; Ody, A.

    2012-12-01

    highly differentiated, siliceous melt that would form anorthositic rocks requires specific mechanisms such as fractional crystallization, assimilation, or partial melting of an already evolved source incompatible with the ultramafic source composition inferred for Mars [8,9]. The unforeseen detection of anorthositic-rocks therefore places new and strong constraints on the formation and the evolution of the crust and the mantle of Mars. Two possible formation scenarios are discussed, either as a result of the formation of the primordial Martian crust or from later plutonic activity. [1] Christensen et al., Nature (2005). [2] Mustard et al., Science (2005). [3] Malin et al., Science (2000). [4] Murchie et al., JGR (2009). [5] Murchie et al., JGR (2007). [6] Wood et al., Proc. LPSC (1970). [7] Leonard & Tanaka, Geologic Investigations Series I-2694, USGS (2001). [8] Elkins-Tanton et al., JGR (2005). [9] Clarke, Granitoid Rocks, Chapman and Hall (1992).

  6. Adsorption of β-carotene on modified magnesium silicate

    NASA Astrophysics Data System (ADS)

    Sun, Shanshan; Guo, Ning; Fu, Yongfeng

    2016-02-01

    Modified flocculation magnesium silicate is prepared by a hydrothermal process at 120°C for 18 h after adding Al2(SO4)3 into the magnesium silicate gel. Compared with standard magnesium silicate with 328.116 m2 g-1 surface area, this modified magnesium silicate has a bigger BET surface area of 536.803 m2 g-1 and a lower interlayer water content. Modified magnesium silicate exhibits high β-carotene adsorption with a maximum adsorption capacity of 364.96 mg g-1. It is shown that when suspended in organic solvent, this material can be used effectively for carotenoid separation. Furthermore, our results suggest that modified magnesium silicate may be a promising candidate as an absorbent in the decoloring of oil.

  7. The evolution of immiscible silicate and fluoride melts: Implications for REE ore-genesis

    NASA Astrophysics Data System (ADS)

    Vasyukova, O.; Williams-Jones, A. E.

    2016-01-01

    exsolved from the silicate melt and altered the inclusion, replacing fluorbritholite-(Ce) with fluocerite-(Ce) and then bastnäsite-(Ce). This was followed by the formation of a fine-grained intergrowth of bastnäsite-(Ce), gagarinite-(Y) and fluorite at the expense of the earlier bastnäsite-(Ce). Chevkinite-(Ce) was not affected. Zircon, however, was replaced by anhydrous zirconosilicates and, in turn, by hydrous zirconosilicates. The inclusion represents the first macroscopic example of silicate-fluoride immiscibility in nature. We propose that globules of the fluoride melt were initially dispersed within the silicate melt and preserved only rarely in unaltered hypersolvus granite. They accumulated in the residual melt (and therefore in pegmatites) scavenging REE, Ca and F from the silicate melt and, with rare exceptions, were later destroyed by fluids. The latter process contributed significantly to the enrichment of the host rocks in REE, Ca and F.

  8. Geologic map of upper Eocene to Holocene volcanic and related rocks in the Cascade Range, Washington

    USGS Publications Warehouse

    Smith, James G.

    1993-01-01

    For geothermal reasons, the maps emphasize Quaternary volcanic rocks. Large igneous-related geothermal systems that have high temperatures are associated with Quaternary volcanic fields, and geothermal potential declines rapidly as age increases (Smith and Shaw, 1975). Most high-grade recoverable geothermal energy is likely to be associated with silicic volcanism less than 1 Ma. Lower grade (= lower temperature) geothermal resources may be associated with somewhat older rocks; however, volcanic rocks older than about 2 Ma are unlikely geothermal targets (Smith and Shaw, 1975).

  9. Palladium, platinum, and rhodium contents of rocks near the lower margin of the Stillwater complex, Montana.

    USGS Publications Warehouse

    Zientek, M.L.; Foose, M.P.; Leung, Mei

    1986-01-01

    Statistical summaries are reported for Pd, Pt and Rh contents of rocks from the lower part of the Stillwater complex, the underlying contact-metamorphosed sediments, and post-metamorphic dykes and sills wholly within the hornfelses. Variability of the data among the rock types is attributed largely to differences in sulphide content. Non-correlation of sulphur with platinum-group assays of many rock types leads to the suggestion that the immiscible sulphide and silicate liquids did not completely equilibrate with respect to platinum-group elements. -G.J.N.

  10. Modeling Nanomechanical Behavior of Calcium-Silicate-Hydrate

    DTIC Science & Technology

    2012-08-01

    ER D C/ G SL T R -1 2 -3 0 Multiscale Modeling of the Structure of Material Modeling Nanomechanical Behavior of Calcium - Silicate -Hydrate...Nanomechanical Behavior of Calcium - Silicate -Hydrate Mei Qiang Chandler and John F. Peters Geotechnical and Structures Laboratory U.S. Army Engineer...DEM) was used to model the nanomechanical behavior of Calcium - Silicate -Hydrate (C-S-H). The inter- particle forces consist of the traditional friction

  11. Experiments of water formation on warm silicates

    SciTech Connect

    He, Jiao; Vidali, Gianfranco

    2014-06-10

    When dust grains have a higher temperature than they would have in dense clouds, and when H, H{sub 2}, and O{sub 2} have a negligible residence time on grains, the formation of water should still be possible via the hydrogenation of OH and Eley-Rideal-type reactions. We determined that the OH desorption energy from an amorphous silicate surface is at least 143 meV (1656 K). This is 400 K higher than the value previously used in chemical models of the interstellar medium and is possibly as high as 410 meV (4760 K). This extends the temperature range for the efficient formation of water on grains from about 30 K to at least 50 K, and possibly over 100 K. We do not find evidence that water molecules leave the surface upon formation. Instead, through a thermal programmed desorption experiment, we find that water formed on the surface of an amorphous silicate desorbs at around 160 K. We also measured the cross-sections for the reaction of H and D with an O{sub 3} layer on an amorphous silicate surface at 50 K. The values of the cross-sections, σ{sub H} = 1.6 ± 0.27 Å{sup 2} and σ{sub D} = 0.94 ± 0.09 Å{sup 2}, respectively, are smaller than the size of an O{sub 3} molecule, suggesting the reaction mechanism is more likely Eley-Rideal than hot-atom. Information obtained through these experiments should help theorists evaluate the relative contribution of water formation on warm grains versus in the gas phase.

  12. Dentinal Tubule Penetration of Tricalcium Silicate Sealers.

    PubMed

    McMichael, Greer E; Primus, Carolyn M; Opperman, Lynne A

    2016-04-01

    The treatments for which mineral trioxide aggregate (MTA)-based materials can be used in dentistry are expanding. Smaller particle size and easier handling properties have allowed the advent of tricalcium silicate sealers including EndoSequence BC Sealer (Brasseler USA, Savannah, GA), QuickSet2 (Avalon Biomed, Bradenton, FL), NeoMTA Plus (Avalon Biomed), and MTA Fillapex (Angelus, Londrina, Brazil). The objective of this study was to measure the tubule penetration with these sealers using continuous wave (CW) and single-cone (SC) obturation techniques. Eighty single-rooted teeth were randomly divided into 8 groups of 10 and obturated with 1 of the previously mentioned sealers mixed with trace amounts of rhodamine using either the CW or SC technique. Teeth were sectioned at 1 mm and 5 mm from the apex and examined under a confocal laser microscope. The percentage of sealer penetration and the maximum sealer penetration were measured. The tricalcium silicate sealers penetrated tubules as deep as 2000 μm (2 mm). The percentage of sealer penetration was much higher 5 mm from the apex, with many specimens having 100% penetration for both SC and warm vertical techniques. MTA Fillapex, a resin-based sealer with less than 20% MTA particles, had significantly greater tubule penetration with a warm vertical technique versus the SC technique at the 1-mm level. Within the limitations of this study, the CW and SC techniques produced similar tubule penetration at both the 1-mm and the 5-mm level with the tricalcium silicate sealers BC Sealer, QuickSet2, and NeoMTA Plus. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  13. Preparation of reactive beta-dicalcium silicate

    DOEpatents

    Shen, M.S.; Chen, J.M.; Yang, R.T.

    1980-02-28

    This invention relates to the preparation of fine particles of reactive beta-dicalcium silicate by means of a solid state process which comprises firing a mixture of calcium sulfate, silica, and a reducing additive selected from the group consisting of calcium sulfide, carbon, carbon monoxide, methane, and hydrogen, at a temperature of about 850 to 1000/sup 0/C. A carrier gas such as nitrogen or carbon dioxide may also be added, if desired. A high concentration of sulfur dioxide is a by-product of this process.

  14. Activity composition relationships in silicate melts

    SciTech Connect

    Glazner, A.F.

    1990-01-01

    Equipment progress include furnace construction and electron microprobe installation. The following studies are underway: phase equilibria along basalt-rhyolite mixing line (olivine crystallization from natural silicic andensites, distribution of Fe and Mg between olivine and liquid, dist. of Ca and Na between plagioclase and liquid), enthalpy-composition relations in magmas (bulk heat capacity of alkali basalt), density model for magma ascent and contamination, thermobarometry in igneous systems (olivine/plagioclase phenocryst growth in Quat. basalt), high-pressure phase equilibria of alkali basalt, basalt-quartz mixing experiments, phase equilibria of East African basalts, and granitic minerals in mafic magma. (DLC)

  15. Preparation of reactive beta-dicalcium silicate

    DOEpatents

    Shen, Ming-Shing; Chen, James M.; Yang, Ralph T.

    1982-01-01

    This invention relates to the preparation of fine particles of reactive beta-dicalcium silicate by means of a solid state process which comprises firing a mixture of calcium sulfate, silica and a reducing additive selected from the group consisting of calcium sulfide, carbon, carbon monoxide, methane and hydrogen, at a temperature of about 850.degree.-1000.degree. C. A carrier gas such as nitrogen or carbon dioxide may also be added, if desired. A high concentration of sulfur dioxide is a by-product of this process.

  16. Microbial dissolution of silicate materials. Final report

    SciTech Connect

    Schwartzman, D.

    1996-03-26

    The objective of this research was to better understand the role of selected thermophilic bacteria in the colonization and dissolution of silicate minerals, with potential applications to the HDR Project. The demonstration of enhanced dissolution from microbial effects is critically dependent on providing a mineral bait within a media deficient in the critical nutrient found in the mineral (e.g., Fe). Reproducible experimental conditions in batch experiments require agitation to expose mineral powders, as well as nearly similar initial conditions for both inoculated cultures and controls. It is difficult, but not impossible to ensure reproducible conditions with microbes favoring filamentous growth habits.

  17. Group II tris(glycolato)silicates as precursors to silicate glasses and ceramics

    SciTech Connect

    Kansal, P.; Laine, R.M.

    1995-03-01

    Group II tris(glycolato)silicates, MSi(OCH{sub 2}CH{sub 2}O){sub 3} (where M = Ba, Ca, Mg), can be synthesized directly by reaction of silica with ethylene glycol and alkaline-earth (group II) oxides at 200 C. These hexa-alkoxy silicates serve as precursors to silicate glass and ceramic powders. They are readily modified by exchange with longer-chain diols into proper precursors. These rheologically useful precursors may provide access to silicate or aluminosilicate powders, thin films, fibers, and coatings. Thus, the authors have examined the utility of hexacoordinate glycolatosilicates as model precursors. Pyrolysis of the compounds, MSi(OCH{sub 2}CH{sub 2})O{sub 3}, in air transforms them to their anticipated ceramic products, MO{center_dot}SiO{sub 2}. The phase transformation and chemical changes that occur during pyrolysis were characterized using X-ray powder diffractometry (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), and scanning electron microscopy (SEM). The hexacoordinate glycolatosilicates oxidatively decompose at {approx}300 C to form amorphous materials. Moderate to significant quantities of the group II carbonates, MCO{sub 3} (15--50 wt%), form coincidentally as the amorphous intermediates trap CO{sub 2} generated by ligand oxidation. At {approx}900 C, the amorphous materials crystallize into the expected, phase-pure, MO{center_dot}SiO{sub 2}.

  18. Sr-Nd-Hf-Pb isotopic constraints on the origin of silicic lavas in the northern Cascade Arc

    NASA Astrophysics Data System (ADS)

    Martindale, M.; Mullen, E.; Weis, D.

    2015-12-01

    The Cascade Arc is the type-locality for a 'hot' subduction zone, where the downgoing slab is young and subduction is relatively slow; a unique setting for studying the controls on silicic (>56 wt% SiO2) magma genesis [1,2]. We present high precision Sr-Nd-Hf-Pb isotopic and trace element data for silicic lavas and country rocks from the major centres of the Garibaldi Volcanic Belt (GVB) in British Columbia, which are hosted by the Mesozoic Coast Plutonic Complex and accreted Coast Belt terranes. In isotopic plots, the silicic GVB lavas define mixing curves between northern Cascadia Basin sediment [3] and Juan de Fuca MORB. The silicic GVB lavas have lower ɛNd, and higher ɛHf, 87Sr/86Sr, 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb than co-existing alkalic mafic lavas [2,4] which define a separate isotopic cluster. The alkalic mafic lavas have OIB-like trace element compositions [2,4], but the silicic lavas are calc-alkaline with a typical 'arc' trace element signature. Geochemical systematics suggest that a mafic, isotopically 'depleted' contaminant may be affecting the composition of GVB silicic lavas. However, modelling indicates that slab melts do not constitute a major component of the lavas despite high slab temperatures. Geochemical models also rule out the accreted Coast Belt terranes as an assimilant. However, AFC modelling using 147 Ma Cloudburst quartz diorite [5] as the assimilant can explain both the trace element and isotopic compositional range displayed by GVB silicic magmas, consistent with the Coast Plutonic Complex as a major component of the deep crust in this region. Crustal assimilation would have partially overprinted any alkalic mantle-derived signature of parental magmas, while imparting a calc-alkaline arc signature to resulting silicic magmas. [1] Green & Harry (1999) EPSL, 171; [2] Mullen & Weis (2013) G3, 14; [3] Carpentier et al. (2014) Chem Geol, 382; [4] Mullen & Weis (2015) EPSL, 414; [5] Friedman & Armstrong (1995) GSA

  19. The determination of the acoustic parameters of volcanic rocks from compressional velocity measurements

    USGS Publications Warehouse

    Carroll, R.D.

    1969-01-01

    A statistical analysis was made of the relationship of various acoustic parameters of volcanic rocks to compressional wave velocities for data obtained in a volcanic region in Nevada. Some additional samples, chiefly granitic rocks, were also included in the study to extend the range of parameters and the variety of siliceous rock types sampled. Laboratory acoustic measurements obtained on 62 dry core samples were grouped with similar measurements obtained from geophysical logging devices at several depth intervals in a hole from which 15 of the core samples had been obtained. The effects of lithostatic and hydrostatic load on changing the rock acoustic parameters measured in the hole were noticeable when compared with the laboratory measurements on the same core. The results of the analyses determined by grouping all of the data, however, indicate that dynamic Young's, shear and bulk modulus, shear velocity, shear and compressional characteristic impedance, as well as amplitude and energy reflection coefficients may be reliably estimated on the basis of the compressional wave velocities of the rocks investigated. Less precise estimates can be made of density based on the rock compressional velocity. The possible extension of these relationships to include many siliceous rocks is suggested. ?? 1969.

  20. Research drilling in young silicic volcanoes

    SciTech Connect

    Eichelberger, J.C.

    1989-06-30

    Magmatic activity, and particularly silicic magmatic activity, is the fundamental process by which continental crust forms and evolves. The transport of magma from deep crustal reservoirs to the surface is a neglected but important aspect of magmatic phenomena. It encompasses problems of eruptive behavior, hydrothermal circulation, and ore deposition, and must be understood in order to properly interpret deeper processes. Drilling provides a means for determining the relationship of shallow intrusive processes to eruption processes at young volcanoes where eruptions are best understood. Drilling also provides a means for directly observing the processes of heat and mass transfer by which recently emplaced intrusions approach equilibrium with their new environment. Drilling in the Inyo Chain, a 600-year-old chain of volcanic vents in California, has shown the close relationship of silicic eruption to shallow dike emplacement, the control of eruptive style by shallow porous-flow degassing, the origin of obsidian by welding, the development of igneous zonation by viscosity segregation, and the character and size of conduits in relation to well-understood magmatic and phreatic eruptions. 36 refs., 9 figs.

  1. Thermochemistry of dense hydrous magnesium silicates

    NASA Technical Reports Server (NTRS)

    Bose, Kunal; Burnley, Pamela; Navrotsky, Alexandra

    1994-01-01

    Recent experimental investigations under mantle conditions have identified a suite of dense hydrous magnesium silicate (DHMS) phases that could be conduits to transport water to at least the 660 km discontinuity via mature, relatively cold, subducting slabs. Water released from successive dehydration of these phases during subduction could be responsible for deep focus earthquakes, mantle metasomatism and a host of other physico-chemical processes central to our understanding of the earth's deep interior. In order to construct a thermodynamic data base that can delineate and predict the stability ranges for DHMS phases, reliable thermochemical and thermophysical data are required. One of the major obstacles in calorimetric studies of phases synthesized under high pressure conditions has been limitation due to the small (less than 5 mg) sample mass. Our refinement of calorimeter techniques now allow precise determination of enthalpies of solution of less than 5 mg samples of hydrous magnesium silicates. For example, high temperature solution calorimetry of natural talc (Mg(0.99) Fe(0.01)Si4O10(OH)2), periclase (MgO) and quartz (SiO2) yield enthalpies of drop solution at 1044 K to be 592.2 (2.2), 52.01 (0.12) and 45.76 (0.4) kJ/mol respectively. The corresponding enthalpy of formation from oxides at 298 K for talc is minus 5908.2 kJ/mol agreeing within 0.1 percent to literature values.

  2. Tip-induced nanoreactor for silicate

    PubMed Central

    Gao, Ming; Ma, Liran; Liang, Yong; Gao, Yuan; Luo, Jianbin

    2015-01-01

    Nanoscale scientific issues have attracted an increasing amount of research interest due to their specific size-effect and novel structure-property. From macro to nano, materials present some unique chemical reactivity that bulk materials do not own. Here we introduce a facile method to generate silicate with nanoscale control based on the establishment of a confined space between a meso/nanoscale tungsten tip and a smooth silica/silicon substrate. During the process, local water-like droplets deposition can be obviously observed in the confinement between the Si/SiO2 surfaces and the KOH-modified tungsten tip. By the combination of in-situ optical microscopy and Raman spectroscopy, we were able to take a deep insight of both the product composition and the underlying mechanism of such phenomena. It was indicated that such nanoreactor for silicate could be quite efficient as a result of the local capillarity and electric field effect, with implications at both nano and meso scales. PMID:26364882

  3. Thermochemistry of dense hydrous magnesium silicates

    NASA Technical Reports Server (NTRS)

    Bose, Kunal; Burnley, Pamela; Navrotsky, Alexandra

    1994-01-01

    Recent experimental investigations under mantle conditions have identified a suite of dense hydrous magnesium silicate (DHMS) phases that could be conduits to transport water to at least the 660 km discontinuity via mature, relatively cold, subducting slabs. Water released from successive dehydration of these phases during subduction could be responsible for deep focus earthquakes, mantle metasomatism and a host of other physico-chemical processes central to our understanding of the earth's deep interior. In order to construct a thermodynamic data base that can delineate and predict the stability ranges for DHMS phases, reliable thermochemical and thermophysical data are required. One of the major obstacles in calorimetric studies of phases synthesized under high pressure conditions has been limitation due to the small (less than 5 mg) sample mass. Our refinement of calorimeter techniques now allow precise determination of enthalpies of solution of less than 5 mg samples of hydrous magnesium silicates. For example, high temperature solution calorimetry of natural talc (Mg(0.99) Fe(0.01)Si4O10(OH)2), periclase (MgO) and quartz (SiO2) yield enthalpies of drop solution at 1044 K to be 592.2 (2.2), 52.01 (0.12) and 45.76 (0.4) kJ/mol respectively. The corresponding enthalpy of formation from oxides at 298 K for talc is minus 5908.2 kJ/mol agreeing within 0.1 percent to literature values.

  4. Silicate mineralogy at the surface of Mercury

    NASA Astrophysics Data System (ADS)

    Namur, Olivier; Charlier, Bernard

    2017-01-01

    NASA's MESSENGER spacecraft has revealed geochemical diversity across Mercury's volcanic crust. Near-infrared to ultraviolet spectra and images have provided evidence for the Fe2+-poor nature of silicate minerals, magnesium sulfide minerals in hollows and a darkening component attributed to graphite, but existing spectral data is insufficient to build a mineralogical map for the planet. Here we investigate the mineralogical variability of silicates in Mercury's crust using crystallization experiments on magmas with compositions and under reducing conditions expected for Mercury. We find a common crystallization sequence consisting of olivine, plagioclase, pyroxenes and tridymite for all magmas tested. Depending on the cooling rate, we suggest that lavas on Mercury are either fully crystallized or made of a glassy matrix with phenocrysts. Combining the experimental results with geochemical mapping, we can identify several mineralogical provinces: the Northern Volcanic Plains and Smooth Plains, dominated by plagioclase, the High-Mg province, strongly dominated by forsterite, and the Intermediate Plains, comprised of forsterite, plagioclase and enstatite. This implies a temporal evolution of the mineralogy from the oldest lavas, dominated by mafic minerals, to the youngest lavas, dominated by plagioclase, consistent with progressive shallowing and decreasing degree of mantle melting over time.

  5. Crystalline-amorphous transition in silicate perovskites

    SciTech Connect

    Hemmati, M.; Chizmeshya, A. |; Wolf, G.H.; Poole, P.H.; Shao, J.; Angell, C.A.

    1995-06-01

    CaSiO{sub 3} and MgSiO{sub 3} perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model perovskite systems transform under tension to a low-density glass composed of corner shared chains of tetrahedral silicon. The amorphization is initiated by a thermally activated step involving a soft polar optic mode in the perovskite phase at the Brillouin zone center. Progression of the system along this reaction coordinate triggers, in succession, multiple barrierless modes of instability ultimately producing a catastrophic decohesion of the lattice. An important intermediary along the reaction path is a crystalline phase where silicon is in a five-coordinate site and the alkaline-earth metal atom is in eightfold coordination. At the onset pressure, this transitory phase is itself dynamically unstable to a number of additional vibrational modes, the most relevant being those which result in transformation to a variety of tetrahedral chain silicate motifs. These results support the conjecture that stress-induced amorphization arises from the near simultaneous accessibility of multiple modes of instability in the highly metastable parent crystalline phase.

  6. Pristine moon rocks - Apollo 17 anorthosites

    NASA Technical Reports Server (NTRS)

    Warren, P. H.; Jerde, E. A.; Kallemeyn, G. W.

    1991-01-01

    New chemical analyses and petrographic descriptions for 10 previously unanalyzed Apollo 17 rock samples are provided. Attention is focused on several that appear to be pristine. All samples were analyzed in INAA using a procedure based on that of Kallemeyn et al. (1989). One sample was found to be unambiguously pristine, and is the first pristine ferroan-anorthositic suite (FAS) sample from Apollo 17. It exhibits extremely low-mg(asterisk) mafic silicates, coupled with relatively sodic plagioclase. It has an unusually high augite/low-Ca pyroxene ratio and contains incompatible trace elements at levels unprecedentedly high compared to FAS anorthosites from the Apollo 14, 15, 16 sites. It is inferred that 74114.5, and Apollo 17 anorthosites in general, formed at a relatively late stage in the evolution of the primordial magmasphere.

  7. Carbon Mineralization Using Phosphate and Silicate Ions

    NASA Astrophysics Data System (ADS)

    Gokturk, H.

    2013-12-01

    Carbon dioxide (CO2) reduction from combustion of fossil fuels has become an urgent concern for the society due to marked increase in weather related natural disasters and other negative consequences of global warming. CO2 is a highly stable molecule which does not readily interact with other neutral molecules. However it is more responsive to ions due to charge versus quadrupole interaction [1-2]. Ions can be created by dissolving a salt in water and then aerosolizing the solution. This approach gives CO2 molecules a chance to interact with the hydrated salt ions over the large surface area of the aerosol. Ion containing aerosols exist in nature, an example being sea spray particles generated by breaking waves. Such particles contain singly and doubly charged salt ions including Na+, Cl-, Mg++ and SO4--. Depending on the proximity of CO2 to the ion, interaction energy can be significantly higher than the thermal energy of the aerosol. For example, an interaction energy of 0.6 eV is obtained with the sulfate (SO4--) ion when CO2 is the nearest neighbor [2]. In this research interaction between CO2 and ions which carry higher charges are investigated. The molecules selected for the study are triply charged phosphate (PO4---) ions and quadruply charged silicate (SiO4----) ions. Examples of salts which contain such molecules are potassium phosphate (K3PO4) and sodium orthosilicate (Na4SiO4). The research has been carried out with first principle quantum mechanical calculations using the Density Functional Theory method with B3LYP functional and Pople type basis sets augmented with polarization and diffuse functions. Atomic models consist of the selected ions surrounded by water and CO2 molecules. Similar to the results obtained with singly and doubly charged ions [1-2], phosphate and silicate ions attract CO2 molecules. Energy of interaction between the ion and CO2 is 1.6 eV for the phosphate ion and 3.3 eV for the silicate ion. Hence one can expect that the selected

  8. Jurassic silicic volcanism in the Transantarctic Mountains: Was it related to plate margin processes or to Ferrar magmatism?

    USGS Publications Warehouse

    Elliot, D.H.; Fleming, T.H.; Foland, K.A.; Fanning, C.M.

    2007-01-01

    Silicic volcanism in the Transantarctic Mountains, represented by rhyolitic tuff that mainly precedes emplacement of the Ferrar Large Igneous Province, is important in interpretation of the tectonic evolution of the Antarctic sector of Gondwana. Sr and Nd isotope data indicate that the tuffs are not directly related to Ferrar magmatism nor to melting of the underlying Ross orogen crust yet zircon gives a U-Pb age of 182.7±1.8 Ma, similar to the U/Pb age for the Ferrar. Distribution of the silicic tuffs along 1400 km of the Transantarctic Mountains suggests, alternatively, a relationship to the Gondwana plate margin. Although West Antarctica comprises Mesoproterozoic crustal terrains, few analyzed rocks are compatible isotopically with the Lower Jurassic tuffs. The source of the tuffs must lie in unexposed Early Jurassic magmatic centers in West Antarctica or an unexposed crustal terrain beneath the Transantarctic Mountains.

  9. Mechanism of the water and carbon dioxide solubility in oxides and silicates and the role of O-

    NASA Astrophysics Data System (ADS)

    Freund, Friedemann

    1981-07-01

    The dissolution of water does not stop at the OH- stage but may proceed further towards H2 plus O- formation. The discovery of atomic carbon dissolved in minerals suggests that, if CO2 enters oxides and silicates at high pressures and temperatures, not only [CO3]2- ions but also [CO{4/.}]4- complexes are formed via a charge transfer which produces O- and essentially zero-valent, atomic carbon. Under P —T-conditions of the mantle, where the solubility for water and CO2 is high, the silicate phases formed may therefore consist to a large volume fraction of O- ions which are much smaller than O2-ions and strongly cova-lently bonding. The implications for the crystal chemistry of high pressure phases, for the petrology of mantle rocks are outlined.

  10. Infrasound from Rock Fall at Santiaguito Volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Ronan, T.; Terbush, B.; Miller, A. J. C.; Anderson, J.; Johnson, J. B.

    2014-12-01

    Volcanoes generate infrasound from incidental rock fall and from rock fall directly associated with eruptions. This study demonstrates that arrays of infrasound microphones are capable of surveillance and quantification of rock fall events, including their size, location, velocity and frequency of occurrence. The study performed at Volcan Santiaguito (Guatemala) in January 2014 made use of a three element infrasound array with 30 m aperture deployed ~500 m from the active vent and ~300 m from the slide path where numerous rock falls descend. Rock fall events were detected on average 5 to 10 times per hour and were easily distinguishable from vent activity (e.g., explosions) by their dynamic back azimuth projection. As blocks tumbled down the southwest flanks of Santiaguito, sources were tracked across an azimuthal range of nearly 30 degrees, consistent with the dome's slope. Back azimuths, determined with a [progressive] multichannel cross correlation technique, are projected to the volcano's steep flanks and are used to precisely locate the source of infrasound (i.e., rocks impacting on the volcano slopes) and their velocity (10-30 m/s). Typical signals last about one minute and are characterized by cigar-shaped tremor envelopes with a predominance of energy above ~5 Hz this spectral content contrasts with Santiaguito eruption infrasound, which is peaked at ~1 Hz. Synchronous video records of the responsible rock fall confirm position and velocity and illustrate that even the smallest rock falls (estimated block size of ~1 m) are capable of producing a traceable signal. This study is a testament to the capabilities of infrasound array remote sensing for detecting volcanic unrest in the form of rock fall, which is common at most active silicic domes.

  11. Isotopic composition of uranium and thorium in crystalline rocks

    NASA Astrophysics Data System (ADS)

    Rosholt, John N.

    1983-09-01

    The 238U-234U-230Th-232Th system has been investigated in 84 silicic crystalline rocks obtained from drill cores, surface, and near-surface samples in California, Wyoming, Colorado, and Illinois. Results of these analyses displayed on ternary diagrams with apexes for 238U, 234U, and 230Th indicate five predominant geochemical processes that affected uranium in the rock: (1) bulk uranium leaching where 238U and 234U were removed with little or no fractionation; (2) preferential 234U leaching by alpha recoil displacement (234U recoil loss) with lesser 238U loss; (3) 234U recoil loss with little or no 238U loss; (4) uranium assimilation where both 238U and 234U were added with present-day 234U/238U activity ratios varying from 0.8 to 1.2; and (5) addition of 234U and 230Th by daughter emplacement processes (234U + 230Th recoil gain). Evidence for the existence of 234U and 230Th recoil gain in rocks is the most important finding of this investigation. Radioactive disequilibrium occurs in the majority of rocks analyzed where 234U recoil loss is the predominant process associated with incipient weathering; U assimilation and 234U+230Th recoil gain occur under conditions of substantial water penetration along fractures and into weathered zones in the rocks. Relatively unfractured and petrographically fresh rocks from the UPH-3 drill hole in northern Illinois are closest to being in radioactive equilibrium for any suite of rocks included in this study, and they demonstrate that equilibrium during the last 0.5 m.y. can be maintained over a substantial vertical distance where there has been little or no movement of water in the basement rock. The 238U-234U-230Th system can be a sensitive indicator of geologically recent U mobility and rock/water interaction both in petrographically fresh core samples and in `sealed' fracture zones.

  12. Friction of rocks

    USGS Publications Warehouse

    Byerlee, J.

    1978-01-01

    Experimental results in the published literature show that at low normal stress the shear stress required to slide one rock over another varies widely between experiments. This is because at low stress rock friction is strongly dependent on surface roughness. At high normal stress that effect is diminished and the friction is nearly independent of rock type. If the sliding surfaces are separated by gouge composed of Montmorillonite or vermiculite the friction can be very low. ?? 1978 Birkha??user Verlag.

  13. Paleomagnetism and Mineralogy of Unusual Silicate Glasses and Baked Soils on the Surface of the Atacama Desert of Northern Chile: A Major Airburst Impact ~12ka ago?.

    NASA Astrophysics Data System (ADS)

    Roperch, P. J.; Blanco, N.; Valenzuela, M.; Gattacceca, J.; Devouard, B.; Lorand, J. P.; Tomlinson, A. J.; Arriagada, C.; Rochette, P.

    2015-12-01

    Unusual silicate glasses were found in northern Chile in one of the driest place on earth, the Atacama Desert. The scoria-type melted rocks are littered on the ground at several localities distributed along a longitudinal band of about 50km. The silicate glasses have a stable natural remanent magnetization carried by fine-grained magnetite and acquired during cooling. At one locality, fine-grained overbank sediments were heated to form a 10 to 20 cm-thick layer of brick-type samples. Magnetic experiments on oriented samples demonstrate that the baked clays record a thermoremanent magnetization acquired in situ above 600°C down to more than 10cm depth and cooled under a normal polarity geomagnetic field with a paleointensity of 40μT. In some samples of the silicate glass, large grains of iron sulphides (troilite) are found in the glass matrix with numerous droplets of native iron, iron sulphides and iron phosphides indicating high temperature and strong redox conditions during melting. The paleomagnetic record of the baked clays and the unusual mineralogy of the silicate glasses indicate a formation mainly by in situ high temperature radiation. Paleomagnetic experiments and chemical analyses indicate that the silicate glasses are not fulgurite type rocks due to lightning events, nor volcanic glasses or even metallurgical slags related to mining activity. The existence of a well-developped baked clay layer indicates that the silicate glasses are not impact-related ejectas. The field, paleomagnetic and mineralogical observations support evidence for a thermal event likely related to a major airburst. The youngest calibrated 14C age on a charcoal sample closely associated with the glass indicates that the thermal event occurred around 12 to 13 ka BP. The good conservation of the surface effects of this thermal event in the Atacama Desert could provide a good opportunity to further estimate the threats posed by large asteroid airbursts.

  14. Bounce Rock Dimple

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This panoramic camera image shows the hole drilled by the Mars Exploration Rover Opportunity's rock abrasion tool into the rock dubbed 'Bounce' on Sol 65 of the rover's journey. The tool drilled about 7 millimeters (0.3 inches) into the rock and generated small piles of 'tailings' or rock dust around the central hole, which is about 4.5 centimeters (1.7 inches) across. The image from sol 66 of the mission was acquired using the panoramic camera's 430 nanometer filter.

  15. Opaque rock fragments

    SciTech Connect

    Abhijit, B.; Molinaroli, E.; Olsen, J.

    1987-05-01

    The authors describe a new, rare, but petrogenetically significant variety of rock fragments from Holocene detrital sediments. Approximately 50% of the opaque heavy mineral concentrates from Holocene siliciclastic sands are polymineralic-Fe-Ti oxide particles, i.e., they are opaque rock fragments. About 40% to 70% of these rock fragments show intergrowth of hm + il, mt + il, and mt + hm +/- il. Modal analysis of 23,282 opaque particles in 117 polished thin sections of granitic and metamorphic parent rocks and their daughter sands from semi-arid and humid climates show the following relative abundances. The data show that opaque rock fragments are more common in sands from igneous source rocks and that hm + il fragments are more durable. They assume that equilibrium conditions existed in parent rocks during the growth of these paired minerals, and that the Ti/Fe ratio did not change during oxidation of mt to hm. Geothermometric determinations using electron probe microanalysis of opaque rock fragments in sand samples from Lake Erie and the Adriatic Sea suggest that these rock fragments may have equilibrated at approximately 900/sup 0/ and 525/sup 0/C, respectively.

  16. Bounce Rock Dimple

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This panoramic camera image shows the hole drilled by the Mars Exploration Rover Opportunity's rock abrasion tool into the rock dubbed 'Bounce' on Sol 65 of the rover's journey. The tool drilled about 7 millimeters (0.3 inches) into the rock and generated small piles of 'tailings' or rock dust around the central hole, which is about 4.5 centimeters (1.7 inches) across. The image from sol 66 of the mission was acquired using the panoramic camera's 430 nanometer filter.

  17. Hungry for Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image from the Mars Exploration Rover Spirit hazard identification camera shows the rover's perspective just before its first post-egress drive on Mars. On Sunday, the 15th martian day, or sol, of Spirit's journey, engineers drove Spirit approximately 3 meters (10 feet) toward its first rock target, a football-sized, mountain-shaped rock called Adirondack (not pictured). In the foreground of this image are 'Sashimi' and 'Sushi' - two rocks that scientists considered investigating first. Ultimately, these rocks were not chosen because their rough and dusty surfaces are ill-suited for grinding.

  18. Characterizing the hypersiliceous rocks of Belgium used in (pre-)history: a case study on sourcing sedimentary quartzites

    NASA Astrophysics Data System (ADS)

    Veldeman, Isis; Baele, Jean-Marc; Goemaere, Eric; Deceukelaire, Marleen; Dusar, Michiel; De Doncker, H. W. J. A.

    2012-08-01

    Tracking raw material back to its extraction source is a crucial step for archaeologists when trying to deduce migration patterns and trade contacts in (pre-)history. Regarding stone artefacts, the main rock types encountered in the archaeological record of Belgium are hypersiliceous rocks. This is a newly introduced category of rock types comprising those rocks made of at least 90% silica. These are strongly silicified quartz sands or sedimentary quartzites, siliceous rocks of chemical and biochemical origin (e.g. flint), very pure metamorphic quartzites and siliceous volcanic rocks (e.g. obsidian). To be able to distinguish between different extraction sources, ongoing research was started to locate possible extraction sources of hypersiliceous rocks and to characterize rocks collected from these sources. Characterization of these hypersiliceous rocks is executed with the aid of optical polarizing microscopy, optical cold cathodoluminescence and scanning-electron microscopy combined with energy-dispersive x-ray spectrometry and with back-scatter electron imaging. In this paper, we focus on various sedimentary quartzites of Paleogene stratigraphical level.

  19. Silicate weathering and CO2 consumption within agricultural landscapes, the Ohio-Tennessee River Basin, USA

    NASA Astrophysics Data System (ADS)

    Fortner, S. K.; Lyons, W. B.; Carey, A. E.; Shipitalo, M. J.; Welch, S. A.; Welch, K. A.

    2012-03-01

    Myriad studies have shown the extent of human alteration to global biogeochemical cycles. Yet, there is only a limited understanding of the influence that humans have over silicate weathering fluxes; fluxes that have regulated atmospheric carbon dioxide concentrations and global climate over geologic timescales. Natural landscapes have been reshaped into agricultural ones to meet food needs for growing world populations. These processes modify soil properties, alter hydrology, affect erosion, and consequently impact water-soil-rock interactions such as chemical weathering. Dissolved silica (DSi), Ca2+, Mg2+, NO3-, and total alkalinity were measured in water samples collected from five small (0.0065 to 0.383 km2) gauged watersheds at the North Appalachian Experimental Watershed (NAEW) near Coshocton, Ohio, USA. The sampled watersheds in this unglaciated region include: a forested site (70+ year stand), mixed agricultural use (corn, forest, pasture), an unimproved pasture, tilled corn, and a recently (<3 yr) converted no-till corn field. The first three watersheds had perennial streams, but the two corn watersheds only produced runoff during storms and snowmelt. For the perennial streams, total discharge was an important control of dissolved silicate transport. Median DSi yields (2210-3080 kg km-2 yr-1) were similar to the median of annual averages between 1979-2009 for the much larger Ohio-Tennessee River Basin (2560 kg km-2 yr-1). Corn watersheds, which only had surface runoff, had substantially lower DSi yields (<530 kg km-2 yr-1) than the perennial-flow watersheds. The lack of contributions from Si-enriched groundwater largely explained their much lower DSi yields with respect to sites having baseflow. A significant positive correlation between the molar ratio of (Ca2++Mg2+)/alkalinity to DSi in the tilled corn and the forested site suggested, however, that silicate minerals weathered as alkalinity was lost via enhanced nitrification resulting from fertilizer

  20. X-ray fluorescence analysis with micro glass beads using milligram-scale siliceous samples for archeology and geochemistry

    NASA Astrophysics Data System (ADS)

    Ichikawa, Shintaro; Nakamura, Toshihiro

    2014-06-01

    A micro glass bead technique was developed to assay precious siliceous samples for geochemical and archeological analyses. The micro-sized (approximately 3.5 mm in diameter and 0.8 mm in height) glass beads were prepared by mixing and fusing 1.1 mg of the powdered sample and 11.0 mg of the alkali lithium tetraborate flux for wavelength-dispersive X-ray fluorescence determination of major oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, and total Fe2O3). The preparation parameters, including temperature and agitation during the fusing process, were optimized for the use of a commercial platinum crucible rather than a custom-made crucible. The procedure allows preparation of minute sample amounts of siliceous samples using conventional fusing equipment. Synthetic calibration standards were prepared by compounding chemical reagents such as oxides, carbonates, and diphosphates. Calibration curves showed good linearity with r values > 0.997, and the lower limits of detection were in the 10s to 100s of μg g- 1 range (e.g., 140 μg g- 1 for Na2O, 31 μg g- 1 for Al2O3, and 8.9 μg g- 1 for MnO). Using the present method, we determined ten major oxides in igneous rocks, stream sediments, ancient potteries, and obsidian. This was applicable to siliceous samples with various compositions, because of the excellent agreement between the analytical and recommended values of six geochemical references. This minimal-scale analysis may be available for precious and limited siliceous samples (e.g., rock, sand, soil, sediment, clay, and archeological ceramics) in many fields such as archeology and geochemistry.

  1. Steps toward interstellar silicate mineralogy. V. Thermal Evolution of Amorphous Magnesium Silicates and Silica

    NASA Astrophysics Data System (ADS)

    Fabian, D.; Jäger, C.; Henning, Th.; Dorschner, J.; Mutschke, H.

    2000-12-01

    The thermally induced amorphous-to-crystalline transition has been studied for bulk sheets and micrometre-sized particles of magnesium silicate glass (MgSiO3), nanometre-sized amorphous magnesium silicate (MgSiO3 and Mg2SiO4 smokes) and amorphous silica particles (SiO2). Silicate glass was produced by the shock-quenching of melts. Samples of nanometre-sized smoke particles have been obtained by the laser ablation technique. Both the MgSiO3 and the Mg2SiO4 smokes have been found to consist of two particle species; particles of smaller size ranging in diametre from 10 nm to about 100 nm and bigger size ranging from a few 100 nm to almost 3 micrometres in diametre. Nanometre-sized particles have been shown to be depleted in magnesium whereas the micrometre-sized particles were found to be enriched in Mg. Generally, the particles are composed of nonstoichiometric magnesium silicates with compositions varying even inside of the particles. Frequently, the particles contained internal voids that are assumed to have been formed by thermal shrinkage or outgassing of the particles' interior during cooling. Annealing at 1000 K transformed the magnesium silicate smokes into crystalline forsterite (c-Mg2SiO4), tridymite (a crystalline modification of SiO2) and amorphous silica (a-SiO2) according to the initial Mg/Si-ratio of the smoke. Crystallization took place within a few hours for the Mg2SiO4 smoke and within one day for the MgSiO3 smoke. The MgSiO3 glass evolved more slowly because crystallization started at the sample surface. It has been annealed at temperatures ranging from 1000 to 1165 K. In contrast to the smoke samples, MgSiO3 glass crystallized as orthoenstatite (MgSiO3). Only after 50 hours of annealing at 1000 K, weak indications of forsterite and tridymite formation have been found in the X-ray diffraction spectra. At a temperature of 1000 K, amorphous silica nanoparticles showed distinctly lower rates of thermal evolution compared with the magnesium silicates

  2. SILICATES FOR CORROSION CONTROL IN BUILDING POTABLE WATER SYSTEMS

    EPA Science Inventory

    Silicates have been used to control the corrosion of drinking water distribution system materials. Previous work has shown that they are particularly useful in reducing the release of zinc from galvanized materials in hot water systems. Negatively charged silicate species were re...

  3. Grain properties of crystalline silicate in Oort cloud comets II

    NASA Astrophysics Data System (ADS)

    Ootsubo, Takafumi

    2014-01-01

    Crystalline silicate is sometimes observed in comets as an 11.3-micron resonant emission feature, and may be used for probing the early solar nebula. Because the formation of the crystalline silicate grains requires high temperature, they are thought to be born from amorphous silicates at the inner region, and then transported toward the outer region where comets were born. This transportation can produce the difference in the fraction of crystalline silicate in the cometary dust between two dynamical types of comets, Oort-cloud comets (OCs) and Ecliptic comets (ECs), due to the different heliocentric distances of their birth places. Recently, it is suggested that infrared spectra and peak wavelengths of silicate (forsterite) features depend on particle shapes. From this point of view, peak wavelengths of crystalline silicate features in comet spectra are important to investigate the conditions of the crystalline silicate formation in the early solar nebula. Fortunately, we can observe the comet C/2012 K1 (PanSTARRS) along with C/2012 X1 (LINEAR) in this semester. In particular, the comet C/2012 K1 is a bright and good target for this silicate peak feature study.

  4. 78 FR 14540 - Cyromazine, Silica Silicates (Silica Dioxide and Silica Gel), Glufosinate Ammonium, Dioctyl...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-06

    ... AGENCY Cyromazine, Silica Silicates (Silica Dioxide and Silica Gel), Glufosinate Ammonium, Dioctyl Sodium... the registration review of cyromazine, silica silicates (silica dioxide and silica gel), glufosinate...). Silica silicates, silicon dioxide and silica gel, are insecticides and acaracides used in...

  5. Submarine weathering of silicate minerals and the extent of pore water freshening at active continental margins

    NASA Astrophysics Data System (ADS)

    Scholz, Florian; Hensen, Christian; Schmidt, Mark; Geersen, Jacob

    2013-01-01

    In order to investigate how submarine weathering processes may affect the water balance of sediments at convergent plate margins, six sediment cores were retrieved off Central Chile at water depth between ˜800 and 4000 m. The sediment solid phase was analyzed for its major element composition and the pore fluids were analyzed for dissolved sulfate, sulfide, total alkalinity, major cations, chloride, bromide, iodide, hydrocarbons as well as the carbon isotopic composition of methane. Because of negligible weathering on land, surface sediments off Central Chile are rich in reactive silicate minerals and have a bulk composition similar to volcanic rocks in the adjacent Andes. Deep-sourced fluxes of alkalinity, cations and chloride indicate that silicate minerals are subject to weathering in the forearc during burial. Comparison of deep-sourced signals with data from nearby Ocean Drilling Program Sites reveals two different types of weathering processes: In shallow (tens of meters), methanic sediments of slope basins with high organic carbon burial rates, reactive silicate minerals undergo incongruent dissolution through reaction with CO2 from methanogenesis. At greater burial depth (hundreds of meters), silicate weathering is dominated by authigenic smectite formation. This process is accompanied by uptake of water into the clay interlayers thus leading to elevated salinities in the surrounding pore water. Deep-seated smectite formation is more widespread than shallow silicate dissolution, as it is independent from the availability of CO2 from methanogenesis. Although solute transport is not focused enough to form cold seeps in the proper sense, tectonically induced, diffuse fluid flow transfers the deep-seated signal of smectite formation into the shallow sediments. The temperature-controlled conversion of smectite to illite is considered the most important dehydration process in marine forearc environments (depth of kilometers). However, in agreement with other

  6. Melt inclusion evidence of second immiscibility within a magma derived non-silicate phase (Mt Vesuvius)

    NASA Astrophysics Data System (ADS)

    Fulignati, P.; Kamenetsky, V.; Marianelli, P.; Sbrana, A.

    2003-04-01

    Processes of melt immiscibility occurring during late magmatic differentiation play important role in the generation of many magmatic-hydrothermal ore deposits and may activate and control the style of volcanic eruptions. The exsolution of a non-silicate, volatile-rich phase from the phonolitic magma occurred at the peripheral parts of the 79AD Vesuvius magma chamber. The results of our work suggest that this immiscible phase can further experience another unmixing event that occurs in essentially "post-magmatic" environment. Heating/cooling experiments were carried out on the cogenetic multiphase (clear daughter crystals + vapour bubble(s) + interstial liquid) inclusions, hosted in K-feldspar of cognate felsic xenoliths, representative of rocks in the peripheral parts of the magma chamber. During heating, solid phases begin to dissolve at about 150^oC and melt completely at 530^oC. These low temperatures of melting argue for a non-silicate composition of daughter minerals, and thus bulk inclusion content. The remaining vapour bubble dissolves at 880^oC. During subsequent cooling, vapour bubble nucleates at 785^oC and increases in size. Unmixing of at least two melt phases occurs instantaneously at 500^oC in all studied inclusions. Globules of one melt float freely in the matrix of another melt, change their shape and size, coalesce and split apart continuously down to 100--150^oC. The movements of globules slow down with decreasing temperature until final solidification at 40--50^oC. The similarity of observed phase transformations inside inclusions suggests their homogeneous trapping at magmatic temperatures. By analogy with results of the study of xenoliths from the Vesuvius 472AD eruption (Fulignati et al., 2001) we interpret unmixed phases as globules of the Na-K chloride melt set in the matrix of Ca-carbonate melt. We infer that immiscibility between low viscosity, highly fugitive non-silicate melts may significantly influence partitioning of metals

  7. Scope of Silicic Magmatism Associated With the Snake River Plain-Yellowstone (SRPY) "Hotspot" Track

    NASA Astrophysics Data System (ADS)

    Leeman, W. P.

    2007-12-01

    Eruptive volumes of silicic volcanic rocks provide indirect albeit minimal indications of the scale of magmatism associated with the SRPY hotspot track. Coherent eruptive centers at Yellowstone produced ca. 6000 km3 of high silica rhyolite over &~2 m.y. whereas the Bruneau-Jarbidge center in the central SRP produced as much as 10,000 km3 between 12.7 and 8 Ma. Total magma volumes could be significantly larger. About half erupted as 'supervolcano class` ignimbrites (i.e., exceeding 103 km3). Implicitly, such volumes must be on-tap at least periodically during the lifetime of an eruptive center but heterogeneities in mineral populations imply that magma may be derived from a plexus of isolated pockets in the crust (`crustal sponge`) rather than a well-mixed chamber. Magmatism was strongly bimodal - 'A-type' high silica rhyolite and basalt - intermediate composition lavas are rare. Moreover, each center produced rhyolite for 2-3 m.y. prior to the onset of basaltic volcanism which dominated subsequent activity. Nearly all SRPY rhyolites carry anhydrous mineral assemblages and mineral thermometry indicates high magmatic temperatures (typically >850-900°C). Radiogenic isotopes (Sr-Nd-Pb), trace element patterns, and low 18O in many SRPY rhyolites implicate a crustal source, although Nd isotopic data preclude large contributions from Archean crust. Silicic volcanism initiated in N-central Nevada ca. 16 Ma and migrated to Yellowstone by 2 Ma. However, the pattern of silicic eruptions was not simply progressive in space and time. Between 11.5-10 Ma major silicic eruptions occurred over a swath of more than 400 km - signifying availability of diverse rhyolite magmas beneath much of the SRP. Assuming that crustal melting was driven by basaltic intrusions, such magmas must have been generated beneath much of the province prior to 10 Ma - in part, well in advance of the postulated position of the Yellowstone hotspot at that time. The quantity of basalt needed to power SRPY

  8. Mapping of hydrothermally altered rocks using airborne multispectral scanner data, Marysvale, Utah, mining district

    USGS Publications Warehouse

    Podwysocki, M.H.; Segal, D.B.; Jones, O.D.

    1983-01-01

    Multispectral data covering an area near Marysvale, Utah, collected with the airborne National Aeronautics and Space Administration (NASA) 24-channel Bendix multispectral scanner, were analyzed to detect areas of hydrothermally altered, potentially mineralized rocks. Spectral bands were selected for analysis that approximate those of the Landsat 4 Thematic Mapper and which are diagnostic of the presence of hydrothermally derived products. Hydrothermally altered rocks, particularly volcanic rocks affected by solutions rich in sulfuric acid, are commonly characterized by concentrations of argillic minerals such as alunite and kaolinite. These minerals are important for identifying hydrothermally altered rocks in multispectral images because they have intense absorption bands centered near a wavelength of 2.2 ??m. Unaltered volcanic rocks commonly do not contain these minerals and hence do not have the absorption bands. A color-composite image was constructed using the following spectral band ratios: 1.6??m/2.2??m, 1.6??m/0.48??m, and 0.67??m/1.0??m. The particular bands were chosen to emphasize the spectral contrasts that exist for argillic versus non-argillic rocks, limonitic versus nonlimonitic rocks, and rocks versus vegetation, respectively. The color-ratio composite successfully distinguished most types of altered rocks from unaltered rocks. Some previously unrecognized areas of hydrothermal alteration were mapped. The altered rocks included those having high alunite and/or kaolinite content, siliceous rocks containing some kaolinite, and ash-fall tuffs containing zeolitic minerals. The color-ratio-composite image allowed further division of these rocks into limonitic and nonlimonitic phases. The image did not allow separation of highly siliceous or hematitically altered rocks containing no clays or alunite from unaltered rocks. A color-coded density slice image of the 1.6??m/2.2??m band ratio allowed further discrimination among the altered units. Areas

  9. Laboratory Studies on Silicates Relevant for the Physics of TNOs

    NASA Astrophysics Data System (ADS)

    Brucato, John Robert; Strazzulla, Giovanni; Baratta, Giuseppe; Mennella, Vito; Colangeli, Luigi

    2003-06-01

    Silicates are one of the principal components present in Solar System objects. Silicates evolve in space modifying their physical properties according to the astronomical environments they go through. To characterise the nature of TNOs in the framework of the formation and evolution of the Solar System, experiments on structural transitions of silicates have been performed in the laboratory to simulate some of the processing suffered by the dust. The infrared spectral properties of possible silicate candidates thought to be present in TNOs have been studied. The results of thermal annealing of amorphous silicates and amorphisation of crystalline forsterite (pure-Mg olivine) by ion irradiation are presented. The observable properties of TNOs surfaces are inferred.

  10. Optical Properties of Astronomical Silicates in the Far-infrared

    NASA Technical Reports Server (NTRS)

    Rinehart, Stephen A,; Benford, Dominic J.; Dwek, Eli; Henry, Ross M.; Nuth, Joseph A., III; Silverberg, Robert f.; Wollack, Edward J.

    2008-01-01

    Correct interpretation of a vast array of astronomical data relies heavily on understanding the properties of silicate dust as a function of wavelength, temperature, and crystallinity. We introduce the QPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project to address the need for high fidelity optical characterization data on the various forms of astronomical dust. We use two spectrometers to provide extinction data for silicate samples across a wide wavelength range (from the near infrared to the millimeter). New experiments are in development that will provide complementary information on the emissivity of our samples, allowing us to complete the optical characterization of these dust materials. In this paper, we present initial results from several materials including amorphous iron silicate, magnesium silicate and silica smokes, over a wide range of temperatures, and discuss the design and operation of our new experiments.

  11. Optical Properties of Astronomical Silicates in the Far-infrared

    NASA Technical Reports Server (NTRS)

    Rinehart, Stephen A,; Benford, Dominic J.; Dwek, Eli; Henry, Ross M.; Nuth, Joseph A., III; Silverberg, Robert f.; Wollack, Edward J.

    2008-01-01

    Correct interpretation of a vast array of astronomical data relies heavily on understanding the properties of silicate dust as a function of wavelength, temperature, and crystallinity. We introduce the QPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project to address the need for high fidelity optical characterization data on the various forms of astronomical dust. We use two spectrometers to provide extinction data for silicate samples across a wide wavelength range (from the near infrared to the millimeter). New experiments are in development that will provide complementary information on the emissivity of our samples, allowing us to complete the optical characterization of these dust materials. In this paper, we present initial results from several materials including amorphous iron silicate, magnesium silicate and silica smokes, over a wide range of temperatures, and discuss the design and operation of our new experiments.

  12. The identification of crystalline olivine in cometary silicates

    NASA Technical Reports Server (NTRS)

    Campins, Humberto; Ryan, Eileen V.

    1989-01-01

    An intermediate-resolution spectrum of the 8-13 micron region in comet Halley is obtained which shows a prominent silicate emission feature with structure not observed before in other comets or in interstellar silicates. The presence of a strong 11.3 micron peak reported by Bregman and coworkers is confirmed, and evidence is found for additional structure in the band. By comparison with spectra of interplanetary dust particles and laboratory silicates, it is concluded that small crystalline olivine particles are a major component of the silicates in this comet; other silicates (e.g., amorphous or hydrated) must also be present. The identification of crystalline olivine in this part of the spectrum is supported by the observation of four peaks in 20-50 micron airborne spectra of this comet which have also been attributed to olivine.

  13. Immobilisation of fully sulfonated polyaniline on nanostructured calcium silicate.

    PubMed

    Borrmann, Thomas; Dominis, Anton; McFarlane, Andrew J; Johnston, James H; Richardson, Michael J; Kane-Maguire, Leon A P; Wallace, Gordon G

    2007-12-01

    Up to 7.4% (w/w) of the sulfonated polyaniline, poly(2-methoxyaniline-5-sulfonic acid) (PMAS) can be absorbed onto nanostructured calcium silicates. Spectroscopic and leaching studies on the novel PMAS-silicate nanocomposites obtained indicate that attachment of the PMAS occurs via electrostatic binding of PMAS sulfonate groups to Ca2+ sites on the silicates. The surface area and pore volume of the nanocomposites are comparable to those of pure silicate and increase the surface area of the PMAS polymer by several orders of magnitude. The PMAS emeraldine salt in the nanocomposites retains its chemical reactivity, being readily oxidised and reduced to its pernigraniline and leucoemeraldine forms, respectively. The conductivity of the composite is comparable to that of the pure PMAS, several orders of magnitude higher than that of dried nanostructured calcium silicate.

  14. Silicate Inclusions in the Kodaikanal IIE Iron Meteorite

    NASA Technical Reports Server (NTRS)

    Kurat, G.; Varela, M. E.; Zinner, E.

    2005-01-01

    Silicate inclusions in iron meteorites display an astonishing chemical and mineralogical variety, ranging from chondritic to highly fractionated, silica- and alkali-rich assemblages. In spite of this, their origin is commonly considered to be a simple one: mixing of silicates, fractionated or unfractionated, with metal. The latter had to be liquid in order to accommodate the former in a pore-free way which all models accomplish by assuming shock melting. II-E iron meteorites are particularly interesting because they contain an exotic zoo of silicate inclusions, including some chemically strongly fractionated ones. They also pose a formidable conundrum: young silicates are enclosed by very old metal. This and many other incompatibilities between models and reality forced the formulation of an alternative genetic model for irons. Here we present preliminary findings in our study of Kodaikanal silicate inclusions.

  15. The identification of crystalline olivine in cometary silicates

    NASA Technical Reports Server (NTRS)

    Campins, Humberto; Ryan, Eileen V.

    1989-01-01

    An intermediate-resolution spectrum of the 8-13 micron region in comet Halley is obtained which shows a prominent silicate emission feature with structure not observed before in other comets or in interstellar silicates. The presence of a strong 11.3 micron peak reported by Bregman and coworkers is confirmed, and evidence is found for additional structure in the band. By comparison with spectra of interplanetary dust particles and laboratory silicates, it is concluded that small crystalline olivine particles are a major component of the silicates in this comet; other silicates (e.g., amorphous or hydrated) must also be present. The identification of crystalline olivine in this part of the spectrum is supported by the observation of four peaks in 20-50 micron airborne spectra of this comet which have also been attributed to olivine.

  16. Elucidating the magmatic history of the Austurhorn silicic intrusive complex (southeast Iceland) using zircon elemental and isotopic geochemistry and geochronology

    NASA Astrophysics Data System (ADS)

    Padilla, A. J.; Miller, C. F.; Carley, T. L.; Economos, R. C.; Schmitt, A. K.; Coble, M. A.; Wooden, J. L.; Fisher, C. M.; Vervoort, J. D.; Hanchar, J. M.

    2016-09-01

    The Austurhorn intrusive complex (AIC) in southeast Iceland comprises large bodies of granophyre and gabbro, and a mafic-silicic composite zone (MSCZ) that exemplifies magmatic interactions common in Icelandic silicic systems. Despite being one of Iceland's best-studied intrusions, few studies have included detailed analyses of zircon, a mineral widely recognized as a valuable tracer of the history and evolution of its parental magma(s). In this study, we employ high spatial resolution zircon elemental and isotopic geochemistry and U-Pb geochronology as tools for elucidating the complex construction and magmatic evolution of Austurhorn's MSCZ. The trace element compositions of AIC zircon crystals form a broad but coherent array that partly overlaps with the geochemical signature for zircons from Icelandic silicic volcanic rocks. Typical of Icelandic zircons, Hf concentrations are relatively low (<10,000 ppm) and Ti concentrations range from 5 to 40 ppm (Ti-in-zircon model temperatures = 761-981 °C). Zircon δ18O values vary from +2.2 to +4.8 ‰, consistent with magmatic zircons from other Icelandic silicic rocks, and preserve evidence for recycling of hydrothermally altered crust as a significant contribution to the generation of silicic magmas within the AIC. Zircon ɛ Hf values generally range from +11 to +15. This range overlaps with that of Icelandic basalts from off-rift settings as well as the least depleted rift basalts, suggesting that the AIC developed within a transitional rift environment. In situ zircon U-Pb ages yield a weighted mean of 6.52 ± 0.03 Ma for the entire complex, but span a range of ~320 kyr, from 6.35 ± 0.08 to 6.67 ± 0.06 Ma (2 σ SE). Gabbros and the most silicic units make up the older part of this range, while granophyres and intermediate units make up the younger part of the complex, consistent with field relationships. We interpret the ~320 kyr range in zircon ages to represent the approximate timescale of magmatic construction

  17. Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury

    NASA Astrophysics Data System (ADS)

    Namur, Olivier; Charlier, Bernard; Holtz, Francois; Cartier, Camille; McCammon, Catherine

    2016-08-01

    Chemical data from the MESSENGER spacecraft revealed that surface rocks on Mercury are unusually enriched in sulfur compared to samples from other terrestrial planets. In order to understand the speciation and distribution of sulfur on Mercury, we performed high temperature (1200-1750 °C), low- to high-pressure (1 bar to 4 GPa) experiments on compositions representative of Mercurian lavas and on the silicate composition of an enstatite chondrite. We equilibrated silicate melts with sulfide and metallic melts under highly reducing conditions (IW-1.5 to IW-9.4; IW = iron-wüstite oxygen fugacity buffer). Under these oxygen fugacity conditions, sulfur dissolves in the silicate melt as S2- and forms complexes with Fe2+, Mg2+ and Ca2+. The sulfur concentration in silicate melts at sulfide saturation (SCSS) increases with increasing reducing conditions (from <1 wt.% S at IW-2 to >10 wt.% S at IW-8) and with increasing temperature. Metallic melts have a low sulfur content which decreases from 3 wt.% at IW-2 to 0 wt.% at IW-9. We developed an empirical parameterization to predict SCSS in Mercurian magmas as a function of oxygen fugacity (fO2), temperature, pressure and silicate melt composition. SCSS being not strictly a redox reaction, our expression is fully valid for magmatic systems containing a metal phase. Using physical constraints of the Mercurian mantle and magmas as well as our experimental results, we suggest that basalts on Mercury were free of sulfide globules when they erupted. The high sulfur contents revealed by MESSENGER result from the high sulfur solubility in silicate melt at reducing conditions. We make the realistic assumption that the oxygen fugacity of mantle rocks was set during equilibration of the magma ocean with the core and/or that the mantle contains a minor metal phase and combine our parameterization of SCSS with chemical data from MESSENGER to constrain the oxygen fugacity of Mercury's interior to IW- 5.4 ± 0.4. We also calculate that

  18. Germanium isotopic variations in igneous rocks and marine sediments

    NASA Astrophysics Data System (ADS)

    Rouxel, Olivier; Galy, Albert; Elderfield, Henry

    2006-07-01

    A new technique for the precise and accurate determination of Ge stable isotope compositions has been developed and applied to silicate rocks and biogenic opal. The analyses were performed using a continuous flow hydride generation system coupled to a MC-ICPMS. Samples have been purified through anion- and cation-exchange resins to separate Ge from matrix elements and eliminate potential isobaric interferences. Variations of 74Ge/ 70Ge ratios are expressed as δ74Ge values relative to our internal standard and the long-term external reproducibility of the data is better than 0.2‰ for sample size as low as 15 ng of Ge. Data are presented for igneous and sedimentary rocks, and the overall variation is 2.4‰ in δ74Ge, representing 12 times the uncertainty of the measurements and demonstrating that the terrestrial isotopic composition of Ge is not unique. Co-variations of 74Ge/ 70Ge, 73Ge/ 70Ge and 72Ge/ 70Ge ratios follow a mass-dependent behaviour and imply natural isotopic fractionation of Ge by physicochemical processes. The range of δ74Ge in igneous rocks is only 0.25‰ without systematic differences among continental crust, oceanic crust or mantle material. On this basis, a Bulk Silicate Earth reservoir with a δ74Ge of 1.3 ± 0.2‰ can be defined. In contrast, modern biogenic opal such as marine sponges and authigenic glauconite displayed higher δ74Ge values between 2.0‰ and 3.0‰. This suggests that biogenic opal may be significantly enriched in light isotopes with respect to seawater and places a lower bound on the δ74Ge of the seawater to +3.0‰.This suggests that seawater is isotopically heavy relative to Bulk Silicate Earth and that biogenic opal may be significantly fractionated with respect to seawater. Deep-sea sediments are within the range of the Bulk Silicate Earth while Mesozoic deep-sea cherts (opal and quartz) have δ74Ge values ranging from 0.7‰ to 2.0‰. The variable values of the cherts cannot be explained by binary mixing

  19. Carbonate turbidites in volcaniclastic metasedimentary rocks of the Mineral Bluff, Fm, Murphy, NC

    SciTech Connect

    Fritz, W.J.; La Tour, T.E.; Stakes, D.S.

    1985-01-01

    Outcrops of the metasedimentary Mineral Bluff Fm near Murphy, North Carolina contain thin lenses to discontinuous layers of calc-silicate in volcaniclastic mudstone. Despite the metamorphism, sedimentary structures preserved in the mudstones include: ripple cross laminations, scour surfaces, crossbedding and graded beds. The calc-silicate layers vary from 2-25cm thick and are zoned from carbonate-rich center to silicate-rich margins. May layers have no carbonate center preserved. Major calc-silicate minerals are carbonate, plagioclase, hornblende, Ca-garnet, and quartz; accessory minerals are clinozoisite, apatite, Fe-Ti oxides, and pyrite. Siltstone immediately adjacent to calc-silicate layers contains much biotite whose abundance decreases away from the calc-silicate layers. Greater original carbonate in siltstone nearest carbonate layers would have facilitated biotite growth. Within calc-silicate layers, hornblende is concentrated near both margins, but in greater concentration near stratigraphic tops. The authors also interpret this as grading within original muddy carbonate turbidites. The calc-silicate turbidite layers may have been derived from the nearby Murphy Marble, a large time-equivalent late Proterozoic or early Paleozoic carbonate unit. The Murphy Marble was a large shallow water carbonate reef associated with an island arc. Other time-equivalent, nearshore rock units in the area are the beach sandstone of the Nottely Quartzite and the locally carbonate-rich volcaniclastic Brasstown Formation. The authors envisage the depositional environment for the Mineral Bluff Fm as a deep basin, distal from the island arc, that received fine-grained volcaniclastic debris from the arc, episodically interrupted by a carbonate turbidity flow.

  20. Organics Synthesized Using Iron-Grain Silicates

    NASA Technical Reports Server (NTRS)

    Johnson, N. M.; Cody, G. D.; Nuth, J. A., III

    2003-01-01

    We use Fischer-Tropsch type (FTT) synthesis to produce hydrocarbons by hydrogenating carbon monoxide via catalytic reactions. The products of these reactions have been studied using 'natural' catalysts and calculations of the efficiency of FTT synthesis in the Solar Nebula suggest that these types of reactions could make significant contributions to the composition of material near three AU. We coat Fe-silicate grains with organic material using FTT synthesis to simulate the chemistry in the early Solar Nebula. In our experimental setup, we roughly model a nebular environment where grains are successively transported from hot to cold regions of the nebula. In other words, the starting gases and FTT products are continuously circulated through the grains at high temperature with intervals of cooling. Organics generated in this manner could represent the carbonaceous material incorporated in comets and meteorites. We analyze the resulting organics and present the results.

  1. Thermal Ablation Modeling for Silicate Materials

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq

    2016-01-01

    A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

  2. Cesium titanium silicate and method of making

    DOEpatents

    Balmer, Mari L.

    1997-01-01

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs.sub.2 Ti.sub.2 Si.sub.4 O.sub.13 pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs.sub.2 O and TiO.sub.2 loadings and are durable glass and ceramic materials. The amount of TiO.sub.2 and Cs.sub.2 that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass.

  3. Cesium titanium silicate and method of making

    DOEpatents

    Balmer, M.L.

    1997-01-07

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs{sub 2}Ti{sub 2}Si{sub 4}O{sub 13} pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs{sub 2}O and TiO{sub 2} loadings and are durable glass and ceramic materials. The amount of TiO{sub 2} and Cs{sub 2} that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass. 10 figs.

  4. Thermal Ablation Modeling for Silicate Materials

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq

    2016-01-01

    A thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in ablation simulations of the meteoroid or glassy Thermal Protection Systems for spacecraft. Time-dependent axi-symmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. For model validation, the surface recession of fused amorphous quartz rod is computed, and the recession predictions reasonably agree with available data. The present parametric studies for two groups of meteoroid earth entry conditions indicate that the mass loss through moving molten layer is negligibly small for heat-flux conditions at around 1 MW/cm(exp. 2).

  5. Procedure for estimating salinity distribution based on resistivity data for a rock mass

    NASA Astrophysics Data System (ADS)

    Mizuno, T.; Iwatsuki, T.; Matsuzaki, T.

    2012-12-01

    Site characterization work will be conducted to understand the geological environment around any site of possible interest for geological disposal of HLW. An approach to reduce uncertainty in the understanding of a geological environment is to increase the investigation density. However, it can be costly and time consuming. Therefore, any increase in investigation density should be done as effectively as possible. Hydrochemical properties, essential characteristics of any geological environment, are developed using hydrochemical data. The data are generally obtained by chemical analyses of groundwater samples from boreholes. However, hydrochemical samples, though taken selectively are not continuous and thus hydrochemical data are point data. On the other hand, the resistivity data, determined using continuous borehole geophysical logging, can be used to estimate the hydrochemical (salinity) distribution. Therefore, if salinity distributions can be estimated from resistivity data, investigation density would be effectively higher. This study has aimed to develop the methodology for estimation of salinity distribution by resistivity data of the boreholes drilled around the Horonobe URL in Hokkaido, northern Japan. JAEA has established the URL as a part of the national R&D program for geological disposal of HLW. In addition, the technical knowledge and know-how learnt through this study are summarized as a "case-base (data base of investigation examples)" to incorporate into the Information Synthesis and Interpretation System (ISIS) that has been developed by JAEA for the Ministry of Economy, Trade and Industry, as a part of its supporting program in 2007. The procedure for estimation of salinity is as follows; (1) Confirmation the applicability of the data of resistivity logging, (2) Conversion of resistivity data to salinity, (3) Comparison of the results of chemical analyses and the calculated results in (2). This study shows that calculated salinity agree well

  6. Mars Rock Analysis Briefing

    NASA Image and Video Library

    2013-03-12

    John Grotzinger (second from left), Curiosity project scientist, California Institute of Technology in Pasadena, speaks at a news conference presenting findings of the Curiosity rover's analysis of the first sample of rock powder collected on Mars, Tuesday, March 12, 2013 in Washington. The rock sample collected shows ancient Mars could have supported living microbes. Photo Credit: (NASA/Carla Cioffi)

  7. Mars Rock Analysis Briefing

    NASA Image and Video Library

    2013-03-12

    John Grotzinger, Curiosity project scientist, California Institute of Technology in Pasadena, answers a reporter's question at a news conference where findings of the Curiosity rover's analysis of the first sample of rock powder collected on Mars were presented, Tuesday, March 12, 2013 in Washington. The rock sample collected shows ancient Mars could have supported living microbes. Photo Credit: (NASA/Carla Cioffi)

  8. Mars Rock Analysis Briefing

    NASA Image and Video Library

    2013-03-12

    John Grotzinger (center), Curiosity project scientist, California Institute of Technology in Pasadena, speaks at a news conference presenting findings of the Curiosity rover's analysis of the first sample of rock powder collected on Mars, Tuesday, March 12, 2013 in Washington. The rock sample collected shows ancient Mars could have supported living microbes. Photo Credit: (NASA/Carla Cioffi)

  9. Session: Hard Rock Penetration

    SciTech Connect

    Tennyson, George P. Jr.; Dunn, James C.; Drumheller, Douglas S.; Glowka, David A.; Lysne, Peter

    1992-01-01

    This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five presentations: ''Hard Rock Penetration - Summary'' by George P. Tennyson, Jr.; ''Overview - Hard Rock Penetration'' by James C. Dunn; ''An Overview of Acoustic Telemetry'' by Douglas S. Drumheller; ''Lost Circulation Technology Development Status'' by David A. Glowka; ''Downhole Memory-Logging Tools'' by Peter Lysne.

  10. Rock Bites into 'Bounce'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This panoramic camera image from the Mars Exploration Rover Opportunity features the 6.44 millimeter (0.25 inch) deep hole ground into the rock dubbed 'Bounce' by the rover's rock abrasion tool. The tool took 2 hours and 15 minutes to grind the hole on sol 66 of the rover's journey. A combination of limited solar power and the rock's jagged texture led the rock abrasion tool team to set very aggressive grinding parameters to ensure that the end result was a full circle, suitable for a thorough read from the rover's spectrometers.

    Bounce's markedly different appearance (when compared to the rocks that were previously examined in the Eagle Crater outcrop) made it a natural target for rover research. In order to achieve an ideal position from which to grind into the rock, Opportunity moved in very close with its right wheel next to Bounce. In this image, the panoramic camera on the rover's mast is looking down, catching the tip of the solar panel which partially blocks the full circle ground by the rock abrasion tool.

    The outer ring consists of the cuttings from the rock, pushed out by the brushes on the grinding instrument. The dark impression at the top of the outer circle was caused by the instrument's contact mechanism which serves to stabilize it while grinding.

  11. Odyssey/White Rock

    NASA Image and Video Library

    2002-10-01

    These Mars Odyssey images show the White Rock feature on Mars in both infrared left and visible right wavelengths. White Rock is the unofficial name for this landform that was first observed during NASA Mariner 9 mission in the early 1970.

  12. Rock Cycle Roulette.

    ERIC Educational Resources Information Center

    Schmidt, Stan M.; Palmer, Courtney

    2000-01-01

    Introduces an activity on the rock cycle. Sets 11 stages representing the transitions of an earth material in the rock cycle. Builds six-sided die for each station, and students move to the stations depending on the rolling side of the die. Evaluates students by discussing several questions in the classroom. Provides instructional information for…

  13. Welcome to Rock Day

    ERIC Educational Resources Information Center

    Varelas, Maria; Benhart, Jeaneen

    2004-01-01

    At the beginning of the school year, the authors, a first-grade teacher and a teacher educator, worked together to "spice up" the first-grade science curriculum. The teacher had taught the unit Rocks, Sand, and Soil several times, conducting hands-on explorations and using books to help students learn about properties of rocks, but she felt the…

  14. Welcome to Rock Day

    ERIC Educational Resources Information Center

    Varelas, Maria; Benhart, Jeaneen

    2004-01-01

    At the beginning of the school year, the authors, a first-grade teacher and a teacher educator, worked together to "spice up" the first-grade science curriculum. The teacher had taught the unit Rocks, Sand, and Soil several times, conducting hands-on explorations and using books to help students learn about properties of rocks, but she felt the…

  15. Mars Rock Analysis Briefing

    NASA Image and Video Library

    2013-03-12

    David Blake, principal investigator for Curiosity's Chemistry and Mineralogy investigation at NASA's Ames Research Center in Calif., speaks at a news conference presenting findings of the Curiosity rover's analysis of the first sample of rock powder collected on Mars, Tuesday, March 12, 2013 in Washington. The rock sample collected shows ancient Mars could have supported living microbes. Photo Credit: (NASA/Carla Cioffi)

  16. Chocolate Hills Rock

    NASA Image and Video Library

    2010-02-16

    This false-color image, taken by the panoramic camera on NASA rover Opportunity, shows the rock Chocolate Hills, perched on the rim of the 10-meter 33-foot wide Concepcion crater. This rock has a thick, dark-colored coating resembling chocolate.

  17. Rock Cycle Roulette.

    ERIC Educational Resources Information Center

    Schmidt, Stan M.; Palmer, Courtney

    2000-01-01

    Introduces an activity on the rock cycle. Sets 11 stages representing the transitions of an earth material in the rock cycle. Builds six-sided die for each station, and students move to the stations depending on the rolling side of the die. Evaluates students by discussing several questions in the classroom. Provides instructional information for…

  18. Rock Bites into 'Bounce'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This panoramic camera image from the Mars Exploration Rover Opportunity features the 6.44 millimeter (0.25 inch) deep hole ground into the rock dubbed 'Bounce' by the rover's rock abrasion tool. The tool took 2 hours and 15 minutes to grind the hole on sol 66 of the rover's journey. A combination of limited solar power and the rock's jagged texture led the rock abrasion tool team to set very aggressive grinding parameters to ensure that the end result was a full circle, suitable for a thorough read from the rover's spectrometers.

    Bounce's markedly different appearance (when compared to the rocks that were previously examined in the Eagle Crater outcrop) made it a natural target for rover research. In order to achieve an ideal position from which to grind into the rock, Opportunity moved in very close with its right wheel next to Bounce. In this image, the panoramic camera on the rover's mast is looking down, catching the tip of the solar panel which partially blocks the full circle ground by the rock abrasion tool.

    The outer ring consists of the cuttings from the rock, pushed out by the brushes on the grinding instrument. The dark impression at the top of the outer circle was caused by the instrument's contact mechanism which serves to stabilize it while grinding.

  19. Timescale of silicic melt extraction/transport by diking from shallow intermediate crystalline-rich reservoirs: numerical modelling and case study

    NASA Astrophysics Data System (ADS)

    Gutiérrez, F. J.; Aravena, A.; Payacán, I. J.; Parada, M. Á.; Bachmann, O.

    2016-12-01

    We performed time-dependent numerical modelling of a cooling shallow magma reservoir of intermediate composition with a particular emphasis on the late-stage silicic melt extraction/transportation through dikes from a crystalline-rich mush formed during the late magmatic stage. Results show that timescales of silicic melt extraction/transport is a relatively short event consistent with crystal settling and compaction processes. We select the 10-12 Ma La Gloria pluton (LGP) as a study case of a shallow slightly zoned granodioritic pluton where leucogranitic dikes are ubiquitous in the pluton and neighboring host rocks. Simulation results indicate that, to preserve the LGP reservoir over the solidus for over 1 Ma, a continuous injection of intermediate magma is required. Residual melt extraction/transport through dikes are only possible during the last thousands of years at rates of 4-8 10-3 km3/yr, leaving a record of accumulated mineral and compositional zonation in the reservoir. According to thermal models, the mentioned modelled rates are similar than to the injection rates needed to build and maintain large silicic mushes at shallower levels. However, we suggest that it is unlikely that a small magma reservoir like LGP has fed a large silicic volcanism (>100 km3 volume), but rather low-volume silicic intrusions, such as sills and dikes preserved at higher levels, or by moderate to small volcanic eruptions (<1 km3 volume).

  20. Evidence for a tektosilicate structure and dominance of Fe(III) over Fe(II) in silicic volcanic glasses of the Nevada Test Site

    SciTech Connect

    Warren, R.G.

    1983-01-01

    More than 400 individual analyses have been obtained by electron microprobe for silicic glasses in 58 samples of tuff and lava from the Nevada Test Site (NTS). These samples comprise a wide range in chemical and petrographic types, including calc-alkaline and peralkaline rock types, and include most of the volcanic units of the NTS. Locations and brief petrographic descriptions are given for representative samples.