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obsidian

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Journal Article
Journal: Geology
Published: 05 October 2017
Geology (2017) 45 (11): 1019–1022.
..., including the Glass Mountain (GM) obsidians and the Early Bishop Tuff (e.g., Metz and Mahood, 1991 ; Hildreth and Wilson, 2007 ), or the hydrous (6–8 wt% H 2 O) Pine Grove Tuff ( Lowenstern, 1994 ) from southwestern Utah (Great Basin). An alternative hypothesis is that the key factor that determines...
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Journal Article
Published: 01 August 2017
American Mineralogist (2017) 102 (8): 1677–1689.
... of ε and glass composition. FTIR water H 2 O speciation volcanic glass rhyolite andesite hydration obsidian The dissolved water content of a silicate melt affects a range of magmatic processes, since it exerts a strong influence on melt viscosity (e.g., Hess and Dingwell 1996...
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Journal Article
Published: 01 June 2017
Italian Journal of Geosciences (2017) 136 (2): 238–262.
... as caementia . The grey-black volcanic rocks are glasses with characteristics more near to obsidian and less to natural pozzolan normally used in the Roman period. To identify the provenance of these glasses, a geochemical comparison between the samples taken from the theatre mortars and the volcanic outcrops...
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Journal Article
Journal: Geology
Published: 01 February 2017
Geology (2017) 45 (2): 183–186.
... fragments. We show that individual obsidian pyroclasts from Mono Craters, California (USA), are heterogeneous in dissolved H 2 O and CO 2 , suggesting that clasts are assembled from juvenile melt and rewelded ash during magma ascent. This is in contrast to the conventional view that clasts are chemically...
Journal Article
Journal: Geology
Published: 01 July 2015
Geology (2015) 43 (7): 647–650.
...Kenneth S. Befus; James Watkins; James E. Gardner; Dominique Richard; Kevin M. Befus; Nathan R. Miller; Donald B. Dingwell Abstract Spherulites in rhyolitic obsidian provide a record of the thermal history of their host lava during the interval of spherulite growth. We use trace element...
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Journal Article
Published: 01 June 2015
European Journal of Mineralogy (2015) 27 (3): 353–363.
..., minor and trace elements. Two main groups of natron-based silica–lime glass were identified, as well as one sample of obsidian (from Lipari Island). The majority of the samples (20) are High Iron, Manganese and Titanium (HIMT) glass. Specifically, most of them (18) can be classified as HIMT1, with only...
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Journal Article
Published: 01 April 2015
American Mineralogist (2015) 100 (4): 774–786.
...Amy G. Ryan; James K. Russell; Alexander R.L. Nichols; Kai-Uwe Hess; Lucy A. Porritt Abstract We present a suite of 36 high-temperature (900–1100 °C) experiments performed on 10 × 10 mm unjacketed cores of rhyolitic obsidian from Hrafntinnuhryggur, Krafla, Iceland, under atmospheric pressure...
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Journal Article
Published: 01 July 2014
American Mineralogist (2014) 99 (7): 1383–1403.
... material of common granitic composition (Lake County obsidian) reduces the crystallization and melting temperatures by approximately 50–70 and 200 °C, respectively, and promotes the formation of quartz-feldspar graphic and granophyric intergrowths. The presence of Li in the hydrous granitic system lowers...
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Journal Article
Published: 01 May 2014
American Mineralogist (2014) 99 (5-6): 1085–1094.
.... Powders from two natural obsidian samples were also studied and yielded results broadly similar to the synthetic model systems. SO 2 adsorption on ash is partially irreversible; it appears that the first layer of SO 2 molecules absorbed on the surface cannot be removed. The pressure and temperature...
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Journal Article
Published: 01 October 2013
The Canadian Mineralogist (2013) 51 (5): 705–714.
... the additional degree of freedom for a melt. Formation of snowflake obsidian is discussed in view of our synthesis experiments. § Corresponding author : Hofmeist@wustl.edu ; 314-935-7440; fax 935-7361 31 07 2013 06 11 2013 © The Mineralogical Association of Canada 2013 laser-flash...
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Journal Article
Journal: Geology
Published: 01 July 2013
Geology (2013) 41 (7): 779–782.
...Kurt Rademaker; Michael D. Glascock; Bruce Kaiser; David Gibson; Daniel R. Lux; Martin G. Yates Abstract We report results from comprehensive mapping and multi-technique geochemical characterization of obsidian from the Alca source in the Peruvian Andes (15.3°S, 72.7°W), aimed at understanding...
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Journal Article
Journal: Clay Minerals
Published: 01 June 2013
Clay Minerals (2013) 48 (3): 423–445.
...J. Cuadros; B. Afsin; P. Jadubansa; M. Ardakani; C. Ascaso; J. Wierzchos Abstract Rhyolitic obsidian was reacted with natural waters to study the effect of water chemistry and biological activity on the composition and formation mechanisms of clay. Two sets of experiments (18 months, 6 years) used...
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Journal Article
Journal: Geology
Published: 01 January 2013
Geology (2013) 41 (1): 7–10.
... crystallization ages for two obsidian-bearing lavas: Red Island (the host for the granophyre) and Obsidian Butte, a prehistoric quarry for obsidian that is widely distributed in southern California and northern Mexico archaeological sites. Lavas and granophyre display overlapping zircon crystallization age...
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Journal Article
Journal: Geology
Published: 01 August 2012
Geology (2012) 40 (8): 699–702.
...James M. Watkins; Michael Manga; Donald J. DePaolo Abstract Water concentration profiles around bubbles offer a new kind of geobarometer. We measure H 2 O and CO 2 concentrations in glass adjacent to bubbles in pyroclastic obsidian from Mono Craters, California (United States). H 2 O and CO 2...
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Journal Article
Journal: Geology
Published: 01 January 2011
Geology (2011) 39 (1): 67–70.
...Agustín Cabrera; Roberto F. Weinberg; Heather M.N. Wright; Sergio Zlotnik; Ray A.F. Cas Abstract We present water content transects across a healed fault in pyroclastic obsidian from Lami pumice cone, Lipari, Italy, using synchrotron Fourier transform infrared spectroscopy. Results indicate...
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Journal Article
Published: 01 September 2009
Journal of the Geological Society (2009) 166 (5): 895–904.
... spectrometry (DSC–TGA–MS) and X-ray diffraction (XRD). Samples range from pristine obsidians to strongly perlitized and altered fragmental deposits. Four types of samples are determined to have notable differences in total volatile concentrations: obsidians (0.44–3.04 wt%), perlites (2.15–8.15 wt%), obsidian...
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Series: GSA Field Guide
Published: 01 January 2009
DOI: 10.1130/2009.fld015(03)
EISBN: 9780813756158
... The volcano last erupted in late Holocene time, when initial explosive activity produced rhyolitic tephra that reached Idaho and ended with emplacement of the Big Obsidian Flow in the caldera. Early Holocene postglacial eruptions were dominantly mafic. As many as a dozen such eruptions...
Journal Article
Published: 01 November 2008
American Mineralogist (2008) 93 (11-12): 1816–1822.
...Jonathan M. Castro; Pierre Beck; Hugh Tuffen; Alexander R.L. Nichols; Donald B. Dingwell; Michael C. Martin Abstract We determined the kinetics of spherulite growth in obsidians from Krafla volcano, Iceland. We measured water concentration profiles around spherulites in obsidian by synchrotron...
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Journal Article
Published: 01 July 2008
American Mineralogist (2008) 93 (7): 1166–1178.
... temperature. Comparisons of low-temperature hydration results among SiO 2 , obsidian, and albite compositions show distinct differences, and features are present in the spectra that do not occur at high temperature. Analysis of H 2 O and D 2 O diffusion also suggest that mechanistic differences occur between...
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Journal Article
Journal: Geology
Published: 01 April 2008
Geology (2008) 36 (4): 279–282.
... the number density and CSD found in three pumice samples (Fig. 2D) . Experimental clinopyroxene CSDs do not fit the obsidian pyroclast CSDs, as they reflect much lower microlite number densities in the small size classes. The departure between experiment and nature is evident in the CSDs of obsidian...
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