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setting, Acta Vulcanologica, 2001, 13, 25–39 [46] Seghedi I., Downes H., Szakacs A., Mason P.R.D., Thirlwall M.F., Rosu E., Pecskay Z., Marton E., et al., Neogene-Quaternary magmatism and geodynam-Volcanic glass textures, shape characteristics and compositions of phreatomagmatic rock units from the Western Hungarian monogenetic volcanic fields and their implications for magma fragmentation ics in the Carpathian-Pannonian region: a synthesis, Lithos, 2004, 72, 117–146 http://dx.doi.org/10.1016/j.lithos.2003.08.006 [47] Szabó C., Harangi S., Csontos L., Review of Neogene

Abstract

Double pulse laser induced breakdown spectroscopy in orthogonal configuration was used for the analysis of twelve samples of volcanic glass. Raw material and artifact samples originated from Czech, Slovak, German, Hungarian, Greek, Turkish, and Ukrainian sites. The primary 266 nm laser beam was focused onto a sample area of about 0.1 mm in diameter at the optimised energy of 10 mJ resulting in only very slight sample damage, almost unrecognizable even by a microscope. The secondary 1064 nm laser beam, positioned parallel to the sample surface and focused onto the intersection with the primary beam, induced a spark with enhanced radiation at the optimised energy of 100 mJ. Measurement of emission lines selected on basis of chemical composition, signal intensity, signal-to-background ratio, and minimum interference from the surrounding spectra: Si(I) 288.16 nm, Mg(II) 279.55 nm, 280.27 nm, Mg(I) 285.21 nm, Ca(II) 317.93 nm, Na(I) 589.59 nm, Al(I) 308.22 nm, Fe(II) 259.94 nm, Ti(II) 334.94 nm, Sr(II) 407.77 nm, Ba(II) 455.40 nm, K(I) 769.90 nm, provided experimental data sufficiently sensitive to differentiate the properties of the studied samples. Rare earth elements were not detected even though the double pulse technique is more sensitive than the single pulse variant. Visualisation methods of multidimensional statistical analyses such as radar chart, Chernoff faces, scatterplots, and the Spearman correlation matrix provided successful differentiation of the sample groups and/or particular samples by their origin.

American Mineralogist, Volume 98, pages 319–334, 2013 0003-004X/13/0203–319$05.00/DOI: http://dx.doi.org/10.2138/am.2013.4272 319 Microbial and inorganic control on the composition of clay from volcanic glass alteration experiments Javier Cuadros,1,* Beytullah afsin,1,† Premroy JaduBansa,2 mahmoud ardakani,3 Carmen asCaso,4 and JaCek WierzChos4 1Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, U.K. 2Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, U.K. 3Department of Materials, Faculty of

American Mineralogist, Volume 86, pages 284–292, 2001 0003-004X/01/0003–284$05.00 284 INTRODUCTION Dissolution of rock-forming minerals and volcanic glass is the most important geochemical process supplying elements required for life-support systems to the Earth’s surface envi- ronments. When the solids are exposed to aqueous solutions, a leached layer having nonstoichometric composition is formed resulting from selective removal of some cations from the solid surfaces (Casey and Bunker 1990). The important reactions producing the leached layer on the solid

American Mineralogist, Volume 86, pages 284–292, 2001 0003-004X/01/0003–284$05.00 284 INTRODUCTION Dissolution of rock-forming minerals and volcanic glass is the most important geochemical process supplying elements required for life-support systems to the Earth’s surface envi- ronments. When the solids are exposed to aqueous solutions, a leached layer having nonstoichometric composition is formed resulting from selective removal of some cations from the solid surfaces (Casey and Bunker 1990). The important reactions producing the leached layer on the solid

Abstract

Fourier transform infrared (FTIR) spectroscopy can be used to determine the concentration and speciation of dissolved water in silicate glasses if the molar absorptivity coefficients (ε) are known. Samples that are thin and/or water-poor typically require the use of the mid-IR 3500 cm−1 total water (H2Ot) and 1630 cm−1 molecular water (H2Om) absorbance bands, from which hydroxyl water (OH) must be determined by difference; however, accurate determination of H2Ot and OH is complicated because ε3500 varies with water speciation, which is not usually known a priori. We derive an equation that uses end-member ε3500 values to find accurate H2Ot and OH concentrations from the 3500 cm−1 absorbance for samples where only the H2Om concentration need be known (e.g., from the 1630 cm−1 band). We validate this new species-dependent ε3500 method against published data sets and new analyses of glass standards. We use published data to calculate new end-member ε3500 values of ε3500OH = 79 ± 11 and ε3500H2Om = 49 ± 6 L/mol·cm for Fe-bearing andesite and ε3500OH = 76 ± 12 and ε3500H2Om = 62 ± 7 L/mol·cm for Fe-free andesite. These supplement existing end-member values for rhyolite and albite compositions. We demonstrate that accounting for the species-dependence of ε3500 is especially important for hydrated samples, which contain excess H2Om, and that accurate measurement of OH concentration, in conjunction with published speciation models, enables reconstruction of original pre-hydration water contents. Although previous studies of hydrous silicate glasses have suggested that values of ε decrease with decreasing tetrahedral cation fraction of the glass, this trend is not seen in the four sets of end-member ε3500 values presented here. We expect that future FTIR studies that derive end-member ε3500 values for additional compositions will therefore not only enable the species-dependent ε3500 method to be applied more widely, but will also offer additional insights into the relationship between values of ε and glass composition.

Abstract

The Pannonian Basin (Central Europe) hosts numerous alkali basaltic volcanic fields in an area similar to 200 000 km2. These volcanic fields were formed in an approximate time span of 8 million years producing smallvolume volcanoes typically considered to be monogenetic. Polycyclic monogenetic volcanic complexes are also common in each field however. The original morphology of volcanic landforms, especially phreatomagmatic volcanoes, is commonly modified. by erosion, commonly aided by tectonic uplift. The phreatomagmatic volcanoes eroded to the level of their sub-surface architecture expose crater to conduit filling as well as diatreme facies of pyroclastic rock assemblages. Uncertainties due to the strong erosion influenced by tectonic uplifts, fast and broad climatic changes, vegetation cover variations, and rapidly changing fluvio-lacustrine events in the past 8 million years in the Pannonian Basin have created a need to reconstruct and visualise the paleoenvironment into which the monogenetic volcanoes erupted. Here phreatomagmatic volcanic fields of the Miocene to Pleistocene western Hungarian alkali basaltic province have been selected and compared with modern phreatomagmatic fields. It has been concluded that the Auckland Volcanic Field (AVF) in New Zealand could be viewed as a prime modern analogue for the western Hungarian phreatomagmatic fields by sharing similarities in their pyroclastic successions textures such as pyroclast morphology, type, juvenile particle ratio to accidental lithics. Beside the AVF two other, morphologically more modified volcanic fields (Pali Aike, Argentina and Jeju, Korea) show similar features to the western Hungarian examples, highlighting issues such as preservation potential of pyroclastic successions of phreatomagmatic volcanoes.

detrital minerals of * E-mail: gpiper@smu.ca Early diagenetic origin of Al phosphate-sulfate minerals (woodhouseite and crandallite series) in terrestrial sandstones, Nova Scotia, Canada GEORGIA PE-PIPER* AND LILA M. DOLANSKY Department of Geology, Saint Maryʼs University, Halifax, Nova Scotia B3H 3C3, Canada ABSTRACT Hydrated alumino-phosphate-sulfate (APS) minerals of the woodhouseite and crandallite series are found as microcrystalline aggregates replacing volcanic glass and apatite and Þ lling pores in sand- stones of the ß uvial Lower Cretaceous Chaswood Formation

effusive eruptive products collected from Soufrière Hills volcano, Montserrat. Plagioclase feldspar crystals were removed from clasts of pyroclastic deposits. Phenocrysts were individually selected on the basis of euhedral mor- phology and a relatively homogeneous distribution of surface contamination, such as volcanic glass. Crystals were cleaned, embedded in In, and analyzed by SIMS in depth-proÞ ling mode. We used an O2+ primary ion beam, which provides a faster sputtering rate than the typically utilized O– primary beam. A normal-incidence electron gun is used

of –107 and –101‰, respectively. The HRT volcanic ash layer hosting the opals consists of hydrous glass shards, which contain 3.6 ± 0.2 wt% total water with a δD of –92 ± 5‰ ( Martin et al. 2017 ). The water in the ash is meteoritic due to secondary re-hydration of the volcanic glass after its deposit ( Taylor 1968 ; Friedman et al. 1993b ; Martin et al. 2017 ). Discussion Conditions of opal formation The consistent δ 18 O silica = 30.5 ± 0.1‰ measured in different Tecopa opals indicates that they were precipitated from the same fluid under the same temperature