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342 results on '"Gilg, H. A."'

1. A distal record of the Middle Miocene silicic eruption of the Carpathian-Pannonian Region stored within the Dinaride Lake System: implications for tephrostratigraphy and emplacement of volcaniclastic deposits

Author

Brlek, Mihovil, Trinajstić, Nina, Schindlbeck-Belo, Julie Christin, Kutterolf, Steffen, Vukovski, Matija, Guillong, Marcel, Markovic, Sava, Šuica, Sanja, Wang, Kuo-Lung, Lee, Hao-Yang, Gaynor, Sean P., Brčić, Vlatko, Mišur, Ivan, Grizelj, Anita, Kurečić, Tomislav, Lazar, Jasmina Martinčević, Milošević, Monika, Baranyi, Viktória, Kukoč, Duje, Gilg, H. Albert, Georgiev, Stoyan, and Lukács, Réka

Published
2024
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5. The geochemical character of synsedimentary volcanism in the Permian Haselgebirge Formation of the Eastern Alps (Austria): Implications for paleogeographic models.

Author

LEITNER, CHRISTOPH, HAUZENBERGER, CHRISTOPH A., GILG, H. ALBERT, FRIEDL, GERTRUDE, VON HAGKE, CHRISTOPH, and FINGER, FRIEDRICH

Abstract

We investigated the geochemistry of ca. 50 volcanic rock samples collected in various regions of the ca. 250 Ma old evaporite-bearing Austroalpine Haselgebirge Formation. The rocks are interpreted to represent synsedimentary volcanism in the Haselgebirge Formation. Open system low-T alteration processes have severely altered potassium, sodium, and calcium contents. However, based on immobile trace elements such as Zr, Y, Nb, Ti, the Haselgebirge volcanism can be classified as mainly basaltic. Different mantle sources must have been at play. Volcanism in the eastern part of the Haselgebirge Formation (Annaberg, Pfennigwiese) was MORB-like and probably related to asthenospheric mantle upwelling. As opposed to this, the volcanic samples of the western Haselgebirge Formation (Hallstatt, Lammertal) display predominantly alkali-basaltic trace element characteristics. It is hypothesized that they represent magmas from a metasomatized lithospheric mantle. Finally, a third basalt type with remarkably low Nb and Ta contents could be identified in the locality Wienern. It might be related to a (remnant?) subduction-modified mantle source. Our research highlights a gradual change of the type of magmatic activity in the Austroalpine Unit during the Permian. While according to literature data, magmatism in the early and middle Permian was dominantly felsic (granitic) and crustal, mafic mantle magmatism apparently gained increasing importance by the end of the Permian. This likely mirrors the beginning break-up of the local Pangea crust and the upwelling of asthenospheric mantle antedating the Triassic opening of the Meliata ocean. The observed source variations within the Haselgebirge volcanism point to a comparably greater degree of lithosphere thinning in the east. This accords with geological models where the (Triassic) Meliata ocean gained its greatest width in the Carpathian realm while wedging out towards the western Eastern Alps. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Compaction and Permeability Evolution of Tuffs From Krafla Volcano (Iceland).

Author

Heap, Michael J., Bayramov, Kamal, Meyer, Gabriel G., Violay, Marie E. S., Reuschlé, Thierry, Baud, Patrick, Gilg, H. Albert, Harnett, Claire E., Kushnir, Alexandra R. L., Lazari, Francesco, and Mortensen, Anette K.

Subjects
CHLORITE minerals, VOLCANIC ash, tuff, etc., PORE fluids, HYDROSTATIC pressure, FLUID flow, ZEOLITES
Abstract

Pressure and stress perturbations associated with volcanic activity and geothermal production can modify the porosity and permeability of volcanic rock, influencing hydrothermal convection, the distribution of pore fluids and pressures, and the ease of magma outgassing. However, porosity and permeability data for volcanic rock as a function of pressure and stress are rare. We focus here on three porous tuffs from Krafla volcano (Iceland). Triaxial deformation experiments showed that, despite their very similar porosities, the mechanical behavior of the three tuffs differs. Tuffs with a greater abundance of phyllosilicates and zeolites require lower stresses for inelastic behavior. Under hydrostatic conditions, porosity and permeability decrease as a function of increasing effective pressure, with larger decreases measured at pressures above that required for cataclastic pore collapse. During differential loading in the ductile regime, permeability evolution depends on initial microstructure, particularly the initial void space tortuosity. Cataclastic pore collapse can disrupt the low‐tortuosity porosity structure of high‐permeability tuffs, reducing permeability, but does not particularly influence the already tortuous porosity structure of low‐permeability tuffs, for which permeability can even increase. Increases in permeability during compaction, not observed for other porous rocks, are interpreted as a result of a decrease in void space tortuosity as microcracks surrounding collapsed pores connect adjacent pores. Our data underscore the importance of initial microstructure on permeability evolution in volcanic rock. Our data can be used to better understand and model fluid flow at geothermal reservoirs and volcanoes, important to optimize geothermal exploitation and understand and mitigate volcanic hazards. Plain Language Summary: The volcanic rocks within a volcano or geothermal reservoir are frequently subject to changes in pressure and stress. Understanding whether pressures and stresses increase or decrease permeability, and by how much, is important for understanding volcano behavior and to maximize the efficiency of a geothermal reservoir. We performed experiments in which we measured the permeability evolution of porous volcanic rocks, three tuffs, as a function of pressure and stress. We also characterized their mechanical behavior. We first show that their mechanical behavior depends on composition: the more clay minerals and chlorite present, the weaker the tuff. We then show that increasing hydrostatic pressure (i.e., depth) decreases their permeability, but that differential loading in the ductile regime can either decrease or increase permeability. Rock permeability usually decreases during deformation in the ductile regime, and so the latter result is surprising. The observed differences in permeability evolution during ductile deformation is attributed to microstructural differences between the tuffs. However, changes in permeability as a function of pressure and stress are small when compared to other rocks, suggesting that tuff may help to maintain hydrothermal circulation in volcanoes and geothermal reservoirs, with attendant consequences for volcanic hazards and geothermal energy exploitation. Key Points: Tuffs are likely weakened by the presence clay minerals, chlorite, and zeolites due to a reduction in fracture toughnessPermeability of tuff decreases during hydrostatic pressurization, particularly following the onset of inelastic hydrostatic compactionPermeability of tuff can increase during ductile deformation due to flow‐parallel microcracks that form surrounding collapsed pores [ABSTRACT FROM AUTHOR]

Published
2024
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13. Precision spectroscopy of pionic 1s states of Sn nuclei and evidence for partial restoration of chiral symmetry in the nuclear medium

Author

Suzuki, K., Fujita, M., Geissel, H., Gilg, H., Gillitzer, A., Hayano, R. S., Hirenzaki, S., Itahashi, K., Iwasaki, M., Kienle, P., Matos, M., Münzenberg, G., Ohtsubo, T., Sato, M., Shindo, M., Suzuki, T., Weick, H., Winkler, M., Yamazaki, T., and Yoneyama, T.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

Deeply bound 1s states of $\pi^-$ in $^{115,119,123}$Sn were preferentially observed using the Sn($d$,$^3$He) pion-transfer reaction under the recoil-free condition. The 1s binding energies and widths were precisely determined, and were used to deduce the isovector parameter of the s-wave pion-nucleus potential to be $b_1 =-0.115\pm 0.007 ~m_{\pi}^{-1}$. The observed enhancement of $|b_1|$ over the free $\pi N$ value ($b_1^{\rm free}/b_1 = 0.78 \pm 0.05$) indicates a reduction of the chiral order parameter, $f^{*}_{\pi} (\rho)^2/f_{\pi}^2 \approx 0.64$, at the normal nuclear density, $\rho = \rho_0$., Comment: 4 pages including 3 postscript figures, RevTeX 4 with multirow.sty, submitted to Physical Review Letters

Published
2002
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30. The tensile strength of hydrothermally altered volcanic rocks

Author

Heap, Michael J., primary, Harnett, Claire E., additional, Wadsworth, Fabian B., additional, Gilg, H. Albert, additional, Carbillet, Lucille, additional, Rosas-Carbajal, Marina, additional, Komorowski, Jean-Christophe, additional, Baud, Patrick, additional, Troll, Valentin R., additional, Deegan, Frances M., additional, Holohan, Eoghan P., additional, and Moretti, Roberto, additional

Published
2022
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31. Thermal impact of dykes on ignimbrite and implications for fluid flow compartmentalisation in calderas

Author

Kennedy, Ben M., Heap, Michael J., Burchardt, Steffi, Villeneuve, Marlène, Tuffen, Hugh, Gilg, H. Albert, Davidson, Jonathan, Duncan, Neryda, Saubin, Elodie, Gestsson, Einar Bessi, Anjomrouz, Marzieh, Butler, Philip, Kennedy, Ben M., Heap, Michael J., Burchardt, Steffi, Villeneuve, Marlène, Tuffen, Hugh, Gilg, H. Albert, Davidson, Jonathan, Duncan, Neryda, Saubin, Elodie, Gestsson, Einar Bessi, Anjomrouz, Marzieh, and Butler, Philip

Abstract

Ignimbrites within calderas host intrusions with hazardous and/or economically significant hydrothermal systems. The Hvítserkur ignimbrite at Breiðuvík caldera, north-eastern Iceland, is intruded by basaltic dykes. Our data show that the ignimbrite immediately adjacent to the dyke is hard, dark-coloured, recrystallised quartz, plagioclase, and alkali feldspar with a low permeability and porosity and frequent macrofractures. At 1-2 m from the dyke, the ignimbrite is hard, dominantly glassy with pervasive perlitic microfractures, has high permeability, but low porosity and frequent macrofractures. A narrow zone of pervasive unlithified clay exists 2 m from the dyke. Beyond this, the ignimbrite is soft and zeolite-rich, has low permeability, high porosity and fewer macrofractures. The dyke intrusion promoted a narrow zone of welding, fracturing and perlitisation in the ignimbrite resulting in high permeability and focussed alteration. Our study shows how intrusions and their thermal aureoles create vertical pathways for, and horizontal barriers to, geothermal fluid flow.

Published
2022

32. The tensile strength of hydrothermally altered volcanic rocks

Author

Heap, Michael J., Harnett, Claire E., Wadsworth, Fabian B., Gilg, H. Albert, Carbillet, Lucille, Rosas-Carbajal, Marina, Komorowski, Jean-Christophe, Baud, Patrick, Troll, Valentin R., Deegan, Frances, Holohan, Eoghan P., Moretti, Roberto, Heap, Michael J., Harnett, Claire E., Wadsworth, Fabian B., Gilg, H. Albert, Carbillet, Lucille, Rosas-Carbajal, Marina, Komorowski, Jean-Christophe, Baud, Patrick, Troll, Valentin R., Deegan, Frances, Holohan, Eoghan P., and Moretti, Roberto

Abstract

The tensile strength of volcanic rocks is an important parameter for understanding and modelling a wide range of volcanic processes, and in the development of strategies designed to optimise energy production in volcanic geothermal reservoirs. However, despite the near-ubiquity of hydrothermal alteration at volcanic and geothermal systems, values of tensile strength for hydrothermally altered volcanic rocks are sparse. Here, we present an experimental study in which we measured the tensile strength of variably altered volcanic rocks. The alteration of these rocks, quantified as the weight percentage of secondary (alteration) minerals, varied from 6 to 62.8 wt%. Our data show that tensile strength decreases as a function of porosity, in agreement with previous studies, and as a function of alteration. We fit existing theoretical constitutive models to our data so that tensile strength can be estimated for a given porosity, and we provide a transformation of these models such that they are a function of alteration. However, because porosity and alteration influence each other, it is challenging to untangle their individual contributions to the measured reduction in tensile strength. Our new data and previously published data suggest that porosity exerts a first-order role on the tensile strength of volcanic rocks. Based on our data and observations, we also suggest that (1) alteration likely decreases tensile strength if associated with mineral dissolution, weak secondary minerals (such as clays), and an increase in microstructural heterogeneity and (2) alteration likely increases tensile strength if associated with pore- and crack-filling mineral precipitation. Therefore, we conclude that both alteration intensity and alteration type likely influence tensile strength. To highlight the implications of our findings, we provide discrete element method modelling which shows that, following the pressurisation of a dyke, the damage within weak hydrothermally altered host-r

Published
2022
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36. The tensile strength of volcanic rocks

Author

Heap, Michael, primary, Aguilar Velasco, Andrea, additional, Baud, Patrick, additional, Carbillet, Lucille, additional, Deegan, Frances, additional, Gilg, H. Albert, additional, Griffiths, Luke, additional, Harnett, Claire, additional, Heng, Zhen, additional, Holohan, Eoghan, additional, Komorowski, Jean-Christophe, additional, Moretti, Roberto, additional, Reuschlé, Thierry, additional, Rosas-Carbajal, Marina, additional, Tang, Chun’an, additional, Troll, Valentin, additional, Vairé, Emma, additional, Vistour, Marie, additional, Wadsworth, Fabian, additional, and Xu, Tao, additional

Published
2022
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37. Thermal impact of dykes on ignimbrite and implications for fluid flow channelisation in a caldera

Author

Kennedy, Ben, primary, Heap, Michael, additional, Burchardt, Steffi, additional, Villeneuve, Marlène, additional, Tuffen, Hugh, additional, Gilg, H. Albert, additional, Davidson, Jonathan, additional, Duncan, Neryda, additional, Saubin, Elodie, additional, Gestsson, Einar Bessi, additional, Anjomrouz, Marzieh, additional, and Butler, Philip, additional

Published
2022
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38. Thermal impact of dykes on ignimbrite and implications for fluid flow compartmentalisation in calderas

Author

Kennedy, Ben M., primary, Heap, Michael J., additional, Burchardt, Steffi, additional, Villeneuve, Marlène, additional, Tuffen, Hugh, additional, Gilg, H. Albert, additional, Davidson, Jonathan, additional, Duncan, Neryda, additional, Saubin, Elodie, additional, Gestsson, Einar Bessi, additional, Anjomrouz, Marzieh, additional, and Butler, Philip, additional

Published
2022
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40. The thermal properties of hydrothermally altered andesites from La Soufrière de Guadeloupe (Eastern Caribbean)

Author

Heap, Michael J., primary, Jessop, David E., additional, Wadsworth, Fabian B., additional, Rosas-Carbajal, Marina, additional, Komorowski, Jean-Christophe, additional, Gilg, H. Albert, additional, Aron, Nadège, additional, Buscetti, Margaux, additional, Gential, Laura, additional, Goupil, Margaux, additional, Masson, Mathilde, additional, Hervieu, Lucie, additional, Kushnir, Alexandra R.L., additional, Baud, Patrick, additional, Carbillet, Lucille, additional, Ryan, Amy G., additional, and Moretti, Roberto, additional

Published
2022
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45. The high-acceptance dielectron spectrometer HADES

Author

Agakichiev, G., Agodi, C., Alvarez-Pol, H., Atkin, E., Badura, E., Balanda, A., Bassi, A., Bassini, R., Bellia, G., Belver, D., Belyaev, A. V., Benovic, M., Bertini, D., Bielcik, J., Böhmer, M., Boiano, C., Bokemeyer, H., Bartolotti, A., Boyard, J. L., Brambilla, S., Braun-Munzinger, P., Cabanelas, P., Castro, E., Chepurnov, V., Chernenko, S., Christ, T., Coniglione, R., Cosentino, L., Dahlinger, M., Daues, H. W., Destefanis, M., Díaz, J., Dohrmann, F., Dressler, R., Durán, I., Dybczak, A., Eberl, T., Enghardt, W., Fabbietti, L., Fateev, O. V., Fernández, C., Finocchiaro, P., Friese, J., Fröhlich, I., Fuentes, B., Galatyuk, T., Garabatos, C., Garzón, J. A., Genolini, B., Gernhäuser, R., Gilardi, C., Gilg, H., Golubeva, M., González-Díaz, D., Grosse, E., Guber, F., Hehner, J., Heidel, K., Heinz, T., Hennino, T., Hlavac, S., Hoffmann, J., Holzmann, R., Homolka, J., Hutsch, J., Ierusalimov, A. P., Iori, I., Ivashkin, A., Jaskula, M., Jourdain, J. C., Jurkovic, M., Kämpfer, B., Kajetanowicz, M., Kanaki, K., Karavicheva, T., Kastenmüller, A., Kidon, L., Kienle, P., Kirschner, D., Koenig, I., Koenig, W., Körner, H. J., Kolb, B. W., Kopf, U., Korcyl, K., Kotte, R., Kozuch, A., Krizek, F., Krücken, R., Kühn, W., Kugler, A., Kulessa, R., Kurepin, A., Kurtukian-Nieto, T., Lang, S., Lange, J. S., Lapidus, K., Lehnert, J., Leinberger, U., Lichtblau, C., Lins, E., Lippmann, C., Lorenz, M., Magestro, D., Maier, L., Maier-Komor, P., Maiolino, C., Malarz, A., Marek, T., Markert, J., Metag, V., Michalska, B., Michel, J., Migneco, E., Mishra, D., Morinière, E., Mousa, J., Münch, M., Müntz, C., Naumann, L., Nekhaev, A., Niebur, W., Novotny, J., Novotny, R., Ott, W., Otwinowski, J., Pachmayer, Y. C., Palka, M., Parpottas, Y., Pechenov, V., Pechenova, O., Pérez Cavalcanti, T., Petri, M., Piattelli, P., Pietraszko, J., Pleskac, R., Ploskon, M., Pospísil, V., Pouthas, J., Prokopowicz, W., Przygoda, W., Ramstein, B., Reshetin, A., Ritman, J., Roche, G., Rodriguez-Prieto, G., Rosenkranz, K., Rosier, P., Roy-Stephan, M., Rustamov, A., Sabin-Fernandez, J., Sadovsky, A., Sailer, B., Salabura, P., Salz, C., Sánchez, M., Sapienza, P., Schäfer, D., Schicker, R. M., Schmah, A., Schön, H., Schön, W., Schroeder, C., Schroeder, S., Schwab, E., Senger, P., Shileev, K., Simon, R. S., Skoda, M., Smolyankin, V., Smykov, L., Sobiella, M., Sobolev, Yu. G., Spataro, S., Spruck, B., Stelzer, H., Ströbele, H., Stroth, J., Sturm, C., Sudoł, M., Suk, M., Szczybura, M., Taranenko, A., Tarantola, A., Teilab, K., Tiflov, V., Tikhonov, A., Tlusty, P., Toia, A., Traxler, M., Trebacz, R., Troyan, A. Yu., Tsertos, H., Turzo, I., Ulrich, A., Vassiliev, D., Vázquez, A., Volkov, Y., Wagner, V., Wallner, C., Walus, W., Wang, Y., Weber, M., Wieser, J., Winkler, S., Wisniowski, M., Wojcik, T., Wüstenfeld, J., Yurevich, S., Zanevsky, Y. V., Zeitelhack, K., Zentek, A., Zhou, P., Zovinec, D., Zumbruch, P., and The HADES Collaboration

Published
2009
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48. Alexandra Hilgner, Susanne Greiff und Dieter Quast (Herausgeber), Gemstones in the First Millenium AD. Mines, Trade, Workshops and Symbolism

Author

Gilg, H. Albert

Abstract

Rezension zu: Alexandra Hilgner, Susanne Greiff und Dieter Quast (Herausgeber), Gemstones in the First Millenium AD. Mines, Trade, Workshops and Symbolism. Römisch-Germanisches Zentralmuseum. RGZM-Tagungen, Band 30. Verlag des Römisch-Germanischen Zentralmuseums, Mainz 2017. VII und 324 Seiten mit 206 meist farbigen Abbildungen., Bonner Jahrbücher, Bd. 217.2017(2018): Bonner Jahrbücher

Published
2021
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49. Alteration‐Induced Volcano Instability at La Soufrière de Guadeloupe (Eastern Caribbean)

Author

Heap, Michael J., primary, Baumann, Tobias S., additional, Rosas‐Carbajal, Marina, additional, Komorowski, Jean‐Christophe, additional, Gilg, H. Albert, additional, Villeneuve, Marlène, additional, Moretti, Roberto, additional, Baud, Patrick, additional, Carbillet, Lucille, additional, Harnett, Claire, additional, and Reuschlé, Thierry, additional

Published
2021
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