Wolf-Achim Kahl
Dr. Wolf-Achim Kahl
MAPEX - Center for Materials and Processes
GEO Room 5070
Klagenfurter Straße 2-4
28359 Bremen, Germany
Phone: +49 421 218 65408
Email
Visit the 3D Materials Analytics section
Quantitative digital 3D image analysis of µ-CT-based volume data
In the last decade, I have focused my attention on microstructural changes of reactive water-rock systems and the associated feedbacks between reaction progress and pore space. I combine quantitative 3D digital image analysis with other spectrographic methods (µ-CT, FIB-SEM, EBSD, EPMA, ICP-MS), and also incorporate observations in natural rocks and experimental simulations.
My scientific work began with research on the influence of bulk compositions on phase relationships in metamorphosed chemical sediments from submarine hydrothermal activity. Later, I established two calorimetry laboratories and determined thermodynamic properties of selected silicate minerals. So far, I have established two µ-CT labs (SkyScan 1172, CAU Kiel; ProCon CT-ALPHA, FB5 University of Bremen) and participated in numerous scientific collaborations (e.g. on Neolithic pottery, fossilized whale bones or aggregates in concrete).
Below are a few examples from my research to unfold....
ABSTRACT. In basaltic volcanic ash recovered from a seamount at 3000 m water depth, we discovered marcasite and pyrite precipitation within cavities that formed by partial to complete dissolution of olivine. In places, these cavities are reminiscent of negative crystal shapes; elsewhere they apparently continue along cracks. In strong contrast, adjacent volcanic glass shows little, if any, evidence for dissolution. The FeS2 precipitates were commonly found to be conjoined and planar aggregates, occurring in the center of the voids. Their maximum volume fraction in relation to the void space as determined by 2D and 3D imaging techniques corresponds to the amount of iron released by olivine dissolution. Almost all occurrences of FeS2 precipitation are related to Cr-spinel inclusions in the former olivine. We propose that rapid olivine dissolution was initiated by reduced H2S-bearing fluids at olivine grain boundaries or surfaces exposed by cracks. Many of these cracks are connected to spinel grains, where the iron liberated from olivine is mineralized as FeS2, initially facilitated by heterogeneous nucleation. Subsequent pyrite and/or marcasite precipitation occurred as overgrowths on existing FeS2 aggregates. The particular chemical environment of low-pH, hydrogen sulfide-bearing fluids may have enhanced olivine dissolution by (1) keeping Fe in solution and (2) sequestering important quantities of Fe as FeS2. The in situ oxidation of ferrous Fe and precipitation of ferric hydroxides at the olivine surface commonly observed in oxic environments were obviously impeded. It would have slowed down olivine dissolution to rates more similar to the dissolution of basaltic glass. We have no direct indication that the process of rapid olivine dissolution was aided by subseafloor life. However, the presence of fibrous structures with small sulfide particles could indicate late colonization of sulfate-reducing bacteria that may add an additional path of iron fixation.
ABSTRACT. Dissolution rates of porous crystalline materials reflect the superposition of transport and surface control, mainly via the parameters saturation of the ambient fluid and distribution of surface energy. As a result, reacting surfaces evolve over time showing a heterogeneous distribution of surface rates. The spatiotemporal heterogeneity of surface reaction rates is analyzed using the rate map and rate spectra concept. Here, we quantify the dissolution rate variability covering the nm- to mm-scale of dissolving single-crystal and polycrystalline calcite samples, using a combined approach of X-ray micro-computed tomography (µ-CT) and vertical scanning interferometry (VSI). The dissolution experiments cover reaction periods from 15 minutes up to 54 days. The observed rate ranges are remarkably consistent over the entire reaction period but include a variability of about two orders of magnitude (10-9 - 3*10-7 mol m-2 s-1). The rate map data underscore the concurrent and superimposing impact of surface- vs. fluid flow controlled rate portions. The impact of fluid flow on reactivity at the mm-scale in the transport-controlled system is confirmed by 2-D reactive transport modeling. The sub-mm spatial heterogeneity of low vs. high reactivity surface portions of polycrystalline calcite is clearly below the mean crystal size. This suggests the dominant impact of highly reactive surface portions irrespective of the orientation of larger crystals on the overall surface reactivity. Correspondingly, the overall range of intrinsic reactivity heterogeneity as observed using singly crystal material is not further expanded for polycrystalline material. As a general conclusion, numerical reactive transport concepts would benefit from the implementation of a reactivity term resembling the experimentally observed existence of multiple rate components.
ABSTRACT. We reconstruct the 3-D microstructure of centimetre-sized olivine crystals in rocks from the Almirez ultramafic massif (SE Spain) using combined X-ray micro computed tomogra- phy (μ-CT) and electron backscatter diffraction (EBSD). The semidestructive sample treatment involves geographically oriented drill pressing of rocks and preparation of oriented thin sections for EBSD from the μ-CT scanned cores. The μ-CT results show that the mean intercept length (MIL) analyses provide reliable information on the shape preferred orientation (SPO) of texturally different olivine groups. We show that statistical interpretation of crystal preferred orientation (CPO) and SPO of olivine becomes feasible because the highest densities of the distribution of main olivine crystal axes from EBSD are aligned with the three axes of the 3-D ellipsoid calculated from the MIL analyses from μ-CT. From EBSD data we distinguish multiple CPO groups and by locating the thin sections within the μ-CT volume, we assign SPO to the corresponding olivine crystal aggregates, which confirm the results of statistical comparison. We demonstrate that the limitations of both methods (i.e. no crystal orientation data in μ-CT and no spatial information in EBSD) can be overcome, and the 3-D orientation of the crystallographic axes of olivines from different orientation groups can be successfully correlated with the crystal shapes of representative olivine grains. Through this approach one can establish the link among geological structures, macrostructure, fabric and 3-D SPO-CPO relationship at the hand specimen scale even in complex, coarse-grained geomaterials.
ABSTRACT. A new flow-through reaction cell consisting of an X-ray-transparent semicrystalline thermoplastic has been developed for percolation experiments. Core holder, tubing and all confining parts are constructed using PEEK (polyetheretherketone) to allow concomitant surveillance of the reaction progress by X-ray microtomography (μ-CT). With this cell setup, corrosive or oversaturated fluids can be forced through rock cores (up to Ø 19 mm) or powders at pressures up to 100 bar and temperatures up to 200 °C. The reaction progress of the experiment can be monitored without dismantling the sample from the core holder.
The combination of this flow-through reaction cell setup with a laboratory X-ray μ-CT system facilitates on-demand monitoring of the reaction progress of (long-term) hydrothermal experiments in the own laboratory, keeping interruption times as short as possible. To demonstrate both the suitability of the cell construction material for X-ray imaging purposes and the experimental performance of the flow-through system, we report the virtually non-existent bias of the PEEK cell setup with distinctive X-ray observations (e.g., differing states of pore fillings: air vs. fluid; detection of delicate fabric elements: filigree zeolite crystals overgrowing weathered muscovite), and the monitoring of the gypsum/anhydrite transition as a case study of a 4-D fabric evolution.
Curriculum vitae
Scientific career
| since April 2020 | Lab Manager 3D X-ray microscope, MAPEX Center for Materials and Processes, University of Bremen, Germany |
| 2012 -2020 | Research fellow, Reinhart Koselleck Project with Prof. Dr.W. Bach, University of Bremen, Germany
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| 2007-2011 | Research fellow in the joint research project CO2-MoPa „Modelling und Parametrization of CO2-Sequestration“ with Prof. Dr. A. Holzheid, Christian-Albrechts-University, Kiel, Germany
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| 2004-2007 | Research fellow in R&D Project „Automotive catalysts“ mit Dr. U. Klein, Umicore AG & Co. KG, Hanau, Germany, and with Prof. Dr. V. Schenk, Christian-Albrechts-University, Kiel, Germany
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| Juli 2000 | Dr. rer. nat. in Mineralogy, Ruhr University Bochum, Germany |
| 1996-2000 | Research assistant and PhD student, Ruhr University Bochum, Germany
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| Jan. 1996 | Diploma in Mineralogy, Christian-Albrechts University, Kiel, Germany |
| 1988-1996 | Studies of Mineralogy, Christian-Albrechts University, Kiel, Deutschland Supervisor of Diploma thesis: Dr. John Schumacher |
Further activities
| 2022 | Appointment as radiation protection officer for MAPEX und FB5, University of Bremen, Germany |
| seit 2011 | Webmaster of the "International Confederation for Thermal Analysis and Calorimetry" (ICTAC, www.ictac.org) |
| 2010 | Appointment as radiation protection officer at the Institute for Geosciences, Christian-Albrechts University, Kiel, Deutschland |
| seit 2004 | Webmaster of the Society for Thermal Analysis e. V. (GEFTA, www.gefta.org) and guest in the board |
Additional qualifications
- Acquisition of expertise in radiation protection (Groups R2, R3, R4, R10) according to RöV (Fachkunde-Richtlinie Technik) at the Norddeutschen Seminar für Strahlenschutz, Kiel
- IT-skills: Webdesign (HTML, PHP, mysql), Application development (Java, VB), Databases
Publications
Schmid-Beurmann, H. A., Kahl, W.-A., Bach, W., Ivarsson, M., Böttcher, M. E., Peckmann, J. (2023) Dispersal of endolithic microorganisms in vesicular volcanic rock: Distribution, settlement and pathways revealed by 3D X-ray microscopy. Terra Nova, 35(5), 396-403.
| doi: 10.1111/ter.12663 |
Sommer, M., Kahl, W.-A., Fechte-Heinen, R. and Hoja, S. (2023) Microscopic Characterization of Compound Layers. Practical Metallography, Vol. 60, No. 4, 2023, 212-241.
| doi: 10.1515/pm-2022-1028 |
Kahl, W.-A., Klügel, A., Bach, W., Murshed, M. M. (2022) Enhanced weathering in the seabed: rapid olivine dissolution and iron sulfide formation in submarine volcanic ash. American Mineralogist, 107(9), 1668-1680.
| doi: 10.2138/am-2022-8057 |
Hansen, C. T., Lissenberg, C. J., Kahl, W.-A., Bach, W. (2022) Hydrothermal troctolite alteration at 300 and 400°C – Insights from flexible Au-reaction cell batch experimental investigations. American Mineralogist, 107(6), 1100-1115.
| doi: 10.2138/am-2021-7832 |
Dilissen, N., Hidas, K., Garrido, C. J., Sánchez-Vizcaíno V. L., Kahl, W.-A. (2021) Morphological transition during prograde olivine growth formed by high-pressure dehydration of antigorite-serpentinite to chlorite-harzburgite in a subduction setting. Lithos, 382-383, 105949.
| doi: 10.1016/j.lithos.2020.105949 |
Albers, E., Kahl, W.-A., Beyer, L., Bach, W. (2020) Variant across-forearc compositions of slab-fluids recorded by serpentinites: Implications on the mobilization of FMEs from an active subduction zone (Mariana forearc). Lithos, 364-365, 105525.
| doi: 10.1016/j.lithos.2020.105525 |
Kahl, W.-A., Yuan, T., Bollermann, T., Bach, W., Fischer, C. (2020) Crystal surface reactivity analysis using a combined approach of X-ray micro-computed tomography and vertical scanning interferometry. American Journal of Science, 320(1), 27-52.
| doi: 10.2475/01.2020.03 |
Türke, A., Jackson, M.S., Bach, W., Kahl, W.-A., Grzybowski, B., Marshall, B., Gudmundsson, M.T., Jørgensen, S.L. (2019) Design of the subsurface observatory at Surtsey volcano, Iceland. Sci. Dril., 25, 57-62.
| doi: 10.5194/sd-25-57-2019 |
Dilissen, N., Hidas, K., Garrido, C. J., Kahl, W.-A., Sánchez-Vizcaíno, V. C., Padrón-Navarta, J. A. (2018) Textural evolution during high-pressure dehydration of serpentinite to peridotite and its relation to stress orientations and kinematics of subducting slabs: Insights from the Almirez ultramafic massif. Lithos, 320-321, 470-489.
| doi: 10.1016/j.lithos.2018.09.033 |
Titschack, J., Baum, D., Matsuyama, K., Boos, K., Färber, C., Kahl, W.-A., Ehrig, K., Meinel, D., Soriano, C., Stock, S.R. (2018) Ambient occlusion – A powerful algorithm to segment shell and skeletal intrapores in computed tomography data, Computers and Geosciences, 115, 75-87.
| doi: 10.1016/j.cageo.2018.03.007 |
Kahl, W.-A., Dilissen, N., Hidas, K., Garrido, C. J., López-Sánchez-Vizcaíno, V. and Román-Alpiste, M. J. (2017): 3-D microstructure of olivine in complex geological materials reconstructed by correlative X-ray µ-CT and EBSD analyses. Journal of Microscopy 268, 193-207.
| doi:10.1111/jmi.12598 |
Wisshak, M., Titschack, J., Kahl, W.-A., and Girod, P. (2017) Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT. Foss. Rec., 20, 173-199.
| doi:10.5194/fr-20-173-2017 |
Jöns, N., Kahl, W.-A., and Bach, W. (2017) Reaction-induced porosity and onset of low-temperature carbonation in abyssal peridotites: insights from 3D high-resolution microtomography. Lithos, 268-271, 274-284.
| doi:10.1016/j.lithos.2016.11.014 |
Kahl, W.-A., Hansen, C., and Bach, W. (2016) A new X-ray-transparent flow-through reaction cell for a μ-CT-based concomitant surveillance of the reaction progress of hydrothermal mineral–fluid interactions. Solid Earth, 7, 651-658.
| doi:10.5194/se-7-651-2016 |
Soltan, A.M.M., Kahl, W.-A., Abd EL-Raoof, F., Abdel-Hamid El-Kaliouby, B., Abdel- Kader Serry, M., Abdel-Kader, N.A. (2016) Lightweight aggregates from mixtures of granite wastes with clay. Journal of Cleaner Production, 117, 139-149.
| doi: 10.1016/j.jclepro.2016.01.017 |
Kahl, W.-A., Jöns, N., Bach, W., Klein, F., Alt, J.C. (2015) Ultramafic clasts from the South Chamorro serpentine mud volcano reveal a polyphase serpentinization history of the Mariana forearc mantle. Lithos, 227, 1-20.
| doi:10.1016/j.lithos.2015.03.015 |
Klein, F., Grozeva, N.G., Seewald, J.S., McCollom, T., Humphris, S.E., Moskowitz, B., Berquó, T.S. & Kahl, W.-A. (2015) Experimental constraints on fluid-rock reactions during incipient serpentinization of harzburgite. American Mineralogist, 100, 991-1002.
| doi: 10.2138/am-2015-5112 |
Klein, F., Bach, W., Humphris, S.E., Kahl, W.-A., Jöns, N., Moskowitz, B. & Berquó, T.S. (2014) Magnetite in seafloor serpentinite−−Some like it hot. Geology, 42(2), 135-138.
| doi: 10.1130/G35068.1 |
Kahl, W.-A., Hinkes, R., Feeser, V. & Holzheid, A. (2013) Microfabric and anisotropy of elastic waves in sandstone - An observation using high-resolution X-ray microtomography. Journal of Structural Geology, 49, 35-49.
| doi: 10.1016/j.jsg.2013.01.006 |
Kiel, S., Kahl, W.-A. & Goedert, J. L. (2013) Traces of the bone-eating annelid Osedax in Oligocene whale teeth and fish bones. Paläontologische Zeitschrift, 87, 161-167.
| doi:10.1007/s12542-012-0158-9 |
Kahl, W.-A. & Ramminger, B. (2012) Non-destructive fabric analysis of prehistoric pottery using high-resolution X-ray microtomography: a pilot study on the late Mesolithic to Neolithic site Hamburg-Boberg. Journal of Archaeological Science, 39, 2206-2219.
| doi:10.1016/j.jas.2012.02.029 |
Majzlan, J., Drahota, P., Filippi, M., Grevel, K.-D., Kahl, W.-A., Plášil, J., Boerio-Goates, J. & Woodfield, B. F. (2012) Thermodynamic properties of scorodite and parascorodite (FeAsO4·2H2O), kaňkite (FeAsO4·3.5H2O), and FeAsO4. Hydrometallurgy, 117-118, 47-56.
| doi:10.1016/j.hydromet.2012.02.002 |
Soltan, A. M. M., Kahl, W.-A., Wendschuh, M. & Hazem, M. M. (2012) Microstructure and reactivity of calcined mud supported limestones. Mineral Processing and Extractive Metallurgy (Trans. Inst. Min Metall. C), Vol. 121, 5-11.
| doi: 10.1179/1743285511Y.0000000024 |
Soltan, A. M. M., Kahl, W.-A., Hazem, M. M., Wendschuh, M. & Fischer, R. X. (2011) Thermal microstructural changes of grain-supported limestones. Mineralogy and Petrology, Vol. 103, 9-17.
| doi: 10.1007/s00710-011-0151-0 |
Kiel, S., Kahl, W.-A. & Goedert, J. L. (2011) Osedax borings in fossil marine bird bones. Naturwissenschaften, Vol. 98, Number 1, 51-55.
| doi: 10.1007/s00114-010-0740-5 |
Kiel, S., Goedert, J. L., Kahl, W.-A. & Rouse, G. W. (2010) Fossil traces of the bone-eating worm Osedax in early Oligocene whale bones. PNAS, Vol. 107, No. 19, 8656-8659.
| doi: 10.1073/pnas.1002014107 |
Grevel, K.-D., Kahl, W.-A., Majzlan, J., Navrotsky, A., Lathe, C. & Fockenberg, T. (2005) Thermodynamic properties of magnesiochloritoid. Eur. J. Mineral., 17, 587-598.
| doi: 10.1127/0935-1221/2005/0017-0587 |
Kahl , W.-A., Maresch, W. V. & Welch, M. D. (2003) Enthalpy of formation of pargasite by high temperature solution calorimetry and heat capacity of pargasite and fluoropargasite by differential scanning calorimetry. Eur. J. Mineral., 15, 617-628.
| doi: 10.1127/0935-1221/2003/0015-0617 |
Kahl , W.-A. & Maresch, W. V. (2001) Enthalpies of formation of tremolite and talc by high temperature solution calorimetry – a consistent picture. Amer. Mineral., 86, 1345-1357.
| link to Vol. 86, No. 11-12 |
Grevel, K.-D., Navrotsky, A., Kahl, W.-A., Faßhauer, D. W. & Majzlan, J. (2001) Thermodynamic data of the high-pressure phase Mg5Al5Si6O21(OH)7 (Mg-sursassite). Phys. Chem. Minerals, 28, 475-487.
| doi: 10.1007/s002690100175 |
Kahl, W.-A. & Schumacher, J.C. (2000) Multiple pyroxene and amphibole assemblages in the amphibolite facies: bulk compositional controls. Amer. Mineral., 85, 1606-1616.
| link to Vol. 85, No. 11-12 |
Kahl, W.-A., Türke, A., and Bach, W. (2021) X-ray µ-CT data reconstruction, image stack of ICPD Core ICDP5059_1_C. PANGAEA.
| https://doi.org/10.1594/PANGAEA.935039 |
Kahl, W.-A., Türke, A., and Bach, W. (2021) X-ray µ-CT data reconstruction, image stack of ICPD Core ICDP5059_1_D. PANGAEA.
| https://doi.org/10.1594/PANGAEA.932142 |
Albers, E., Kahl, W.-A., Beyer, L., and Bach, W. (2020) Mineral geochemical data of serpentinites from the Mariana serpentinite mud volcanoes (IODP Exp. 366). PANGAEA Documentation, Bremerhaven, PANGAEA.
| https://doi.pangaea.de/10.1594/PANGAEA.921494 |
Magnucki, G., Kahl, W.-A. (2018) Four rooted maxillary first molar with five root canals and two enamel pearls. The International Journal of Dental and Health Sciences, vol. 5, no. 4, pp. 600–605.
Wisshak, M. , Titschack, J. , Kahl, W.-A. and Girod, P. (2017) Classical and new bioerosion trace fossils in Cretaceous belemnite guards characterised via micro-CT, supplementary material. PANGAEA Documentation, Bremerhaven, PANGAEA.
| doi: 10.1594/PANGAEA.875121 |
Kahl, W.-A., Ramminger, B. (2012) Zerstörungsfreie Analysen prähistorischer Keramik mittels hoch auflösender Mikro-Computertomographie am Beispiel spätmesolithischer und neolithischer Funde aus Hamburg-Boberg. In: B. Ramminger/O. Stilborg (Hrsg.), Naturwissenschaftliche Analysen vor- und frühgeschichtlicher Keramik II: Methoden, Anwendungsbereiche, Auswertungsmöglichkeiten. Universitätsforschungen zur prähistorischen Archäologie 216, 2012, 59-95.
Kelemen, P., de Obeso, J., Manning, C., Godard, M., Bach, W., Cai, M., Choe, S., Coggon, J., Ellison, E., Eslami, A., Evans, K., Harris, M., Kahl, W.-A., Matter, J., Michibayashi, K., Okazaki, K., Pezard, P., Teagle, D., Templeton, A., and OmanDP Science Team (2019) Peridotite alteration in OmanDP cores. European Geosciences Union General Assembly 2019, Vienna, Austria, Geophysical Research Abstracts 21, EGU2019-4436-2.
Türke, A., Jackson, M.D., Bach, W., Kahl, W.-A., Jørgensen, S.L., and Gudmundsson, M.T. (2019) Design and implementation of a submarine borehole observatory at Surtsey Volcano, Iceland. European Geosciences Union General Assembly 2019, Vienna, Austria, Geophysical Research Abstracts 21, EGU2019-18812-1.
Benjamin M Tutolo, B.M., Eslami, A., Evans, K.A., Kahl, W.-A., Godard, M., Kelemen, P.B., Michibayashi, M., Takazawa, E., Teagle, D.A.H. (2018) A Reconnaissance Petrographic Study of Opaque Mineral Assemblages in Peridotites and Mafic Dykes from the Oman Drilling Project Holes BA1B, BA3A and BA4A. AGU Fall Meeting 2018, V13E-0137.
Kelemen, P.B., Bach, W., Evans, K.A., Eslami, A., Farough, A., Hamada, M., Ichiyama, Y., Kahl, W.-A., Matter, J.M., Pezard, P.A., Paukert Vankeuren, A.N., Godard, M., Michibayashi, K., Choe, S., and Coggon, J.A. (2019) Correlated variation in vein type, vein frequency, pH, oxygen fugacity and depth in Oman Drilling Project Holes BA1B, BA3A and BA4A. AGU Fall Meeting 2018, V12B-03.
Kahl, W.-A., Bach, W, Littmann S. (2018) Fluid path-dependent, hydrodynamic micro-environments govern serpentinization textures of harzburgite hydration in a flow-through reaction cell. European Geosciences Union General Assembly 2018, 9-13 April, 2018, Vienna, Austria, Geophysical Research Abstracts 20, EGU2018-13566.
Lisker, F., Emmel, B., Hewawasam, T., Kahl, W.-A., Schlegel, A. (2018) Sri Lanka: the inverted hinge of Gondwana. European Geosciences Union General Assembly 2018, 9-13 April, 2018, Vienna, Austria, Geophysical Research Abstracts 20, EGU2018-13360.
Dilissen, N., Hidas, K., Garrido, C.J., López Sánchez-Vizcaíno, V., Kahl, W.-A., Román-Alpiste, M.J. (2018) Fluid infiltration-driven morphological transition during prograde olivine growth formed by high-pressure Atg-serpentinite dehydration. European Geosciences Union General Assembly 2018, 9-13 April, 2018, Vienna, Austria, Geophysical Research Abstracts 20, EGU2018-4598.
Los, C.L., Kahl, W.-A., Bach, W. (2017) Length scales of reactive transport in basalt: Hydrothermal flow-through experiments and anhydrite precipitation. AGU Fall Meeting 2017, New Orleans, USA.
Kahl, W.-A., Bach, W., Jöns, N. (2017) Oxidative alteration of partially serpentinized harzburgite in a flow-through reaction cell: reaction of olivine to Fe-oxyhydroxide phases and serpentine at 120 °C. GeoBremen2017, A-849.
Jöns, N., Kahl, W.-A., Bach, W. (2017) Reaction-induced porosity and low-temperature carbonation of abyssal peridotites from the Mid-Atlantic Ridge. GeoBremen2017, A-751.
Beyer, L., Albers, E., Kahl, W.-A., Bach, W. & Exp. 366 Scientists (2017) Polyphase alteration of ultramafic clasts from a serpentinite mud volcano (Mariana forearc) unveil shallow subduction zone processes. GeoBremen2017, A-746.
Kahl, W.-A., Türke, A., Bach, W. (2017) Assessing microbial, mineralogical, and hydrothermal processes in the ICDP borehole on Surtsey: a combined observatory and experimental approach. GeoBremen2017, A-723.
Los, C., Kahl W.-A., Bach, W. (2017) Reactive transport in basalt: sulfate precipitation in flow-through experiments. GeoBremen2017, A-611.
Fischer, C., Kurganskaya, I., Kahl, W.-A., Bollermann, T., Prüsse, F., Bach, W., Luttge, A. (2017) Upscaling of Dissolution Rate Contributors from the Atomic Scale to the Macroscopic Scale. Goldschmidt Abstracts, 2017.
Bach, W., Kahl, W.-A., Türke, A. (2017): Rates and processes of tephra alteration in Surtsey volcano: a combined observational and experimental approach. IODP/ICDP Kolloquium, Braunschweig, Deutschland.
Kahl, W.-A., Hidas, K., Dilissen, N., Garrido, C.J., Lopez-Sanchez Vizcaino, V., Roman-Alpiste, M.J. (2017) Reconstruction of the 3-D Shape and Crystal Preferred Orientation of Olivine: A Combined X–ray –CT and EBSD-SEM approach. European Geosciences Union General Assembly 2017, 23-28 April, 2017, Vienna, Austria, Geophysical Research Abstracts 17, EGU2017-8061.
Dilissen, N., Hidas, K., Garrido, C.J., Lopez-Sanchez Vizcaino, V., Kahl, W.-A., Padron-Navarta, J.A., Roman-Alpiste, M.J. (2017) Relationship Between Far Field Stresses, Fluid Flow and High-Pressure Deserpentinization in Subducting Slabs: a Case Study From the Almirez Ultramafic Massif. European Geosciences Union General Assembly 2017, 23-28 April, 2017, Vienna, Austria, Geophysical Research Abstracts 17, EGU2017-16454.
Dilissen, N., Hidas, K., Garrido, C.J., Lopez-Sanchez Vizcaino, V., Kahl, W.-A., Padron-Navarta, J.A., Roman-Alpiste, M.J. (2017) Couplings between far field stresses, fluid flow and high-pressure deserpentinization in subducting slabs: insight from the Almirez ultramafic massif. SIP International Conference Barcelona, 39, 45-46.
Los, C.L., Kahl, W.-A., Plümper, O., Bach, W. (2016): Formation of replacive sulphide in anhydrite chimneys. Jährliches DMG Sektionstreffen 2016 Geochemie-Petrologie-Petrophysik, Bremen.
Dilissen, N., Kahl, W.-A., Garrido, C.J., Sanchez-Vizcaino, V.L., Hidas, K. (2016) Deciphering the dynamics of olivine nucleation and growth during antigorite breakdown. European Geosciences Union General Assembly 2016, 17-22 April, 2016, Vienna, Austria, Geophysical Research Abstracts 16, EGU2016-5743.
Klein, F., Bach, W., Humphris, S.E., Kahl, W.-A., Jöns, N., Moskowitz, B., Berquó, T.S. (2014) Low-Temperature Serpentinization Produces Abundant Hydrogen within the Temperature Limits of Life. Goldschmidt Abstracts, 2014, 1276.
Türke. A., Bach, W., Kahl, W.-A., Klügel, A. (2014): Palagonitization of basalt glass in the flanks of mid-ocean ridges: impications for bioenergetics of oceanic intracrustal ecosystems. 4th Nordic Astrobiology Conference, Bergen, Norwegen.
Türke, A., Bach, W., Kahl, W.-A., Klügel, A. (2013): Palagonitization of basalt glass in the flanks of mid-ocean ridges: impications for bioenergetics of oceanic intracrustal ecosystem. DMG/GV Meeting, Tübingen, Deutschland.
Bach, W., Kahl, W.-A., Jöns, N., Türke, A., Plümper, O. (2013) Rocky Constraints on Catabolic Energy Supply in the Subseafloor. Mineralogical Magazine, 77(5) 638.
Kahl, W.-A., Jöns, N., Bach, W., Klein, F. (2013) Polyphase serpentinization history of Mariana forearc mantle: observations on the microfabric of ultramafic clasts from ODP Leg 195, Site 1200. Geophysical Research Abstracts 15, EGU2013-13864.
Klein, F., Bach, W., Kahl, W.-A., Humphris, S. (2013) Redox Controls and Reaction Pathways during Serpentinization of Abyssal Peridotite. Geophysical Research Abstracts 15, EGU2013-8752.
Kahl, W.-A., Holzheid, A. (2013) High-resolution 3D X-ray microtomography as tool to investigate size distribution of grain phase and pore space in sandstones. Geophysical Research Abstracts 15, EGU2013-7640.
Jöns, N., Kahl, W.-A., Bach, W. (2013) Reaction-induced porosity and onset of carbonation in abyssal peridotites: insights from 3D high-resolution microtomography. Geophysical Research Abstracts 15, EGU2013-5412.
Kahl, W.-A., Ramminger, B., Helfert, M. (2012) X-ray microtomography: a non-destructive tool to visualise different links in the production chain of ancient pottery. European Mineralogical Conference, Vol. 1, EMC2012-280, 2012.
Kahl, W.-A., Jöns, N. (2012) X-ray microtomography as a visualization tool for fluid-rock interaction in the oceanic crust: insights into serpentinisation and low-temperature seawater alteration. SkyScan Usermeeting 2012, 03.-05.04.2012, Brussels, Belgium. Micro-CT User Meeting Abstract Book ISBN 9789081678100, p. 21-26.
Kahl, W., Helfert, M., Ramminger, B. (2012) Potsherds of late Mesolithic/Neolithic age shed light on prehistoric ceramicist's workshop. SkyScan Usermeeting 2012, 03.-05.04.2012, Brussels, Belgium. Micro-CT User Meeting Abstract Book ISBN 9789081678100, p. 218-223.
Kahl, W.-A., Jöns, N., Bach, W., Klein, F. (2012) Polyphase serpentinization history of Mariana forearc mantle: observations on ultramafic clasts from ODP Leg 195, Site 1200. IODP-ICDP Kolloquium Kiel, p.84.
Grevel, K.-D., Majzlan, J., Kahl, W.-A., Woodfield, B.F., Boerio-Goates, J. (2012) Thermodynamics of scorodite, FeAsO4*2 H2O. EMPG 2012 – Abstract volume, p. 70.
Kahl, W.-A., Jöns, N., Bach, W., Klein, F. (2011) Polyphase serpentinization history of Mariana forearc mantle: observations on ultramafic clasts from ODP Leg 195, Site 1200. Mineralogical Magazine 75, p.1134.
Kahl, W.-A., Feeser, V., Hinkes, R., Holzheid, A. (2011) Anisotropy of elastic waves in sandstone: correlation with microstructural observations. SkyScan Usermeeting 2011, 13.-15.04.2011, Leuven, Belgium. Micro-CT User Meeting Abstract Book ISBN 9789081678100, p. 196.
Kahl, W., Ramminger, B. (2011) Potsherds of late Mesolithic/Neolithic age shed light on prehistoric ceramicist's workshop. SkyScan Usermeeting 2011, 13.-15.04.2011, Leuven, Belgium. Micro-CT User Meeting Abstract Book ISBN 9789081678100, p. 248.
Kiel, S., Kahl, W.-A., Godert, J. L., Rouse, G. W. (2011) Osedax borings in fossil early Oligocene marine bird bones. SkyScan Usermeeting 2011, 13.-15.04.2011, Leuven, Belgium. Micro-CT User Meeting Abstract Book ISBN 9789081678100, p. 244.
Beier, K., Kahl, W.-A., Holzheid, A. (2011) Dissolution experiments of potential reservoir materials in CO2-bearing saline fluids. IOPD workshop GEOLOGICAL CARBON CAPTURE & STORAGE IN MAFIC AND ULTRAMAFIC ROCKS. Muscat, Sultanate of Oman 8-10 January, 2011.
Kahl, W.-A., Holzheid, A. (2010) Estimated and "true" geometric surfaces and their possible impact on experimentally and thermodynamically derived mineral dissolution and precipitation rates in CO2-brine-mineral reactions. DMG Tagung, Münster 19.09.-22.09.2010, Presentation S04-T02, p. 43.
Beier, K., Kahl, W.-A., Holzheid, A. (2010) Dissolution rates of calcite in CO2-bearing brines - a comparison of experimental and literature data. DMG Tagung, Münster 19.09.-22.09.2010, Presentation S04-T08, p. 52.
Soltan, A. M., Kahl, W.-A., Wendschuh, M., Hazem, M. (2010) Impact of thermal microstructural changes of Egyptian limestones on quicklime reactivity: mud-supported limestones. DMG Tagung, Münster 19.09.-22.09.2010, Poster P4-07, p. 242.
Kahl, W.-A., Hinkes, R., Feeser, V., Holzheid, A. (2010) Anisotropy of sandstones. SkyScan User Meeting 2010, 07.-09.07.2010, Mechelen, Belgium, Presentation #41.
Kiel, S., Kahl, W.-A., Godert, J. L., Rouse, G. W. (2010) 30 Million year old traces of the bone-eating worm Osedax. SkyScan User Meeting 2010, 07.-09.07.2010, Mechelen, Belgium, Poster #2.
Beier, K., Kahl, W.-A., Holzheid, A. (2010) Influence of temperature and reactive surface on dissolution rates of carbonates in CO2-bearing brine. Geophysical Research Abstracts, Vol. 12, EGU2010-0, EGU General Assembly 2010
Kahl, W.-A., Holzheid, A. (2009) X-ray computed microtomography in geoscience: two case studies. DMG Tagung, Halle 13.09.-16.09.2009, Abstract #118 (CD-ROM).
Beier, K., Kahl, W.-A., Holzheid, A. (2009) CO2-Sequestration on the laboratory scale - first results of chemical interaction processes between injected CO2, saline fluids and potential reservoir materials. DMG Tagung, Halle 13.09.-16.09.2009, Abstract #24 (CD-ROM).
Grevel, K.-D., Kahl, W.-A. (2009) High-temperature oxide melt calorimetry: the enthalpy of formation of topaz-OH, Al2SiO4(OH)2. Micro-Analysis, Processes, Time (MAPT): Annual Meeting 2009 of the Mineralogical Society of Great Britain and Ireland, 31.08. - 02.09.2009, Edinburgh, United Kingdom.
Kahl, W.-A., Holzheid, A. (2009) Quantifying porosities in sandstones: How to assess accuracy?. SkyScan User Meeting 2009, 22.-24.04.2009, Ghent, Belgium, Presentation #41.
Kahl, W.-A., Beier, K., and Holzheid, A. (2008) Determination of CO2-Solubilities in Complex Brines as Part of an Experimental Study on CO2-Sequestration on the Laboratory Scale, DMG Tagung, Berlin, 14.-17.09.2008, Abstract #204 (CD-ROM).
Grevel, K.-D., Navrotsky, A., Kahl, W.-A., Majzlan, J. & Lathe, C. (2003) Thermodynamic data of Mg-chloritoid, EGS-AGU-EUG conference, Nice, France.
Grevel, K-D; Navrotsky, A.; Kahl, W.- A.; Majzlan, J.; Lathe, C. (2003) Thermodynamic data of Mg-chloritoid, 81. Jahrestagung der Deutschen Mineralogischen Gesellschaft (Bochum 2003), 70.
Kahl, W.-A., Fockenberg, T., Gottschalk, M., Wolf- I. & Maresch, W. V. (2000) Crystal chemistry and enthalpy of formation of synthetic glaucophanic amphibol, Berichte der Deutschen Mineralogischen Gesellschaft, Beih. z. Eur. J. Mineral., 12, No. 1, 89.
Kahl, W.-A. & Maresch, W.V. (1999) Tremolite: Enthalpy of formation calculated from high-temperature, drop-solution calorimetry, Berichte der Deutschen Mineralogischen Gesellschaft, Beih. z. Eur. J. Mineral., 11, 114.
Schumacher, J.C. & Kahl, W.-A. (1999) Mineralogy and petrology of amphibole- and pyroxene-bearing assemblages from Mn-Quartzites (coticules), Southwestern New Hampshire, USA [invited], EOS supplement, 80, 359.
PhD Thesis
Kahl, W.-A. (2000) Hochtemperatur-Lösungskalorimetrie und Leistungsdifferenzkalorimetrie zur thermodynamischen Charakterisierung von Mineralen. PhD Thesis, Ruhr-Universität Bochum
Diploma Thesis
Kahl, W.-A. (1995) Mineralchemie und Phasenbeziehungen in granat-, amphibol- und erzführenden Quarziten von Südneuengland, USA, unpublished Diploma Thesis, Universität Kiel, 151 pp.