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Positions Held

• since Jan. 2009: Institut für Mineralogie, Universität Münster.
• Aug. 2006-Dec. 2008: Senior postdoc position at the centre for Physics of Geological Processes (PGP), University of Oslo (Norway), Research topics: physical and geochemical consistent numerical solution for reactive fluid flow in rocks under high-pressure / low-temperature conditions, based on field observations.
• Jan. 2002-Aug. 2006: Postdoctoral Fellow. Research project part of SFB 574 Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanism for Natural Disasters at Kiel University. P-T-t-X and isotopic investigations of subducted fragments of former oceanic lithosphere to understand element and volatile losses in subducting slabs.
• Nov 2000-Jun. 2001: Visiting scientist at the Zentrallabor für Geochronologie at Mineralogical Institute, University of Münster, Germany.
• Mar. 1998-Dec. 2001: Research associate, Kiel University, Germany; Dissertation project: petrological, geochemical, and geochronological investigations on high-pressure rocks of Zambia.
• Feb. 1991-Nov. 1991: Drilling assistant (pratical) in a geological pilot study in Bitterfeld (Germany), Noell Umweltdiensten. Duties included soil sampling with different techniques at different depths and to develop maps about the pollution and hazard potential of the investigated area.

Education

• Jul. 2012: Habilitation in Geology/Mineralogy, University of Münster, Germany.
  • Thesis: Physical and chemical processes during the dehydration of subducting oceanic lithosphere: Reactive fluid flow under high-pressure conditions.

• Dec. 2001: Dr. rer. nat., University of Kiel, Germany
  • Thesis: Subduction and continental collision in the Lufilian Arc - Zambezi Belt orogen: A petrological, geochemical, and geochronological study of eclogites and whiteschists (Zambia).

• Feb. 1998: Diplom in Geology, University of Bremen, Germany
  • Thesis: Metamorphic and geodynamic evolution of the southern Ashanti Belt (SW Ghana), in German; Mapping: Geological mapping of the Palaeozoic / Cenozoic units of the north-western Gulf of Suez (Egypt) in German.

• Apr. 1994: Diplomvorprüfung in Geology, RWTH Aachen, Germany.
• Mar. 1998-Dec. 2001: Doctoral student, University of Kiel, Germany.
• Oct. 1994-Feb. 1998: Student of Geology, University of Bremen, Germany.
• Apr. 1992-Jul. 1994: Student of Mineralogy and Geology, RWTH Aachen, Germany.

Professional affiliation

• European Geosciences Union
• European Association of Geochemistry
• Deutsche Mineralogische Gesellschaft
• Geologische Vereinigung

Current Research Topics

Physical and chemical processes during the dehydration of subducting oceanic lithosphere (reactive fluid flow under high-pressure / low-temperature conditions).
During subduction, downgoing plates heat up and their hydrous minerals become progressively unstable and break down to produce water. It is now evident that the released fluids can reach the mantle wedge and cause melting. The most prominent metamorphic reaction occurring in subduction zones is the eclogitization of oceanic crust. It is commonly assumed that the density increase of this reaction makes plate subduction self-sustained. Seismic studies indicate that this transformation happens under non-equilibrium conditions and field evidence points to fluids as a trigger. The details of intra-slab fluid flow are, however, not yet understood. Field evidence points to not yet quantified relationships between reactions, fluid flow, seismicity and mobilization of both major and trace elements. I use a combined field and laboratory based approach to explore the interrelationships of these processes. I investigate how fluids migrate inside slabs (i.e. if fluid migration occurs main ly by distributed porous flow or by channelized fluid flow) and furthermore the interrelation between fluid flow and seismic slip.

Reactive fluid flow and transport of so-called fluid-immobile elements.
The presence of fluids in Earth's crust results in processes that enable significant element mobilization. Metasomatic changes in rocks due to open system reactive fluid flow often cause surprisingly high solubilities and transport rates of so-called fluid-immobile elements, such as HFSE (high field strength elements, e.g., Th, Nb, Ta, Ti) and the REE (rare earth elements). During metasomatism new minerals form which are more stable under the changing physical and chemical conditions. The associated element transport and mineral growth may finally result in economic ore mineralization. We are currently investigating how titanium, tantalum, and niobium (Ti-Nb-Ta) are mobilized and transported and how Nb-Ta are fractionated, even though they are regarded as geochemical identical twins. Metasomatic processes are also interesting with respect to thorium (Th), because this rather immobile element becomes redistributed and concentrated into accessory minerals, while the host rocks experience infiltration of highly oxidizing fluids.

Global chlorine-cycle: halogen concentrations and stable isotopes as tracer for fluid related processes.
The large recycling machines, such as subduction zones and spreading centres, are important for element exchange and transport on Earth. Even though the volatile element chlorine represents an important component of the fluids stored in subducting oceanic lithosphere, the behaviour of chlorine within subduction zones and during the formation of magmas in island arc, in plumes or at spreading ridges is not understood yet. This part of my research is mainly emphasised to establish a conservative trace for subduction zone fluids, i.e. halogen ratios and stable chlorine isotopes (delta37Cl), to identify different fluid sources and to quantify fluid-rock interaction and fluid fluxes. Therefore two main topics are currently in investigation, one is to define the Cl-isotopical signal of the main fluid sources of the deeper fluid cycle, i.e. serpentinite and blueschist dehydration; the other is to investigate how conservative the Cl-isotopes behave during fluid flow and fluid-rock in teraction. I will also try to find "fluid-composition-indicative" minerals to use those as a fluid-probe.

Evolution of craton margins during continent break up and continental collisions (reconstruction of supercontinents and the break up of Gondwana).
Geodynamic processes during orogenesis cause changes in pressure and temperature conditions (P-T conditions), which affect the rocks within an orogen. The reconstruction of the P-T evolution of a metamorphic rock allows to determine the geodynamic causes of metamorphism (e.g., subduction, tectonic thickening, extension during orogenic collapse or rifting, erosion, magmatic underplating). To be able to distinguish between the possible causes for metamorphism and to get a more complete understanding of geodynamic processes the knowledge of the age and the duration of metamorphic events, i.e. the P-T-t path, is essential. My current research is mainly focused on the geodynamic reconstruction of the Neoproterozoic to Cambrian orogens of south central Africa, which are related to the formation of the supercontinent Gondwana. I started to investigate the geodynamic evolution of the Tianshan melange zone (NW China) as a prime example for a cold subduction zone and the cont inetal margin of Ghana as a prime example for rifting processes along oceanic and continental transform margins.

Current Grants

• “Timing and rates of fluid release during the dehydration of subducting oceanic crust: reactive fluid flow under high-pressure conditions”; research project with doctoral student position; three years funded through DFG grant (JO 349/5-1).
• “Halogen concentrations and stable Cl isotopes in apatite as a fluid probe: mapping regional-scale fluid pulses by Cl-isotopes”; research project with doctoral student position; three years funded through DFG grant (JO 349/3-1).

Expeditions and Field Work

• Egypt and Ghana (1996)
• Malawi and Zambia (1998; 1999)
• Vendée (France; 2002)
• Cabo Ortegal (Spain; 2002)
• Raspas Complex (Ecuador; 2002)
• Ligurian Alps (Italy; 2005; 2007)
• Tianshan (China; 2003; 2005; 2006; 2011)
• Western Gneiss Region and Bamble Complex (Norway; 2006; 2007; 2010)
• New Caledonia (March 2012)
  Planed expeditions: Tianshan (August 2012)

Teaching

Lectures and Practicals

• Rocks, Minerals, Fluids / Mineralogical processes (since 2009) - Münster University, with A. Putnis.
• Current Topics in Mineralogy (since 2011) - Münster University, with A. Putnis.
• Mineralogy, Petrology and Geochemistry (2007) - Oslo University, with T. Andersen.
• Isotope Geochronology and Geochemistry (2005, 2006) - Kiel University.
• Microscopy of Magmatic Rocks (since 2009) - Münster University.
• Mineral optics (since 2009) - Münster University.

Student Field Trips

• Geology of Southern Germany (14 days): The Variscian mountain belt, the Mesozoic “Schichtstufenland”, and the Ries – impact, sedimentology, volcanology and metamorphic petrology; Excursion designed for students who have completed their first year; (2003-2005) Kiel University.
• Metamorphic Petrology of the Oslo Region: Introduction into field-based petrology; One day in 2007. Excursion for students taking the Mineralogy, Petrology, and Geochemistry course, Oslo University.
• The Alpine and Hercynian geology of Corsica (14 days): The Hercynian basement, the Alpine high-pressure belt, and sedimentary basin formation - sedimentology, structural geology, and metamorphic and magmatic petrology; Excursion for master students; (2011) Münster University.

2012

• John, T., Gussone, N., Podladchikov, Y. Y., Bebout, G. E., Dohmen, R., Halama, R., Klemd, R., et al. (2012). Volcanic arcs fed by rapid pulsed fluid flow through subducting slabs. Nature Geoscience, 5, 489–492.
• Halama, R., Bebout, G., John, T. & Scambelluri, M. (2012). Nitrogen recycling in subducted mantle rocks and implications for the global nitrogen cycle. International Journal of Earth Science. DOI: 10.1007/s00531-012-0782-3
• Lisker, F. & John, T. (accepted). How much denudation at the Ghana transform margin? - A review of the offshore apatite fission track record. Earth Surface Processes and Landforms.
• Herms, P., John, T., Bakker, R.J. & Schenk, V. (2012). Evidence for channelized external fluid flow and element transfer in subducting slabs (Raspas Complex, Ecuador). Chemical Geology, 310-311, 79-96.
• van der Straaten, F., Halama, R., John, T., Schenk, V., Hauff, F. & Andersen, N. (2012). Tracing the effects of high-pressure metasomatic fluids and seawater alteration in blueschist-facies overprinted eclogites: Implications for subduction channel processes. Chemical Geology, 292-293, 69-87.

2011

• John, T., Scambelluri, M., Frische, M., Barnes, J.D. & Bach, W. (2011). Dehydration of subducting serpentinite: implications for halogen mobility in subduction zones and the deep halogen cycle. Earth and Planetary Science Letters, 308, 65-76.
• Smit, M., Scherer, E., John, T. & Janssen, A. (2011). Creep of garnet in eclogite: mechanisms and implications. Earth and Planetary Science Letters, 311, 411-419.
• Klemd, R., John, T., Scherer, E.E., Rondenay, S. & Gao, J. (2011). Change in dip of subducting slabs at greater depths: petrological and geochronological evidence from HP-UHP rocks (Tianshan, NW-China). Earth and Planetary Science Letters, 310, 9-20.
• John, T., Klemd, R., Klemme, S., Pfänder, J., Hoffmann, J.E. & Gao, J. (2011). Nb-Ta fractionation by partial melting at the titanite-rutile transition. Contributions to Mineralogy and Petrology, 161, 35-45.
• Meyer, M., John, T., Brandt, S. & Klemd, R. (2011). Trace element composition of rutile and the application of Zr-in-rutile thermometry to UHT metamorphism (Epupa Complex, NW Namibia). Lithos, 126, 388-401.
• Raufaste, C., Jamtveit, B., John, T., Meakin, P. & Dysthe, D.K. (2011). The mechanism of porosity formation during solvent-mediated phase transformations. Proceedings of the Royal Society A, 467, 1408-1426.
• Halama, R., John, T., Herms, P., Hauff, F. & Schenk, V. (2011). A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab. Chemical Geology 281, 151-166.

2010

• John, T., Layne, G., Haase, K. & Barnes, J.D. (2010). Chlorine isotope evidence for crustal recycling into the Earth´s mantle. Earth and Planetary Science Letters, 298, 175-182.
• Putnis, A. & John, T. (2010). Replacement processes in the Earth’s crust. Elements, 6, 159-164.
• Beinlich, A., Klemd, R., John, T. & Gao, J. (2010). Trace-element mobilization during Ca-metasomatism along a major fluid conduit: eclogitization of blueschists as a consequence of fluid-rock interaction. Geochimica et Cosmochimica Acta, 74, 1892-1922.
• John, T., Scherer, E.E., Schenk, V., Herms, P., Halama, R. & Garbe-Schönberg, D. (2010). Subducted seamounts in an eclogite-facies ophiolite sequence: The Andean Raspas Complex, SW Ecuador. Contributions to Mineralogy and Petrology, 159, 265-284.
• Halama, R., Bebout, G. E., John, T. & Schenk, V. (2010). Nitrogen recycling in subducted oceanic lithosphere: the record in high- and ultrahigh pressure metabasaltic rocks. Geochimica et Cosmochimica Acta. 74, 1636-1652.

2009

• John, T., Medvedev, S., Rüpke, L.H., Podladchikov, Y., Andersen, T.B. & Austrheim, H. (2009). Generation of intermediate-depth earthquakes by self-localizing thermal runaway. Nature Geoscience, 2, 137-140.
• Adamuszek, M., John, T., Dabrowski, M., Podladchikov, Y.Y. & Gertisser, R. (2009). Assimilation and diffusion during xenolith-magma interaction: A case study of the Variscan Karkonosze granite, Bohemian Massif. Mineralogy and Petrology, 97, 203-222.
• Schmidt, A., Weyer, S., John, T. & Brey, G.P. (2009). HFSE systematics of rutile-bearing eclogites: New insights into subduction zone processes and implications for the Earth's HFSE budget. Geochimica et Cosmochimica Acta, 73, 455-468.

2008

• John, T., Klemd, R., Gao, J. & Garbe-Schönberg, C-D. (2008). Trace-element mobilization in slabs due to non steady-state fluid-rock interaction: constraints from an eclogite-facies transport vein in blueschist (Tianshan, China). Lithos, 103, 1-24.
• van der Straaten, F., Schenk, V., John, T. & Gao, J. (2008). Blueschist-facies rehydration of eclogites: implications for subduction channel fluid-rock interaction from the Tianshan, NW China. Chemical Geology, 255, 195-219.
• Iyer, K., Austrheim, H., John, T. & Jamtveit, B. (2008). Serpentinization of the oceanic lithosphere and some geochemical consequences: Constraints from the Leka Ophiolite Complex, Norway. Chemical Geology, 249, 66-90.

2007

• Zack, T. & John, T. (2007). An evaluation of reactive fluid flow and trace-element mobility in subducting slabs. Chemical Geology, 239, 199-216.
• Gao, J., John, T., Klemd, R. & Xiong, X. (2007). Mobilisation of Ti-Nb-Ta during subduction: insights from rutile precipitates in eclogite-facies segregations and veins (Tianshan, NW China). Geochimica et Cosmochimica Acta, 71, 4974-4996.

2006 and before

• John, T. & Schenk, V. (2006). Interrelations between intermediate-depth earthquakes and fluid flow within subducting oceanic plates: constraints from eclogite-facies pseudotachylytes. Geology, 34, 557-560.
• Xiong X., John T., Gao J., Klemd R. & Huang D. (2006). Trace element mobilization in subducted slabs: Constraints on an eclogite-facies transport vein from the western Tianshan, NW China. Acta Geologica Sinica, 80, 53-60.
• John, T., Scherer, E., Haase, K. & Schenk, V. (2004). Trace element fractionation during fluid-induced eclogitization in a subducting slab: trace element and Lu-Hf / Sm-Nd isotope systematics. Earth and Planetary Science Letters, 227, 441-456.
• John, T., Schenk, V., Mezger, K. & Tembo, F. (2004). Timing and P-T evolution of whiteschist metamorphism in the Lufilian Arc-Zambezi Belt orogen (Zambia): implications to the Gondwana assembly. The Journal of Geology, 112, 71-90.
• John, T. & Schenk, V. (2003). Partial eclogitisation of gabbroic rocks in a late Precambrian subduction zone (Zambia): prograde metamorphism triggered by fluid infiltration. Contributions to Mineralogy and Petrology, 146, 174-191.
• John, T., Schenk, V., Haase, K., Scherer, E. & Tembo, F. (2003). Evidence for a Neoproterozoic ocean in south central Africa from MORB-type geochemical signatures and P-T estimates of Zambian eclogites. Geology, 31, 243-246.
• John, T., Klemd, R., Hirdes, W. & Loh, G. (1999). The metamorphic evolution of the Paleoproterozoic (Birimian) volcanic Ashanti belt (Ghana, West Africa). Precambrian Research, 98, 11-30.
• John, T., Klemd, R., Hirdes, W. & Loh, G. (1998). The metamorphic evolution of the Paleoproterozoic (Birimian) gold-bearing Ashanti volcanic belt, West Africa. Zeitschrift für Angewandte Geologie, 44, 108-110.

Invited Conference Talks

• John, T., Podladchikov, Y. (2012). Lithium-speedometric constraints on duration and kinetics of fluid-rock interaction. EU project: DELTAMIN meeting, Oviedo, Spain.
• John, T., Podladchikov, Y., Gussone, N., Bebout, G., Halama, R., Magna, T. & Klemd, R. (2011). On the duration and rates of fluid release from a dehydrating slab. Goldschmidt conference.
• John, T., Gussone, N., Beinlich, A., Halama, R., Bebout, G., Podladchikov, Y. & Magna, T. (2010). Pulse-like channelled long-distance fluid flow in subducting slabs. Eos Transactions AGU, Fall Meeting Supplements.
• Gussone, N., John, T., Beinlich, A. & Bebout, G. (2010). Calcium isotopes as tracers of high-pressure subduction-zone fluid-rock interaction. Goldschmidt conference.
• John, T., Podladchikov, Y., Klemd, R. & Magna, T. (2010). Dehydrating slabs – mechanisms, flow structures, and rates. EGU conference, KEYNOTE.
• Raufaste, C., Mathiesen, J., Jamtveit, B. John, T. & Dysthe, D.K. (2010). Mechanism of permeability enhancement during chemical alteration. Nordic Geological Winter Meeting, KEYNOTE.
• John, T. (2007). Reactive fluid flow in slabs – a metamorphic view on the origin of the slab component. Goldschmidt conference. Geochimica Cosmochimica Acta, 71, A447. KEYNOTE
• John, T., Austrheim, H., Schmid, D.W., Rüpke, L. & Podladchikov Y. (2007). Interplay of deformation, fluid infiltration and eclogitization. Goldschmidt conference. Geochimica Cosmochimica Acta, 71, A447.
• John, T. (2007). Reactive fluid flow in slabs – a metamorphic view on the origin of the slab component. MARGINS and SFB-574 Workshop to Integrate Subduction Factory and Seismogenic Zone Studies in Central America. Online abstract volume. KEYNOTE
• Halama, R., John, T., Schenk, V., McDonough, W.F. & Rudnick, R.L. (2007). Li isotope fractionation in the subducted slab – a case study from the Raspas complex, Ecuador. Goldschmidt conference. Geochimica Cosmochimica Acta, 71, A370.
• Zack, T. & John, T. (2006). Channelization and reactive fluid flow in subducting slabs. Goldschmidt conference, Geochimica Cosmochimica Acta, 70, A728.
• Klemd, R., Gao, J. & John, T. (2006). Trace element-enriched fluids released during slab dehydration: implications for oceanic slab - mantle wedge transfer. Goldschmidt conference, Geochimica Cosmochimica Acta, 70, A323
• John, T. & Schenk, V. (2005). Interrelations between intermediate-depth earthquakes and fluid flow in subducting oceanic plates. EGU conference, Geophysical Research Abstracts, 7, EGU05-A-022218.
• John, T., Scherer, E., Haase, K. & Schenk, V. (2005). Does fluid-induced eclogitization of slab crust generate arc signatures? Goldschmidt conference, Geochimica Cosmochimica Acta, 69, A650.
• Gao, J., John, T. & Klemd, R. (2005). Partial dehydration of blueschist: insights into the slab-wedge transfer. Goldschmidt conference, Geochimica Cosmochimica Acta, 69, A653.

Invited Seminar Talks

• Lithium-chronometric constraints on duration and kinetics of fluid-rock interaction: implications for the subduction zone fluid flow system. Seminar of Institute for Geochemsitry and Petrology, ETH Zürich (2012), Switzerland.
• Dehydrating slabs – mechanisms, flow structures, and rates. Colloquium of the Institute for Geoscience, Universität Freiburg (2011), Germany.
• On the duration of fluid release from a dehydrating slab – mechanisms, flow structures, and rates. Seminar of the Institute of Geoscience and Geophysics of the Chinese Academy of Science, Beijing (2011), China.
• Dehydrating slabs – mechanisms, flow structures, and rates. Colloquium of the Institute for Geological Science, Freie Universität Berlin (2011), Germany.
• Dehydrating slabs – mechanisms, flow structures, and rates. Seminar of the Petrology Group, Bochum University (2011), Germany.
• Entwässerung in Subduktionszonen: Mechanismen, Raten sowie geochemische und geophysikalische Konsequenzen. University of Bremen, lecture series „Fluide in der Erde“(2011), Germany.
• Channelled fluid flow through slabs: mechanisms, chemistry, rates. Seminar of the Woods Hole Oceanographic Institution, USA, February 2010.
• Self-localizing thermal runaway as a mechanism for intermediate to deep focus earthquakes. SFB 574 Seminar 2008, University of Kiel, Germany.
• Reactive fluid flow in slabs  – a metamorphic view on the origin of the slab component and some new concepts of flow pattern formation. Seminar of the Department of Earth and Planetary Sciences 2007, University of New Mexico, USA.
• Interrelations among Intermediate-Depth Earthquakes and Fluid Flow in Subducting Oceanic Plates and the Origin of the Geochemical Arc Signature -a metamorphic view on the deep subduction zone fluid cycle-. Seminar of the Department of Earth Sciences 2006, Boston University, USA.
• Interrelations between intermediate-depth earthquakes and fluid flow within subducting oceanic plates: constraints from eclogite-facies pseudotachylytes. PGP invited-seminar 2005, Centre for Physics of Geological Processes, University of Oslo, Norway.
• Partial dehydration of blueschists: insights into the slab-wedge transfer. Mineralogisches Seminar 2005, University of Münster, Germany.
• Does fluid-induced eclogitization of slab crust generate arc signatures? Mineralogisches Seminar 2005, University of Frankfurt, Germany.
• Geochemical and petrological evidence for a palaeosubduction zone: constraints from Zambian eclogites. Geochemisch-Petrologisches Seminar 2001, University of Göttingen, Germany.