Dr. rer. nat. Benjamin Walter

Dr. rer. nat. Benjamin Walter

  • Institut für Angewandte Geowissenschaften 
    Abteilung Geochemie und Lagerstättenkunde


    KIT - Karlsruher Institut für Technologie
    Campus Süd

    Adenauerring 20b, Gebäude 50.40
    76131 Karlsruhe

Current position

Assistant Professor/Research fellow

Present projects

I am interested in all kind of fluids responsible for ore-formation in magmatic, metamorphic, sedimentary and hydrothermal settings. My major research focus is to decipher processes leading to ore formation in carbonatites, alkaline-rocks and hydrothermal vein-type deposits. My current projects are:

Alkaline silicate rocks and carbonatites

  • The influence of crustal contamination on a late-stage REE-mineralization in carbonatites (collaboration with Gregor Markl, Michael Marks, Johannes Giebel, Tübingen)
  • The role of late-stage fluids in carbonatite and alkaline silicate rocks (collaboration with Gregor Markl, Michael Marks, Johannes Giebel, Tübingen)
  • The mineralogical control of geophysical exploration signatures (HiTech AlkCarb project)
  • New geomodels for exploring carbonatites and alkaline silicate rocks (HiTech AlkCarb project)
  • The genesis of the South African and Namibian alkaline provinces province (collaboration with Gregor Markl, Michael Marks, Johannes Giebel, Tübingen)
  • Reconstruction of hydrothermal system in volcanoes of the East African rift (collaboration with Will Hutchinson, St Andrews, Scotland)
  • Petrology and age-constrains of the SW-German alkaline province (collaboration with Gregor Markl and Michael Marks, Tübingen; Jens Grimmer KIT)
  • Shallow plumbing systems in alkaline and carbonatite complexes (HiTech AlkCarb project)

Hydrothermal vein type deposits

  • Trace element systematics of hematite-hosted fluid inclusions (cooperation with Gregor Markl, Michel Marks, Tübingen and Matthew Steele-MacInnis, Edmonton, Canada)
  • Mineralogical changes within a single vein and the relation to superregional events
  • Deciphering fluid migration pathways (cooperation with Mathias Burisch, Freiberg)
  • The geochemistry of native arsenic and arsenides in hydrothermal vein-type deposits (cooperation with Gregor Markl and Manuel Scharrer, Tübingen)
  • The genesis of ore shoots in hydrothermal veins (cooperation with Gregor Markl and Manuel Scharrer, Tübingen)
  • Kinetics of ore precipitation in hydrothermal systems

Other projects I contribute:

  • Dolomitization in oil reservoirs (cooperation with Adrian Immenhauser and Anton Kolchugin, Kazan, Russia)
  • How to bring hydrocarbons into crystalline basement rocks? (cooperation with Graham Banks, GEUS Copenhagen)
  • Testing the resilience of ancient early diagenetic dolomites as archives of their palaeo-environment (cooperation with Adrian Immenhauser and Mathias Müller, Bochum)

Funded projects

Single Projects:

MA 2563/19-1 Petrology and age of foidites in SW Germany

Foidites are mantle-derived and strongly SiO2-undersaturated volcanic rocks, with primitive olivine melilitites possibly representing primary magma compositions. Among the Palaeogene volcanic rocks in SW Germany, foidite occurrences are concentrated in seven areas (Kaiserstuhl, Upper Rhine graben, Bonndorf graben including Vosges, Hegau, Urach, Lower Neckar). Mineralogically, they range between olivine melilitites, nephelinites and haüynites, with clear differences between those areas. However, except for the Kaiserstuhl, their petrology has not been systematically investigated and their ages are not reliably constrained.

The proposed study will test the following hypotheses: (i) Mineralogical differences of the melilitite-nephelinite-haüynite series at the locations to be investigated relate to variable degrees and courses of magmatic differentiation of parental olivine melilititic magmas. (ii) The intrusion ages for these rocks relate to transient geodynamic settings that cause distinct melting events in the mantle manifested in distinct ages for the different areas to be studied.

To test these hypotheses, detailed petrographic and mineral chemical data (EMPA and LA-ICP-MS on minerals) will be combined with petrological modeling (T-aSiO2-fO2 conditions and differentiation paths) and geochronological data (LA-ICP-MS dating). The expected results will enable us to characterize the crystallization conditions and differentiation paths for the foidites at the different localities. Their comparison with each other will help to decipher potential genetic relations between the foidite types of each locality and will show if the courses of differentiation at the different localities are similar or different from each other. Such a comparative study has never been performed so far and the results are expected to have major implications on our understanding on the potential heterogeneity of the mantle domains below SW Germany. The results of this study will be integrated in recent models on the post-Variscan tectonic evolution in SW Germany.  

WA 3116/4-1 Effect and significance of contamination-related compositional melt variations of the Tweerivier and Bulhoekkop carbonatites, South Africa, with special reference to their REE mineralization

REE enrichment in carbonatitic melts are generally explained by a combination of parameters, including low-degree melting of geochemically enriched mantle sources, carbonate-silicate melt immiscibility, crystal fractionation, melt-aqueous brine immiscibility and hydrothermal alteration. However, the effect of crustal contamination, as a potential first order process is only weakly constrained. Nevertheless, our recent study of Kaiserstuhl carbonatites clearly provided evidence that the interaction of carbonatite magma with silicate wall rocks can enable strong REE enrichment in apatite via the britholite substitution mechanism involving Si. Based on the results from the Kaiserstuhl, the role of variable contaminants needs to be tested in detail to show if this process is of general importance in carbonatitic systems.

This project will investigate the impact of carbonatite-country rock interaction on REE enrichment in carbonatites. The study will be performed using field examples from the Tweerivier and Bulhoekkop carbonatites in the Republic of South Africa which are known to bear a large variability of crustal xenoliths and xenoliths of associated silicate rocks and contain variable amounts of silicate minerals (amphibole, clinopyroxene, mica, tremolite) that may indicate crustal contamination.

To test this hypothesis, whole rock data (XRF and ICP-MS), textural, mineral chemical and isotopic data (microscopy, EMPA, C and O-isotope systematics) will be carried out for the different carbonatites samples to study the effect of contamination by Fe, Mg, Al and Si-rich lithologies. The expected results will allow for (1)         Identification of the influence of contamination on the REE pattern of the residual melt. (2) Identification of mineralogical and compositional variation of major mineral phases.

MA 2135/26-1 Influence of crustal contamination on REE-enrichment in carbonatites of the Kalkfeld group (Namibia)

High levels of REE in carbonatites are generally explained by a combination of factors, including low-degree melting of geochemically enriched mantle sources, crystal fractionation, carbonate-silicate melt immiscibility, melt-aqueous brine immiscibility and hydrothermal alteration. Crustal contamination, however, is a process that is typically not considered to play an important role during carbonatite magmatism. Nevertheless, a recent study of the applicants demonstrated that the interaction of carbonatite magma with silicate wall rocks can enable strong REE enrichment in apatite via a coupled substitution mechanism involving Si. Having shown this for the Kaiserstuhl, the applicants suggest that such processes may be of general importance in carbonatitic systems.

This project will investigate the impact of carbonatite-wall rock interaction on REE enrichment in carbonatites. The study will be performed using field examples from the Damaraland Province (Namibia), because these carbonatites show variable REE enrichment and REE mineralogy and contain variable amounts of silicate minerals (amphibole, clinopyroxene, quartz, feldspar) that may indicate crustal contamination.

To test this hypothesis, textural, mineral chemical and geochronological data (microscopy, EMPA, LA-ICP-MS) as well as fluid inclusion data (microthermometry including numerical liquidus-surface modeling for quantification, Raman spectroscopy) for the different carbonatites which are probably genetic related will be gathered and compared with each other. The expected results will allow for (1) characterizing the magmatic to hydrothermal evolution of the carbonatites in great detail and (2) reconstructing the genesis of the REE mineralizations including the potential influence of wall-rock interaction and hydrothermal overprint.


DFG priority programme DOME Dynamics of Ore Metal Enrichment:

MA 2563/18-1 The role of early cumulate formation for HFSE enrichment in foidolitic systems.

Foidolites are mantle-derived and strongly SiO2-undersaturated plutonic cumulate rocks. Studies on economically interesting HFSE deposits associated with foidolitic rocks are generally rare, but the Gardiner Complex in E-Greenland and the Kovdor Complex in Russia were studied in some detail. The various lithologies of both complexes are believed to derive from a mela-nephelinitic parental magma. In both complexes a suite of peridotitic rocks (dunite & clinopyroxenite), melteigitic to urtitic rocks, foidolitic rocks (melilitolite) and carbonatite occur. Although the parental magma compositions are melanephelinitic for the Kovdor and Gardiner complexes, the mineralogical composition of melilitolite and carbonatite of these two complexes show clear differences: Melilitolite of the Gardiner Complex shows ore grade enrichment of perovskite in cumulates, whereas melilitolite at Kovdor contains only accessory perovskite. In contrast, Kovdor carbonatite is HFSE-mineralized, but at Gardiner these rocks are barren in HFSE. This project aims at comparing these two similar complexes in detail and to decipher the processes leading to the HFSE-enrichment in early cumulates at Gardiner and the late-stage HFSE-enrichment in the Kovdor carbonatite.

The proposed study will be guided by the following two working hypotheses: (i)   the mineralogical differences between the peridotitic rocks (minor chromite versus minor Ti-magnetite) and melilitolite (presence or absence of massive perovskite cumulates) at the Gardiner and Kovdor complexes relate to differences in their parental magma composition, which influenced the timing of perovskite saturation; (ii) the concentration of HFSE in carbonatite of Gardiner (low) and Kovdor (enriched) relate to the intensity of previous perovskite fractionation. To test these hypotheses, detailed petrographic, mineral chemical and petrological data for the different rock types of the two complexes will be gathered and thoroughly compared. Special focus will be given to the distribution of REE + HFSE (Zr, Hf, Nb, Ta) between apatite, clinopyroxene, olivine, perovskite, and melilitite. The project further aims at developing exploration indicators that will help to search for the different enrichment types within a complex (early cumulate versus late stage magmatic versus hydrothermal overprint).

Past projects

Petrology of the Kaiserstuhl

  • Fluid evolution of continental basement brines by microthermometry and crush leach analyses
  • Ore forming processes in hydrothermal vein-type deposits, Schwarzwald, Germany
  • Stable isotope chemistry of hydrothermal vein-type deposits
  • Mg-isotope systematics of hydrothermal carbonates (cooperation with A. Immenhauser, RUB Bochum, Germany)
  • Ore petrography and ore chemistry of hydrothermal vein-type deposits
  • Ore fluid evolution in the continental crystalline basement
  • Ore precipitation processes by LA-ICPMS analyses of single fluid inclusions (cooperation with C. Heinrich & M. Wälle ETH Zürich, Switzerland)
  • U-Pb age-dating of hydrothermal gangue and ore minerals (cooperation with A. Gerdes, Frankfurt, Germany)
  • Evolution of fluid pathways in crystalline basement (cooperation with C. Heinrich & M. Wälle ETH Zürich, Switzerland)
  • Multi-aquifer fluid mixing processes as first order processes for ore precipitation


Fluid Inclusion short course

This 1 SWS short course provides basic knowledge in microthermometrical analyses and data interpretation.

Field Trip: Hydrothermal ore forming processes, Schwarzwald

This 3 day field trip provides basic knowledge in mapping ore mineralizations in the field, relationship of host rock and hydrothermal veins and ore forming processes.

Field Trip: Isle of Mull, Scotland (2018)

Mapping Course Elba, Italy

Mapping Course Syros/Naxos, Greece



Personal information

Dipl. Mineraloge, Postdoc, supervisor of the microthermometry and cathodoluminescence microscopy labs

2006-2012 Diploma in Geoscience, Eberhard Karls University, Tuebingen

2012-2016 Ph.D in Mineralogy, Eberhard Karls University, Tübingen

Ph.D. thesis: Ore forming processes in hydrothermal vein-type deposits, Schwarzwald, Germany

05/2016 Postdoc, Eberhard Karls University, Tübingen (HiTech AlkCarb project)

The HiTech AlkCarb project is funded under the European Union's Horizon 2020 Research and Innovation programme, to develop new geomodels and sustainable exploration methods for alkaline igneous rocks and carbonatites (http://www.bgs.ac.uk/HiTechAlkCarb/). I was project partner in the EKUT team and we work in the Kaiserstuhl SW Germany on science question 1 in work package 2: „How can we predict what intrusive rocks are present at depth using volcanic carbonatites and alkaline rocks exposed at the surface?“

Since 05/2019 Assistant Professor and Research Fellow, Karlsruhe Institute of Technology (KIT)


Fluids associated with carbonatitic magmatism: A critical review and implications for carbonatite magma ascent.
Walter, B. F.; Giebel, R. J.; Steele-MacInnis, M.; Marks, M. A. W.; Kolb, J.; Markl, G.
2021. Earth science reviews, 103509. doi:10.1016/j.earscirev.2021.103509
Complex carbonate-sulfate brines in fluid inclusions from carbonatites: Estimating compositions in the system H2O-Na-K-CO3-SO4-Cl.
Walter, B.; Steele-MacInnis, M.; Giebel, R. J.; Marks, M. A. W.; Markl, G.
2020. Geochimica et cosmochimica acta. doi:10.1016/j.gca.2020.03.030
Formation of hydrothermal fluorite-hematite veins by mixing of continental basement brine and redbed-derived fluid: Schwarzwald mining district, SW-Germany.
Walter, B. F.; Jensen, J. L.; Coutinho, P.; Laurent, O.; Markl, G.; Steele-MacInnis, M.
2020. Journal of geochemical exploration, 212, Article: 106512. doi:10.1016/j.gexplo.2020.106512
Formation of native arsenic in hydrothermal base metal deposits and related supergene U6+ enrichment: The Michael vein near Lahr, SW Germany.
Scharrer, M.; Sandritter, K.; Walter, B. F.; Neumann, U.; Markl, G.
2020. American mineralogist, 105 (5), 727–744. doi:10.2138/am-2020-7062
Testing the preservation potential of early diagenetic dolomites as geochemical archives.
Mueller, M.; Igbokwe, O. A.; Walter, B.; Pederson, C. L.; Riechelmann, S.; Richter, D. K.; Albert, R.; Gerdes, A.; Buhl, D.; Neuser, R. D.; Bertotti, G.; Immenhauser, A.
2020. Sedimentology, 67 (2), 849–881. doi:10.1111/sed.12664VolltextVolltext der Publikation als PDF-Dokument
Combining Ion Chromatography and Total Reflection X-ray Fluorescence for Detection of Major, Minor and Trace Elements in Quartz-hosted Fluid Inclusions.
Ladenburger, S.; Walter, B. F.; Marks, M. A. W.; Markl, G.
2020. Journal of analytical chemistry, 75 (11), 1477–1485. doi:10.1134/S106193482011009X
A comparative study of two Mississippian dolostone reservoirs in the Volga-Ural Basin, Russia.
Kolchugin, A.; Immenhauser, A.; Morozov, V.; Walter, B.; Eskin, A.; Korolev, E.; Neuser, R.
2020. Journal of Asian earth sciences, 199, 104465. doi:10.1016/j.jseaes.2020.104465

Publications until 2018


Epp,T. , Walter, B.F., Scharrer, M., Lehmann, G., Henze, K., Heimgärtner, C., Bach, W. and Markl, G. (2018): Quartz with associated Sb-Pb-Ag±Au mineralization in the Schwarzwald, SW Germany: a record of metamorphic cooling, tectonic rifting and element remobilization processes in the Variscan belt. Mineralium Deposita. DOI: 10.1007/s00126-018-0855-8 

Braunger, S., Marks, M.A.W., Walter, B.F., Neubauer, R., Reich, R., Wenzel, T., Parsapoor Anis & Markl, G. (2018). The Petrology of the Kaiserstuhl Volcanic Complex, SW Germany: The Importance of Metasomatized and Oxidized Lithospheric Mantle for Carbonatite Generation. Journal of Petrology. Journal of Petrology 59 (9), 1731-1762. External Link

Walter, B.F., Gerdes, A., Kleinhanns, I. C., Dunkl, I., von Eynatten, H., Kreissl, S., & Markl, G. (2018): The connection between hydrothermal fluids, mineralization, tectonics and magmatism in a continental rift setting: fluorite Sm-Nd and hematite and carbonates U-Pb geochronology from the Rhinegraben in SW Germany. Geochimica et Cosmochimica Acta 240, 11-42. External Link

Walter B.F., Parsapoor A., Braunger S., Marks M.A.W., Wenzel T., Martin M., Markl G. (2018): Pyrochlore as a monitor for magmatic and hydrothermal processes in carbonatites from the Kaiserstuhl volcanic complex (SW Germany). Chemical Geology 498, 1-16. External Link

Keim, M. F., Walter, B. F., Neumann, U., Kreissl, S., Bayerl, R. & Markl, G. (2018): Polyphase enrichment and redistribution processes in silver-rich mineral associations of the hydrothermal fluorite-barite-(Ag-Cu) Clara deposit, SW Germany. Mineralium Deposita 53, 1-20. External Link

Kreissl, S., Gerdes, A., Walter, B.F., Neumann, U., Wenzel, T. and Markl, G. (2018): Reconstruction of a >200 Ma multi-stage “five element” Bi-Co-Ni-Fe-As-S system in the Penninic Alps, Switzerland. Ore Geology Reviews. External Link

Walter, B.F., Burisch, M., Fusswinkel, T., Marks, M.A.W., Steele-MacInnis, M., Wälle, M., Apukhtina, O., Markl, G. (2018): Multi-reservoir fluid mixing processes in rift-related hydrothermal veins, Schwarzwald, SW-Germany. Journal of Geochemical Exploration 186, 158-186. External Link

Burisch, M., Walter, B.F., Gerdes, A., Lanz, M. and Markl, G. (2018): Late-stage anhydrite-gypsum-siderite-dolomite-calcite assemblages record the transition from a deep to a shallow hydrothermal system in the Schwarzwald mining district, SW Germany. Geochimica and Cosmochimica Acta 223, 259-278. External Link


Walter, B.F., Steele-MacInnis, M. and Markl, G. (2017): Sulfate brines in fluid inclusions of hydrothermal veins: Compositional determinations in the system H2O-Na-Ca-Cl-SO4. Geochimica et Cosmocimica Acta, 209, 184-203. External Link

Burisch, M., Walter, B.F. and Markl, G. (2017): Silification of hydrothermal gangue minerals in Pb-Zn-Cu-fluorite-quartz-baryte veins. Canadian Mineralogist 55, 1-14. External Link

Walter, B.F., Burisch, M., Marks, M.A.W. & Markl, G. (2017): Major element composition of fluid inclusions from hydrothermal vein-type deposits record eroded sedimentary Units in the Schwarzwald district, SW Germany. Mineralium Deposita 52(8), 1191-1204 External Link.


Burisch, M., Gerdes, A., Walter, B.F., Neumann, U., Fettel, M. and Markl, G. (2016): Methane and the origin of five-element veins: Mineralogy, age, fluid inclusion chemistry and ore forming processes in the Odenwald, SW Germany. Ore Geology Reviews. DOI:10.1016/j.oregeorev.2016.10.033 External Link

Walter, B.F., Burisch, M., Markl, G. (2016): Long-term chemical Evolution and modification of Continental Basement brines - a field study from the Schwarzwald, SW Germany. Geofluids. DOI: 10.1111/gfl.12167 External Link.

Burisch, M., Walter, B.F., Wälle, M. and Markl, G. (2016): Tracing fluid migration pathways in root zone below unconformity-related hydrothermal veins: Insights from trace element systematics of individual fluid inclusions. Chemical Geology 429, 44-50. External Link

Kolchugin, A., Immenhauser, A., Walter, B., Morozov, V.P. (2016): Diagenesis of the palaeo-oil-water transition zone in a Lower Pennsylvanian carbonate reservoir: Constraints from cathodoluminescence microscopy, microthermometry, and isotope geochemistry. Marine and Petroleum Geology 72, 45-61. External Link


Walter, B.F., Immenhauser, A., Geske, A. and Markl, G. (2015): Exploration of hydrothermal Carbonate Magnesium isotop signatures as Tracers for Continental fluid aquifers, Schwarzwald mining district, SW Germany. Chemical Geology 400, 87-105. External Link


Bons, P.; Fusswinkel, T.; Gomez-Rivas, E; Markl, G.; Wagner, T.; Walter, B. (2014): Fluid mixing from below in unconformity-related hydrothermal ore deposits. Geology 42(12), 1035-1038. External Link



Fieldwork Serra de Monchique Oct 2020

Fieldwork Namibia Dec 2019

HiTech AlkCarb field trip Namibia 2018

HiTech AlkCarb field trip Greenland 2017

HiTech AlkCarb field trip Scotland 2017

HiTech AlkCarb field trip Malawi 2016