Development and optimization of crystallographic tools using the Rietveld method (BGMN-Param), the application for manganese nodules (BGMN-MeMa) and soil clay minerals (BGMN-HIM)

Begin of project: January 1, 2015

End of project: December 31, 2022

Status of project: May 22, 2019

BGR started a project with three work packages focusing on development of new tools for the Rietveld method, particularly the optimization of crystallographic tools (work package parameterization). In the other work packages we aim to test the application of these tools for manganese nodules from the German license area as well as for soils from acidic environments.

X-ray diffraction (XRD) allows the qualitative and quantitative determination of minerals in rocks. The BGR holds modern analytical equipment both in the XRD laboratory as well as additional analytical methods like infrared spectroscopy (IR), x-ray fluorescence analysis (XRF), element analysis of carbon and sulphur (Leco analyser), cation exchange capacity (CEC), thermal analysis (DTA-MS), scanning electron microscopy (SEM) particle size determination and many more.

The results of these methods, which may be fully quantitative or qualitative to semi-quantitative, will be used to choose representative specimen from large series of samples for further investigations (screening). They may also be used to combine all available analyses to a plausible over-all outcome (complex mineralogical phase analysis). Chemical data will be used to check the consistency of mineral contents, calculated with the Rietveld program BGMN (named after its developer Jörg Bergmann). There is no software tool so far to perform these adjustments in an at least semi-automatic mode. These very complex procedures will be simplified in the project “BGMN-Param” as a first step. The innovation of this approach is the connection of different observed data to achieve a sound model. This model allows the structural description of disordered minerals for the correct determination of mineral contents in mixtures.

The method of parametric Rietveld refinements will be established in a further step (figure 1) based on this. The parametric Rietveld refinement method allows the refinement of a complex model using multiple measurements collected under different conditions. This approach increases the significance of results and allows even the refinement of non-crystallographic parameters.

See also: Laboratory for mineralogy, sedimentology and colloid chemistry

Manganese nodules are made up of layers of Mn-Fe oxihydroxides which are concentrically formed around a nucleus. They mainly occur in 4.000 – 6.000m water depth. The last decade has witnessed a rising interest in Mn nodules because of their content of economically important base and high-tech metals such as Nickel, Copper, Cobalt, Molybdenum, Rare Earth Elements, Lithium, and Gallium. Apart from scientific interest regarding formation processes of the nodules, a main objective of current research focuses on the development of new methods for the effective and sustainable extraction of those metals. The basis for the development of such methods is a sound understanding of the crystallography of the Mn and Fe oxihydroxides. Therefore, the project BGMN-MeMa (metal binding in Manganese minerals) will investigate Mn minerals which are typically found in Mn nodules such as todorokite and the phyllomanganates birnessite and buserite. A special focus will be on the positions of the metals in the basal crystallographic units of the Mn phases. In a first step synthetic Mn minerals will be produced under defined lab conditions and analyzed using new analytical methods. The general aims of the project are to develop new Rietveld disordering models and to increase our understanding of the cation-exchange processes in Mn minerals of the deep-sea.

Acceptance of clay mineralogy is low in soil science as usually no quantitative mineral analysis can be obtained, particularly if compared with soil chemical methods. In the work package BGMN-HIM disordering model for hydroxy-intercalated minerals (secondary chlorite) will be developed aiming at improving quantitative clay mineral analysis of soils from acidic environments. In the past BGR has developed disordering models for clay minerals of the type illite-smectite, talc, palygorskite, and sepiolite. No such models are available for hydroxy-intercalated minerals yet. The mineralogical-crystalchemical challenge is that new strategies for the description of the observed disordering have to be developed. HIMs contain “pillars” of poorly ordered aluminum hydroxo polymers with varying degree of polymerization eliminating the swelling capacity. Some parts of the interlayers may however still be expandable upon gylcolization. The innovation of this project will be the development of such Rietveld disordering models and their application for quantitative phase analysis of acidic soils.

Contact:

Publications:

• Dietel, J., Dohrmann, R., Guggenberger, G., Meyer-Stüve, S., Turner, S., Schippers, A., Kaufhold, S., Condron, L.M., Mikutta, R. 2017. Complexity of clay mineral formation during 120,000 years of soil development along the Franz Josef chronosequence, New Zealand. New Zealand Journal of Geology and Geophysics 60, 23–35. doi: 10.1080/00288306.2016.1245668
• Dietel, J., Ufer, K., Kaufhold, S., Dohrmann, R. 2018. Unusual illite-dioctahedral vermiculite interstratification with Reichweite 2 in clays from Northern Hungary. European Journal of Mineralogy 30, 747-757 doi: 10.1127/ejm/2018/0030-2730
• Dietel, J., Gröger-Trampe J., Bertmer, M., Kaufhold, S., Ufer, K., Dohrmann, R.. Crystal Structure Model Development For Soil Clay Minerals – I. Hydroxy-interlayered smectite (HIS) synthesized from natural bentonite. A multianalytical study. Geoderma 347, 135-149. doi: 10.1016/j.geoderma.2019.03.021
• Dietel, J., Ufer, K., Kaufhold, S., Dohrmann, R. 2019. Crystal structure model development for soil clay minerals – II quantification and characterization of hydroxy-interlayered smectite (HIS) using the Rietveld refinement technique. Geoderma 347, 1-12. doi: 10.1016/j.geoderma.2019.03.020
• Heller, C., Kuhn, T., Versteegh, G. J. M., Wegorzewski, A.V., Kasten, S. 2018. The geochemical behavior of metals during early diagenetic alteration of buried manganese nodules. Deep Sea Research Part I: Oceanographic Research Papers. doi: 10.1016/j.dsr.2018.09.008
• Sommerfeld, M., Friedmann, D. Kuhn, T. Friedrich, B. 2018. "Zero-Waste": A sustainable approach on pyrometallurgical processing of manganese nodule slags. Minerals, 8, 544, doi:10.3390/min8120544
• Wegorzewski, A.V., Köpcke, M., Kuhn, T., Sitnikova, M.A., Wotruba, H. 2018. Thermal pre-treatment of polymetallic nodules to create metal (Ni, Cu, Co)-rich individual particles for further processing. Minerals 8, 523; doi: 10.3390/min8110523