Conference Agenda

Overview and details of the sessions of this conference. Please select a date or location to show only sessions at that day or location. Please select a single session for detailed view (with abstracts and downloads if available).

Session Overview
7.1-1 Spectroscopic methods in modern geosciences
Wednesday, 22/Sept/2021:
9:00am - 10:30am

Session Chair: Melanie Kaliwoda, SNSB /LMU
Session Chair: Jörg Göttlicher, KIT

Session Abstract

Spectroscopic methods with their capability to gain information on atoms and molecules are becoming more and more relevant in earth sciences in order to open up new fields of research and to solve problems in the various scientific disciplines. Therefore, it is important to have an exchange, which methods are especially suitable for different requirements. The session Spectroscopic methods in modern geosciences is addressed to all geoscientific researchers who use spectroscopic technologies such as Raman, Infrared (IR), UV/Vis, X-ray, Electron and Nuclear Magnetic Resonance (NMR) Spectroscopy as well as Mass spectrometry (MS). Also contributions of investigations that involve a spectroscopic method not listed here are highly welcome.

9:00am - 9:30am
Session Keynote

The spectroscopy of luminescent geological materials

Ian M. Coulson

University of Regina, Canada

Luminescence is the non-incandescent emission of light from materials excited by an electron beam. Electron irradiation raises sample electrons to an excited state, which then emit a photon as they return to a lower energy. Luminescence phenemona may be studied in several ways, including spectral and spatial methods. Whilst cathodolominescence (CL) has become an established method of analysis for Earth materials, other forms of luminescence in minerals should not be overlooked. Photoluminescence (PL) studies, for example, allow for emission and excitation spectroscopy to be examined in weak- to strongly luminescent minerals, such as wilmenite. In the case of quartz PL, emission spectroscopy investigations have shown that excitation at different wavelengths produces highly variable emission spectra that relate to one or more transitions for excitation. As the building blocks to rocks, minerals and the atoms or ions within preserve critical information concerning the conditions attending growth or subsequent evolution - thus, investigation of these can inform on the origin or surface/near surface interactions relating to environmental change. As a non-destructive technique used in the study of rare materials (e.g., Lunar meteorites) luminescence imaging and spectroscopy have the potential to help characterise, as well as, elucidate domains or reveal fine-scale features not resolvable by optical methods. Advances in instrumentation now permit the collection of multi-dimensional data sets (e.g., hyperspectral) that can be interrogated off-line. The simultaneous capture and interpretation of compositional and luminescence signals has the potential to greatly improve our understanding of causes of luminescence, be these trace activator or defect.

9:30am - 9:45am

Zircon Raman dating: Age calculation and data valuation

Birk Härtel, Raymond Jonckheere, Lothar Ratschbacher

Geology, TU Bergakademie Freiberg, Germany

Zircon Raman dating is a debated concept in thermochronology. It is based on the disruption of the zircon lattice by α-disintegration of 238U, 235U, 232Th, and their daughter nuclides. This radiation damage leads to broadening of the Raman bands. A date is calculated from the measured Raman bandwidths, and the effective Uranium (eU) content, measured in the same spot. Radiation damage anneals at elevated temperatures; thus the Raman date is interpreted with regard to its closure temperature (Tc) as an event, cooling or mixed age, depending on the thermal history of the sample. We present zircon Raman ages calculated from the widths of the 439, 1008, and 356 cm-1 Raman bands for samples with different thermal histories. We discuss: (1) criteria for evaluating the Raman data by inter-band comparison; (2) the effect of partial annealing on the dating results; (3) the spatial matching of Raman and eU microanalysis.

9:45am - 10:00am

Raman spectroscopy as a functional scientific examination method for minerals, rocks and meteorites in the modern Geosciences

Melanie Kaliwoda1, Malte Junge1, Felix Hentschel1, Wolfgang W. Schmahl1, Fabian Dellefant2, Claudia Trepmann2

1Mineralogical State Collection Munich, SNSB and Ludwig Maximilians University, LMU, Germany; 2Ludwig Maximilians University, LMU, Germany

Raman spectroscopy is becoming an increasingly important investigative tool in modern geosciences. So it has been applied in the examination of a variety of materials, including meteoritic and igneous rocks, as well as natural and synthetic minerals and crystals.

This is not least due to the many advantages of Raman spectroscopy, like very fast measurements, small spot size or different samples consistency.

One main investigation area are meteorites, because new space mission programs to Moon and Mars are underway. In these new missions, robots are equipped with analytical instruments to probe the chemistry and constitution of the materials on the surface of the respective bodies. One of the promising mobile techniques is Raman spectroscopy. Therefore, the experience and measurement of comparable samples like meteorites, basalts or ophiolitic material helps us a lot. Several types of different meteorites have already been investigated here, for example, those recovered from the Neuschwanstein, Almahatta Sitta, Braunschweig or Tscheljabinsk fall. Furthermore, we started to investigate Meteorites from the Moon and Mars.

Raman methods can also help to study mineral compositions, because the spectra can aid in the classification, based upon crystal structure and mineral composition. In combination with electron microprobe, it is a perfect tool to characterize different polytypes and polymorphs. As such, it has been possible to distinguish between graphite, graphene and diamond within some of our meteorite samples, and between coesite, stishovite and other quartz polymorphs, present. These critical data provide pressure and temperature information for the meteorite and its parent body.

10:00am - 10:15am

The effect of Co substitution and sample preparation on the Raman spectra of pyrite

Khulan Berkh, Dieter Rammlmair

Federal Institute for Geosciences and Natural Resources, Germany

Effect of Co substitution in pyrite was investigated using a Raman microprobe. Textural appearance of Co-bearing pyrite was visualized by mapping method. The revealed Raman map tightly correlates with a Co distribution map obtained by electron microprobe and µ-energy-dispersive X-ray fluorescence microscope. In addition, a strong influence on the pyrite spectra due to sample preparation was documented. The standard mechanical polishing caused highly broadened modes at upshifted frequencies, which could be avoided by analyzing of sample polished with Ar broad ion beam or non-polished cut sample. However, the effect of Co on pyrite spectra is independent of the sample preparation. Additionally, the Raman method has several advantages over other methods. For instance, It does not require sample preparation, vacuum chamber and wavelength-dispersive system and operates with a laser instead of X-ray. Thus, the Raman method can be used as a possible tool for differentiation of Co-bearing pyrite from pure one.

10:15am - 10:30am

Hyperspectral analysis of lacquer peel profiles as quasi-in-situ analysis for tailings exploration

Wilhelm Nikonow, Dieter Rammlmair

BGR, Germany

Three lacquer peel profiles were prepared from a copper tailings deposit in Central Chile. The peels were taken from two sides at varying depths of the tailings heap. Parallel to that, samples were taken from each layer within the peels for bulk XRF analysis and particle size analysis. The peels were analysed by Hyperspectral Imaging (HSI, VNIR- SWIR, 400 – 2500 nm wavelength) with the Specim SisuRock system and µXRF mapping using M4 Tornado Plus from Bruker for chemical comparison.

The lacquer peel method worked well for sandy tailings with the polyvinyl alcohol Mowiol as glue with a peel size of 50 x 30 cm. All peels were stable, transportable and ready to be measured by HSI after about one day of drying.

The HSI data shows that reflectance of the different material layers within the peels is correlated with particle size data from sieving (Camsizer, Retsch and Sedigraph, Micromeritics). This is important information for a possible reprocessing of copper sulfides, since tailings deposition works as a particle sorting process and, flotation efficiency depends on particle size. Furthermore, endmember classes were extracted from the HSI data using the Pixel Purity Index on lacquer profile 2, which were used to classify the remaining profiles. The HSI classification was registered to the µXRF mappings and the HSI classes were attributed the copper concentration from µXRF. With this information, zones of copper enrichment could be localized using the HSI data in combination with µXRF. This process is also applicable on tailings drill cores.