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Prof. Dr. Leander Franz

Department of Environmental Sciences
Profiles & Affiliations

Wissenschaftliche Forschungsinteressen (Research focus)

Forschungsinteressen: Druck-Temperatur-Zeit-Pfade metamorpher Gesteine, Petrologie des Erdmatels, Edelsteinforschung


Research focus: PT-t paths of metamorphic rocks, mantle petrology, gemstones.

Selected Publications

Nimis, Paolo, Zanetti, Alberto, & Franz, Leander. (2024). A revision of the Ni-in-garnet geothermometer with special regard to its pressure dependence [Forschungsartikel]. Lithos, 468. https://doi.org/10.1016/j.lithos.2024.107513

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Hess, Thomas, Mullis, Josef, & Franz, Leander. (2023). The first petrographic characterisation of a prehistoric rock crystal mine in the Swiss Alps. Scientific Reports, 13:23107, 11. https://doi.org/10.1038/s41598-023-48914-8

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Min, Myo., Ratschbacher, Lothar, Franz, Leander, Hacker, Bradley R., Enkelmann, Eva, Toreno, Eko Yoan, Härtel, Birk, Schurr, Bernd, Tichomirowa, Marion, & Pfänder, Jörg A. (2022). India (Tethyan Himalaya Series) in central Myanmar: implications for the evolution of the Eastern Himalayan Syntaxis and the Sagaing transform-fault system. Geophysical Research Letters, 49(12), e2022GL099140. https://doi.org/10.1029/2022gl099140

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Phyo, Myint M., Franz, Leander, Romer, Rolf L., de Capitani, Christian, Balmer, Walter A., & Krzemnicki, Michael S. (2022). Petrology, geothermobarometry and geochemistry of granulite facies wall rocks and hosting gneiss of gemstone deposits from the Mogok area (Myanmar). Journal of Asian Earth Sciences: X, 9, 100132. https://doi.org/10.1016/j.jaesx.2022.100132

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Franz, Leander, Romer, Rolf L., & de Capitani, Christian. (2013). Protoliths and phase petrology of whiteschists. Contributions to Mineralogy and Petrology, 166(1), 255–274. https://doi.org/10.1007/s00410-013-0874-5

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Selected Projects & Collaborations

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Raman-Spektroskopie für anorganische und organische Feststoffanalyse, Geothermobarometrie und Flüssigkeits- einschlussuntersuchungen.

Research Project  | 1 Project Members

The analysis of inorganic and organic solid matter in natural scientific research is commonly performed with a number of devices based on X-ray techniques (XRD, XRF), inductively coupled plasma mass spectrometry (ICP) or electron microprobe (EMP). Most of these techniques yield very precise chemical analyses of the investigated specimen but do not reveal any information on its properties (e.g., crystallinity and crystal system, organic group etc.). Furthermore, the majority of these techniques are considerably limited concerning their spatial resolution or the type of elements, which can be analyzed. The electron microprobe, which is the only instrument performing a non-destructive analysis of very small particles (< 5 ?m), is either limited to elements heavier than oxygen and not at all able to analyze organic matter. A high-tech approach to identify inorganic and organic phases is Raman spectroscopy, which allows non-destructive analysis based on spectra resulting from inelastic scattering of the sample molecules activated by monochromatic laser light. Raman spectroscopy can be applied to solid, liquid and gaseous phases and thus covers the whole range of matter in geosciences as well as soil biology and archeology. We therefore decided to purchase a Bruker SENTERRA confocal Raman spectrometer, which works with multiple wavelengths (two lasers with 532 nm and 785 nm) and has a very high spectral resolution of <3cm-1 and a spatial resolution of 1 ?m. Five groups of the Department of Environmental Sciences of the University of Basel take part in this project. 1.) The Petrology/Mineralogy Group (Leander Franz & Christian de Capitani) will use the Raman spectrometer in the framework of the existing SNF project NF-200021-113399/1/1 (Multiple high- and ultrahigh-pressure orogenies in the Qinling Mountains: boundary conditions permitting their formation and exhumation) for phase identification and geothermobarometry. 2.) The Fluid Inclusion Group (Josef Mullis) will identify the chemical character of the fluid inclusions in metamorphic minerals (blueschist facies and greenschist facies minerals from veins). 3.) The Fission Track Group (Alexandre Kounov and Meinert Rahn) plan to study the extent of metamictization within minerals containing fission tracks in order to further develop Raman-based techniques in low-temperature thermochronology. 4.) The Soil Science and Terrestrial Biogeochemistry Group (Christine Alewell & Franz Conen) will use the Raman spectrometer for identification and mapping of inorganic components and organic matter in soils. 5.) The Archaeology Group (Jörg Schibler and Philippe Rentzel) will use the Raman spectrometer for archaeometrical studies in the framework of analysis of ceramics, determination of pigments and studies on the provenance of prehistoric raw materials. A sixth group from the Geosciences Department of the Natural History Museum Basel (André Puschnig) would benefit from the analytical possibilities of the Raman spectrometer to perform non-destructive identifications of numerous valuable samples. Finally, the Raman spectrometer will also serve as a teaching tool for master and PhD students. Quick access to and the knowledge about the possibilities of such modern analytical equipment is an integral part of scientific education as well as research. Hence, this equipment also fulfills the needs of an innovative curriculum at the Department of Environmental Sciences at the University of Basel.

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Multiple high- and ultrahigh-pressure orogenies in the Qinling Mountains: boundary conditions permitting their formation and exhumation

Research Project  | 1 Project Members

In the last years, numerous occurrences of ultrahigh-pressure (UHP) metamorphic rocks have been found all over the world. In most cases, these rocks experienced a subduction due to a continental collision and were rapidly transported to and exchumed from a depth of more than 100 km, which means that they reached the stability field of coesite and sometimes diamond. Understanding how ultrahigh-pressure metamorphic rocks form and exhume is an outstanding tectonometamorphic question, as it highlights processes dealing with the exchange of material between the crust and mantle, the formation and destruction of mountain belts, the composition of deep continental crust, and tectonic plate motions. The huge and well-exposed UHP terranes of the Qinling mountains in central eastern China allow case studies in natural laboratories, i.e. orogen-scale geologic work, yielding crucial parameters like HP/UHP phase petrology and fluid studies within continental crust in mantle depth. Furthermore, information is supplied on plate geometry, plate-tectonic framework, and detailed structural research that provides the geometry and the kinematics of exhumation (the subduction history has remained mostly enigmatic) and the rheology of deformation. This project, building on earlier work in the archetype of UHP orogens, the Dabie-Sulu belt, will (i) establish the value of four recently discovered and/or enigmatic eclogite facies (HP and UHP) events in the Qinling mountain belt for research on HP-UHP orogeny; (ii) set up the physico-chemical and structural boundary conditions that permitted formation and exhumation of these rocks; and (iii) make first-order contributions to the understanding of the centrepiece of Chinese geology, the Qinling orogenic collage. Recent meetings and thematic volumes on UHP research, to which we contributed, highlighted hypotheses that need long-term study by the tectonics community; these are among others: - How do UHP rocks form and exhume? - Which plate-tectonic processes and boundary conditions permit/prohibit formation and exhumation of UHP rocks? - What are the rates that transfer continental crust into mantle and vice versa? - Do UHP terranes constitute a significant portion of the continental lower crust? To solve such a complex problem, an inter-disciplinary project with international scientific partners has been enforced. A first application on this topic was already granted to Lothar Ratschbacher (Freiberg University of Mining and Technology/Saxony) by the German Research Community (Deutsche Forschungsgemeinschaft DFG) in December of 2006. The working group in Freiberg will mainly concentrate on structural geology and - in co-operation with our U.S. American partners Bradley Hacker (UC Santa Barbara) and Mike McWilliams (Stanford University) - on geochronology. The Swiss working consist of Leander Franz (field petrology, PTtd-paths), Christian de Capitani (theoretical petrology, thermodynamics) and Josef Mullis (fluid inclusions). Two PhD students (Thomas Bader from Basel and Carsten Weise from Freiberg) will unravel the tectonometamorphic evolution of the Qinling mountains combining state of the art methods of petrology, fluid inclusion studies, structural geology and geochronology.