Time-resolved experimental simulation of pressure-induced amorphization, memory effect and polymorphic phase transformations in plagioclase – implications for meteorite impacts

• Applicant: Professor Dr. Falko Langenhorst
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 571966757

Plagioclase is next to quartz the most diagnostic indicator for natural impact events and has a unique importance for reconstructing the impact record of extraterrestrial bodies (asteroids, Moon, Mars), since quartz is not a component in meteorites. Plagioclase shows an exceptional transformation behaviour under shock compression, which includes solid-state amorphization (formation of so-called maskelynite) and partial recovery to the original crystalline state (memory effect) as well as formation of hollandite- (lingunite, stöfflerite) and unusual defect pyroxene-structured polymorphs (tissintite). The mechanisms behind these transformations are barely understood and can only be deciphered by modern experimental concepts. Previous shock experiments have not been successful in reproducing high-pressure polymorphs and allowed often to only study recovered samples. Here, we pursue therefore a new experimental approach of performing time-resolved in-situ synchrotron X-ray diffraction experiments during rapid compression in a diamond anvil cell at a timescale which is now very close to that of a natural impact. These experiments have recently been tested on single crystal quartz at room temperature and proven to provide significant progress in the field. Here, we propose to apply this technique to oriented single-crystal plagioclase of variable composition, as well, and to extend the temperature range of the diamond anvil experiments up to 1000°C. The microstructures of recovered samples will also be studied by transmission electron microscopy and compared to plagioclase from previous shock experiments of the proponents. Altogether, we expect that the experimental simulation of impact conditions in a realistic pressure-temperature-time frame and the characterization of the microstructures will provide a profound understanding of the origin and formation mechanisms of amorphization and high-pressure polymorphic transitions of plagioclase. The results of the proposed project may also be of great importance for material science, because plagioclase is a model system for pressure-induced amorphization and the memory effect of materials, which provide a distinct route to prepare novel amorphous materials with improved physical properties.

• DFG Programme: Research Grants
• Co-Investigator: Hanns-Peter Liermann, Ph.D.