Disorder in martian pyroxenes

• Applicant: Dr. Eveline Weidner
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2003 to 2006
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5417688

The aim of the project is gaining broader knowledge of the prior history of the Mars meteorites through x-ray diffraction experiments. Pyroxene single crystals from sample material of seven Mars meteorites are available for study. We performed first experiments on samples taken from different meteorites, which revealed crystal qualities spanning from well ordered, with sharp Bragg peaks, to heavily textured ones. To our knowledge, these are the first single crystal x-ray diffraction patterns from martian samples recorded. X-ray diffraction methods will be applied to analyse the atomic structure (Bragg scattering), disorder and microstructures (diffuse scattering). Structure analysis of pyroxenes formed under martian conditions has not been attempted so far. It will provide valuable insights into the thermal history of these rocks through the determination of the intracrystalline partitioning coefficient (kD) of Mg-Fe2+. The diffuse scattering can give information on the 'exsolution history' and therefore the petrogenetic conditions. The combination of these methods will help clarify the magmatic and post-magmatic ordering processes. A solid understanding of the temperature and time-dependent ordering will help to differentiate between the initial (pre-impact) state and the subsequent shock deformation and structural transformation.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1115: Mars and the Terrestrial Planets