Date: 16:30-, Tuesday, 12 June 2018
Place: 3F, Lecture room, Main Chemistry Build.
講演者：Konstantin Litasov（Novosibirsk State University）
Title: High-pressure minerals and microstructures in meteorites and their relation to phase diagrams in dynamic and static high-pressure experiments
I provide brief description of status of research in high-pressure mineralogy of meteorites and emphasize following current issues. Electron microscopy and focused ion beams may be used more generally to unravel the mineralogy of shocked rocks at the nanoscale. Each tiny mineral reflects part of the (P,T,t) history of the shock. Mineralogy and petrology should be introduced into numerical models of crater formation to enable forward prediction of the (P,T) metamorphic maps of crater rocks and ejecta blankets. Wider spherically converging shock experiments should be performed with careful identification of run products. Supercomputers can be used to study, through molecular dynamics or other means, the physics of wave propagation in heterogeneous media at a scale of a few nanometers to a few micrometers. Kinetic calculations and experiments should be introduced systematically to estimate process duration during shock metamorphism.
The case studies include identification of broad spectra of high-pressure phases in L6 chondrites from the meteorite collection of Russian Academy of Sciences. The studied chondrites contain abundant shock-melt veins (SMVs). Olivine close to the veins is transformed to wadsleyite and ringwoodite, whereas inside the SMVs it is totally replaced by wadsleyite-ringwoodite aggregates. Plagioclase grains are transformed to jadeite and linguinite. Some of them are rimmed by majorite. Orthopyroxene is transformed to majorite, akimotoite and presumably bridgmanite. However, detailed identification of bridgmanite is not clear. These phenomena are related to solid-state transformation. The SMV presented by fine-grained majorite, ringwoodite and metallic phases. These minerals are formed from quenched shock melt. Apatite is replaced by fine-grained aggregates of tuite with partial melting. Broad range of high-pressure minerals indicates heavy shocked conditions for studied meteorites with preserved post-shock pressures above 20-25 GPa. Post-shock temperature conditions were highly heterogeneous. SMV minerals formed from melt at temperatures >2500 K. Akimotoite formed by cooling of majorite or bridgmanite at relatively low-temperatures of <2000 K.