¹Keita Nagaki, ²Toshihiko Kadono, ¹Tatsuhiro Sakaiya, ¹Tadashi Kondo, ³Kosuke Kurosawa, ⁴Yoichiro Hironaka, ⁵Keisuke Shigemori, ⁵Masahiko Arakawa
¹Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
²School of Medicine, University of Occupational and Environmental Health, Yahata, Kitakyushu, Japan
³Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba, Japan
⁴Institute of Laser Engineering, Osaka University, Suita, Osaka, Japan
⁵Graduate School of Science, Kobe University, Nada, Kobe, Japan

We carried out laser shock experiments and wholly recovered shocked olivine and quartz samples. We investigated the petrographic features based on optical micrographs of sliced samples and found that each recovered sample comprises three regions, I (optically dark), II (opaque), and III (transparent). Scanning electron microscopy combined with electron backscattered diffraction shows that there are no crystal features in the region I; the materials in the region I have once melted. Moreover, numerical calculations performed with the iSALE shock physics code suggest that the boundary between regions II and III corresponds to Hugoniot elastic limit (HEL). Thus, we succeeded in the recovery of the entire shocked samples experienced over a wide range of pressures from HEL (~10 GPa) to melting pressure (~100 GPa) in a hierarchical order.

Reference
Nagaki K, Kadono T, SakaiyaT, Kondo T, Kurosawa K, Hironaka Y, Shigemori K, Arakawa M (2016) Recovery of entire shocked samples in a range of pressure from ~100 GPa to Hugoniot elastic limit. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12654]
Published by arrangement with John Wiley & Sons

¹Neva A. Fowler-Gerace, ^1,2Kimberly T. Tait, ³Desmond E. Moser, ³Ivan Barker,⁴Bob Y. Tian
¹Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada
²Department of Natural History, Mineralogy, Royal Ontario Museum, Toronto, Ontario, Canada
³Department of Earth Sciences, Western University, London, Ontario, Canada
⁴Department of Physics, University of Toronto, Toronto, Ontario, Canada

The mechanism by which olivine grains became embedded within iron-nickel alloy in pallasite meteorites continues to be a matter of scientific debate. Geochemical and textural observations have failed to fully elucidate the origin and history of the olivine crystals; however, little research attention has been devoted to their crystallographic orientations within the metal matrix. Using electron backscatter diffraction, we have collected crystallographic orientation data for 296 crystals within ∼65 cm2 sample surface from Springwater. Though no global crystallographic preferred orientation exists, very low misorientations are observed among [100] axes of olivine crystals within specific texturally defined domains. Combined with a thorough characterization of large-scale Springwater textures, the definitively nonrandom spatial distribution of olivine orientations provides clues regarding the nature of the olivine’s initial formation environment as well as the sequence of events subsequent to metal incorporation.

Reference
Fowler-Gerace NA, Tait KT, Moser DE, Barker I,Tian BY (2016) Aligned olivine in the Springwater pallasite. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12650]
Published by arrangement with John Wiley & Sons