¹Christopher M. Wright, ^1,2Tho Do Duy, ¹Warrick Lawson
¹School of Physical, Environmental and Mathematical Sciences, UNSW Canberra, PO Box 7916, Canberra BC 2610, Australia
²Department of Physics, International University – Vietnam National University HCM, Block 6, Linh Trung, Thu Duc, Ho Chi Minh City, Viet Nam

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Reference
Wright CM, Duy TD, Lawson W (2016) Absorption at 11 μm in the interstellar medium and embedded sources: evidence for crystalline silicates. Monthly Notices of the Royal Astronomical Society 457, 1593-1625.
Link to Article [doi:10.1093/mnras/stw041]

^1,2F. C. Pignatale, ²Kurt Liffman, ²Sarah T. Maddison, ³Geoffrey Brooks
¹Université de Lyon, Lyon, F-69003, France; Université Lyon 1, Observatoire de Lyon, 9 avenue Charles André, Saint-Genis Laval, F-69230, France CNRS, UMR 5574, Centre de Recherche Astrophysique de Lyon; Ecole Normale Supérieure de Lyon, F-69007, France
²Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122, Australia
³FSET, Swinburne University of Technology, Hawthorn, VIC 3122, Australia

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Pignatale FC, Liffman K, Maddison ST, Brooks G (2016) 2D condensation model for the inner Solar Nebula: an enstatite-rich environment. Monthly Notices of the Royal Astronomical Society 457, 1359-1370
Link to Article [doi:10.1093/mnras/stv3003]

¹Jangmi Han, ¹Adrian J. Brearley
¹Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA

We have carried out a FIB/TEM study of refractory CAI-like objects in one AOA from the ALHA77307 CO3.0 chondrite. The CAI-like objects in the AOA consist of a zoned sequence with a spinel-rich core through an intergrowth layer of spinel and Al-Ti-rich diopside to a diopside rim. The spinel-rich core consists of polycrystalline aggregates of spinel and ±minor melilite showing equilibrated grain boundary textures. The intergrowth layer contains fine-grained diopside and spinel with minor anorthite with highly curved and embayed grain boundaries. The diopside rim consists of polycrystalline aggregates of diopside. The compositions of pyroxene change significantly outward from Al-Ti-rich diopside in contact with the spinel-rich core to Al-Ti-poor diopside next to the surrounding olivine of the AOA. Overall microstructural and chemical characteristics suggest that the spinel-rich core formed under equilibrium conditions whereas the intergrowth layer is the result of reactions that occurred under conditions that departed significantly from equilibrium. The remarkable changes in formation conditions of the CAI-like objects may have been achieved by transport and injection of refractory objects into a region of a partially-condensed, Ca,Ti-saturated gas which reacted with spinel and melilite to form Al-Ti-rich diopside.

Crystallographically-oriented TiO2 nanoparticles decorate the grain boundaries between spinel grains and between spinel and Al-Ti-rich diopside grains. During the disequilibrium back-reaction of spinel with a partially-condensed, Ca,Ti-saturated gas, metastable TiO2 nanoparticles may have condensed by an epitaxial nucleation mechanism and grown on the surface of spinel. These TiO2 nanoparticles are disordered intergrowths of the two TiO2 polymorphs, anatase and rutile. These nanoparticles are inferred to have nucleated as anatase that underwent partial transformation into rutile. The local presence of the TiO2 nanoparticles and intergrowth of anatase and rutile imply that the disequilibrium back-reaction of spinel with the gas occurred on a short timescale, i.e., minutes to hours at maximum.

Reference
Han J, Brearley AJ (2016) Microstructural constraints on complex thermal histories of refractory cai-like objects in an amoeboid olivine aggregate from the ALHA77307 CO3.0 chondrite. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2016.04.011]
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