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Published August 18, 2009 | Published
Journal Article Open

Ultrafast growth of wadsleyite in shock-produced melts and its implications for early solar system impact processes

Abstract

We observed micrometer-sized grains of wadsleyite, a high-pressure phase of (Mg,Fe)_2SiO_4, in the recovery products of a shock experiment. We infer these grains crystallized from shock-generated melt over a time interval of <1 μs, the maximum time over which our experiment reached and sustained pressure sufficient to stabilize this phase. This rapid crystal growth rate (≈1 m/s) suggests that, contrary to the conclusions of previous studies of the occurrence of high-pressure phases in shock-melt veins in strongly shocked meteorites, the growth of high-pressure phases from the melt during shock events is not diffusion-controlled. Another process, such as microturbulent transport, must be active in the crystal growth process. This result implies that the times necessary to crystallize the high-pressure phases in shocked meteorites may correspond to shock pressure durations achieved on impacts between objects 1–5 m in diameter and not, as previously inferred, ≈1–5 km in diameter. These results may also provide another pathway for syntheses, via shock recovery, of some high-value, high-pressure phases.

Additional Information

Copyright ©2009 by the National Academy of Sciences. Contributed by Thomas J. Ahrens, June 17, 2009 (received for review June 20, 2008). Published online before print August 10, 2009, doi: 10.1073/pnas.0905751106 We thank M. Long, E. Gelle, R. Oliver, E. Miura, and G. Rossman for experimental and analytical support. This work was supported by National Science Foundation Grant 0552010, National Nuclear Security Administration Cooperative Agreement DOE-FC88-01NV14049, and National Aeronautics and Space Administration/Goddard Grants NNG04GP57G and NNG04GI07G. N.K. was supported by the California Institute of Technology Summer Undergraduate Research Fellowships program and Mr. and Mrs. Robert E. Anderson. The High Pressure Collaborative Access Team facility was supported by the Department of Energy-Basic Energy Sciences, Department of Energy-National Nuclear Security Administration, National Science Foundation, Department of Defense-Army Tank-Automotive and Armaments Command, and the W. M. Keck Foundation. The U2A beamline is supported by the Consortium for Materials Properties Research in Earth Sciences under National Science Foundation Cooperative Agreement 06-49658, Department of Energy Grant DE-FC52-08NA28554. Advanced Photon Source, Advanced Light Source, and National Synchrotron Light Source are supported by the Department of Energy-Basic Energy Sciences under Contracts W-31-109-Eng-38, DE-AC02–05CH11231, and DE AC02-98CH10886, respectively. Field emission scanning electron microscopy, EBSD, and EMP analyses were carried out at the California Institute of Technology Geological and Planetary Sciences Division Analytical Facility, which is supported in part by National Science Foundation Grant EAR-0318518 and the National Science Foundation Materials Research Science and Engineering Center Program under Grant DMR-00800065. Author contributions: O.T., P.D.A., and T.J.A. designed research; O.T., P.D.A., N.K., C.M., S.S., Z.L., S.F., and N.T. performed research; O.T., P.D.A., and N.K. contributed new reagents/analytic tools; O.T., P.D.A., and N.K. analyzed data; and O.T., P.D.A., N.K., and T.J.A. wrote the paper. The authors declare no conflict of interest.

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August 22, 2023
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