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Moderate velocity oblique impact sliding: Production of shocked meteorite textures and palaeomagnetically important metallic spherules in planetary regoliths

Potter, David K. and Ahrens, Thomas J. (2013) Moderate velocity oblique impact sliding: Production of shocked meteorite textures and palaeomagnetically important metallic spherules in planetary regoliths. Meteoritics and Planetary Science, 48 (4). pp. 656-664. ISSN 1086-9379. doi:10.1111/maps.12081. https://resolver.caltech.edu/CaltechAUTHORS:20130531-104225510

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Abstract

We detail the production of metallic spherules in laboratory oblique shock impact experiments, and their applicability (1) to textures in a partly shock-melted chondritic meteorite and (2) to the occurrence of palaeomagnetically important fine iron or iron alloy particles in the lunar regolith. Samples recovered from 29–44 GPa, 800 ns, experiments revealed melting and textures reminiscent of metallic spherules in the Yanzhuang H-chondrite, including “dumbbell” forms and other more complex morphologies. Our experiments demonstrate that metallic spherules can be produced via oblique impact sliding at lower velocities (1.85 km s^(−1)) than are generally assumed in previous work associated with bulk-shock melting, and that oblique impact sliding is a viable mechanism for producing spherules in shock-induced veins in moderately shocked meteorites. Significantly, our experiments also produced fine metallic (iron alloy) spherules within the theoretical narrow size range (a few tens of nanometers for slightly ellipsoidal particles) for stable single-domain (SSD) particles, which are the most important palaeomagnetically, since they can record lunar and planetary magnetic fields over geological time periods. The experiments also produced spherules consistent with superparamagnetic (SP) and multidomain (MD) particle sizes. The fine SSD and SP particles on the lunar surface are currently thought to have been formed predominantly by space weathering processes. Our experiments suggest that oblique shock impact sliding may be a further means of producing the SSD and SP iron or iron alloy particles observed in the lunar regolith, and which are likely to occur in the regoliths of Mercury and other planetary bodies.


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http://dx.doi.org/10.1111/maps.12081 DOIUNSPECIFIED
http://onlinelibrary.wiley.com/doi/10.1111/maps.12081/abstractPublisherUNSPECIFIED
Additional Information:© 2013 The Meteoritical Society. Received 17 December 2011; revision accepted 17 December 2012. Article first published online: 15 Mar. 2013. Research supported by NASA. We thank Meteoritics & Planetary Science, © 1992 by the Meteoritical Society, for permission to reproduce fig. 1 of Begemann et al. (1992). We thank associate editor Randy Korotev and the two reviewers, Philippe Claeys and an anonymous reviewer, for their constructive comments which improved this manuscript.
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NASAUNSPECIFIED
Issue or Number:4
DOI:10.1111/maps.12081
Record Number:CaltechAUTHORS:20130531-104225510
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130531-104225510
Official Citation:Potter, D. K. and Ahrens, T. J. (2013), Moderate velocity oblique impact sliding: Production of shocked meteorite textures and palaeomagnetically important metallic spherules in planetary regoliths. Meteoritics & Planetary Science, 48: 656–664. doi: 10.1111/maps.12081
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38730
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Jun 2013 15:14
Last Modified:09 Nov 2021 23:39

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