Nebula sulphidation and evidence for migration of 'free floating' refractory metal nuggets revealed by atom probe microscopy

Daly, L., Bland, P. A., Saxey, D. W., Reddy, S. M., Fougerouse, D., Rickard, W. D.A. and Forman, L. V. (2017) Nebula sulphidation and evidence for migration of 'free floating' refractory metal nuggets revealed by atom probe microscopy. Geology, 45(9), pp. 847-850. (doi:10.1130/G39075.1)

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Abstract

Disk models have been proposed that imply particles migrate rapidly in a protoplanetary disk. However, the only physical constraints on these processes from meteorites are observations of refractory inclusions in cometary material from the NASA Stardust mission. Atom probe microscopy (APM) of sub-micrometer refractory metal nuggets (RMNs) contained within a Sc-Zr–rich ultrarefractory inclusion (URI) from the ALH 77307 carbonaceous Ornans (CO) 3.0 meteorite revealed the presence of sulfur at 0.06–1.00 atomic percent (at%) abundances within RMNs. The mineralogical assemblage, petrographic texture, and flat chondrite-normalized highly siderophile element ratios indicate S exposure was unlikely to have occurred after the RMNs were incorporated into the URI. APM analyses suggest these RMNs were likely “free floating” when they were exposed to a S-condensing gas. This requires early, rapid migration of RMNs to cooler regions of the disk to incorporate S and then cycling back to the Ca-Al–rich inclusion (CAI)–forming region for incorporation in the URI, or conditions in the CAI-forming region that promote the incorporation of S into RMNs.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Daly, Dr Luke
Authors: Daly, L., Bland, P. A., Saxey, D. W., Reddy, S. M., Fougerouse, D., Rickard, W. D.A., and Forman, L. V.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Geology
Publisher:Geological Society of America
ISSN:0091-7613
ISSN (Online):1943-2682
Published Online:26 July 2017
Copyright Holders:Copyright © 2017 Geological Society of America
First Published:First published in Geology 45(9):847-850
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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