Journal
GEOCHIMICA ET COSMOCHIMICA ACTA
Volume 100, Issue -, Pages 116-157Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2012.09.052
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Funding
- Graduate University of Advanced Studies in Japan
- NIPR publication subsidy
- Grants-in-Aid for Scientific Research [23340165] Funding Source: KAKEN
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We analyzed 91 relict grain-bearing micrometeorites (MMs) from two Antarctic collections: Tottuki icefield and the South Pole Water Well. To determine if the MMs are related to specific meteorite groups, we analyzed their relict olivines and low-Ca pyroxenes and compared them with olivines and pyroxenes we analyzed in various meteorites: an enstatite chondrite (EH3), a suite of carbonaceous chondrites (CM2, CR2, CV3.2, CO3.0, and CO3.2), an ungrouped carbonaceous chondrite (Tagish Lake), various unequilibrated ordinary chondrites (H3.2, L3.7, LL3.0, LL3.2, LL3.3), and a Rumuruti chondrite (R3.5/5 breccia). Mg-rich olivines are the most common relict mineral in the MMs studied (42%), followed by Fe-rich olivines (16%), Mg-rich low-Ca pyroxenes (15%), and MMs containing both Mg-rich olivine and low-Ca pyroxene (13%). If one corrects for the effects of atmospheric heating on the proportion of olivines and pyroxenes, then 59% of MMs are related to carbonaceous chondrites, 22% to ordinary chondrites (mostly unequilibrated, UOCs), and 19% to a high-Mn group. Results of textural observations suggest that four MMs resemble chondrules from CO3 carbonaceous chondrites, and one is a shock-melted H chondrite. MMs from the high-Mn group appear to have crystallized from a melt and might be fragments of chondrule-like objects similar to those found in comet 81P/Wild 2. (C) 2012 Elsevier Ltd. All rights reserved.
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