Remanent magnetization in angrite NWA 4931

Angrites are among the oldest known rocks and may record planetesimal dynamo activity and protoplanetary disk fields in the early solar system. Towards this goal, the natural remanent magnetism and its origin were examined in newly discovered angrite NWA 4931. Measurements were conducted on subsamples cut from various distances along a drilled core sample of the meteorite. The samples were then progressively demagnetized to isolate primary magnetization from contaminant overprints and to calculate paleofield intensity. Dust produced during the subsampling process was analyzed to determine that the mineralogical source of the magnetism was magnetite. Analyses of fusion crusted and adjacent samples showed that the exterior of the meteorite had been contaminated by a collector's hand magnet. However, the interior of the core yielded a pristine record, indicative of a paleointensity strength on the order of 25 [mu]T. These results, in light of magnetic measurements on other angrite samples, are suggestive of a core dynamo active for at least seven million years on the angrite parent body, beginning by 4564 Ma.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Berdahl, James Scott

Advisor dc:contributor.advisor

• Benjamin Weiss.

• Earth, Atmospheric, and Planetary Sciences.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/114342

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/114342