Magnetic Properties of Avanhandava H4 Meteorite Chondrules
Abstract
The magnetic properties of twenty individual chondrules from Avanhandava chondritic (H4) meteorite fall were studied. Magnetic hysteresis measurements and isothermal remanent magnetization (IRM) acquisition experiments reveal two populations of chondrules with different magnetic properties within the meteorite. The first group shows magnetically hard behavior with coercivities (Hc) ranging between 20 and 60 mT and IRM acquisition curves displaying two distinct coercivity components. The low coercivity component is acquired at fields < 250 mT, while the high coercivity component is acquired mostly between 400 and 1200 mT. This high coercivity component is also apparent in first order reversal curve (FORC) diagrams. The median destructive field (MDF) for samples' saturation isothermal remanent magnetization (SIRM) was ∼ 160 mT. The second group shows magnetically soft behavior, with Hc values below 5 mT and IRM acquisition curves showing only a single low coercivity component acquired at fields < 250 mT. Additionally, there are no high coercivity components observed in the FORC diagrams of these chondrules, and MDFs are generally lower than those of the first group. The natural remanent magnetization (NRM) of the chondrules is weak (∼ 10-2 - 10-1 mAm2/kg). Surprisingly, there is no correlation between the stability of the NRM and the presence of the high coercivity component. The NRM directions of individual chondrules define a random distribution. Alternating field demagnetization reveals one or two stable components. Some chondrules display erratic variations in intensity during demagnetization, which can be caused by the presence of multi-domain grains. While the low coercivity component is likely related to the presence of multi-domain kamacite, the mineralogy of the high coercivity fraction is uncertain. Experiments are underway to identify the magnetic carriers of the two coercivity fractions. This information will be essential for isolating the NRM component held by the high coercivity carriers, which may be related to processes such as original chondrule formation, subsequent coalescence into a parent meteorite body, and/or shock events.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2009
- Bibcode:
- 2009AGUSMGP11D..01K
- Keywords:
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- 1519 Magnetic mineralogy and petrology;
- 1540 Rock and mineral magnetism;
- 6240 Meteorites and tektites (1028;
- 3662)