Stony meteorite characterization by non‐destructive measurement of magnetic properties

Abstract

All appendix tables for this article are available online at http://meteoritics.org.Abstract-Four parameters of low-field magnetic susceptibility (bulk value, frequency dependence, degree of anisotropy, and ellipsoid shape) have been determined for 321 stony meteorites from the National Collection of Canada. These parameters provide a basis for rapid, non-destructive, and accurate meteorite classification as each meteorite class tends to have a distinct range of values.Chondrites show a clear trend of increasing bulk susceptibility from LL to L to H to E within the 3.6 to 5.6 logχ (in 10 −9 m 3 /kg) range, reflecting increasing Fe-Ni metal and Fe-Ni sulfide content. Achondrite values range in logχ from 2.4 to 4.7 and primitive achondrites from 4.2 to 5.7. Frequency dependence is observed, using 19,000 Hz and 825 Hz, with variations in strength among meteorite classes and individual specimen dependence ranging from 1-25.6%. Degrees of anisotropy range from 1 to 53% with both oblate and prolate ellipsoids present. The aubrite class is marked by high degrees of anisotropy, low bulk magnetic susceptibility, and prolate fabric. Camel Donga is set apart from other eucrites, marked by higher bulk susceptibility, degree of anisotropy, and magnitude of oblate ellipsoid shape. The Shergotty, Nakhla, and Chassigny (SNC) meteorites show subclass distinction using frequency dependence and Chassigny is set apart with a relatively strong oblate fabric. The presence of both strong oblate and prolate fabrics among and within meteorite classes of chondritic and achondritic material points to a complex, multi-mechanism origin for anisotropy, more so than previously thought, and likely dominated by impact processes in the later stages of stony parent body formation.

The Cali meteorite fall: A new H/L ordinary chondrite

“…The measured magnetic susceptibility value for Cali of 5.11 is also intermediate between those of L chondrite falls, 4.87 ± 0.10, and H chondrite falls, 5.31 ± 0.12 (Rochette et al 2003;Smith et al 2006). Again, the value in Cali is very similar to those of Tieschitz (4.97) and Bremervörde (4.98) (Rochette et al 2003).…”

Magnetic classification of stony meteorites: 3. Achondrites

“…List of meteorite collections entered in the database (in chronological order of measurements, and with the same numbering as in Rochette et al 2003), as well as number of measured specimens and the measurement instruments used. 1-5, 6-7, 17, 22, 31, and 33 were previously and partly published in Rochette et al (2001a), Thero et al (1993), Smith et al (2006), Kohout et al (2008), and Lin et al (2008) equivalent, for the Helsinki data) was used, allowing samples up to a mass of 450 g to be measured, although coil saturation may be already reached for 50-100 g highly magnetic samples. The high homogeneity of the solenoid coil internal field allowed us to obtain reliable results on samples with anisometric shape (fragments, slice, full stones).…”

“…This instrument is less precise than the KLY-2 but reasonably well cross-calibrated with the KLY-2 . The Ottawa collection has been measured using a SI-2B bridge (from Sapphire; Smith et al 2006). Cross calibration with the KLY-2 is not specifically provided, but correlating the measurements from the CEREGE and Canadian databases on the same meteorite (Smith et al 2006) show a good one to one correspondence.…”

“…After that publication, the new samples investigated have been in chronologic order, from the collections of Chicago (Field Museum), Albuquerque (IOM), London (NHM), Moscow (Vernadsky Institute), Rio de Janeiro (Museu Nacional), Tokyo (NIPR), Vienna (NHM), Houston (JSC), Washington (Smithsonian Institution), New York (AMNH), Zurich (ETH), Bern (NHM), Christchurch (Canterbury Museum), Los Angeles (UCLA), Lyon (ENSL), Tempe (ASU), Paris (UPMC), Berlin (Humboldt University), Edinburgh (National Museums Scotland), Cambridge (Harvard Mineralogical Museum), as well as various private collections. Furthermore, the Ottawa collection (Smith et al 2006), the Berlin and four other European collections , and the Shanghai Antarctic meteorite collection (Lin et el. 2008) have been investigated independently, and the data merged for this publication with the CEREGE database.…”

The Puerto Lápice eucrite

“…The hysteresis loops for all of the Puerto Lápice specimens were very similar. Specific magnetic susceptibility, χ, measured at a low field (0.5 mT) on the three samples gave a logχ of 2.6 ± 0.1 (in 10 −9 m 3 kg −1 ), typical of other eucrites, 2.8 ± 0.2 (Consolmagno et al 2006;Smith et al 2006). These low magnetic susceptibility values are due to depletion in the siderophile elements of eucrites as a result of being the product of partial melting of differentiated parent bodies; eucrites are dominated by Fe-Mg silicates, which are paramagnetic minerals.…”