Other
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992metic..27r.287s&link_type=abstract
Meteoritics, vol. 27, no. 3, volume 27, page 287
Other
Scientific paper
The carbonaceous chondrites (CC) Yamato-82162 (Y-82162) and Yamato-86720 (Y-86720) were found in the bare ice fields of the Yamato mountains in Antarctica. Oxygen isotopic characteristics of these CC are CI-like (Mayeda et al., 1987); however, the details of mineralogy and chemistry are different from those of ordinary CI or CM chondrites. TEM and SEM studies (Akai 1990) showed evidences that the matrix phylosilicates in both meteorites was thermally metamorphosed before their entry to the Earth. They contrast with other CI and CM non-Antarctic CC in which no evidences of thermal metamorphism has been found. In this paper we report on variable temperature Mossbauer spectroscopy measurements on samples of Y-82162 and Y-86720. The transmission Mossbauer spectra were taken through the temperature range 4.2 K to 300 K. The Mossbauer spectra at room temperature (RT) indicate in both meteorites the presence of a magnetically split component and two quadrupole doublets corresponding to paramagnetic Fe^2+ and Fe^3+ compounds. By lowering the temperature from RT up to 25 K the spectra maintain their overall shape and show the same contribution as that of the one obtained at RT. Below 25 K a broadening of the paramagnetic components occurs and a significant transition is observed at 4.2 K. Our results indicate that the proportion of the magnetic phase, due to iron in troilite, in these CC is unusual compared with the non-Antarctic ones. The Mossbauer hyperfine parameters at RT for the Fe^2+ component are in accordance with Fe^2+ in olivines despite the differences observed for both meteorites, probably due to different degrees of thermal metamorphism (Tomeoka et al., 1989). The Fe^3+ doublet in Y-86720 can be attributed to ferrihydrite while in that of Y-82162 can be due to an overlap of different components like Fe and Mg carbonates and Fe-poor magnetite. We thank the National Institute of Polar Research (NIPR) for providing the meteorite samples. References: Mayeda T. K., Clayton R. N., and Yanai K. (1987) Mem. Natl. Inst. Polar Res., Spec. Issue, 46, 144-150. Akai J. (1990) Proc. NIPR Symp. Antarct. Meteorites, 3, 55-68. Tomeoka K., Kojima H., and Yanai K. (1989) Proc. NIPR Symp. Antarct. Meteorites, 2, 55-74.
Azevedo Souza I.
Galvao da Silva E.
Scorzelli R. B.
No associations
LandOfFree
Yamato-82162 and Yamato-86720: A Mossbauer Study does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Yamato-82162 and Yamato-86720: A Mossbauer Study, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Yamato-82162 and Yamato-86720: A Mossbauer Study will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1209907