Место издания:Казанский Федеральный Университет Казанский Федеральный Университет
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Аннотация:The Chelyabinsk meteorite (the fall of February 15, 2013; Russia) is a LL5 ordinary chondrite. Numerous (thousands) stones fell as a shower to the south and the SW of Chelyabinsk. The stones consist of two intermixed lithologies (light and dark). Light variety (LV) has a typical chondritic texture and shock stage S4 (~30 GPa). Dark variety (DV) consists of blackened chondrite fragments embedded in a fine-grained matrix. We investigated the magnetic properties of the meteorite stones (in 10-1073K temperature range) collected immediately after the fall by the expedition of the Vernadsky Institute, Moscow.
The mean logχ0 (where χ0 is low-field magnetic susceptibility) is 4.57±0.09 (s.d.) (n=135) for the LV and 4.65±0.09 (s.d.) (n=39) (×10-9 m3/kg) for the DV, indicating that the DV is richer in metal than the LV. According to [1], Chelyabinsk is three times more magnetic than the average LL5 fall, but similar to other metal-rich LL5 (e.g., Paragould, Aldsworth, Bawku, Richmond), as well as L/LL chondrites (e.g., Glanerbrug, Knyahinya, Qidong). The estimation of metal content from saturation magnetization values gives 3.7 wt.% for the LV and 4.1 wt.% for the DV whereas the estimation from χ0 yields overestimated contents. Thermomagnetic analyses up to 800°C identify the main magnetic carriers at room temperature (T0) and above as taenite and kamacite (no tetrataenite found), in accordance with mineralogical data. Additional magnetic analyses [2] confirm the absence of tetrataenite and show that metal grains are primarily multidomain and magnetically soft (coercivity Bc<2 mT and coercivity of remanence Bcr<23 mT) at T0. However, at temperatures <75 K, the magnetic remanence of the Chelyabinsk chondrite is dominated by high coercivity chromite with much higher Bcr (606 mT for the LV and 157 mT for the DV). These results are consistent with previously published data on ordinary chondrites [3]. Acknowledgments: This research was funded by a U.S. National Science Foundation IRM Visiting Fellowship.
References: [1] Rochette P. et al. 2003. Meteoritics & Planetary Science 38: 251-268. [2] Bezaeva N.S. et al. 2013. Geochemistry International 51(7): 568-574. [3] Gattacceca J. et al. 2011. Geophysical Research Letters 38: L10203.