TY - JOUR
T1 - Mineralogy of fine-grained matrix, fine-grained rim, chondrule rim, and altered mesostasis of a chondrule in Asuka 12169, one of the least altered CM chondrites
AU - Noguchi, Takaaki
AU - Yasutake, Masahiro
AU - Tsuchiyama, Akira
AU - Miyake, Akira
AU - Kimura, Makoto
AU - Yamaguchi, Akira
AU - Imae, Naoya
AU - Uesugi, Kentaro
AU - Takeuchi, Akihisa
N1 - Funding Information:
The polished chip of A 12169 was loaned from the National Institute of Polar Research. This work was supported by NIPR Project fund KP307 and General Collaboration Project 2–19. T. N. was supported by a JSPS KAKENHI Grant Number 19H00725 . A. T. was supported by JSPS KAKENHI Grant Numbers 15H05695 and 20H00205 and by Chinese Academy of Sciences International Fellowship for Visiting Scientists Grant No. 2019VCA0004 . K. U. was supported by a JSPS KAKENHI Grant Number JP16H0634 8. The SR-XCT experiments at SPring-8 in this study were conducted under the proposal No. 2019B0166.
Publisher Copyright:
© 2021 Elsevier B.V. and NIPR
PY - 2021/9
Y1 - 2021/9
N2 - Mineralogy of fine-grained matrix (FGM), fine-grained rim (FGR), chondrule rim, and altered mesostasis of a chondrule from the Asuka (A) 12169 CM3.0 chondrite was investigated by field emission scanning electron microscopy (FE-SEM), synchrotron radiation-based X-ray nano-tomography (SR-XCT), and transmission electron microscopy (TEM). SR-XCT and TEM observations revealed that both FGM and FGR contain abundant amorphous silicate embedding nano-inclusions (most are Fe–Ni sulfide). Although the amorphous silicate is more or less hydrated based on the analysis of the X-ray linear attenuation coefficients in SR-XCT, there are no areas filled by abundant phyllosilicate even in three dimensions. However, FGM and FGR contain ~2-10 μm-sized aggregates composed of tochilinite, nano-inclusions of possible magnetite, and poorly crystalline serpentine without sharp boundaries with the surroundings. It is unlikely that the heterogeneity resulted from brecciation and mixing of materials that experienced different degrees of aqueous alteration, but more likely from a very early stage of aqueous alteration that proceeded heterogeneously depending on locally different chemistry. Chondrule mesostasis near the surface of a chondrule was altered to saponite with tochilinite-rich aggregates. These observations indicate that the degree aqueous alteration of A 12169 is very low and that it is comparable with that of Acfer 094, ALH 77307, and the least altered areas of Paris.
AB - Mineralogy of fine-grained matrix (FGM), fine-grained rim (FGR), chondrule rim, and altered mesostasis of a chondrule from the Asuka (A) 12169 CM3.0 chondrite was investigated by field emission scanning electron microscopy (FE-SEM), synchrotron radiation-based X-ray nano-tomography (SR-XCT), and transmission electron microscopy (TEM). SR-XCT and TEM observations revealed that both FGM and FGR contain abundant amorphous silicate embedding nano-inclusions (most are Fe–Ni sulfide). Although the amorphous silicate is more or less hydrated based on the analysis of the X-ray linear attenuation coefficients in SR-XCT, there are no areas filled by abundant phyllosilicate even in three dimensions. However, FGM and FGR contain ~2-10 μm-sized aggregates composed of tochilinite, nano-inclusions of possible magnetite, and poorly crystalline serpentine without sharp boundaries with the surroundings. It is unlikely that the heterogeneity resulted from brecciation and mixing of materials that experienced different degrees of aqueous alteration, but more likely from a very early stage of aqueous alteration that proceeded heterogeneously depending on locally different chemistry. Chondrule mesostasis near the surface of a chondrule was altered to saponite with tochilinite-rich aggregates. These observations indicate that the degree aqueous alteration of A 12169 is very low and that it is comparable with that of Acfer 094, ALH 77307, and the least altered areas of Paris.
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U2 - 10.1016/j.polar.2021.100727
DO - 10.1016/j.polar.2021.100727
M3 - Article
AN - SCOPUS:85110166044
VL - 29
JO - Polar Science
JF - Polar Science
SN - 1873-9652
M1 - 100727
ER -