TY - JOUR
T1 - The effects of secondary processing in the unique carbonaceous chondrite Miller Range 07687
AU - Haenecour, Pierre
AU - Floss, Christine
AU - Brearley, Adrian J.
AU - Zega, Thomas J.
N1 - Funding Information: A draft of this manuscript was originally written by Christine Floss. This work was support by NASA grants NNX14AG25G and 80NSSV17K0592 (CF), NNX11AK51G and NNX15AD28G (AJB), and NNX15AD94G (TJZ). We also thank Jane Howe and Hitachi High Technologies Co. for help and support with the SU9000 measurements. This manuscript was significantly improved by helpful suggestions from M. Bose, A. King, an anonymous reviewer, and guest associate editor L. R. Nittler. TEM and FIB analyses for grain 5d1-6o1 were carried out at the University of Arizona Kuiper Materials Imaging and Characterization Facility (NSF Grant 1531243 and NASA Grants NNX15AJ22G and NNX12AL47G). US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center. Funding Information: A draft of this manuscript was originally written by Christine Floss. This work was support by NASA grants NNX14AG25G and 80NSSV17K0592 (CF), NNX11AK51G and NNX15AD28G (AJB), and NNX15AD94G (TJZ). We also thank Jane Howe and Hitachi High Technologies Co. for help and support with the SU9000 measurements. This manuscript was significantly improved by helpful suggestions from M. Bose, A. King, an anonymous reviewer, and guest associate editor L. R. Nittler. TEM and FIB analyses for grain 5d1‐6o1 were carried out at the University of Arizona Kuiper Materials Imaging and Characterization Facility (NSF Grant 1531243 and NASA Grants NNX15AJ22G and NNX12AL47G). US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center. Publisher Copyright: © The Meteoritical Society, 2020.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - Our detailed mineralogical, elemental, and isotopic study of the Miller Range (MIL) 07687 meteorite showed that, although this meteorite has affinities to CO chondrites, it also exhibits sufficient differences to warrant classification as an ungrouped carbonaceous chondrite. The most notable feature of MIL 07687 is the presence of two distinct matrix lithologies that result from highly localized aqueous alteration. One of these lithologies is Fe-rich and exhibits evidence for interaction with water, including the presence of fibrous (dendritic) ferrihydrite. The other lithology, which is Fe-poor, appears to represent relatively unaltered protolith material. MIL 07687 has presolar grain abundances consistent with those observed in other modestly altered carbonaceous chondrites: the overall abundance of O-rich presolar grains is 137 ± 3 ppm and the overall abundance of SiC grains is 71 ± 11 ppm. However, there is a large difference in the observed O-rich and SiC grain number densities between altered and unaltered areas, reflecting partial destruction of presolar grains (both O- and C-rich grains) due to the aqueous alteration experienced by MIL 07687 under highly oxidizing conditions. Detailed coordinated NanoSIMS-TEM analysis of a large hotspot composed of an isotopically normal core surrounded by a rim composed of 17O-rich grains is consistent with either original condensation of the core and surrounding grains in the same parent AGB star, or with grain accretion in the ISM or solar nebula.
AB - Our detailed mineralogical, elemental, and isotopic study of the Miller Range (MIL) 07687 meteorite showed that, although this meteorite has affinities to CO chondrites, it also exhibits sufficient differences to warrant classification as an ungrouped carbonaceous chondrite. The most notable feature of MIL 07687 is the presence of two distinct matrix lithologies that result from highly localized aqueous alteration. One of these lithologies is Fe-rich and exhibits evidence for interaction with water, including the presence of fibrous (dendritic) ferrihydrite. The other lithology, which is Fe-poor, appears to represent relatively unaltered protolith material. MIL 07687 has presolar grain abundances consistent with those observed in other modestly altered carbonaceous chondrites: the overall abundance of O-rich presolar grains is 137 ± 3 ppm and the overall abundance of SiC grains is 71 ± 11 ppm. However, there is a large difference in the observed O-rich and SiC grain number densities between altered and unaltered areas, reflecting partial destruction of presolar grains (both O- and C-rich grains) due to the aqueous alteration experienced by MIL 07687 under highly oxidizing conditions. Detailed coordinated NanoSIMS-TEM analysis of a large hotspot composed of an isotopically normal core surrounded by a rim composed of 17O-rich grains is consistent with either original condensation of the core and surrounding grains in the same parent AGB star, or with grain accretion in the ISM or solar nebula.
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U2 - https://doi.org/10.1111/maps.13477
DO - https://doi.org/10.1111/maps.13477
M3 - Article
SN - 1086-9379
VL - 55
SP - 1228
EP - 1256
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
IS - 6
ER -