TY - JOUR
T1 - Late formation of a comet Wild 2 crystalline silicate particle, Pyxie, inferred from Al-Mg chronology of plagioclase
AU - Nakashima, Daisuke
AU - Ushikubo, Takayuki
AU - Kita, Noriko T.
AU - Weisberg, Michael K.
AU - Zolensky, Michael E.
AU - Ebel, Denton S.
N1 - Publisher Copyright:
© 2014 Elsevier B.V.
Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2015/1/5
Y1 - 2015/1/5
N2 - We examined the Al-Mg isotope systematics of plagioclase in a FeO-poor ferromagnesian Wild 2 particle (C2092,7,81,1,0; named Pyxie) using a ~2 μm spot. Three analyses show average 27Al/24Mg ratio of ~65 and excess δ26Mg* value of +0.1±4.5‰ (2σ), indicating no resolvable 26Mg excess in the particle. The inferred initial (26Al/27Al)0 ratio of plagioclase in Pyxie is estimated as (-0.6±4.5)×10-6 with an upper limit of 4×10-6. The result is very similar to that of the FeO-rich ferromagnesian particle "Iris" (Ogliore et al., 2012). Assuming homogeneous distribution of 26Al in the early solar system, Pyxie formed at least 2.6 Ma after the oldest Ca-Al-rich inclusions. This minimum formation age is marginally younger than formation ages of most chondrules in type ~3.0 chondrites but comparable with those of Mg#<98 chondrules in CR3 chondrites. Considered in conjunction with similar oxygen isotope ratios between Pyxie (and Iris) and Mg#<98 chondrules in CR3 chondrites, it is inferred that the ferromagnesian Wild 2 particles and Mg#<98 chondrules in CR3 chondrites formed late in local disk environments that had similar oxygen isotope ratios and redox states.
AB - We examined the Al-Mg isotope systematics of plagioclase in a FeO-poor ferromagnesian Wild 2 particle (C2092,7,81,1,0; named Pyxie) using a ~2 μm spot. Three analyses show average 27Al/24Mg ratio of ~65 and excess δ26Mg* value of +0.1±4.5‰ (2σ), indicating no resolvable 26Mg excess in the particle. The inferred initial (26Al/27Al)0 ratio of plagioclase in Pyxie is estimated as (-0.6±4.5)×10-6 with an upper limit of 4×10-6. The result is very similar to that of the FeO-rich ferromagnesian particle "Iris" (Ogliore et al., 2012). Assuming homogeneous distribution of 26Al in the early solar system, Pyxie formed at least 2.6 Ma after the oldest Ca-Al-rich inclusions. This minimum formation age is marginally younger than formation ages of most chondrules in type ~3.0 chondrites but comparable with those of Mg#<98 chondrules in CR3 chondrites. Considered in conjunction with similar oxygen isotope ratios between Pyxie (and Iris) and Mg#<98 chondrules in CR3 chondrites, it is inferred that the ferromagnesian Wild 2 particles and Mg#<98 chondrules in CR3 chondrites formed late in local disk environments that had similar oxygen isotope ratios and redox states.
KW - Al-Mg isotope systematics
KW - Comet 81P/Wild 2
KW - Crystalline silicate
KW - Solar system formation
KW - Stardust
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U2 - 10.1016/j.epsl.2014.11.020
DO - 10.1016/j.epsl.2014.11.020
M3 - Article
AN - SCOPUS:84949117670
VL - 410
SP - 54
EP - 61
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
SN - 0012-821X
ER -