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Michael K Weisberg - One of the best experts on this subject based on the ideXlab platform.
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late formation of a comet wild 2 crystalline silicate particle pyxie inferred from al Mg chronology of plagioclase
Earth and Planetary Science Letters, 2015Co-Authors: Daisuke Nakashima, Noriko T Kita, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, Denton S EbelAbstract: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‰+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(−0.6±4.5)×10−6 with an upper limit of 4×10−64×10−6. 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.
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oxygen isotopes in crystalline silicates of comet wild 2 a comparison of oxygen isotope systematics between wild 2 particles and chondritic materials
Earth and Planetary Science Letters, 2012Co-Authors: Daisuke Nakashima, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, D J Joswiak, D E Brownlee, G Matrajt, N T KitaAbstract:Abstract Oxygen three-isotope ratios of nine crystalline silicate particles from comet Wild 2 were measured to investigate oxygen isotope systematics of cometary materials. We are able to analyze particles as small as 4 μm using an ion microprobe with a∼1×2 μm beam by locating the analysis spots with an accuracy of ±0.4 μm. Three particles of Mn-rich forsterite, known as low-iron, manganese-enriched (LIME) olivine, showed extremely 16O-rich signatures (δ18O, δ17O∼−50‰), similar to refractory inclusions in chondrites. The three Mn-rich forsterite particles may have formed by condensation from an 16O-rich solar nebula gas. Other particles consist of olivine and/or pyroxene with a wide range of Mg# [=molar MgO/(FeO+MgO) %] from 60 to 96. Their oxygen isotope ratios plot nearly along the carbonaceous chondrite anhydrous mineral (CCAM) and Young and Russell lines with Δ17O(=δ17O−0.52×δ18O) values of –3.0‰ to +2.5‰. These data are similar to the range observed from previous analyses of Wild 2 crystalline silicates and those of chondrules in carbonaceous chondrites. Six particles extracted from Stardust track 77 show diverse chemical compositions and isotope ratios; two Mn-rich forsterites, FeO-poor pigeonite, and three FeO-rich olivines with a wide range of Δ17O values from −24‰ to +1.6‰. These results confirmed that the original projectile that formed track 77 was an aggregate (>6 μm) of silicate particles that formed in various environments. The Δ17O values of ferromagnesian Wild 2 particles (including data from previous studies) increase from ∼−23‰ to+2.5‰ with decreasing Mg#: Δ17O values of Mn-rich forsterite particles (Mg#=98–99.8) cluster at −23‰, those of FeO-poor particles (Mg#=95–97) cluster at −2‰, and those of FeO-rich particles (Mg#≤90) scatter mainly from −1.5‰ to+2.5‰. Compared to chondrules in primitive chondrites, the systematic trend between Mg# and Δ17O among the Wild 2 particles is most similar to that reported for CR chondrite chondrules. We argue that CR chondrites and some cometary materials share multiple common chemical and isotope characteristics. We suggest that many of the crystalline silicate particles formed in the outer regions of the asteroid belt, or regions that share the common properties, and were transported to comet-forming regions and accreted into comet Wild 2.
Daisuke Nakashima - One of the best experts on this subject based on the ideXlab platform.
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petrogenesis and provenance of ungrouped achondrite northwest africa 7325 from petrology trace elements oxygen chromium and titanium isotopes and mid ir spectroscopy
Geochimica et Cosmochimica Acta, 2017Co-Authors: Cyrena A Goodrich, Noriko T Kita, Qingzhu Yin, Matthew E Sanborn, C D Williams, Daisuke Nakashima, M D Lane, Shannon BoyleAbstract:Northwest Africa (NWA) 7325 is an ungrouped achondrite that has recently been recognized as a sample of ancient differentiated crust from either Mercury or a previously unknown asteroid. In this work we augment data from previous investigations on petrography and mineral compositions, mid-IR spectroscopy, and oxygen isotope compositions of NWA 7325, and add constraints from Cr and Ti isotope compositions on the provenance of its parent body. In addition, we identify and discuss notable similarities between NWA 7325 and clasts of a rare xenolithic lithology found in polymict ureilites. NWA 7325 has a medium grained, protogranular to poikilitic texture, and consists of 10–15 vol.% Mg-rich olivine (Fo 98), 25–30 vol.% diopside (Wo 45, Mg# 98), 55–60 vol.% Ca-rich plagioclase (An 90), and trace Cr-rich sulfide and Fe,Ni metal. We interpret this meteorite to be a cumulate that crystallized at ⩾1200 °C and very low oxygen fugacity (similar to the most reduced ureilites) from a refractory, incompatible element-depleted melt. Modeling of trace elements in plagioclase suggests that this melt formed by fractional melting or multi-stage igneous evolution. A subsequent event (likely impact) resulted in plagioclase being substantially remelted, reacting with a small amount of pyroxene, and recrystallizing with a distinctive texture. The bulk oxygen isotope composition of NWA 7325 plots in the range of ureilites on the CCAM line, and also on a mass-dependent fractionation line extended from acapulcoites. The e54Cr and e50Ti values of NWA 7325 exhibit deficits relative to terrestrial composition, as do ordinary chondrites and most achondrites. Its e54Cr value is distinct from that of any analyzed ureilite, but is not resolved from that of acapulcoites (as represented by Acapulco). In terms of all these properties, NWA 7325 is unlike any known achondrite. However, a rare population of clasts found in polymict ureilites (“the magnesian anorthitic lithology”) are strikingly similar to NWA 7325 in mineralogy and mineral compositions, oxygen isotope compositions, and internal textures in plagioclase. These clasts are probably xenolithic in polymict ureilites, and could be pieces of NWA 7325-like meteorites. Using constraints from chromium, titanium and oxygen isotopes, we discuss two possible models for the provenance of the NWA 7325 parent body: (1) accretion in the inner solar system from a reservoir similar to that of acapulcoites in Δ17O, e54Cr and e50Ti; or (2) early (<1 Ma after CAI formation) accretion in the outer solar system (beyond the snow line), before 54Cr and 50Ti anomalies were introduced to this region of the solar system. The mid-IR emission spectrum of NWA 7325 obtained in this work matches its modal mineralogy, and so can be compared with spectra of new meteorites or asteroids/planets to help identify similar materials and/or the parent body of NWA 7325.
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late formation of a comet wild 2 crystalline silicate particle pyxie inferred from al Mg chronology of plagioclase
Earth and Planetary Science Letters, 2015Co-Authors: Daisuke Nakashima, Noriko T Kita, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, Denton S EbelAbstract: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‰+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(−0.6±4.5)×10−6 with an upper limit of 4×10−64×10−6. 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.
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oxygen isotopes in crystalline silicates of comet wild 2 a comparison of oxygen isotope systematics between wild 2 particles and chondritic materials
Earth and Planetary Science Letters, 2012Co-Authors: Daisuke Nakashima, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, D J Joswiak, D E Brownlee, G Matrajt, N T KitaAbstract:Abstract Oxygen three-isotope ratios of nine crystalline silicate particles from comet Wild 2 were measured to investigate oxygen isotope systematics of cometary materials. We are able to analyze particles as small as 4 μm using an ion microprobe with a∼1×2 μm beam by locating the analysis spots with an accuracy of ±0.4 μm. Three particles of Mn-rich forsterite, known as low-iron, manganese-enriched (LIME) olivine, showed extremely 16O-rich signatures (δ18O, δ17O∼−50‰), similar to refractory inclusions in chondrites. The three Mn-rich forsterite particles may have formed by condensation from an 16O-rich solar nebula gas. Other particles consist of olivine and/or pyroxene with a wide range of Mg# [=molar MgO/(FeO+MgO) %] from 60 to 96. Their oxygen isotope ratios plot nearly along the carbonaceous chondrite anhydrous mineral (CCAM) and Young and Russell lines with Δ17O(=δ17O−0.52×δ18O) values of –3.0‰ to +2.5‰. These data are similar to the range observed from previous analyses of Wild 2 crystalline silicates and those of chondrules in carbonaceous chondrites. Six particles extracted from Stardust track 77 show diverse chemical compositions and isotope ratios; two Mn-rich forsterites, FeO-poor pigeonite, and three FeO-rich olivines with a wide range of Δ17O values from −24‰ to +1.6‰. These results confirmed that the original projectile that formed track 77 was an aggregate (>6 μm) of silicate particles that formed in various environments. The Δ17O values of ferromagnesian Wild 2 particles (including data from previous studies) increase from ∼−23‰ to+2.5‰ with decreasing Mg#: Δ17O values of Mn-rich forsterite particles (Mg#=98–99.8) cluster at −23‰, those of FeO-poor particles (Mg#=95–97) cluster at −2‰, and those of FeO-rich particles (Mg#≤90) scatter mainly from −1.5‰ to+2.5‰. Compared to chondrules in primitive chondrites, the systematic trend between Mg# and Δ17O among the Wild 2 particles is most similar to that reported for CR chondrite chondrules. We argue that CR chondrites and some cometary materials share multiple common chemical and isotope characteristics. We suggest that many of the crystalline silicate particles formed in the outer regions of the asteroid belt, or regions that share the common properties, and were transported to comet-forming regions and accreted into comet Wild 2.
Takayuki Ushikubo - One of the best experts on this subject based on the ideXlab platform.
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late formation of a comet wild 2 crystalline silicate particle pyxie inferred from al Mg chronology of plagioclase
Earth and Planetary Science Letters, 2015Co-Authors: Daisuke Nakashima, Noriko T Kita, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, Denton S EbelAbstract: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‰+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(−0.6±4.5)×10−6 with an upper limit of 4×10−64×10−6. 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.
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oxygen isotopes in crystalline silicates of comet wild 2 a comparison of oxygen isotope systematics between wild 2 particles and chondritic materials
Earth and Planetary Science Letters, 2012Co-Authors: Daisuke Nakashima, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, D J Joswiak, D E Brownlee, G Matrajt, N T KitaAbstract:Abstract Oxygen three-isotope ratios of nine crystalline silicate particles from comet Wild 2 were measured to investigate oxygen isotope systematics of cometary materials. We are able to analyze particles as small as 4 μm using an ion microprobe with a∼1×2 μm beam by locating the analysis spots with an accuracy of ±0.4 μm. Three particles of Mn-rich forsterite, known as low-iron, manganese-enriched (LIME) olivine, showed extremely 16O-rich signatures (δ18O, δ17O∼−50‰), similar to refractory inclusions in chondrites. The three Mn-rich forsterite particles may have formed by condensation from an 16O-rich solar nebula gas. Other particles consist of olivine and/or pyroxene with a wide range of Mg# [=molar MgO/(FeO+MgO) %] from 60 to 96. Their oxygen isotope ratios plot nearly along the carbonaceous chondrite anhydrous mineral (CCAM) and Young and Russell lines with Δ17O(=δ17O−0.52×δ18O) values of –3.0‰ to +2.5‰. These data are similar to the range observed from previous analyses of Wild 2 crystalline silicates and those of chondrules in carbonaceous chondrites. Six particles extracted from Stardust track 77 show diverse chemical compositions and isotope ratios; two Mn-rich forsterites, FeO-poor pigeonite, and three FeO-rich olivines with a wide range of Δ17O values from −24‰ to +1.6‰. These results confirmed that the original projectile that formed track 77 was an aggregate (>6 μm) of silicate particles that formed in various environments. The Δ17O values of ferromagnesian Wild 2 particles (including data from previous studies) increase from ∼−23‰ to+2.5‰ with decreasing Mg#: Δ17O values of Mn-rich forsterite particles (Mg#=98–99.8) cluster at −23‰, those of FeO-poor particles (Mg#=95–97) cluster at −2‰, and those of FeO-rich particles (Mg#≤90) scatter mainly from −1.5‰ to+2.5‰. Compared to chondrules in primitive chondrites, the systematic trend between Mg# and Δ17O among the Wild 2 particles is most similar to that reported for CR chondrite chondrules. We argue that CR chondrites and some cometary materials share multiple common chemical and isotope characteristics. We suggest that many of the crystalline silicate particles formed in the outer regions of the asteroid belt, or regions that share the common properties, and were transported to comet-forming regions and accreted into comet Wild 2.
N T Kita - One of the best experts on this subject based on the ideXlab platform.
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oxygen isotopes in crystalline silicates of comet wild 2 a comparison of oxygen isotope systematics between wild 2 particles and chondritic materials
Earth and Planetary Science Letters, 2012Co-Authors: Daisuke Nakashima, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, D J Joswiak, D E Brownlee, G Matrajt, N T KitaAbstract:Abstract Oxygen three-isotope ratios of nine crystalline silicate particles from comet Wild 2 were measured to investigate oxygen isotope systematics of cometary materials. We are able to analyze particles as small as 4 μm using an ion microprobe with a∼1×2 μm beam by locating the analysis spots with an accuracy of ±0.4 μm. Three particles of Mn-rich forsterite, known as low-iron, manganese-enriched (LIME) olivine, showed extremely 16O-rich signatures (δ18O, δ17O∼−50‰), similar to refractory inclusions in chondrites. The three Mn-rich forsterite particles may have formed by condensation from an 16O-rich solar nebula gas. Other particles consist of olivine and/or pyroxene with a wide range of Mg# [=molar MgO/(FeO+MgO) %] from 60 to 96. Their oxygen isotope ratios plot nearly along the carbonaceous chondrite anhydrous mineral (CCAM) and Young and Russell lines with Δ17O(=δ17O−0.52×δ18O) values of –3.0‰ to +2.5‰. These data are similar to the range observed from previous analyses of Wild 2 crystalline silicates and those of chondrules in carbonaceous chondrites. Six particles extracted from Stardust track 77 show diverse chemical compositions and isotope ratios; two Mn-rich forsterites, FeO-poor pigeonite, and three FeO-rich olivines with a wide range of Δ17O values from −24‰ to +1.6‰. These results confirmed that the original projectile that formed track 77 was an aggregate (>6 μm) of silicate particles that formed in various environments. The Δ17O values of ferromagnesian Wild 2 particles (including data from previous studies) increase from ∼−23‰ to+2.5‰ with decreasing Mg#: Δ17O values of Mn-rich forsterite particles (Mg#=98–99.8) cluster at −23‰, those of FeO-poor particles (Mg#=95–97) cluster at −2‰, and those of FeO-rich particles (Mg#≤90) scatter mainly from −1.5‰ to+2.5‰. Compared to chondrules in primitive chondrites, the systematic trend between Mg# and Δ17O among the Wild 2 particles is most similar to that reported for CR chondrite chondrules. We argue that CR chondrites and some cometary materials share multiple common chemical and isotope characteristics. We suggest that many of the crystalline silicate particles formed in the outer regions of the asteroid belt, or regions that share the common properties, and were transported to comet-forming regions and accreted into comet Wild 2.
M E Zolensky - One of the best experts on this subject based on the ideXlab platform.
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late formation of a comet wild 2 crystalline silicate particle pyxie inferred from al Mg chronology of plagioclase
Earth and Planetary Science Letters, 2015Co-Authors: Daisuke Nakashima, Noriko T Kita, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, Denton S EbelAbstract: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‰+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(−0.6±4.5)×10−6 with an upper limit of 4×10−64×10−6. 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.
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oxygen isotopes in crystalline silicates of comet wild 2 a comparison of oxygen isotope systematics between wild 2 particles and chondritic materials
Earth and Planetary Science Letters, 2012Co-Authors: Daisuke Nakashima, Takayuki Ushikubo, Michael K Weisberg, M E Zolensky, D J Joswiak, D E Brownlee, G Matrajt, N T KitaAbstract:Abstract Oxygen three-isotope ratios of nine crystalline silicate particles from comet Wild 2 were measured to investigate oxygen isotope systematics of cometary materials. We are able to analyze particles as small as 4 μm using an ion microprobe with a∼1×2 μm beam by locating the analysis spots with an accuracy of ±0.4 μm. Three particles of Mn-rich forsterite, known as low-iron, manganese-enriched (LIME) olivine, showed extremely 16O-rich signatures (δ18O, δ17O∼−50‰), similar to refractory inclusions in chondrites. The three Mn-rich forsterite particles may have formed by condensation from an 16O-rich solar nebula gas. Other particles consist of olivine and/or pyroxene with a wide range of Mg# [=molar MgO/(FeO+MgO) %] from 60 to 96. Their oxygen isotope ratios plot nearly along the carbonaceous chondrite anhydrous mineral (CCAM) and Young and Russell lines with Δ17O(=δ17O−0.52×δ18O) values of –3.0‰ to +2.5‰. These data are similar to the range observed from previous analyses of Wild 2 crystalline silicates and those of chondrules in carbonaceous chondrites. Six particles extracted from Stardust track 77 show diverse chemical compositions and isotope ratios; two Mn-rich forsterites, FeO-poor pigeonite, and three FeO-rich olivines with a wide range of Δ17O values from −24‰ to +1.6‰. These results confirmed that the original projectile that formed track 77 was an aggregate (>6 μm) of silicate particles that formed in various environments. The Δ17O values of ferromagnesian Wild 2 particles (including data from previous studies) increase from ∼−23‰ to+2.5‰ with decreasing Mg#: Δ17O values of Mn-rich forsterite particles (Mg#=98–99.8) cluster at −23‰, those of FeO-poor particles (Mg#=95–97) cluster at −2‰, and those of FeO-rich particles (Mg#≤90) scatter mainly from −1.5‰ to+2.5‰. Compared to chondrules in primitive chondrites, the systematic trend between Mg# and Δ17O among the Wild 2 particles is most similar to that reported for CR chondrite chondrules. We argue that CR chondrites and some cometary materials share multiple common chemical and isotope characteristics. We suggest that many of the crystalline silicate particles formed in the outer regions of the asteroid belt, or regions that share the common properties, and were transported to comet-forming regions and accreted into comet Wild 2.