26Al–26Mg Systematics of Chondrules

Nagashima, K.; Kita, N. T.; Luu, Tu-Han

doi:10.1017/9781108284073.009

Cited by 20 publications

(17 citation statements)

References 94 publications

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“…An analogous argument was made for the Mn-Cr system by Trinquier et al (2008). We interpret the range of younger Al-Mg internal isochron ages in chondrules to reflect various generations of (re-)melting events (e.g., Nagashima et al, 2018), which reset the Al-Mg systematics at a chondrule length scale but not at the scale of bulk chondrites.…”

Section: The Canonical Isochronsupporting

confidence: 66%

“…Our implied suggestion of primordial Al ∕ Mg differences between bulk chondrites might seem at odds with ~ 2-4 Ma younger Al-Mg ages for chondrules (see recent review by Nagashima et al, 2018), the chief constituents of many chondrites. Yet, Larimer and Anders (1970) noted that the formation of chondrules does not seem to be related to the fractionations that set the bulk compositions of the different chondrite groups.…”

Section: The Canonical Isochronmentioning

confidence: 66%

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Bulk chondrite variability in mass independent magnesium isotope compositions – Implications for initial solar system 26Al/27Al and the timing of terrestrial accretion

Luu

Hin

Coath

et al. 2019

Earth and Planetary Science Letters

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We have determined ′ 26 MgDSM-3, the mass-independent variations in 26 Mg ∕ 24 Mg, of primitive, bulk meteorites to precisions better than ± 3 ppm (2se). Our measurements of samples from 10 different chondrite groups show ′ 26 MgDSM-3 that vary from −5 to 22 ppm. Our data define an array with a positive slope in a plot of ′ 26 MgDSM-3 against 27 Al ∕ 24 Mg, which can be used to determine (26 Al ∕ 27 Al)0, i.e. initial 26 Al ∕ 27 Al, and (′ 26 MgDSM-3)0, i.e. initial ′ 26 MgDSM-3. On such an isochron plot, the best fit of our new measurements combined with literature data implies (26 Al ∕ 27 Al)0 of (4.67±0.78)x10 −5 and (′ 26 MgDSM-3)0 of −31.6 ± 5.7 ppm (2se) for ordinary and carbonaceous chondrites, other than CR chondrites, which have anomalously low ′ 26 MgDSM-3. These parameters are within uncertainty of those defined by previous measurements of bulk calcium-, aluminium-rich inclusions (CAIs) that set canonical (26 Al ∕ 27 Al)0 ~ 5x10 −5. The most straightforward interpretation of all these observations is that

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Section: The Canonical Isochronsupporting

confidence: 66%

Section: The Canonical Isochronmentioning

confidence: 66%

Bulk chondrite variability in mass independent magnesium isotope compositions – Implications for initial solar system 26Al/27Al and the timing of terrestrial accretion

Luu

Hin

Coath

et al. 2019

Earth and Planetary Science Letters

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“…Bollard and co-authors conclude that 26 Al was heterogeneously distributed in PPD, and therefore cannot be used as a chronometer. For a different view, see Kita et al (2015), Schrader et al (2017), and Nagashima et al (2018). Verification of these results by other research groups is urgently needed.…”

Section: Pb-pb Absolute and Al-mg Relative Chronologies Of Cais And Cmentioning

confidence: 97%

“…(), and Nagashima et al. (). Verification of these results by other research groups is urgently needed.…”

Section: Origin and Distribution Of 26al In The Ppdmentioning

confidence: 98%

“…Due to small sizes of Al‐rich phases (plagioclase and glass) in chondrules suitable for in situ measurements of Al‐Mg isotope systematics, the internal 26 Al‐ 26 Mg isochrons were measured so far only in a limited number of chondrules in an individual chondrite and to a relatively low precision (Nagashima et al. and references therein). Therefore, it is rather difficult to estimate the possible number of chondrule generations present in a chondrite group (e.g., Schrader et al.…”

Section: Origin and Distribution Of 26al In The Ppdmentioning

confidence: 99%

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Refractory inclusions in carbonaceous chondrites: Records of early solar system processes

Krot

2019

Meteorit & Planetary Scien

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Chondrites consist of three major components: refractory inclusions (Ca,Al‐rich inclusions [CAIs] and amoeboid olivine aggregates), chondrules, and matrix. Here, I summarize recent results on the mineralogy, petrology, oxygen, and aluminum‐magnesium isotope systematics of the chondritic components (mainly CAIs in carbonaceous chondrites) and their significance for understanding processes in the protoplanetary disk (PPD) and on chondrite parent asteroids. CAIs are the oldest solids originated in the solar system: their U‐corrected Pb‐Pb absolute age of 4567.3 ± 0.16 Ma is considered to represent time 0 of its evolution. CAIs formed by evaporation, condensation, and aggregation in a gas of approximately solar composition in a hot (ambient temperature >1300 K) disk region exposed to irradiation by solar energetic particles, probably near the protoSun; subsequently, some CAIs were melted in and outside their formation region during transient heating events of still unknown nature. In unmetamorphosed, type 2–3.0 chondrites, CAIs show large variations in the initial 26Al/27Al ratios, from <5 × 10–6 to ~5.25 × 10–5. These variations and the inferred low initial abundance of 60Fe in the PPD suggest late injection of 26Al by a wind from a nearby Wolf–Rayet star into the protosolar molecular cloud core prior to or during its collapse. Although there are multiple generations of CAIs characterized by distinct mineralogies, textures, and isotopic (O, Mg, Ca, Ti, Mo, etc.) compositions, the 26Al heterogeneity in the CAI‐forming region(s) precludes determining the duration of CAIs formation using 26Al‐26Mg systematics. The existence of multiple generations of CAIs and the observed differences in CAI abundances in carbonaceous and noncarbonaceous chondrites may indicate that CAIs were episodically formed and ejected by a disk wind from near the Sun to the outer solar system and then spiraled inward due to gas drag. In type 2–3.0 chondrites, most CAIs surrounded by Wark–Lovering rims have uniform Δ17O (= δ17O−0.52 × δ18O) of ~ −24‰; however, there is a large range of Δ17O (from ~−40 to ~ −5‰) among them, suggesting the coexistence of 16O‐rich (low Δ17O) and 16O‐poor (high Δ17O) gaseous reservoirs at the earliest stages of the PPD evolution. The observed variations in Δ17O of CAIs may be explained if three major O‐bearing species in the solar system (CO, H2O, and silicate dust) had different O‐isotope compositions, with H2O and possibly silicate dust being 16O‐depleted relative to both the Genesis solar wind Δ17O of −28.4 ± 3.6‰ and even more 16O‐enriched CO. Oxygen isotopic compositions of CO and H2O could have resulted from CO self‐shielding in the protosolar molecular cloud (PMC) and the outer PPD. The nature of 16O‐depleted dust at the earliest stages of PPD evolution remains unclear: it could have either been inherited from the PMC or the initially 16O‐rich (solar‐like) MC dust experienced O‐isotope exchange during thermal processing in the PPD. To understand the chemical and isotopic composition of the protosolar MC...

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Chondrule Properties and Formation Conditions

Marrocchi,

Jones,

Russell

et al. 2024

Space Sci Rev

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Chondrules are iconic sub-millimeter spheroids representing the most abundant high-temperature dust formed during the evolution of the circumsolar disk. Chondrules have been the subject of a great deal of research, but no consensus has yet emerged as to their formation conditions. In particular, the question of whether chondrules are of nebular or planetary origin remains largely debated. Building upon decades of chondrule investigation and recent headways in combining petrographic observations and O−Ti−Cr isotopic compositions, we here propose a comprehensive vision of chondrule formation. This holistic approach points toward a nebular origin of both NC and CC chondrules, with repetitive high-temperature recycling processes controlling the petrographic and isotopic diversities shown by chondrules. Chondrule precursors correspond to mixing between (i) early-formed refractory inclusions ± NC-like dust and (ii) previous generation of chondrules ± CI-like material. Chondrule formation took place under open conditions with gas-melt interactions with multi-species gas (H2O, Mg, SiO) playing a key role for establishing their characteristics. Petrographic and isotopic systematics do not support disk-wide transport of chondrules but point toward local formation of chondrules within their respective accretion reservoirs. Altogether, this shows that several generations of genetically-related chondrules (i.e., deriving from each other) co-exist in chondrites. In addition to supporting the nebular brand of chondrule-forming scenarios, this argues for repetitive and extremely localized heating events for producing chondrules.

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26Al–26Mg Systematics of Chondrules

Cited by 20 publications

References 94 publications

Bulk chondrite variability in mass independent magnesium isotope compositions – Implications for initial solar system 26Al/27Al and the timing of terrestrial accretion

Bulk chondrite variability in mass independent magnesium isotope compositions – Implications for initial solar system 26Al/27Al and the timing of terrestrial accretion

Refractory inclusions in carbonaceous chondrites: Records of early solar system processes

Chondrule Properties and Formation Conditions

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