Refractory inclusions as Type IA chondrule precursors: Constraints from melting experiments

Whattam, Scott A.; Hewins, R. H.; Seo, Jieun; Devouard, Bertrand

doi:10.1016/j.gca.2021.12.022

Cited by 4 publications

(2 citation statements)

References 88 publications

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“…Most chondrites contain CAIs and other highly refractory inclusions, including presolar grains, which formed 0.7 Ma or more before the chondrules (MacPherson, 2007; MacPherson et al., 2005; Piralla et al., 2023; Whattam et al., 2022). CAIs are believed to be condensates of a brief, hot phase of the solar nebula, although the cause and spatial extent of this hot phase are uncertain.…”

Section: Discussion: Testing a Splash–flyby Hybrid Frameworkmentioning

confidence: 99%

Chondrule formation during low‐speed collisions of planetesimals: A hybrid splash–flyby framework

Herbst,

Greenwood

2024

Meteorit & Planetary Scien

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Chondrules probably formed during a small window of time ~1–4 Ma after CAIs, when most solid matter in the asteroid belt was already in the form of km‐sized planetesimals. They are unlikely, therefore, to be “building blocks” of planets or abundant on asteroids, but more likely to be a product of energetic events common in the asteroid belt at that epoch. Laboratory experiments indicate that they could have formed when solids of primitive composition were heated to temperatures of ~1600 K and then cooled for minutes to hours. A plausible heat source for this is magma, which is likely to have been abundant in the asteroid belt at that time, and only that time, due to the trapping of 26Al decay energy in planetesimal interiors. Here, we propose that chondrules formed during low‐speed () collisions between large planetesimals when heat from their interiors was released into a stream of primitive debris from their surfaces. Heating would have been essentially instantaneous and cooling would have been on the dynamical time scale, ~30 min, where is the mean density of a planetesimal. Many of the heated fragments would have remained gravitationally bound to the merged object and could have suffered additional heating events as they orbited and ultimately accreted to its surface. This is a hybrid of the splash and flyby models: We propose that it was the energy released from a body's molten interior, not its mass, that was responsible for chondrule formation by heating primitive debris that emerged from the collision.

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Section: Discussion: Testing a Splash–flyby Hybrid Frameworkmentioning

confidence: 99%

Chondrule formation during low‐speed collisions of planetesimals: A hybrid splash–flyby framework

Herbst,

Greenwood

2024

Meteorit & Planetary Scien

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“…For carbonaceous chondrites containing mostly type I porphyritic chondrules, a peak temperature around 1600 °C is widely accepted. Interestingly, recent dynamic crystallization experiments mimicking chondrule formation from the melting of AOA‐like assemblages showed that relict spinel is totally resorbed at temperature ≥1600 °C (Whattam et al., 2021). As no inherited grain was observed within the type I chondrules we surveyed, this suggests they have experienced peak temperatures of at least 1600 °C.…”

Section: Discussionmentioning

confidence: 99%

Spinel in CV chondrules: Investigating precursor legacy and chondrule thermal histories

Schnuriger

Cartier

Villeneuve

et al. 2022

Meteorit & Planetary Scien

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In carbonaceous chondrites, Mg‐spinel (MgAl2O4) grains are ubiquitous in refractory inclusions but rarely reported in chondrules, where they may correspond to minerals either (i) inherited from chondrule precursors or (ii) crystallized from chondrule melts. Here, we report high‐current quantitative electron microprobe measurements and secondary ion mass spectrometry oxygen isotopic analyses of Mg‐spinel‐bearing chondrules in the CV3 carbonaceous chondrites Northwest Africa 10235 and Allende. Compared to spinels in refractory inclusions, chondrule spinels are characterized by higher Cr contents and 16O‐poorer oxygen isotopic signatures (∆17O ≡ δ17O−0.52 × δ18O, from −2 to −6‰). Because the similar Δ17O values of chondrule olivine and spinel crystals imply their comagmatic origin, we applied a geothermometer based on the Al‐Cr distribution between these minerals to determine their crystallization temperatures. The calculated temperatures range from 1200 to 1640 °C (mean = 1470 °C), most being lower than the estimated liquidus temperature of porphyritic chondrules (~1600 °C). Our results suggest that chondrules experienced relatively slow cooling rates (slower than a few hundreds of °C h−1), which is in good agreement with models of chondrule formation invoking nonlinear or two‐stage cooling rates.

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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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Refractory inclusions as Type IA chondrule precursors: Constraints from melting experiments

Cited by 4 publications

References 88 publications

Chondrule formation during low‐speed collisions of planetesimals: A hybrid splash–flyby framework

Chondrule formation during low‐speed collisions of planetesimals: A hybrid splash–flyby framework

Spinel in CV chondrules: Investigating precursor legacy and chondrule thermal histories

Chondrule Properties and Formation Conditions

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