# Early generation of a refractory inclusions-enriched H-chondritic parent body: A safe harbor for Ca, Al-rich inclusions

Samuel Ebert, Kazuhide Nagashima, Alexander Krot, Shigeru Wakita, Jean-Alix Barrat, Addi Bischoff

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## To cite this version:

Samuel Ebert, Kazuhide Nagashima, Alexander Krot, Shigeru Wakita, Jean-Alix Barrat, et al. Early generation of a refractory inclusions-enriched H-chondritic parent body: A safe harbor for Ca, Al-rich inclusions. Earth and Planetary Science Letters, 2024, 646, pp.119010. 10.1016/j.epsl.2024.119010. hal-04931399

HAL Id: hal-04931399

https://hal.univ-brest.fr/hal-04931399v1

Submitted on 21 Mar 2025

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# Early generation of a refractory inclusions-enriched H-chondritic parent body: A safe harbor for Ca, Al-rich inclusions

Samuel Ebert a,*, Kazuhide Nagashima b, Alexander N. Krot b, Shigeru Wakita c, Jean-Alix Barrat d, Addi Bischoff a

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## ARTICLE INFO

Editor: Dr O Mousis

**Keywords:**

Chondrite

Mn-Cr dating

Refractory inclusions

Isotopes

Parent body formation

Fayalite

## ABSTRACT

Calcium-aluminum-rich inclusions (CAIs) commonly observed in chondritic meteorites are the oldest dated solids formed in the Solar System. Short-lived isotope chronologies ($^{26}$Al-$^{26}$Mg, $^{182}$Hf-$^{182}$W) suggest a ~2 Ma gap between the formation of CAIs and the accretion of the final chondrite parent bodies. One thin section, 3.27 cm² in size, of an ordinary chondrite NWA 3358 (H3.1) studied contains 52 refractory inclusions (CAIs and amoeboid olivine aggregates (AOAs)) comprising 0.14 % of its area, which is the highest abundance of refractory inclusions among non-carbonaceous chondrites containing on average ~0.009 area % of CAIs and AOAs. In combination with a low chondrule/matrix ratio of ~1.5, this makes NWA 3358 a unique ordinary chondrite. The aqueously-formed fayalites (Fa>99) in NWA 3358 have the inferred initial $^{53}$Mn/$^{55}$Mn ratio of (5.56 ± 0.44) × 10⁻⁶ which is the highest measured value for secondary minerals in chondrites and corresponds to the formation time of ~1.0–1.5 Ma after CAIs. Based on the $^{53}$Mn-$^{53}$Cr chronology of fayalite formation and the thermal modeling, we infer that the first-generation of an H chondrite parent body, ~6–12 km in diameter, accreted within 1.0 Ma after formation of CAIs, filling the gap of ~2 Ma between CAIs and the earliest chondrite parent bodies. This early accretion provides a possible mechanism of CAIs/AOAs storage in the inner solar nebula and could explain the high amount of refractory inclusions in NWA 3358. A later destruction of these first-generation bodies may also explain the presence of CAIs and chondrules of different ages within later formed chondrite parent bodies.

## 1. Introduction

Understanding the processes and timing of when the first planetesimals accreted in the protoplanetary disk is fundamental to reveal the formation history of asteroid-size bodies, which led to the formation of terrestrial planets. Meteorites play a special role in this investigation, as they provide insights into the first million years evolution of our solar system.

Calcium-aluminum-rich inclusions (CAIs) from CV (Vigarano type) carbonaceous chondrites formed 4567.30 ± 0.16 Ma (Connelly et al., 2012) are the oldest dated objects formed in the solar system and represent the start of its evolution. Calcium-aluminum-rich inclusions formed by evaporation, condensation, aggregation and melting processes in a gas of approximately solar composition in a high-temperature region of the protoplanetary disk exposed to irradiation by solar

energetic particles (McKeegan et al., 2000), most likely near the young sun, and were subsequently removed from this region by accretion towards the Sun (Weidenschilling, 1977) and outward transport by a viscous expanding disk (Ciesla, 2007; Yang and Ciesla, 2012; Burkhardt et al., 2019).

Accretion of meteorite parent bodies appear to have started nearly contemporaneously with the formation of CAIs and lasted for about 4 Ma. The first parent bodies of iron meteorites accreted 0.1–0.3 Ma after CAIs (Kruijer et al., 2014). Chondrite parent bodies composed of refractory inclusions (CAIs and amoeboid olivine aggregates (AOAs)), chondrules, and fine-grained matrices accreted ~2–5 Ma after CAIs (Fujiya et al. 2012; Doyle et al., 2015; Keil et al., 2015; Desch et al., 2018; Bischoff et al., 2021). Non-carbonaceous (NC: ordinary, enstatite, Rumuruti, and Kakangari-like) and carbonaceous chondrites (CC: Cl, CM, CR, CO, CV, CK, CH, CB, CY, CL) are inferred to have accreted inside

<footnote>a Institut für Planetologie, University of Münster, D-48149, Münster, Germany</footnote>

<footnote>b Hawai'i Institute of Geophysics and Planetology, University of Hawai'i at Manoa, Honolulu, HI 96822, USA</footnote>

<footnote>c Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</footnote>

<footnote>d Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, Place Nicolas Copernic, F-29280, Plouzané Cedex, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: samuel.ebert@uni-muenster.de (S. Ebert).</footnote>
and outside Jupiter, respectively (Kruijer et al., 2017, 2020; Desch et al., 2018). The apparent age gap between formation of refractory inclusions and their accretion into chondrite parent bodies has led to the so-called CAI storage problem (Desch et al., 2018): dust and small grains, like refractory inclusions in the sizes typical for NC chondrites (average diameter ~50 µm; Hezel et al., 2008) are expected to spiral into the Sun by aerodynamic drag forces at rates of >1 AU/Ma (Weidenschilling, 1977). As a result, refractory inclusions are not expected to have been present in the inner part of the protoplanetary disk where NC chondrites formed. However, refractory inclusions have been identified in every NC chondrite group (e.g., Bischoff and Keil, 1983; Bischoff et al., 1985, Rout et al., 2008; Ebert et al., 2018; Ebert et al., 2020; Dunham et al., 2023 and references therein), and this raises the question of what kind of processes could have hampered the inward movement of refractory inclusions.

In the case of CCs, Jupiter most likely played a key role preventing refractory inclusions from spiraling into the Sun (Desch et al., 2018). In the outer solar system, refractory inclusions could have been stored and concentrated in a pressure maximum exterior of an early and rapidly formed Jupiter (Desch et al., 2018). The proto-Jupiter would open a gap in the protoplanetary disk and separate the inner (NC) from the outer (CC) region and prevent a large-scale mixing between these two regions resulting in a refractory inclusion-enriched CC and refractory inclusion-depleted NC regions. This "barrier" seems not to be 100 % efficient and small particles, typically <100–300 µm in size, from the outer solar system could have bridged the gap (Ebert et al., 2018; Haugbølle et al., 2019). This model can therefore explain some of the refractory inclusions present in NC chondrites but fails to explain the presence of some larger CAIs up to 400–600 µm (Russel et al., 2016) and high abundance of ¹⁶O-enriched clasts in some NC chondrites (Kerraouch et al., 2022), including NWA 3358 (this study).

Therefore, an additional process is required to prevent refractory inclusions in the inner protoplanetary disk to spiral into the Sun. One possible way would be if chondritic planetesimals formed earlier (within first Ma) as first-generation bodies, because that may allow to preserve refractory inclusions in the NC region (van Kooten et al., 2019; Weidenschilling, 2019). Such hypothetical bodies may contain higher abundances of CAIs and AOAs than the final chondrite parent bodies. So far, only few possible remnants of first-generation bodies have been found: they occur within various chondritic meteorites as small fragments/clasts having different composition and petrography than the host meteorites (Metzler et al., 1992; Bischoff, 1998; Ebert et al., 2019; Kerraouch et al., 2022). Unfortunately, it may be difficult to distinguish between the small first-generation bodies and the final larger chondrite parent bodies if they accreted in the same region of the protoplanetary disk and had similar mineralogy, petrology, and bulk oxygen isotopic compositions.

One possible way to distinguish between different generations of parent bodies would be to date the formation time of low-temperature aqueous alteration minerals in chondritic meteorite samples. Aqueous alteration is ubiquitous in chondritic meteorites suggesting that chondritic asteroids were heated to temperatures well above melting temperature of water ice shortly after they accreted. Therefore, alteration products can be used to constrain accretion ages of chondrite parent bodies (Krot et al., 2006; Weidenschilling, 2019). The water/rock ratio and temperature in the respective chondrite strongly affect what kind of secondary minerals are formed. For example, in CI and CM chondrites, which experienced aqueous alteration at low temperatures (<100 °C) and high water/rock ratios (0.3–0.8), phyllosilicates, carbonates and magnetite are the most abundant secondary minerals (Brearley, 2006; Zolensky et al., 2008). In CO, CV, and unequilibrated ordinary chondrites, which experienced aqueous alteration at higher temperatures (~100–350 °C) and lower water/rock ratios (<0.3), common secondary minerals include fayalite, magnetite, kirschsteinite, hedenbergite, wollastonite, andradite, and ferroan olivine; phyllosilicates are minor (Zolotov et al., 2006; Brearley and Krot, 2013). The oxygen isotopic

composition of such alteration minerals is largely defined by the O-isotope composition of the aqueous fluid. In type 3 ordinary chondrites, including H3.1 chondrite NWA 3358, aqueously formed fayalite and magnetite are characterized by ¹⁶O-poor compositions with Δ¹⁷O = δ¹⁷O – (0.52 × δ¹⁸O) of ~ +5 ± 1 ‰ (Doyle et al., 2015; Ebert et al., 2020) compared to the O-isotopic bulk composition of H3 chondrites with Δ¹⁷O ~0.66 ‰ (Clayton et al., 1991).

The short-lived radionuclide ⁵³Mn, which decays to ⁵³Cr with a half-life of ~3.7 Ma, was homogenously distributed in the protoplanetary disk (Trinquier et al., 2008). This observation and the high ⁵⁵Mn/⁵²Cr ratio in aqueously-formed fayalite, kirschsteinite, and carbonates make ⁵³Mn-⁵³Cr chronology a useful tool for dating aqueous alteration in ordinary and carbonaceous chondrites (Fujiya et al., 2012; Doyle et al., 2016). We note, however, that ⁵³Mn-⁵³Cr is a relative chronometer that cannot give an absolute age; an age anchor is required. Here we report on ⁵³Mn-⁵³Cr systematics of fayalite in the H3.1 chondrite NWA 3358 measured in situ using secondary ion mass-spectrometry (SIMS) and a synthetic fayalite standard (Doyle et al., 2015; see also Section 2.4).

## 2. Methods

### 2.1. Sample identification and selection

The polished thin section of NWA 3358 (H3.10) with the internal number PL05192 was provided by the *Institut für Planetologie* at the *University of Münster*. NWA 3358 is classified as a H-chondrite in the Meteorological Bulletin Database based on its petrography and geochemistry with an O-isotopic bulk composition that plots within the field, but near the edge, of the H-chondrites in a three-isotope oxygen diagram. The petrologic subtype of 3.10 is based on the mean Cr₂O₃ content of olivine in type II chondrules from NWA 3358. For identification of the fayalite grains and refractory inclusions within the matrix (Fig. 1), a JEOL 6610-LV electron microscope (SEM) at the Interdisciplinary Center for Electron Microscopy and Microanalysis (ICEM) at the *University of Münster* was used. The attached EDS system (INCA; Oxford Instruments) was used for chemical characterization and analyses of the olivine fayalite content at 20 keV. The beam current was controlled using a Faraday cup. Standard (Astimex) olivine (Mg, Fe, Si), plagioclase (Al), diopside (Ca), rutile (Ti), chromium-oxide (Cr), rhodonite (Mn), and pentlandite (Ni) were used as natural and synthetic standards. Only olivine grains >10 µm in size and Fa>99 (Fig. 2) were used for further investigations with the SIMS.

### 2.2. Determination of chondrules' and components' modal abundances

A detailed BSE mosaic map (Fig. 1) was created by ~220 single BSE images with a magnification of 85. Image analyses were performed with the software JMicrovision (https://jmicrovision.github.io/download.htm). The modal abundances of the different phases and components were determined by point counting (2000 points; random position). As refractory inclusions are in general very small, the modal abundances were determined by a different technique (see next section).

### 2.3. Determination of CAI and AOA abundances

Detailed Al-maps were created from the investigated thin section to identify objects with high Al-abundances. Identified objects were directly investigated with the SEM to determine the mineral phases and create a BSE image from each single refractory inclusion (examples are given in Fig. 3). If a major part of a fluffy type inclusion is olivine, the object was classified as an AOA (Fig. 3f), otherwise as a CAI.

The detailed size/area of each single object was determined by using Photoshop and its internal measurement tool. If two CAIs were located directly next to each other and had the same mineralogy/shape, they were counted as one CAI (Fig. 3b). A high amount of single spinel grains or hibonite/corundum grains within the matrix itself were not included
<figure><img src="image_5.png" /><figcaption>Fig. 1. BSE mosaic map of NWA 3358. Positions of the measured fayalite grains are marked in white circles and the position of all refractory inclusions are marked with red circles. Numbers in a red circle give the amount of refractory inclusions contained therein. The six examples of Fig. 3 are also labeled next to its individual position.</figcaption></figure>

to the list of individual refractory inclusions. This also counts for spinel grains within chondrules. CAI and AOA diameters were calculated as in (Dunham et al., 2023) to get comparable results:

$$ \text{CAI diameter} = 2 \times \sqrt{\frac{\text{area CAI}}{\pi}} $$

The combined abundance of CAIs and AOAs are given in area% as they were obtained of a thin section. If we assume that refractory inclusions are uniformly distributed in the meteorite/parent body and that the refractory inclusions are uniformly distributed in our thin section (Fig. 1) and assuming that the thickness of the thin section is negligible compared to the thickness of the meteorite/parent body, we can ignore the volume to area ratio. Therefore, area% can be seen as vol.%. This also counts for the modal abundances of chondrules, matrix, and sulfides from NWA 3358 determined by point counting.

## 2.4. SIMS measurements

Mn-Cr isotope data were collected in situ with the UH Cameca imsm-1280 ion microprobe. An $^{16}$O$^-$ primary beam with a 100 pA current was focused into a spot of ~7 µm in diameter and used to collect data from liquidus-phase synthetic olivines (Fa$_{99}$) as a standard and fayalites (Fa$_{>99}$) from the H3.1 chondrite NWA 3358.

The positive secondary ions were accelerated with 10 kV, where a 44 eV energy window was used. Three chromium isotopes ($^{50}$Cr$^+$, $^{52}$Cr$^+$ and $^{53}$Cr$^+$) were measured simultaneously using two multicollection EMs (Electron Multipliers) and an axial EM, respectively. Subsequently, $^{55}$Mn$^+$ was measured on the axial EM by peak jumping. To separate the measured ions from interfering species including $^{52}$CrH$^+$, the mass-resolving power was set to ~4500 for $^{50}$Cr$^+$ and $^{52}$Cr$^+$, and ~6000 for $^{53}$Cr$^+$ and $^{55}$Mn$^+$. In previous studies (Keil et al., 2015; Doyle et al., 2015, 2016), the chromium count rates were constantly higher for the first 25 cycles of the measurements and had to be removed. To prevent such a problem, the pre-sputter time was set to 400 s, and isotopic data

were typically collected over 60 cycles.

Chromium-isotope and $^{55}$Mn/$^{52}$Cr ratios were calculated from the total number of counts to suppress systematic bias caused by low count rates of chromium (Ogliore et al., 2011; Telus et al., 2012; Coath et al., 2013). The measured $^{53}$Cr/$^{52}$Cr ratios were corrected for instrumental mass fractionation determined by repeat analyses of synthetic fayalite (Fa$_{99}$; Doyle et al., 2015), which was assumed to have a terrestrial $^{53}$Cr/$^{52}$Cr ratio of 0.113459 (Papanastassiou, 1986). The measured $^{55}$Mn/$^{52}$Cr ratios were corrected by using the calculated RSF of ~1.45 which is defined by ($^{55}$Mn$^{+}$/$^{52}$Cr$^+$)$_{SIMS}$/($^{55}$Mn/$^{52}$Cr)$_{EPMA}$.

Finally, as a last step, all fayalite grains were re-investigated with the SEM again to check whether the fayalites were hit correctly by the ion beam and whether there were any overlaps with other phases or cracks that could affect the measurements (Fig. 2).

## 2.5. Age calculation

As the initial $^{53}$Mn/$^{55}$Mn ratio in the solar system is not known and the measured values of NWA 3358's fayalites had to be anchored to the angrite D'Orbigny, for which ($^{53}$Mn/$^{55}$Mn)$_{0}$ (Glavin et al., 2004; McKibbin et al., 2015) in combination with U-corrected Pb-Pb absolute ages (Brennecka et al., 2012) are known. Therefore, the measured $^{53}$Mn/$^{55}$Mn value of NWA 3358 can be combined with the U-corrected absolute ages of CV CAIs, which have an age of 4567.30 ± 0.16 Ma (Connelly et al., 2012).

However, two different $^{53}$Mn/$^{55}$Mn values for D'Orbigny have been used in the literature: (3.24 ± 0.04) × 10$^{-6}$ (Glavin et al., 2004) and (3.54 ± 0.18) × 10$^{-6}$ (McKibbin et al., 2015), leading to a time difference of nearly 0.5 Ma between the two anchor values and results in different formation times. Both values were used for the calculation to be able to compare the new data with previous measurements. An error propagation was performed including all used values from the literature. In some cases, this resulted in higher errors than specified in the original work, as the final error of the age was only calculated from the
<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Backscatter electron (BSE) images of the investigated fayalite grains after the SIMS measurements. The grains were precisely hit, and no contamination by surrounding material occurred. The O-isotopes-spot was created during a previous study (Ebert et al. 2020).</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Fig. 3. BSE images of various examples of refractory inclusions from NWA 3358: a) Fluffy type and elongated CAI; b) two small CAIs next to each other. They were counted as one CAI because cutting layer effects cannot be ruled out; c & d) two hibonite bearing CAIs; e) CAI fragment that shows strong similarities with a Wark-Lovering rim; f) small spinel, cpx bearing CAIs embedded in olivine. As olivine is very dominant, this was classified as an AOA (Ebert et al., 2020). cpx, various types of Ca-Pyroxene; hib, hibonite; ilm, ilmenite; mel, melilite; ol, olivine; plag, plagioclase; pv, perovskite; sp, spinel; Zn-her, Zn-hercynite.</figcaption></figure>

$^{53}$Mn/$^{55}$Mn error of the measurement itself (Table 3, Fig. 5).

## 2.6. Thermal modeling of NWA 3358 parent body

To evaluate the thermal evolution of the NWA 3358 parent body (H3.1) in accordance with peak metamorphic temperatures, we modeled the temperature range of fayalite formation and the inferred $^{53}$Mn-$^{53}$Cr ages of fayalite crystallization by considering spherically symmetric and

instantly accreting bodies heated only by the decay of $^{26}$Al. The heat conduction equation is given by:

$$ \rho c \frac{\partial T}{\partial t} = \frac{1}{r^2} \frac{\partial}{\partial r} \left( r^2 K \frac{\partial T}{\partial t} \right) + Ae^{-\lambda t} $$

where $\rho$ is density, c is specific heat, T is temperature, t is time, r is radius from the center, K is thermal conductivity, A is initial radiogenic heat generation rate per unit volume, and $\lambda$ is the decay constant of $^{26}$Al. The
equation is solved numerically using a finite difference method and an explicit integral method (Wakita and Sekiya, 2011).

While we used the same thermal modeling method as in Doyle et al. (2015), we adjusted it with different parameters and physical properties for the NWA 3358 parent body.

Some assumptions were made: (1) $^{26}$Al was uniformly distributed in the protoplanetary disk with the canonical $^{26}$Al/$^{27}$Al ratio of 5.25 × 10$^{-5}$ and was the only heat source of a chondrite parent body; (2) some regions of these parent bodies reached 100–200 °C (temperature range of fayalite formation (Zolotov et al., 2006)) at the time of fayalite formation; and (3) to preclude Fe-Mg diffusion in secondary fayalite, these regions avoided subsequent heating above 300 °C.

A range of 2–6 km in radius of parent body and 0.6–2.3 Ma after CAIs for their accretion time were used. The use of an initial $^{26}$Al/$^{27}$Al ratio of 5.25 × 10$^{-5}$ rather than 5 × 10$^{-5}$ corresponds to 0.05 Ma, which is well within the uncertainty of our isotope measurements (±0.95 Ma). Some fixed parameters specific for the NWA 3358 parent body are: water/rock mass ratio of 0.2 (Zolotov et al., 2006); initial temperature of 150 K; aluminum content of 1.13 wt.% (Table S1). To obtain precise Al-data for NWA 3358 necessary for adequate calculation, a 500 mg whole-rock sample was homogenized, and an aliquot was dissolved following the procedure described by Barrat et al. (2012, 2016). The initial parameters of an H-chondritic parent body are assumed to be constant as listed in Table S2. We would like to point out that the water/rock mass ratio of 0.2 may change depending on the porosity of the parent body. However, the effect of porosity is beyond the capability of our current model and we only consider the consolidated body. The latent heat of ice melting has been included, and the effect of ice melting on the thermal evolution were numerically calculated. However, hydration reactions were not included, as the primary goal was to determine whether or not the parent bodies could reach the formation temperature range of fayalite. For simplicity, we ignore the potential influence of an overlying regolith that reduces the thermal diffusivity. Two previous estimates of $^{26}$Al heating of meteorite parent bodies (Lee et al., 1976; Hutcheon et al., 1989) reported much higher temperatures than those calculated here, most likely owing to the differences in the assumed physical properties, such as the thermal diffusivity (previous studies assumed values of <0.01) and the water/rock ratio (assumed to be zero in the previous studies). Because increasing the water/rock ratio not only increases the amount of energy required to heat the parent body to a given temperature (ice has a higher heat capacity than rock) but also reduces the amount of $^{26}$Al (per unit mass) available to produce heat, as water does not contain any $^{26}$Al.

# 3. Results

## 3.1. NWA 3358 component abundances

Determined modal abundances for NWA 3358 obtained by point counting reveals 60 vol.% of chondrules and chondrules fragments, 35 vol.% of matrix materials, and 5 vol.% of metals/sulfides. The chondrule/matrix (including metals/sulfides) ratio is ~1.5.

From detailed Al-maps of NWA 3358, we were able to identify 42 CAIs and 10 AOAs in a single thin section. They are all marked within the BSE-overview image of NWA 3358 (Fig. 1). The 42 CAIs cover 0.00292 cm$^2$ and the 10 AOAs 0.00157 cm$^2$ within an investigated area of 3.27 cm$^2$. The combined abundance of CAIs and AOAs is 0.137 area% (Table 1). This is ~15 × higher than the average abundance of refractory inclusions (~0.009 area%) for NC chondrites (Dunham et al., 2023). Furthermore, CAIs within NWA 3358 have an average diameter of 85 µm and 94 µm if AOAs are also included. This is nearly 2 × higher than the mean diameter of 46 µm for CAIs within NC chondrites (Dunham et al., 2023).

Higher abundances of refractory inclusions in NWA 3358 were already observed during the investigations by Ebert et al. (2020). At that time, only refractory inclusions >100 µm were used for further

<caption>**Table 1**</caption>

CAI and AOA size distributions and abundances from one NWA 3358 thin section.

<table><thead><tr><th>Thin section 3.27 cm<sup>2</sup></th><th>CAIs</th><th>AOAs</th><th>CAIs + AOAs</th></tr></thead><tbody><tr><td>quantity</td><td>42</td><td>10</td><td>52</td></tr><tr><td>area %</td><td>0.09</td><td>0.05</td><td>0.14</td></tr><tr><td>avg diameter [µm]</td><td>85.1</td><td>129.5</td><td>93.6</td></tr><tr><td>std deviation [µm]</td><td>40.4</td><td>60.2</td><td>47.6</td></tr><tr><td>min diameter [µm]</td><td>15.6</td><td>47.3</td><td>15.6</td></tr><tr><td>max diameter [µm]</td><td>167.0</td><td>219.4</td><td>219.4</td></tr><tr><td>median diameter [µm]</td><td>90.1</td><td>115.4</td><td>92.3</td></tr></tbody></table>

Abbreviations: min, minimum; max, maximum.

investigations, but a strikingly higher number of refractory inclusions was discovered in the roughly polished chips, which prompted us to perform further and deeper investigations on NWA 3358. Therefore, this high abundance of refractory inclusions seems to be a common characteristic of this meteorite in general.

## 3.2. Mn-Cr isotopic composition of NWA 3358 and the resulting ages

The Mn-Cr isotopic compositions of NWA 3358 fayalites are listed in Table 2 and Fig. 4. They show large excesses of $^{53}$Mn and high $^{55}$Mn/$^{52}$Cr ratios and define a model isochron with initial $^{53}$Mn/$^{55}$Mn ratio ($^{53}$Mn/$^{55}$Mn)$_0$ of (5.56 ± 0.44) × 10$^{-6}$. However, fayalite #3 (fa-3) has by far the highest $^{55}$Mn/$^{52}$Cr and $^{53}$Cr values of all measured fayalites within NWA 3358, and the slope could be dominated by fa-3 alone (Figs. 4 and S1-S2). This means that if there was, hypothetically, something wrong with the measurement on this grain, it would affect the whole isochron, resulting in wrong ages. Therefore, Fig. S1 shows the results with and without fa-3. The difference between the two slopes is marginal, which clearly shows that fa-3 lies on the extended isochron of the other measurements and that fa-3 is not alone the reason for the higher $^{53}$Mn/$^{55}$Mn value of NWA 3358 compared to previous studies (Table 3). Therefore, the measurements can be considered correct and truthful, resulting in NWA 3358 fayalites formation times of 1.05$^{+0.73}_{-0.76}$ (anchor: Glavin et al., 2004) and 1.52$^{+0.94}_{-0.96}$ Ma (anchor: McKibbin et al., 2015) after CAIs (Table 3, Fig. 5).

## 3.3. NWA 3358 parent body sizes

Results of the thermal modelling of NWA 3358 parent body are plotted in Fig. 6. The field of stability of nearly pure fayalite is ~100–200 °C (Zolotov et al., 2006). A body with the radius of 2 km is too small to reach the temperatures necessary to form fayalite. A body with 3 km in radius is already possible to form fayalite and that body was formed ~0.60–0.75 Ma after CAIs. For a body with 4, 5, and 6 km in radius it would be ~1.05–1.25 Ma, ~1.40–1.60, ~1.60–1.85 Ma after CAIs, respectively. Larger bodies should have been formed later to be able to form fayalite, but in that case, they do not match our ($^{53}$Mn/$^{55}$Mn)$_0$ measured values of NWA 3358 fayalites and the ages calculated from them. Therefore, a parent body of 3–6 km in radius is the best fit to explain the high ($^{53}$Mn/$^{55}$Mn)$_0$ of (5.56 ± 0.44) × 10$^{-6}$ for the nearly pure fayalite.

<caption>**Table 2**</caption>

Mn-Cr isotopic composition of individual fayalite grains from NWA 3358.

<table><thead><tr><th></th><th><sup>55</sup>Mn/<sup>52</sup>Cr</th><th>2σ</th><th><sup>53</sup>Cr/<sup>52</sup>Cr</th><th>2σ</th><th>δ<sup>53</sup>Cr</th><th>2σ</th></tr></thead><tbody><tr><td>fayalite-1</td><td>116.2</td><td>21.9</td><td>0.114</td><td>0.001</td><td>5.4</td><td>6.8</td></tr><tr><td>fayalite-2</td><td>2826.5</td><td>129.0</td><td>0.129</td><td>0.002</td><td>133.4</td><td>18.8</td></tr><tr><td>fayalite-3</td><td>30262.1</td><td>3499.6</td><td>0.275</td><td>0.022</td><td>1420.6</td><td>195.2</td></tr><tr><td>fayalite 5</td><td>1753.9</td><td>36.9</td><td>0.124</td><td>0.002</td><td>89.6</td><td>20.5</td></tr><tr><td>fayalite 9</td><td>918.4</td><td>42.6</td><td>0.117</td><td>0.002</td><td>35.3</td><td>18.4</td></tr><tr><td>fayalite 10</td><td>5618.0</td><td>119.7</td><td>0.146</td><td>0.004</td><td>289.4</td><td>33.4</td></tr><tr><td>fayalite 12_2</td><td>2812.5</td><td>130.0</td><td>0.129</td><td>0.002</td><td>133.6</td><td>20.2</td></tr></tbody></table>
<figure><img src="image_8.png" /><figcaption>**Fig. 4.** a) $^{53}$Mn/$^{55}$Cr evolution diagram of aqueously-formed fayalite in NWA 3358. Dotted square near the origin is the area showed by b). The excess of $^{53}$Cr correlates with $^{55}$Mn/$^{52}$Cr ratio indicating in situ decay of $^{53}$Mn to $^{53}$Cr. $\delta^{53}\text{Cr} = ((^{53}\text{Cr}/^{52}\text{Cr})_{\text{fayalite}}/(^{53}\text{Cr}/^{52}\text{Cr})_{\text{terrestrial}} - 1) \times 1000$, where $(^{53}\text{Cr}/^{52}\text{Cr})_{\text{terrestrial}} = 0.113459$ (Papanastassiou, 1986). b) Close up of the area near the origin.</figcaption></figure>

## 4. Discussion

With a ($^{53}$Mn/$^{55}$Mn)$_0$ of (5.56 ± 0.44) × 10⁻⁶ NWA 3358 fayalites has distinct higher and more precise $^{53}$Mn/$^{55}$Mn ratio than those for fayalites from previously investigated ordinary chondrites EET 90161 (L3.05) and Vicência (LL3.2) having ($^{53}$Mn/$^{55}$Mn)$_0$ of (4.35 ± 1.23) × 10⁻⁶ and (3.20 ± 0.73) × 10⁻⁶, respectively (Doyle et al., 2015; Keil

et al., 2015). We recalculated the formation ages of previously measured samples using the same age anchors to get comparable values and uncertainties for this work (Table 3). The two commonly used anchors (based on the angrite D'Orbigny (Glavin et al., 2004; McKibbin et al., 2015)) resulted in formation times for the NWA 3358 fayalites of 1.05±0.73 and 1.52±0.94 Ma after CAIs, respectively and therefore possible older than the CI-chondrite Flensburg [2.6 ± 1.0 Ma (Bischoff et al., 2021)]. Unfortunately, the larger uncertainties of the previous measurements resulted in larger formation-time-intervals (Doyle et al., 2015; Keil et al., 2015; Bischoff et al., 2021) and those uncertainties overlap with our new measurements. However, our much more precise $^{53}$Mn/$^{55}$Mn measurement alone indicates that the formation age of the fayalite within NWA 3358 occurred up to one million years earlier than for any other chondritic meteorites analyzed so far and was most likely 1.0–1.5 Ma after CAIs (Table 3; Fig. 5). Only carbonates in Ryugu could have older formation ages of 0.4 ± 0.4 Ma and 1.0 ± 0.8 Ma after CAIs (McCain and Matsuda et al., 2023) but there are strong discrepancies to other measurements on Ryugu with 5.2±1.8 Ma (Yokoyama et al., 2023), 5.2±0.8 Ma (Yokoyama et al., 2022), 4.13±0.62 Ma (Tanaka et al., 2024), and 2.6±1.0 Ma (Nakamura et al., 2022) after CAIs. One reason could be the use of different standard material in the various studies and the same standard with the same RSF would possibly lead to a narrower age range. But at the moment the age of Ryugu is still too vague to compare it with NWA 3358.

The maximum temperature of an asteroid to have reached can be modeled by assuming the accretion time and size of an object. Our thermal modeling shows that the parent body of NWA 3358 had to be larger than 2 km in radius to melt the accreted water-ice but not larger than 6 km, otherwise it would exceed the temperatures where nearly pure fayalite is stable, ~200 °C (Zolotov et al., 2006; Fig. 6). Aqueous alteration of small asteroids of 3–6 km in radius that accreted ~1.0–1.5 Ma after CAIs could explain the formation age of the NWA 3358 fayalite. This accretion age is significantly older than the estimated accretion ages of ordinary chondrite parent asteroids and may correspond to the formation of a first-generation body. Comparable conclusions were drawn from a CAI from the CV chondrite Allende which experienced early aqueous alteration on an earlier formed precursor body, <10 km in size, before it accreted on the CV parent body (Tang et al., 2017).

In some models, initially small parent bodies are challenging to explain, because they argued that asteroids were “born” big (~100 km, Johansen et al., 2014). On the contrary, other models suggested a formation of small bodies; turbulent concentration models show the possibility of 10 km in diameter bodies (Hartlep and Cuzzi, 2022) and the collisional model indicates the formation of 100 m to a few km radius bodies (Kobayashi and Tanaka, 2021). Since these sizes of bodies are large enough to avoid radial inward drifting or migration (Weidenschilling, 1977; Johansen et al., 2014), they could therefore remain in the region where they were formed. Note that the initial body might be a porous body which differs from a compact body as it is in our

<table><caption>**Table 3**
Summary and recalculations of Mn-Cr ages from previous studies using the same parameters.</caption><thead><tr><th>Meteorite (reference)</th><th>Type</th><th>Mineral</th><th>(<sup>53</sup>Mn/<sup>55</sup>Mn)<sub>0</sub></th><th>2σ</th><th>Δt<sub>CAI</sub> Ma (G)</th><th>Δt<sub>CAI</sub> Ma (M)</th></tr></thead><tbody><tr><td>NWA 3358 (this study)</td><td>H3.1</td><td>fayalite</td><td>5.41E-06</td><td>4.31E-07</td><td>1.05<sup>+0.73</sup><sub>-0.76</sub></td><td>1.52<sup>+0.94</sup><sub>-0.96</sub></td></tr><tr><td>EET 90161 (D)</td><td>L3.05</td><td>fayalite</td><td>4.35E-06</td><td>1.23E-06</td><td>2.36<sup>+1.65</sup><sub>-2.09</sub></td><td>2.83<sup>+1.86</sup><sub>-2.29</sub></td></tr><tr><td>Vicência (K)</td><td>LL3.2</td><td>fayalite</td><td>3.20E-06</td><td>7.30E-07</td><td>4.00<sup>+1.41</sup><sub>-1.70</sub></td><td>4.47<sup>+1.63</sup><sub>-1.90</sub></td></tr><tr><td>MAC 88107 (D)</td><td>CO3.0-3.1</td><td>fayalite</td><td>2.58E-06</td><td>2.10E-07</td><td>5.15<sup>+0.73</sup><sub>-0.77</sub></td><td>5.62<sup>+0.95</sup><sub>-0.97</sub></td></tr><tr><td>A-881317 (D)</td><td>CV3</td><td>fayalite</td><td>3.07E-06</td><td>4.40E-07</td><td>4.22<sup>+1.03</sup><sub>-1.14</sub></td><td>4.69<sup>+1.24</sup><sub>-1.34</sub></td></tr><tr><td>Flensburg (B)</td><td>C1</td><td>carbonate</td><td>4.43E-06</td><td>8.00E-07</td><td>2.26<sup>+1.20</sup><sub>-1.36</sub></td><td>2.73<sup>+1.41</sup><sub>-1.58</sub></td></tr><tr><td>Murchison (F)</td><td>CM</td><td>carbonate</td><td>2.66E-06</td><td>7.90E-07</td><td>4.98<sup>+1.70</sup><sub>-2.20</sub></td><td>5.46<sup>+1.92</sup><sub>-2.40</sub></td></tr><tr><td>Y-791198 (F)</td><td>CM</td><td>carbonate</td><td>3.40E-06</td><td>7.40E-07</td><td>3.67<sup>+1.37</sup><sub>-1.63</sub></td><td>4.15<sup>+1.58</sup><sub>-1.82</sub></td></tr><tr><td>ALH 83100 (F)</td><td>CM</td><td>carbonate</td><td>2.79E-06</td><td>4.70E-07</td><td>4.73<sup>+1.15</sup><sub>-1.30</sub></td><td>5.20<sup>+1.36</sup><sub>-1.50</sub></td></tr><tr><td>Sayama (F)</td><td>CM</td><td>carbonate</td><td>3.38E-06</td><td>4.00E-07</td><td>3.70<sup>+0.91</sup><sub>-0.99</sub></td><td>4.18<sup>+1.13</sup><sub>-1.19</sub></td></tr></tbody></table>

References: B = Bischoff et al., 2021; D = Doyle et al., 2015; F = Fujiya et al. 2012; G = Glavin et al., 2004; K = Keil et al., 2015; M = McKibbin et al., 2015.
<figure><img src="image_9.png" /><figcaption>**Fig. 5.** Histogram with 0.1 Ma steps of $^{26}$Al-$^{26}$Mg ages of 113 different ferromagnesian chondrules from unequilibrated ordinary chondrites (Kita et al., 2000; Villeneuve et al., 2009; Bollard et al., 2019; Pape et al., 2019; Siron et al., 2022). The inferred ($^{53}$Mn/$^{55}$Mn)$_{0}$ of the angrite D'Orbigny were used for age calculation: Inferred accretion ages of NWA 3358 fayalites of (a) $1.05_{-0.76}^{+0.73}$ after CAIs, calculated with the D'Orbigny anchor from Glavin et al. (2004) and (b) of $1.52_{-0.96}^{+0.94}$ after CAIs with the D'Orbigny anchor from McKibbin et al. (2015). Blue diamond is age of fayalite formation in NWA 3358 (this study); black diamonds are Mn-Cr ages of fayalites from ordinary chondrites and orange diamonds are Mn-Cr ages of carbonates from various carbonaceous chondrites reported previously (see Table 1). Ryugu samples are not included based on the age variations from <1.8 Ma (McCain and Matsuda et al., 2023) to $5.2_{-0.7}^{+0.8}$ (Yokoyama et al., 2022) and $5.2_{-1.4}^{+1.8}$ (Yokoyama et al., 2023). Uncertainties are 2σ.</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>**Fig. 6.** Maximum temperature as a function of accretion time of H chondrite-like body. Each line represents a parent body of different radius.</figcaption></figure>

sample today. On a porous body, the formation of fayalite and other aqueous alteration products have already taken place (Metzler et al., 1992; Bischoff, 1998). Over time, the loosely packed body could grow by accreting more material and result in a larger and compact body due to its gravity. However, the thermal conductivity of porous material decreases from the non-porous one (e.g., Yomogida and Matsui, 1981; Henke et al., 2012; Neumann et al., 2021); the porous body tends to reach a higher temperature than the consolidated body as we modeled here. This implies that our estimated size can be the upper limit. We need to mention that the phase change of water-ice within the porous body and the shrinking of the body due to the compaction could result in

the complicated process of aqueous alteration within the porous body. We also note that this process and the porosity of the parent body might change the water/rock mass ratio, which we assume 0.2 in this work. A further model of considering the effect of porosity might be necessary.

The estimated early accretion of the NWA 3358 first-generation body provides a mechanism by which refractory inclusions and also early-formed chondrules were protected from spiraling toward the Sun. A thin section of NWA 3358 studied, 3.27 cm$^2$, contains with 52 CAIs and AOAs comprising 0.14 % of its surface area, by far the highest abundance of refractory inclusions within a NC-chondrite (modal abundance of CAIs in UOCs is estimated to be ~0.009 area%; Dunham et al., 2023). The high refractory inclusion abundances and our calculated formation time of NWA 3358 fits very well to the modeled CAI abundances of 0.36–0.02 wt.% of an early formed body between 1.0 and 1.25 Ma after CAIs in a distance of 2 AU to the Sun (Desch et al., 2018). However, our work cannot constrain the formation location of NWA 3358 parent body. Given that it contained water-ice, its formation location could be also around the snow line which might be beyond 2 AU.

Such early formed bodies could be disrupted by later impacts, and release CAIs, chondrules, fragments, and clasts to the solar nebula; this material could be subsequently converted to chondrules and/or be accreted into chondrite parent bodies (Johansen et al., 2015; Tang et al., 2017; Spitzer et al., 2020). As NWA 3358 contains such a high amount of refractory inclusions compared to other NC chondrites, just a part of the inclusions has to survive to provide sufficient amounts of CAIs and AOAs for later formed bodies. Such a process would of course lead to stronger fragmentation of refractory inclusions, resulting in smaller sizes, and indeed, the average diameter of CAIs within NWA 3358 is with 85 µm (94 µm if AOAs are also included) nearly 2 × higher than the mean diameter of 46 µm of CAIs for NC chondrites (Dunham et al., 2023).
Furthermore, those refractory inclusions and other components could have already been affected by parent body alteration on their individual first-generation bodies and this can explain for example a CAI from a unequilibrated ordinary chondrite (LL3.00) whose O-isotope composition is affected by aqueous alteration (Russell et al., 2016).

Disruption and re-accretion of first-generation bodies may also explain the observed range of $^{26}$Al-$^{26}$Mg chondrule ages within a chondrite group (Nagashima et al., 2018; van Kooten et al., 2019). The $^{26}$Al-$^{26}$Mg dating indicates that chondrule formation rate increased ~ 2 Ma after the formation of CAIs (Pape et al., 2019; Siron et al., 2022). We hypothesize that most of the earlier-formed chondrules released during dispersal of first-generation bodies were reprocessed during subsequent chondrule-forming events resulting in underestimated abundances of old chondrules. Chondrule/matrix ratio in NWA 3358 is ~1.5, which is low compared to the majority of other H-chondritic meteorites, up to 4 (Scott et al., 2006), supporting an earlier accretion time for NWA 3358: chondrule/matrix ratio in later-accreted chondritic parent bodies is expected to be higher than in first-generation bodies.

Another consequence of such an early-formed chondritic parent body would be that refractory material like CAIs and early-formed chondrules were not exposed to the solar nebula alteration for millions of years, limiting the time that O-isotopic exchange might occur on them as freely-floating grains. This makes it even more unlikely that, e.g. the mineralogically controlled O-isotopic heterogeneity within CAIs and chondrules, measured in chondritic meteorites of petrological type >3.0, was caused by an O-isotopic exchange within the nebula and the process of an aqueous fluid-rock interaction on their parent bodies is a more likely scenario (Krot, 2019; Ebert et al., 2020, 2022, 2024).

Furthermore, various components likely underwent parent body alteration within the first-generation bodies before they accreted on the new body. In this case, the newly accreted asteroids would contain material and components that do not fit to the meteorites' history and would stand in petrological contrast to neighboring components (considering the brecciation within a sample itself). For example, various clasts in the LL3.1 chondrite Krymka differ from the host meteorite (e.g., contain higher CAI abundances), most likely originated from a previously accreted parent body (Semenenko et al., 2001). After the first-generation bodies were destroyed by impacts, these primary clasts became coated with fine-grained rims consisting of material from the solar nebula, which can only be collected by freely-floating material. A similar conclusion was drawn for aqueous hydrous phases, accretionary dust rimming chondrules, CAIs, and TCI (tochilinite-cronstedtite intergrowth)-objects in CM chondrites which should have resulted from the earlier destruction of loosely-compacted, aqueously-altered precursor planetesimals (Metzler et al., 1992; Bischoff, 1998). An early-formed LL or CM parent body can explain all these features, and NWA 3358 is the proof that such early chondritic bodies did exist.

Yet, the H3.1 chondrite NWA 3358 was not heated above ~250-300 °C and therefore does not represent a seed for accretion of a final H-chondrite parent body that reached peak metamorphic temperature of ~900 °C in its center (Huss et al., 2006). We suggest that NWA 3358 represents a fragment of a first-generation H chondrite-like body that formed in close proximity to the final H chondrite parent and accreted to its peripheral part ~ 1 Ma later. This outcome of smaller bodies surviving the accretion of a dominant body has also been estimated by the existing accretion models (e.g. Ormel et al., 2010). The presence of protoplanets and planetesimals in the solar nebula governs the survivability of smaller first-generation bodies. At the early formation stage of protoplanets, larger planetesimals sweep up smaller bodies, leading to runaway growth (Kokubo and Ida, 1996; Ormel et al., 2010). Since this process is self-limiting, the larger bodies would become large enough to stir up the eccentricities and inclinations of the smaller ones: There would be an "oligarchy" of larger bodies and a swarm of smaller bodies (Kokubo and Ida, 1998). Those smaller bodies were likely affected by later collisions and/or were accreted by the larger ones over longer timescales (Kokubo and Ida, 1996). As a result, only a small number of

smaller first-generation bodies likely survived during the formation period of protoplanets. Thus, NWA 3358 represents a smaller and early-formed chondritic body that was never incorporated into a larger one, preserving its pristine and extraordinary character.

## 5. Conclusions

(1) NWA 3358 is characterized by a chondrule/matrix ratio of ~1.5, which is low compared to the majority of other H-chondritic meteorites (up to 4). Furthermore, the meteorite is characterized by an extremely high amount of refractory inclusions (42 CAIs and 10 AOAs) within one thin section, comprising 0.14 % of its area. This is the highest abundance of refractory inclusions among non-carbonaceous chondrites containing on average ~0.009 area % of refractory inclusions.

(2) The aqueously-formed fayalites ($Fa_{>99}$) in NWA 3358 have the inferred initial $^{53}$Mn/$^{55}$Mn ratio of (5.56 ± 0.44) × 10$^{-6}$. This is the highest measured $^{53}$Mn/$^{55}$Mn value for secondary minerals in chondrites resulting in formation times for the NWA 3358 fayalites of $1.05_{-0.76}^{+0.73}$ and $1.52_{-0.96}^{+0.94}$ Ma after CAIs depending on the used anchor (Glavin et al., 2004; McKibbin et al., 2015, respectively).

(3) Thermal modeling indicates that the first-generation of an H chondrite parent body, ~6–12 km in diameter, that accreted within 1.0 Ma after formation of CAIs can explain the presence of such old fayalites within the matrix of NWA 3358. Such an early formed first-generation body would fill the gap of ~2 Ma between CAIs and the final chondrite parent bodies and provides a possible mechanism of CAIs/AOAs storage in the inner protoplanetary disk.

## CRediT authorship contribution statement

**Samuel Ebert:** Writing – review & editing, Writing – original draft, Project administration, Methodology, Funding acquisition, Formal analysis, Data curation, Conceptualization. **Kazuhide Nagashima:** Methodology, Investigation, Formal analysis, Data curation. **Alexander N. Krot:** Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis. **Shigeru Wakita:** Writing – review & editing, Investigation, Formal analysis, Data curation. **Jean-Alix Barrat:** Writing – review & editing, Formal analysis, Data curation. **Addi Bischoff:** Writing – review & editing, Resources.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Data availability

All used data are available in the manuscript and Supplementary Material.

## Acknowledgments

We thank Ulla Heitmann (Münster) for sample preparation, Thorsten Grund for the technical assistance on the SEM, and Celeste Brennecka for writing support. We would also like to thank Olivier Mousis for his careful editing and two anonymous reviewers who provided very helpful comments on the manuscript. Numerical computations for the thermal modeling were carried out on the PC cluster and analysis servers at the Center for Computational Astrophysics of the National Astronomical Observatory of Japan. We acknowledge support from the Open Access
Publishing Fund of University of Muenster. This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - project numbers 413893359 and 463342295. ANK was supported by NASA Emerging Worlds grant 80NSSC23K0253.

## Supplementary materials

Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.epsl.2024.119010.

## References

Barrat, J.-A., Zanda, B., Moynier, F., Bollinger, C., Liorzou, C., Bayon, G., 2012. Geochemistry of CI chondrites: major and trace elements, and Cu and Zn isotopes. Geochim. Cosmochim. Acta 83, 79-92.

Barrat, J.-A., Dauphas, N., Gillet, P., Bollinger, C., Etoubleau, J., Bischoff, A., Yamaguchi, A., 2016. Evidence from Tm anomalies for non-CI refractory lithophile element proportions in terrestrial planets and achondrites. Geochim. Cosmochim. Acta 176, 1-17.

Bischoff, A., 1998. Aqueous alteration of carbonaceous chondrites: evidence for preaccretionary alteration—A review. Meteorit. Planet. Sci. 33, 1113-1122.

Bischoff, A., Keil, K., 1983. Ca-Al-rich chondrules and inclusions in ordinary chondrites. Nature 303, 588-592.

Bischoff, A., Keil, K., Stöffler, D., 1985. Perovskite-hibonite-spinel-bearing inclusions and Al-rich chondrules and fragments in enstatite chondrites. Chem. Erde 44, 97-106.

Bischoff, A., et al., 2021. The old, unique C1 chondrite Flensburg—Insight into the first processes of aqueous alteration, brecciation, and the diversity of water-bearing parent bodies and lithologies. Geochim. Cosmochim. Acta 293, 142-186.

Bollard, J., Kawasaki, N., Sakamoto, N., Olsen, M., Itoh, S., Larsen, K., Wielandt, D., Schiller, M., Connelly, J.N., Yurimoto, H., Bizzarro, M., 2019. Combined U-corrected Pb-Pb dating and $^{26}$Al-$^{26}$Mg systematics of individual chondrules—Evidence for a reduced initial abundance of $^{26}$Al amongst inner solar system chondrites. Geochim. Cosmochim. Acta 260, 62-83.

Brearley, A.J., 2006. The action of water. In: Lauretta, D.S., McSween Jr., H.Y. (Eds.), Meteorites and the Early Solar System II. University of Arizona Press, pp. 584-5624.

Brearley, A.J., Krot, A.N., 2013. Metasomatism in the early solar system: the record from chondritic meteorites in *metasomatism and the chemical transformation of rock*. In: Harlov, D., Austrheim, H. (Eds.), Lecture Notes in Earth System Sciences. Springer-Verlag, Berlin and Heidelberg, Germany, pp. 659-789.

Brennecka, G.A., Wadhwa, M., 2012. Uranium isotope compositions of the basaltic anglite meteorites and the chronological implications for the early solar system. PNAS 109 (2012), 9299-9303.

Burkhardt, C., Dauphas, N., Hans, U., Bourdon, B., Kleine, T., 2019. Elemental and isotopic variability in solar system materials by mixing and processing of primordial disk reservoirs. Geochim. Cosmochim. Acta 261, 145-170.

Ciesla, F.J., 2007. Outward transport of high-temperature materials around the midplane of the solar nebula. Science 318, 613-615.

Clayton, R.N., Mayeda, T.K., Goswami, J.N., Olsen, E.J., 1991. Oxygen isotope studies of ordinary chondrites. Geochim. Cosmochim. Acta 55, 2317-2337.

Coath, C.D., Steele, R.C.J., Lunnon, W.F., 2013. Statistical bias in isotope ratios. J. Anal. At. Spectrom. 28, 52-58.

Connelly, J.N., Bizzarro, M., Krot, A.N., Nordlund, Å., Wielandt, D., Ivanova, M.A., 2012. The absolute chronology and thermal processing of solids in the solar protoplanetary disk. Science 338, 651-655.

Desch, S.J., Kalyaan, A., Alexander, C.M.O'D., 2018. The effect of Jupiter's formation on the distribution of refractory elements and inclusions in meteorites. Astrophys. J. Suppl. Ser. 238, 11.

Doyle, P.M., Jogo, K., Nagashima, K., Krot, A.N., Wakita, S., Ciesla, F.J., Hutcheon, I.D., 2015. Early aqueous activity on the carbonaceous and ordinary chondrite parent asteroids recorded by secondary fayalite. Nat. Commun. 6, 1-10.

Doyle, P.M., Jogo, K., Nagashima, K., Huss, G.R., Krot, A.N., 2016. Mn-Cr relative sensitivity factor in ferromagnesian olivines defined for SIMS measurements with a Cameca Ims-1280 ion microprobe: implications for dating secondary fayalite. Geochim. Cosmochim. Acta 174, 102-121.

Dunham, E.T., Sheikh, A., Opara, D., Matsuda, N., Liu, M.-C., McKeeegan, K.D., 2023. Calcium-aluminum-rich inclusions in non-carbonaceous chondrites: abundances, sizes, and mineralogy. Meteorit. Planet. Sci. 58, 643-671.

Ebert, S., Render, J., Brennecka, G.A., Burkhardt, C., Bischoff, A., Gerber, S., Kleine, T., 2018. Ti isotopic evidence for a non-CAI refractory component in the inner solar system. Earth Planet. Sci. Lett. 511, 44-54.

Ebert, S., Patzek, M., Lentfort, S., Bischoff, A., 2019. Accretion of differentiated achondritic and aqueously altered chondritic materials in the early solar system—Significance of an igneous fragment in the CM chondrite NWA 12651. Meteorit. Planet. Sci. 54, 2985-2995.

Ebert, S., Nagashima, K., Krot, A.N., Bischoff, A., 2020. Oxygen-isotope heterogeneity in the Northwest Africa 3358 (H31.) refractory inclusions—fluid-assisted isotopic exchange on the H-chondritic parent body. Geochim. Cosmochim. Acta 282, 98-112.

Ebert, S., Nagashima, K., Bischoff, A., Berndt, J., Krot, A.N., 2022. Mineralogy, petrology, and oxygen isotopic compositions of aluminum-rich chondrules from unequilibrated ordinary and the Dar al Gani 083 (CO3.1) chondrite. Geochim. Cosmochim. Acta 336, 448-468.

Ebert, S., Nagashima, K., Krot, A.N., Patzek, M., Bischoff, A., 2024. Oxygen isotopic variation in the CAI-forming region recorded by a single refractory inclusion from the CO3.1 carbonaceous chondrite Dar al Gani 083. Astrophys. J. 966, 10.

Fujiya, W., Sugiura, N., Hotta, H., Ichimura, K., Sano, Y., 2012. Evidence for the late formation of hydrous asteroids from young meteoritic carbonates. Nat. Commun. 3, 1-6.

Glavin, D.P., Kubny, A., Jagoutz, E., Lugmair, G.W., 2004. Mn-Cr isotope systematics of the D'Orbigny angrite. Meteorit. Planet. Sci. 39, 693-700.

Hartlep, T., Cuzzi, J.N., 2022. Cascade model for planetesimal formation by turbulent clustering. Astrophys. J. 892, 120.

Haugbølle, T., Weber, P., Wielandt, D.P., Benítez-Llambay, P., Bizzarro, M., Gressel, O., Pessah, M.E., 2019. Probing the Protosolar disk using dust filtering at gaps in the early solar system. Astron. J. 158, 55.

Henke, S., Gail, H.-P., Trieloff, M., Schwarz, W.H., Kleine, T., 2012. Thermal evolution and sintering of chondritic planetesimals. Astron. Astrophys. 537, A45.

Hezel, D.C., Russell, S.S., Ross, A.J., Kearsley, A.T., 2008. Modal abundances of CAIs: implications for bulk chondrite element abundances and fractionations. Meteorit. Planet. Sci. 43, 1879-1894.

Huss, G.R., Rubin, A.E., Grossmann, J.N., 2006. Thermal metamorphism in chondrites. In: Lauretta, D.S., McSween Jr., H.Y. (Eds.), Meteorites and the Early Solar System II. University of Arizona Press, pp. 567-586.

Hutcheon, I.D., Hutchison, R., 1989. Evidence from the Semarkona ordinary chondrite for $^{26}$Al heating of small planets. Nature 337, 238-241.

Johansen, A., Jacquet, E., Cuzzi, J.N., Morbidelli, A., Gounelle, M., 2014. The multifaceted planetesimal formation process. In: Beuther, H., Klessen, R., Dullemond, C., Henning, Th. (Eds.), Protostars and Planets VI. University of Arizona Press, pp. 547-570.

Johansen, A., Low, M.-M.M., Lacerda, P., Bizarro, M., 2015. Growth of asteroids, planetary embryos, and Kuiper belt objects by chondrule accretion. Sci. Adv. 1, 1500109.

Keil, K., et al., 2015. The Vicência meteorite fall: a new unshocked (S1) weakly metamorphosed (3.2) LL chondrite. Meteorit. Planet. Sci. 50, 1089-1111.

Kerraouch, I., Bischoff, A., Zolensky, M.E., Trieloff, M., Krot, A.N., Nagashima, K., Vollmer, C., Patzek, M., Ebert, S., Radić, D., Treiman, A., Rubin, A.E., 2022. Discovery of hydrated clasts with very high abundance of ferromagnesian $^{16}$O-rich olivine: inner or outer solar system origin? Meteorit. Planet. Sci. 57, #6246.

Kita, N.T., Nagahara, H., Togashi, S., Morishita, Y., 2000. A short duration of chondrule formation in the solar nebula: evidence from $^{26}$Al in Semarkona ferromagnesian chondrites. Geochim. Cosmochim. Acta 64, 3913-3922.

Kobayashi, H., Tanaka, H., 2021. Rapid formation of gas-giant planets via collisional coagulation from dust grains to planetary cores. Astrophys. J. 922, 16.

Kokubo, E., Ida, S., 1996. On runaway growth of planetesimals. Icarus 123, 180-191.

Kokubo, E., Ida, S., 1998. Oligarchic growth of protoplanets. Icarus 131, 171-178.

Krot, A.N., 2019. Refractory inclusions in carbonaceous chondrites: Records of early solar system processes. Meteorit. Plan. Sci. 54, 1647-1691.

Krot, A.N., Hutcheon, I.D., Brearley, A.J., Pravdivtseva, O.V., Petaev, M.I., Hohenberg, C. M., 2006. Timescales for secondary alteration of chondritic meteorites. In: Lauretta, D., McSween, H. (Eds.), Meteorites and The Early Solar System II. University of Arizona Press, pp. 525-555.

Kruijer, T.S., Touboul, M., Fischer-Gödde, M., Bermingham, K.R., Walker, R.J., Kleine, T., 2014. Protracted core formation and rapid accretion of protoplanets. Science 344, 1150-1154.

Kruijer, T.S., Burkhardt, C., Budde, G., Kleine, T., 2017. Age of Jupiter inferred from the distinct genetics and formation times of meteorites. PNAS 114, 6712-6716.

Kruijer, T.S., Kleine, T., Borg, L.E., 2020. The great isotopic dichotomy of the early solar system. Nat. Astr. 4, 32-40.

Lee, T., Papanastassiou, D.A., Wasserburg, G.J., 1976. Correlated O and Mg isotopic anomalies in Allende inclusions: II. Magnesium. Geophys. Res. Lett. 3, 109-112.

McCain, K., Matsuda, N., et al., 2023. Early fluid activity on Ryugu inferred by isotopic analyses of carbonates and magnetite. Nat. Astron. 7, 309-317.

McKeegan, K.D., Chaussidon, M., Robert, F., 2000. Incorporation of short-lived $^{10}$Be in a calcium-aluminum-rich inclusion from the Allende meteorite. Science 289, 1334-1337.

McKibbin, S.J., Ireland, T.R., Amelin, Y., Holden, P., 2015. Mn-Cr dating of Fe- and Ca-rich olivine from ‘quenched’ and ‘plutonic’ anglite meteorites using secondary ion mass spectrometry. Geochim. Cosmochim. Acta 157, 13-27.

Metzler, K., Bischoff, A., Stöffler, D., 1992. Accretionary dust mantles in CM chondrites: Evidence for solar nebula processes. Geochim. Cosmochim. Acta 56, 2873-2897.

Nagashima K., Kita N.T., Luu T.-H., 2018. 26Al-26Mg systematics of chondrules. In Chondrules, S.S., Russell, H.C. Jr., Connolly, A.N. Krot, (Eds.), Cambridge University Press, 2018, pp. 247-275.

Nakamura, E., et al., 2022. On the origin and evolution of the asteroid Ryugu: a comprehensive geochemical perspective. Proc. Jpn. Acad., Ser. B 98, 227-282.

Neumann, W., Grott, M., Trieloff, M., Jaumann, R., Biele, J., Hamm, M., Kührt, E., 2021. Microporosity and parent body of the rubble-pile NEA (162173) Ryugu. Icarus 358, 114166.

Ogliore, R.C., Huss, G.R., Nagashima, K., 2011. Ratio estimation in SIMS analysis. Nucl. Instr. Meth. Phys. Res. B 269, 1910-1918.

Ormel, W., Dullemond, C.P., Spaans, M., 2010. Accretion among preplanetary bodies: the many faces of runaway growth. Icarus 210, 507-538.

Papanastassiou, D.A., 1986. The identification of meteorite inclusions with isotope anomalies. Astrophys. J. 308, L27-L30.

Pape, J., Mezger, K., Bouvier, A.-S., Baumgartner, L.P., 2019. Time and duration of chondrule formation: constraints from $^{26}$Al-$^{26}$Mg ages of individual chondrules. Geochim. Cosmochim. Acta 244, 416-436.
Rout, S.S., Bischoff, A., 2008. Ca, Al-rich inclusions in Rumuruti (R) chondrites. Meteorit. Planet. Sci. 43, 1439–1464.

Russell, S.S., Itoh, S., Salge, T., Higashi, Y., Kawasaki, N., Sakamoto, N., 2016. A CAI in the highly unequilibrated ordinary chondrite Northwest Africa 8276: implications for CAI formation and processing. In: Lunar and Planetary Science Conference, 47. #1989.

Scott, E.R.D., Love, S.G., Krot, A.N., 2006. Formation of chondrules and chondrites in the protoplanetary disk. In: Hewins, R.H., Jones, R.H., Scott, E.R.D. (Eds.), Chondrules and the Protoplanetary Disk. Cambridge University Press, pp. 87–96.

Semenenko, V.P., Bischoff, A., Weber, I., Perron, C., Girich, A.L., 2001. Mineralogy of fine-grained material in the Krymka (LL3.1) chondrite. Meteorit. Planet. Sci. 36, 1067–1085.

Siron, G., Fukuda, K., Kimura, M., Kita, N.T., 2022. High precision <sup>26</sup>Al-<sup>26</sup>Mg chronology of chondrules in unequilibrated ordinary chondrites: evidence for restricted formation ages. Geochim. Cosmochim. Acta 324, 312–345.

Spitzer, F., Burkhardt, C., Budde, G., Kruijer, T.S., Morbidelli, A., Kleine, T., 2020. Isotopic evolution of the inner solar system inferred from molybdenum isotopes in meteorites. Astrophys. J. Lett. 898, L2.

Tanaka, R., et al., 2024. Unraveling the Cr isotopes of Ryugu: an accurate aqueous alteration age and the least thermally processed solar system material. Astrophys. J. 965, 52.

Tang, H., Liu, M.-C., McKeegan, K.D., Tissot, F.L.H., Dauphas, N., 2017. In situ isotopic studies of the U-depleted Allende CAI curious Marie: pre-accretionary alteration and the co-existence of <sup>26</sup>Al and <sup>36</sup>Cl in the early solar nebula. Geochim. Cosmochim. Acta 207, 1–18.

Telus, M., Huss, G.R., Ogliore, R.C., Nagashima, K., Tachibana, S., 2012. Recalculation of data for short-lived radionuclide systems using less-biased ratio estimation. Meteorit. Planet. Sci. 47, 2013–2030.

Trinquier, A., Birck, J.-L., Allègre, C.J., Göpel, C., Ulfbeck, D., 2008. <sup>53</sup>Mn-<sup>53</sup>Cr systematics of the early solar system revisited. Geochim. Cosmochim. Acta 72, 5146–5163.

Van Kooten, E.M., Moynier, F., Agranier, A., 2019. A unifying model for the accretion of chondrules and matrix. PNAS 116, 18860–18866.

Villeneuve, J., Chaussidon, M., Liboure!, G., 2009. Homogeneous distribution of <sup>26</sup>Al in the solar system from the Mg isotopic composition of chondrules. Science 325, 985–988.

Wakita, S., Sekiya, M., 2011. Thermal evolution of icy planetesimals in the solar nebula. Earth Planets Space 63, 1193–1206.

Weidenschilling, S.J., 1977. Aerodynamics of solid bodies in the solar nebula. MNRAS 180, 57–70.

Weidenschilling, S.J., 2019. Accretion of the asteroids: implications for their thermal evolution. Meteorit. Planet. Sci. 54, 1115–1132.

Yang, L., Ciesla, F.J., 2012. The effects of disk building on the distributions of refractory materials in the solar nebula. Meteorit. Planet. Sci. 47, 99–119.

Yokoyama, T., et al., 2022. Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites. Science 379, eabn7850.

Yokoyama, T., et al., 2023. Water circulation in Ryugu asteroid affected the distribution of nucleosynthetic isotope anomalies in returned sample. Sci. Adv. 9, eadi7048.

Yomogida, K., Matsui, T., 1981. Physical properties of some Antarctic meteorites. Mem. Natl. Inst. Polar Res., Special Issue 20, 384–394.

Zolensky M.E., Krot A.N., Benedix G., 2008. Record of low-temperature alteration in asteroids. In *Oxygen in the Solar System*, G.J. MacPherson, (Ed.), Rev. Mineral. Geochem. vol. 68, pp. 429–462.

Zolotov, M.Y., Mironenko, M.V., Shock, E.L., 2006. Thermodynamic constraints on fayalite formation on parent bodies of chondrites. Meteorit. Planet. Sci. 41, 1775–1796.