# Formation of chondrule fine-grained rims from local nebular reservoirs

Gabriel A. Pinto, Yves Marrocchi, Emmanuel Jacquet, Felipe Olivares

► To cite this version:

Gabriel A. Pinto, Yves Marrocchi, Emmanuel Jacquet, Felipe Olivares. Formation of chondrule fine-grained rims from local nebular reservoirs. Meteoritics and Planetary Science, 2022, 57 (5), pp.1004-1017. 10.1111/maps.13812. insu-03712867

HAL Id: insu-03712867

https://insu.hal.science/insu-03712867v1

Submitted on 20 Aug 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
The
Meteoritical
Society

Meteoritics & Planetary Science 57, Nr 5, 1004–1017 (2022)

doi: 10.1111/maps.13812

# Formation of chondrule fine-grained rims from local nebular reservoirs

Gabriel A. PINTO<sup>1,2</sup>, Yves MARROCCHI<sup>2</sup>, Emmanuel JACQUET<sup>3</sup>, and Felipe OLIVARES<sup>1</sup>

<sup>1</sup>Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copayapu 485, Copiapó, Chile

<sup>2</sup>Université de Lorraine, CNRS, CRPG, UMR 7358, Vandœuvre-lès-Nancy 54501, France

<sup>3</sup>Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d'Histoire naturelle, Sorbonne Université, CNRS, CP52, 57 rue Cuvier, Paris 75005, France

*Corresponding author. E-mail: gabriel.pinto@univ-lorraine.fr

*(Received 14 September 2021; revision accepted 08 March 2022)

**Abstract**–Chondrules are commonly surrounded by fine-grained rims (FGRs) whose origin remains highly debated; both nebular and parent body settings are generally proposed. Deciphering their origin, however, is of fundamental importance as they could clarify the matrix–chondrule relationship and thus constrain the formation and transport conditions of chondrules in the circumsolar disk. Here, we report a systematic survey of FGRs in CO, CM, CV, and CR chondrites; we compare (i) the thickness of FGRs to the size of their host chondrules and (ii) the frequency of FGRs to the modal abundance of matrix in the respective host chondrites. Although FGRs show textural variations depending on the petrologic type of the considered chondrites, our data show a positive correlation between apparent rim thickness and the radius of the host chondrule in all chondrite groups. We also found a positive correlation between the evaluated percentages of rimmed chondrules and the modal abundance of matrix material in the chondrites. We show that this relationship could not result from parent body processes, whether matrix compaction or FGR fragmentation. Therefore, we propose that FGRs were accreted under warm conditions at the end of chondrule-forming events. Our results thus support (i) a nebular origin for FGR, whose abundances are directly related to the abundance of available dust in regions of chondrite accretion; and (ii) the accretion of chondrites from locally formed chondrules and matrix, suggesting limited radial transport in the protoplanetary disk.

## INTRODUCTION

Chondritic meteorites are fragments of asteroids that escaped melting and differentiation, and have thus remained largely unchanged since their formation in the early solar system (e.g., Piani et al., 2020; Scott & Krot, 2014). They comprise particles formed at high temperatures during the early evolution of the protoplanetary disk, such as refractory inclusions and chondrules, within a fine-grained matrix formed at low temperatures. Chondrules are ferromagnesian quasi-spheroids formed by the crystallization of magma droplets through a still-elusive high-temperature event (Connolly & Jones, 2016). To explain their formation, chondrules are considered to represent either (i) nebular products arising from the melting of early condensates (Marrocchi, Villeneuve, et al., 2018; Marrocchi et al.,

2019; Ruzicka et al., 2007), for example, during the passage of bow shocks produced by planetesimals on eccentric orbits (Morris et al., 2012), or (ii) residues of protoplanet collisions (Johnson et al., 2015; Libourel & Krot, 2007). To constrain these models, it is critical to understand the relationship between chondrules and matrix. For instance, all chondrites, except the CI group, experienced chemical fractionation involving refractory (e.g., chondrules) and volatile (e.g., matrix) elements. This might reflect spatial or temporal heterogeneities of chondrite components’ formation into different reservoirs. One possible scenario is the two-component model (e.g., Anders, 1964; Zanda et al., 2006, 2018), which considers that chondrules and matrix are unrelated, for example, they formed in outer and inner regions of the disk, respectively (or, in impact scenarios, by collisions of planetary bodies at different
heliocentric distance and were subsequently mixed in varying proportions within the disk). Other researchers favor a common origin for chondrules and matrix in a closed reservoir, with elemental exchanges between the coarse- and fine-grained components leading to a complementary relationship between matrix and chondrule compositions (e.g., Goldberg et al., 2015; Hezel et al., 2018; Palme et al., 2015); this model considers that localized heating events produced chondrules from nebular dust.

To solve this enigma, further insights into the matrix-chondrule relationship could be gleaned from an additional petrographic component, intermediate between chondrules and matrix: chondrule fine-grained rims (FGRs). In various chondrite groups, chondrules are armored by FGRs, which are distinguished from the surrounding matrix (which will be called “intercomponent matrix,” or ICM) by their texture (i.e., grain size, compaction, porosity; e.g., MacPherson et al., 1985; Zanetta et al., 2021), mineralogy (Brearley, 1993; Zanetta et al., 2021), and/or presolar grain abundance (Leitner et al., 2016, 2019). FGRs are also observed around refractory inclusions, isolated olivine grains, and Fe-Ni metal beads (Brearley, 1993; Hanna & Ketcham, 2018; Jacquet et al., 2021; Lauretta et al., 2000; Simon et al., 2018; Zanetta et al., 2021). Although numerous studies have focused on the mineralogical, chemical, and isotopic characteristics of FGRs (Brearley, 1993; Cosarinsky et al., 2008; Friend et al., 2018; Huss et al., 2005; Lauretta & Buseck, 2003; MacPherson et al., 1985; Wasson & Rubin, 2014), their origin remains poorly constrained and no consensus has yet arisen. One hypothesis is that FGRs formed early in a nebular environment through the accretion of dust around free-floating chondrules before their incorporation into planetesimals (e.g., Cuzzi, 2004; Hanna & Ketcham, 2018; Liffman, 2019; Liffman & Toscano, 2000; Metzler et al., 1992; Zanetta et al., 2021). Alternatively, FGRs may have formed during parent body evolution through compaction or secondary processes such as fluid and/or thermal alteration, which would have induced pervasive modification at the chondrule-matrix boundary (e.g., Brearley & Krot, 2012; Sears et al., 1993; Takayama & Tomeoka, 2012; Tomeoka & Ohnishi, 2010, 2014, 2015; Trigo-Rodriguez et al., 2006). Either way, it must be kept in mind that chondrules and FGRs may have been lithified together *before* the final lithification of the host meteorite where they may have been incorporated as clasts (e.g., Metzler et al., 1992; Takayama & Tomeoka, 2012; Tomeoka & Ohnishi, 2014, 2015).

Most studies of FGRs have focused on the aqueously altered CM carbonaceous chondrites due to the high abundances of FGRs in these meteorites. Deciphering the

broader origin of FGRs thus requires that they be studied in other chondrite groups, particularly the least aqueously and thermally altered CO carbonaceous chondrites (Bonal et al., 2007, 2016; Marrocchi, Bekaert, et al., 2018; McSween, 1977; Pinto et al., 2021; Scott & Jones, 1990; Zolensky et al., 1993). To this end, we here report a systematic survey of FGRs in CO, CM, CV, and CR chondrites; we compare (i) the estimated sizes of FGRs to those of their host chondrules and (ii) the frequency of FGRs to the modal abundance of the matrix in the respective host chondrite group. Based on our results, we discuss the implications on the parent body versus nebular origin of FGRs and the one-reservoir versus two-reservoir origin of chondrules and matrix.

## SAMPLES AND ANALYTICAL METHODS

We studied four polished sections of CO3 chondrites collected in the dense collection areas of El Médano (EM 397, EM 463, and EM 216) and Los Vientos (LoV 123), provided by the Museo del Meteorito (San Pedro de Atacama, Chile), and prepared at Universidad de Atacama (Copiapó, Chile). We also surveyed sections of CM (Paris, section 4029sp1), CV (Vigarano, section Vigarano-P), and CR carbonaceous chondrites (Dar al Gani [DaG] 574, section 3681sp2; Renazzo, section719sp3) provided by the Muséum national d'Histoire naturelle of Paris. The petrography and mineralogy of chondrules and FGRs were determined by optical microscopy, backscattered electron (BSE) imaging, and X-ray compositional mapping. For the latter two, we used (i) a Zeiss Evo MA10 equipped with an Oxford X-MAX N 20 SDD energy-dispersive spectrometer and operating with a 3 nA electron beam accelerated at 15 kV (Universidad de Atacama) and (ii) a JEOL JSM-6510 scanning electron microscope equipped with a Genesis EDX detector using a 3 nA electron beam accelerated at 15 kV (CRPG-CNRS, Nancy, France).

The modal abundances of coarse- and fine-grained components were determined by manual point counting using JMicrovision software (3000 random points). We examined representative areas of 95.9, 134.2, 27, 32.4, and 186.9 mm² in EM 463, EM 397, EM 216, LoV 123, and Vigarano, respectively, and the total section areas of 266, 239, and 58.4 mm² in Paris, Renazzo, and DaG 574, respectively, to calculate the modal abundances and statistics of rimmed chondrules (Table 1). The perimeter of all rimmed chondrules was traced by eye using the open-source software ImageJ (Schindelin et al., 2012). We determined the sizes of individual chondrules without (i.e., particle) and with their surrounding FGRs (i.e., particle + rim) as circle-equivalent diameter (i.e., $d = \sqrt{\frac{\text{pixel area}}{\pi}} \times 2$). The
<table><caption>Table 1. Statistics of completely rimmed chondrules in the studied classes of carbonaceous chondrite.</caption><thead><tr><th>Class</th><th>Meteorite</th><th>Fine-grained particles (%)</th><th>Number of chondrules<sup>a</sup></th><th>Rimmed chondrules (%)</th></tr></thead><tbody><tr><td rowspan="6">CO</td><td>LoV 123</td><td>28 ± 1</td><td>1671</td><td>0.2 ± 0.1</td></tr><tr><td>EM 216</td><td>32 ± 1</td><td>966</td><td>1.9 ± 0.4</td></tr><tr><td>EM 463</td><td>29 ± 1</td><td>2092</td><td>2.0 ± 0.3</td></tr><tr><td>EM 397</td><td>34 ± 1</td><td>868</td><td>2.6 ± 0.5</td></tr><tr><td>Mean</td><td>30.6</td><td></td><td>1.7</td></tr><tr><td>STD</td><td>2.9</td><td></td><td>1.0</td></tr><tr><td rowspan="4">CR</td><td>DaG 574</td><td>34 ± 1</td><td>66</td><td>10.6 ± 4</td></tr><tr><td>Renazzo</td><td>38 ± 1</td><td>177</td><td>12.4 ± 2.7</td></tr><tr><td>Mean</td><td>36.1</td><td></td><td>11.5</td></tr><tr><td>STD</td><td>2.7</td><td></td><td>1.3</td></tr><tr><td rowspan="4">CM</td><td>Paris<sup>b</sup></td><td>66</td><td>78</td><td>80.8</td></tr><tr><td>Paris section 4029sp1</td><td>64 ± 1</td><td>288</td><td>54.9 ± 2.8</td></tr><tr><td>Mean</td><td>65</td><td></td><td>67.8</td></tr><tr><td>STD</td><td>1.5</td><td></td><td>18.3</td></tr><tr><td rowspan="4">CV</td><td>Allende<sup>c</sup></td><td>50</td><td>413</td><td>15</td></tr><tr><td>Vigarano</td><td>39 ± 1</td><td>84</td><td>16.7 ± 4.4</td></tr><tr><td>Mean</td><td>45</td><td></td><td>15.8</td></tr><tr><td>STD</td><td>8.0</td><td></td><td>1.2</td></tr></tbody></table>

In our data, the statistical error of fine-grained material and the percentage of rimmed chondrules were calculated according to the number of counts, assuming a Poisson distribution.

STD, standard deviation.

<sup>a</sup>Minimum numbers of chondrules in the samples.

<sup>b</sup>Zanetta et al. (2021).

<sup>c</sup>Simon et al. (2018).

apparent rim thickness was calculated as half of the difference between the two diameters. The FGR-matrix boundaries were identified after their sharpness, the change in tonality (FGR looks darker), and some imbricated minerals oriented parallel to them. To estimate the uncertainty of these free-hand measurements, we performed five replicate tracing iterations for chondrule-matrix and matrix-FGR boundary in 13 chondrules. This uncertainty shows a positive correlation between the average chondrule diameter and the standard deviation ($R^2$ = 0.72), that is, at larger chondrule diameter, the standard deviation of the five free-hand measurements increases (Table S1 in

supporting information). Moreover, the linear regression of the chondrule diameter + FGR versus standard deviation displays a low value in the coefficient of determination ($R^2$ = 0.43; Table S1). We use these models to calculate the uncertainties of the 162 measured chondrules. The FGR thickness was calculated by quadratic error using the values of chondrule diameter and chondrule diameter + FGR. The porosity of the FGRs and ICM was calculated using the threshold tool in the software ImageJ.

## RESULTS

### Petrographic Characteristics of FGRs Around Chondrules

Among all types of chondrules (porphyritic olivine, porphyritic pyroxene, porphyritic olivine-pyroxene, and nonporphyritic), well-defined FGRs were found (Fig. 1). Rimmed chondrules exceed 100 µm in diameter (Table S2 in supporting information). The FGRs show distinctive petrographic features compared to the ICM such as higher porosity (mean ± standard deviation of 24 ± 11 vol%, N = 9, compared to 15 ± 7 vol%, N = 9), as previously seen by Zanetta et al. (2021) in the Paris chondrite and (ii) size of smaller opaque phases (mean circular size ± standard deviation of 7 ± 4 µm, N = 50, compared to 28 ± 27 µm, N = 52). The FGR-matrix interface is frequently delineated by a thin layer of oriented iron oxide, sulfides, or tochilinite-cronstedtite intergrowths (TCI, Figs. 1b and 1d) (Pignatelli et al., 2016, 2017; Vacher et al., 2019) that is brighter than adjacent areas in BSE images. Several FGRs in petrologic type 2 chondrites (CM, CR) have multilayered structures comprising (i) compacted material at the chondrule-FGR interface and (ii) a porous outer layer regularly containing imbricated minerals and metal beads oriented parallel to the chondrule perimeter (Fig. 1d). In contrast, most chondrule rims in petrologic type 3 chondrites (CV, CO) show no evidence of textural or compositional layering, and the chondrule-FGR and FGR-matrix interfaces commonly include a discontinuous thin film (~3 µm) of iron oxide (Figs. 1a and 1b). In addition, most FGRs (>75%) observed in

Fig. 1. Representative examples of rimmed chondrules in backscattered electron images of (a, b) EM 397, (c, d) Paris, (e, f) Renazzo, and (g, h) Vigarano; CO, CM, CR, and CV carbonaceous chondrites, respectively. Dashed white lines mark chondrule borders and dashed yellow lines the FGR-matrix interface.b, d) Details of FGR-matrix boundary. b) A discontinuous thin film (~3 µm) of iron oxide.c) The FGRs are narrower at the contact between the two rimmed type II chondrules, which may have collided and agglomerated before the end of dust accretion onto chondrules (so that the thickness at the contact was deprived of further increase). Collision of the two rimmed type II chondrules shortly after their formation is statistically more likely than later coagulation given the rarity of type II chondrules in carbonaceous chondrites.d) Multilayered structures observed in the FGRs. Dashed orange lines indicate compacted material at the chondrule-FGR interface and dashed red line indicates the porous outer layer containing imbricated minerals and metal beads oriented parallel to the chondrule perimeter. The white arrows indicate TCI. (Color figure can be viewed at wileyonlinelibrary.com.)
<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>
<figure><img src="image_10.png" /><figcaption>Fig. 2. Broken chondrules in (a, b) CO and (c, d) CV chondrites have FGRs mantling only their intact edges. In (d), the white arrows mark a discontinuous radial crack in the FGR of the broken CV chondrule that does not affect the matrix, and the yellow arrow indicates a microchondrule within the FGR. Dashed white lines mark the exterior borders of chondrules and dashed yellow lines the FGR–matrix interface. (Color figure can be viewed at wileyonlinelibrary.com.)</figcaption></figure>

the CO3 chondrites recovered from the Atacama Desert include calcium sulfates that fill porosity and fractures.

Most rims are continuous with round edges and sharp FGR–matrix transition. However, fractions of the FGRs are absent in the cases of (i) fragmented chondrules with angular or irregular borders (Fig. 2) (Metzler et al., 1992; Zanetta et al., 2021) or (ii) local regions where coarse-grained components impinge upon chondrule exteriors (Fig. 1c).

## FGR Statistics: Frequency and Thickness

Our point counting analysis revealed coarse-grained (>5 µm, i.e., chondrules, refractory inclusions, Fe-Ni metal beads, isolated olivine grains) to fine-grained (<5 µm, i.e., ICM and FGRs) ratios of ~69/31, ~64/36, ~61/39, and 34/66 in CO, CR, CV, and CM chondrites, respectively. The mean percentage of complete rimmed chondrules (excluding fragments) ranges from 1.6 ±

1.0% in CO chondrites to 11.8 ± 1.3%, 16.4 ± 0.4%, and 67.8 ± 18.3% in CR, CV, and CM chondrites, respectively (Table 1). The estimated percentages of FGR-bearing chondrules in CO, CR, CV, and CM chondrites are positively correlated with the modal abundances of fine-grained materials in those chondrites.

We determined the apparent thicknesses of FGRs around 97, 13, 44, and 8 continuously rimmed chondrules in CO, CR, CM, and CV chondrites, respectively (Table S2). The average (±standard deviation [STD]) apparent diameters of chondrules (not including FGRs) in CO, CM, CR, and CV chondrites are 397 (±210), 338 (±229), 668 (±337), and 1552 (±923) µm, respectively. FGR thicknesses vary greatly, but are generally within the range of 8–140 µm, with a median of ~34 µm (Fig. 3). Simple linear regressions on our results show positive correlations between FGR thickness and chondrule radius (dashed lines in Fig. 3),
<figure><img src="image_11.png" /><figcaption>Fig. 3. Positive correlations between apparent chondrule radius and apparent FGR thickness among the studied (a) CO, (b) CM, (c) CR, and (d) CV carbonaceous chondrites. Colored solid lines and black dashed lines represent weighted and simple regressions, respectively (Thirumalai et al., 2011); fitting parameters are shown for the weighted regressions only. (Color figure can be viewed at wileyonlinelibrary.com.)</figcaption></figure>

if with lower R² for CR chondrites but the number of data points (12) may be too low for the difference to be significant. The slopes of weighted linear regressions increase from 0.05 in CV chondrites to 0.13, 0.13, and 0.14 in CR, CO, and CM chondrites, respectively, indicating that FGR thickness increases with increasing matrix abundance. The slope of the weighted regression for CMs is comparable to the range of 0.16–0.21 reported by Metzler et al. (1992) but steeper than the slope of 0.1 reported in the X-ray computed tomography study of Murchison by Hanna and Ketcham (2018). This latter difference results from the 2-D nature of our measurements, which are known to systematically overestimate true (3-D) rim thicknesses (e.g., Cuzzi & Olson, 2017). In all studied chondrites, the weighted regressions have positive y-intercepts that increase with mean chondrule size, consistent with literature data (e.g., Liffman, 2019).

The frequency of occurrence and the thickness of FGRs differ slightly between type I and type II chondrules. For instance, the percentage of rimmed type I (n = 311) with respect to all type I chondrules (n = 5754) is 5.4% with an average FGR thickness of 41 µm (n = 140). In comparison, the percentage of

rimmed type II (n = 40) with respect to all type II chondrules (n = 536) is 7.5% with an average FGR thickness of 36 µm (n = 21). In CM2 chondrites, 62% and 49% of the counted type I and II chondrules are rimmed, respectively, whereas in CO3 chondrites, 1.4% and 3.1% are rimmed, respectively (Table S3 in supporting information). In Murchison, Sears et al. (1993) reported that their “group A” chondrules (essentially type I) had thicker FGRs than their “group B” chondrules (essentially type II); the slope of their thickness versus size correlation for type I chondrules was twice as steep as that for type II chondrules. We see little difference between type II and type I FGR thickness/chondrule size correlations in our CM (Paris) and CO data, although the data are sparse.

## Microchondrules in FGRs and the Intercomponent Matrix

We observed nine microchondrules (<40 µm in diameter; Krot & Rubin, 1996; Krot et al., 1997) in the fine-grained materials (FGR and ICM) of LoV 123 and Vigarano. All four microchondrules observed in Vigarano occur within the FGRs of type I chondrules;
<figure><img src="image_12.png" /><figcaption>Fig. 4. Backscattered electron images and compositional maps of two microchondrules within rimmed type I chondrules in (a–c) CO and (d–f) CV chondrites. The CO chondrite microchondrule shows sharp contact with the fine-grained material and is composed of an olivine core surrounded by Ca-poor pyroxene (c) as well as a small metal bead inside (b). These petrographic features are similar to their host chondrule. The CV chondrite microchondrule shows sharp contact with the fine-grained material and is Ca- and Al-rich (f, Mg-Al-Ca compositional map), different from their host chondrule (Mg-rich). It could represent melted mesostasis expelled from some parent chondrule. Yellow arrows mark the microchondrules, and red boxes indicate the areas shown in the compositional maps. Dashed white lines mark chondrule borders and dashed yellow lines the FGR–matrix interface. (Color figure can be viewed at wileyonlinelibrary.com.)</figcaption></figure>

meanwhile, among the five observed microchondrules in
LoV 123, two were found in the matrix and three
within the FGRs of type I chondrules (Fig. 4). Most
observed microchondrules are isolated, nonporous, and
have sharp boundaries. The apparent diameters range
from 3.2 to 37.9 µm (average 17.4 ± 12.2 µm), and
some show internal zoning, with olivine cores
surrounded by low-Ca pyroxene margins (Fig. 4c) and
can display metal beads inside (Fig. 4b). This
composition and texture are similar to type I
chondrules, thus, similar to their host chondrules.

However, one microchondrule has a Ca-Al-rich
composition, similar to mesostasis but different from
the Mg-rich mineral in the host chondrule (Figs. 4d–f).
The thickness of microchondrule-bearing FGR is
comparable to that of microchondrule-free ones
(57 ± 33 µm and 40 ± 24 µm, respectively).

Previously, microchondrules (<40 µm in diameter; Krot & Rubin, 1996; Krot et al., 1997) have been mostly reported in unequilibrated ordinary chondrites (UOC), and mostly within FGR of chondrules/ inclusions and occasionally isolated or clustered in the
<figure><img src="image_13.png" /></figure>

Fig. 5. Correlation between the modal abundance of ICM+FGR and the percentage of rimmed chondrules in CO, CM, CR, and CV chondrites. The black solid line represents the simple linear regression for all measurements, and the fit parameters are reported at top left. Reference data do not report errors associated with the modal abundance or percentage of rimmed chondrule. Error bars are smaller than symbol sizes in most cases of our reported data. (Color figure can be viewed at wileyonlinelibrary.com.)

fine-grained matrix (Bigolski et al., 2016; Dobrică & Brearley, 2016; Rubin et al., 1982). Yet a few microchondrules were also observable around chondrule Ch4 in the CR2 chondrite Elephant Moraine 92042 (Connolly et al., 2001) and three microchondrules have also been found in the FGR of one calcium–aluminum-rich inclusion, one chondrule, and one compound chondrule in two CM chondrites, Murchison and Elephant Moraine 96029 (Suttle et al., 2019).

DISCUSSION

A Nebular Formation of FGR

The estimated percentages of FGR-bearing
chondrules in CO, CR, CV, and CM chondrites are
positively correlated with the modal abundances of
fine-grained materials in those chondrites (Fig. 5),
particularly the ICM because FGRs account for only a
minority of the fine-grained materials present (Hanna
& Ketcham, 2018). To explain this correlation solely
through parent body processes would require that
either (i) FGRs were derived from the ICM by
compaction (e.g., Trigo-Rodriguez et al., 2006; Wasson
& Rubin, 2014) or (ii) the ICM was derived from
FGRs by attrition (e.g., Metzler et al., 1992).
However, FGRs are more porous than the ICM (this
work; Zanetta et al., 2021), excluding their origin by
compaction of the matrix. Similar to (ii), even in those

CM lithologies deemed by Metzler et al. (1992) to be
“primary accretionary rocks,” FGRs are outnumbered
in modal abundance by ICM (recognizable by its
larger abundance of TCI; contrast to their figs. 5, 7, 8
and their cartoon in fig. 19; see also Trigo-Rodriguez
et al., 2006), so ICM must have predated the primary
accretion and is thus unlikely to be derived from FGR
in the parent body. More generally, FGRs are
distinguished from the ICM based on the mineralogy,
bulk composition (Bigolski, 2017; Friend et al., 2018;
Zanetta et al., 2021), and presolar grain abundance
(Haenecour et al., 2018; Leitner et al., 2016). Thus, it
is unlikely that either one derived from the other
within the parent body, although they may ultimately
share similar pre-accretionary descent. Although some
portion of the FGRs may have been incorporated into
the ICM during lithification, as suggested by instances
of rim fragmentation (Fig. 2) (see also Bigolski, 2017)
or rare isolated microchondrules (if originally
hosted in FGRs), the correlation between the
frequency of FGRs and ICM abundance requires
another explanation.

In fact, the very broken chondrules just mentioned,
in having rims interrupted where they were fragmented,
provide strong evidence for FGR formation prior to
accretion. Incidentally, the FGR around a broken
chondrule in Vigarano (Figs. 2c and 2d) also displays a
discontinuous radial crack in the FGR that does not
affect the matrix, suggesting a fragmentation before
agglomeration with the ICM.

FGR thickness is positively correlated to host
chondrule size (Fig. 3) (see also Cuzzi, 2004; Hanna &
Ketcham, 2018). This correlation between FGR
thickness and chondrule size has also been interpreted
as evidence of FGR formation within the
protoplanetary disk via (i) a weakly turbulent nebula
(Cuzzi, 2004; Hanna & Ketcham, 2018) or (ii)
supersonic interactions between chondrules and a
mixture of gas and dust (Liffman, 2019; Liffman &
Toscano, 2000). Indeed, in either case, the frequency of
interactions between chondrules and dust should have
increased with increasing chondrule size; that is, larger
chondrules would have accreted more dust (see Fig. 3).
This scenario is supported by the observed correlation
between the abundance of FGR-bearing chondrules
and matrix (Fig. 5), provided that ICM modal
abundance is the representative of dust abundances in
the chondrite formation regions. We note that Rubin
(2010) also found matrix abundance to be
anticorrelated with the porphyritic/nonporphyritic
chondrule ratio among different chondrite groups (CO,
CK, CR, CM, CV, R, EL, and EH), which he
considered a proxy of dust abundance during
chondrule-forming events.
## FGR and Chondrule Formation

When exactly did FGRs accrete onto the chondrules—in particular how long after chondrule formation? What do the textural differences between FGR and ICM teach us? Mounting evidence suggests that FGRs, or their immediate precursors, formed in relatively warm environments. Indeed, Zanetta et al. (2021) reported that, despite their porosity, FGRs in Paris show low degree of aqueous alteration, which they attributed to low water/rock ratios, as expected if water was mostly gaseous at the time of FGR formation (and if water mobility was limited to a few tens of micrometers on the parent body after accretion; Brearley, 2014). Bigolski (2017) has found that most FGRs around UOC chondrules exhibit sintered textures and estimated a range of 350–800 °C for their formation. Bigolski et al. (2016) have described numerous microchondrules (which testify to temperatures reaching the point of melting) in them, which we also found in carbonaceous chondrites' FGRs, if at lower abundances (Fig. 6). The lower abundance of presolar silicate grains in FGRs compared to the ICM in CO3 chondrites (Haenecour et al., 2018) may indicate their partial destruction during a heating event, whereas the opposite trend in aqueously altered CR2 chondrites may be traced to the more efficient aqueous alteration of the ICM (Haenecour et al., 2018). One may also note that the particles or aggregates which accreted to form FGRs (Matsumoto et al., 2021) were necessarily smaller than the FGR thickness and thus did not exceed a few tens of microns. However, the few Ma elapsed since the formation of the disk would allow sufficient time for reaching the sticking barrier of the order of a millimeter (e.g., Brauer et al., 2008; Jacquet, 2014). Perhaps then, some thermal or mechanical effects, such as ice volatilization or ram pressure, had temporarily disaggregated local millimeter-sized dust aggregates.

Most available literature ascribes the warm conditions of FGR formation to reheating episodes that occurred after the formation of rimmed chondrules (e.g., Bigolski, 2017; Bigolski et al., 2014; Krot et al., 1997). In this view, coarse-grained (or “igneous”) chondrule rims could represent melted FGRs (e.g., Rubin, 2010) from which microchondrules might have originated (Krot et al., 1997). However, no igneous chondrule rims were associated with the FGRs of chondrules in our sections. Furthermore, this can explain neither the larger thicknesses of igneous rims compared to FGRs (Matsumoto et al., 2021) nor the similar oxygen isotopic compositions of igneous rims and the host chondrules (Jacquet et al., 2015). Alternatively, microchondrules could have formed

<figure><img src="image_14.png" /><figcaption>Fig. 6. Positive correlations between apparent chondrule radius and apparent FGR thickness between type I and type II chondrules in (a) CO and (b) CM carbonaceous chondrites. Colored solid lines represent simple regressions. Type I and type II chondrules are represented by the blue circle and orange square, respectively. No rimmed type II chondrule was found in the sections of CR and CV chondrites studied. (Color figure can be viewed at wileyonlinelibrary.com.)</figcaption></figure>

during collisions between partially molten chondrules (Dobrică & Brearley, 2016), and coarse-grained rims could have resulted from the accretion of microchondrules near the end of crystallization (Jacquet, 2021). In this view, early accreted (and “digested”) droplets would have merely increased the size of the chondrule, perhaps accounting for the correlation between average chondrule size and igneous rim thickness (Rubin, 2010).

FGRs may merely represent the tail end of this “hot dust accretion”; that is, FGRs may comprise material that was heated (but not molten) in the vicinity of the chondrule-forming region, in some “halo” around the volume where solids experienced melting (e.g., Hubbard & Ebel, 2014), as sketched in Fig. 7. Indeed, some (though perhaps not all; e.g., Hubbard & Ebel, 2014) presolar grains could have survived in such a peripheral environment, ultimately being preserved in FGRs. FGR may have incorporated some materials processed in the chondrule-forming region such as microchondrules or fine condensates (Wasson, 2008).
<figure><img src="image_15.png" /><figcaption>Fig. 7. Schematic representation of the proposed genetic link between chondrules and FGRs. The chondrule-forming region and chondrules are not drawn to scale. The chondrule-forming region includes a zone in which solids were melted, a peripheral region ("halo") where solids were not melted but exceeded some arbitrary processing temperature, and an outer zone where dust went unprocessed. Chondrules (probably still warm) subsequently accreted FGRs, which were composed mostly of processed dust, with a few "contaminants" from the chondrule-melting volume (e.g., microchondrules) and presolar grains that could have survived in the unmelted halo. The abundance of rimmed chondrules depends on the dust abundance in the chondrule-forming region. Before their incorporation into a parent body, chondrule fragments with noncontinuous FGRs were likely produced through collisions in a turbulent nebular environment. (Color figure can be viewed at wileyonlinelibrary.com.)</figcaption></figure>

The FGR could have also accreted some unheated material but before it efficiently diluted the aforementioned higher temperature components. Rapid dust accretion would have been promoted by the higher dust densities estimated during chondrule formation (e.g., Alexander et al., 2008; Jacquet, 2021; Schrader et al., 2013). Chondrules may have essentially accreted all the “halo” material. The lack of significant differences in the FGR thickness/chondrule size relationships between type I and type II chondrules may suggest that the halo/chondrule-melting region mass ratio did not vary much. The exact properties of FGRs would depend on how the dust accretion rate compared with the cooling rate and/or the background temperature (inside or outside the snow line).

It is thus both possible and simpler to invoke the very formation of chondrules as the origin of the warm conditions recorded by FGRs, rather than a subsequent heating episode. In this scenario, the fine-grained materials produced during chondrule formation might be largely restricted to FGRs. If this is the case, matrix-chondrule complementarity (e.g., Goldberg et al., 2015; Hezel et al., 2018; Palme et al., 2015), on the matrix side, would be largely carried by FGR (and their fragments detached in the ICM; see Friend et al., 2018), with later co-accretion of unprocessed ICM not affecting the overall solar bulk elemental ratios (Braukmüller et al., 2018; Jacquet et al., 2016). Since large-scale migration within the disk would have destroyed any correlation between the frequency of
occurrence of FGRs (reflecting the conditions of chondrule formation) and ICM abundance (reflecting dust abundance during accretion), chondrules and matrix incorporated in a given chondrite must have formed locally (e.g., Piralla et al., 2021; Schneider et al., 2020).

## CONCLUDING REMARKS

We characterized FGR around chondrules in CO, CM, CR, and CV carbonaceous chondrites. Our results revealed positive correlations between (i) rim thickness and host chondrule radius and (ii) the abundance of rimmed chondrules and that of other fine-grained matrix material. Combined with our petrographic description of FGR, our data suggest that they did not form during parent body evolution, but rather result from nebular processes, with the frequency and thickness of FGR being directly related to the abundance of available dust in their respective chondrule formation regions. Since large-scale migration within the disk would have destroyed the correlation between FGR and matrix abundances, our data support models of local chondrule formation with limited, if any, transport in the circumsolar disk. We hypothesize that FGR accreted under warm conditions at temperatures between silicate solidus (~1300 K) and ice vaporization (~170 K), in the aftermath of the chondrule-forming events. The matrix contribution to matrix-chondrule complementarity must then be dominated by FGR (and isolated fragments of rim within the matrix), with the later co-accretion of the unprocessed matrix not affecting the overall solar bulk composition.

*Acknowledgments*—We are grateful to Museo del Meteorito de San Pedro de Atacama for loaning the samples of CO chondrites. We thank the Muséum national d'Histoire naturelle de Paris for the loan of the CM, CV, and CR sections. G.A.P and F.O.E. acknowledge support from FONDECYT project 1201223. G.A.P. was supported by an Eiffel Excellence Scholarship (grant 968045D). We thank the anonymous reviewers for helpful comments that improved the manuscript. This is CRPG contribution #2794.

*Data Availability Statement*—The data that support the findings of this study are openly available at https://doi.org/10.24396/ORDAR-82.

*Editorial Handling*—Dr. A. J. Timothy Jull

## REFERENCES

Alexander, C. M. O'D., Grossman, J. N., Ebel, D. S., and Ciesla, F. J. 2008. The Formation Conditions of Chondrules and Chondrites. *Science* 320: 1617-9.

Anders, E. 1964. Origin, Age, and Composition of Meteorites. *Space Science Reviews* 3: 583-714.

Bigolski, J. N. 2017. The Formation of Fine-Grained Chondrule Rims in Unequilibrated Ordinary Chondrites. PhD thesis, The City University of New York, New York, USA.

Bigolski, J. N., Weisberg, M. K., Connolly, H. C., and Ebel, D. S. 2016. Microchondrules in Three Unequilibrated Ordinary Chondrites. *Meteoritics & Planetary Science* 51: 235-60.

Bigolski, J., Weisberg, M. K., Ebel, D. S., and Connolly, H. C. 2014. Microchondrules: Records of Multiple Heating Events in the Solar Nebula and Implications for Type II Chondrule Formation (Abstract #1879). 45th Lunar and Planetary Science Conference. CD-ROM.

Bonal, L., Bourot-Denise, M., Quirico, E., Montagnac, G., and Lewin, E. 2007. Organic Matter and Metamorphic History of CO Chondrites. *Geochimica et Cosmochimica Acta* 71: 1605-23.

Bonal, L., Quirico, E., Flandinet, L., and Montagnac, G. 2016. Thermal History of Type 3 Chondrites from the Antarctic Meteorite Collection Determined by Raman Spectroscopy of Their Polyaromatic Carbonaceous Matter. *Geochimica et Cosmochimica Acta* 189: 312-37.

Brauer, F., Henning, T., and Dullemond, C. P. 2008. Planetesimal Formation Near the Snow Line in MRI-Driven Turbulent Protoplanetary Disks. *Astronomy and Astrophysics* 487: 1-4.

Braukmüller, N., Wombacher, F., Hezel, D. C., Escoube, R., and Münker, C. 2018. The Chemical Composition of Carbonaceous Chondrites: Implications for Volatile Element Depletion, Complementarity and Alteration. *Geochimica et Cosmochimica Acta* 239: 17-48.

Brearley, A. J. 1993. Matrix and Fine-Grained Rims in the Unequilibrated CO3 Chondrite, ALHA77307: Origins and Evidence for Diverse, Primitive Nebular Dust Components. *Geochimica et Cosmochimica Acta* 57: 1521-50.

Brearley, A. J. 2014. Nebular Versus Parent Body Processing. In *Meteorites and Cosmochemical Processes*, edited by A. M. Davis, 309-34. Treatise on Geochemistry, vol. 1, 2nd ed. Oxford: Elsevier.

Brearley, A. J., and Krot, A. N. 2012. Metasomatism in the Early Solar System: The Record from Chondritic Meteorites. In *Metasomatism and the Chemical Transformation of Rock-Lecture Notes in Earth System Sciences*, edited by D. E. Harlov and H. Austrheim, 659-789. Berlin: Springer.

Connolly, H. C., Huss, G. R., and Wasserburg, G. J. 2001. On the Formation of Fe-Ni Metal in Renazzo-Like Carbonaceous Chondrites. *Geochimica et Cosmochimica Acta* 65: 4567-88.

Connolly, H. C., and Jones, R. H. 2016. Chondrules: The Canonical and Noncanonical Views: A Review of Chondrule Formation. *Journal of Geophysical Research Planets* 121: 1885-99.

Cosarinsky, M., Leshin, L. A., MacPherson, G. J., Guan, Y., and Krot, A. N. 2008. Chemical and Oxygen Isotopic Compositions of Accretionary Rim and Matrix Olivine in
CV Chondrites: Constraints on the Evolution of Nebular Dust. *Geochimica et Cosmochimica Acta* 72: 1887-913.

Cuzzi, J. N. 2004. Blowing in the Wind: III. Accretion of Dust Rims by Chondrule-Sized Particles in a Turbulent Protoplanetary Nebula. *Icarus* 168: 484–97.

Cuzzi, J. N., and Olson, D. M. 2017. Recovering 3D Particle Size Distributions from 2D Sections. *Meteoritics & Planetary Science* 52: 532–45.

Dobrică, E., and Brearley, A. J. 2016. Microchondrules in Two Unequilibrated Ordinary Chondrites: Evidence for Formation by Splattering from Chondrules During Stochastic Collisions in the Solar Nebula. *Meteoritics & Planetary Science* 51: 884–905.

Friend, P., Hezel, D. C., Barrat, J. A., Zipfel, J., Palme, H., and Metzler, K. 2018. Composition, Petrology, and Chondrule-Matrix Complementarity of the Recently Discovered Jbilet Winselwan CM2 Chondrite. *Meteoritics & Planetary Science* 53: 2470–91.

Goldberg, A. Z., Owen, J. E., and Jacquet, E. 2015. Chondrule Transport in Protoplanetary Discs. *Monthly Notices of the Royal Astronomical Society* 452: 4054–69.

Haenecour, P., Floss, C., Zega, T. J., Croat, T. K., Wang, A., Jolliff, B. L., and Carpenter, P. 2018. Presolar Silicates in the Matrix and Fine-Grained Rims Around Chondrules in Primitive CO3.0 Chondrites: Evidence for Pre-Accretionary Aqueous Alteration of the Rims in the Solar Nebula. *Geochimica et Cosmochimica Acta* 221: 379–405.

Hanna, R. D., and Ketcham, R. A. 2018. Evidence for Accretion of Fine-Grained Rims in a Turbulent Nebula for CM Murchison. *Earth and Planetary Science Letters* 481: 201–11.

Hezel, D. C., Harak, M., and Libourel, G. 2018. What We Know About Elemental Bulk Chondrule and Matrix Compositions: Presenting the ChondriteDB Database. *Chemie der Erde* 78: 1–14.

Hubbard, A., and Ebel, D. S. 2014. Protoplanetary Dust Porosity and FU Orionis Outbursts: Solving the Mystery of Earth's Missing Volatiles. *Icarus* 237: 84–96.

Huss, G. R., Alexander, C. M. O'D., Palme, H., Bland, P. A., and Wasson, J. T. 2005. Genetic Relationships Between Chondrules, Fine-Grained Rims, and Interchondrule Matrix. In *Chondrites and the Protoplanetary Disk—ASP Conference Series* 341, edited by A. N. Krot, E. R. D. Scott, and B. Reipurth, 701–31. San Francisco: Astronomical Society of the Pacific.

Jacquet, E. 2014. The Quasi-Universality of Chondrule Size as a Constraint for Chondrule Formation Models. *Icarus* 232: 176–86.

Jacquet, E. 2021. Collisions and Compositional Variability in Chondrule-Forming Events. *Geochimica et Cosmochimica Acta* 296: 18–37.

Jacquet, E., Alard, O., and Gounelle, M. 2015. Trace Element Geochemistry of Ordinary Chondrite Chondrules: The Type I/Type II Chondrule Dichotomy. *Geochimica et Cosmochimica Acta* 155: 47–67.

Jacquet, E., Barrat, J. A., Beck, P., Caste, F., Gattacceca, J., Sonzogni, C., and Gounelle, M. 2016. Northwest Africa 5958: A Weakly Altered CM-Related Ungrouped Chondrite, not a CI3. *Meteoritics & Planetary Science* 51: 851–69.

Jacquet, E., Piralla, M., Kersaho, P., and Marrocchi, Y. 2021. Origin of Isolated Olivine Grains in Carbonaceous Chondrites. *Meteoritics & Planetary Science* 56: 13–33.

Johnson, B. C., Minton, D. A., Melosh, H. J., and Zuber, M. T. 2015. Impact Jetting as the Origin of Chondrules. *Nature* 517: 339–41.

Krot, A. N., and Rubin, A. E. 1996. Microchondrule-Bearing Chondrule Rims: Constraints on Chondrule Formation. In *Chondrules and the Protoplanetary Disk*, edited by R. H. Hewins, R. H. Jones, and E. R. D. Scott, 181–4. Cambridge, UK: Cambridge University Press.

Krot, A. N., Rubin, A. E., Keil, K., and Wasson, J. T. 1997. Microchondrules in Ordinary Chondrites: Implications for Chondrule Formation. *Geochimica et Cosmochimica Acta* 61: 463–73.

Lauretta, D. S., and Buseck, P. R. 2003. Opaque Minerals in Chondrules and Fine-Grained Chondrule Rims in the Bishunpur (LL3.1) Chondrite. *Meteoritics & Planetary Science* 38: 59–79.

Lauretta, D. S., Hua, X., and Buseck, P. R. 2000. Mineralogy of Fine-Grained Rims in the ALH 81002 CM Chondrite. *Geochimica et Cosmochimica Acta* 64: 3263–73.

Leitner, J., Metzler, K., Vollmer, C., Floss, C., Harries, D., Hoppe, P., and Haenecour, P. 2019. The Presolar Grain Inventory of Fine-Grained Chondrule Rims in the Mighei-Type (CM) Chondrites. *Meteoritics & Planetary Science* 55: 1176–206.

Leitner, J., Vollmer, C., Floss, C., Zipfel, J., and Hoppe, P. 2016. Ancient Stardust in Fine-Grained Chondrule Dust Rims from Carbonaceous Chondrites. *Earth and Planetary Science Letters* 434: 117–28.

Libourel, G., and Krot, A. N. 2007. Evidence for the Presence of Planetesimal Material Among the Precursors of Magnesian Chondrules of Nebular Origin. *Earth and Planetary Science Letters* 254: 1–8.

Liffman, K. 2019. Fine-Grained Rim Formation—High Speed, Kinetic Dust Aggregation in the Early Solar System. *Geochimica et Cosmochimica Acta* 264: 118–29.

Liffman, K., and Toscano, M. 2000. Chondrule Fine-Grained Mantle Formation by Hypervelocity Impact of Chondrules with a Dusty Gas. *Icarus* 143: 106–25.

MacPherson, G. J., Hashimoto, A., and Grossman, L. 1985. Accretionary Rims on Inclusions in the Allende Meteorite. *Geochimica et Cosmochimica Acta* 49: 2267–79.

Marrocchi, Y., Bekaert, D. V., and Piani L. 2018. Origin and Abundance of Water in Carbonaceous Asteroids. *Earth and Planetary Science Letters* 482: 23–32. https://doi.org/10.1016/j.epsl.2017.10.060.

Marrocchi, Y., Euverte, R., Villeneuve, J., Batanova, V., Welsch, B., Ferrière, L., and Jacquet, E. 2019. Formation of CV Chondrules by Recycling of Amoeboid Olivine Aggregate-Like Precursors. *Geochimica et Cosmochimica Acta* 247: 121–41.

Marrocchi, Y., Villeneuve, J., Batanova, V., Piani, L., and Jacquet, E. 2018. Oxygen Isotopic Diversity of Chondrule Precursors and the Nebular Origin of Chondrules. *Earth and Planetary Science Letters* 496: 132–41. https://doi.org/10.1016/j.epsl.2018.05.042.

Matsumoto, Y., Hasegawa, Y., Matsuda, N., and Liu, M.-C. 2021. Formation of Rims Around Chondrules via Porous Aggregate Accretion. *Icarus* 367: 114538.

McSween Jr., H. Y. 1977. Carbonaceous Chondrites of the Ornans Type: A Metamorphic Sequence. *Geochimica et Cosmochimica Acta* 41: 477–91.

Metzler, K., Bischoff, A., and Stöffler, D. 1992. Accretionary Dust Mantles in CM Chondrites: Evidence for Solar
Nebula Processes. *Geochimica et Cosmochimica Acta* 56: 2873-97.

Morris, M. A., Boley, A. C., Desch, S. J., and Athanassiadou, T. 2012. Chondrule Formation in Bow Shocks Around Eccentric Planetary Embryos. *The Astrophysical Journal* 752: 27.

Palme, H., Hezel, D. C., and Ebel, D. S. 2015. The Origin of Chondrules: Constraints from Matrix Composition and Matrix-Chondrule Complementarity. *Earth and Planetary Science Letters* 411: 11-9.

Piani, L., Marrocchi, Y., Rigaudier, T., Vacher, L. G., Thomassin, D., and Marty, B. 2020. Earth's Water May Have Been Inherited from Material Similar to Enstatite Chondrite Meteorites. *Science* 369: 1110-3.

Pignatelli, I., Marrocchi, Y., Mugnaioli, E., Bourdelle, F., and Gounelle, M. 2017. Mineralogical, Crystallographic and Redox Features of the Earliest Stages of Fluid Alteration in CM Chondrites. *Geochimica et Cosmochimica Acta* 209: 106-22.

Pignatelli, I., Marrocchi, Y., Vacher, L. G., Delon, R., and Gounelle, M. 2016. Multiple Precursors of Secondary Mineralogical Assemblages in CM Chondrites. *Meteoritics & Planetary Science* 51: 785-805.

Pinto, G. A., Marrocchi, Y., Morbidelli, A., Charnoz, S., Varela, M. E., Soto, K., Martínez, R., and Olivares, F. 2021. Constraints on Planetesimal Accretion Inferred from Particle-Size Distribution in CO Chondrites. *The Astrophysical Journal Letters* 917: L25.

Piralla, M., Villeneuve, J., Batanova, V., Jacquet, E., and Marrocchi, Y. 2021. Conditions of Chondrule Formation in Ordinary Chondrites. *Geochimica et Cosmochimica Acta* 313: 295-312.

Rubin, A. E. 2010. Physical Properties of Chondrules in Different Chondrite Groups: Implications for Multiple Melting Events in Dusty Environments. *Geochimica et Cosmochimica Acta* 74: 4807-28.

Rubin, A. E., Scott, E. R. D., and Keil, K. 1982. Microchondrule-Bearing Clast in the Piancaldoli LL3 Meteorite: A New Kind of Type 3 Chondrite and Its Relevance to the History of Chondrules. *Geochimica et Cosmochimica Acta* 46: 1763-76.

Ruzicka, A., Hiyagon, H., Hutson, M., and Floss, C. 2007. Relict Olivine, Chondrule Recycling, and the Evolution of Nebular Oxygen Reservoirs. *Earth and Planetary Science Letters* 257: 274-89.

Schindelin, J., Arganda-Carreras, I., Frise, E., Kaynig, V., Longair, M., Pietzsch, T., Preibisch, S. et al. 2012. Fiji: An Open-Source Platform for Biological-Image Analysis. *Nature Methods* 9: 676-82.

Schneider, J. M., Burkhardt, C., Marrocchi, Y., Brennecka, G. A., and Kleine, T. 2020. Early Evolution of the Solar Accretion Disk Inferred from Cr-Ti-O Isotopes in Individual Chondrules. *Earth and Planetary Science Letters* 551: 116585.

Schrader, D. L., Connolly Jr., H. C., Lauretta, D. S., Nagashima, K., Huss, G. R., Davidson, J., and Domanik, K. J. 2013. The Formation and Alteration of the Renazzo-Like Carbonaceous Chondrites II: Linking O-Isotope Composition and Oxidation State of Chondrule Olivine. *Geochimica et Cosmochimica Acta* 101: 302-27.

Scott, E. R. D., and Jones, R. H. 1990. Disentangling Nebular and Asteroidal Features of C03 Carbonaceous Chondrite Meteorites. *Geochimica et Cosmochimica Acta* 54: 2485-502.

Scott, E. R. D., and Krot, A. N. 2014. Chondrites and Their Components. In *Treatise on Geochemistry*, 2nd ed., edited by H. D. Holland and K. K. Turekian, 65-137. Oxford: Elsevier.

Sears, D. W. G., Benoit, P. H., and Jie, L. U. 1993. Two Chondrule Groups Each with Distinctive Rims in Murchison Recognized by Cathodoluminescence. *Meteoritics* 28: 669-75.

Simon, J. I., Cuzzi, J. N., McCain, K. A., Cato, M. J., Christoffersen, P. A., Fisher, K. R., Srinivasan, P., Tait, A. W., Olson, D. M., and Scargle, J. D. 2018. Particle Size Distributions in Chondritic Meteorites: Evidence for Pre-Planetesimal Histories. *Earth and Planetary Science Letters* 494: 69-82.

Suttle, M. D., Genge, M. J., Salge, T., Lee, M. R., Folco, L., Góral, T., Russell, S. S., and Lindgren, P. 2019. A Microchondrule-Bearing Micrometeorite and Comparison with Microchondrules in CM Chondrites. *Meteoritics & Planetary Science* 54: 1303-24.

Takayama, A., and Tomeoka, K. 2012. Fine-Grained Rims Surrounding Chondrules in the Tagish Lake Carbonaceous Chondrite: Verification of Their Formation Through Parent-Body Processes. *Geochimica et Cosmochimica Acta* 98: 1-18.

Thirumalai, K., Singh, A., and Ramesh, R. 2011. A MATLAB™ Code to Perform Weighted Linear Regression with (Correlated or Uncorrelated) Errors in Bivariate Data. *Journal of the Geological Society of India* 77: 377-80.

Tomeoka, K., and Ohnishi, I. 2010. Indicators of Parent-Body Processes: Hydrated Chondrules and Fine-Grained Rims in the Mokoia CV3 Carbonaceous Chondrite. *Geochimica et Cosmochimica Acta* 74: 4438-53.

Tomeoka, K., and Ohnishi, I. 2014. Olivine-Rich Rims Surrounding Chondrules in the Mokoia CV3 Carbonaceous Chondrite: Further Evidence for Parent-Body Processes. *Geochimica et Cosmochimica Acta* 137: 18-34.

Tomeoka, K., and Ohnishi, I. 2015. Redistribution of Chondrules in a Carbonaceous Chondrite Parent Body: A Model. *Geochimica et Cosmochimica Acta* 164: 543-55.

Trigo-Rodriguez, J. M., Rubin, A. E., and Wasson, J. T. 2006. Non-Nebular Origin of Dark Mantles Around Chondrules and Inclusions in CM Chondrites. *Geochimica et Cosmochimica Acta* 70: 1271-90.

Vacher, L. G., Truche, L., Faure, F., Tissandier, L., Mosser-Ruck, R., and Marrocchi, Y. 2019. Deciphering the Conditions of Tochilinite and Cronstedtite Formation in CM Chondrites from Low Temperature Hydrothermal Experiments. *Meteoritics & Planetary Science* 54: 1870-89.

Wasson, J. T. 2008. Evaporation of Nebular Fines During Chondrule Formation. *Icarus* 195: 895-907.

Wasson, J. T., and Rubin, A. E. 2014. Absence of Matrix-Like Chondrule Rims in CR2 LAP 02342. *Meteoritics & Planetary Science* 49: 245-60.

Zanda, B., Hewins, R. H., Bourot-Denise, M., Bland, P. A., and Albarède, F. 2006. Formation of Solar Nebula Reservoirs by Mixing Chondritic Components. *Earth and Planetary Science Letters* 248: 650-60.

Zanda, B., Lewin, E., and Humayun, M. 2018. The Chondritic Assemblage: Complementarity Is Not a Required Hypothesis. In *Chondrules: Records of Protoplanetary Disk Processes*, edited by S. Russell, H. C. Connolly Jr., and A. Krot, 122-50. Cambridge, UK: Cambridge University Press.
Zanetta, P. M., Leroux, H., le Guillou, C., Zanda, B., and Hewins, R. H. 2021. Nebular Thermal Processing of Accretionary Fine-Grained Rims in the Paris CM Chondrite. *Geochimica et Cosmochimica Acta* 295: 135–54.

SUPPORTING INFORMATION

Additional supporting information may be found in
the online version of this article.

Zolensky, M., Barrett, R., and Browning, L. 1993. Mineralogy and Composition of Matrix and Chondrule Rims in Carbonaceous Chondrites. *Geochimica et Cosmochimica Acta* 57: 3123–48.

**Table S1.** Uncertainty of free-hand measurements

**Table S2.** Rimmed chondrules measurements

**Table S3.** Abundance of rimmed chondrules