Maxime Piralla
email: maxime.piralla@univ-lorraine.fr

Johan Villeneuve

Valentina Batanova

Emmanuel Jacquet

Yves Marrocchi

Conditions of chondrule formation in ordinary chondrites

Keywords: ordinary chondrites, chondrules, oxygen isotopes, gas-melt interactions, inner protoplanetary disk Unified Astronomy Thesaurus: Chondrites (228), Chondrules (229), Isotopic abundances

Chondrules are sub-millimetric spheroids that are ubiquitous in chondrites and whose formation mechanism remains elusive. Textural and oxygen isotopic characteristics of chondrules in carbonaceous chondrites (CCs) suggest that they result from the recycling of isotopically heterogeneous early-condensed precursors via gas-melt interactions. Here, we report high-resolution X-ray elemental maps and in situ O isotopic analyses of FeO-poor, olivine-rich chondrules from ordinary chondrites (OCs) to compare the conditions of chondrule formation in these two main classes of chondrites. OC chondrules show minor element (e.g., Ti, Al) zonings at both the chondrule and individual olivine grain scales. Considering the entire isotopic data set, our data define a mass-independent correlation, with olivine grains showing O isotopic variations spanning more than 40 ‰. Though 16 O-rich relict olivine grains were identified in OC chondrules, they are much less abundant than in CC chondrules. They appear as two types: (i) those with low minor element abundances and ∆ 17 O < -15 ‰ and (ii) those with varying minor element abundances and less negative ∆ 17 O values averaging -5.5 ‰. The host olivine grains exhibit mass-dependent O isotopic variations within individual chondrules.

Our results reveal that similar processes (precursor recycling and interactions between chondrule melts and a SiO-and Mg-rich gas) established the observed features of OC and CC chondrules. The mass-dependent isotopic variations recorded by host olivine grains result from kinetic effects induced by complex evaporation/recondensation processes during the gas-melt interactions. This suggests that OC chondrules formed through enhanced recycling processes, in good agreement with the lower abundances of relict olivine grains in OC chondrules compared to CC chondrules. We use the ∆ 18 O =  18 O - 17 O parameter to demonstrate that there is no genetic relationship between CC and OC

chondrules, suggesting limited radial transport in the protoplanetary disk. Finally, to the first order, the ∆ 18 O-∆ 17 O diagram may allow the non-carbonaceous vs. carbonaceous origin of a given chondrule to be deciphered.

1-Introduction

Whether primitive or differentiated, meteorites exhibit a fundamental isotopic dichotomy between a carbonaceous (C) and a non-carbonaceous (NC) superclan [START_REF] Trinquier | Origin of Nucleosynthetic Isotope Heterogeneity in the Solar Protoplanetary Disk[END_REF][START_REF] Warren | Stable-isotopic anomalies and the accretionary assemblage of the Earth and Mars: A subordinate role for carbonaceous chondrites[END_REF][START_REF] Budde | Molybdenum isotopic evidence for the origin of chondrules and a distinct genetic heritage of carbonaceous and non-carbonaceous meteorites[END_REF][START_REF] Kruijer | Age of Jupiter inferred from the distinct genetics and formation times of meteorites[END_REF][START_REF] Kruijer | The great isotopic dichotomy of the early Solar System[END_REF][START_REF] Nanne | Origin of the non-carbonaceouscarbonaceous meteorite dichotomy[END_REF][START_REF] Burkhardt | Elemental and isotopic variability in solar system materials by mixing and processing of primordial disk reservoirs[END_REF][START_REF] Kleine | The Non-carbonaceous-Carbonaceous Meteorite Dichotomy[END_REF]. Compared to their NC counterparts, C meteorites are enriched in neutron-rich isotopes of many elements with different geochemical and cosmochemical behaviors (e.g., Ti, Cr, Ni) thus representing a fundamental characteristic of the solar system [START_REF] Kleine | The Non-carbonaceous-Carbonaceous Meteorite Dichotomy[END_REF]. Combined with the chronology of iron meteorites, the NC-C dichotomy suggests that meteorites derived from two genetically distinct reservoirs that coexisted but remained spatially separated between 1 and ~3-4 Myr after the formation of Ca-Al-rich inclusions (CAIs), the oldest known solids in the solar system [START_REF] Kruijer | Age of Jupiter inferred from the distinct genetics and formation times of meteorites[END_REF][START_REF] Desch | The E ect o J piter's Formation on the Distribution of Refractory Elements and Inclusions in Meteorites[END_REF][START_REF] Kleine | The Non-carbonaceous-Carbonaceous Meteorite Dichotomy[END_REF]. This prolonged physical barrier between the two reservoirs remains a matter of debate, and may reflect the early formation of Jupiter [START_REF] Kruijer | Age of Jupiter inferred from the distinct genetics and formation times of meteorites[END_REF], a pressure maximum in the disk [START_REF] Brasser | The partitioning of the inner and outer Solar System by a structured protoplanetary disk[END_REF], or the preponderant role of the snowline [START_REF] Lichtenberg | Bifurcation of planetary building blocks during Solar System formation[END_REF]. We note that the subsequent loss of any intermediate materials also remains a possibility [START_REF] Jacquet | Fingerprints of the Protosolar Cloud Collapse in the Solar System. II. Nucleosynthetic Anomalies in Meteorites[END_REF]. Regardless of their origins, the NC and C reservoirs are considered to represent the primordial inner and outer parts of the solar system, respectively [START_REF] Trinquier | Widespread 54 Cr Heterogeneity in the Inner Solar System[END_REF][START_REF] Warren | Stable-isotopic anomalies and the accretionary assemblage of the Earth and Mars: A subordinate role for carbonaceous chondrites[END_REF][START_REF] Kruijer | Age of Jupiter inferred from the distinct genetics and formation times of meteorites[END_REF][START_REF] Kruijer | The great isotopic dichotomy of the early Solar System[END_REF][START_REF] Desch | The E ect o J piter's Formation on the Distribution of Refractory Elements and Inclusions in Meteorites[END_REF][START_REF] Burkhardt | Elemental and isotopic variability in solar system materials by mixing and processing of primordial disk reservoirs[END_REF].

The isotopic dichotomy observed among bulk chondrites has now also been observed at the scale of individual chondrules [START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF], sub-millimetric igneous silicate spheroids formed during the evolution of the protoplanetary disk [START_REF] Connolly | Chondrules: The canonical and noncanonical views: A Review of Chondrule Formation[END_REF]. NC chondrules have bulk oxygen, 50 Ti, and 54 Cr isotopic compositions uniformly similar to their host chondrites, whereas chondrules in carbonaceous chondrites (CCs) have more variable compositions, sometimes differing from that of their host chondrite [START_REF] Williams | Chondrules reveal large-scale outward transport of inner Solar System materials in the protoplanetary disk[END_REF][START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF]. Although the isotopic compositions of CC and NC chondrules may overlap for individual isotope ratios, this does not hold in multi-isotope space, i.e., (i) no CC chondrule plots within the field of NC chondrites (although a few plot near NC achondrites; [START_REF] Williams | Chondrules reveal large-scale outward transport of inner Solar System materials in the protoplanetary disk[END_REF]) and (ii) no NC chondrule plots within the field of CC chondrites [START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF]. Consistent with transport simulations by [START_REF] Goldberg | Chondrule transport in protoplanetary discs[END_REF], these characteristics suggest that chondrules essentially accreted where they had formed, with a predominant effect of their precursor heterogeneity [START_REF] Gerber | Mixing and Transport of Dust in the Early Solar Nebula as Inferred from Titanium Isotope Variations among Chondrules[END_REF][START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF] as opposed to large-scale (that is, reaching across C and NC reservoir boundaries) chondrule transport in the disk after their formation [START_REF] Van Kooten | Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites[END_REF][START_REF] Williams | Chondrules reveal large-scale outward transport of inner Solar System materials in the protoplanetary disk[END_REF]. That is, the varied isotopic compositions of CC chondrules may result from the mixing of NC dust with a chemically variable dust component having a CAI-or amoeboid olivine aggregate (AOA)-like isotopic composition [START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF].

Conversely, the narrow range of nucleosynthetic anomalies observed in NC chondrules suggests that they formed from different precursors and/or under different conditions. Therefore, this dichotomy ultimately calls into question the conditions of dust formation in the NC and CC reservoirs.

Type I (i.e. FeO-poor), CC chondrules are characterized by the frequent presence of relict olivine grains that are generally more 16 O-rich than their host olivines (e.g., [START_REF] Jones | Oxygen isotope heterogeneity in chondrules from the Mokoia CV3 carbonaceous chondrite[END_REF][START_REF] Rudraswami | Oxygen isotope systematics of chondrules in the Allende CV3 chondrite: High precision ion microprobe studies[END_REF][START_REF] Ushikubo | Primordial oxygen isotope reservoirs of the solar nebula recorded in chondrules in Acfer 094 carbonaceous chondrite[END_REF][START_REF] Tenner | Oxygen isotope systematics of chondrule phenocrysts from the CO3.0 chondrite Yamato 81020: Evidence for two distinct oxygen isotope reservoirs[END_REF][START_REF] Tenner | Oxygen isotope ratios of FeO-poor chondrules in CR3 chondrites: Influence of dust enrichment and H 2 O during chondrule formation[END_REF][START_REF] Tenner | Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry[END_REF][START_REF] Schrader | The retention of dust in protoplanetary disks: Evidence from agglomeratic olivine chondrules from the outer Solar System[END_REF][START_REF] Schrader | Outward migration of chondrule fragments in the early Solar System: O-isotopic evidence for rocky material crossing the Jupiter Gap?[END_REF][START_REF] Hertwig | Formation of chondrules in a moderately high dust enriched disk: Evidence from oxygen isotopes of chondrules from the Kaba CV3 chondrite[END_REF][START_REF] Chaumard | Oxygen isotope systematics of chondrules in the Murchison CM2 chondrite and implications for the CO-CM relationship[END_REF][START_REF] Chaumard | Oxygen isotope systematics of chondrules in the Paris CM2 chondrite: Indication for a single large formation region across snow line[END_REF][START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a;;[START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF][START_REF] Ushikubo | Oxygen-isotope systematics of chondrules and olivine fragments from Tagish Lake C2 chondrite: Implications of chondrule-forming regions in protoplanetary disk[END_REF][START_REF] Weisberg | Micro-distribution of oxygen isotopes in unequilibrated enstatite chondrites[END_REF].

Relict olivine grains are interpreted as chondrule precursor minerals that survived the high-temperature chondrule forming event(s) [START_REF] Jones | Oxygen isotope heterogeneity in chondrules from the Mokoia CV3 carbonaceous chondrite[END_REF]. Recent high-current X-ray maps and secondary ion mass spectrometry (SIMS) measurements of relict olivine grains have revealed that they are characterized by low refractory element (Al, Ti) contents, similar to those observed in olivine grains within AOAs [START_REF] Jacquet | Chondrule heritage and thermal histories from trace element and oxygen isotope analyses of chondrules and amoeboid olivine aggregates[END_REF][START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a)). It has thus been proposed that type I chondrules are derived from AOAs or AOA-related nebular materials; these nebular condensates underwent partial melting and subsequent interactions with SiO-and Mg-rich gas [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF](Marrocchi et al., , 2019a;;[START_REF] Villeneuve | Silicon isotopic compositions of chondrule silicates in carbonaceous chondrites and the formation of primordial solids in the accretion disk[END_REF][START_REF] Jacquet | Origin of isolated olivine grains in carbonaceous chondrites[END_REF][START_REF] Jacquet | Collisions and compositional variability in chondrule-forming events[END_REF].

Relict olivine grains are also observed in chondrules from ordinary chondrites (OCs, the most abundant type of NC chondrites), but in lower abundances than in CC chondrules [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF][START_REF] Tenner | Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry[END_REF]Marrocchi et al., 2019a;[START_REF] Schrader | Outward migration of chondrule fragments in the early Solar System: O-isotopic evidence for rocky material crossing the Jupiter Gap?[END_REF]. It has been proposed that 16 O-rich relict olivine grains within OC chondrules originated from the C reservoir [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF], but this is difficult to reconcile with the spatially and chemically distinct NC and C reservoirs inferred from nucleosynthetic anomalies [START_REF] Gerber | Mixing and Transport of Dust in the Early Solar Nebula as Inferred from Titanium Isotope Variations among Chondrules[END_REF][START_REF] Spitzer | Isotopic Evolution of the Inner Solar System Inferred from Molybdenum Isotopes in Meteorites[END_REF][START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF]. Still, the similar O isotopic compositions of CAIs in non-carbonaceous and carbonaceous chondrites (e.g., [START_REF] Mckeegan | Oxygen Isotopic Abundances in Calcium-Aluminum-Rich Inclusions from Ordinary Chondrites: Implications for Nebular Heterogeneity[END_REF][START_REF] Guan | Oxygen isotopes in calciumaluminum-rich inclusions from enstatite chondrites: new evidence for a single CAI source in the solar nebula[END_REF][START_REF] Fagan | Calcium-aluminum-rich inclusions in enstatite chondrites (II): Oxygen isotopes[END_REF]) must suggest common descent for part of their components.

The oxygen isotope systematics of OC chondrules themselves also differ from those of their CC chondrule counterparts. They exhibit more 17,18 O-rich isotopic compositions (i.e., Δ 17 O ≈ 0-1 ‰; [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF] than CC chondrules (-5 to -2 ‰; [START_REF] Tenner | Oxygen isotope systematics of chondrule phenocrysts from the CO3.0 chondrite Yamato 81020: Evidence for two distinct oxygen isotope reservoirs[END_REF][START_REF] Tenner | Oxygen isotope ratios of FeO-poor chondrules in CR3 chondrites: Influence of dust enrichment and H 2 O during chondrule formation[END_REF][START_REF] Tenner | Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry[END_REF][START_REF] Schrader | Variations in the O-isotope composition of gas during the formation of chondrules from the CR chondrites[END_REF][START_REF] Schrader | Outward migration of chondrule fragments in the early Solar System: O-isotopic evidence for rocky material crossing the Jupiter Gap?[END_REF][START_REF] Hertwig | Formation of chondrules in a moderately high dust enriched disk: Evidence from oxygen isotopes of chondrules from the Kaba CV3 chondrite[END_REF][START_REF] Chaumard | Oxygen isotope systematics of chondrules in the Murchison CM2 chondrite and implications for the CO-CM relationship[END_REF][START_REF] Chaumard | Oxygen isotope systematics of chondrules in the Paris CM2 chondrite: Indication for a single large formation region across snow line[END_REF][START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a;;[START_REF] Jabeen | Oxygen isotope signatures in bulk chondrules: Implications for the aqueous alteration and thermal metamorphism on the Allende CV3 parent body[END_REF] and show internal mass-dependent

fractionations not yet observed in CC chondrules [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF][START_REF] Schrader | Variations in the O-isotope composition of gas during the formation of chondrules from the CR chondrites[END_REF][START_REF] Schrader | The retention of dust in protoplanetary disks: Evidence from agglomeratic olivine chondrules from the outer Solar System[END_REF][START_REF] Schrader | Outward migration of chondrule fragments in the early Solar System: O-isotopic evidence for rocky material crossing the Jupiter Gap?[END_REF][START_REF] Tenner | Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry[END_REF][START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a)). Within OCs, type I porphyritic olivine (PO) chondrules tend to have lower δ 18 O values than type I porphyritic pyroxene (PP) chondrules with similar Δ 17 O values [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF]. This characteristic has been ascribed to either kinetic isotopic fractionations during multiple evaporation events or equilibrium isotopic partitioning between molten chondrule precursors and a CO-H 2 O-rich gas of varying composition [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF]. However, the textural similarity between OC and CC chondrules [START_REF] Libourel | Chondrules as direct thermochemical sensors of solar protoplanetary disk gas[END_REF][START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a;;[START_REF] Jacquet | Origin of isolated olivine grains in carbonaceous chondrites[END_REF] may indicate comparable interactions between the melts and SiO-and Mg-rich gas.

To better understand the conditions of type I chondrule formation in the NC reservoir, we selected type I PO chondrules from the pristine ordinary chondrites Semarkona (LL3.00), Piancaldoli (LL3.10), and Bishunpur (LL3.15; [START_REF] Grossman | The onset of metamorphism in ordinary and carbonaceous chondrites[END_REF][START_REF] Marrocchi | The Piancaldoli meteorite: A forgotten primitive LL3.10 ordinary chondrite[END_REF]. We report a comprehensive study of chondrule olivine grains combining petrological observations and quantitative geochemical analyses. We use our results to discuss (i) the nature and conditions of the chondrule-forming events in the NC reservoir based on textural and O isotopic evidence, (ii) how they compare with those in the C reservoir, and (iii) implications for dynamics within the protoplanetary disk.

2-Materials & Methods

2-1-Samples

We surveyed all chondrules within (i) a home-made thick section of Piancaldoli (3.10; [START_REF] Marrocchi | The Piancaldoli meteorite: A forgotten primitive LL3.10 ordinary chondrite[END_REF] and (ii) thick sections rom the s m national d'Histoire nat relle (Paris, France) of Semarkona (LL3.00, section 3583; [START_REF] Grossman | The onset of metamorphism in ordinary and carbonaceous chondrites[END_REF] and Bishunpur (LL3.15, section 2491sp4; [START_REF] Grossman | The onset of metamorphism in ordinary and carbonaceous chondrites[END_REF]. We selected 11 type I PO chondrules for further analyses: one from Semarkona, six from Piancaldoli, and four from Bishunpur.

2-2-Elemental mapping and analyses

High-resolution cathodoluminescence (CL), elemental X-ray mapping, and quantitative point analyses were performed at the Institut des Sciences de la Terre (ISTerre, Grenoble, France) using a JEOL JXA 8230 electron microprobe equipped with five wavelength-dispersive spectrometers (WDS), silicon drift detector energy-dispersive spectrometer (SDD-EDS; [START_REF] Batanova | Trace element analysis of olivine: High precision analytical method for JEOL JXA-8230 electron probe microanalyser[END_REF], and panchromatic cathodoluminescence system. High-resolution CL maps coupled with fast major element (Mg, Fe, Si) X-ray maps (on WDS detectors) were acquired simultaneously using an acceleration voltage of 20 kV, a beam current of 100 nA, 1.5-2 μm step size, and a dwell time of 10 ms. This allows the identification of olivine, pyroxene, and glass in chondrules. High-resolution elemental X-ray maps were performed with an acceleration voltage of 20 kV and a beam current of 500 nA; the step size and dwell time were set to 1.5-2 μm and 330-600 ms, respectively, to achieve acquisition times of 18-24 h depending on map size. Al, Ca, Cr, Mn, and Ti were measured by WDS and Mg, Fe, and Si by EDS. Detection limits were below 40 ppm for Al, Ca, Ti, Cr, and Mn as estimated from the minimum differences between the average concentrations of visually distinct homogeneous zones and the standard deviations of the concentrations within homogeneous zones. These X-ray maps are semi-quantitative, because the backgrounds were not quantified in similar off-peak maps. Quantitative analyses of Al, Ti, Ca, Cr, Mn, Ni, Mg, Fe, and Si in all olivine grains large enough to be isotopically characterized by SIMS were performed with an accelerating voltage of 20 kV, probe current of 900 nA, beam diameter of 1 μm (diameter of interaction volume around 5 µm). The total peak/background counting time was 400 s for Al, Ti, Ca, Mn and 200 s for Cr and Ni with equal counting time in positions of peak and background measured from both side of the peak (e.g., Batanova et al., 2018). Such a high current and long counting times allow very low detection limits, here estimated to be about 10 ppm for Al, Ca, and Ti, and below 20 ppm for Cr, Mn, and Ni [START_REF] Batanova | Trace element analysis of olivine: High precision analytical method for JEOL JXA-8230 electron probe microanalyser[END_REF]2018). Mg, Fe, and Si were simultaneously measured on the EDS detector. The JEOL software ZAF method was used for matrix corrections. MongOL sh11-2 olivine reference material [START_REF] Batanova | New Olivine Reference Material for In Situ Microanalysis[END_REF] was used for major element standardization and for monitoring analytical accuracy and precision during measurements.

2-3-Isotopic analyses

We measured the oxygen isotopic compositions of type I chondrule olivine grains by SIMS, targeting nearly all olivine grains within each chondrule, and performed multiple analyses within the coarsest zoned olivine grains. We used the CAMECA IMS 1270 E7 at the Centre de Recherches Pétrographiques et Géochimiques (CRPG-CNRS, Nancy, France). 16 O -, 17 O -, and 18 O -ions produced by a Cs + primary ion beam (~10 µm, ~2-2.5 nA, rastered over 5 × 5 µm 2 ) were measured in multi-collection mode using three Faraday cups (FCs). To remove the 16 OH -interference on the 17 O -peak and to maximize the flatness atop the 16 O -and 18 O - peaks, the entrance and exit slits of the central FC were adjusted to obtain mass resolution power (MRP = M/ΔM) of ∼7,000 for 17 O -. The two off-axis multicollection FCs, L'2 and H1, were respectively used to measure 16 O -and 18 O -and were set on exit slit 1 (MRP = 2,500).

We used 10 10 Ω, 10 12 Ω, and 10 11 Ω resistors for the L'2 ( 16 O), central ( 17 O), and H1 ( 18 O) FCs, respectively (see [START_REF] Bouden | Triple Oxygen Isotope Measurements by Multi-Collector Secondary Ion Mass Spectrometry[END_REF] for further details). As an additional safeguard against 16 OH -interference, a liquid N 2 trap was used to reduce the pressure in the analysis chamber to <1 × 10 -8 mbar. A normal-incidence electron gun was used for charge compensation. Total measurement times were 300 s, comprising 120 s of pre-sputtering and 180 s of analysis.

Two terrestrial standards, San Carlos olivine and JV1 diopside, were used to define the massdependent fractionation line. The instrumental mass fractionation (IMF) of chondrule olivine grains was corrected using San Carlos olivine. To monitor any instrumental drift and to achieve good precision, the San Carlos olivine was analyzed after every 15-20 sample analyses. Typical count rates obtained on San Carlos olivine were 1.0 × 10 9 cps, 4.0 × 10 5 cps, and 2.1 × 10

3-Results

The selected type I PO chondrules range from 150 to 700 µm in diameter. They S1), but highcurrent X-ray maps reveal complex chemical zonings at both the chondrule and olivine scales S1). Olivine grains in the inner parts of chondrules show Al-, Ti-, Mn-, and Cr-depleted cores surrounded by overgrowths enriched in these trace or minor S1). Similar zonings are also observed perpendicular to the long axes of olivine bars in the Semarkona Ch-4 chondrule (Fig. S8), similar to observations by [START_REF] Libourel | Chondrules as direct thermochemical sensors of solar protoplanetary disk gas[END_REF]. Dusty olivine grains areas are uniformly Ca-, Al-, and Ti-poor and Mn-rich and, in Bishunpur Ch-6, are accompanied by oscillatory-zoned hopper textured crystals (Fig. 3). Olivine grains in the outer parts of chondrules are characterized by asymmetric trace and minor element distributions: closer to the chondrule center, olivine compositions are similar to those in interior chondrule olivines, and toward the outer edge of chondrules, Ca, Al, and Ti contents increase then decrease again, whereas Mn, Cr, and Fe contents increase monotonically (Figs. 1-3, Figs. S2-S8, Table S1). Olivine minor and trace element concentrations range from 30 to 1,500 ppm TiO 2 , 100 to 9,700 ppm S1). These zonings are comparable to those observed in carbonaceous chondrites [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF](Marrocchi et al., , 2019a)).

(Figs. 1-3, Figs. S2-S8, Table
elements (Figs. 1-3, Figs. S2-S8, Table
Across the entire dataset, olivine O isotopic compositions vary widely, with δ 18 O and δ 17 O values ranging respectively from -40.9 ‰ to +9.0 ‰ and rom -44.0 ‰ to +6.5 ‰ (Fig. 4). O r data de ine a good correlation with δ 17 O = [0.97 ± 0.02] × δ 18 O -[1.0 ± 0.9] ‰ (MSWD = 4.7, r 2 = 0.94, n = 649). As in our previous works [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF](Marrocchi et al., , 2019a)),

we adopt the convention of [START_REF] Ushikubo | Primordial oxygen isotope reservoirs of the solar nebula recorded in chondrules in Acfer 094 carbonaceous chondrite[END_REF] and consider olivine grains with ∆ 17 O val es beyond 3σ (analytical error) from that of their host olivine to be relicts. This is a conservative approach. For example, the standard deviation on the ∆ 17 O value of the "host olivine" in chondrule Bishunpur Ch-2 is twice the analytical error (Table S3), and the S1,S3). The mean host δ 18 O value (including Piancaldoli Ch-8) is 3.6 ‰, somewhat higher than the val e o 1.9 ‰ reported or type I PO chondrules by [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF] but comparable to that of their type I POP chondr les (3.9 ‰). The average intra-chondrule standard deviation of host olivine δ 18 O values is 1.0 ‰, regardless of the presence or absence of relicts (Fig. 5A-B, Tables S1,S3); this value is higher than the val e o 0.3 ‰ reported for type I PO or POP chondrules by [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF], but similar to the value of 1.1 ‰ reported for carbonaceous chondrites by [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al. ( , 2019a)). The highest δ 18 O (i.e., isotopically heaviest) host olivine values seem restricted to analyses in chondrule interiors (Fig. 6).

Of our 649 oxygen isotopic measurements, only 17, or about 3%, correspond to relict olivine grains according to the threshold of [START_REF] Ushikubo | Primordial oxygen isotope reservoirs of the solar nebula recorded in chondrules in Acfer 094 carbonaceous chondrite[END_REF], much lower than the 17 % and 10 % reported for the carbonaceous chondrites NWA 5958 (C2-ung) and Kaba (CV3) by [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al. ( , 2019a)). This is consistent with previous literature data: [START_REF] Hertwig | Formation of chondrules in a moderately high dust enriched disk: Evidence from oxygen isotopes of chondrules from the Kaba CV3 chondrite[END_REF] reported 24 % of analyzed olivines in Kaba (CV3) to be relicts and Chaumard et al.

(2018) reported 14 % in Murchison (CM2), whereas [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF] reported 7 % in LL chondrites. However, direct comparison of the absolute percentages may be hampered by the different search strategies because the few analyses per chondrule in past literature studies (usually n = 2-10; e.g., [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF][START_REF] Rudraswami | Oxygen isotope systematics of chondrules in the Allende CV3 chondrite: High precision ion microprobe studies[END_REF][START_REF] Hertwig | Formation of chondrules in a moderately high dust enriched disk: Evidence from oxygen isotopes of chondrules from the Kaba CV3 chondrite[END_REF][START_REF] Chaumard | Oxygen isotope systematics of chondrules in the Murchison CM2 chondrite and implications for the CO-CM relationship[END_REF][START_REF] Tenner | Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry[END_REF] may have been biased in favor of large host olivine crystals. Relict olivine grains do not show any specific spatial distributions within chondrules. They also have narrower ranges of Ti, Al, and Cr contents and Mg# than their host olivine grains and are depleted in Ni and Mn (Fig. 7; Tables S1-S3). Of note, relict olivine grains with ∆ 17 O < -15‰ are systematically depleted in all these elements except Cr (Fig. 7, Tables S1-S3). Relict grains plot roughly along the Primary Chondrule Minerals (PCM) line defined by [START_REF] Ushikubo | Primordial oxygen isotope reservoirs of the solar nebula recorded in chondrules in Acfer 094 carbonaceous chondrite[END_REF] for the carbonaceous chondrite Acfer 094, but, like our host grains, seem systematically shifted toward its left (Fig. 4). This can be quantified by the mass-ractionation parameter ∆ 18 O = δ 18 O -δ 17 O (e.g., [START_REF] Zanda | Formation of solar nebula reservoirs by mixing chondritic components[END_REF]Figs. 8, S10), which corresponds to the delta of the 18 O/ 17 O ratio and is thus insensitive to 16 O enrichments or depletions. ∆ 18 O is on average 2.1 ‰ in relict olivines (n = 17 grains, 1 SD = 0.9 ‰; Figs. 8, S10, Table S2) and 1.1 ‰ in host olivines (n = 11 chondrule averages, 1 SD = 0.5 ‰; Figs. 8, S10, Table S3); these values are somewhat higher than the average of 0.45 ‰ obtained for type I PO chondrules by [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF]. In terms of this parameter, the PCM corresponds to ∆ 18 O = 2.7 ‰ (strictly speaking, [0.013 ± 0.013]  δ 18 O + [2.7 ± 0.11] ‰ using the parameterization of [START_REF] Ushikubo | Primordial oxygen isotope reservoirs of the solar nebula recorded in chondrules in Acfer 094 carbonaceous chondrite[END_REF], consistent with our previous data on relict and host grains in carbonaceous chondrites [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF](Marrocchi et al., , 2019a;;Fig. 8). Such displaced ∆ 18 O values in OC relict grains are also apparent in analyses of dusty grains [START_REF] Schrader | Outward migration of chondrule fragments in the early Solar System: O-isotopic evidence for rocky material crossing the Jupiter Gap?[END_REF] and the 16 O-rich olivines of Baeza [START_REF] Bravo | Oxygen isotope systematics of ordinary chondrite chondrules: insights into the inner solar system planetary reservoir[END_REF], although one cannot unequivocally distinguish between relicts and 16 O-rich hosts in the latter study because of the low number of analyses per chondrule.

4-Discussion

4-1 Origin of chondrule textures

In CCs, type I PO chondrules are characterized by complex chemical zonings at the scales of both chondrules and individual olivine grains [START_REF] Libourel | Chondrules as direct thermochemical sensors of solar protoplanetary disk gas[END_REF][START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a)), with inner-chondrule olivine grains showing Al-, Ti-, Mn-, and Crdepleted cores surrounded by overgrowths enriched in those elements. At chondrule margins, olivine grains exhibit asymmetric grain growths and distributions of trace and minor elements, with Ca, Al, and Ti contents increasing and then decreasing toward the outer chondrule edge [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF](Marrocchi et al., , 2019a)). Our results show similar features for OC chondrules with (i) chemically zoned trace and minor element contents (e.g., Al, Ti, Mn, and Cr; Figs. 1-3, S2-S8; Table S1) and (ii) the asymmetric growth of outer-chondrule crystals (Figs. 1-3, S1-S8). However, we also observed more complex textures such as hoppertextured olivine crystals in porphyritic OC chondrules (e.g., Fig. 3), which, in CCs, have only been reported in barred olivine chondrules [START_REF] Libourel | Chondrules as direct thermochemical sensors of solar protoplanetary disk gas[END_REF].

Elements such as Cr might be mobilized during low-grade metamorphism [START_REF] Grossman | The onset of metamorphism in ordinary and carbonaceous chondrites[END_REF]. However, Cr in type II FeO-rich olivine grains is not affected in Semarkona [START_REF] Grossman | The onset of metamorphism in ordinary and carbonaceous chondrites[END_REF] nor in Piancaldoli [START_REF] Marrocchi | The Piancaldoli meteorite: A forgotten primitive LL3.10 ordinary chondrite[END_REF] but could be modified in Bishunpur [START_REF] Grossman | The onset of metamorphism in ordinary and carbonaceous chondrites[END_REF]. Similarly, metamorphism can slightly affect the Cr distribution in Mg-rich olivine grains of Bishunpur. For the other elements, Ca could be affected due to its relatively fast diffusion within Mg-rich olivine but Ti and Al are not affected as their respective diffusion rates in Mg-rich olivine are very slow (e.g., [START_REF] Chakraborty | Diffusion Coefficients in Olivine, Wadsleyite and Ringwoodite[END_REF], as may be judged from the preserved fine structure of the zoning.

The observed zonings thus appear inherited from the (pre-accretionary) chondrule-forming processes.

Overall, the similarity of the features observed in OC and CC chondrules indicates that these processes were essentially the same at different heliocentric distances in the protoplanetary disk: (i) the melting of precursor aggregates containing isotopically diverse (and sometimes AOA-like) materials produced, owing to partial evaporation, refractory Ca-Al-Ti-rich melt; (ii) crystallization of Ca-Al-Ti-rich host olivines from the melt around preserved Al-Ti-poor relicts; and (iii) the subsequent crystallization of Ca-Al-Ti-poor olivine, especially on outer-chondrule rims, was enhanced by the recondensation of Mg and SiO (also diluting the aforementioned refractory incompatible elements), which eventually also promoted pyroxene crystallization [START_REF] Libourel | Chondrules as direct thermochemical sensors of solar protoplanetary disk gas[END_REF][START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a;;[START_REF] Villeneuve | Silicon isotopic compositions of chondrule silicates in carbonaceous chondrites and the formation of primordial solids in the accretion disk[END_REF][START_REF] Jacquet | Origin of isolated olivine grains in carbonaceous chondrites[END_REF]. Interactions with the surrounding gases would have rapidly buffered the O isotopic composition of the melt to that of the local reservoir, which explains the limited variability of host olivine ∆ 17 O values beyond analytical error. The surrounding gases included SiO and likely also H 2 O [START_REF] Ushikubo | Primordial oxygen isotope reservoirs of the solar nebula recorded in chondrules in Acfer 094 carbonaceous chondrite[END_REF][START_REF] Schrader | The formation and alteration of the Renazzo-like carbonaceous chondrites II: Linking O-isotope composition and oxidation state of chondrule olivine[END_REF][START_REF] Schrader | Variations in the O-isotope composition of gas during the formation of chondrules from the CR chondrites[END_REF][START_REF] Tenner | Oxygen isotope systematics of chondrule phenocrysts from the CO3.0 chondrite Yamato 81020: Evidence for two distinct oxygen isotope reservoirs[END_REF][START_REF] Tenner | Oxygen isotope ratios of FeO-poor chondrules in CR3 chondrites: Influence of dust enrichment and H 2 O during chondrule formation[END_REF][START_REF] Hertwig | Formation of chondrules in a moderately high dust enriched disk: Evidence from oxygen isotopes of chondrules from the Kaba CV3 chondrite[END_REF][START_REF] Chaumard | Oxygen isotope systematics of chondrules in the Murchison CM2 chondrite and implications for the CO-CM relationship[END_REF], which may have isotopically exchanged O with the melt and/or contributed to the net influx of O through reactions such as SiO (g) + H 2 O (g) = SiO 2 (l) + H 2 (g) .

4-2 Mass-dependent oxygen isotopic variations

Host olivine δ 18 O and δ 17 O values range from -4.0 ‰ to +9.0 ‰ and from -3.5 ‰ to +6.5 ‰, respectively (Figs. 4, S10, Table S1). Interestingly, they define a correlation (δ 17 O = [0.76 ± 0.06] × δ 18 O -[0.08 ± 0.14] ‰; MSWD = 0.21, r 2 = 0.80, n = 632) whose slope is shallower than that of the entire data set (0.97 ± 0.02; see section 3) but steeper than 0.52.

However, taken separately, the host olivine gains in individual chondrules plot along particular mass fractionation (i.e., slope 0.52) lines (e.g., Bishunpur Ch-6, Fig. 5A). This S3). Finally, the intra-chondrule ranges of host olivine δ 18 O values vary rom 1.7 to 13 ‰ (with intrachondrule host olivine 1 SD of 0.5 -1.9 ‰; Table S3), with the largest intra-chondrule variations being comparable to the range of the entire host olivine dataset.

In this subsection, we investigate the origin of these isotopic variations. We first note that oxygen diffuses very slowly in solid olivine (e.g., diffusivities below 10 -17 m²/s, corresponding to ~1 µm²/d, below 1600 °C; e.g., [START_REF] Chakraborty | Diffusion Coefficients in Olivine, Wadsleyite and Ringwoodite[END_REF], such that each olivine spot should preserve the O isotopic composition it had upon crystallization. Although such isotopic variations might be explained by melt-crystal isotopic fractionations, the observed variations are larger than those predicted under equilibrium crystallization (e.g., ln(α olivine- basaltic melt ) ≈ δ 18 O olivine -δ 18 O basaltic melt < 1‰; [START_REF] Eiler | Oxygen Isotope Variations of Basaltic Lavas and Upper Mantle Rocks[END_REF][START_REF] Zhao | Calculation of oxygen isotope fractionation in magmatic rocks[END_REF]. Another possibility is kinetic fractionations induced by diffusion and growth reactions [START_REF] Tiller | The redistribution of solute atoms during the solidification of metals[END_REF][START_REF] Smith | A mathematical analysis of solute redistribution during solidification[END_REF][START_REF] Albarede | Kinetic disequilibrium in trace element partitioning between phenocrysts and host lava[END_REF]. Specifically, a boundary layer that has become depleted or enriched in some element via crystallization may induce diffusive transport of that element in the melt, and thus isotopic fractionation if the diffusivity depends on isotopologue mass. Such a process could generate isotopic fractionations as large as ~10 ‰ or δ 18 O [START_REF] Jambon | Isotopic fractionation: A kinetic model for crystals growing from magmatic melts[END_REF][START_REF] Watkins | Kinetic Fractionation of Non-Traditional Stable Isotopes by Diffusion and Crystal Growth Reactions[END_REF], of similar magnitude to those observed within OC chondrules. (Figs. 4, 5; Tables S1,S3). However, we exclude this process for several reasons. First, the fast crystallization of large crystals (>0.5 cm) is required to produce such extended isotopic fractionations, whereas all chondrule olivine grains are smaller than 200 µm (excluding the large olivine crystal in chondrule Ch-6 of Piancaldoli; Fig. S4). Second, the power law dependence on isotope mass used by [START_REF] Jambon | Isotopic fractionation: A kinetic model for crystals growing from magmatic melts[END_REF] is rather high for natural condensed systems [START_REF] Lesher | Self-diffusion in Silicate Melts: Theory, Observations and Applications to Magmatic Systems[END_REF][START_REF] Watkins | Kinetic Fractionation of Non-Traditional Stable Isotopes by Diffusion and Crystal Growth Reactions[END_REF]. Third, convective (isotopically insensitive) transport must be negligible, which [START_REF] Jambon | Isotopic fractionation: A kinetic model for crystals growing from magmatic melts[END_REF] deemed unlikely for viscosities below 10 5 Pa•s, an upper limit for typical high-temperature chondrule melts (e.g., [START_REF] Gooding | Estimated viscosities and implied thermal histories of chondrule droplets[END_REF]. Finally, the theoretical analytical model is only developed for 1D systems, whereas numerical 3D simulations tend to show reduced fractionations [START_REF] Watson | Non-equilibrium isotopic and elemental fractionation during diffusion-controlled crystal growth under static and dynamic conditions[END_REF][START_REF] Watkins | Kinetic Fractionation of Non-Traditional Stable Isotopes by Diffusion and Crystal Growth Reactions[END_REF]. Therefore, the large, kinetic, and massdependent isotopic variations observed within OC chondrules cannot have resulted from chemical and isotopic disequilibrium during crystallization from chondrule melts, and olivine crystals should essentially record the isotopic composition of their immediate parental melt.

The large observed O isotopic variations could also be related to gas-melt interactions during chondrule formation. Although a single O-bearing molecule is often considered in isotopic models of chondrule formation (i.e., only H 2 O (g) or SiO (g) ), several major O-bearing molecules co-existed, whether considering (i) a high-temperature gas of solar composition [START_REF] Larimer | Chemical fractionations in meteorites-I. Condensation of the elements[END_REF][START_REF] Lodders | Solar System Abundances and Condensation Temperatures of the Elements[END_REF][START_REF] Javoy | First-principles investigation of equilibrium isotopic fractionation of O-and Si-isotopes between refractory solids and gases in the solar nebula[END_REF], (ii) a dust-enriched region subject to evaporation [START_REF] Ebel | Condensation in dust-enriched systems[END_REF], or (iii) impact-generated vapor plumes [START_REF] Visscher | Chemistry of impact-generated silicate melt-vapor debris disks[END_REF]. Equilibrium fractionations between the main O-bearing species at temperatures of 500-1573 K (i.e., SiO (g) , H 2 O (g) , and CO (g) ; [START_REF] Richet | A Review of Hydrogen, Carbon, Nitrogen, Oxygen, Sulphur, and Chlorine Stable Isotope Fractionation Among Gaseous Molecules[END_REF][START_REF] Javoy | First-principles investigation of equilibrium isotopic fractionation of O-and Si-isotopes between refractory solids and gases in the solar nebula[END_REF] would predict δ 18 O values increasing in the order olivine ≈ SiO (g) < H 2 O (g) < CO (g) (with the last being abo t 3 ‰ higher than the irst at the highest temperatures; e.g. [START_REF] Zanda | Formation of solar nebula reservoirs by mixing chondritic components[END_REF][START_REF] Marrocchi | The Piancaldoli meteorite: A forgotten primitive LL3.10 ordinary chondrite[END_REF]. With varying temperature, changing fractionation factors and condensate/gas ratios would yield only minor isotopic variations in olivine, <2 ‰ for δ 18 O, even allowing for fractional condensation [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF], and thus cannot be responsible for most of the observed intra-chondrule variations. We note in passing that our type I PO chondrules are isotopically comparable to [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF] type I POP and PP chondrules but at odds with the lighter isotopic compositions of their type I PO chondrules, which they ascribed to higher equilibration temperatures.

Considering gas-melt interactions, the oxygen isotopic compositions of chondrule precursors may have differed from that of the surrounding gas, and molten chondrules would have evolved toward equilibrium. This would imply that host olivine grains that crystallized at various stages of the gas-melt isotopic exchange (by continual condensation and evaporation) record that isotopic evolution, and thus varying ∆ 17 O and/or ∆ 18 O values.

However, this is not consistent with the uniform ∆ 17 O values obtained for host olivine grains (within analytical errors). One could, of course, conceive that the endmembers of this putative mixing lay along a slope 0.52 line (i.e., constant ∆ 17 O) in the oxygen three-isotope plot, but relict grains (which would be representative of the solid precursors) are generally displaced from their hosts (closer to the gas-solid average) roughly along a line of slope 1 (e.g., Figs. 4, 5B, 8, S10). Consequently, any evidence of an initial isotopic disequilibrium must have been lost when the host olivines started to crystallize.

However, even if the ambient gas and chondrule melts were at isotopic equilibrium, chemical disequilibrium could have induced isotopic variations via the net transfer of oxygen from one phase to another. This would tend to temporarily enrich the latter phase in light Oisotopes because, at a given temperature, lighter isotopologues move faster from one phase to another than their heavier counterparts (e.g., [START_REF] Richter | Elemental and isotopic fractionation of Type B calcium-, aluminum-rich inclusions: experiments, theoretical considerations, and constraints on their thermal evolution[END_REF]Fig. 9). Importantly, such isotopic fractionations would have been mass-dependent and thus would have not affected the ∆ 17 O value, as observed in OC chondrules (Fig. S10).

In more detail, oxygen would suffer a net evaporation during the initial heating of chondrule precursors, inducing the preferential loss of light isotopes to the undersaturated gas (Fig. 9). Assuming that evaporation coefficients are not mass-dependent, the evaporating SiO may have presented a fractionation relative to the source melt down to [M(Si 16 O)/M(Si 18 O)] 1/2 -1 = -22 ‰ for δ 18 O (e.g., [START_REF] Richter | Elemental and isotopic fractionation of Type B calcium-, aluminum-rich inclusions: experiments, theoretical considerations, and constraints on their thermal evolution[END_REF]. Via this mechanism, the melt could have attained the isotopically heaviest compositions observed in host olivine grains after a few tens of percent of evaporation. As that olivine would have started crystallizing after the evaporation stage, the earliest host olivine to crystallize would have been isotopically heavy. These early-crystallized host olivine grains would have formed the immediate overgrowths of relict crystals in chondrule interiors, which may explain why the heaviest compositions are observed in some interior grains (Fig. 9). The fact that these compositions are not clearly spatially systematic may reflect various degrees of overlap of SIMS analytical spots with relict grains (not necessarily manifest in ∆ 17 O; e.g., Bishunpur Ch-2) or the outermost (later-crystallized) parts of the overgrowths.

Upon cooling, the preferential condensation of light isotopes from the oversaturated gas would gradually shift the melt isotopic compositions toward lighter values, as recorded by the successively crystallized olivine. Of note, the melt composition might even temporarily become isotopically lighter than the equilibrium prediction before converging back toward it as the oversaturation of gaseous species eventually decreased (Fig. 9). The intensity and record of these isotopic variations during host olivine crystallization would depend on the exact thermal history, which might have been more complicated than a single heating and cooling stage. Our isotopic data show ∆ 18 O values (extending to negative values) beyond equilibrium fractionation predictions from an isotopically homogeneous bulk OC-like reservoir (Fig. S10), implying that the range of isotopic compositions within each individual chondrule was set by these kinetic effects.

4-3 OC chondrule precursors and their relationship to the CC reservoir

It is well known that most OC chondrules have ∆ 17 O values higher than most of their CC counterparts (e.g., [START_REF] Kita | High precision SIMS oxygen three isotope study of chondrules in LL3 chondrites: Role of ambient gas during chondrule formation[END_REF][START_REF] Tenner | Oxygen Isotope Characteristics of Chondrules from Recent Studies by Secondary Ion Mass Spectrometry[END_REF]Figs. 8, S10), possibly due to protracted gas-melt interactions during or before the chondrule-forming event(s) (e.g., Marrocchi et al., 2019a). Combined with literature data, our results reveal that OC chondrules also have lower ∆ 18 O values than CC chondrules (Figs. 8, S10). Besides, the average difference between the host olivine ∆ 18 O values in OC (1.1 ± 0.5 ‰, 1 SD) and CC chondrules (3.4 ± 0.5 ‰, 1 SD; [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a) ) is consistent with the average difference between those of the bulk chondrules (OCs, 1.4 ± 0.4 ‰; CCs, 3.5 ± 0.5 ‰, 1 SD; [START_REF] Clayton | Oxygen isotopic compositions of chondrules in Allende and ordinary chondrites[END_REF][START_REF] Clayton | Oxygen isotope studies of ordinary chondrites[END_REF]Clayton andMayeda, 1985, 1999;[START_REF] Mayeda | Oxygen, silicon, and magnesium isotopes in ningqiang chondrules[END_REF][START_REF] Rubin | Oxygen isotopes in chondrules and coarse-grained chondrule rims from the Allende meteorite[END_REF][START_REF] Weisberg | The CR (Renazzo-type) carbonaceous chondrite group and its implications[END_REF][START_REF] Jones | Oxygen isotope heterogeneity in chondrules from the Mokoia CV3 carbonaceous chondrite[END_REF]. Furthermore, CC chondrules show intra-chondrule mass fractionations (1 SD = 1.1 ‰ or δ 18 O; [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF]Marrocchi et al., , 2019a) similar to those observed in OC chondrules (1 SD = 1 ‰ or δ 18 O; Table S3; see section 3), although the former was not previously noticed due to the larger mass-independent variations observed in CC chondrules. This suggests that the kinetic effects during host olivine crystallization discussed in the preceding section, regardless of their causes, occurred with similar magnitudes in both chondrite classes, in good agreement with their textural similarities. However, the observed difference between the ∆ 18 O values of CC and OC chondrules (~2 ‰) is larger than those produced during the chondrule-forming events themselves (intra-and inter-chondrule ∆ 18 O SD = ~0.7 ‰ and ~0.5 ‰, respectively, in both OCs and CCs; Figs. 8, S10, Table S3), indicating that OC chondrules cannot be derived from the CC reservoir by kinetic effects attending one chondrule-forming event. Interestingly, in OC chondrules, low ∆ 18 O values are observed for (i) both relict and host olivine grains (Figs.

8, S10, Tables S1-S3) and (ii) chondr les with negative ∆ 17 O values (e.g., Piancaldoli Ch8; Figs.

8, 10; Tables S1-S3). These low ∆ 18 O values in OC chondrules are also similar to those of their host chondrites, with the average b lk OC ∆ 18 O value being 1.6 ‰, compared to 3.8 ‰ or CO chondrites [START_REF] Zanda | Formation of solar nebula reservoirs by mixing chondritic components[END_REF]. This suggests that the different O isotopic compositions of the OC and CC reservoirs were already established before the final chondrule-forming events.

Two distinct types of relict grains occur in OC chondrules: (i) those with low trace element contents, ∆ 17 O < -15 ‰, and ∆ 18 O values similar to those of CC relict and host olivine grains and (ii) those with varying trace element contents, ∆ 17 O ≈ -5.5 ‰, and ∆ 18 O values lower than those of CC relict and host olivine grains (Figs. 7,8). Interestingly, the former (or at least the two found in this study) have chemical and isotopic features similar to CC relicts', which characteristics have been interpreted as inherited from nebular condensates similar to AOAs [START_REF] Marrocchi | Oxygen isotopic diversity of chondrule precursors and the nebular origin of chondrules[END_REF](Marrocchi et al., , 2019a;;[START_REF] Villeneuve | Silicon isotopic compositions of chondrule silicates in carbonaceous chondrites and the formation of primordial solids in the accretion disk[END_REF]; see Fig.

8, S10

). This thus suggests a genetic link between early condensates and chondrules in both the OC and CC reservoirs. Conversely, OC relicts with ∆ 17 O ≈ -5.5 ‰, although having similar ∆ 17 O and minor element contents than CC host olivine grains, show significantly different ∆ 18 O values compared to CC relict and host olivine grains (Fig. 8). This indicates that even the 16 O-rich materials in OCs are not dominated by a contribution from the CC reservoir, consistent with the limited mixing between C and NC reservoirs inferred from the O-Cr-Ti systematics of NC and CC chondrules [START_REF] Schneider | Early evolution of the solar accretion disk inferred from Cr-Ti-O isotopes in individual chondrules[END_REF]. This is also consistent with the paucity of refractory inclusions in OCs (usually <<0.1 vol %, e.g., [START_REF] Kimura | Yamato 792947, 793408 and 82038: The most primitive H chondrites, with abundant refractory inclusions[END_REF] compared to 1-13 vol % in CV, CO, and CM chondrites, e.g., [START_REF] Krot | Classification of Meteorites and Their Genetic Relationships[END_REF], which limits the contribution of CC material in OCs to less than ~1 % in order of magnitude (not to mention the possibility that part of the refractory inclusions may have never been through a C reservoir, if they were dispersed throughout the disk before the C/NC dichotomy came into being). The type (ii) relicts could result from extensive recycling of previous chondrule generations, as suggested by the high chondrule fraction in OCs .

To quantitatively estimate this process, we refer to the Marrocchi et al. (2019a) chondrule recycling calculation and assume that (i) the different chondrule-forming events experienced by a given grain of nebular matter were independent and rare, and (ii) the chondrule/matrix ratio of an OC is representative of the chondrule/dust ratio of the reservoir from which it formed. Considering the modal chondrule abundances of 81 and 84 % in Piancaldoli and Semarkona, respectively [START_REF] Zanda | Formation of solar nebula reservoirs by mixing chondritic components[END_REF][START_REF] Marrocchi | The Piancaldoli meteorite: A forgotten primitive LL3.10 ordinary chondrite[END_REF], the model of Marrocchi et al. (2019a) would then imply that ~61 and 66 % of chondrule matter had been recycled from previous chondrule-forming events. In this framework, the higher the modal abundance of chondrules, the higher the amount of chondrule reprocessing. ). This continuum contrasts with the gaps reported in other isotopic biplots (e.g., tracing inherited presolar components) used to discuss the NC-C dichotomy [START_REF] Warren | Stable-isotopic anomalies and the accretionary assemblage of the Earth and Mars: A subordinate role for carbonaceous chondrites[END_REF][START_REF] Kruijer | Age of Jupiter inferred from the distinct genetics and formation times of meteorites[END_REF][START_REF] Kruijer | The great isotopic dichotomy of the early Solar System[END_REF][START_REF] Nanne | Origin of the non-carbonaceouscarbonaceous meteorite dichotomy[END_REF][START_REF] Burkhardt | Elemental and isotopic variability in solar system materials by mixing and processing of primordial disk reservoirs[END_REF][START_REF] Kleine | The Non-carbonaceous-Carbonaceous Meteorite Dichotomy[END_REF]. That said, ∆ 18 O values may still be used to a first order to constrain the NC or C origin of a given chondrule/grain as both chondritic superclans are well-resolved in the ∆ 18 O-∆ 17 O diagram (Figs. 8, 10, S11). We note that although import from CC into the NC reservoir seems quite small, evidence for isotopically NC-like chondrules in CV and CK chondrites [START_REF] Williams | Chondrules reveal large-scale outward transport of inner Solar System materials in the protoplanetary disk[END_REF]) and OC-like dusty olivine relicts in CM chondrules [START_REF] Schrader | Outward migration of chondrule fragments in the early Solar System: O-isotopic evidence for rocky material crossing the Jupiter Gap?[END_REF]) suggests more important, if limited, transport in the other direction, from NC to CC.

5-Concluding remarks

We performed high-resolution elemental X-ray mapping analyses coupled with in situ From these data, we drew the following conclusions:

O
1. The similar features observed in OC and CC chondrules indicate that chondrule formation processes were essentially the same within different reservoirs of the protoplanetary disk.

The melting of precursor aggregates containing isotopically diverse material produced refractory Ca-Al-Ti-rich melts from which host olivine grains crystallized around preserved Al-Ti-poor relicts. The subsequent crystallization of Ca-Al-Ti-poor olivine grains, especially at the outer edges of chondrules, resulted from the recondensation of Mg-and SiO-rich gas.

2-Host olivine grains in both OC and CC chondrules show intra-chondrule mass-dependent variations along lines of slope 0.52, with 1 SD ≈ 1 ‰ or δ 18 O. In CC chondrules, these variations were not previously noticed because of the larger mass-independent variations

shown by relict grains commonly measured in CC chondrules.

(

  V-SMOW) as δ 17,18 O = ( 17,18 O/ 16 O) Sample / ( 17,18 O/ 16 O) V-SMOW -1 (expressed in ‰). Typical 2σ measurement errors, accounting for internal errors on each measurement and the external reproducibility of the standards, were estimated to be ~0.4 ‰ or δ 18 O, ~0.7 ‰ or δ 17 O, and ~0.7 ‰ or Δ 17 O = δ 17 O -0.52 × δ 18 O (representing mass-independent deviation from the terrestrial fractionation line, TFL).

  Figs. S3-S4, S8) and a 0.5-mm-long olivine macrocryst was observed in the Piancaldoli Ch-6

  Al 2 O 3 , 970 to 9,700 ppm CaO, 50 to 4,600 ppm MnO, 800 to 10,000 ppm Cr 2 O 3 , and 15 to 3,600 ppm Table

  δ 18 O-∆ 17 O plot suggests a bimodal distrib tion o ∆ 17 O values aro nd 1 and 2 ‰ (Fig. S9); therefore, there are likely "hidden" relict olivine beyond the three 16 O-rich (i.e., below the TFL in Fig. S9) ones recognized in this chondrule. Host olivine grains have δ 18 O and δ 17 O values ranging from -4.0 ‰ to +9.0 ‰, with Δ 17 O values between -2.6 and +3.6 ‰. It is to note that the chondrule Piancaldoli Ch-8 has a mean Δ 17 O = -1.8 ± 0.7 ‰ distinct rom the other with a mean Δ 17 O = +0.9 ± 1.3 ‰ (Fig. 4, Tables

  implies that the intermediate slope observed in the combined host olivine data set results from the various ∆ 17 O values of the individual chondrules (Figs. 8, S10, Table

  Interestingly, the ∆ 18 O-∆ 17 O trend could be related to the abundance of chondrules in the different types of chondrites, with relatively chondrule-rich chondrites showing lower ∆18 O values (Figs. 8, 10). Then, the intermediate position in the ∆ 18 O-∆ 17 O diagram of OC relicts [type (ii)] with ∆ 17 O ≈ -5.5 ‰ and ∆ 18 O ≈ 2.1 ‰ may record previous steps of chondrule recycling if they indeed represent the debris of earlier generations of chondrules. That is, although a single chondrule-forming event may not have produced sufficient mass fractionation to account for the presently observed shift of the chondrule hosts from the PCM, the cumulative effect of several such episodes may have (e.g., by some distillation process in which the isotopically heavy gas was lost after each episode). Such a high degree of OC chondrule reprocessing may explain the low abundance of isotopically identifiable relict olivine grains, in particular those from pre-chondrule (AOA-like) precursors [the type (i) of the previous paragraph], compared to CCs. This thus attests to the higher efficiency of transient thermal events in the inner solar system. Our results thus demonstrate the predominant role of gas-melt interactions under different conditions in the inner and outer solar system in generating the petrographic and isotopic features of OC and CC chondrules (Fig.11).Although OCs andCCs show di erent ∆ 18 O values (Figs. 8, 10, S10, S11), they form a continuum trend from the low ∆ 17 O and high ∆ 18 O values of CK-and CM-related chondrites (e.g., NWA 5958) to high ∆ 17 O and low ∆ 18 O values of OC chondrites (Fig. 10, S11

  isotopic measurements of most of the visible olivine grains from 11 chondrules in the Bishunpur, Piancaldoli, and Semarkona ordinary chondrites. Our main results are: 1-OC olivine-rich chondrules are characterized by complex chemical zonings at both the chondrule and grain scales. Inner-chondrule olivine grains have Al-, Ti-, Mn-, and Cr-depleted cores surrounded by overgrowths enriched in those elements, whereas outer-chondrule olivines grew asymmetrically and are depleted in refractory elements toward the chondrule edges. 2-All olivine grains define a good correlation with δ 17 O = [0.97 ± 0.02] × δ 18 O -[1.0 ± 0.9] ‰ (MSWD = 4.7, r 2 = 0.94, n = 649). Host olivines define another correlation with a shallower slope: δ 17 O = [0.76 ± 0.06] × δ 18 O -[0.08 ± 0.14] ‰ ( SWD = 0.21, r 2 = 0.80, n = 632). 3-Relict olivine grains, if identified as having ∆ 17 O val es beyond 3σ o those of their host grains, represent only 3 % of the analyzed olivines. This abundance is lower than that reported in CC chondrules (~10-20 %). Two types of relicts were observed: (i) those with extreme 16 O enrichments (∆ 17 O < -15 ‰) and low Al 2 O 3 and TiO 2 concentrations and (ii) those with moderately negative ∆ 17 O values around -5.5 ‰ and variable minor element abundances.

3-

  These mass-dependent intra-chondrule isotopic variations can only be explained by kinetic effects during gas-melt interactions, and result from evaporation and recondensation during chondrule formation. 4-The distinct ∆ 18 O (=  18 O - 17 O) and ∆ 17 O values observed in OC and CC chondrules at both the bulk chondrule and individual grain (host and relict) scales indicate that the OC and CC reservoirs were already separated before the final chondrule-forming events. 5-Among relict grains, those with extreme 16 O-enrichments (∆ 17 O < -15 ‰) and low Al 2 O 3 and TiO 2 concentrations share similarities with AOA olivine grains, indicating a genetic link between early-condensed refractory inclusions and chondrules. Although the other relict grains with ∆ 17 O ≈ -5.5 ‰ and variable trace element ab ndances share similarities with CC host olivine grains, their distinct ∆ 18 O values imply that they do not result from the recycling of CC chondrules. Instead, this supports a local origin for OC chondrules, which resulted from several episodes of chondrule formation.

Figure Captions Fig. 1 .

 Captions1 Figure Captions

Fig. 2 .

 2 Fig. 2. (A) Back-scattered electron image of type I PO chondrule Ch-2 in LL3.15 Bishunpur

Fig. 3 .

 3 Fig. 3. (A) Back-scattered electron image of type I PO chondrule Ch-6 in LL3.15 Bishunpur

Fig. 4 .

 4 Fig. 4. Oxygen isotopic compositions of the entire dataset of chondrule olivine crystals from

Fig. 5 .

 5 Fig. 5. (A) Oxygen isotopic composition of olivine grains in chondrule Ch-6 from LL3.15

Fig. 6 .

 6 Fig.6. Gray-scale high-resolution TiO 2 X-ray maps of chondrules (A) Ch-1 from Bishunpur and

Fig. 7 .

 7 Fig. 7. ∆ 17 O values as functions of incompatible element concentrations: (A) TiO 2 , (B) Al 2 O 3 , (C) CaO, (D) MnO, and (E) NiO. 16 O-poor host olivine grains exhibit variable minor element compositions, whereas 16 O-rich relict grains define two distinct groups: (i) those with extreme 16 O enrichments (∆ 17 O < -15 ‰) are systematically Al-and Ti-poor, whereas others (ii) with ∆ 17 O ≈ -5.5 ‰ show variable minor element abundances. (F) Mg# vs. ∆ 17 O values. In all plots, the black line and gray rectangle define the average ∆ 17 O value and 2 SD range, respectively, for all host olivine grains. (∆ 17 O vs. Cr 2 O 3 is shown in Fig. S12).

Fig. 8 .

 8 Fig. 8. ∆ 18 O vs. ∆ 17 O diagram for host and relict chondrule olivine grains from OCs (red) and CCs (blue). The ∆ 18 O and ∆ 17 O values of host olivines (squares) correspond to average values

Fig. 9 .

 9 Fig. 9. Schematic representation of gas-melt interactions during the OC chondrule-forming

Fig. 10 .

 10 Fig. 10. ∆ 18 O vs. ∆ 17 O diagram of (A) the average O isotopic compositions of host olivine

  Fig. 1 962

  Fig. 10 981

  6 cps for16 O, 17 O, and 18 O, respectively. All SIMS analytical spots were checked thoroughly by scanning electron microscope, and any spots near fractures, in the mesostasis, or not completely within olivine grains were excluded from the dataset. Isotopic compositions are reported in delta notation relative to Vienna standard mean ocean water

Acknowledgments

Nordine Bouden is thanked for technical assistance with SIMS measurements. We are grate l to the s m national d'Histoire nat relle o Paris or loaning the Bishunpur and Semarkona samples. Tim Fagan, Arshad Ali and an anonymous reviewer are thanked for constructive comments and Associate Editor Yuri Amelin for careful editing. This research was o nded by l'Agence Nationale de la Recherche (ANR) thro gh grant CASSYSS ANR-18-CE31-0010-01 (PI Johan Villeneuve). This is CRPG contribution #2771.

Research Data

Original data from this study are available on the Ordar database: https://doi.org/10.24396/ORDAR-69

(2020), and [START_REF] Williams | Chondrules reveal large-scale outward transport of inner Solar System materials in the protoplanetary disk[END_REF]. In (B), errors on ∆ 18 O and ∆ 17 O, when given, are smaller than the symbol size; bulk chondrule O isotopic compositions are from [START_REF] Clayton | Oxygen isotopic compositions of chondrules in Allende and ordinary chondrites[END_REF][START_REF] Clayton | Oxygen isotope studies of ordinary chondrites[END_REF], Clayton andMayeda (1985, 1999), [START_REF] Mayeda | Oxygen, silicon, and magnesium isotopes in ningqiang chondrules[END_REF], [START_REF] Rubin | Oxygen isotopes in chondrules and coarse-grained chondrule rims from the Allende meteorite[END_REF][START_REF] Weisberg | The CR (Renazzo-type) carbonaceous chondrite group and its implications[END_REF][START_REF] Jones | Oxygen isotope heterogeneity in chondrules from the Mokoia CV3 carbonaceous chondrite[END_REF]. Chondrule fractions in the different chondrite groups are from [START_REF] Scott | Chondrites and Their Components[END_REF] and normalized to 100 %.