# Lack of resolvable titanium stable isotopic variations in bulk chondrites

Zhengbin Deng, Frederic Moynier, Kirsten van Zuilen, Paolo Sossi, Emily

Pringle, Marc Chaussidon

► To cite this version:

Zhengbin Deng, Frederic Moynier, Kirsten van Zuilen, Paolo Sossi, Emily Pringle, et al.. Lack of resolvable titanium stable isotopic variations in bulk chondrites. Geochimica et Cosmochimica Acta, 2018, 239, pp.409-419. 10.1016/j.gca.2018.06.016. insu-02901105

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1 Lack of resolvable titanium stable isotopic variations in bulk chondrites

2 Zhengbin Deng<sup>a, *</sup>, Frédéric Moynier<sup>a, b</sup>, Kirsten van Zuilen<sup>a</sup>, Paolo A. Sossi<sup>a</sup>, Emily A.

3 Pringle<sup>a</sup>, Marc Chaussidon<sup>a</sup>

4 <sup>a</sup> Institut de Physique du Globe de Paris, Université Paris Diderot, Université Sorbonne Paris

5 Cité, CNRS UMR 7154, 1 rue Jussieu, 75005, Paris, France.

6 <sup>b</sup> Institut Universitaire de France, Paris, France.

7 * Corresponding author: deng@ipgp.fr

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9 Abstract

10 Titanium and calcium are both refractory lithophile elements. Significant stable isotopic
11 variations on Ti and Ca have been documented within calcium, aluminum-rich inclusions
12 (CAIs) in carbonaceous chondrites. To trace the condensation history of Ti in the solar
13 nebula, we conducted a high-precision double-spike Ti stable isotopic study on a large set of
14 chondrites. The studied chondrites have a homogeneous bulk Ti stable isotopic composition
15 (δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> = -0.069 ± 0.018‰, 2σ, n = 22, i.e., the per mil deviation of the <sup>49</sup>Ti/<sup>47</sup>Ti
16 ratios relative to the IPGP-Ti reference material). The homogeneity across eleven chondrite
17 groups implies that chondrites have acquired, through the condensation sequence at
18 equilibrium, the average stable isotopic composition of Ti in the refractory solids that
19 condensed early in the solar nebula. In contrast, the light Ca stable isotopic compositions of
20 bulk chondrites can be attributed to either the presence of CAIs (CV-, CM- and CO-type) or
21 parent-body aqueous alteration (CR- and CI-type).
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# 1. Introduction

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Chondrites are undifferentiated meteorites with chemical compositions (except H, He, Li, C, N, O and noble gases) close to those of the solar photosphere (in particular CI-type chondrites; Anders and Grevesse, 1989). Since the discovery of oxygen isotopic anomalies in carbonaceous chondrites (Clayton et al., 1973), mass-independent isotopic variations of various elements such as Ca (e.g., Niederer and Papanastassiou, 1984; Schiller et al., 2015; Simon et al., 2009; Huang and Jacobsen, 2017; Jungck et al., 1984), Ti (e.g., Niederer et al., 1985; Trinquier et al., 2009; Niemeyer and Lugmair, 1981; Niemeyer and Lugmair, 1984), Cr (e.g., Trinquier et al., 2008; Birck and Allègre, 1985; Papanastassiou, 1986), Ni (e.g., Steele et al., 2012) or V (Sossi et al., 2017) have been used to trace the heterogeneity of the solar proto-planetary disk, the effect of early solar irradiation or to identify the materials that accreted to form the terrestrial planets (See the recent reviews in Teng et al. (2017) for other elements such as Fe, Mg, Zn, Mo, etc.). In contrast mass-dependent isotopic variations in planetary reservoirs can be used to study a number of processes, such as nebular condensation and evaporation (e.g., Niederer and Papanastassiou, 1984; Niederer et al., 1985; Simon and DePaolo, 2010), electromagnetic separation in the solar nebula (e.g., Moynier et al., 2006, 2015), syn- or post-accretion processes including metal-silicate differentiation (e.g., Shahar et al., 2011), volatile depletion (e.g., Paniello et al., 2012; Pringle et al. 2014; Day and Moynier 2014; Hin et al., 2017), magmatic differentiation (e.g., Teng et al., 2010; Sossi and O'Neill, 2017; Greber et al., 2017b) and parent-body aqueous alteration (Clayton and
Mayeda, 1999). Among these, evaporation and condensation driven by thermal events in the solar nebula are fundamental to shape the isotopic composition of early solar system materials (e.g., Niederer and Papanastassiou, 1984; Niederer et al., 1985; Simon and DePaolo, 2010; Davis et al., 1990; Luck et al. 2005; Kato and Moynier 2017; Pringle and Moynier, 2017; Hin et al., 2017). As shown by the Ca isotopic studies of aluminum-rich inclusions (CAIs) and experimental samples, the magnitude of isotopic fractionation resulting from evaporation and condensation in vacuum is proportional to the square root of the ratio of the masses of the two isotopes (Richter, 2002). This approximation holds for Ca and Ti, for which the relative mass difference, and hence isotope fractionation, is larger for Ca (g) relative to TiO₂ (g) at 2000°C (Zhang et al., 2014). Nevertheless, evaporation at lower temperatures of elements such as Si, Mg and K is subject to a smaller isotopic fractionation than predicted under vacuum, potentially due to diffusion in the gas phase (Davis et al., 1990; Richter et al., 2011; Mendybaev et al., 2013).

In the solar nebula, Ti and Ca are both refractory lithophile elements (50% T<sub>C</sub> of 1582 K for Ti and 1517 K for Ca; Lodders et al., 2003), limiting the potential for modification of their isotope signatures by evaporation/condensation. Nonetheless, it was shown that CAIs exhibited large mass-dependent isotopic variations of Ca, Ti, Mg and O, but there was no correlation between the mass-dependent isotopic variations of Ti and those of Ca (Niederer and Papanastassiou, 1984; Niederer et al., 1985). Recently, Simon et al. (2017) and Davis et al. (2018) confirmed the different stable isotopic behaviors of Ti and Ca in CAIs: Ca tends to be enriched in the lighter isotopes while Ti can be both isotopically heavy or light. In contrast
64 to the isotopic variations observed in CAIs by Simon et al. (2017), 3‰/amu for Ca and
65 0.7‰/amu for Ti, and by Niederer et al. (1985), 2.6‰/amu for Ca and 1.2‰/amu for Ti, the
66 magnitude of isotopic fractionation is larger for Ca (5‰/amu) and Ti (4‰/amu) in the CAI
67 samples from Davis et al. (2018).

68 The distinction in the mass-dependent isotope fractionation of Ti and Ca is borne out in
69 the composition of carbonaceous chondrites at the bulk scale. Individual carbonaceous
70 chondrite groups are characterized by a progressive enrichment in the lighter Ca isotopes in
71 the order CO < CM ≤ CI ≤ CR ≤ CV (Simon and DePaolo, 2010; Valdes et al., 2014;
72 Amsellem et al., 2017; Huang and Jacobsen, 2017). The CR- and CV-type chondrites are up
73 to 0.25‰/amu lighter in Ca than the bulk silicate Earth (BSE; Huang et al., 2010; Kang et al.,
74 2017). Titanium isotopic studies of bulk chondrites are very limited with only two studies
75 reporting a total of 6 data for carbonaceous chondrites. Williams (2015) found that both
76 Murchison and Allende chondrites were isotopically heavier than terrestrial basalts, whereas
77 Greber et al. (2017a) report no resolvable Ti stable isotopic variations within a precision of ±
78 0.02‰/amu for Lancé (CO), Murray (CM), Orgueil (CI) and Allende (CV), which are similar
79 to terrestrial basalts. Greber et al. (2017a) inferred that the Ca stable isotopic variations in
80 bulk chondrites could be explained by the varying abundances of CAIs. While this
81 conclusion may work for chondrite samples showing high contents of CAIs (e.g., the CV-
82 and CM-type), it cannot explain the ~0.1-0.2‰/amu isotopically lighter Ca in CI- and
83 CR-type chondrites compared to CO-type, ordinary and enstatite chondrites (Valdes et al.,
84 2014) because these groups are CAI-poor (≈ 0%; Hezel and Palme, 2008). The origin of Ca
stable isotopic variations in bulk carbonaceous chondrites is puzzling since, among the most
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abundant elements (e.g., oxygen, magnesium, silicon, calcium and iron) oxygen is the only
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other element that shows significant mass-dependent isotopic variation among meteorite
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classes (Clayton et al., 1988; Teng et al., 2010; Sossi et al., 2016).
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To understand the stable isotopic behaviors of Ti in chondritic materials, a large set of
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chondrite samples were analyzed for their Ti isotopic compositions by a <sup>47</sup>Ti-<sup>49</sup>Ti double
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spike technique. The new Ti isotopic data allow us to evaluate the processes that may have
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induced Ti variations in chondrites, and further trace the condensation history of Ti in the
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solar nebula.
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## 2. Samples and analytical methods

### 2.1. *Samples*

*Terrestrial samples.* Four international geological reference materials from the U.S.
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Geological Survey, including a Hawaiian basalt (BHVO-2), an Icelandic basalt (BIR-1), a
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Columbia River basalt (BCR-2) and a Guano Valley andesite (AGV-1), were analyzed. The
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OL-Ti standard used in Millet and Dauphas (2014) and Greber et al. (2017a) was calibrated
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relative to the IPGP-Ti standard (Table 1).
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*Chondrites.* Chondrites studied here include one CI-chondrite (Orgueil, CI1), two CM
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(Murchison, CM2; Cold Bokkeveld, CM2), three CO (Ornans, CO3.4; Lancé, CO3.5; and
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Isna, CO3.8), two CV (Allende, CV3; and Vigarano, CV3), one CK (Karoonda, CK4), two
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CR (RBT04133, CR2; A881595, CR2), one CH (PCA91467, CH3), four L (Hallingeberg,
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L3.4; Saratov, L4; Tedjera, L5; and l'Aigle, L6), two LL (Olivenza, LL5; and Cherokee

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Springs, LL6), one EL (Khairpur, EL6) and three EH (Sahara 97096, EH3; GRO95517, EH3;

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and Indarch, EH4) chondrites (Table 2).

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## 2.2. Methods

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### 2.2.1. Sample digestion

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Three different methods for sample digestion were tested, for all of them, meteorite

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pieces of ~1 g were crushed into fine-grained powders (200-300 mesh, i.e., with grain size ≤

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75 µm) using an agate mortar and pestle.

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#### *HF-HNO<sub>3</sub> hot-plate digestion.*
About 6 to 20 mg of sample powder containing 5-22 µg

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Ti were weighed into 7 ml Savillex PFA beakers, and 2 mL 26 M HF and 1 ml 16 M HNO<sub>3</sub>

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were added and left overnight at room temperature before being evaporated to dryness at

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~100 °C. Subsequently, 2 ml 26 M HF and 1 ml 16 M HNO<sub>3</sub> were added and the closed

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beakers were placed on a hot plate at ~100 °C for three days. After evaporation to dryness,

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the sample residues were dissolved in 3 ml 6M HCl at ~130 °C for three days to decompose

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the fluorides that formed during HF digestion.

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#### *Parr bomb digestion.*
Sample powders of 8-25 mg containing 7-21 µg were weighed into

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23 ml PTFE beakers. Subsequently, 2 ml 26 M HF and 1 ml 16 M HNO<sub>3</sub> were added before

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placing the PTFE beakers into stainless-steel digestion vessels (Parr bombs). High-pressure

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digestion was achieved by heating the sealed vessels within a ventilation oven at 140 °C for

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two days. Afterwards, the PTFE beakers were taken out and the samples evaporated to
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dryness, before being dissolved in 3 ml 6 M HCl in the ventilation oven at 140 °C for two
days for fluoride decomposition.

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*Alkali Fusion.* Solutions of the digested chondrites including samples of Orgueil, Murchison, Ornans, Lancé, Allende, Vigarano, A881595, Hallingeberg, Saratov, Tadjena, l'Aigle, Olivenza and Cherokee Springs, were the same as used in Pringle et al. (2013).

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Another set of chondrite samples, including samples of Murchison, Cold Bokkeveld, Allende, Lancé, Isna, Vigarano, l'Aigle, Sahara 97096, GRO95517 and Indarch, were freshly dissolved at IPGP following the alkali fusion protocol of Pringle et al. (2013) (Table 2). For all the samples, about 7 to 15 mg of sample powder were weighed into Ag crucibles with addition of ~200 mg NaOH pellets (99.99% trace metal basis, Sigma Aldrich Company).

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Fusion was conducted in a furnace in air at ~720 °C for 15 minutes. The fused samples were
finally dissolved in about 1 M HNO₃ at room temperature.

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2.2.2. Chromatographic Ti purification

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Before chromatographic purification, an adequate amount of ⁴⁷Ti-⁴⁹Ti double spike (see below) was added to an aliquot of each dissolved sample after the Ti concentration was determined by a Agilent 7900 Series Inductively-Coupled-Plasma Mass-Spectrometer (ICP-MS) at IPGP. Since high-precision mass-independent Ti isotopic compositions of bulk chondrites have been well documented in Trinquier at al. (2009) and Zhang et al. (2012), only spiked aliquots were processed in this study. The spiked solutions were placed in closed beakers on a hot plate at about 100 °C for at least one hour, to ensure sufficient equilibration
between sample and double spike, and afterwards evaporated to dryness. The titanium purification was modified from the two-step protocol described in Zhang et al. (2011). To avoid using large amounts of DGA resin, the order of the chromatographic steps was inverted (Protocol I). The first column was custom-made from a heat-shrinkable Teflon tube and the resin bed (0.6 cm inner diameter × 4 cm length) was filled with 1.1 cm³ chloride-form Bio-Rad AG1-X8 resin (200-400 mesh). The samples were loaded in 0.5 ml 4 M HF and the matrix (mostly alkali and transition metals, including Fe) was removed with additional 9.5 ml 4 M HF. Titanium was then eluted in 5 ml 6 M HCl + 0.01 M HF together with Ca, V, Zr, Hf, Al, Sr, Ba and Mg. The samples were dissolved in 16 M HNO₃ and dried, twice, to remove the remaining traces of HF and HCl. The second column, also made from heat-shrinkable Teflon (0.45 cm diameter × 1.3 cm length), was filled with 0.2 cm³ Eichrom DGA resin (50-100 µm particle size). The samples were loaded in 100 µl 12 M HNO₃ and the remaining matrix elements were removed by addition of 900 µl 12 M HNO₃. The final Ti cut was collected in 600 µl MilliQ H₂O (Supplementary Table S1). After chemistry, the purified samples were evaporated and organic particles derived from the resins were decomposed by fluxing with 16 M HNO₃ at about 120 °C overnight.

Protocol I was tested with (terrestrial) geological reference materials and Ti yields of typically >90% were achieved. However, some Ti elution cuts still contained small amounts of Fe (Fe/Ti ≈ 0.1–1). Furthermore, the Ti yields for some chondrite samples were as low as 20% (data not included in this study). Titanium was likely lost after the first column due to the fluoride formation of remaining Mg. Although the double spike is able to correct for
isotope fractionations induced by incomplete recovery, a second protocol (Protocol II) was set up for extraterrestrial samples to increase the Ti yields. As Fe competes with Ti on the DGA resin and the capacity of the resin is easily exceeded by the loaded amount of sample matrix, Fe was first removed from the matrix by a preceding column (0.6 cm diameter x 4 cm length) using AG1-X8 resin. The samples were loaded in 0.5 ml 6 M HCl, and Ti (plus other matrix elements) was immediately collected with in total 6 ml 6M HCl, while Fe remained on the resin. After evaporation, the samples were dissolved in 12 M HNO₃ and subjected to the DGA column to remove especially Ca, Cr and V as described above. In the last step of Protocol II, the Mg-free sample cuts were finally passed through an AG1-X8 column with 4 M HF (Supplementary Table S2). Organic compounds in the dried samples that were released from the resins were digested in 16 M HNO₃ at about 120 °C overnight. Typical Ti blanks for the both column chemistry protocols were < 2 ng, which is negligible compared to the loaded amount of natural Ti (≥1.5 µg) and the typical Ti yield after chemistry (≥ 80%) (Table S6).

### 2.2.4. Ti reference material and <sup>47</sup>Ti-<sup>49</sup>Ti double spike

A reference material for Ti isotope analyses (hereafter referred as IPGP-Ti) was prepared from a Ti ICP standard solution (1000 µg/ml PlasmaCal, SCP Science, Lot SC7186430). IPGP-Ti was diluted to about 10 µg/ml and stored in 1 M HNO₃ + 0.01 M HF.

The high isotopic purity spikes were purchased from CortecNet (Voisins-le-Bretonneux, France): <sup>47</sup>Ti (95.7%) and <sup>49</sup>Ti (93.3%). The single spikes were digested in about 20 M HF. Optimal double spike composition and double spike to sample ratio were calculated using the
double spike toolbox (Rudge et al., 2009). The two single spikes were mixed accordingly and the double spike further diluted to a concentration of about 5 µg/ml Ti ($^{47}$Ti + $^{49}$Ti), stored in 1 M HNO$_3$ + 0.01 M HF. The $^{47}$Ti-$^{49}$Ti double spike was calibrated relative to IPGP-Ti. First, pure solutions of IPGP-Ti and double spike were measured separately to estimate their Ti isotope abundances. Chromium was used as a dopant to internally correct for instrumental mass bias with a fixed $^{53}$Cr/$^{52}$Cr ratio of 0.1134 (de Laeter et al., 2003). In a second step, nine aliquots of IPGP-Ti with increasing double spike proportions were analyzed three times each. The preliminary $^{49}/^{47}$Ti values of IPGP-Ti were calculated by conducting double spike inversion for the measured isotopic ratios, and the isotopic composition of the $^{47}$Ti-$^{49}$Ti double spike can be estimated by mass-dependently adapting the $^{49}/^{47}$Ti value of IPGP-Ti to 0 ‰. At double spike to sample ratios > 0.60, the calculated $^{49}/^{47}$Ti values of IPGP-Ti aliquots deviates from 0 ‰. Therefore, the optimized mixing ratio between double spike and IPGP-Ti ranges from 0.42 to 0.60. The calculated Ti isotopic composition of the IPGP-Ti standard and $^{47}$Ti-$^{49}$Ti double spike are provided in Supplementary Table S3.

The double spike method has been in use since the 1960s (e.g., Dodson et al., 1969; Compston and Oversby, 1969; Russell et al., 1978; Rudge et al., 2009). Niederer et al. (1985) employed a double spike to measure the Ti isotopic composition of meteorites and terrestrial rocks. As explained by Niederer et al. (1985), in order to determine the absolute Ti isotopic composition of unknown samples, a gravimetric stoichiometry of the used double spike is necessary. The method monitors the Ti isotopic fractionations in the samples relative to the
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assumed normalization value for $^{46}$Ti/$^{48}$Ti (Niederer et al., 1985) or $^{49}$Ti/$^{47}$Ti (here) in the Ti standard, and only the differences in Ti isotopic fractionations are absolute.

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## 2.2.5. Mass spectrometry

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The dried Ti elution cuts after chemistry were dissolved in 0.5 M HNO$_3$ + 0.0015 M HF for analyses on the Thermo Scientific Neptune Multi-Collection Inductively-Coupled-Plasma Mass-Spectrometer (MC-ICP-MS) housed at IPGP. Traces of HF were used to stabilize Ti in dissolution. Sample solutions were introduced via an APEX HF desolvating nebulizer (Elemental Scientific Inc., USA), used without spare gas and with an uptake rate of 70 µl/min. Typical sensitivity was 17-19 V on $^{48}$Ti$^+$ (using a 10$^{11}$ Ω resistor) for a solution containing 300 ppb of Ti measured under medium mass resolution (M/ΔM ≈ 5800). Two sample introduction protocols were used to calibrate the OL-Ti standard relative to the IPGP-Ti standard, i.e., 1 ppm solution introduced via a quartz dual cyclonic spray chamber and 300 ppb solution via an APEX HF desolvating nebulizer. Between two analyses, Ti was washed out by a first rinse with 1.2 M HNO$_3$ + 0.0015 M HF, followed by a second rinse with 0.5 M HNO$_3$ + 0.0015 M HF, until a typical background of 2-5 mV on $^{48}$Ti$^+$ was reached.

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Data acquisition consisted of 100 cycles with an integration time of 8 s. The signals of $^{44}$Ca$^+$, $^{46}$Ti$^+$, $^{47}$Ti$^+$, $^{48}$Ti$^+$, $^{49}$Ti$^+$ and $^{50}$Ti$^+$ were simultaneously detected in static mode. $^{44}$Ca$^+$ intensities were used to correct for interferences of $^{46}$Ca and $^{48}$Ca on $^{46}$Ti and $^{48}$Ti, respectively. The instrumental mass fractionation factor determined for Ti for each

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measurement cycle by double spike data reduction (see below) was applied to the natural Ca isotopic ratios ($^{44}$Ca/$^{46}$Ca = 657.03 and $^{44}$Ca/$^{48}$Ca = 11.14; Zhang et al., 2011), and the estimated $^{46}$Ca$^{+}$ and $^{48}$Ca$^{+}$ intensities were subtracted from the total signals on masses 46 and 48. To avoid measurements in dynamic mode, signals of $^{51}$V$^{+}$ and $^{52}$Cr$^{+}$ were not monitored and interferences of $^{50}$V and $^{50}$Cr on $^{50}$Ti could not be corrected. Thus, $^{50}$Ti was not used for further data reduction. Due to the use of a quartz injector and plasma torch in combination with HF, isobaric interferences from silicon oxides and fluorides, e.g., $^{28}$Si$^{16}$O$^{+}$ on $^{44}$Ca$^{+}$, $^{30}$Si$^{16}$O$^{+}$ on $^{46}$Ti$^{+}$ and $^{28}$Si$^{19}$F$^{+}$ on $^{47}$Ti$^{+}$, occurred. These polyatomic interferences were resolved in medium resolution (M/ΔM ≈ 5800) and the interference-free signals were measured at the low mass of the peaks for masses 44, 46 and 48 (Supplementary Table S4). Polyatomic interferences on $^{48}$Ti$^{+}$ ($^{30}$Si$^{18}$O$^{+}$ and $^{29}$Si$^{19}$F$^{+}$) and $^{49}$Ti$^{+}$ ($^{30}$Si$^{19}$F$^{+}$) were found negligible and data were acquired at center peaks (Fig. S1).

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2.2.6. Data reduction and notation

Data reduction was accomplished with the IsoSpike software (Creech and Paul, 2015).

Signals of $^{46}$Ti, $^{47}$Ti, $^{48}$Ti and $^{49}$Ti after Ca correction were used for double spike inversion.

Within each analysis, statistic outliers among 100 cycle measurements that scatter beyond 2-sigma were identified and removed from double spike inversion. The measured results for the samples without Ti isotopic anomaly are supposed to follow:

$$R_{sample}^{i/k} = R_{standard}^{i/k} \left( \frac{m_i}{m_k} \right)^{\alpha} \qquad (1)$$
$$251 \qquad R_{\text{measured}}^{i/k} = \left[ \left(1 - \lambda\right) R_{\text{standard}}^{i/k} \left( \frac{m_i}{m_k} \right)^{\alpha} + \lambda R_{\text{spike}}^{i/k} \right] \left( \frac{m_i}{m_k} \right)^{\beta} \qquad (2)$$

with *i* the Ti isotope of interest (e.g., ⁴⁶Ti, ⁴⁸Ti and ⁴⁹Ti), and *k* the Ti isotope used as the denominator (e.g., ⁴⁷Ti), $R_{\text{measured}}^{i/k}$, $R_{\text{standard}}^{i/k}$ and $R_{\text{spike}}^{i/k}$ the isotopic ratios of measured mixture, standard and spike, respectively, and *m* the atomic mass of isotope *i* or *k*. $\alpha$ is the mass-dependent Ti isotopic fractionation in the sample relative to standard, and $\beta$ represents the instrumental mass bias. $\lambda$ is the mass proportion of isotope *k* from the spike in the sample-double spike mixture.

However, since chondrites exhibit isotopic anomalies on ⁴⁶Ti, ⁴⁸Ti and ⁵⁰Ti (Niederer et al., 1985; Trinquier et al., 2009; Zhang et al., 2012; Niemeyer and Lugmair, 1981; Niemeyer and Lugmair, 1984), their stable isotopic compositions may deviate from the terrestrial mass-dependent fractionation line on which the reference material IPGP-Ti lies (Greber et al., 2017a). To account for this deviation, the assumed normalization values of IPGP-Ti have to be adapted for the anomalies for each individual sample and the $\delta^{49/47}$Ti values of chondrites have to be reduced relative to the adapted normalization values:

$$265 \qquad R_{\text{standard-adapted}}^{i/k} = R_{\text{standard}}^{i/k} \left(1 + \varepsilon^{i/k} / 10^4\right) \qquad (3)$$

with $\varepsilon^{i/k}$ the mass-independent Ti isotopic fractionation on the isotopic ratio of isotope *i* to *k* and $R_{\text{standard-adapted}}^{i/k}$ the adapted normalization values for the IPGP-Ti standard. After this, the adapted normalization values of IPGP-Ti would lie on the same mass-dependent fractionation line as the samples showing isotopic anomalies. The double spike inversion was conducted on the results of the double spiked samples to determine the mass-dependent Ti
271 isotopic fractionations by replacing $R_{standard}^{i/k}$ with $R_{standard-adapted}^{i/k}$ in Eq. (2). In this study, 272 mass-independent Ti isotopic data from Trinquier at al. (2009) and Zhang et al. (2012) were 273 used. For the samples without available mass-independent isotopic data, the average values 274 of the corresponding meteorite groups were used. This protocol is principally the same as the 275 one used for Ba isotopes in Eugster et al. (1969), i.e., the results of the un-spiked samples 276 were normalized onto the assumed values of the Ba standard, and the normalized un-spiked 277 sample compositions and the results from the double spiked samples were combined to run a 278 double spike inversion to calculate the mass-dependent Ba isotopic fractionations. 279

While the $^{47}$Ti-$^{49}$Ti double spike has been used in this study, the analytical results here 280 have been converted into $^{49}$Ti/$^{47}$Ti ratios since (i) this data reporting manner discriminates 281 mass-dependent Ti isotopic fractionations from isotopic anomalies on $^{46}$Ti and $^{48}$Ti (Trinquier 282 et al., 2009; Zhang et al., 2012) and (ii) a delta notation on $^{49}$Ti/$^{47}$Ti ratio has been adopted by 283 the most recent studies on Ti stable isotopic variations (Millet and Dauphas, 2014; Millet et 284 al., 2016; Greber et al., 2017a). As such, the data are reported in the $\delta$-notation relative to 285 IPGP-Ti for $^{49}$Ti/$^{47}$Ti ratio: 286

$$ \delta^{49/47} \mathrm{Ti}_{\mathrm{IPGP-Ti}} = \left[ \frac{\left( \frac{^{49}\mathrm{Ti}}{^{47}\mathrm{Ti}} \right)_{\mathrm{sample}}}{\left( \frac{^{49}\mathrm{Ti}}{^{47}\mathrm{Ti}} \right)_{\mathrm{IPGP-Ti}}} - 1 \right] \times 1000. \quad (4) $$

The isotopic differences between Ti standards from different laboratories are expressed 287 in $\‰$:

$$ \Delta^{49/47} \mathrm{Ti}_{\mathrm{standard1-standard2}} = \left[ \frac{\left( \frac{^{49}\mathrm{Ti}}{^{47}\mathrm{Ti}} \right)_{\mathrm{standard1}}}{\left( \frac{^{49}\mathrm{Ti}}{^{47}\mathrm{Ti}} \right)_{\mathrm{standard2}}} - 1 \right] \times 1000. \quad (5) $$
The spiked IPGP-Ti standard was measured after every second sample. After the $\delta^{49/47}$Ti values of both IPGP-Ti standard and samples were calculated by double spike inversion, the $\delta^{49/47}$Ti values for samples were further normalized against the average $\delta^{49/47}$Ti values of the preceding and succeeding bracketing IPGP-Ti standards. This normalization can reduce the effects of (i) the short-term fluctuations that probably come from the changes in instrumental mass bias $\beta$ due to the instrumental instability, and (ii) the different molecular interferences between sessions as the results of the small tailing effects from $^{30}$Si$^{18}$O$^{+}$, $^{29}$Si$^{19}$F$^{+}$ and $^{30}$Si$^{19}$F$^{+}$.

For the data set of geological reference materials, the long-term external precision was estimated by calculating the 'pooled' standard deviation ($2s_p$), i.e., $\pm 0.027\%$ on the $^{49}$Ti/$^{47}$Ti ratio:

$$s_p = \sqrt{\frac{\sum_{i=1}^{k} (n_i - 1)s_i^2}{\sum_{i=1}^{k} (n_i - 1)}} \quad (6)$$

where $n_i$ is the number of repeated measurements of each sample $i$ and $s_i^2$ their variance. This suggests that the upper limit of the typical uncertainty on the measured $\delta^{49/47}$Ti is $\pm 0.027\%$.

Since each sample analysis has been bracketed by the analyses of the IPGP-Ti standard, the short-term precision was quoted here, i.e., using the 2se values of the measurement duplicates as the analytical uncertainties on the average $\delta^{49/47}$Ti$_{IPGP-Ti}$ values of the rock standards and chondrites. Since the Ti isotopic anomalies of chondrites have been previously determined with a precision of $\pm 0.05$ on $\varepsilon^{46}$Ti (2se) in Trinquier et al. (2009) and Zhang et al. (2012), the isotopic anomaly correction would not significantly affect the reported analytical uncertainties for the studied chondrites.
310

311

## 3. Results

312

### 3.1. Tests for the possible sources of analytical artifacts

313

#### 3.1.1. Sample digestion

314

Incomplete sample digestion may cause biased Ti isotope data, when minerals inert towards chemical attacks bear highly fractionated Ti isotopic compositions. Possible effects of the digestion methods on the Ti isotope measurements were tested by digesting aliquots of powders of several samples by two or more of the above described methods. In general, the $\delta^{49/47}$Ti values are in excellent agreement within analytical uncertainty (Fig. 1). Isna (CO3.8) and Allende (CV3), however, cannot be reproduced within analytical uncertainty between different aliquots (Fig. 1). Niederer et al. (1985), Trinquier at al. (2009) and Zhang et al. (2012) have shown that CAIs have considerably different Ti isotopic anomalies compared to chondrules and matrix. Therefore, CO- and CV-type chondrites that are enriched in CAIs are particularly prone to isotopic heterogeneities, and isotope anomaly data may vary amongst sample aliquots, based on the proportion of CAIs. As there is no systematic trend in the $\delta^{49/47}$Ti data with digestion method and the dissolution aliquots of the Isna and Allende meteorites were dissolved from the powders crushed from different sample pieces, the offset may be a result of whole-rock heterogeneity rather than of incomplete digestion.

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

#### 3.1.2. Titanium recovery
Column yields for *Protocol II* were > 80% for all samples, and in some cases the recovery was twice as large as for *Protocol I* (Fig. S2A). Within an external measurement precision of ± 0.03 to 0.08‰ for chondrite samples, aliquots processed by using the two protocols have indistinguishable δ<sup>49/47</sup>Ti values (Fig. S2B). Thus, Ti isotope data acquired for samples with column yields as low as ~40% were included in this study. In the case of the Allende chondrite, the recovery rates of all aliquots were >80%. The higher δ<sup>49/47</sup>Ti value for the dissolution aliquot purified following *Protocol II* is therefore likely the result of sample heterogeneity (Figs. S2A-B). As such, the similarity between low- and high-yield replicates demonstrates that the double spike method here can correct for the incomplete titanium recovery as low as 40%. For samples with high Mg concentrations, such as chondrites, the three-step chromatographic protocol is recommended in order to achieve a high Ti recovery.
For terrestrial igneous rocks, however, the shorter two-step protocol is sufficient with Ti yields > 90% (Table 1), while lowering the procedure blank and the amount of time required for sample purification.

344

3.1.3. Sample impurity

Aliquots of IPGP-Ti were doped with varying amounts of Fe, Ca and Si to test for isobaric and non-spectral matrix effects. It appears that non-spectral matrix effects of Fe on the measured Ti isotopic ratios are negligible for Fe/Ti ratios ≤10 (Fig. 2). Isobaric interferences of Ca can successfully be corrected for Ca/Ti ratios ≤ 0.1. Significant amounts of Si (Si/Ti >0.1) cause systemically lower Δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> values due to the tailing effects of
351

$^{28}$Si$^{19}$F+ (Fig. 2). The effect of Si on the Ti measurements might be relevant especially for the

352

samples digested by alkali fusion, as dissolved Si remains in solution. However, different

353

digestion methods result in indistinguishable $\Delta^{49/47}\text{Ti}_{\text{IPGP-Ti}}$ values. Furthermore, small

354

amounts of Si from the quartz glass injector and torch are considered to produce Si/Ti ratios

355

<< 0.1 (Fig. S1; Supplementary Table S5). Thus, the effects of the tested impurities after

356

chromatographic purification are negligible on the $\delta^{49/47}\text{Ti}$ values in this study.

357

Normally, the isobaric interferences from $^{46}\text{Ca}^+$ and $^{48}\text{Ca}^+$ on $^{46}\text{Ti}^+$ and $^{48}\text{Ti}^+$,

358

respectively, can be corrected by monitoring the intensity of $^{44}\text{Ca}^+$ and applying the natural

359

Ca isotopic ratios. However, if a small amount of the unnatural and highly isotopically

360

fractionated Ca was present in the used double spike, this Ca correction manner might lead to

361

either the over- or under-correction of the Ca isobaric interferences. A systematic drift on the

362

$\delta^{49/47}\text{Ti}$ values would be expected upon a fact that: The spiked samples were cleaned after

363

chromatographic purification, but the spiked bracketing IPGP-Ti standard was not. To test

364

this, we measured a spiked IPGP-Ti solution through the DGA column against the spiked

365

bracketing IPGP-Ti standard, which provide a resolvable $\Delta^{49/47}\text{Ti} = +0.022 \pm 0.009\%_o$ (2se, n

366

= 9) (Table 1). The measurements on the used double spike show that the intensities are ≈ 4

367

mV on $^{44}\text{Ca}^+$ while ≈ 18-20 V on $^{47}\text{Ti}^+$ and $^{49}\text{Ti}^+$. Therefore, we suggest here that the small

368

drift is likely the result of a remnant of the isotopically non-normal Ca that came in as part of

369

the isotope separation procedure. This systematic drift is unlikely to alter the Ti isotopic

370

differences between samples within an individual laboratory. Nonetheless, if aiming for

371

high-precision inter-laboratory comparison, the purification on both the samples and
372

bracketing IPGP-Ti standard would be necessary. Thus, all the δ<sup>49/47</sup>Ti values in this study

373

were corrected for this drift with error propagation.

374

375

## 3.2. Inter-laboratory comparison

376

While the measurements with spray chamber show a δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> = -0.158 ± 0.008‰

377

(2se) for the OL-Ti standard, the analyses with Apex provide a slightly higher δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub>

378

value of -0.140 ± 0.011‰ (2se). Here the latter value is preferred since all the samples have

379

been measured with Apex. After the correction of the Ca effects from double spike in Section

380

3.1.3, resolvable Ti isotopic variations can be observed for BIR-1 (δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> = -0.188 ±

381

0.010‰, 2se), BCR-2 (δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> = -0.148 ± 0.010‰, 2se), BHVO-2 (δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> =

382

-0.129 ± 0.011‰, 2se) and AGV-1 (δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> = -0.060 ± 0.012‰, 2se) (Fig. 3; Table 1;

383

Supplementary Table S6). Replicates of the rock standards imply that our method is able to

384

resolve the subtle Ti stable isotopic fractionation in nature, i.e., ~0.010‰ on δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub>

385

within 95% confidence interval. These values for the rock standards BIR-1, BCR-2, BHVO-2

386

and AGV-1 match well with the reported values in Williams (2015), Millet and Dauphas

387

(2014) and Millet et al. (2016) within errors (Fig. 3; Table 1).

388

389

## 3.3. Stable Ti isotopic compositions of bulk chondrites

390

The δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> values of individual chondrite samples vary within a range of 0.176‰

391

(δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> of -0.162 ± 0.011‰ to +0.014 ± 0.024‰; Table 2). Nonetheless, the average

392

values for individual chondrite groups (CI, CM, CO, CV, CR, CH, CK, L, LL, EL and EH)
are indistinguishable within the analytical uncertainty ($\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}} = -0.070 \pm 0.015\text{‰}$, 2se, n = 11) (Table 2; Supplementary Table S6). Furthermore, the average $\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}}$ value of the individual chondrite samples ($\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}} = -0.069 \pm 0.018\text{‰}$, 2se, n = 22) is similar to the average chondrite value from Williams (2015) ($\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}} = -0.090 \pm 0.028\text{‰}$, 2se, n = 6), while slightly heavier when compared to the bulk silicate Earth estimate from Millet et al. (2016) ($\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}} = -0.133 \pm 0.014\text{‰}$, 2se; n = 26) and the chondrite average from Greber et al. (2017a) ($\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}} = -0.132 \pm 0.015\text{‰}$, 2se; n = 16 with 4 CC, 3 EC and 9 OC) (Fig. 4; Supplementary Table S7).

401

## 4. Discussion

### 4.1. *Homogeneous Ti stable isotopic compositions of chondrites*

While the rock standards show similar $\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}}$ values in this study, Williams (2015) and Millet and Dauphas (2014), the chondrites from this study and Williams (2015) are ~0.040-0.060‰ higher in $\delta^{49/47}\text{Ti}_{\text{IPGP-Ti}}$ values than those from Greber et al. (2017a). The presence of this inter-laboratory discrepancy motivated us to carry out a series of tests to clarify the possible sources of analytical artifacts in Section 3.1, though no reason for such a discrepancy was apparent. However, it is unquestionable that the eleven studied individual chondrite groups are homogenous in Ti stable isotopic composition.

The Ti stable isotopic homogeneity for bulk chondrites with varying degrees of aqueous alteration and metamorphism implies that Ti isotopes are not affected by these processes. In contrast with the Ti stable isotopic homogeneity for bulk chondrites, the CAIs in chondrites
are characterized by much larger mass-dependent Ti isotopic variations. Seven CAI samples in Niederer et al. (1985) show an enrichment in heavy Ti isotopes compared to terrestrial rocks (+0.1‰/amu to +1.3‰/amu), and forty-nine CAIs from Allende chondrites have both positive and negative δ⁴⁹/⁴⁷TiIPGP-Ti values with an average δ⁴⁹/⁴⁷TiIPGP-Ti value of +0.20 ± 0.33‰ (2σ, n = 49; Davis et al., 2018). On average, the CAIs in CV-type chondrites can contain 15-20% of the total Ti (Hezel and Palme, 2007). Thus, the similarity of Ti stable isotopic composition across carbonaceous chondrite groups implies that CAIs in chondrites are, on average, not markedly isotopically different from other non-CAI components in Ti, even if a δ⁴⁹/⁴⁷TiIPGP-Ti range of ~7‰ has been observed in CAIs in Davis et al. (2018).

The large variation on δ⁴⁹/⁴⁷TiIPGP-Ti for individual CAIs suggests that the condensation and evaporation processes that formed the CAIs in the early solar nebula can significantly fractionate Ti stable isotopes (Niederer et al., 1985; Zhang et al., 2014; Davis et al., 2018). As a refractory lithophile element, most Ti would enter the condensates after 5% of CI chondritic composition was condensed (Davis and Richter, 2003). The primary Ti-bearing condensates, e.g., perovskite and hibonite, can further equilibrate with the surrounding liquids or gases during the cooling processes of the early solar nebula. This re-equilibration would lead to the forming of other Ti-bearing components, e.g., pyroxenes or mesostasis in the chondrules of carbonaceous and ordinary chondrites (Hezel and Palme, 2007), or the sulfides or metals of enstatite chondrites (Keil, 1969). The aggregation of the varying components can result in various types of chondrites with bulk TiO₂ contents ranging from ~0.05 wt% (EH-type) to ~0.15 wt% (CV-type) (Supplementary Table S6). Thus, the Ti stable isotopic homogeneity
435

among eleven chondrite groups may imply that chondrites have inherited the average stable isotopic composition of the early condensed Ti through the efficient re-equilibration between the primary refractory condensates and liquids or gases in the solar nebula.

436

437

438

439

## 4.2. Constraints on the Ca stable isotopic variations in bulk chondrites

440

While there is a Ti stable isotopic homogeneity for bulk chondrites, the CI-, CM-, CV- and CR-type chondrites exhibit lower $\delta^{44/40}\text{Ca}_{\text{NIST SRM 915a}}$ values from +0.27 ± 0.04‰ to +0.79 ± 0.09‰ (2σ) when compared to those of CO-type chondrites (+0.97 ± 0.18‰, 2σ), and ordinary and enstatite chondrites (+0.91‰ to +0.97‰) (Valdes et al., 2014; Simon and DePaolo, 2010; Amsellem et al., 2017; Huang et al., 2017). These observations demonstrate that the Ca isotopes behave differently from Ti isotopes in bulk chondrites.

441

442

443

444

445

446

### 4.2.1. Inheritance from CAIs?

447

While multiple CAIs are on average similar to bulk chondrites with respect to Ti stable isotopes (Davis et al., 2018; Niederer et al., 1985; Simon et al., 2017), the CAIs from Allende are mostly isotopically lighter in Ca ($\delta^{44/40}\text{Ca}_{\text{NIST SRM 915a}}$ down to -10.34‰) than the bulk values of Allende ($\delta^{44/40}\text{Ca}_{\text{NIST SRM 915a}}$ = -0.61‰ to -0.27‰), Allende chondrules ($\delta^{44/40}\text{Ca}_{\text{NIST SRM 915a}}$ = +0.91‰ to +1.06‰; Amsellem et al., 2017) and ordinary/enstatite chondrites (+0.91‰ to +0.97‰) (Niederer and Papanastassiou, 1984; Huang et al., 2012; Huang and Jacobsen, 2017; Simon et al., 2017; Valdes et al., 2014; Simon and DePaolo, 2010; Amsellem et al., 2017). In a gas phase above silicate liquids, Ca is present as $\text{Ca}^{0}$, while Ti mainly occurs as $\text{TiO}_{2}$ (Zhang et al., 2014), though TiO is also present in small

448

449

450

451

452

453

454

455
456

proportions (De Maria et al., 1971). The smaller relative mass difference per atomic mass

457

unit of Ti⁴⁹O₂/Ti⁴⁷O₂ with respect to Ca⁴⁴/Ca⁴⁰ reduces mass-dependent isotopic fractionation

458

of the former during evaporation (Zhang et al., 2014; Simon et al., 2017). Nonetheless, in

459

contrast with the canonical Ti stable isotope records, the light Ca isotopic compositions for

460

CAIs imply that a significant fraction of isotopically heavy Ca has been removed from the

461

CAI source materials (Niederer and Papanastassiou, 1984; Huang et al., 2012).

462

The CAIs may contribute significantly to the inventory of refractory lithophile elements

463

in bulk CV-type chondrites, as attested by the similar Rare Earth Element (REE) pattern

464

between Allende (CV3) and Group II CAIs (Huang et al., 2012). Thus, Ca isotope variations

465

in CV-type chondrites may be controlled by the modal abundance of isotopically light CAIs.

466

If so, a correlation between CAI abundances and Ca stable isotopic compositions would be

467

expected among different types of chondrites. As documented in Hezel and Palme (2008), the

468

abundances of refractory inclusions in individual carbonaceous chondrite groups follow an

469

order of CI ≈ CR < CO < CM < CV, with CI- and CR-type chondrites containing almost no

470

CAIs. Following this logic, CI- and CR-type chondrites that are CAI-free should have heavier

471

Ca stable isotopic composition compared to the CO- and CM-type chondrites, which is not

472

the case (Valdes et al., 2014; Simon and DePaolo, 2010; Amsellem et al., 2017). Therefore,

473

other mechanisms are needed to explain variation in stable isotopic composition of Ca in bulk

474

chondrites.

475

476

4.2.2. Parent-body aqueous alteration?
477

A major chemical difference between Ca and Ti is that Ca is very mobile during aqueous alteration while Ti is not (Van Baalen, 1993). Oxygen isotopic variations between CI-, CR- and CM-type chondrites show that they have experienced variable degrees of aqueous alteration in their parent bodies (Clayton et al., 1988; Clayton and Mayeda, 1999; Rowe et al., 1994; Weisberg et al., 1993). As addressed by Clayton and Mayeda (1999), the slopes (S) of individual carbonaceous chondrite groups on a triple oxygen isotope plot (relative variations of the ¹⁷O/¹⁶O ratios versus the ¹⁸O/¹⁶O ratios) can be used as an indicator of the degrees of aqueous alteration (S<sub>CV</sub> ≈ 1, S<sub>CM+CO</sub> ≈ 0.70, S<sub>CR+CH</sub> ≈ 0.59 and S<sub>CI</sub> ≈ 0.5; Clayton and Mayeda, 1999). This idea follows a logic that the anhydrous minerals of carbonaceous chondrites plot along a line with S ≈ 1 (Clayton et al., 1973), while aqueous alteration induces isotope fractionations varying along lines with S ≈ 0.5 (Clayton and Mayeda, 1999). Thus, an index for increasing aqueous alteration can be defined from oxygen isotopes in the order CV < CO < CM < CI ≤ CR.

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

The contribution from CAIs on the Ca stable isotopic inventory of carbonaceous chondrites can be subtracted by using the CAI abundance and chemical composition data from Hezel and Palme (2007; 2010), and temporarily assuming δ<sup>44/40</sup>Ca<sub>NIST SRM 915a</sub> = -0.9‰ and CaO = 18 wt% for CAIs in average. After the subtraction of the contribution of CAIs, CV-, CO- and CM-type chondrites exhibit similar Ca isotopic compositions as that of ordinary or enstatite chondrites (Valdes et al., 2014; Amsellem et al., 2017), but CR- and CI-type chondrites still have resolvable lighter Ca isotopic ratios (Fig. 5). This observation indicates that the Ca stable isotopic inventory in CR- and CI-type chondrites may have been
altered by parent-body aqueous alteration. Similar interpretations have been given to explain the different Mg isotopic composition of CI and CR chondrites from other carbonaceous chondrite groups (Hin et al., 2017), as corroborated by their high ¹⁸O/¹⁶O ratios. This interpretation is supported by the fact that the water-soluble phases from CI-type chondrite Orgueil extracted with boiling water contain up to nearly 50% of the total Ca and the main water-soluble Ca carriers are the Ca-sulfates and carbonates formed by aqueous activity in the parent body (Fredriksson and Kerridge, 1988).

## 5. Conclusions

Eleven chondrite groups (CI, CM, CO, CV, CR, CH, CK, L, LL, EL and EH-type) exhibit indistinguishable Ti stable isotopic compositions with an average δ⁴⁹/⁴⁷Ti/IPGP-Ti of -0.070 ± 0.015‰ (2σ). This homogeneity corroborates that CAIs in average should be similar to the bulk chondrites for Ti stable isotopes, and chondrites have inherited the average Ti isotopic composition of the solar system through the condensation sequence. In contrast, the large Ca stable isotopic variations in bulk chondrites are likely the combining results of (i) the incorporation of CAIs and (ii) aqueous alteration. Future characterization of the carrier phases for the light Ca stable isotopic signatures among non-CAI chondritic components will be helpful to testify whether chondrites have also sampled the average Ca stable isotopic composition from the early condensates in the early solar nebula, which has been demonstrated for Ti.
519 Acknowledgements

520 We thank Julien Moureau, Pascale Louvat, Jessica Dallas and Pierre Burckel for maintaining
521 the MC-ICP-MS and Q-ICP-MS at IPGP, John Creech for hist help with IsoSpike software,
522 and Marc-Alban Millet for sharing the OL-Ti standard. Dimitri Papanastassiou, Justin Simon
523 and two anonymous reviewers are greatly appreciated for their constructive comments on our
524 manuscript. FM acknowledges funding from the European Research Council under the H2020
525 framework program/ERC grant agreement #637503 (Pristine). FM and MC thank financial
526 support from the ANR through the Cradle project and the UnivEarthS Labex program at
527 Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02). Parts of this work
528 were supported by IPGP multidisciplinary program PARI, and by Region Île-de-France
529 SESAME Grant no. 12015908. We are also indebted to Joseph Boesenberg and Denton Ebel
530 (American Museum of National History, New York), Timothy McCoy (US National Museum
531 of Natural History, Smithsonian Institution, Washington DC), Caroline Smith (The Natural
532 History Museum, London), Alex Bevan (Western Australian Museum, Perth), Jim Karner
533 and Carl Agee (University of New Mexico, Albuquerque), Ludovic Ferriere
534 (Naturhistorisches Museum, Vienna), Philip Heck (The Field Museum, Chicago), Meenakshi
535 Wadhwa (Arizona State University, Tempe), Cecilia Satterwhite (NASA Johnson Space
536 Center, Houston) and the Comité de Gestion (Museum Nationale d'Histoire Naturelle, Paris)
537 for their generous donations of meteorite samples for this work and their confidence in our
538 analytical and scientific capabilities.
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**Table and figure captions**

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**Table 1** Titanium stable isotopic compositions of the reference materials in this study and literature.

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**Table 2** Titanium stable isotopic compositions of the chondrite samples in this study.

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**Figure 1** Titanium isotopic composition of sample aliquots digested by different methods.
Error bars indicate 2σ uncertainties (see Supplementary Table S6).

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**Figure 2** Results of matrix doping. For Ca doping, uncorrected (green) and corrected data (pink) are shown. The isobaric interferences from Si doping were not corrected, which can lead to lower δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> values when Si/Ti is > 0.1. Note: Si/Ti is << 0.1 for the unknown samples in this study after chromatographic purification. Error bars indicate 2σ uncertainties (smaller than symbol size). The inset is the zoom-in for the box field. The grey bar shows the typical precision of ± 0.027‰ for the samples with only one or two duplicates.

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**Figure 3** Comparison of results from reference materials (AGV-1, BHVO-2, BCR-2 and BIR-1) in this study with the literature data (Williams, 2015; Millet and Dauphas, 2014; Millet et al., 2016).

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**Figure 4** δ<sup>49/47</sup>Ti<sub>IPGP-Ti</sub> values of chondrites and rock standards in this study. The chondrite and rock standard data from Williams (2015), Greber et al. (2017a), Millet and Dauphas

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(2014) and Millet et al. (2016) are shown for comparison. All the data have been rescaled
onto the IPGP-Ti standard with error propagation. The average of each group of data is
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indicated with 2σ uncertainty.
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**Figure 5** Diagram showing the subtraction of CAIs on the Ca stable isotopic inventory of CI-, CR-, CM-, CO- and CV-type chondrites. This subtraction was conducted by a mass balance using parameters shown in Supplementary Table S8 (i.e., the blue arrows), by assuming that CAIs in average have a CaO content of 18 wt.% and a $\delta^{44/40}$Ca$_{NIST SRM 915a}$ value of -0.9‰. The pink labels represent the original Ca stable isotopic values while the green ones stand for the values after subtraction of CAIs. The slopes of chondrite groups defined on the triple oxygen isotope plot from Clayton and Mayeda (1999) are indicated at the bottom. The $\delta^{44/40}$Ca$_{NIST SRM 915a}$ value of ordinary and enstatite chondrites in Valdes et al. (2014) is shown as an orange bar.
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<figure><img src="image_2.png" /></figure>

Alkali fusion-Pringle2013

Alkali fusion-IPGP

Parr bomb

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

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

Ca/Ti = 0.1

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

Ca/Ti = 0.03

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

Fe/Ti = 0.1

Fe/Ti = 10

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

Fe/Ti = 5

Ca/Ti = 0.003

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

± 0.027 ‰

Si/Ti = 0.1

<figure><img src="image_9.png" /></figure>

Si/Ti = 1

<figure><img src="image_10.png" /></figure>

Si/Ti = 3

<figure><img src="image_11.png" /></figure>

Fe doping

Ca doping-corr.

Ca doping-uncorr.

Si doping
<figure><img src="image_12.png" /></figure>
<figure><img src="image_13.png" /></figure>
Blue arrows indicate the subtraction of the contribution from CAIs.

<figure><img src="image_14.png" /></figure>