High-precision Mg-isotope measurements of terrestrial and extraterrestrial material by HR-MC-ICPMS—implications for the relative and absolute Mg-isotope composition of the bulk silicate Earth

Bizzarro, Martin; Paton, Chad; Larsen, Kirsten; Schiller, Martin; Trinquier, Anne; Ulfbeck, D.

doi:10.1039/c0ja00190b

Cited by 137 publications

(190 citation statements)

References 51 publications

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“…Magnesium and chromium were purified from sample matrices by ion exchange chromatography based on protocols developed in Bizzarro et al (60) and Schiller et al (61) and adapted for the typically smaller sample sizes processed in this study. In detail, Mg was separated using a six-step purification scheme that combines cation, anion, di-éthylhexyldiglycolamide (TODGA), and Ni-spec resins (60). The Cr-rich separate was retrieved from the second step of the Mg chemical purification (60) and further processed through a two-step scheme using TODGA resin (61).…”

Section: Methodsmentioning

confidence: 99%

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Kooten

Wielandt

Schiller

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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173

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The short-lived 26 Al radionuclide is thought to have been admixed into the initially 26 Al-poor protosolar molecular cloud before or contemporaneously with its collapse. Bulk inner Solar System reservoirs record positively correlated variability in mass-independent 54 Cr and 26 Mg*, the decay product of 26 Al. This correlation is interpreted as reflecting progressive thermal processing of infalling 26 Al-rich molecular cloud material in the inner Solar System. The thermally unprocessed molecular cloud matter reflecting the nucleosynthetic makeup of the molecular cloud before the last addition of stellar-derived 26 Al has not been identified yet but may be preserved in planetesimals that accreted in the outer Solar System. We show that metal-rich carbonaceous chondrites and their components have a unique isotopic signature extending from an inner Solar System composition toward a 26 Mg*-depleted and 54 Cr-enriched component. This composition is consistent with that expected for thermally unprocessed primordial molecular cloud material before its pollution by stellar-derived 26 Al. The 26 Mg* and 54 Cr compositions of bulk metal-rich chondrites require significant amounts (25-50%) of primordial molecular cloud matter in their precursor material. Given that such high fractions of primordial molecular cloud material are expected to survive only in the outer Solar System, we infer that, similarly to cometary bodies, metal-rich carbonaceous chondrites are samples of planetesimals that accreted beyond the orbits of the gas giants. The lack of evidence for this material in other chondrite groups requires isolation from the outer Solar System, possibly by the opening of disk gaps from the early formation of gas giants. molecular cloud | outer Solar System | metal-rich chondrites | isotopes | chondrite accretion regions L ow-mass stars like our Sun form by the gravitational collapse of the densest parts of molecular clouds comprising stellarderived dust and gas. Collapsing clouds swiftly evolve into deeply embedded protostars that rapidly accrete material from their surrounding envelopes via a protoplanetary disk (1), in which planetesimals and planetary embryos form over timescales of several million years (2). Chondritic meteorites (chondrites) are fragments of early-formed planetesimals that avoided melting and differentiation and, therefore, provide a record of the earliest evolutionary stages of the Sun and its protoplanetary disk. Most chondrites contain calcium−aluminum-rich inclusions (CAIs) and chondrules, which formed by high-temperature processes that included evaporation, condensation, and melting during short-lived heating events (3). CAIs represent the oldest dated solids and, thus, define the age of the Solar System at 4,567.3 ± 0.16 Ma (4). It is inferred that CAIs formed near the proto-Sun during a brief time interval (<0

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Section: Methodsmentioning

confidence: 99%

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Kooten

Wielandt

Schiller

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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173

124

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“…The sampled material was digested using hydrofluoric (HF)-HNO 3 acid mixtures and, after complete dissolution, a 5% aliquot of the sample was taken for Al/Mg ratio determination to 5% accuracy using a ThermoFisher X-Series II inductively coupled plasma source mass spectrometer (ICPMS) at the Centre for Star and Planet Formation in Copenhagen. The magnesium from samples with Al/Mg ratios typical of CAIs was purified by ion-exchange chromatography and its isotopic composition analyzed using a ThermoFisher Neptune multiple collector inductively coupled plasma source mass spectrometer (MC-ICPMS) at the Centre for Star and Planet Formation in Copenhagen, following protocols outlined in Bizzarro et al (33). One inclusion was typified by a resolvable deficit in 26 Mg* of ∼300 ppm as well as a stable Mg-isotope composition enriched in the heavy isotopes by ∼1%/amu.…”

Section: Methodsmentioning

confidence: 99%

¹⁸² Hf– ¹⁸² W age dating of a ²⁶ Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

Holst

Olsen

Paton

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Refractory inclusions [calcium–aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., 26 Al, 41 Ca, and 182 Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of 26 Al corresponding to 26 Al/ 27 Al of ∼5 × 10 −5 , rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and 26 Al/ 27 Al of <5 × 10 −6 , possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the 182 Hf– 182 W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with 26 Al/ 27 Al of ∼3 × 10 −6 . The decoupling between 182 Hf and 26 Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for 182 Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for 26 Al. Admixing of stellar-derived 26 Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the 26 Al– 26 Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support 182 Hf homogeneity and chronological significance of the 182 Hf– 182 W clock.

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“…The δ 25,26 Mg notation is the relative deviation, in per mil (‰), of the 25,26 Mg/ 24 Mg ratio from a reference isotopic composition (noted (δ x Mg) DSM 3 when the DSM 3 international standard is used). The reference isotopic composition used to calculate the raw Mg-isotope ratios is that of SRM 980, with 25 10 ). However, as explained in the following, because most of the data reduction is made using isotopic ratios and not delta values, and because instrumental mass fractionation is calibrated from the analyses of different standards, the final corrected delta values are independent of the values taken as the reference isotopic ratios.…”

Section: Data Reductionmentioning

confidence: 99%

“…10 However bulk analyses by HR-MC-ICPMS require a large sample size and do not allow to determine mineral isochrons because of the high spatial resolution required in the case of early solar system objects.…”

Section: Introductionmentioning

confidence: 99%

“…The magnitude of the 26 Mg excesses measured in situ by MC-SIMS (multi-collection secondary ion mass spectrometry) in ferromagnesian chondrules (chondrules are mm-sized objects which were melted and quenched in the accretion disk and they constitute the major high-temperature component of primitive meteorites) from ordinary chondrites does support a ± 10% homogeneous distribution of 26 Al and Mg isotopes at the time of CAI formation in the disk. 8 This view has been challenged 9 from very high precision bulk analyses (± 2.5 ppm for 26 Mg excesses 10 ) of refractory components of carbonaceous chondrites (CAIs and amoeboid olivine aggregates) by HR-MC-ICPMS (high-resolution multi-collector inductively coupled plasma source mass spectrometry).…”

Section: Introductionmentioning

confidence: 99%

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High precision Mg isotope measurements of meteoritic samples by secondary ion mass spectrometry

Luu

Chaussidon

Mishra

et al. 2013

J. Anal. At. Spectrom.

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The possibility of establishing an accurate relative chronology of early solar system events based on the decay of short-lived 26 Al to 26 Mg (half-life of 0.72 Myr) depends on the level of homogeneity (or heterogeneity) of 26 Al and Mg isotopes. However this level is difficult to constrain precisely because of the very high precision needed on the determination of isotopic ratios, typically of ± 5 ppm. In this study, we report for the first time a very detailed analytical protocol developed for high precision in situ Mg isotopic measurements

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High-precision Mg-isotope measurements of terrestrial and extraterrestrial material by HR-MC-ICPMS—implications for the relative and absolute Mg-isotope composition of the bulk silicate Earth

Cited by 137 publications

References 51 publications

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

¹⁸² Hf– ¹⁸² W age dating of a ²⁶ Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

High precision Mg isotope measurements of meteoritic samples by secondary ion mass spectrometry

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High-precision Mg-isotope measurements of terrestrial and extraterrestrial material by HR-MC-ICPMS—implications for the relative and absolute Mg-isotope composition of the bulk silicate Earth

Cited by 137 publications

References 51 publications

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites

182 Hf– 182 W age dating of a 26 Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

High precision Mg isotope measurements of meteoritic samples by secondary ion mass spectrometry

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¹⁸² Hf– ¹⁸² W age dating of a ²⁶ Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System