Survival of presolar p -nuclide carriers in the nebula revealed by stepwise leaching of Allende refractory inclusions

Abstract

The 87Rb-87Sr radiochronometer provides key insights into the timing of volatile element depletion in planetary bodies, yet the unknown nucleosynthetic origin of Sr anomalies in Ca-Al–rich inclusions (CAIs, the oldest dated solar system solids) challenges the reliability of resulting chronological interpretations. To identify the nature of these Sr anomalies, we performed step-leaching experiments on nine unmelted CAIs from Allende. In six CAIs, the chemically resistant residues (0.06 to 9.7% total CAI Sr) show extreme positive μ84Sr (up to +80,655) and 87Sr variations that cannot be explained by decay of 87Rb. The extreme 84Sr but more subdued 87Sr anomalies are best explained by the presence of a presolar carrier enriched in the p-nuclide 84Sr. We argue that this unidentified carrier controls the isotopic anomalies in bulk CAIs and outer solar system materials, which reinstates the chronological significance of differences in initial 87Sr/86Sr between CAIs and volatile-depleted inner solar system materials.

A new gain calibration protocol for Faraday amplifiers equipped with a 1013 Ω resistor

“…Depending on the version, the amplifiers show different responses to any instrumental trouble in the constant current generator. This idea does not contradict with previous studies 17–19 that reported no systematic error in the isotopic data obtained by TIMS using the 3.3 pA constant current calibration.…”

“…A new calibration technique for the 10 13 U Faraday amplier was recently reported to achieve better precision in gain measurement. [16][17][18][19] This technique employs a fully sowarecontrolled procedure that entails the use of a 3.3 pA constant current generator, while the automation of the calibration protocol tends to obscure technical or instrumental problems. In practice, our preliminary isotopic data yielded a systematic error of >0.1&, suggesting a need for the validation of the calibration protocol prior to an isotopic analysis.…”

In situ 87Rb–87Sr analyses of terrestrial and extraterrestrial samples by LA-MC-ICP-MS/MS with double Wien filter and collision cell technologies

“…Overall, this study shows that while the precision of LA-MC-ICP-MS/MS is not as good as TIMS, which has a better useful yield than LA-MC-ICP-MS/MS for Sr (1.5% (ref. 97) vs. 0.25%), the precision is still sufficient to detect magma mixing and assimilation based on in situ 87 Sr/ 86 Sr isotopic analyses.…”

“…Our motivation for measuring the Sr isotopic compositions of hibonite inclusions was to search for possible isotopic anomalies 108 and compare the 87 Sr/ 86 Sr ratios with the known solar system initial ratio (0.69876 AE 0.00002; 109 0.69883 AE 0.00002; 110 0.698784 AE 0.000076 (ref. 97)). Given the small size and refractory nature of hibonite inclusions, we changed the laser beam spot to 35 mm and the repetition rate to 12 Hz.…”

Distribution of s-, r-, and p-process Nuclides in the Early Solar System Inferred from Sr Isotope Anomalies in Meteorites

“…To quantitatively assess the expected μ 84 Sr variations, we will start with the variations expected from the heterogeneous distribution of nuclides produced in neutron-rich stellar environments. For Sr this includes r-and p-process variations, which result in the same 84 Sr signatures; for instance, the 84 Sr excesses in CAIs have been interpreted to reflect either an r-process (Hans et al 2013) or p-process excess (Charlier et al 2021). For the model of this study, the distinction between r-and p-process variations is not important, which we will therefore treat together.…”