ta2.14 – Europlanet

22-EPN3-036: Investigating Titanium and Chromium Isotopes in Unusual Achondrite NWA 8564

October 3, 2024

22-EPN3-036: Investigating Titanium and Chromium Isotopes in Unusual Achondrite NWA 8564

Visit by Julia Cartwright of University of Alabama (USA) to TA2.14 ETH Zurich Geo- and Cosmochemistry Isotope Facility (Switzerland).
Dates of visit: 10-22 July 2023

Report Summary: We pursued high-precision chromium (Cr) and titanium (Ti) isotopic analysis to better refine the parent body of little-studied unusual achondrite Northwest Africa (NWA) 8564. While originally classified as a cumulate eucrite, NWA 8564 displayed unusual lead (Pb) data, suggestive of contributions from an exotic component, thus calling into question its assumed parent body, asteroid 4-Vesta. In this work, we sampled, prepared, and dissolved materials from NWA 8564, eucrites Juvinas and Tirhert, alongside diogenite NWA 7831 and a terrestrial standard to determine the parentage of NWA 8564.

Samples were selected, sampled and sent to ETHZ to be crushed and taken through dissolution and column chemistry. As Cr and Ti isotope analysis require different schedules, the chemistry and analysis stages were staggered for efficiency (e.g., three Ti columns and the first stages of Cr column cleaning were performed prior to Ti arrival). During the visit, the Cr separation procedure was carried out and preliminary analyses were performed after the visit. Eluted Ti aliquots were assessed for content and subsequently diluted for MC-ICP-MS analysis in week 1. Following data assessment/reduction, further aliquots were prepared through week 2, resulting in ~4 sessions of Ti data. The preliminary results show Ti and Cr isotope values for NWA 8564 within the range of eucrites. This suggests that NWA 8564 originates from Vesta, and must have experienced a significant event on Vesta that affected the Pb isotope data. This may include remelting associated with a large impact, potentially linked to the large, ancient basins at Vesta’s south pole.

Back to TA visit reports page.

Back to TA main page.

Back to Europlanet 2024 RI homepage.

22-EPN3-048: Evaluation of the initial 92Nb abundance in the inner Solar System

September 29, 2024

22-EPN3-048: Evaluation of the initial 92Nb abundance in the inner Solar System

Visit by Makiko Haba, Tokyo Institute of Technology (Japan) to TA2.14 ETH Zurich Geo- and Cosmochemistry Isotope Facility (Switzerland).
Dates of visit: 02-15 August 2023

Report Summary: Evaluation of the heterogeneous distribution of short-lived 92Nb in the protoplanetary disk is mandatory to utilize the ⁹² Nb-⁹²Zr chronometer for dating planetary materials. A higher initial ⁹²Nb/⁹³Nb ratio has been reported for one meteorite that originate from the outer Solar System compared to meteorites from asteroid Vesta, which formed in the inner Solar System. The initial ⁹²Nb/⁹³Nb ratios determined at high precision from various types of meteorites are needed to comprehend the initial distribution of ⁹²Nb in the early Solar System. To evaluate the initial ⁹²Nb/⁹³Nb ratio in the inner Solar System, we conducted Zr isotopic measurements of rutiles separated from the Miles iron meteorite (IIE), whose parent body is considered to have formed inside Vesta in the protoplanetary disk.

During the Europlanet TA visit, the Zr isotopic compositions of five rutile fractions were analysed using a Neptune Plus MC-ICPMS. These rutile fractions with large variations in Nb/Zr ratios yielded ε⁹² Zr values from 0.19 ± 0.28 to 5.27 ± 0.21. The Nb-Zr data form a single, well defined isochron yielding a ⁹²Nb/⁹³Nb Nb ratio of (1.10 ± 0.07) × 10^-5 at the time of rutile formation. Using the absolute age of the Miles iron meteorite (4542.3 ± 4.0 Ma, Kirby et al., 2022) yields an ⁹²Nb/⁹³Nb ratio of (1.76 ± 0.12) × 10^-5 at CAI formation. This is consistent with the initial ⁹²Nb/⁹³Nb ratio in Vesta formation region ((1.66 ± 0.10) × 10^-5), suggesting that the initial ⁹²Nb/⁹³Nb ratio was homogeneous in the inner Solar System.

Back to TA visit reports page.

Back to TA main page.

Back to Europlanet 2024 RI homepage.

20-EPN2-074: Titanium and chromium isotopes in individual chondrules and anomalous clasts in chondrite meteorites

October 7, 2022

20-EPN2-074: Titanium and chromium isotopes in individual chondrules and anomalous clasts in chondrite meteorites

Visit by Philip Reger, University of Western Ontario (Canada) to TA2.14 ETH Zurich Geo- and Cosmochemistry Isotope Facility (Switzerland).
Dates of visit: 5-22 July 2021

Report Summary: Chondrules, which are sub-millimetre igneous spherules and the main component of chondrites, formed during the first 5 Myr of the Solar System. Both ²⁶Al-²⁶Mg and ²⁰⁷Pb-²⁰⁶Pb ages of individual chondrules have also shown a ~2 Myr age difference between them in single meteorites. To advance our understanding of chondrule formation and the evolution of the protoplanetary disk within its first 5 Myr of existence, we proposed to obtain the mass-independent isotopic compositions of Cr and Ti for 6 selected chondrules and anomalous clasts from H and L ordinary chondrites. During the Europlanet TA visit, the Cr isotope compositions were analyzed by MC-ICP-MS after undergoing Cr and Ti separation by ion-exchange chromatography (awaiting mass spectrometry measurements for Ti). The Cr isotopic analyses are the most precise results from individual chondrules to date and show variability of the Cr isotope composition in individual chondrules, even within the same meteorite. A comparison of ^ε54Cr with chronological data previously obtained on the same chondrules suggests that the Cr isotope composition of the inner Solar System (NC reservoir) underwent a gradual change during at least the first 2 Myr of the Solar System. This change could potentially reflect thermal processing, a change of infalling molecular cloud material, or the decreasing incorporation of refractory minerals without ⁵⁴Cr excesses into chondrule precursors.

Back to TA visit reports page.

Back to TA main page.

Back to Europlanet 2024 RI homepage.