ID-TIMS zircon U–Pb geochronology of the Camel Donga eucrite

摘要: Abstract Eucrite meteorites are considered to originate from the upper crust of asteroid 4-Vesta. These differentiated basaltic commonly contain accessory zircons with grain sizes smaller than 20–30 μm in diameter. U–Pb zircon dating using secondary ion mass spectrometry (SIMS) revealed that initial magmatism and global thermal metamorphism occurred Vestan ~4550–4555 million year ago (Ma). To improve temporal resolution order distinguish grown during different events early stage crustal evolution Vesta, we have applied a chemical abrasion-based method for extracting small crystals bulk meteorite samples obtained high-precision isotope dilution-thermal ionization (ID-TIMS) dates Camel Donga eucrite. Some occur contact ilmenite, implying they formed by exsolution ilmenite followed reaction silica high temperature metamorphism. Raman measurements indicate moderately radiation damaged annealing (900 °C 48 h) is likely their crystallinities. Zircons separated acid residues after dissolving other minerals mixture hydrofluoric nitric experienced Pb fractionation treatment. High prior extraction efficiently suppresses resulting accurate precise 207Pb–206Pb dates. The weighted mean date annealed 4552.56 ± 0.69 Ma (2σ), which significantly older previously SIMS (4531 ± 10 Ma) but consistent eucrites. Thus, eucrite or formation.