Al-Mg and U-Pb chronological records of Erg Chech 002 ungrouped achondrite meteorite

Achondrite meteorites are remnants of the earliest planetary differentiation processes in Solar System. They have been used to anchor short-lived radiochronometers absolute ages determined from long-lived radiochronometers. More specifically, when comparing isotopic systematics 26Al-26Mg chronometer anchored U-corrected Pb-Pb ages, inferences about distribution 26Al (half-life ∼717 000 yr) protoplanetary disk can be evaluated. The ungrouped achondrite Erg Chech (EC) 002 has a distinct mineralogy and more evolved elemental composition compared basaltic achondrites. In situ solution chronometry 53Mn-53Cr suggest that EC formed within ∼0.7 2.2 Ma after formation Ca-Al-rich inclusions (CAIs), making it oldest known sample igneous crust System (Barrat et al., 2021, Anand 2022, Zhu Fang 2022). Here we present age obtained by MC-ICPMS analysis same mineral separate samples 002. addition, six merrillite grains were analyzed in-situ SIMS determine their individual ages. U isotope exhibits internal heterogeneities between leached pyroxene (238U/235U = 137.766 ± 0.027) bulk rock 137.8190 0.0074). Pb progressively pyroxenes characterized radiogenic 206Pb/204Pb ratios (ranging 41 23487). Using pyroxenes, resulting 207Pb/206Pb-204Pb/206Pb isochron is 4565.87 0.30 (2σ). weighted mean seven analyses merrillites 4564.3 5.2 These similar (within uncertainty) indicate rapid cooling absence significant thermal events ∼4559 on parent body through rock, pyroxene, fine-grained four plagioclase fractions defines an initial 26Al/27Al ratio [8.89 0.79] × 10−6 corresponding 1.83 0.12 CAIs ([5.23 0.13] 10−5; Jacobsen 2008). abundance consistent with previous MC-ICP-MS reported for (Fang 2022), but 0.46 0.13 Myr older than previously Barrat al. (2021).When CV3 (4567.30 0.16 Ma; Connelly 2012), Al-Mg model 4565.47 0.20 Ma, slightly younger its age. concordance CC achondrites was homogeneously distributed NC reservoirs at time accretion. Furthermore, presence found whole-rock supports need meteoritic dated using chronometer.