An effect of variations in relative sensitivity factors on Al-Mg systematics of Ca-Al-rich inclusions in meteorites with secondary ion mass spectrometry

Abstract

significant variations in (Al/Al)0, implying that thermal processes of condensation and melting for CAI formation occurred contemporaneously and continued for ~0.4 Myr at the very beginning of Solar System formation, under the assumption of homogeneous distributions of 26Al in the forming region (Kawasaki et al., 2020). Among the data available, an example of the smallest analytical errors in (Al/Al)0 for CAIs has been obtained from a fluffy Type A CAI from Vigarano, with (Al/Al)0 = (4.703 ± 0.082) × 10 –5 (Kawasaki et al., 2019); the relative error is 1.7%. (Al/Al)0 for CAIs is determined from the slope of the regression line for CAI mineral data on the Al-Mg evolution diagram (27Al/24Mg vs. radiogenic excess of 26Mg, 26Mg*) for each CAI. 26Mg* values for CAI minerals are accurately determined with SIMS by correcting both natural mass-dependent fractionation and instrumental mass fractionation (IMF) of SIMS for Mg-isotopes (Itoh et al., 2008; Kita et al., 2012; Kawasaki et al., 2017). On the other hand, relative An effect of variations in relative sensitivity factors on Al-Mg systematics of Ca-Al-rich inclusions in meteorites with secondary ion mass spectrometry