Al-26 in chondrules from CR2 chondrites

作者：Nagashima Kazuhide^*; Krot Alexander N; Huss Gary R

来源：Geochemical Journal, 2014, 48(6): 561-570.

DOI：10.2343/geochemj.2.0346

• Al-26
• chronology
• chondrules
• CR2 chondrite
• SIMS

We report Al-Mg isotope systematics in fourteen mineralogically pristine chondrules from six CR2 (Renazzo-type) carbonaceous chondrites measured with secondary ion mass spectrometry. Six chondrules show resolvable excesses of Mg-26 that correlate with Al/Mg ratios, indicating in situ decay of Al-26. The inferred initial Al-26/Al-27 ratios [(Al-26/Al-27)(0)] in these chondrules range from similar to 1 x 10(-6) to similar to 6 x 10(-6). The other eight chondrules show no detectable Mg-26 excesses and have upper limits of (Al-26/Al-27)(0) similar to(2-3) x 10(-6). Most CR chondrules have (Al-26/Al-27)(0) significantly lower than those in the other least metamorphosed primitive chondrites, LL3.0, CO3.0, and Acfer 094 (ungrouped). Assuming uniform distribution of Al-26 in the protoplanetary disk, these observations suggest that majority of CR chondrules formed %26gt;1 Myr later than those in LL3.0, CO3.0, and Acfer 094.

• 出版日期2014