Fig. 14
From: Infiltration metasomatism of the Allende coarse-grained calcium-aluminum-rich inclusions
Aluminum-magnesium isotope diagram of primary melilite in TS-34 (B1) and secondary grossular in TS-34, AJEF (B1), A-39 (B2), and TS-21 (B2). All melilite analyses show 26Mg* corresponding to the initial 26Al/27Al ratio, (26Al/27Al)0, of (5.4±0.3)×10−5, which is indistinguishable from the canonical (26Al/27Al)0 of 5.25×10−5. Grossular grains in nearly monomineralic veins crosscutting gehlenitic melilite mantle in TS-34 show resolvable 26Mg* and plot along Al-Mg isochron defined by melilite; both minerals have similar 27Al/24Mg ratios. Coarse grossular grains replacing åkermanitic melilite and associating with monticellite, ±wollastonite, ±Al-diopside, and ±forsterite show no resolvable 26Mg*; Al-Mg isochron with (26Al/27Al)0 of 1.7×10−6 is shown for reference. We infer that replacement of melilite by grossular took place after nearly complete decay of 26Al; 26Mg* in the TS-34 grossular replacing gehlenitic melilite was inherited by the melilite and provide no chronological information