Strontium isotopic anomalies in the Allende Meteorite

Abstract

We report Sr isotope anomalies in two Ca-Al-rich inclusions (EK1-4-1 and Cl) of the Allende meteorite which also contain anomalies in O, Mg, Ca, Ba, Nd and Sm. The Sr effects correspond to ^(84)Sr or ^(88)Sr deficits of 3.2‰ and 0.8‰ or to ^(86)Sr excesses of 1.6‰ and 0.4‰. Although it cannot be ascertained in which isotope the anomalies reside, arguments based on the ^(87)Sr abundance indicate that the anomalies may reside in ^(84)Sr and ^(86)Sr. The data indicate deficits in the p-process component (^(84)Sr) up to 3.2‰ or in the r-process component in Sr (^(88)Sr) of up to 32‰ and are not easily reconcilable with effects in Ba and Nd, which indicate excess r, and in Sm, which indicate excess r and p components. The existence of positive and negative anomalies for many elements requires an isotopically heterogeneous solar system at the time of formation of these inclusions. The use of ^(87)Sr/^(86)Sr as a chronometer in the early solar system requires reevaluation, although the anomalies found in Sr thus far do not show the presence of any obvious artifacts in ^(87)Sr/^(86)Sr.

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