^(238)U/^(235)U Ratios of Anagrams: Angrites and Granites

Abstract

Significant ^(238)U/^(235)U variations have been documented in meteoritic [e.g. 1-4] and terrestrial [5] samples, which can affect Pb-Pb ages. In most cases, the cause of these variations is not understood. Here, we report an extensive study of the U isotopic composition of planetary crustal rocks. Determination of ^(238)U/^(235)U ratio in angrites is critical to establish their age: an important anchor in early solar system chronology [6,7]. The extent to which the protolith of terrestrial granites affects their U isotopic composition is unknown. We report high-precision U isotope measurements of angrites and terrestrial granites to address these two outstanding questions in solar system chronology and crustal differentiation.