Abstract
U and Pb isotopes and rare earth elements (REEs) in individual phosphate grains from H4‐chondrites, Y‐74371 were measured by using an ion microprobe. Nine analyses of whitlockite (merrillite) and five analyses of apatites indicate a total Pb/U isochron age of 4533 ± 40 Ma (2 sigma), which are consistent with the results from previous using Thermal ionization mass spectrometer (TIMS). The observed apatites age of 4525 ± 30 Ma (2 sigma), however, is younger than those of previous works. On the other hand, the time difference between the whitlockite age of 4601 ± 94 Ma (2 sigma) and those of apatites are not observed, because of the large uncertainties. The REE abundance patterns of the whitlockites normalized to CI chondrite are characterized by an almost constant enrichment of 200–800 times CI abundance, and a striking negative Eu anomaly. The REE abundances of the apatites are lower than those of whitlockite grains, and vary appreciably among different grains. The remarkable correlation between the Eu anomaly (Eu/Eu*) and total concentration of REE is confirmed, but significant correlation with Eu anomaly and formation age of individual grains are not observed.
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