Abundance of alkali metals, alkaline and rare earths, and strontium-87/ strontium-86 ratios in lunar samples.
The variation in trace element abundance patterns indicates that lunar igneous rocks are the product of extensive igneous fractionation. Variations in the Sr(87)/ Sr(86) ratio indicate that these rocks crystallized 3.5+/-0.3 x 10(9) years ago.
Gast
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Hubbard
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