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Lu-Hf and Sm-Nd evolution in lunar mare basalts

January 1, 1984

Lu-Hf and Sm-Nd data for mare basalts combined with Rb-Sr and total REE data taken from the literature suggest that the mare basalts were derived by small (≤10%) degrees of partial melting of cumulate sources, but that the magma ocean from which these sources formed was light REE and Hf-enriched. Calculated source compositions range from lherzolite to olivine websterite. Nonmodal melting of small amounts of ilmenite (≤3%) in the sources seems to be required by the Lu/Hf data. A comparison of the Hf and Nd isotopic characteristics between the mare basalts and terrestrial oceanic basalts reveals that the εHf/εNd ratios in low-Ti mare basalts are much higher than in terrestrial oceanic basalts. The results are qualitatively consistent with the hypothesis that terrestrial basalt sources are partial melt residues whereas mare basalt sources are cumulates. Alternatively, the results may imply that the terrestrial mantle has evolved in two (or more) stages of evolution, and that the net effect was depletion of the mantle during the first ∼1–3 b.y. followed by enrichment during the last 1–2 b.y.; or simply that there is a difference in Lu-Hf crystal-liquid partitioning (relative to Sm-Nd between the lunar and terrestrial mantles.

Publication Year 1984
Title Lu-Hf and Sm-Nd evolution in lunar mare basalts
DOI 10.1029/JB089iS02p0B459
Authors D.M. Unruh, P. Stille, P. J. Patchett, M. Tatsumoto
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research Solid Earth
Index ID 70013141
Record Source USGS Publications Warehouse