Lu‐Hf and Sm‐Nd evolution in lunar mare basalts
Lu‐Hf and Sm‐Nd evolution in lunar mare basalts
复制标题
月海玄武岩中的 Lu-Hf 和 Sm-Nd 演化
DOI：
--
复制
发表时间：
1984
期刊：
影响因子：
--
通讯作者：
M. Tatsumoto
中科院分区：
文献类型：
--
作者：
D. Unruh;P. Stille;P. Patchett;M. Tatsumoto
月海玄武岩的Lu-Hf和Sm-Nd数据，结合Rb-Sr和总REE数据，表明月海玄武岩是由堆积物源区的小程度（≤ 10%）部分熔融形成的，但形成这些源区的岩浆海洋是轻稀土和富Hf的。计算出的物源成分范围从二辉橄榄岩到橄榄二辉橄榄岩。源中少量钛铁矿（≤ 3%）的非模态熔融似乎是Lu/Hf数据所要求的。通过对月海玄武岩和陆洋玄武岩的Hf、Nd同位素特征的比较，发现低Ti月海玄武岩的ε Hf/ε Nd比值远高于陆洋玄武岩。这一结果与陆源玄武岩源为部分熔融残留物而月海玄武岩源为堆积物的假设在定性上是一致的。或者，结果可能意味着，陆地地幔的演化在两个（或更多）阶段的演变，和净效应是地幔的耗尽在第一个约1 -3亿年。在最后1-2亿年期间，或者简单地说，月球和地球地幔之间的Lu-Hf晶体-液体分配（相对于Sm-Nd）存在差异。
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 (< or =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 fromm lherzolite to olivine websterite. Nonmodal melting of small amounts of ilmenite (< or =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 epsilonHf/epsilonNd ratios of 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 approx.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.