Coupled Ce-Nd isotope systematics and rare earth elements differentiation of the moon |
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| Authors: | Masaharu Tanimizu Tsuyoshi Tanaka |
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| Institution: | 1 Department of Earth and Planetary Sciences, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan |
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| Abstract: | 138Ce/142Ce and 143Nd/144Nd isotope ratios of lunar samples are determined to constrain the petrogenetic differentiation and evolution of the moon. High-precision Ce-Nd isotope data, well-defined Rb-Sr isochrons, and rare earth elements (REE) abundances of lunar samples show that unexpectedly low La/Ce ratios of evolved lunar highland samples are preserved from at least 3.9 Ga. Precise analysis of REE abundances indicates that the low La/Ce ratio results from a depletion of La relative to other REE. This depletion can be seen in pristine KREEP basalts and Mg-suite rocks from 3.85 to 4.46 Ga. As REE abundances of all these samples are controlled by the presence of a KREEP component, the depletion was probably inherited from a late crystallization sequence of the lunar magma ocean related to the production of the original KREEP component. |
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