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Nakamura, Y., Fujimaki, H., Nakamura, N., Tatsumoto, M., McKay, G.A. and Wagstaff, J. (1986). Hf, Zr, and REE partition coefficients between ilmenite and liquid: Implications for lunar petrogenesis. Journal of Geophysical Research 91: doi: 10.1029/JB091iB04p0D239. issn: 0148-0227. |
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Hf, Zr, and REE partition coefficients between ilmenite and coexisting liquid were determined under near-lunar conditions. Ilmenite was synthesized at 1125¿C under low oxygen fugacity (fO2=10-12.4) from glass of a high-Ti mare basalt composition, doped with 50--100 μg/g or REE and Hf, and 500--1000 μg/g of Zr. The partition coefficients (D) of ilmenite for Hf and Zr, obtained by isotope dilution analysis, are 0.41 and 0.33, respectively. These values are significantly lower than those of ilmenite (3.0 and 1.8, respectively) from a kimberlite megacryst (Fujimaki et al., 1984a). DREE for the synthesized ilmenite are slightly smaller than those of ilmenite from the kimberlite megacryst, and the DLu is 0.056. These results suggest that ilmenite may have played an important role in the Lu-Hf evolution of lunar mare basalts. Using newly determined DLu and DHf for ilmenite, the Lu-Hf evolution of Lunar cumulates and the coexisting magma was examined for several different crystallization sequences by a model calculation. The Lu-Hf variation trend of most high-Ti mare basalts is well explained by a small degree (less than 5%) of partial melting of the cumulates. However, a higher degree of partial melting is required to explain the variation of very low-Ti basalts, green glass, and Apollo 12 low-Ti basalts. Apollo 15 low-Ti basalts could not be produced by simple partial melting, but may require chromite crystallization as well. |
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American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
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