The composition and origin of the moon

Anderson, Don L.

doi:10.1016/0012-821x(73)90069-1

Cited by 47 publications

(20 citation statements)

References 40 publications

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“…A similar suggestion was made by Wood et al (1970). The trace element abundances in the lunar crust [Anderson, 1973a] are consistent with the fractional crystallization calculations of Gast et al [ 1970], although they did not consider melilite as a possible residual phase.Acknowledgments. This note is a combination and condensation of replies written in response to extensive comments by A. E. Ringwood on 'Removal of a constraint on the composition of the lunar interior.'…”

supporting

confidence: 86%

“…Rapid accretion combined with the initially high temperatures of the condensation model suggests that the moon was extensively molten early in its history . I proposed earlier [Anderson, 1973a] that the present internal structure resulted from fractional crystallization involving most if not all of the moon. A similar suggestion was made by Wood et al (1970).…”

Section: Andersonmentioning

confidence: 88%

“…The density of this region in the Ringwood model would. be 3.27 g/cm 3 , much higher than that of Wood's (1973] model.A thick plagioclase rich crust and a Ca-Al rich interior are consistent with the lunar density and C/MR 2• lfwe adopt 2.9 g/cm 3 for the mean density of the crustal layers, 3.6 g/cm 3 for the 40-km thick subcrustal layer [Toksoz et al, 1973;Anderson and Kovach, 1972], and 3.0 g/cm 3 for the remainder of the moon above 250 km, then the density of the lower mantle required to satisfy the lunar density is 3.5 g/cm 3 • This can be compared with the 3.4-g/cm 3 density predicted by Anderson [1973a] on the basis of the refractory model, assuming complete separation of the residual crystals (spinet, merwinite, diopside) from the low-melting fraction of the early condensate. The presence of Ca rich garnet, perovskite, or corundum in the lower lunar mantle would serve to increase the density.…”

mentioning

confidence: 87%

“…However, the surface evidence suggests that the moon is also deficient in elements and compounds more volatile than iron. This led to the suggestion [Anderson, 1972[Anderson, , 1973a that the interior of the moon was enriched in CaO and Al 2 0 3 • This is in direct conflict with the conclusion of Ringwood and Essene (1970) and Ringwood [1970). In the model of Anderson [1972Anderson [ , 1973a the moon is refractory rich and is composed predominantly of material less volatile than iron.…”

mentioning

confidence: 99%

“…The early condensates and the Allende inclusions both have the desired properties. The preiron condensates constitute 6% of the mass of material of solar or chondritic composition and will be enriched by a factor of about 17 in the refractory trace elements; the Ca0-Al 2 0 3 rich Allende inclusions are enriched by about a factor of 16 [Anderson, 1973a]. Table I gives the abundances of several refractory elements in the moon and for comparison, abundances in the Ca0-Al 2 0 3 rich inclusions in the Allende meteorite and chondritic abundances.…”

mentioning

confidence: 99%

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On the composition of the lunar interior

Anderson

1975

J. Geophys. Res.

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There is now abundant geophysical and geochemical evidence suggesting that the moon has a thick plagioclase rich outer shell. This is most easily explained by early and extensive melting of a CaO and Al,0 8 rich moon followed by fractional crystallization involving p1agioclase notation. Melilite is probably an important constituent of the interior. This model explains the seismic velocities, the mean density, and the moment of inertia of the moon. The moon is 73-88% high-temperature condensa~e.In a previous paper [Anderson, I 913b] I concluded that the gross physical properties of the moon such as its mass and moment of inertia did not place significant constraints on the major element abundances of the deep lunar interior except that the moon was clearly deficient in iron in relation to cosmic, chondritic, or terrestrial abundances. In particular, this kind of data cannot be used to place upper bounds on the CaO and Al 2 0 3 content. However, the surface evidence suggests that the moon is also deficient in elements and compounds more volatile than iron. This led to the suggestion [Anderson, 1972[Anderson, , 1973a that the interior of the moon was enriched in CaO and Al 2 0 3 • This is in direct conflict with the conclusion of (1970) andRingwood [1970). In the model of Anderson [1972, 1973a] the moon is refractory rich and is composed predominantly of material less volatile than iron. Such a moon would be enriched in the refractory trace elements by about a factor of 16 relative to chondritic abundances and upon melting or fractional crystallization would yield a plagioclase-pyroxene outer shell of the order of 250-km thickness. A mixture of about 14% basalt and 86% anorthosite satisfies the bulk chemistry of this layer and eliminates the Eu 1 anomaly. Melilite, an important component of the interior in this model, can also retain Eu relative to the other REE (rare earth elements). This would reduce the required thickness of a plagioclase rich outer shell. However, these proportions are broadly consistent with the areal extent of the maria and the volumetric relationships implied by elevation differences, offset of center of mass, and the moments of inertia [Wood et al., 1970;Wood, 1973). The Allende inclusions have many of the properties inferred for the moon, such as depletion of volatiles and appropriate levels of the incompatible trace elements, The inclusions show that compounds in the nebula can be separated on the basis of their volatility. Ringwood and EsseneIn most discussions of the composition of the deep lunar interior the assumption is made that the lqnar mantle is predominantly olivine and pyroxene. There is a strong terrestrial and meteoritic bias behind these assumptions. The fact that the moon is clearly depleted in iron compared with the terrestrial planets and cosmic abundances suggests that the moon may be unique in other respects. Trace element studies support this suggestion and imply that the source region of lunar igneous rocks is enriched in refractories. Ringwood [1970, p. 6467) sugg...

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supporting

confidence: 86%

Section: Andersonmentioning

confidence: 88%

mentioning

confidence: 87%