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A Petrologic Model for the Moon Based on Petrogenesis, Experimental Petrology, and Physical Properties

Smith, J. V. and Anderson, A. T. and Newton, R. C. and Olsen, E. J. and Wyllie, P. J. (1970) A Petrologic Model for the Moon Based on Petrogenesis, Experimental Petrology, and Physical Properties. Journal of Geology, 78 (4). pp. 381-405. ISSN 0022-1376.

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Crystallization experiments under highly reducing conditions of synthetic material of mean Apollo 11 rock composition yielded: ilmenite in at 1,150° C; clinopyroxene in at 1,130° C, plagioclase in at 1,120° C. The same sequence of crystallization for the A pollo 11 vesicular ferrobasalts was interpreted from the mineral textures. The low liquidus temperature, narrow crystal-liquid interval, and delayed appearance of plagioclase are interpreted by crystallization from a magma formed by remelting of a mixture of accumulated pyroxene and ilmenite crystals in a liquid which has undergone advanced fractional crystallization. Under the Sea of Tranquillity, a residual ferrobasaltic liquid was formed by fractional crystallization of ultrabasic magma deeper in the moon. Heavy ilmenite and pyroxene crystals sank in the liquid, while light plagioclase floated to augment a crust. Meteorite impact blasted away the plagioclase-rich crust and released a ferro-basaltic magma formed by melting of ilmenite and pyroxene into the differentiated liquid. Fractional crystallization of a molten moon of modified chondritic composition yielded a small metallic core surrounded by pressure-stable, Mg-rich olivine and pyroxene. The fractionated liquid became Fe-and Ti-rich. Primitive ultrabasic crust in the highlands was augmented by dominant plagioclase-rich cumulates. The preferential occurrence of large irregular seas on the earth side of the moon is explained by differential tidal attraction of the late liquid fraction, and release by meteorite impact. The model can satisfy the density and moment of inertia of the moon if the olivine is Mg-rich. Early removal of radioactive material from the center by fractional crystallization, and enhancement of radiative heat transfer in volatile-free silicates would ease the problem of cooling the center of the moon. The low volatile content of A pollo 11 rocks may be a feature of the entire moon, permitting high rigidity and refractoriness. Incorporation of metal-seeking elements into a metal core, loss of volatiles from a hot surface, and crystal-liquid fractionation can explain some element concentrations of A pollo 11 rocks. Nevertheless the low density of the moon indicates a low Fe content of the primary material of the moon. Although there are no'meteorites which match the Apollo 11 rocks in all chemical and textural respects, several types have one or more features in common.

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Additional Information:© 1970 University of Chicago Press. Manuscript received February 25, 1970. We thank G.R. Zechman and O. Draughn for electron microprobe supervision and specimen preparation, Mrs. J.V. Smith for bibliographic and editorial work, and Mrs. I. Baltuska for secretarial help. Financial assistance from NASA grant NAS9-8086 was supplemented by NSF grants G-1658, GA-4420, GA-15718, and GA-1656, an Advanced Research Project Agency grant, a grant-in-aid from Union Carbide Corporation, a Hertz Foundation fellowship, and general funds of the University of Chicago. We particularly thank D. Anderson and J. Warner of NASA, and the LSPET and LSAPT teams for their hard work in preparing and distributing samples. We thank E. Anders for help with bibliography and for various valuable discussion.s
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Advanced Research Projects Agency (ARPA)UNSPECIFIED
Union Carbide CorporationUNSPECIFIED
Fannie and John Hertz FoundationUNSPECIFIED
University of ChicagoUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20160202-111703486
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Official Citation:Smith, J. V. et al.. “A Petrologic Model for the Moon Based on Petrogenesis, Experimental Petrology, and Physical Properties”. The Journal of Geology 78.4 (1970): 381–405
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64168
Deposited By: Tony Diaz
Deposited On:03 Feb 2016 23:27
Last Modified:03 Oct 2019 09:35

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