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Hubbard, N. J.

Publications and source records attributed to Hubbard, N. J..

35 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

How to lose Rb, K, and change the K/Rb ratio - An experimental study

Thermal volatilization studies on Apollo 16 soils and crystalline rocks have been carried out to measure the depletion of K, Rb, and Na and changes in K/Rb ratios during heating under vacuum. Rubidium can be lost from both soils and rocks at temperatures as low as 1000 C. Because of the greater volatility of Rb as compared to K, the K/Rb ratio can be changed from normal values of 330-360 for the Apollo 16 samples to values as high as 1100 by thermal volatilization. Rapid heating experiments on soil samples were carried out to approximate agglutinate formation conditions in order to measure changes in alkali element abundances. Equal changes in K/Rb ratios can be produced with longer heating at lower temperatures or heating at higher temperatures for shorter times.

Gibson, E. K., Jr.↗
NASA NTRS1973

Lunar rock types - The role of plagioclase in non-mare and highland rock types

Some nonmare and highland rock types (14310 type KREEP and very high Al2O3 basalts) have the internal chemical variations expected for a plagioclase-liquid system. The observed Eu variations in these rock types suggest a D(Eu) 1/p of 0.6 to 0.7. The Sr variations suggest a D(Sr) 1/p of about 0.6, with values as low as 0.35 suggested for some materials from sample 14063. Common Apollo 14 KREEP and Apollo 15 KREEP do not show internal Sr, Eu, Al2O3 variations consistent with the D(Eu, Sr) 1/p values derived for 14310 type KREEP. Major element and experimental data indicate that olivine or pyroxene is a large, perhaps dominant, controller of chemical variations within common Apollo 14 KREEP. The application of these distribution coefficients to pure anorthosites like 15415 yields the model dependent conclusion that the silicate liquids with which such anorthosites may have been chemically equilibrated have not yet been analyzed and perhaps not directly sampled.

Hubbard, N. J.↗
NASA NTRS1973

Rb-Sr systematics for chemically defined Apollo 15 and 16 materials

Concentrations of Rb and Sr and the Sr87/86 ratios are determined in a large number of Apollo 15 samples, including KREEP basalts, mare basalts, anorthosite breccia clasts, lithic fragments, a spinel-bearing clast, green glass samples, breccia matrix, and soils. Relative concentrations of Sm, Eu, Rb, and Sr are also examined in the samples, with particular attention to Rb/Sr systematics vs other trace element abundances and total chemical compositions of rocks. Analysis of crystalline KREEP samples rich in trace elements indicates that the differentiation of these rocks has extended to -4.25 AE age, a significantly later time than the presumed time of accretion of the moon.

Nyquist, L. E.↗
NASA NTRS1972

The chemical composition of soil from the Apollo 16 and Luna 20 sites.

The concentrations of the rare earth elements K, Rb, Sr, Ba, U, Zr, and Cr for the Luna 20 soil and four different Apollo 16 soils are reported. These trace element abundances imply: (1) that the lunar highlands consist of a mixture of rocks rich in large ion lithophile (LIL) elements and LIL-element improverished anorthosites; or (2) that the bulk of the aluminum-rich crust did not originate by upward segregation of plagioclase in a primitive liquid shell. The Luna 20 soil is distinguished from the Apollo 16 soil by lower aluminum and LIL element abundances.

Bansal, B. M.↗
NASA NTRS1972

Chemical features of the Luna 16 regolith sample.

The Luna 16 regolith sample differs from Apollo 11, 12 and 14 regolith and basalt samples by having smaller negative Eu and Sr anomalies and nearly chondritic Eu/Sm and Eu/Sr ratios although the overall REE, Ba, Sr and U concentrations are 25 to 45 times chondrites. Major element data, in particular FeO vs Al2O3, show that the Luna 16 regolith sample is composed of materials that follow a quantitatively different Fe/Al variation than do Apollo 11, 12, 14 and 15 samples. The small Eu and Sr anomalies and the displaced Fe/Al variation are two chemical features unique to the Luna 16 regolith sample. The Luna 16 regolith sample can contain little if any of the rock types abundant at Apollo sites, thus indicating that the unique chemical features are typical of local or nearby materials and indicate a separate petrogenetic province for major component rock types of the Luna 16 regolith.

Hubbard, N. J.↗
NASA NTRS1972

Nonmare basalts. II.

Chemical characteristics of KREEP basalts from the Apollo 12 site are discussed. It is indicated that nonmare basalts are chemically distinct from mare basalts, primarily in FeO and Al2O3 concentrations and their ratios, and that the spectra of the former are closely related to the degree of partial melting. It is also noted that the chemical compositions of KREEP basalts from Apollo 12, 13, and 14 show very little chemical variation.

Hubbard, N. J.↗
NASA NTRS1972

Rb-Sr systematics for chemically defined Apollo 14 breccias.

The Rb and Sr systematics were determined for eight lithic fragments from the coarse fines of Apollo 11, Apollo 12, and Apollo 14; for bulk soils from Luna 16, Apollo 14, and Apollo 15 and for 'whole rocks' from Apollo 14 and the Apollo 15 anorthosite 15415. The objective of the studies was to identify important lunar rock types by their major and trace element chemistry and utilize Rb and Sr systematics to obtain a chronology for events which establish or modify rock chemical composition.

Nyquist, L. E.↗
NASA NTRS1972

Thermal volatilization studies on lunar samples.

The results of thermal volatilization studies on lunar basalts, breccias, and soils, carried out to measure the depletion of selected elemental abundances during heating under vacuum, are evaluated. The kinetics of K, Rb, and Pb loss are found to be sufficiently fast to permit vaporization and loss of these elements during the production of impact glasses. There is little probability that lunar basalt flows have lost a significant percentage of K, Rb, and Na by volatilization, unless the flow is extensively stirred. The uniformly low Na concentrations of mare basalts cannot be attributed to post eruption vaporization and loss on Na.

Gibson, E. K., Jr.↗
NASA NTRS1971

Chemical composition of lunar anorthosites and their parent liquids.

Data obtained in a trace element analysis of some anorthosite and anorthositic fragments are presented. The low Mg concentrations of the Apollo 15 anorthosite and the KREEP anorthosite reflect the mineralogical purity of these samples. They are so pure that their composition can be taken as that of liquidus plagioclases. Some of the characteristics of the parent liquids of these plagioclases can be calculated from the liquid-plagioclase distribution coefficients.

Hubbard, N. J.↗