The lunar regolith: Chemistry and petrology of Luna 24 grain size fractions

doi:10.1016/0016-7037(87)90077-9

Geochimica et Cosmochimica Acta

Volume 51, Issue 3, March 1987, Pages 661-673

https://doi.org/10.1016/0016-7037(87)90077-9 Get rights and content

Abstract

Chemical data are reported for the first time for lunar soil size fractions smaller then 2 μm. We report chemical data for 30 elements by INAA in eight size fractions (370−200, 200−94, 94−74, 74−40, 40−10, 10−5, 5−2 and <2 μm) and petrology of five size fractions (down to 40−10 μm) in two Luna 24 soils, 24176 and 24214. Consistent with our previous results for lunar soils, the compositions of coarser fractions (>10 μm) are quite similar to each other but quite different from the fine fractions (<10 μm). The finer fractions (10–5, 5–2, <2 μm) become increasingly feldspathic and enriched in large-ion lithophile elements (LILE) with decreasing grain size. Chemical data for the finer fractions provide direct evidence in favor of efficient comminution of rock mesostasis and feldspar leading to their preferential incorporation into the finer fractions. High concentrations of meteoritic indicator elements (Ni, Au, Ir) in the finer fractions are consistent with the comminution process by micrometeorite impacts. The chemical data strongly support the F³ (fusion of the finest fraction) model for agglutinate formation.

Based on grain size distribution, petrology, and LILE patterns of size fractions, the Luna 24 soils are less reworked than most lunar soils. The Luna 24 regolith appears to have formed as a result of mixing more mature and fine grained material with less mature coarse material in different proportions at different depth intervals.

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Cited by (13)

Polarimetry of moonlight: A new method for determining the refractive index of the lunar regolith
2016, Icarus
Citation Excerpt :
Studies of lunar soil have shown that the composition of the regolith changes with grain size. An important finding is that, when compared to coarser grains, the smallest fraction of grains within mare soils are consistently richer in plagioclase, and are depleted in elements (e.g. Fe, Mg) associated with ferromagnesian minerals (Evenson et al., 1974; Korotev, 1976; Laul et al., 1987; Papike et al., 1981; Taylor et al., 2003). A hypothesis that may account for this is that a greater proportion of plagioclase from disaggregated mare basalt is concentrated in the finer grain size fraction (Korotev, 1976; Papike et al., 1982; Laul et al., 1987).
We present a new method for remotely measuring the refractive index of the lunar regolith, using polarised moonlight. Umov’s Law correlates the polarisation (P_max) of scattered moonlight and the albedo (A) of the scattering lunar regolith. We discuss how deviations from this correlation have previously been linked to the so-called ‘Polarimetric Anomaly Parameter’, (P_max)^aA, which was proposed by Shkuratov and others as being related to variations in regolith grain size. We propose a reinterpretation of that parameter. We develop models of light scattering by regolith grains which predict that variation in the refractive index of regolith grains causes deviations from Umov’s Law. Variations in other grain parameters such as grain size and degree of space weathering do not produce this deviation. The models are supported by polarimetric measurements on powdered terrestrial materials of differing refractive index. We derive a simple formula to express the relationship between refractive index and the deviation from Umov’s Law and apply it to telescopic measurements of regions of the lunar surface. We show that the Aristarchus Plateau and the Marius Hills regions both comprise materials of unusually low refractive index. These results are consistent with recent estimates of the mineralogy of those areas. Picard and Peirce craters, in Mare Crisium, are shown to contain material of low refractive index similar to highland regions, as has been suggested by earlier studies of these craters.
Precise determination of the isotopic composition of potassium: Application to terrestrial rocks and lunar soils
1995, Geochimica et Cosmochimica Acta
We detail a method for the precise and accurate determination of isotopic variations in the $^{41} K^{39} K$ ratio with a precision of ±0.5‰ (2σ_m). Purified potassium is chemically extracted from rocks, soils, minerals, or solutions by ion exchange chromatography. Complete chemical yields (>99.8%) are achieved in order to avoid laboratory-induced isotopic fractionations. The purified potassium is converted to a glass by melting with barium borate flux, and the resultant bead is mounted for ion probe analysis. The SIMS method utilized by the ion probe produces extremely stable K+ ion beams, with no measurable temporal variability in the isotope ratio. The instrumental fractionation is steady at about −4‰, and is corrected for by measurement of a standard. The measurement of gravimetrically prepared isotopic standards indicates that the method is accurate at the stated level of precision and free of egregious errors. Analysis of terrestrial samples including peridotite, basalts, granites, carbonatite, biotite schists, and seawater, indicate the complete absence of isotopic variations in δ41 1K among terrestrial materials at the 0.5%o level. Application to lunar soils and a regolith breccia confirms previously observed large isotopic fractionation effects (Garner et al., 1975a; Church et al., 1976). Some lunar soils, e.g., 14163, are shown to have large sample heterogeneity (≈7%o), while others, e.g., soils and a regolith breccia at several Apollo 15 sites (Station $79$ ), are homogeneous at the level of analytical precision. The presence of potassium isotopic effects in bulk soils (up to +12.7‰ in this study) with magnitudes comparable to the Rayleigh fractionation factor (25‰) indicates that volatility during micrometeorite impact melting played a large role in lunar regolith formation. As much as 15% of the regolith potassium has been lost from the Moon, through the tenuous lunar atmosphere.
Lunar Regolith Analogues: Spectral Reflectance Properties of Compositional Variations
1993, Icarus
The reflectance spectra of a number of glass and mafic silicate-bearing mineral mixtures designed to reproduce some of the spectral reflectance properties of lunar regoliths have been analyzed in order to assess how the reflectance spectra are altered by glass, end member abundance, and compositional variations. The reflectance spectra of glasses produced from different starting compositions show wide spectral variations attributable to differences in fusion times, techniques, and starting compositions. All the glasses show increasing reflectance toward longer wavelengths and very subdued or absent absorption bands. Olivine abundance and pyroxene compositional variations have the most dramatic effects on the spectra of mafic silicate-bearing mixtures in terms of changes in band positions, widths, depths, and areas and consequently are the easiest types of variations to recognize. Pyroxene, ilmenite, and plagioclase abundance variations cause less readily detectable changes in these spectral parameters. Plagioclase, being more weakly featured than mafic silicates, is difficult to unambiguously identify in mafic silicate-bearing mixture spectra unless its abundance exceeds ∼50 wt%. Continuum removal was applied to glass-bearing mineral mixtures in attempts to reconstruct band positions, widths, depths, and areas of glass-free mineral mixtures by dividing glass-bearing mixture spectra by a straight line continuum or by the spectrum of the glass used in the mixture. The results suggest that straight line continuum division is generally more effective at reproducing most of the diagnostic spectral parameters of the corresponding glass-free mixtures and hence is more effective for isolating and subsequently analyzing mineral absorption bands.
Reply to "Geochemistry of grain-size fractions of Luna 24 soil" by R. L. Korotev
1989, Geochimica et Cosmochimica Acta
Geochemistry of grain-size fractions of Luna 24 soil: Comments on "The lunar regolith: Chemistry and petrology of Luna 24 grain size fractions" by J. C. Laul, O. D. Rode, S. B. Simon, and J. J. Papike
1989, Geochimica et Cosmochimica Acta
Manufacture of glass and mirrors from lunar regolith simulant
2019, Journal of Materials Science

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The lunar regolith: Chemistry and petrology of Luna 24 grain size fractions

Abstract

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Chemical variability and origin of agglutinate glass

Origin and modal petrography of Luna 24 soils

Empirical correction factors for the electron microanalysis of silicates and oxides

J. Geol.

Major and trace element chemistry of Luna 24 samples for Mare Crisium

Geology of the Luna 24 landing site

Luna 24: Geologic setting of landing site and characteristics of sample core (preliminary data)

Debye-Scherrer investigations of experimentally shocked silicates

The Moon

Grain size evolution and fractionation trends in an experimental regolith

Soils from Mare Crisium: Agglutinate glass chemistry and soil development

Neutron activation of geological materials

Atomic Energy Review IAEA

The Apollo 17 Drill Core: Chemistry of size fractions and the nature of the fused soil components

The lunar regolith: Comparative chemistry of the Apollo sites

Chemistry and petrology of size fractions of Apollo 17 deep drill core 70009-70006

Chemistry, mineralogy and petrology of seven > 1 mm fragments from Mare Crisium

The Apollo 17 drill core: Chemical systematics of grain size fractions