Element distribution in size fractions of Apollo-16 soils: Evidence for element mobility during regolith processes

William V. Boynton, C. L. Chou, R. W. Bild, P. A. Baedecker, J. T. Wasson

Research output: Contribution to journalArticle

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Abstract

Three Apollo-16 soils, 61220, 63500 and 65500, having diverse properties were separated into six size fractions and analyzed for 8 volatiles and siderophiles. Relative concentrations of an additional 20 elements were determined in 61220 and 63500. The volatile elements Cd, Zn, In and Ga increase in concentration with decreasing grain size; in the finest fractions the increase is roughly parallel to the increase in specific surface area, and a surface correlation is inferred. The total increase from coarsest (177-500 μm) to finest (<5 μm) fraction is by factors of 10-20 for Zn and Cd in soils 61220 and 63500. Concentrations of elements that are good indicators of KREEP (Sm), mare basalts (Fe) and anorthosites (Ca) show nearly no dependence on size. The preservation of the observed surface correlation throughout regolith evolution suggests that the volatile elements are labile on the lunar surface. Concentration-size distributions of siderophiles show peaks in the 80-300 μm range for each soil, independent of whether they are dominantly extralunar (Ni, Ge, Au, Ir) or lunar (Co) in origin. If this peak results from agglutinate formation, a viable mechanism must allow for incorporation of the extralunar siderophiles. Alternatively, the peak may result from a continuous growth of metal grain size during the evolution of the regolith.

Original languageEnglish (US)
Pages (from-to)21-33
Number of pages13
JournalEarth and Planetary Science Letters
Volume29
Issue number1
DOIs
StatePublished - 1976
Externally publishedYes

Fingerprint

element mobility
regolith
soils
volatile element
Soils
grain size
mare basalt
soil
anorthosite
Specific surface area
lunar surface
surface area
Metals
basalt
metal
distribution
metals

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Geochemistry and Petrology
  • Geophysics

Cite this

Element distribution in size fractions of Apollo-16 soils : Evidence for element mobility during regolith processes. / Boynton, William V.; Chou, C. L.; Bild, R. W.; Baedecker, P. A.; Wasson, J. T.

In: Earth and Planetary Science Letters, Vol. 29, No. 1, 1976, p. 21-33.

Research output: Contribution to journalArticle

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