Volatile element depletion and K-39/K-41 fractionation in lunar soilsEvidence for selective loss and isotopic fractionation (in the case of K) of volatile elements during formation of agglutinates by micrometeoritic bombardment of lunar soils is presented. Concentrations and isotopic compositions of volatile elements (K, Rb, Pb) and nonvolatile elements (U, Th, Ba, Sr, rare earths) in separates taken from soils 14163, 14259, 15041, 68501, and 71500 are examined. Rayleigh fractionation calculations applied to K-39/K-41 isotopic data indicate ten-fold recycling of bulk soil, to account for observed isotopic anomalies. The lunar soil fines fraction seems to be a site of deposition for volatile or labile Pb produced during agglutination. Local fines (below 75 microns) are viewed as representative of the parent material for agglutinates formed in situ by micrometeoritic impact. Magnetic separation of agglutinates from soil 68501 revealed a bimodal population, with one class comprising welded blocky magnetic glasses.
Document ID
19770051824
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Church, S. E. (California Univ. Santa Barbara, CA, United States)
Tilton, G. R. (California Univ. Santa Barbara, CA, United States)
Wright, J. E. (California, University Santa Barbara, Calif., United States)
Lee-Hu, C.-N. (California, University Los Angeles, Calif., United States)