Major, minor and trace element abundances in samples from the Apollo 17 station 7 boulder - Implications for the origin of early lunar crustal rocks
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Lithophile trace element abundances have been determined by mass spectrometric isotope dilution for a suite of Apollo 17 samples. The six mare basalts have generally similar relative trace element abundances; they are also similar to Apollo 11 trace element poor basalts. It is suggested that these basalts were derived by partial fusion of cumulates. The Apollo 17 highland breccias show an order of magnitude range in trace element abundances although there is a clustering of KREEP-rich samples which are interpreted as mixtures. The Apollo 17 soils show only a limited range of trace element abundances. They are mixtures of highland breccias, mare basalts, and orange-black 'soil'. There appear to be two groups of soils, Light Mantle and the rest. Both groups seem to have the same basalt component, which is similar to Station 4 basalt from Shorty Crater and probably is the uppermost basalt unit throughout the Taurus-Littrow valley.
Lithium, K, Rb, Sr, Ba, rare-earth, Zr, and Hf abundances have been determined by mass-spectrometric isotope-dilution for Apollo 16 soils, anorthosite 61016, and 'basalt' 68415 whole-rock and separated pyroxene and plagioclase. Our sample of 61016 is similar to some other lunar anorthosites in lithophile trace-element concentrations but at a slightly lower level. It was probably accumulated from a little differentiated basalt. Basalt 68415 might be a homogeneous mixture of KREEP and anorthosite material; it appears to have crystallized under conditions as reducing as those holding for mare-basalts. The soil fines cover only a limited compositional range. No obvious chemical differences were noted between the Descartes and Cayley formations. Most of the compositional variation of the soils can be accounted for in terms of the addition of plagioclase. The existence of very high alumina basalt as an independent magma-type appears debatable in view of its KREEP-like lithophile trace-element relative concentrations and the observed lunar radioactivity distribution.
Chemical analyses were obtained for five samples of Apollo 14 regolith fines, three 14230 core samples, soil clod 14049, breccias 14305 and 14319, 14310 basalt, and some separated phases. The chemical uniformity of these Apollo 14 samples indicates thorough mixing and/or uniform source rocks. Basalt 14310 can be matched well in composition by a four to one mixture of soil and plagioclase. The Eu(2+)/Eu(3+) ratios calculated for 14310 pigeonite and plagioclase are similar to those for Apollo 12 and 15 mare-type basalt phases; this indicates similar redox conditions. Apollo 14 samples are chemically similar to Apollo 12 and 15 KREEP as distinct from Apollo 11, 12, and 15 and Luna 16 mare-type basalts.
Chemical analyses have been obtained for five samples of Apollo 14 regolith fines, three 14230 core samples, 14049 soil clod, 14305 and 14319 breccias, 14310 basalt, and some separated phases. The chemical uniformity of these Apollo 14 samples indicates thorough mixing and/or uniform source rocks. Basalt 14310 can be matched well in composition by a four-to-one mixture of soil and plagioclase. Eu(2+)/Eu(3+) ratios calculated for 14310 pigeonite and plagioclase are similar to those for Apollo 12 and 15 mare-type basalt phases; this indicates similar redox conditions. The investigated Apollo 14 samples are chemically similar to Apollo 12 and 15 KREEP as distinct from Apollo 11, 12, and 15, and Luna 16 mare-type basalts. A relationship between the two types of basalt, in which mare-basalts would represent fused cumulates, is suggested.