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Apollo 11 lunar rock K, Rb, Sr, Ba and rare earth element concentrations, examining relationship to terrestrial and chondritic levels
Chemical analysis for Li, Na, K, Rb, Cs, Ca, Sr and Ba in achondrites and Apollo 11 lunar rocks, breccia and soil samples
Lunar chronology and evolution from Rb and Sr internal isochrons on Apollo 11 and 12 crystalline rock samples
Internal Rb-Sr isochrons were determined on four basaltic rocks and on a basaltic clast from a breccia from the Fra Mauro landing site. An internal isochron was determined for rock 12004 and yielded a value in agreement with previous results for basaltic rocks from the Apollo 12 site. The crystallization ages for Apollo 14 basalts are only 0.2 to 0.3 AE older than were found for mare basalts from the Sea of Tranquility. Assuming these leucocratic igneous rocks to be representative of the Fra Mauro site, it follows that there were major igneous processes active in these regions, and presumably throughout the highlands, at times only slightly preceding the periods at which the maria were last flooded.
Concentrations of Li, K, Rb, Sr, Na, rare-earths, Zr and Hf have been determined for some Luna 16 core materials by mass-spectrometric isotope-dilution. Two regolith fines samples from different depths in the core, and four rock-chips, including both igneous rocks and breccias, have similar trace-element concentrations. The Luna 16 materials have general lunar trace-element characteristics but differ from other returned lunar samples in a manner that suggests the presence of excess feldspar. Unless the Luna 16 igneous rocks are fused soils, they appear to represent either partial plagioclase cumulates or the least differentiated igneous material yet returned from the moon. The similarity in trace-element concentrations of the igneous rocks and the fines would then suggest largely local derivation of the Luna 16 regolith.
The effect of buffer gas and pumping light on the output frequency of the Rb-85 maser is discussed. In contrast to a primary standard, these frequency shifts can be used to advantage when it is necessary to operate the maser at a frequency which differs from the ground-state hyperfine frequency by a few kilohertz. Using appropriate mixtures of buffer gas and carefully shaped lamp spectral profiles, it is also possible to operate the maser exactly at the ground-state hyperfine frequency. It is pointed out that the short-term phase stability of the maser is not impaired by these shifts.
The concentrations of selected elements and elemental ratios in some Apollo 14 samples are presented in a table. Another table shows the isotopic composition of lead and strontium in some Apollo 14 samples. Graphs are provided with lead isotope ratio plots and a strontium evolution diagram. Rb-Sr ages are discussed together with isochron age methods of U-Th-Pb, a primary Pb-Pb isochron, a secondary Pb-Pb isochron, U-Pb concordia age relations, and U-Th-Pb concordia relations. Breccias and some soil samples as well as a basalt sample give evidence of significant enrichment of lead relative to uranium and thorium billions of years ago at the Fra Mauro site.
A description of measurements of light-shift and light-broadening parameters for an Rb-87 maser operating between the field independent levels is reported. A parallel study of the spectral profile of the D1 pumping line is described. Comparison between the experimental results and theoretical calculations, taking into account the spatial inhomogeneity of the pumping light in the absorption cell, is presented.
Plagioclase rich clasts, orthopyroxene rich matrix, purified pyroxene, and plagioclase from the Civet Cat clast define a Rb-Sr isochron age of 4.18 + or - 0.04 x 10 to the 9th power yr and an initial Sr-87/Sr-86 ratio of 0.69922 + or - 0.00005. The fit of all data to the line is within error except for plagioclase 3, and blank corrections are essentially negligible. The decay constant used is 1.39 x 10 to the minus 11th power yr.
Investigation results on the Rb-Sr systematics and K concentrations for two Apollo 14 breccias and several Apollo 15, 16, and 17 soils are reviewed. The reported results include the finding that plagioclase clasts from microbreccia fragments in Apollo 16 soil are distinctly too radiogenic to have been in equilibrium with the whole rock fragments 4 b.y. ago.
Results are presented on the relaxation and frequency shifts measured for the 0-0 transition of the ground state of Rb-85 at 3.03 GHz in various physical environments. These results include data on spin-exchange, buffer-gas, and wall interactions.
A new method for tuning the cavity of the Rb-87 maser is proposed. It is based on the existence of a cavity tuning for which the maser frequency is independent on the light intensity. The features of this method are evaluated theoretically and tested experimentally. Preliminary results obtained by using a closed loop feedback electronic system for tuning the cavity are given.
Rb and Sr isotopic data and other chemical data indicate major lunar differentiation at about 4.6 AE and very limited subsequent differentiation. The constraints of limited differentiation post 4.6 AE and the apparent lack of H2O on the moon, when applied to the derivation and petrogenesis of lunar samples, suggest the following: (1) soil samples, breccias, metaclastic rocks, and feldspathic basalts represent mixtures of repeatedly-modified clastic material, which was ultimately derived from materials formed during the about 4.6 AE differentiation; and (2) mare basalts crystallized from melts which formed by partial melting and, which developed without equilibration between the melt and crystalline residuum.
Measurements of Rb-Sr ages of crystallization performed on igneous lunar highland rocks 62295 and 14310 are reported. Lunar sample 62295 is a mesostasis-rich spinel-troctolite very-high-alumina basalt exhibiting a variable igneous structure. Sample 14310 is a feldspathic KREEP-rich basalt. The determined ages probably date the cooling of shock melts.
We have previously demonstrated that the Rb-Sr system of Fra Mauro breccia 14321 did not completely equilibrate at the time of assembly. Basalt and microbreccia clasts, with approximately the same internal isochron ages (about 4.0 b.y.) have distinctly different initial ratios. This result did not preclude the possibility that individual clast ages were reset by short range diffusion in a hot ejecta blanket. We now demonstrate that equilibration between basalt and adjacent microbreccia did not occur at about 4 b.y. on a 1 mm scale. The internal isochron ages of the clasts therefore probably date pre-assembly (possibly pre-Imbrium) magmatic and impact events. We also report the presence of a mare basalt clast in relatively KREEP-rich breccia 15265, indicating formation of such breccias after the basin-forming events.
The Vermilion district in Northeastern Minnesota is a classic example of a lower Precambrian greenstone-granite terrane in the Superior Province of the Canadian Shield. The present study presents new Rb-Sr isotopic data for the Ely Greenstone, the Newton Lake Formation, granitic pebbles that occur within the Ely Greenstone, a graywacke composite of the Knife Lake Group, and some Algoman granites whose data are complementary to those of Peterman et al. (1972). The isochron ages obtained are statistically indistinguishable and therefore cannot be used to resolve the timing of specific geologic events. Volcanic extrusion, granitic intrusion, and metamorphism are shown to be less contemporaneous events which probably took place within a time span of less than 50 m.y. A major conclusion is that a granitic basement probably did not underlie the Ely Greenstone.
High quality Rb-Sr data for lunar and terrestrial rocks older than 2.5 b.y. are examined, and the similarities and differences of the isotopic systematics in these rocks of different planetary bodies are compared. The implications of results of lunar studies for the early history of the earth are discussed.
Rb/Sr isotopic data and internal isochron ages are presented for some mare basalts from the Taurus-Littrow region. It is found that in age and in trace- and major-element chemistry as well as in Rb-Sr isotopic systematics, the Serenitatis mare basalts closely resemble the low-K Tranquility basalts, suggesting that over a wide region on the moon volcanism occurred at a discrete period 3.7-3.8 AE ago.