Shuford Schuhmann

Luna 16 - Some Li, K, Rb, Sr, Ba, rare-earth, Zr, and Hf concentrations.

Abstract 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

Rb, Sr and strontium isotopic composition, K/Ar age and large ion lithophile trace element abundances in rocks and glasses from the Wanapitei Lake impact structure

Abstract Shock metamorphosed rocks and shock-produced melt glasses from the Wanapitei Lake impact structure have been examined petrographically and by electron microprobe. Eleven clasts exhibiting varying degrees of shock metamorphism and eight impact-produced glasses have been analyzed for Rb, Sr and Sr isotopic composition. Five clasts and one glass have also been analyzed for large ion lithophile (LIL) trace element abundances including Li, Rb, Sr, and Ba and the REEs. The impact event forming the Wanapitei Lake structure occurred 37 m.y. ago based on K/Ar dating of glass and glassy whole-rock samples. Rb/Sr isotopic dating failed to provide a meaningful whole-rock or internal isochron. The isotopic composition of the glasses can be explained by impact-produced mixing and melting of metasediments. Large ion lithophile trace element abundance patterns confirm the origin of the glasses by total shock melting of metasediments.

The Apollo 17 'melt sheet' - Chemistry, age and Rb/Sr systematics

Major, minor and trace element compositions, age data and Rb/Sr systematics of Apollo 17 boulders have been compiled, and additional analyses performed on a norite breccia clast (77215) included in the Apollo 17, Station 7 boulder. The Apollo 17 boulders are found to be identical or nearly so in major, minor and trace element composition, suggesting that they all originated as an impact melt analogous to melt sheets found in larger terrestrial craters. The matrix dates ( 40 Ar/ 39 Ar) and Rb/Sr systematics available suggest that this impact melt formed by a single impact about 4 b.y. ago. This impact excavated, shocked, brecciated and melted norites, norite cumulates and possibly anorthositic gabbros and dunites about 4.4 b.y. old. The impact was likely a major one, possibly the Serenitatis basin-forming event.

Major, minor and trace element abundances in samples from the Apollo 17 station 7 boulder - Implications for the origin of early lunar crustal rocks

Abstract Apollo 17 station 7 boulder consortia samples were analyzed for major and minor elements by a combined semimicro atomic absorption spectrophotometric and colorimetric procedure. Lithophile trace element abundances were determined by stable isotope dilution mass spectrometry. Three matrix types samples (77135, 77115, and 77075) were found to be KREEP-rich fragment-laden melts with analogues throughout the Apollo 17 landing site. Of the five clasts analyzed, at least one (77115,19, troctolite) is thought to be a cumulate; 77135, 77115, and 77075 are thought to have originated by impact fusion of material with similar composition. This original material may represent a partial melt of a parent material of the composition of an included, shocked norite breccia (77215).

Geochemistry of Apollo 15 Basalt 15555 and Soil 15531

Major and trace element concentrations have been determined by atomic absorption spectrophotometry, colorimetry, and isotope dilution in Apollo 15 mare basalt 15555 from the Hadley Rille area; trace element concentrations have also been determined in plagioclase and pyroxene separates from basalt 15555 and in soil 15531 from the same area. Basalt 15555 most closely resembles in composition the Apollo 12 olivine-rich basalts. The concentrations of lithium, potassium, rubidium, barium, rare-earth elements, and zirconium in basalt 15555 are the lowest, and the negative europium anomaly is the smallest, reported for lunar basalts; this basalt might be the least differentiated material yet returned from the moon. Crystallization and removal of about 6 percent of plagioclase similar to that contained in the basalt would account for the observed europium anomaly; if plagioclase is not on the liquidus of this basalt, a multistage origin is indicated. Mineral data indicate that plagioclase and pyroxene approached quasi-equilibrium. Most of the chemical differences between basalt 15555 and soil 15531 would be accounted for if the soil were a mixture of 88 percent basalt, 6 percent KREEP (a component, identified in other Apollo soils, rich in potassium, rare-earth elements, and phosphorus) and 6 percent plagioclase (anorthosite?).

Luna 20 and Apollo 16 core fines: large-ion lithophile trace-element abundances

Abstract Li, K, Rb and Sr abundances have been determined by mass-spectrometric stable isotope dilution analysis for a sample of Luna 20 fines and for eight fines from the Apollo 16 deep drill core. Ba and rare-earth abundances have also been determined for the Luna 20 sample and two of the Apollo 16 samples. Luna 20 and Apollo 16 were the first missions to interior highlands sites. The trace-element similarity of the fines samples may indicate that the lunar highlands are fairly homogeneous. An abundant feldspathic component is indicated. However, the negative Eu anomalies indicate that the fines cannot have been made entirely from earthly feldspathic cumulates. As in the case of the Apollo 12 and 15 core samples, the abundance of the large-ion lithophile trace elements increases with depth in the Apollo 16 core. It is suggested that Apollo 16 core material was lost during separation of the drill sections on the Moon.

Chapter 37G Mass-spectrometric stable-isotope-dilution analysis for lanthanides in geochemical materials

Publisher Summary This chapter presents the fundamental theory and scope of the stable isotope dilution mass-spectrometry (MSID) method. It describes the chemical preparation and the mass spectrometry of the samples, and explains data calculation and quality. MSID is the most accurate technique for determining lanthanide abundances in geochemical materials. The superior quality of the method may be attributed principally to the inherent sensitivity of mass-spectrometers, and to the use of the ideal internal standard—namely, an artificially enriched isotope of each element to be determined. The utilization of isotopic internal standards virtually eliminates potential analytical problems, such as quantitative recovery and instrument calibration. The sensitivity of the mass spectrometer is such that the lower limit of measurable abundance is usually controlled by the purity of the reagents used in preparing the sample for analysis.