Cosmochemical Research

The chemical and physical conditions prevailing in the early solar system are recorded in the structure and composition the primitive ten-family group of meteorites designated as chondrites. The concentrations of the moderately and highly volatile trace elements (VTEs) provide information about the thermal history of the chondrites and the parent planets from which they are derived. The most volatile elements (Ag, Se, Cs, Te, Zn, Cd, Pb, Bi, In, and Tl) are particularly sensitive to subtle differences in their thermal history. This sensitivity can result in their fractionation between chondritic families and even between individual meteorite samples of the same family. While they occur as trace components in all mineral phases, the disposition or siting of the VTE with respect to mineral phase chemistry is uncertain. Methodologies that can accurately determine and evaluate distributions of the highly VTEs are crucial to understanding meteorite thermal history. Fundamentally, complete measurement of concentrations of major, minor, and trace elements in separated minerals could provide information regarding VTE affinity. We propose to develop and utilize methods that will allow us to determine the siting of the highly VTEs in chondritic meteorites. This goal will be achieved by developing inductively coupled plasma mass spectrometry for the analysis of major, minor, trace elements, and highly VTEs in minerals separated from the carbonaceous chondrites Allende and Murchison. We will use chemometric techniques to test null-hypotheses of highly VTE compositions between sample fractions to determine whether specific mineral phases contain significantly different concentrations of these elements. Comparisons will be made on both a univariate and multivariate basis. Techniques such as model-dependent and model-independent analysis of variance and linear discriminant analysis can be used for this purpose. Correlations within the highly VTEs as well as between the highly VTEs and other major and minor elements will be explored using factor analysis and by canonical correlation analysis. This project has been funded by the Research Corporation .

Allende is a Type III (CV3) carbonaceous chondrite that fell in Allende, Mexico on February 8, 1969. This meteorite formed during the solar nebula phase of our solar system 4.56 billion years ago and contains interstellar grains (remnants of a prior star that lived out its life and exploded before the formation of our Sun) within calcium/aluminum-rich inclusions (CAIs). Allende is volatile element rich and represents some of the oldest known matter

Murchison Meteorite

Murchison is a Type II (CM2) carbonaceous chondrite that fell on September 28, 1969 over Murchison, Australia. Over 100 kilograms of this meteorite have been found. Murchison is volatile rich and possesses a high water content of 12%. An abundance of amino acids found within this meteorite has led to intense study by researchers as to its origins. More than 92 different amino acids have been identified within the Murchison meteorite to date.

We have recently utilized ICPMS to determine the concentrations of 14 labile trace elements in the lunar meteorite Yamato 981031 to study the thermal history and geochemical evolution of the moon. We are comparing our data with existing analyses of Lunar and Martian samples using chemometric data analysis techniques (linear discriminant analysis, logistic regression, cluster analysis, and computer boot-strap randomization-simulations) to investigate the thermal histories of these two meteorite parent bodies. This project is being performed in collaboration with Professor M. E. Lipschutz of Purdue University.

Yamato 981031 Meteorite