Paper No. 7
Presentation Time: 9:45 AM


JOHNSON, Clark, Department of Geoscience, University of Wisconsin-Madison, NASA Astrobiology Institute, 1215 W. Dayton St, Madison, WI 53706, MCLENNAN, Scott M., Department of Geoscience, State University of New York - Stony Brook, Stony Brook, NY 11794, MCSWEEN, Harry Y., Earth & Planetary Sciences, University of Tennessee, Knoxville, TN 37996 and SUMMONS, Roger E., Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, MIT, E25-633, 77 Massachusetts Ave, Cambridge, MA 02139,

Many of the discoveries made in geochemistry over the last fifty years have been driven by technological advances that have allowed analysis of smaller samples, attainment of better instrumental precision and accuracy or computational capability, and automation that has provided many more data. These advances occurred during development of revolutionary concepts, such as plate tectonics, which has provided an over-arching framework for interpreting many geochemical studies. Also, spacecraft exploration of other planetary bodies, including analyses of returned lunar samples and remote sensing of Mars, has added an additional dimension to geochemistry. We will touch on but a few of the important insights into the evolution of the Earth and solar system that has been gained though geochemical studies over the last fifty years.

The technical advances that have occurred have been remarkable. Determination of elemental compositions of minerals and rocks, either through in situ analysis by various techniques (e.g., electron microprobe, SIMS, synchrotron XRF, laser ablation) or bulk analysis (e.g., XRF, ICP-AES, ICP-MS), have become essential approaches to many geochemical studies at levels of sensitivity and spatial resolution undreamed of five decades ago. Isotopic variations, whether produced by stable or radiogenic isotopes, provide a third dimension to the Periodic Table, and tremendous advances in instrumentation since the early 1960s have broadened this field of geochemistry. Mass spectrometers have diversified greatly in design and capability over the last five decades (e.g., IRMS, TIMS, MC-ICP-MS, SIMS), allowing isotopic analysis of many elements across the Periodic Table, including via in situ methods. As computing power has rapidly increased, geochemical modeling tools have become more sophisticated.

The individual sub-fields of geochemistry are becoming increasingly integrated, where systems are now viewed in a more holistic fashion, rather than in isolation related to a specific method or technique. This seems likely to continue in the future, and such an approach offers a comprehensive way to test multiple hypotheses and address geologic questions that continue to be important as we use geochemistry to better understand the geologic history of Earth and the solar system.