U.S. Argentina Cooperative Research on Cenozoic Volcanism inthe Argentine Puna: Relation of Magmatic Source Areas to Evolving Tectonics

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This award supports the participation of Dr. Suzanne M. Kay of Cornell University in a program of cooperative research with Prof. Beatriz L. Coira of the Universidad National de Jujuy, Argentina, aimed at relating visible changes on the surface of the earth--collisions between adjacent "plates" reflected in the formation of mountain ranges or plateaus, for example--to the geochemistry of igneous rocks. Both very old and relatively young rocks from the high plateau region of central Argentina will be analyzed for major and trace element chemistry, and in some cases for isotopic composition, and the results will be correlated to the processes that were involved in the uplift of the plateau and generalized to the formation of mountain ranges and high plateaus generally. Our understanding of the growth and evolution of the earth's crust may be improved by studying the distribution and geochemistry of the volcanic rocks found at the intersections of the plates which form the earth's crust, since this geochemistry is a function of the time scale, thermal history, and structural mechanics of the formation of the crust. The high plateau of Argentina is an excellent location for the study of this geochemistry, due to the past concentration but current cessation of volcanic activity there. In addition, the area is well mapped geologically, both terrestrially and from satellites, and is well-known to local geologists. The proposed analysis of volcanic rocks should yield information on time scales and temperatures involved in the geological processes of the plateau's formation, and on the evolving chemistry of crust forming the plateau itself. Overall, the proposed study will make excellent complementary use of the U.S. principal investigator's expertise in geochemical analysis techniques, and the Argentine collaborator's expertise in field petrology, and should result in obtaining a fuller understanding of the processes that occur in the formation of mountain and high plateau regions in general.