U.S.-China Cooperative Research (Geochemistry): U-disequili-bria in Northeast Asian Alkali Basalts.

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The objective of this two-year cooperative research project between James Gill, University of California, Santa Cruz and Liang Zhoucheng, Chinese Academy of Sciences' Institute of Geochemistry is to perform U Th disequilibrium studies of Northeast Asian alkali basalts. The investigators will concentrate on "young" basalts from volcanic eruptions in Northern China 265 years ago. Through radioactive isotopic studies the investigators will determine the source of the Chinese basalts, study chemical fractionation during basalt genesis and date the age of the samples. U Th disequilbrium studies are useful tools for studying the origins of volcanic rocks, composition of the earth's mantle and the processes causing mantle heterogeneities. The U.S.-China collaboration is significant in several respects. U Th disequilbrium studies require "young" rocks and the investigators will have access to a unique source in China. Analysis will be performed in both U.S. and Chinese laboratories thereby enabling inter-laboratory calibration of samples. Research results will advance understanding of the nature of recent volcanic eruptions in northeast Asia (Japan, Korea and China) and its coupling to tectonic activities in this region. The combined efforts, complementary facilities of the Chinese and U.S. laboratories fulfill the principal objective of the U.S.-China program; which is, to advance scientific knowledge through international collaboration.