This project represents a continuation of research previously supported by NSF grant EAR82-18984, involving experimental studies of the diffusion of oxygen and cations in minerals. Specific objectives are to: 1.Measure oxygen diffusion in biotite, muscovite, and phlogopite micas, and in magnetite, garnet, and clinopyroxene, all under hydrothermal conditions, 2. Complete the measurements of Rb, Sr, and Pb diffusion in orthoclase, and of the REE, Nd and Er, in hornblende, and 3. To use the new methods developed in (2) to measure the diffusion kinetics of these elements in clinopyroxene, garnet, apatite, and plagioclase. The results will permit the quantitative assessment of the behavior of the geochronologically important systems Rb-Sr, Sm-Nd, and U-Th-Pb in rocks during episodes of heating. It will also be possible to set constraints on models of basalt genesis by partial melting in the mantle. It is important to know if the basalt magmas were not in chemical and isotopic equilibrium with their source rocks for all their constituents.
