This work will apply transmission electron microscopy, analysis, and diffraction to several problems of petrological, geochemical, and geophysical importance. Rock-forming minerals can contain populations of submicroscopic inclusions that contain trace and minor elements, which may be significant for processes such as partial melting. It will be determined whether such inclusion dissolve prior to melting and the kinetics of the dissolution process. In situ studies of phase transformations in minerals will be continued. A combination of TEM, SEM, and electron microprobe analysis will be used to examine in detail the reactions and fluid flow regimes that occur during low-grade metamorphism of shale in the central Swiss Alps. Mechanisms of weathering that produce the detrital input for Abert Lake, an alkaline, saline lake in an arid environment, will be determined. The mineralogical and chemical changes occurring in the clays of the lake sediments during diagenesis will be analyzed. These changes have been shown to control the geochemistry of the lake waters.
