The planning grant will be used to survey perthite microtextues from a variety of high-grade metamorphic rocks in the Adirondack Mountains. By relying on the well-documented metamorphic and igneous rocks of the Adirondacks, which record a wide range of pressure, temperature, and deformational regimes, it should be possible to document the textural and chemical behavior of alkali feldspars over a range of conditions. By revealing the details of chemical exchange and possible development of intracrystalline networks of micropores, this study will target possible limitations on the use of alkali feldspars in studies of stable isotope exchange, radiometric dating, geothermometry, geobarometry, weathering, permeability development, deformation mechanisms, etc. Samples from carefully selected localities in the Adirondacks will be analyzed by optical microscopy, a unique etching/SEM technique developed by the PI, and ultimately by TEM and electron microprobe. Part of the work will be carried out at the home institution and/or nearby labs, while a significant part will be done at Edinburgh University (where all necessary facilities are available at one location) during the PI's junior faculty leave. Once the feasibility of the methods has been tested, the PI will design an intensive study of one or more areas in the Adirondacks, and submit a full research proposal to EAR. 9
