Sedimentary and low-grade metamorphic pelitic rocks record the occurrence, timing and magnitude of interaction with crustal fluids, but radiogenic isotopic studies of such rocks and events lead to ambiguous results due to heterogeneity of source of the key minerals, especially clay minerals. The project will combine radiogenic isotopic studies (Rb-Sr and K-Ar) with detailed characterization by scanning transmission electron microscopy (STEM) in order to provide a firm basis of interpretation of the isotopic data. The proposal is based on a successful "pilot project" development of methods for Rb-Sr analysis of Gulf Coast shales that have verified "episodic" diagenesis by tectonically- induced fluid flow. This research will expand the studies to the full range of diagenesis - low-grade metamorphism with further studies of Gulf Coast shales, and analyses of continuous sequences across northern New York and in Wales that span the range from late diagenesis to greenschist facies metamorphism.
