Conclusions regarding the nature of clay mineral transformations and the characteristics of those clays which have derived from XRD and TEM data are frequently conceived as being incompatible, especially as relates to smectite/illite and the concept of fundamental particles. Because conclusions are based on observations of metastable systems whose states are controlled by factors affecting kinetics, conclusions differ in part because of differences in rock types and environment of formation. TEM data are largely based on observations of shales, whereas other data are largely derived from bentonite and hydrothermal systems. We propose to study low-grade clay mineral systems using integrated XRD and TEM techniques to resolve differences in interpretation both in terms of methods and geological origin. Systems to be studied include bentonites from the Broadlands-Ohaaki geothermal field, North Sea geopressured siltstones, coeval metabasite and metabasite pairs over a broad range of grade, kerogen-rich black shales, and Salton Sea hydrothermal-metamorphosed sediments.
