Diagenesis in Shales: Evidence from Backscattered Electron Microscopy and Electron Microprobe Analyses
T. J. Primmer, H. F. Shaw, 1985. "Diagenesis in Shales: Evidence from Backscattered Electron Microscopy and Electron Microprobe Analyses", Proceedings of the International Clay Conference Denver, 1985, Leonard G. Schultz, H. van Olphen, Frederick A. Mumpton
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Information gained from standard X-ray powder diffraction (XRD) analyses of Gulf Coast Tertiary and North Sea Mesozoic shales are compared with backscattered electron microscopy and electron microprobe data to illustrate the potential of backscattered electron imagery (BEI) for diagenetic studies of shales. The XRD analyses of Gulf Coast shales showed that one of the principal changes is the increased illitization of mixed-layer clays with depth. The electron microprobe data confirmed this change, but the BEI data revealed that closed microenvironments also exist within the shales, in which other diagenetic processes have taken place, e.g., the formation of authigenic kaolinite and chlorite. The XRD analyses of Mesozoic North Sea shales showed abrupt changes in the nature of illite/smectite compositions with stratigraphie position, suggesting that the compositional changes could be due to differences in detrital source materials. The BEI and probe analyses of these North Sea samples indicate a variety of diagenetic reactions in different microenvironments including dissolution, precipitation, and alteration involving phyllosilicate, feldspar, carbonate, and sulfide phases. The diagenetic reactions were found to vary significantly depending on the nature of the original sediments.
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Proceedings of the International Clay Conference Denver, 1985
The papers included in this proceedings volume are representative of the research on clays being conducted in all parts of the world at the time of publication. Many of the subjects treated are controversial, and although some ideas expressed may not necessarily represent the views of the editors, the referees, or the publisher, they deserve to be brought to the attention of the international clay community.