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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Petrology
Vol. 37 (1967)No. 4. (December), Pages 1006-1011

X-Ray Diffraction Techniques Applicable to Studies of Diagenesis and Low Rank Metamorphism in Humic Sediments

George M. Griffin

ABSTRACT

X-ray diffraction techniques are applicable to the study of humic materials ranging in rank from lignite to recta-anthracite. Techniques for sample preparation and analysis are described. During diagenesis and low rank metamorphism, the repeat distance of the graphite-like layers decreases progressively from 3.6-3.8 A in the lignite to high-volatile A bituminous group--to 3.5 A in the medium-volatile bituminous to anthracite group-to 3.35 A in meta-anthracite; this lattice collapse is related to the expulsion of volatiles. Also corresponding to the loss of volatiles from planar surfaces, the c aixs dimension of crystallites increases progressively from near 7 A in lignite--to near 20 A in medium to high rank coals--to 143 A in meta-anthracite. The observed changes are potentially appl cable to studies of insoluble organic residues extracted from humic rich shales and other normal sediments undergoing diagenesis and low rank metamorphism.


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