Some chemical data on british carboniferous sediments and their relationship to the clay mineralogy of these rocks
TL;DR: In this article, it is suggested that degraded illite supplied to the site of sedimentation had a bigher Na+ :K+ ratio than the illite now present in the shales and that post-depositional changes have caused a fall in this ratio.
Abstract: Analyses of shales, mudstones and associated strata from the British Coal Measures reflect the general similarity of the clay mineralogy of the rocks studied. Variations in the Na ~ :K+ ratio appear to be due to variations in the Na+ :K+ ratio in illite. It is suggested that degraded illite supplied to the site of sedimentation had a bigher Na+ :K+ ratio than the illite now present in the shales and that post-depositional changes have caused a fall in this ratio. Under conditions of rapid sedimentation such changes tend to be inhibited by rapid burial. In the seat earths, produced by very slow sedimentation, post-depositional changes continued to an advanced stage and resulted in low Na+ :K+ ratio in the final sedimentary rock.
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TL;DR: In this article, the authors apply current knowledge of clay colloid chemistry and mineralogy to the question of how water escapes from muddy sediments and find that water is compacted out of clay soon after burial, before the formation of hydrocarbons comparable with those found in reservoirs.
Abstract: The application of current knowledge of clay colloid chemistry and mineralogy to the question of how water escapes from muddy sediments suggests two conclusions. (1) The alteration of montmorillonite to illite takes place after deep burial and involves the transfer of large amounts of bound water from montmorillonite surfaces to interparticle areas where it is normal water. This water transfer has an important bearing on the porosity, permeability, abnormal fluid pressure, and initial release of hydrocarbons from mudrocks. (2) In deposits of primary illite, water is compacted out of clay soon after burial, before the formation of hydrocarbons comparable with those found in reservoirs. These points are important in petroleum exploration in new areas because it appears that the development of a shale source rock requires the initial deposition of a montmorillonitic organic mud, and its subsequent alteration to illite after deep burial. Abnormally high fluid pressures may easily be caused by a volume increase associated with the desorption of the last few monomolecular layers of water from montmorillonite during its diagenesis to illite. This understanding of mineralogical characteristics makes it possible to make meaningful interpretations of data on the bulk properties of compacting mudrocks.
305 citations
TL;DR: In this article, the major, minor and trace constituents have been made on a series of mudstones, seat earth and coal seam forming part of a Coal Measure succession encountered in an underground borehole at Bersham, North Wales.
82 citations
TL;DR: In this article, coal samples from the 170mthick A zone of the Hat Creek coal deposit No. 1 in central British Columbia were examined for major-, minor, and trace-element distribution.
76 citations
TL;DR: In this paper, the elemental compositions of coals from Fording, southeastern British Columbia, were examined using INAA and ICP spectrometry, and detailed elemental analyses were carried out for coal seams in two equivalent sections and also within selected coal seams.
67 citations
TL;DR: The results of a sedimentological reconnaissance in the area of the River and Gulf of St. Lawrence are discussed in this article, mainly concerned with the relationship between submarine topography, surface sediments, sediment sources and present processes of deposition.
35 citations