What are cleats? Preliminary studies from the Konin lignite mine, Miocene of central Poland
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Date
2014-03-31
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Wydawnictwo Naukowe UAM
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Abstract
Cleats (fractures, joints) are discontinuities in coals, including lignites. They are important in mining activity because of
their gas and water permeability in hard coal, and mainly because of their water permeability in lignites. As opposed
to hard-coal cleats, lignite cleats have not been studied in detail before. The present contribution does so, using as an
example the 1st Middle-Polish Lignite Seam (MPLS-1) in the Jóźwin IIB opencast mine in central Poland. It should be
mentioned here that any remarks in the present contribution concerning MPLS-1 refer exclusively to this lignite seam
in the Jóźwin IIB opencast mine.
The investigated discontinuities consist of two sets, i.e. the face and butt cleats, which are roughly oriented NW–SE and
NE–SW, respectively. The mean spacing of the face cleats is ~12.4 cm, while the mean spacing of the butt cleats is ~12.8
cm. The maximum average aperture is ~4.9 mm for the face cleats and ~4.1 mm for the butt cleats. The cleat spacing
and aperture do not depend on the lignite thickness, but the cleat spacing increases with increasing mineral-matter and
xylite content, whereas the aperture increases when the contents decrease. The regional folding and local salt diapirism
tentatively explain the formation of the orthogonal system of the lignite cleats, partly because of the parallelism of the
face cleats and the major tectonic directions in central Poland.
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Keywords
lignite cleats, structural geology, lignite seams, Miocene, central Poland
Citation
Geologos, 2014, 20, 1, s. 3-12
ISBN
978-83-232187-4-6