SEM-EDS imaging of multi-stage cleat minerals formation in the South Walker Creek Coals, Bowen Basin

The South Walker Creek coals are moderately to highly developed fracture systems. These fractures can be recognized from the top to the bottom of the seam, with both open and closed apertures. They are filled with several different minerals, occurs either as single-phase infillings (monomineralic), or as mixed mineral deposits (polymineralic). This paper presents scanning electron microscope (SEM) analysis of mineralogical association within coals fractures or cleats, as well as their origin and phase of development. SEM-EDS analysis indicates that the polymineralic cleats seem to be more common in the coal seam compared to monomineralic cleats. The polymineralic cleat infillings are composed of clay minerals, carbonates, and other minerals, such rutile and apatite, with minor occurrences of diaspore. This polymineralic association within the single cleat spaces represents a multi-phase minerals formation, as a result of different stages of epigenetic activity. The hydrothermal fluid circulation are responsible for this epigenetic process, they are re-opened previous minerals filled cleats and transformed pre-existing mineral within the cleats, and/or to remobilization earlier minerals, which then precipitated in the cleat as epigenetic minerals.