The petrography, mineralogy and geochemistry of a paleocene lignite from southern Saskatchewan, Canada

The coal petrology, mineralogy, and elemental composition was determined on the 5-m-thick lignite of the Estevan seam, Bienfait Mine, southwest Saskatchewan. Organic petrology reveals a dominance of huminite macerals (73%), with minor liptinite (7%) and inertinite (11%) macerals. The maceral assemblage, and the banded nature of the coal suggests a forest moor depositional environment for the lignite. Optical and scanning electron microscopy, and X-ray diffraction reveals that the dominant mineralogy of the coal is quartz and carbonates with minor sulfates. The roof, parting and floor rock are dominated by quartz and clays, with minor feldspars. Elemental concentration is rather uniform with depth. Most elements are associated with the mineral matter, and increase with increasing ash content. The elements B, Na, Sr and Br are associated with the organic portion of the coal. Some elements show both a mineral and organic association (As, Ba, Co, Fe, Mo, Ce, Dy, Lu, W, U). The high concentrations of certain elements (Na, B, Ca) is attributed to groundwater circulation which can both introduce and remove elements from the porous lignite.