Elemental Composition of Fluvial-Lacustrine and Lacustrine Coal-Bearing Environments, British Columbia, Canada

Abstract

Coal and interbedded rocks from the two coalfields in the southern intermontane region of British Columbia, Canada, deposited in fluvial-lacustrine, and lacustrine were examined using reflected light microscopy, instrumental neutron activation analysis (INAA), and inductively coupled plasma optical emission spectroscopy (ICPOES). Coals were deposited in the Paleogene period and under lacustrine (Hat Creek coalfields) and fluvial-lacustrine (Tulameen coalfield) conditions. The thorium/uranium ratio decreases rapidly with increasing authigenic uranium in the lacustrine Hat Creek. The Th/U ratio decreased slowly with increasing authigenic uranium in the fluvial setting due to a higher rate of sedimentation and an autochthonous origin of uranium. The intermontane coals have very low sulfur and pyrite content, typical of coals deposited in a freshwater environment. The elements of calcium, iron, magnesium, and manganese in these coals are found in the carbonate minerals ankerite, calcite, dolomite, and siderite and follow similar enrichment and depletion trends within the coal-bearing strata. The coal-bearing section in Tulameen is faulted. Some of the beds associated with major faults developed slickensides and became brittle. These beds have a high concentration of iron (38.5%), calcium (13.2%), and titanium (1.1%), which was the result of input by groundwater associated with the adjacent intrusive and extrusive rocks. Barium has a positive relationship with calcium, indicating its association with carbonates. Coals in the Hat Creek coalfield have high vanadium content with an average of 126 ppm compared to World coal (2–100 ppm). One coal sample (ash content = 13 wt %) has the highest vanadium content recorded in Canadian coals (897 ppm).

Coal quality, mineralogy, petrography, and geochemistry of the high-strontium Parçikan lignite

“…The B concentrations of the Bozburun coal samples are generally higher than 110 ppm (Table 4). Such concentrations could be evidence of paralic conditions (Goodarzi and Swaine, 1994;Goodarzi et al, 2020). The reported palynoflora and mollusc fauna from the Bozburun Formation suggest that freshwater conditions have been common (Türkmen et al, 2004;Nazik et al, 2008).…”

“…Besides, more recent studies show that these features of coal beds and partings in combination with coal petrography, palaeontological, and sedimentological data could provide significant information about the depositional conditions in the palaeomires (e.g., Finkelman et al, 2019;Dai et al, 2020a;Hood et al, 2020) for this purpose, indicative elements, and element ratios have been used (e.g., Goodarzi and Swaine, 1994;Dai et al, 2015aDai et al, , 2020aSpiro et al, 2019). For example, distributions of As, U, and Mo contents, along with Th/U ratio, are used for the determination of palaeoredox conditions in palaeomires, while distributions of total S, B, and Mo contents and Sr/Ba ratio serves as palaeosalinity indicator in palaeomires (Goodarzi and Swaine, 1994;Spiro et al, 2019;Dai et al, 2020a;Goodarzi et al, 2020;Çelik et al, 2021). Nevertheless, these index elements and elemental ratios should be used with caution, since coal seams have heterogeneous elemental and mineralogical compositions and certain accessory minerals (e.g., barite, chromite, monazite) can increase the concentrations of certain indicator elements (Finkelman et al, 2019;Dai et al, 2020a, b;Karayiğit et al, 2020a, b).…”