Mineral Inclusions in Coals of Transbaikalia
Abstract Generated abstract
This paper examines mineral inclusions in coals from the Tarbagatai, Kharanor, and Chernovskoe deposits of Transbaikalia using hand specimens, thin and polished sections, and spectral analysis data. It distinguishes terrigenous inclusions, including gold, quartz, and feldspar, from authigenic minerals, with the latter classified as syngenetic or epigenetic. The study describes the occurrence and morphology of pyrite, spherosiderite, kaolin, and hydromica, noting deposit-specific features such as gold in the Tigninskii seam and spherosiderite in Chernovskoe coals. It concludes that terrigenous minerals entered the peat-forming basin during coal accumulation, whereas pyrite, spherosiderite, and clay minerals were introduced later by infiltrating or formation waters and deposited in fractures and voids.
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MINERAL INCLUSIONS IN THE COALS OF TRANSBAIKALIA
O. A. Dulzon
(Presented by the scientific seminar of the Department of Combustible Minerals)
To date, coal petrographers have discovered more than 30 minerals in coals. Some mineral inclusions are observed with the naked eye, others only under a microscope, and still others by spectral methods.
In studying mineral impurities in the coals of the Tarbagatai, Kharanor, and Chernovskoe deposits, we examined hand specimens, thin sections, polished sections, and data from spectral analyses.
Among the mineral inclusions in Transbaikalian coals, it is necessary to distinguish allochthonous, or terrigenous, and autochthonous, or authigenous, inclusions. The autochthonous, in turn, are divided into syngenetic and epigenetic.
Terrigenous mineral inclusions include gold, quartz, and feldspar.
Gold—a native element—is represented by small yellow inclusions with angular, slightly rounded edges. Gold inclusions were found mainly in the coal of the Tigninskii seam, which adjoins the southern side of the open-pit coal mine of the Tarbagatai deposit.
Quartz is observed in polished sections in the form of angular fragments and rounded grains of light-gray color. The quartz fragments contain dendrite-like inclusions and fine disseminations of pyrite.
Feldspar occurs in polished sections in the form of small angular fragments of gray color.
Epigenetic minerals include pyrite, spherosiderite, and clay material.
Pyrite in the coals is observed in the form of ferruginous films, rosettes, and, more often, it fills the cellular openings of plant tissues. Large spherical and cubic pyrite inclusions occur in the argillite deposits of the roof of the Tigninskii coal seam of the Tarbagatai deposit.
Spherosiderite is represented by small concretions of dark-brown color with a radial-fibrous structure. Spherosiderite concretions are observed both on the surface of coal hand specimens and under the microscope. Spherosiderites occur only in the Chernovskoe coals.
Clay material is represented by two minerals: kaolin and hydromica. Kaolin and hydromica were brought into the coal by formation waters.
In conclusion, it should be noted that gold, quartz, and feldspars were deposited in the peat bog in the coal-accumulation basin. Pyrite, spherosiderite, and clayey material penetrated into already formed coal seams in the form of dissolved salts carried by infiltrating flows and were deposited on the walls of fractures, filling all the voids in the coal. Kaolin and hydromicas were introduced into the coal by formation waters from the roof of the coal seam, composed predominantly of argillites and siltstones.