Modern mineral formation in the geotechnogenic landscape of the Sherlovogorsky ore area (Eastern Transbaikalia)

The results of studying modern mineral formation in the geotechnogenic landscape of the Sherlovogorsk ore region in the South-Eastern Transbaikalia are summarized. The area of the deposit belongs to the mountain forest steppe. It is characterized by a sharply continental dry climate. As a result of almost 300-year-old mining of tin-polymetallic, beryllium-bismuth-tin-tungsten ores and gemstone raw materials, man-made arrays of mining wastes and substandard ores were formed. It has been established that under conditions of hypergenesis, intense oxidation of sulphides occurs with the formation of sulphate waters containing divalent iron, manganese, copper, zinc, cadmium, nickel and cobalt, magnesium. Here, from these waters, on the evaporative geochemical barriers, mineral associations of the sulfates of these chemical elements are formed. A feature of minerals is a wide isomorphism of cations with the formation of isomorphic series. The formation of sulphates of one cation with a variable number of crystal hydrate water molecules has also been established. For the group of kizerite, the following series was established: kieserite MgSO₄∙H₂O - gunningite ZnSO₄∙H₂O - szmikite MnSO₄∙H₂O and szomolnokite FeSO₄^H₂O, for the group of starkeyite: boyleite ZnSO₄^4H₂O - starkeyite MgSO₄^4H₂O -rozenite FeSO₄∙4H₂O - aplowite CoSO₄∙4H₂O. Intermediate mineral phases with a different number of fractions of mutually replacing chemical elements were revealed inside the row. mineral phases with a different number of fractions of mutually replacing chemical elements were revealed inside the row. As a result, ferrous gunningite, starkyite zincite, and other species are formed. The rows of sulphates of the same cation with a variable number of crystalline water for zinc and magnesium are represented most fully. Magnesium sulfates are represented by kieserite MgSO₄∙H₂O, MgSO₄∙3H₂O, not yet described in the literature, starkeyite MgSO₄∙4H₂O, pentahydrite MgSO₄∙5H₂O, hexahydrite MgSO₄∙6H₂O, epsomite MgSO₄∙7H₂O. Zinc sulfates are represented by the following: gunningite ZnSO₄∙H₂O, boyleite ZnSO₄∙4H₂O, bianchite ZnSO₄∙6H₂O, goslarite ZnSO₄∙7H₂O. Copper sulfates are represented by chalcocyanite CuSO₄, monohydrate copper sulfate CuSO₄∙H₂O, bonattite CuSO₄∙3H₂O, and chalcanthite CuSO₄∙5H₂O. A series of cobalt sulphates was also detected: aplite CoSO₄∙4H₂O, moorhouseite CoSO₄∙6H₂O, bieberite CoSO₄∙7H₂O. A series of NiSO₄∙4H₂O - Ni-hexahydrite Ni-SO₄∙6H₂O is outlined from nickel sulfates. Also, thin crusts of copper and zinc sulphates on snow and on the ice surface in winter as a result of cryomineragenesis were noted. The stability of the resulting mineral associations depends on weather and climatic conditions. They are stable only in the dry season or in dry hot or cold weather. During rains they dissolve in water and are washed away by temporary water flows. At this time, the ferrous and manganese sulphates are partially oxidized and undergo hydrolysis to form their hydroxides, sorbing weakly mobile lead, bismuth, antimony, arsenic and rare earths. Movable sulphates washed away by rainwater are carried to the lake at the bottom of the pit, increasing their concentration. The zinc content of the lake water reached 468 mg/l. The study of modern mineral formation is one of the tools for understanding the processes of hypergenesis.

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