Conditions of formation and sources of fluids of the birthplace of barren residential quartz of hydrothermal-metamorphogenic-metasomatic and hydrothermal-metamorphogenic genesis (Middle and South Urals)
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St Petersburg State University
Abstract
The paper considers the conditions of quartz formation of hydrothermal-metamorphogenic-
metasomatic and hydrothermal-metamorphogenic genesis of deposits and manifestations of
the Middle and Southern Urals based on the study of fluid inclusions by methods of thermobarogeochemistry,
ion and gas chromatography. It is established that the studied quartz objects
are formed in a wide temperature range, against the background of insignificant differences in
pressure values. It is shown that the temperatures of mineral formation in deposits of hydrothermal-
metamorphogenic-metasomatic genesis vary from 440–230 °C at a pressure of 1.2–1.4 kbar.
The formation of these veins occurred with the participation of K-Mg-Fe-chloride fluid with a salinity of 1.2–8.7 wt. % NaCl-eq., depleted Mg and Fe due to the deposition of magnesia-ferruginous
carbonates. A typomorphic feature of hydrothermal-metamorphogenic-metasomatic
quartz is the high values of boron associated with the placement of quartz veins among pegmatoids
and the presence of boron-containing mineral inclusions on quartz-vein objects. Veins of
hydrothermal-metamorphogenic genesis were formed when the crack system was filled with
quartz with the participation of a substantially K-Na chloride fluid (0.2–15.5 wt. % NaCl-eq.),
at homogenization temperatures of 435–335 °C and a pressure of 1.3–2.3 kbar. In the composition
of fluid inclusions of hydrothermal-metamorphogenic-metasomatic quartz, the sum of
“harmful” components (H2O, CO2, CH4, Cl, B, Na, K, Mg and Li) is less than in hydrothermal-
metamorphogenic quartz. The studied quartz deposits and veins were formed in the range
of temperatures and pressures not higher than the green shale stage during several successive
stages: the formation of quartz veins — in a more high-temperature hydrothermal stage, while
subsequent changes in quartz veins occurred under the influence of metamorphism processes,
with a decrease in temperature. Subsequent changes are associated with the appearance of fracturing,
cataclysm and recrystallization of quartz bodies with a decrease in grain size.
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Korekina, M. A., Savichev, A. N. (2023). Conditions of formation and sources of fluids of the birthplace of barren residential quartz of hydrothermal-metamorphogenic-metasomatic and hydrothermal-metamorphogenic genesis (Middle and South Urals). Vestnik of Saint Petersburg University. Earth Sciences, 68 (2), 200–217. https://doi.org/10.21638/spbu07.2023.201 (In Russian)