Репозиторий DSpace

Цифровой репозиторий ГГМ РАН

Репозиторий переведен на новую версию - DSpace 9.0. В репозитории содержится 43 600 публикации с тематикой "Науки о земле".

Сообщества в DSpace

Выберите сообщество для просмотра коллекций.

Показано 1 - 1 из 1

Геология России

Последние отправления

Geology, mineralization, and fluid inclusion characteristics of the Lermontovskoe reduced-type tungsten (±Cu, Au, Bi) skarn deposit, Sikhote-Alin, Russia
(2017) Soloviev S.G.; Kryazhev S.G.; Dvurechenskaya S.S.
The Lermontovskoe deposit (∼48 Kt WO3; average 2.6% WO3, 0.24% Cu, 0.23 g/t Au) is situated in a W-Sn-Au metallogenic belt that formed in a collisional tectonic environment. This tungsten skarn deposit has a W-Au-As-Bi-Te-Sb signature that suggests an affinity with reduced intrusion-related Au deposits. The deposit is associated with an intrusion that is part of the ilmenite-series, high-K peraluminous granitoid (granodiorite to granite) suite. These rocks formed via mantle magma-induced melting of crustal sources. The deposit comprises reduced-type, pyroxene-dominated prograde and retrograde skarns followed by hydrosilicate (amphibole-chlorite-pyrrhotite-scheelite-quartz) and phyllic (muscovite/sericite-carbonate-albite-quartz-scheelite-sulfide, with abundant apatite) alteration assemblages. Fluid inclusions from the skarn assemblages indicate high-temperature (>500 °C), high-pressure (1400–1500 bars) and high-salinity (53–60 wt% NaCl-equiv.) magmatic-hydrothermal fluids. They were post-dated by high-carbonic, methane-dominate, low-salinity fluid at the hydrosilicate alteration stage. These fluids boiled at 360–380 °C and 1300–1400 bars. The subsequent phyllic alteration started again with a high-temperature (>450 °C), high-pressure (1000–1100 bars) and high-salinity (42–47 wt% NaCl-equiv.) fluid, with further incursion of high-carbonic, methane-dominated, low-salinity fluid that boiled at 390–420 °C and 1150–1200 bars. The latest phyllic alteration included the lower-temperature (340–360 °C), lower pressure (370–400 bars) high-carbonic, methane-dominated (but with higher CO2 fraction), low-salinity fluid, and then the low-temperature (250–300 °C) H2O-CO2-CH4-NaCl fluid, with both fluids boiled at the deposit level. The high-salinity aqueous fluids are interpreted to have come from crystallizing granitoid magma, whereas the reduced high-carbonic fluids probably came from a deeper mafic magma source. Both of these fluids potentially contributed to the W-Au-As-Bi-Te-Sb metal budget. Decreasing temperatures coupled with high aCa2+ and fluid boiling promoted scheelite deposition at all post-skarn hydrothermal stages.
The Berezovsk giant intrusion-related gold-quartz deposit, Urals, Russia: Evidence for multiple magmatic and metamorphic fluid reservoirs
(2017) Vikent'eva O.V.; Bortnikov N.S.; Vikentyev I.V.; Groznova E.O.; Lyubimtseva N.G.; Murzin V.V.
The Berezovsk gold deposit in the Middle Urals has been mined for 270 years. Its endowment (past production and gold reserves) is estimated to be 490 t of gold. The deposit is located in the greenschist metamorphosed Silurian volcanogenic-sedimentary rocks intruded by granitoid dykes to the north-east of Late Carboniferous Shartash granite massif. Mineralisation is represented by sulphide-quartz veins in the granitoid dykes (“ladder” veins) and in the host rocks (“krassyk” veins) formed in the following four stages: ankerite-quartz, quartz-pyrite, gold-polymetallic and carbonate. Ore veins are accompanied by halos of gumbeite (quartz + orthoclase + carbonate), beresite (quartz + sericite + ankerite + pyrite) and listvenite (quartz + Fe-Mg carbonate + fuchsite + pyrite). The veins mainly consist of quartz with sulphide minerals (commonly 3–5 vol%). About 180 minerals have been identified in ores, but the most abundant minerals are quartz, calcite, ankerite, pyrite, galena, tennantite, chalcopyrite, aikinite, native gold, and sphalerite. Native gold was deposited during quartz-pyrite (Au I) and gold-polymetallic (Au II) stages. Fineness of gold ranges from 863 to 984 and from 723 to 848 for Au I and Au II, respectively. The mineral and metal zoning was identified relative to the roof of the Shartash granite massif. The fluid inclusion study revealed that the gold mineralisation at the Berezovsk deposit was formed at 300–230 °C and 0.3–2.3 kbar (mostly 0.5–1.2 kbar), from a H2O-CO2-NaCl fluid with salinity of 7.3–18.2 wt% NaCl equiv. The fluid was separated into H2O-CO2-NaCl and CO2-rich fluids due to temperature and/or pressure drop at the deposition site. Calculated δ18O and δD values are 5.2–8.1‰ and −39 to −63‰, respectively, for the fluid in equilibrium with alteration assemblages. The average δ13C value for the fluid equilibrated with carbonates from the inner zones of metasomatic halos is −5.3‰. The calculated δ18O and δ13C values are 3.0–9.6‰ and −3 to −9‰, respectively, for ore-forming fluids. The δ34S values are 1.4–12.9‰ and −1.6 to 11.7‰ for the fluid in equilibrium with early and late sulphides, respectively. In addition to the isotopic data, the geological, mineralogical and fluid inclusion data confirmed the predominant contribution of the magmatic fluid to formation of the Berezovsk hydrothermal system. The light C, O, and S isotope enrichment of the fluid was mainly caused by fluid phase separation. Fluids generated by decarbonation and dehydration reactions due to the contact metamorphism of the host rocks during the Shartash massif emplacement were responsible for additional 34S input. The ore-forming fluid was enriched in the light 16O isotope on the deposit flanks indicating the mixing with heated meteoric water.
The Vorontsovskoe Au-Hg-As ore deposit (Northern Urals, Russia): Geological setting, ore mineralogy, geochemistry, geochronology and genetic model
(2017) Murzin V.V.; Naumov E.A.; Azovskova O.B.; Varlamov D.A.; Rovnushkin M.Yu.; Pirajno F.
The large Vorontsovskoe Au-Hg-As deposit in the Urals is located in the exocontact of the Early Devonian Auerbah gabbro-diorite-granodiorite massif, which intrudes volcano-sedimentary rocks. The orebodies are confined to a tectonic contact of calcareous and tuffaceous rocks. They are composed of 6 types of disseminated ores, but the main reserves of gold are associated with the following ore types: gold-pyrite-arsenopyrite in altered tuffaceous rocks, pyrite-realgar ores in limestone breccia with a carbonate-volcanogenic cement, and gold-oxide-clay from regolith with residual gold. Early ore associations have been formed at 450–300 °C, whereas the late ores have been formed at lower temperature of 260–110 °C. We propose a model for the genesis of the Vorontsovskoe deposit based on synchronicity of mineralization with the formation of the Auerbah volcano-plutonic complex. The Ar-Ar age of hydromica from the gold-arsenopyrite association is 391.1 ± 4.9 Ma, which coincides with the age of igneous rocks of the Auerbah complex. The main sources of water and carbon dioxide were composed of the fluid derived from the magma chamber and the metamorphic water equilibrated with carbonate sedimentary rocks. Magmatic fluid dominated during the development of skarns, jasperoids and quartz veins, whereas metamorphic water was dominant during quartz-sericite alteration of volcano-sedimentary rocks and calcareous breccias. The bulk of the sulfur was supplied by a deep magma reservoir, however this source prevailed only during skarn ore formation. The mixing between deep-sourced sulfur and sedimentary or biogenic sulfur was established for other ore types. Gold and other ore components were possibly introduced during the volcanic and intrusive activity and also extracted from host sedimentary rocks.
Microheterogeneity of the Koupol Deposit Fahlores as a Reflection of Changing of Physicochemical Parameters of the Ore-forming Solution
(2013) Kemkin I.V.; Kemkina R.A.
New data on a zonal structure of the Koupol deposit fahlores grains are given, and features of their chemism are shown. The fahlores chemical composition within the zones evolves from essentially arsenious (Fe-tennantite and Zn-tennantite), through mixed fahlores (Zn-tennantite-tetrahedrite arsenious and Zn-tennantite-tetrahedrite antimonous), to essential antimonous (Ag-bearing Zn-tetrahedrite). Varying chemical composition manifested as mineralogical-geochemical zonation of the fahlores grains is caused by changes of physicochemical conditions of the ore forming process during the time.
ВЗАИМОСВЯЗАННЫЕ РЕАКЦИИ РАСТВОРЕНИЯ-ПЕРЕОТЛОЖЕНИЯ МИНЕРАЛОВ ТЕННАНТИТ-ТЕТРАЭДРИТОВОЙ СЕРИИ НА ЗОЛОТОРУДНОМ МЕСТОРОЖДЕНИИ ДАРАСУН (ВОСТОЧНОЕ ЗАБАЙКАЛЬЕ, РОССИЯ)
(2019) Любимцева Н.Г.; Бортников Н.С.; Борисовский С.Е.; Викентьева О.В.; Прокофьев В.Ю.
В золоторудном месторождении Дарасун обнаружены неоднородные ритмично-зональные агрегаты теннантита-IV, заместившие частично или полностью ранние однородные зерна Zn-тетраэдрита-I и идиоморфные кристаллы (Fe-Zn)-теннантита-I. Наблюдаются различные стадии замещения блеклой руды: оно начинается по границам зерен и заканчивается полным превращением в псевдоморфные агрегаты (Zn-Fe)-теннантита-IV, окаймленные Zn-тетраэдритом-IV. Последние тесно ассоциируют с бурнонитом и галенитом, отложение которых инициировало образование псевдоморфоз. Результаты РСМА показали, что на начальных стадиях отлагается (Fe-Zn)-тетраэдрит с более высоким содержанием As, чем в Zn-тетраэдрите-I. В зонально-неоднородном агрегате преобладает теннантит с широкими вариациями соотношений Sb/(Sb + As) и Fe/(Fe + Zn). В (Fe-Zn)-тетраэдрит-теннантите-IV проявлена отрицательная зависимость между соотношениями Sb/(Sb + As) и Fe/(Fe + Zn). В каждом участке на границе Zn-тетраэдрита-I и новообразованного теннантита-IV происходит разрыв смесимости между As и Sb и резкое падение Sb/(Sb + As) и увеличение Fe/(Fe + Zn). Резкие, зубчатые границы между Zn-тетраэдритом-I и новообразованным теннантитом-IV и наличие пор в новообразованном агрегате свидетельствуют о том, что образование псевдоморфоз произошло в результате взаимосвязанных реакций растворения-переотложения. Растворение инициировано нарушением химического равновесия между Zn-тетраэдритом-I и ненасыщенным флюидом из-за кристаллизации ассоциации галенита и бурнонита. Отложение тетраэдрит-теннантита-IV происходило при колебательных изменениях соотношений Sb/(Sb + As) и Fe/(Fe + Zn) из-за градиента концентраций во флюиде. По сфалерит-блеклорудному геотермометру рассчитана температура кристаллизации зонально-неоднородных агрегатов теннантита-IV, которая составила (134-161) ± 20 °С. Неустойчивость раннего Zn-тетраэдрита-I обусловлена охлаждением гидротермального флюида и снижением его солености и изменением растворимости тетраэдрита и теннантита из-за эволюции условий миграции полуметаллов.