The redox state of chromium ores of the Polar Urals

Cover Page

Cite item

Full Text

Open Access Open Access
Restricted Access Access granted
Restricted Access Subscription Access

Abstract

The redox state of chromium ores of the main industrially significant types, developed in ultramafic rocks of the Rayiz-Voikar complex of the Polar Urals, was studied. The chromitites occurring in various geological settings – rocks of the dunite-harzburgite complex and large dunite bodies – have been investigated. For the first time, on a representative sample of analyzes (more than 150 samples), an assessment was made of oxygen fugacity and temperature of olivine-spinel equilibrium in chromium ores of the Rai-Iz and Voikaro-Syninsky massifs.

At each of the studied objects, the iron content of minerals increases linearly from chromitites to their host ultramafic rocks. The temperature of olivine-spinel equilibrium in chromitites varies within 550–800оС. The oxygen fugacity in aluminous chromitites averages FMQ +0.5–1.5 log. units, in medium chromium – FMQ +1.5–2.5 log. units, in high-chromium ones it exceeds +2.5 log. units relative to the FMQ buffer. The fugacity of oxygen in densely disseminated chromitites is 0.5–1 log. units higher than in poorly disseminated and rarely disseminated. The values of T-fO2 parameters correspond to the crustal conditions and are close to those established in the metaultramafites of the studied massifs.

The data obtained may indicate that the concentration of the ore component and the formation of chromium ore deposits occur not only in mantle or lower crustal conditions, characterized by fO2 values close to the FMQ buffer, but also as a result of ultramafic crustal metamorphism occurring in an oxidizing environment.

Full Text

Restricted Access

About the authors

P. B. Shiryaev

Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences

Author for correspondence.
Email: pavel.shiryayev@gmail.com
Russian Federation, 620016, Yekaterinburg, st. Academician Vonsovsky, 15

N. V. Vakhrusheva

Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences

Email: pavel.shiryayev@gmail.com
Russian Federation, 620016, Yekaterinburg, st. Academician Vonsovsky, 15

References

  1. Батанова В.Г., Савельева Г.Н. Миграция расплавов в мантии под зонами спрединга и образование дунитов замещения: обзор проблемы // Геология и геофизика. 2009. Т. 50. № 9. С. 992–1012.
  2. Белоусов И.A., Батанова В.Г., Савельева Г.Н., Соболев А.В. Свидетельство надсубдукционной природы мантийных пород Войкаро-Сыньинского офиолитового массива, Полярный Урал // Докл. РАН. 2009. Т. 429. № 2. С. 238–243.
  3. Бортников Н.С., Лобанов К.В., Волков А.В., Галямов А.Л., Викентьев И.В., Тарасов Н.Н., Дистлер В.В., Лаломов А.В., Аристов В.В., Мурашов К.Ю. Месторождения стратегических металлов Арктической зоны // Геология руд. месторождений. 2015. Т. 57. № 6. С. 479–500.
  4. Вахрушева Н.В., Ширяев П.Б., Степанов А.Е., Богданова А.Р. Петрология и хромитоносность ультраосновного массива Рай-Из Полярный Урал. Екатеринбург: ИГГ УрО РАН, 2017. 265 с.
  5. Добрецов Н.Л., Молдаванцев Ю.Е., Казак А.П. и др. Петрология и метаморфизм древних офиолитов (на примере Полярного Урала и Западного Саяна) // Тр. Ин-та геол. и геоф. Сиб. отд. АН СССР. Новосибирск: Наука, Сибирское отделение, 1977. Вып. 368. 221 с.
  6. Зылёва Л.И., Коновалов А.Л, Казак А.П. и др. Государственная геологическая карта Российской Федерации. Масштаб 1 : 1 000 000 (3-е покол.). Сер. Зап.-Сибирская. Лист Q-42 – Салехард. Об. зап. СПб.: ВСЕГЕИ, 2014, 396 с.
  7. Книппер А.Л. Океаническая кора в структуре альпийской складчатой области: (юг Европы, западная часть Азии и Куба). М.: Наука, 1975. 208 с.
  8. Колман Р.Г. Офиолиты. М.: Мир, 1979. 262 с.
  9. Макеев А.Б., Брянчанинова Н.И. Топоминералогия ультрабазитов Полярного Урала. СПб.: Наука, 1999. 252 с.
  10. Макеев А.Б., Брянчанинова Н.И. Крупномасштабное минералогическое картирование хромитоносных участков на примере Хойлинского рудного узла (Войкаро-Сыньинский массив, Полярный Урал) Статья 2. Особенности образования и преобразования руд и пород // Изв. ВУЗов. Геология и разведка. 2014. № 2. С. 15–22.
  11. Маракушев А.А., Панеях Н.А., Горбачев Н.С., Зотов И.А. Минералого-геохимическая специфика гигантских месторождений хрома и платиновых металлов и проблема глубинности их мантийных источников // Крупные и суперкрупные месторождения: Закономерности размещения и условия образования. М.: ОНЗ РАН, 2004. С. 137–159.
  12. Методические рекомендации по применению Классификации запасов месторождений и прогнозных ресурсов твердых полезных ископаемых. Хромовые руды. М.: ФГУ ГКЗ МПР РФ, 2007. 36 с.
  13. Николаев Г.С., Арискин А.А., Бармина Г.С., Назаров М.А., Альмеев Р.Р. Тестирование Ol-Opx-Sp оксибарометра Балльхауса-Берри-Грина и калибровка нового уравнения для оценки окислительного состояния расплавов, насыщенных оливином и шпинелидом // Геохимия. 2016. № 4. С. 323–343.
  14. Никольская Н.Е., Казеннова А.Д., Николаев В.И. Типоморфизм рудообразующего хромшпинелида месторождений хромовых руд // Минеральное сырье. № 42. М.: ФГБУ “ВИМС”, 2021. 238 c.
  15. Павлов Н.В. Химический состав хромшпинелидов в связи с петрографическим составом пород ультраосновных интрузивов // Труды института геол. наук. Серия рудных месторождений. 1949. Вып. 103. 87 с.
  16. Павлов Н.В., Кравченко Г.Г., Чупрынина Г.Г. Хромиты Кемпирсайского плутона. М.: Наука, 1968. 178 с.
  17. Перчук Л.Л., Рябчиков И.Д. Фазовое соответствие в минеральных системах. М.: Недра, 1976. 287 с.
  18. Перевозчиков Б.В., Кениг В.В., Лукин А.А., Овечкин А.М. Хромиты массива Рай-Из на Полярном Урале (Россия) // Геология руд. месторождений. 2005. № 47 (3). С. 230–248.
  19. Плечов П.Ю., Щербаков В.Д., Некрылов Н.А. Экстремально магнезиальный оливин в магматических породах // Геология и геофизика 2018. № 59(12). С. 2129–2167. https://doi.org/10.15372/GiG20181212
  20. Пушкарев Е.В., Каменецкий В.С., Морозова А.В., Хиллер В.В., Главатских С.П., Родеманн Т. Онтогения рудных хромшпинелидов и состав включений как индикаторы пневматолито-гидротермального образования платиноносных хромититов массива Кондер (Алданский щит) // Геология руд. месторождений. 2015. Т. 57. № 5. С. 394–423.
  21. Савельева Г.Н. Габбро-ультрабазитовые комплексы офиолитов Урала и их аналоги в современной океанической коре. М.: Наука, 1987. 244 с.
  22. Савельева Г.Н., Батанова В.Г., Соболев А.В., Кузьмин Д.В. Минералы мантийных перидотитов – индикаторы хромовых руд в офиолитах // Докл. РАН. 2013. Т. 452. № 3. С. 313–316.
  23. Савельева Г.Н., Батанова В.Г., Кузьмин Д.В., Соболев А.В. Состав минералов мантийных перидотитов как отражение рудообразующих процессов в мантии (на примере офиолитов Войкаро-Сыньинского и Кемпирсайского массивов) // Литология и полезные ископаемые. 2015. № 1. С. 87–98.
  24. Савельева Г.Н., Перцев А.Н. Мантийные ультрамафиты в офиолитах Южного Урала, Кемпирсайский массив // Петрология. 1995. Т. 3. № 2. С. 115–132.
  25. Cимонов В.А., Смирнов В.Н., Иванов К.С., Ковязин С.В. Расплавные включения в хромшпинелидах расслоенной части Ключевского габбро-гипербазитового массива // Литосфера. 2008. № 2. С. 101–115.
  26. Строение, эволюция и минерагения гипербазитового массива Рай-Из. Ред.: Пучков В.Н., Штейнберг Д.С. Свердловск: УрО АН СССР, 1990. 228 с.
  27. Царицын Е.П., Алимов В.Ю. Оливин-хромшпинелидовые парагенезисы в гипербазитах Кемпирсайского массива // Минералы и парагенезисы минералов месторождений Урала. Свердловск: УНЦ АН СССР, 1983. С. 87–102.
  28. Чащухин И.С., Вотяков C.Л., Щапова Ю.Л. ЯГР кристаллохимия хромшпинели и окситермобарометрия ультрамафитов складчатых областей. Екатеринбург: ИГГ УрО РАН, 2007. 345 с.
  29. Чащухин И.С., Перевозчиков Б.В., Царицын Е.П. Метаморфизм гипербазитов массива Рай-Из (Полярный Урал) // Исследования по петрологии и металлогении Урала. УНЦ АН СССР, 1986. С. 49–75.
  30. Ширяев П.Б., Вахрушева Н.В. Особенности состава и условий образования рудообразующих хромовых шпинелей южного участка месторождения Центральное (массив Рай-Из) // Ежегодник-2016. Труды ИГГ УрО РАН. 2017. № 164. С. 204–206.
  31. Шмелев В.Р. Мантийные ультрабазиты офиолитовых комплексов Полярного Урала: петрогенезис и обстановка формирования // Петрология. 2011. Т. 19. № 6. С. 649–672.
  32. Arai S., Abe N. Reaction of orthopyroxene in peridotite xenoliths with alkali basalt melt and its implication for genesis of alpine-type chromitite // Amer. Mineral. 1995. V. 80. P. 1041–1047.
  33. Arai S., Akizawa N. Precipitation and dissolution of chromite by hydrothermal solutions in the Oman ophiolite: new behavior of Cr and chromite // Amer. Mineral. 2014. V. 99. V. 28–34.
  34. Arai S., Miura M. Formation and modification of chromitites in the mantle // Lithos. 2016. V. 264. P. 277–295.
  35. Ballhaus C., Berry R.F., Green D.H. Experimental calibration of the olivine-orthopyroxene-spinel oxygen barometer – implications for oxygen fugacity in the Earth’s upper mantle // Contrib. Miner. Petrol. 1991. V. 107. P. 27–40.
  36. Borisova A.Y., Ceuleneer G., Arai S., Kamenetsky V., Béjina F., Polvé M., Aigouy T., Pokrovski G.S. A new view on the petrogenesis of the Oman ophiolite chromitites from microanalyses of chromite-hosted inclusions // J. Petrol. 2012. V. 53. Р. 2411–2440.
  37. Dare S.A., Pearce J.A., McDonald I., Styles M.T. Tectonic discrimination of peridotites using fO2–Cr# and Ga-Ti-FeIII systematics in chrome–spinel // Chem. Geol. 2009. V. 261. P. 199–216.
  38. Dilek Y., Furnes H. Ophiolite genesis and global tectonics: Geochemical and tectonic fi ngerprinting of ancient oceanic lithosphere // Geological Society of America Bulletin. 2011. V. 123. P. 387–411.
  39. Hu W.-J., Zhou M.-F., Yudovskaya M.A., Vikentyev I.V., Malpas J., Zhang P.-F. Trace elements in chromite as indicators of the origin of the giant podiform chromite deposit at Kempirsai, Kazakhstan // Econ. Geol. 2022. V. 117(7). P. 1629–1655. https://doi.org/10.5382/econgeo.4955
  40. Irvine T.N. Chromian spinel as a petrogenetic indicator. Part 2. Petrologic applications // Can. J. Earth Sci. 1967. V. 4. P. 71–103.
  41. Klemme S., O’Neill H.S.C. The effect of Cr on the solubility of Al in orthopyroxene: experiments and thermodynamic modeling// Contrib. Mineral. Petrol. 2000. V. 140. P. 84–98.
  42. Lécuyer C., Yanick R. Long-term fluxes and budget of ferric iron: Implication for the redox state of the Earth’s mantle and atmosphere // Earth Planet. Sci. Lett. 1999. V. 165. P. 197–211.
  43. Li C., Ripley E.M., Sarkar A., Shin D., Maier W.D. Origin of phlogopite-orthopyroxene inclusions in chromites from the Merensky Reef of the Bushveld Complex, South Africa // Contrib. Miner. Petrol. 2005. V. 150. P. 119–130.
  44. McСammon C.A. Mantle Oxidation State and Oxygen Fugacity: Constraints on Mantle Chemistry, Structure, and Dynamics // Earth’s Deep Mantle: Structure, Composition, and Evolution (eds R.D. Van Der Hilst, J.D. Bass, J. Matas and J. Trampert). American Geophysical Union, 2005. 334 p.
  45. Melcher F., Grum W., Simon G., Thalhammer T.V., Stumpfl E.F. Petrogenesis of the ophiolitic giant chromite deposits of Kempirsai, Kazakhstan: a study of solid and fluid inclusions in chromite // J. Petrol. 1997. V. 38. P. 1419–1458.
  46. O’Neill H.S.C., Rubie D.C., Canil D., Geiger C.A., Ross II C.R., Seifert F., Woodland A.B. Ferric iron in the upper mantle and in transition zone assemblages: implications for relative oxygen fugacities in the mantle // Evolution of the Earth and Planets, International Union of Geodesy and Geophysics and the American Geophysical Union, Geophysical Monograph 74. IUGG, 1993. V. 14. P. 73–88.
  47. O’Neill H.S.C., Wall V.J. The olivine-orthopyroxene-spinel oxygen geobarometer, the nickel precipitation curve, and the oxygen fugacity of the Earth’s upper mantle // J. Petrol. 1987. V. 28. P. 1169–1191.
  48. Osborne M.D., Fleet M.E., Michael Bancroft G. Fe2+-Fe3+ ordering in chromite and Cr-bearing spinels // Contrib. Mineral. Petrol. 1981. V. 77(3). P. 251–255.
  49. Orcutt B., Daniel I., Dasgupta R.. Orcutt B. Deep Carbon: Past to Present. Cambridge: Cambridge University Press, 2019. 653 p.
  50. Parkinson I.J., Arculus R.J. The redox state of subduction zones: insights from arc-peridotites // Chem. Geol. 1999. V. 160. P. 409–423.
  51. Parkinson I.J., Pearce J.A. Peridotites from the Izu–Bonin–Mariana forearc (ODP Leg 125): evidence for mantle melting and melt–mantle interaction in a supra-subduction zone setting // J. Petrol. 1998. V 39 (9). P. 1577–1618.
  52. https://doi.org/10.1093/petroj/39.9.1577
  53. Payot B.D., Arai S., Tamayo R.A. Graciano Y.P. Textural Evidence for the Chromite-Oversaturated Character of the Melt Involved in Podiform Chromitite Formation // Resource geology. 2013. V 63 (3). P. 313–319.
  54. Roeder P.L., Campbell L.H. and Jamieson H.E. A re-evaluation of the olivine-spinel geothermometer // Contrib. Mineral. Petrol. 1979. V. 68. P. 325–334.
  55. Roeder P.L., Reynolds I. Crystallization of chromite and chromium solubility in basaltic melts // J. Petrol. 1991. V. 32. P. 909–934.
  56. Satsukawa T., Piazolo S., González-Jiménez J.M., Colás V., Griffin W.L., O’Reilly S.Y., Gervilla F., Fanlo I., Kerestedjian T.N. Fluid-present deformation aids chemical modification of chromite: insights from chromites from Golyamo Kamenyane, SE Bulgaria // Lithos. 2015. V. 228. P. 78–89.
  57. Saveliev D.E. Chromitites of the Kraka ophiolite (South Urals, Russia): Geological, mineralogical and structural features // Miner. Depos. 2021. V. 56 P. 1111–1132. https://doi.org/10.1007/s00126–021–01044–5
  58. Snethlage R., Von Gruenewaldt G. Oxygen fugacity and its bearing on the origin of chromitite layers in the Bushveld Complex // Time- and strata-bound ore deposits. Klemm D.D. and Schneider H.J., eds. Berlin: Springer-Verlag, 1977. P. 352–370.
  59. Shiryaev P.B., Vakhrusheva N.V. Chemical zoning of ore-forming spinels from Cr-saturated and Al-rich chromitites of the Voikaro-Syninsky massif // Известия Уральского государственного горного университета. 2021. № 2 (62). P. 39–47. https://doi.org/10.21440/2307–2091–2021–2–39–47
  60. Schiano P., Clocchiatti R., Lorand J.-P., Massare D., Deloule E., Chaussidon M. Primitive basaltic melt included in podiform chromites from the Oman ophiolite // Earth Planet. Sci. Lett. 1997. V. 146. P. 489–497.
  61. Tesalina, S.G, Nimis P., Auge T., Zaykov, V. Origin of chromite in mafic-ultramafic-hosted hydrothermal massive sulfides from the Main Uralian Fault, South Urals, Russia // Lithos. 2003. V. 70. P. 39–59.
  62. Woodland A.B., Kornprobst J., Tabit A. Ferric iron in orogenic lherzolite massifs and controls of oxygen fugacity in the upper mantle // Lithos. 2006. V. 89. № 1–2. P. 222–241.
  63. Xiong F., Zoheir Basem, Robinson P.T., Yang Jingsui, Xu X., Meng F. Genesis of the Ray-Iz chromitite, Polar Urals: Inferences to mantle conditions and recycling processes // Lithos. 2020. V. 374–375.
  64. https://doi.org/10.1016/j.lithos.2020.105699
  65. Zhang P, Zhou M, Yumul G.P. Coexistence of high-Al and high-Cr chromite orebodies in the Acoje block of the Zambales ophiolite, Philippines: Evidence for subduction initiation // Ore Geol. Rev. 2020. V. 126. 103739.
  66. https://doi.org/10.1016/j.oregeorev.2020.103739
  67. Zhou M.-F., Robinson P.T., Bai W.-J. Formation of podiform chromitites by melt/rock interaction in the upper mantle // Mineral. Deposita. 1994. V. 29. P. 98–101.

Supplementary files

Supplementary Files
Action
1. JATS XML
Download
2. Fig. 1. Layout of the ultramafic massifs Rai-Iz and Voikaro-Syninsky (after Zyleva et al., 2014, Savelyeva et al., 2015; Vakhrusheva et al., 2017). Legend: 1 – ultramafic rocks of the Rayiz-Voykar complex; 2 – serpentinite melange; 3 – Kershor dunite-wehrlite-pyroxenite-gabbro complex; 4 – complex of diabase dikes; 5 – metamorphic complexes; 6 – sedimentary complexes; 7 – regional strike-slip faults and strike-slip faults; 8 – boundaries of formations of different ages; 9 – studied chromium ore objects: 1 – Central deposit, 2 – Engaiskoye-1 ore occurrence, 3 – Arkashorskoye ore occurrence, 4 – Yambotyvissky ore occurrences; 10, 11 – ultramafic massifs: 10 – Rai-Iz, 11 – Voykar-Syninsky.

Download (667KB)
Indexing metadata
3. Fig. 2. Schematic geological map of the Central deposit (based on materials (Perevozchikov et al., 2005; Shiryaev, Vakhrusheva, 2017)). Legend: 1 – 4 rocks of the dunite-harzburgite complex with different contents of the dunite component (1 – <10%; 2–10–30%; 3–30–50%; 4–50–70%); 5 – dunites; 6 – serpentinites; 7 – diabase; 8 – geological boundaries; 9, 10 – tectonic disturbances of the 1st and 2nd ranks, respectively; 11 – bodies of chrome ores and their numbers.

Download (757KB)
Indexing metadata
4. Fig. 3. Types of chrome ores of the Rai-Iz massif: the Central deposit (a, b, c) and the Engaiskoe-1 ore occurrence (d, e, f). Photo of polished sections. a – densely disseminated, coarse-grained; b – densely disseminated, fine-grained; c – solid, coarse-grained; d – banded, medium-densely disseminated, medium-grained; e – disseminated-banded, medium disseminated, fine-grained; e – wretchedly disseminated fine-grained.

Download (1MB)
Indexing metadata
5. Fig. 4. Types of chrome ores of the Voykar-Syninsky massif: Yambotyvisskoye ore occurrence (a, b, c) and Arkashorskoye (d, e, f). Photo of polished sections. a – medium disseminated, medium-grained; b – porphyritic, densely disseminated fine-grained; c – banded, schlieren-disseminated, medium-grained; d – medium-disseminated, uneven-grained fine-medium-grained; e – schlieren-disseminated, uneven-grained fine-medium-grained; e – medium disseminated, fine-grained.

Download (1MB)
Indexing metadata
6. Fig. 5. The degree of oxidation of iron in spinel, determined using NGR spectroscopy and calculated by converting the composition of the mineral to the stoichiometric formula. On the left are the ore-forming spinels of the Rai-Iz massif, on the right are the Voykar-Synya massif. 1 – chrome spinels of high-chromium and medium-chromium chrome ores, 2 – chrome spinels of aluminous chrome ores.

Download (135KB)
Indexing metadata
7. Fig. 6. Change in the chemical composition of chrome spinel and olivine along the profile through ore bodies No. 48/1 and No. 9; Central deposit. 1–2 chromitites: 1 – densely disseminated, 2 – moderately disseminated; 3 – dunites; 4 – zone of deformation of chrome ores.

Download (706KB)
Indexing metadata
8. Fig. 7. Variations in the chemical composition of ore-forming chrome spinel, T and fO2 along the section through ore body No. 10, Central deposit. Legend: 1–5 chromium ores: 1 – continuous, 2 – densely disseminated, 3 – moderately disseminated, 4 – sparsely disseminated; 5 – ore-bearing dunites; 6 – boreholes and their numbers.

Download (804KB)
Indexing metadata
9. Fig. 8. Variations in the chemical composition of ore-forming chrome spinel, T and fO2 along the section through ore bodies No. 742/1, 742/2, 742/3, Engaiskoe-1 ore occurrence. Legend: 1–3 chrome ores: 1 – moderately disseminated, 2 – sparsely disseminated; 3 – wretchedly interspersed; 4 – ore-bearing dunites; 5 – boreholes and their numbers.

Download (1002KB)
Indexing metadata
10. Fig. 9. Variations in the chemical composition of ore-forming chrome spinel, T and fO2 along the section through ore bodies No. 742/2, 742/3, 742/6, 742/7, Engaiskoye-1 ore occurrence. For symbols, see Fig. 8.

Download (949KB)
Indexing metadata
11. Fig. 10. Changes in the chemical composition of ore-forming spinel, the temperature of olivine-chromium-spinel equilibrium and oxygen fugacity inside chromitite bodies No. 28 and No. 118 of the Yambotyvis area. 1–3 – structure of chromitites based on the content of ore-forming spinel: 1 – continuous, 2 – densely disseminated; 3 – moderately disseminated; 4 – dunites.

Download (902KB)
Indexing metadata
12. Fig. 11. Changes in the chemical composition of ore-forming spinel, the temperature of olivine-chrome-spinel equilibrium and oxygen fugacity inside the body of chromitites No. 346 of the Yambotyvis area. For symbols, see Fig. 10.

Download (480KB)
Indexing metadata
13. Fig. 12. Changes in the chemical composition of ore-forming spinel, the temperature of olivine-spinel equilibrium and oxygen fugacity inside the body of chromitites 3415 of the Arkashor ore occurrence. The red dotted line is a tectonic fault; for other symbols, see Fig. 10.

Download (790KB)
Indexing metadata
14. Fig. 13. Diagram of the relationship between the iron content of olivine and the iron content of spinel. Legend: 1, 2 – Central deposit, 1 – chrome ores, 2 – ore-hosting rocks; 3, 4 – Yengaiskoe-1 ore occurrence, 3 – chrome ores, 4 – ore-hosting rocks; 5, 6 – Yambotyvisskaya area, 5 – chrome ores, 6 – ore-hosting rocks; 7, 8 – chrome ores of the Arkashorskoye ore occurrence, 1 – eastern block, 2 – western block. Lilac field - compositions of minerals from chromitites and ore-hosting ultramafic rocks of the Almaz-Zhemchuzhina deposit, Kempirsay massif, Kazakhstan (after Tsaritsyn, Alimov, 1983).

Download (323KB)
Indexing metadata
15. Fig. 14. Diagram of the composition of the studied ore-forming (left) and accessory (right) chrome-spinels of the Rai-Iz and Voikaro-Syninsky massifs. Legend: a – Central deposit; b – Yengaiskoe-1 ore occurrence; c – Arkashorskoe ore occurrence; d – ore occurrences of the Yambotyvis area. Composition fields according to N.V. classification Pavlova (1949, 1968): 1 – chromite, 2 – subferrichromite, 3 – aluminochromite, 4 – subferrialuminochromite, 5 – ferrialuminochromite, 6 – subaluminumferrichromite, 7 – ferrichromite, 8 – chrompicotite, 9 – subferrichromopicotite.

Download (341KB)
Indexing metadata
16. Fig. 15. Diagram T – log fO2 for chromitites of the Rai-Iz (a) and Voykar-Syninsky (b) massifs. Legend: 1 – Central deposit; 2 – Yengaiskoe-1 ore occurrence; 3 – Arkashor ore occurrence; 4 – ore occurrences of the Yambotyvis area.

Download (482KB)
Indexing metadata
17. Fig. 16. Diagram T –log fO2 for ultramafic rocks of the Central deposit (1) and the Engaiskoe-1 ore occurrence (2).

Download (192KB)
Indexing metadata
18. Fig. 17. Dependence of oxygen fugacity on the density of chrome spinel dissemination in ores of ore body No. 8; Central deposit.

Download (139KB)
Indexing metadata
19. Fig. 18. T – fO2 diagram for chromitites of the Yambotyvis ore occurrence. 1 – poorly and sparsely disseminated; 2 – from moderately disseminated to solid.

Download (139KB)
Indexing metadata

Copyright (c) 2024 Russian Academy of Sciences

This website uses cookies

You consent to our cookies if you continue to use our website.

About Cookies