Geologicheskii Vestnik

The mineralogical features of several samples of gabbroids from the eastern part of the Mindyak mafic-ultramafic massif have been studied. The compositions of rock-forming and accessory minerals are given. The rocks underwent autometamorphic transformations with the replacement of the primary pyroxene-plagioclase association to amphibole and essentially sodium feldspar secondary assemblage. Typical accessory minerals are titanite, ilmenite, titanomagnetite, and apatite. The gabbroids of the massif cover a wide range of compositions from melanogabbro to diorites, also demonstrating significant variations in the contents of petrogenic oxides and trace elements. In terms of REE distribution, most of the studied samples of gabbroids are comparable to basalts of mid-ocean ridges, but often differ from them in high concentrations of strontium and some other rare elements. The gabbroids of the eastern part of the massif have U-Th mineralization in association with aggregates of xenomorphic zircon grains. The origin of these finds has not been established in the present study. Estimates of the PT conditions by the amphibole barometer show the presence of two maxima of values — 2.8–5.1 kbar and less than 2 kbar, which most likely fix two different stages in the formation of rocks — autometamorphism in the magma chamber during cooling and interaction with magmatic fluids (magnesian hornblende), and low-temperature (greenstone) transformations (actinolite).

gabbro, amphibole, apatite, thorite, Mindyak mafic-ultramafic massif, the Southern Urals

• Anderson J.L., Smith D.R. (1995). The effects of temperature and fO2 on the Al-in-hornblende barometer // American Mineralogist. V. 80. P. 549–559.
• Denisova E.A. (1984). Internal structure of Mindyak ultrabasic massif (the Southern Urals) // Doklady of Earth Science. V. 274. Is. 2. P. 382–387. (in Russian).
• Gottman I.A., Poushkarov Ye.V., Khiller V.V. (2015). U-Zr-Ti-assotsiatsiya mineralov v vysokobaricheskikh granatovykh porodakh Mindyakskogo massiva (Yuzhnyy Ural) [U-Zr-Ti-association of minerals in high-pressure garnet rocks of the Mindyak massif (Southern Urals)]. Yezhegodnik-2014 — Yearbook-2014. V. 162. IGG UB RAS Publ., 155–158 p. (In Russian).
• Gottman I.A., Pushkarev E.V., Khiller V.V. (2018). Uranium-Bearing Srilankite from High-Pressure Garnetites of the Southern Urals: First Data. Doklady Earth Sciences, V. 479. Part 2. P. 529–533. https://doi.org/10.1134/S1028334X18040244
• Gottman I. A., Pushkarev E.V., Khiller V.V. (2018). Uranium-Bearing Srilankite from High-Pressure Garnetites of the Southern Urals: First Data // Doklady Earth Sciences. V. 479. Part 2. P. 529–533. https://doi.org/10.1134/S1028334X18040244
• Gottman I.A., Pushkarev Ye.V., Glavatskikh S.P. (2013). Kimrit iz vysokobaricheskikh granatitov Mindyakskogo massiva na Yuzhnom Urale [Kimrite from high-pressure garnetites of the Mindyak massif in the Southern Urals]. Vestnik Ural’skogo otdeleniya Rossiyskogo Mineralogicheskogo obshchestva № 10 — Bulletin of the Ural Branch of the Russian Mineralogical Society. №10. Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences, 17–20 p. (In Russian).
• Hammarstrom J.M., Zen E-an. (1986). Aluminum in hornblende: An empirical igneous geobarometer // American Mineralogist. V. 71. P. 1297–1313.
• Kosarev A.M. (2013). Osobennosti raspredeleniya MgO, K2O i TiO2 i nekotorykh mikroelementov v bazal’takh okeanov, kontinentov i rannepaleozoyskikh paleovulkanicheskikh poyasov Yuzhnogo Urala [Features of the distribution of MgO, K2O and TiO2 and some trace elements in basalts of the oceans, continents and early Paleozoic paleovolcanic belts of the Southern Urals]. Geologicheskiy sbornik №10. Informatsionnye materialy — Geologicheskiy sbornik №10. Informatsionnyye materialy. Institut geologii UNC RAS, Ufa, Russia, 143–154 p. (In Russian).
• Kosarev A.M. (2015). Geologiya i geokhimicheskie osobennosti rannepaleozoyskikh vulkanitov Samarskiy i Voznesenskoye-Prisakmarskoy zon na Yuzhnom Urale [Geology and geochemical features of the Early Paleozoic volcanic rocks of the Sakmara and Voznesenskoye-Samara zones in the Southern Urals]. Litosfera, No 2. Institut geologii UNC RAS, Ufa, Russia, 40–64 p. (In Russian).
• Krasnobayev A.A., Rusin A.I., Rusin I.A., Busharina S.V. (2011). Tsirkony, tsirkonovaya geokhronologiya i voprosy petrogenezisa lertsolitovykh massivov Yuzhnogo Urala [Zircons, zircon geochronology and issues of petrogenesis of lherzolite massifs of the Southern Urals]. Geochemistry, №5. P. 506–522. (In Russian).
• Kuznetsov D.V. (2017). Izmereniya khimicheskogo sostava mineralov olivin-shpinel’ — piropovykh vebsteritov Mindyakskogo massiva kak otrazheniye evolyutsii etikh porod [Changes in the chemical composition of minerals in olivine-spinal-pyrope websterites of the Mindyak massif as a reflection of the evolution of these rocks]. Yezhegodnik-2016 — Yearbook-2016. V. 164. IGG UB RAS Publ., 214–218 p. (In Russian).
• Kuznetsov D.V., Pushkarev Ye.V., Gottman I.A. (2014). Sostav khromshpinelidov iz olivin-shpinel’ — piropovykh vebsteritov Mindyakskogo massiva [Composition of Cr-spinels from olivine-spinel-pyrope websterites of the Mindyak massif]. Yezhegodnik-2013 — Yearbook-2013. V. 161. IGG UB RAS Publ., 274–278 p. (In Russian).
• Leake B.E., Woolley A.R., Arps C.E.S., Birch W.D., Gilbert M.C., Grice J.D., Hawthorne W.C., Kato A., Kisch K.J., Krivovichev V. G., Lithout K., Laird J., Mandarino J. A., Maresch W.V., Nickel E.A., Rock N.M.S., Schumacher J.C., Smith D.C., Stephenson N.C. N., Ungaretti L., Whittaker E.J. W., Youzhi G. (1997). Nomenclature of amphiboles. Report of the Subcommittee on amphiboles of the International Mineralogical Association Commission on New Minerals and Mineral Names // European Journal of Mineralogy. V. 9. P. 623–651.
• Morimoto N. (1989). Nomenclature of pyroxenes // Canadian mineralogist. V. 27. P. 143–156.
• Pushkarev E.V., Ryazantsev A.V., Tretyakov A.A., Belova A.A., Gottman I.A. (2010). Granatovyye ul’tramafity i mavity v zone Glavnogo Ural’skogo razloma na Yuzhnom Urale: petrologiya, vozrast problema obrazovaniya [Garnet ultramafic and mafic rocks in the zone of the Main Ural Fault in the Southern Urals: petrology, age and problem of formation]. Lithosphere, №5. P. 101–133. (In Russian).
• Salikhov D.N. (2008). Ofiolity i orudeneniye v zone nablyudeniya Glavnogo Ural’skogo razloma [Ophiolites and mineralization in the observation zone of the Main Ural fault]. Geologicheskiy sbornik. Yubileynyy vypusk — Geological collection. Anniversary issue. (№7), UNC RAS Publ., Ufa,
  Russia, 126–134 p. (In Russian).
• Salikhov D.N., Belikova G.I. (2007). Gabbroidy zony melanzha Glavnogo Ural’skogo razloma [Gabbroids of the melange zone of the Main Ural fault]. Geologicheskiy sbornik. Informatsionnyye materialy — Geological collection. Information materials. (№6), UNC RAS Publ., Ufa, Russia, 106–125 p. (In Russian).
• Saveliev D.E., Gataullin R.A., Gayfullin R.Yu. (2022). Mineralogo-geokhimicheskiye osobennosti I usloviya obrazovaniya ultramafitov Mindyakskogo massiva (Yuzhnyy Ural) [Mineralogigal and geochemical features of formation of Mindyak ultramafic massif (the Southern Urals)] // Herald of the Academy of Sciences of the Republic of Bashkortostan. V. 42. Is. 1 (105). P. 47–57. DOI: 10.24412/1728-5283_2022_1_47_57
• Savelieva G.N., Sharaskin A.Ya., Saveliev A.A., Spadea P., Gaggero L. (1997). Ophiolites of the southern Uralides adjacent to the East European continental margin // Tectonophysics. V. 276. P. 117–137.
• Scarrow J.H., Savelieva G.N., Glodny J., Montero P., Pertsev A.N., Cortesogno L., Gaggero L. (1999). The Mindyak palaeozoic lherzolite ophiolite, Southern Urals: geochemistry and geochronology // Ofioliti. V. 24. №2. P. 239–246.
• Scarrow J.H., Spadea P., Cortesogno L., Savelieva G.N., Gaggero L. (2000). Geochemistry of garnet metagabbros from the Mindyak ophiolite massif Southern Urals // Ofioliti. V. 25. №2. P. 103–115.
• Schmidt M.W. (1992). Amphibole composition in tonalite as a function of pressure: An experimental calibration of the AI-in-hornblende barometer // Contributions to Mineralogy and Petrology. V. 110. P. 304–310.
• Seravkin I.B., Znamensky S.E., Kosarev A.M. (2001). Razryvnaya tektonika I rudonosnost’ Bashkirskogo Zaural’ya [Crack tectonic and ore-bearing of Bashkirian Zauralye]. Ufa: Poligrafkombinat. 318 p. (In Russian).
• Spadea P., D’Antonio M. (2006). Initiation and evolution of intra-oceanic subduction in the Uralides: Geochemical and isotopic constraints from Devonian oceanic rocks of the Southern Urals, Russia // Island Arc, V. 15. P. 7–25.
• Tessalina S.G., Gannoun A., Bourdon B., Capmas F., Garuti G., Pushkarev E.V., OrgevalJ.J., Birck J.L., Allegre C.J. (2003). Ocean crust formation age in the Southern Urals: example of the Mindyak ophiolite complex // Conference: EGS-AGU-EUG Joint Assembly, 6–11 April 2003At: Nice,
  FranceVolume.
• Tessalina S.G., Bourdon B., Gannoun A., Capmas F., Birck J.L., Allègre C.J. (2007). Complex proterozoic to paleozoic history of the upper mantle recorded in the Urals lherzolite massifs by Re-Os and Sm-Nd systematics// Chemical Geology, V. 240. P. 61–84.
• Whitney D.L., Evans B.W. (2010). Abbreviations for names of rock-forming minerals // American Mineralogist. V. 95. P. 185–187.
• Znamensky S.E. (2009). Strukturnye usloviya formirovaniya kollizionnykh mestorozhdeniy zolota vostochnogo sklona Yuzhnogo Urala [Structural conditions of formation of orogenic Au deposits on the east slope of the Southern Urals]. Ufa: Gilem. 348 p.