Formation Conditions of Ferromagnesian Metasomatic Carbonates in the Lower Riphean Terrigenous–Carbonate Rocks of the Southern Urals

New age determinations of detrital zircons of sandstones augmented the possibilities of interpretation of their provenance. This interpretation is often restricted by a formal comparison of age-and-composition characteristics of detrital crystals with any very distant model objects. A different situation arises when the role of a source of a detritus is claimed by local objects. The analysis of SHRIMP and TIMS - datеs of zircons and U and Th concentrations in them, and also a comparison of histograms of primary zircons from Riphean volcanics and rocks of the Taratash complex on one hand and the detrital zircons from the sandstones of Vendian (Asha series) and Lower Riphean (Ai Formation) on the other, have shown that the age variations of sources and clastics are comparable in many aspects. It means that the age characteristics of primary zircons from the Riphean volcanics and rocks of the Taratash complex as sources of zircon clastics for the Riphean and Vendian sandstones in the Southern Urals are regulated by processes of resedimentation, though the influence of distant sources is not excluded.

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Boninitic variolites of the Buribay volcanic complex the Southern Urals: mineralogy, geochemistry and formation conditions

LITOSFERA ◽

10.24930/1681-9004-2018-18-2-246-279 ◽

2018 ◽

Vol 18 (2) ◽

pp. 246-279 ◽

Cited By ~ 1

Author(s):

Aleksandr M. Kosarev ◽

◽

Sergei A. Svetov ◽

Svetlana Yu. Chazhengina ◽

Gul’nara T. Shafigullina ◽

...

Keyword(s):

Southern Urals ◽

Volcanic Complex ◽

The Southern Urals ◽

Formation Conditions

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Polychronous zircons of volcanics of the Navysh complex of the Lower Riphean Ai Formation (Southern Urals)

Georesursy ◽

10.18599/grs.2020.4.101-112 ◽

2020 ◽

Vol 22 (4) ◽

pp. 101-112

Author(s):

Artur A. Krasnobaev ◽

Victor N. Puchkov ◽

Nina D. Sergeeva ◽

Sofia V. Busharina

Keyword(s):

Age Groups ◽

Lower Boundary ◽

Complex Form ◽

Southern Urals ◽

Primary Sources ◽

The Southern Urals ◽

Geochemical Properties ◽

Previous Cycle ◽

Lower Riphean ◽

Frequent Presence

The volcanics of the Navysh complex of the Lower Riphean Ai Formation in the Southern Urals are well studied petrochemically and dated by several methods. In 2013 zircons from a trachybasalt porphyrite (sample 2152) gave a concordant SHRIMP date 1752±11 Ma, which was used as a fundamental for the lower boundary of the Riphean with no special arguments against it. The later attempts to repeat this date for the Navysh volcanics were not successful: the collected zircons were either more ancient (> 2500 Ma), or more young (< 500 Ma). From the beginning, the zircons with such ages were regarded as xenogenic or secondary metasomatic, or belonging to paleozoic dykes intruding the Riphean volcanics. However, the clearly expressed mineralogical properties of the Paleozoic zircons and their frequent presence in volcanics, not dykes, led to a conclusion that the zircons and Navysh volcanics, containing them, and exposed within the area of development of the Ai Formation, are polychronous. To support this conclusion, the authors studied in more detail the zircons of the Navysh trachybasalts, developed in the Ai Formation. The main conclusion, obtained from this new data, was that the volcanics attributed to the Navysh complex, form a polychronous system, including both the Lower Riphean (1750 Ma) and Paleozoic (450 Ma) rocks. The zircons of these age groups differ in their mineralogical and geochemical properties supporting the idea that they belong to different primary sources which may be due to repeating plume processes, which partly reanimated – heated and melted-rocks of the previous cycle and/or created new sources of melts.

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Physicochemical Model of Formation of Gold-Bearing Magnetite-Chlorite-Carbonate Rocks at the Karabash Ultramafic Massif (Southern Urals, Russia)

Minerals ◽

10.3390/min8070306 ◽

2018 ◽

Vol 8 (7) ◽

pp. 306 ◽

Cited By ~ 3

Author(s):

Valery Murzin ◽

Konstantin Chudnenko ◽

Galina Palyanova ◽

Aleksandr Kissin ◽

Dmitry Varlamov

Keyword(s):

Carbon Dioxide ◽

Carbonate Rocks ◽

Southern Urals ◽

Ultramafic Rocks ◽

Physicochemical Model ◽

The Southern Urals ◽

Model Calculations ◽

Ultramafic Massif ◽

Copper Gold ◽

Gold Bearing

We present a physicochemical model for the formation of magnetite-chlorite-carbonate rocks with copper gold in the Karabash ultramafic massif in the Southern Urals, Russia. The model was constructed based on the formation geotectonics of the Karabash massif, features of spatial distribution of metasomatically altered rocks in their central part, geochemical characteristics and mineral composition of altered ultramafic rocks, data on the pressure and temperature conditions of formation, and composition of the ore-forming fluids. Magnetite-chlorite-carbonate rocks were formed by the hydrothermal filling of the free space, whereas chloritolites were formed by the metasomatism of the serpentinites. As the source of the petrogenic and ore components, we considered rocks (serpentinites, gabbro, and limestones), deep magmatogenic fluids, probably mixed with metamorphogenic fluids released during dehydration and deserpentinization of rocks in the lower crust, and meteoric waters. The model supports the involvement of sodium chloride-carbon dioxide fluids extracting ore components (Au, Ag, and Cu) from deep-seated rocks and characterized by the ratio of ore elements corresponding to Clarke values in ultramafic rocks. The model calculations show that copper gold can also be deposited during serpentinization of deep-seated olivine-rich rocks and ore fluids raised by the tectonic flow to a higher hypsometric level. The results of our research allow predicting copper gold-rich ore occurrences in ultramafic massifs.

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Zircons of the Permian age (280–290 Ma) from intrusive magmatic rocks in Riphean structure of the Southern Urals

LITOSFERA ◽

10.24930/1681-9004-2021-21-5-601-608 ◽

2021 ◽

Vol 21 (5) ◽

pp. 601-608

Author(s):

A. A. Krasnobaev ◽

V. N. Puchkov ◽

N. D. Sergeeva ◽

S. V. Busharina

Keyword(s):

Southern Urals ◽

Lower Permian ◽

The Urals ◽

Shrimp Dating ◽

The Southern Urals ◽

Lower Paleozoic ◽

Magmatic Rocks ◽

Lower Riphean ◽

Granite Complex ◽

A Chain

Research subject. Magmatic complexes that are developed in the lower (volcanogenic-sedimentary) part of the Ai Formation of the Lower Riphean of the Taratash anticline in the Southern Urals. Results. For the frst time, the Lower Permian SHRIMP dating (288.6 ± 3.1 Ma by U-Pb method on zircon from monzogabbro) was obtained for a dike cutting the basalts of the Lower Paleozoic (420–450 Ma) age. Conclusions. On the eastern slope of the Urals there is a chain of massifs which are close in the age. The chain belongs to the Lower Permian Stepninsky monzogabbro-granosyenite-granite complex, represented by the Uiski, Vandyshevski, Biryukovski and Stepninski intrusions with the age of 281 ± 2, 280 ± 2 and 286 ± 2 Ma, correspondingly (U-Pb method after zircons, SHRIMP-II, VSEGEI) and earlier obtained dates 281 ± 4 Ma (Rb-Sr isochrone) and 283 ± 2 Ma (isotope Pb-Pb method after zircons). The Stepninsky complex was described earlier as plume-dependent. The monzogabbro dike, described in this paper, although being at a considerable distance from the Sepninsky complex, is situated at a strike of the chain of the stepninsky intrusions, is close to them by the composition and age and can be ascribed to the same plume episode. The idea of the plume character of the complex was ехрressed by us relatively long ago based on a superimposed character of the chain of the intrusions over the earlier, collisional Uralian structures. As for the geochemical character (monzogabbro) the dike conforms with one of two standard trends of the Stepninsky complex – monzonite (monzogabbro, monzodiorites, syenites).

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The Lower Precambrian in the structure of paleozoic in the Subpolar Urals

Доклады Академии наук ◽

10.31857/s0869-56524865572-576 ◽

2019 ◽

Vol 486 (5) ◽

pp. 572-576

Author(s):

Yu. I. Pystina ◽

A. M. Pystin ◽

V. B. Hubanov

Keyword(s):

Southern Urals ◽

Western Slope ◽

Geochronological Data ◽

The Urals ◽

The Southern Urals ◽

Early Precambrian ◽

Subpolar Urals ◽

Late Precambrian ◽

Lower Riphean ◽

First Time

In many polymetamorphic complexes of the Urals, rocks with Early Precambrian age marks have been established. But only with respect to the two polymetamorphic complexes located on the western slope of the Southern Urals: the Taratash and Aleksandrov, their indisputable belonging to the Archean-Paleoproterozoic section is recognized. They are framed by weakly metamorphosed Lower Riphean sediments and reliable geochronological data are obtained from them, which unambiguously indicate the Early Precambrian age of rock metamorphism. The available Early Precambrian age datings for other Ural polymetamorphic complexes (with the prevailing number of Late Precambrian and Paleozoic age values) are interpreted differently. Therefore, their attitude to the Lower Precambrian section has been disputed by many researchers. In the article, for the first time, based on the results of mass U-Pb dating of metamorphic zircons from the gneiss of the Nyrtin polymetamorphic complex of the Subpolar Urals, taking into account the available data, the Paleoproterozoic age of the earliest stage of rocks metamorphism (2127 ± 31 Ma) is substantiated. This gives grounds to assert that the complex under consideration, as well as the Taratash and Alexandrov complexes of the Southern Urals, belongs to the Lower Precambrian formations involved in the structure of Uralides.

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Diagenesis of Carbonate and Siderite Deposits of the Lower Riphean Bakal Formation, the Southern Urals: Sr Isotopic Characteristics and Pb-Pb Age

Lithology and Mineral Resources ◽

10.1007/s10987-005-0022-z ◽

2005 ◽

Vol 40 (3) ◽

pp. 195-215 ◽

Cited By ~ 35

Author(s):

A. B. Kuznetsov ◽

M. T. Krupenin ◽

G. V. Ovchinnikova ◽

I. M. Gorokhov ◽

A. V. Maslov ◽

...

Keyword(s):

Southern Urals ◽

The Southern Urals ◽

Lower Riphean

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Comparison of Lower and Middle Riphean sparry magnesite deposits of the Southern Urals province

Boletim Paranaense de Geociências ◽

10.5380/geo.v50i0.4156 ◽

2002 ◽

Vol 50 ◽

Author(s):

MIKHAIL T. KRUPENIN

Keyword(s):

Southern Urals ◽

Ultramafic Rocks ◽

Western Slope ◽

South Urals ◽

The Southern Urals ◽

Humid Climate ◽

Ore Formation ◽

Ore Body ◽

Lower Riphean ◽

Average Size

Sparry magnesite deposits (SMD) of the Lower Riphean (LR) and Middle Riphean (MR) sequences in the western slope of the South Urals have some distinguished peculiarities, which allows to compare them and speculate about the mechanism of ore formation and Mg-source origin. LR magnesites are located in some stratigraphic levels and lie within widespread dolostone horizons. MR magnesites that occur in the lower carbonate member of Avzyan fm. are represented by dolomitized limestones. The shape of LR magnesite body is very often layer-like with sharp contacts. The shape of MR one is sometimes lens like, contacts of ore body are complecated with zones of impregnable magnesites near the hosting dolomites. The crystalline structures of LR magnesites are typically corse-grained with average size of crystalls 10 mm. The magnesite grains of the MR one have 1-3 mm of average size. The chemical composition of MR magnesite ore shows increase of SiO 2 , Al 2 O 3 , FeO and decrease of LREE fractionation in comparison with the LR magnesites. As we assume, metasomatic magnesites of the Lower Riphean time are connected with sedimentation/early diagenesis stage. The source of Mg 2+ came from a crust of weathering of basic and ultramafic rocks in humid climate. Magnesite occurrences in Middle Riphean time are connected with high Fe-contents metasomatic fluids, which were resulted of evaporite Mg-enriched solutions transformation during kathagenesis.

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