The timing and extent of the eruption of the Siberian Traps large igneous province: Implications for the end-Permian environmental crisis     

Marc K. Reichow  M.S. Pringle  A.I. Al'Mukhamedov  M.B. Allen  V.L. Andreichev  M.M. Buslov  C.E. Davies  G.S. Fedoseev  J.G. Fitton  S. Inger  A.Ya. Medvedev  C. Mitchell  V.N. Puchkov  I.Yu. Safonova  R.A. Scott  A.D. Saunders 《Earth and Planetary Science Letters》2009,277(1-2):9-20

We present new high-precision ⁴⁰Ar/³⁹Ar ages on feldspar and biotite separates to establish the age, duration and extent of the larger Siberian Traps volcanic province. Samples include basalts and gabbros from Noril'sk, the Lower Tunguska area on the Siberian craton, the Taimyr Peninsula, the Kuznetsk Basin, Vorkuta in the Polar Urals, and from Chelyabinsk in the southern Urals. Most of the ages, except for those from Chelyabinsk, are indistinguishable from those found at Noril'sk. Cessation of activity at Noril'sk is constrained by a ⁴⁰Ar/³⁹Ar age of 250.3 ± 1.1 Ma for the uppermost Kumginsky Suite.The new ⁴⁰Ar/³⁹Ar data confirm that the bulk of Siberian volcanism occurred at 250 Ma during a period of less than 2 Ma, extending over an area of up to 5 million km². The resolution of the data allows us to confidently conclude that the main stage of volcanism either immediately predates, or is synchronous with, the end-Permian mass extinction, further strengthening an association between volcanism and the end-Permian crisis. A sanidine age of 249.25 ± 0.14 Ma from Bed 28 tuff at the global section and stratotype at Meishan, China, allows us to bracket the P–Tr boundary to 0.58 ± 0.21 myr, and enables a direct comparison between the ⁴⁰Ar/³⁹Ar age of the Traps and the Permo–Triassic boundary section.Younger ages (243 Ma) obtained for basalts from Chelyabinsk indicate that volcanism in at least the southern part of the province continued into the Triassic.  相似文献   

Bashkirian Sr-Nd age of the terminal stage of collisional magmatism in the Western Magnitogorsk zone of the South Urals     

I. R. Rakhimov  D. N. Salikhov  V. N. Puchkov  Yu. L. Ronkin  V. V. Kholodnov 《Doklady Earth Sciences》2014,457(2):921-925

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Mineralogy,U–Pb (TIMS,SHRIMP) age,and rare-earth elements in zircons from granites of the Mazara Massif,South Urals     

A. A. Krasnobaev  V. N. Puchkov  N. D. Sergeeva  S. V. Busharina 《Geochemistry International》2017,55(6):521-534

The paper reports the results of mineralogical, geochemical, and geochronological (TIMS and SHRIMP) study of heterogeneous zircons from granites of the Mazara Massif, South Urals. Obtained data revealed the Mesoproterozoic age (1550–1390 Ma) of a granite protolith and the Neoproterozoic age of their formation (745–710 Ma). In the La–Sm/La diagram, the zircons of the massif occupy an intermediate position between the fields of magmatic and metasomatic (hydrothermal) zircons. This “intermediate” field is proposed to ascribe to the late magmatic zircons, which provides more reliable characterization of zircon formation throughout the entire crystallization history of a granite melt, up to the appearance of genetically metamict metasomatic hydrozircons.  相似文献   

Polychronous zirconology of syenites from the Avashla intrusion in the Kurgass anticline (Southern Urals)     

A. A. Krasnobaev  V. N. Puchkov  N. D. Sergeeva  S. P. Shokalski  S. V. Busharina 《Doklady Earth Sciences》2017,473(1):323-328

Zircons were separated from syenites of the Avashla intrusion in the Kurgass anticline of the Bashkir megaanticlinorium in the Southern Urals. The obtained samples were dated using the U–Pb procedure by means of a SHRIMP II ion microprobe. The integrated mineralogical, geochemical, and isotope studies of zircons resulted in primary data on the origin and current conditions of zircons in syenites of the Avashla intrusion. The relics of early zircon generations (1320–1340 Ma) allowed us to specify the geological position of syenites along with the stratigraphic location of the enclosing sedimentary rocks. The time of the transformation (metamorphism) of the zircons at the Middle–Upper Riphean boundary is represented by a dating of 1097±20 Ma, which is of importance for specifying the boundary age and for revealing a geological event that started a new development stage of the stratoregion in the Upper Riphean.  相似文献   

The first finds of paragenetic Th–REE mineralization in precambrian rocks of the Shatak complex (Southern Urals)     

S. G. Kovalev  S. I. Vysotsky  V. N. Puchkov 《Doklady Earth Sciences》2017,476(2):1181-1186

Detailed characterization of Th–REE mineralization confined to terrigenous deposits of the Shatak complex is presented. For the first time the veinlet xenotime mineralization, unknown in the scientific literature, as well as diverse unidentified Th–REE compounds of variable composition were described in terrigenous deposits. It was concluded that permanent Th and REE admixtures and rare-earth minerals and thorite, respectively, as well as the occurrence of paragenetic intergrowths of Th and REE minerals of variable composition, are evidence that Th–REE mineralization crystallized as a result of the influence of the fluid phase on the sedimentary substrate upon magmatic melt intrusion into the frame rocks. The superimposed dynamothermal greenschist-facies metamorphism led to decay of metastable Th–REE phases without affecting significantly the redistribution of thorium and rare earth elements.  相似文献   

Geodynamic conditions of formation of massive sulfide deposits in the Magnitogorsk Megazone,Southern Urals,and prospection criteria     

I.?B.?SeravkinEmail author  A.?M.?Kosarev  V.?N.?Puchkov 《Geology of Ore Deposits》2017,59(3):227-243

The zoned composition changes of the massive sulfide deposits in the major massive sulfide zone of the Southern Urals such as the Magnitogorsk Megasynclinorium are considered. The zoning is expressed as the trend of Ni–Co–Cu → Zn–Cu → Cu–Zn → Au–Ba–Pb–Cu–Zn. This trend is related to two basic factors: (1) the subduction process with the slab’s eastward subsidence preconditioned the formation (from the west to the east) of the following massive sulfide zones: accretionary prism, frontal island arc, developed island arc, inter-arc spreading zone, split back arc, and back-arc spreading; (2) the longitudinal zoning of the massive sulfide paleovolcanic belts related to changes in the thickness of the crust’s basaltic layer and an inclination of the subducting plate in transverse blocks of the belt. The first factor affects the general paleovolcanic and metallogenic latitudinal zoning of the studied region, while the second factor defines the local meridional zoning. The composition of ore-bearing solutions is dependent on the formation depth of the subduction fluids, magma differentiation type, and the ratio of deep fluids to solutions of near-surface convective cells. The combination of the geodynamic factors expressed in the composition of ore-bearing volcanic complexes and the specific geological settings defines the massive sulfide mineralization composition and productivity criteria. The most productive structures include the frontal island-arc and inter-arc spreading zones and within them, the central-type volcanic edifices whose basalts are referred to as the island-arc tholeiite series and are characterized by the minimum TiO₂ and Zr content and low La/Yb ratios.  相似文献   

Incipient metamorphism between Ufa and Beloretzk, western fold-and-thrust belt, southern Urals, Russia     

I. Matenaar  U. A. Glasmacher  W. Pickel  U. Giese  V. N. Pazukhin  V. I. Kozlov  V. N. Puchkov  L. Stroink  R. Walter 《International Journal of Earth Sciences》1999,87(4):545-560

The low-temperature thermal history of Paleozoic and Precambrian shales and slates was studied in detail along a NW–SE transect between Ufa and Beloretzk in the western fold-and-thrust belt of the southern Urals, Russia. The aim of the investigations was to compare four thermal parameters, namely illite and chlorite crystallinity, vitrinite reflectance, and Conodont color alteration index (CAI), in order to quantify the finite (i.e. maximum) thermal grade. The transect extends from Devonian to Permian sedimentary units of the pre-Uralian foredeep, crossing Precambrian siliciclastic and carbonate units of the Bashkirian megaanticlinorium into the Paleozoic units of the Ural-Tau antiform. In general, the four methods indicate similar metamorphic grades of the samples. The finite thermal grade ranges from lower diagenesis (R_o=0.9%, CIS-FWHM_ill001ad=0.770 Δ°2Θ, CIS-FWHM_chl002ad=0.447 Δ°2Θ, CAI=1.5) in the pre-Uralian foredeep to epizone (CIS-FWHM_ill001ad=0.243 Δ°2Θ, CIS-FWHM_chl002ad=0.252 Δ°2Θ, CAI=6) in the eastern part of the Bashkirian mega-anticlinorium and the Zilair synclinorium. All parameters show a sudden change in value at thrust boundaries and an increase in metamorphic grade with stratigraphic age within structural units. In comparison, the westernmost Precambrian units of the Ala-Tau-anticlinorium are characterized by thermal grades of lower diagenesis. Magmatic dikes cause a wide variation of the thermal grade in the western part of the Bashkirian megaanticlinorium. Also in areas with an intensive cleavage development (Zilair synclinorium) the finite thermal grade shows a stronger relationship towards the deformation than the stratigraphic position.  相似文献   

Transverse (Sublatitudinal) Zonality of the Urals: Causes and Time of Occurrence     

Ivanov  K. S.  Puchkov  V. N. 《Doklady Earth Sciences》2022,504(2):344-348

Doklady Earth Sciences - It is shown that the observed latitudinal zonality of the Ural Fold Belt is determined mainly by the different levels of erosion of different areas. Thus, the deep levels...  相似文献