Structural and magnetic microinhomogeneities in accessory spinel of the system Fe2+(Cr2–xFex3+)O4 from the Kytlym massif (Urals platinum-bearing belt)     

T.A. Sherendo  P.S. Martyshko  V.P. Moloshag  A.A. Garaeva  D.A. Zamyatin  V.Ya. Mitrofanov  L.A. Pamyatnykh 《Russian Geology and Geophysics》2012,53(9):853-860

The microstructure and magnetic properties of accessory Fe–Cr-spinels from the Kytlym massif of the Urals platinum-bearing belt were studied. Atypical Fe–Cr-spinels in the form of magnetic microareas in grains of primary nonmagnetic Fe–Cr-spinel have been revealed for the first time in the bed dunites of the Kytlym multiphase concentrically zoned massif, North Urals. These spinels are responsible for the magnetic properties of the dunites. It has been established that the microareas are separations in solid solution Fe²⁺(Cr_2–xFe_x³⁺)O₄, which are enriched in Fe^3 + and are probably an intermediate product of the transformation of primary accessory Fe-Cr-spinel during the formation of the dunite massif. These are magnetic microphases with particular chemical composition, cation distribution, and corresponding reversed crystal lattice, which determine the main magnetic properties of the microarea: the magnitude and direction of magnetization vector and Curie temperature. The formation of this earlier unknown type of magnetic Fe–Cr-spinel is probably conjugate with the formation and concentration of PGE mineralization in the bed dunites of the Kytlym platinum-bearing massif. The presence of such magnetization carriers in rocks and ores must be taken into account in geophysical research at the Urals chromite and platinum–chromite deposits.  相似文献   

The Unique Sabantuy Chromite Paleoplacer in the Sedimentary Cover of the Eastern European Platform     

Rakhimov  I. R.  Saveliev  D. E.  Kholodnov  V. V.  Zamyatin  D. A. 《Geology of Ore Deposits》2020,62(6):542-546

Geology of Ore Deposits - Abstract—In the section of the sedimentary cover of the East European Platform, the new Sabantuy chromite ore occurrence was revealed. It is localized in Upper...  相似文献   

Chemical U–Th–total Pb dating and structural disorder of monazite-(Ce) from granitoids of the Aduiskii massif,Middle Urals     

D. A. Zamyatin  S. L. Votyakov  G. B. Fershtater  M. D. Vishniakova 《Doklady Earth Sciences》2017,476(1):1033-1037

Using the methods of electron probe microanalysis and Raman spectroscopy, the zoning, chemical composition, and disorder in the matrix of accessory monazite extracted from a synplutonic quartz dioritic dyke intruding migmatite, diorite, and fine-granular granite of the Aduiskii massif were studied. It was established that monazite grains contained inner and outer zones. The contributions of chemical and radiation factors to mineral disorder were estimated. The results of chemical U-Th-total Pb dating of mineral are reported. The age 252 ± 4 Ma corresponds to the second maximum of granite formation.  相似文献   

Chemical dating of zircon from granitic pegmatite of the Shartash Massif (Central Urals)     

S. L. Votyakov  S. V. Pribavkin  D. A. Zamyatin 《Doklady Earth Sciences》2016,470(1):938-941

Using techniques of microprobe analysis and Raman microspectroscopy, a study of the composition, structure, and age of high-uranium zircon from the Sharatash intrusion pegmatite was performed. The presence of a number of zones in crystals having different physicochemical characteristics has been revealed. The Id-e zones affected by a radiation dose of (30–130) × 10¹⁸ α-dec/g were completely amorphized, and their chemical isochron age was estimated at 311.4 ± 7.1 Ma: this is interpreted as the time of zircon formation in the pegmatite. The age of uraninite coupled with zircon is 317.1 ± 2.3 Ma. These dating results clarify the formation time of the final phase (pegmatite) of the Shartash intrusion and determine the upper age limit of hydrothermal gold mineralization (Berezovsk deposit) associated with the granite massif.  相似文献   

On the Structure of Water Exchange Between the Deep Northern and Shelf Southwestern Part of the Kara Sea over the Brusilov Sill     

Kremenetskiy  V. V.  Nedospasov  A. A.  Shchuka  S. A.  Shchuka  A. S.  Zamyatin  I. A.  Bondar  A. V. 《Oceanology》2021,61(6):786-790

Oceanology - During cruise 81 of the R/V Akademik Mstislav Keldysh comprehensive studies of the Kara Sea were carried out over sill separating the central spur of the St. Anna Trough and the Novaya...  相似文献   

Nature of the Clinoenstatite Rim in Refractory Forsterite-Rich Objects from Carbonaceous Chondrites: First Results of Study by the Method of Electron Backscatter Diffraction (EBSD)     

Berzin  S. V.  Koroteev  V. A.  Dugushkina  K. A.  Shilovskikh  V. V.  Zamyatin  D. A.  Stepanov  S. Yu. 《Doklady Earth Sciences》2020,495(1):812-815

Doklady Earth Sciences - A clinoenstatite rim occurs in many refractory forsterite-rich objects; however, specialized studies of it have not been carried out. The first data from the study of...  相似文献   

Features of metamict zircons based on their micrographs and the data of electron microprobe analysis     

S. L. Votyakov  D. A. Zamyatin  Yu. V. Shchapova  A. V. Porotnikov  A. A. Krasnobaev 《Doklady Earth Sciences》2014,457(1):882-886

A new quantitative approach on the basis of joint probability distribution (JPD) analysis of BSE- and CL-images is proposed for studies of the zoning of polygenic (polychronous) grains of zircon. It was shown for the example of zircon of the Mugodzhar metamorphic rocks (South Ural) that a series of zones might be distinguished in the grains of high chemical (structural) heterogeneity. Zones Ia and Ib belong to the fragments of crystalline and radiation-damaged zircon, respectively. Zone II corresponds to the primarily disordered areas (the “genetically metamict” zones) of high concentrations of the impurities of Y, P, REE, U, Hf, etc. The Ia-Ic trend is related to the process of autoradiation metamictization. Based on the data on oxygen content, the declinations of zircon composition from the stoichiometry and the hydration effects were considered.  相似文献   

Composition and Formation Conditions of Neoproterozoic Phosphorites in the Middle Urals     

Krupenin  M. T.  Kuznetsov  A. B.  Zamyatin  D. A.  Pankrushina  E. A.  Lepekha  S. V. 《Lithology and Mineral Resources》2023,58(2):95-121

Lithology and Mineral Resources - Phosphorite breccias compose a 6-m-thick member in the Vendian terrigenous Kernos Formation in the basin of the Mezhevaya Utka and Sylvitsa rivers (Middle Urals)....  相似文献   

Mineralogy, conditions of crystallization and melt generation of epidote-bearing porphyries from the Middle Urals, Russian federation     

Sergey V. Pribavkin  Irina S. Avdonina  Dmitry A. Zamyatin 《Mineralogy and Petrology》2013,107(1):125-147

Epidote-bearing porphyritic dikes (whole rock analysis: SiO₂?=?55–65 wt. %, MgO <2.1 wt. %, K₂O <2.5 wt. %, Al₂O₃ >17 wt. %, Na₂O + K₂O?=?5.7–9.4 wt. %) situated in the continental margin zone, the Middle Urals, Russian Federation have been dated using SHRIMP U-Pb zircon techniques and give a Middle Devonian age of 388?±?2 Ma and 389?±?6 Ma. The porphyries contain phenocrysts of magmatic epidote (Ps?=?17–25 %), Ca- and Mn-rich (CaO >9 wt. %; MnO >6 wt. %) almandine garnet, Al-rich (Al₂O₃?=?12–16 wt. %) amphibole, titanite, plagioclase, biotite, muscovite, apatite, and quartz. 60 to 70 % groundmass of the porphyritic dikes consists of fine-grained albite, quartz, and K-feldspar. A variety of thermobarometric estimations, plus comparison with published experimental data indicate that the phenocryst assemblage was stable between 5 and 11 kbar and 690 to 800 °C. Oxygen fugacity was close to or greater than logfo₂ = Ni-NiO + 1. Later stage formation of the quartz-feldspar groundmass took place at hypabyssal conditions, corresponding to 1 to 2 kbar and 660 to 690 °C. The porphyritic dikes are metaluminous to slightly peraluminous (ACNK?=?0.7–1.17). They are enriched in REE and depleted Nb and Ti. They show features typical of subduction-related magmas. Chemical composition and isotopic ratios of ⁸⁶Sr/⁸⁷Sr_i?=?0.709–0.720 suggest that both mantle- and deep crustal-derived materials were involved in their petrogenesis.  相似文献   

Alteration and chemical U-Th-total Pb dating of heterogeneous high-uranium zircon from a pegmatite from the Aduiskii massif,middle Urals,Russia     

Zamyatin  Dmitry A.  Shchapova  Yuliya V.  Votyakov  Sergey L.  Nasdala  Lutz  Lenz  Christoph 《Mineralogy and Petrology》2017,111(4):475-497

Mineralogy and Petrology - The U-Th-Pb isotope system in the accessory mineral zircon may be disturbed, as for instance by the secondary loss of radiogenic lead. The recognition of such alteration...  相似文献