Geochemistry and age of ultrahigh pressure metamorphic rocks from the Kokchetav massif (Northern Kazakhstan)     

V. S. Shatsky  E. Jagoutz  N. V. Sobolev  O. A. Kozmenko  V. S. Parkhomenko  M. Troesch 《Contributions to Mineralogy and Petrology》1999,137(3):185-205

Isotopic and geochemical data of the Zerenda series metamorphic rocks from the Kokchetav massif are reported. Some of these rocks contain microdiamond inclusions in garnets and other indicators of ultrahigh pressure metamorphism (P > 40 kbar, T = 900–1000 °C). The diamond-bearing rocks exhibit distinctive geochemical characteristics compared to typical crustal rocks. The REE patterns range from LREE depleted to slightly LREE enriched [chondrite normalized (La/Yb)_N– 0.1–5.4] with a negative Eu anomaly. They are depleted in incompatible elements (e.g. Sr, Ba, U, Th) with respect to the upper crust. In contrast non-diamondiferous rocks of the Zerenda series exhibit normal crustal geochemistry. All rocks of the Zerenda series have very radiogenic lead isotopes. The measured μ values (²³⁸U/²⁰⁴Pb) compared with those calculated for the interval between crust formation and ultrahigh pressure (UHP) metamorphism suggest a decrease by factors of up to 200 during the UHP metamorphism. The Sm-Nd mineral isochrons from the diamond-bearing rocks and other rock types of the Zerenda series give a Middle Cambrian (524–535 Ma) age of metamorphism. The Nd model ages show that crust formation occurred about 2.3 Ga ago. Significant fractionation of Sm and Nd and loss of incompatible elements may be due to partial melting of the protoliths. The Ar-Ar age determinations of secondary biotite and muscovite from the diamond-bearing rocks yield an age of 517 ± 5 Ma. This cooling age requires a short time interval between UHP metamorphism and uplift to a crustal level. Ultrahigh pressure metamorphism might be a significant source of Pb for the mantle. We propose that the radiogenic Pb of the oceanic array is the contamination traces of numerous UHP events. Beside the geological aspect we demonstrate a method of dating a high grade metamorphic terrain using Nd isotopes. We compare whole rock isochrons and mineral isochrons and in this way get some insight into the behaviour of the Sm-Nd system during very high grade metamorphic events. Received: 14 August 1998 / Accepted: 1 June 1999  相似文献   

New FTIR spectroscopy data on the composition of the medium of diamond crystallization in metamorphic rocks of the Kokchetav Massif     

E.S. Sitnikova  V.S. Shatsky 《Russian Geology and Geophysics》2009,50(10):842-849

A representative sample of microdiamonds in calc-silicate and garnet-pyroxene-quartz rocks and gneisses from the cross section of an adit driven at the Kumdy-Kol’ deposit (Northern Kazakhstan) has been analyzed. Microdiamonds from these rocks were studied by Fourier-transform infrared spectroscopy for the first time. It has been established that nitrogen impurity content (300–3000 ppm) and nitrogen aggregation degree (14–75%) vary widely and do not correlate with each other. The variation is probably due to the uneven distribution of nitrogen in crystals and to their specific internal structures.The results of the study show that in most diamondiferous rocks, diamonds crystallized from a fluid/melt of composition varying between aqueous-carbonate and aqueous-silicate end-members. Spectroscopy studies partly disagree with literature data on individual nanoinclusions in diamonds. The cause of this discrepancy may be the evolution of the fluid/melt during diamond crystallization.  相似文献   

Two contrasting petrotectonic domains in the Kokchetav megamélange (north Kazakhstan): Difference in exhumation mechanisms of ultrahigh‐pressure crustal rocks,or a result of subsequent deformation?     

K. Theunissen  N. L. Dobretsov  A. Korsakov  A. Travin  V. S. Shatsky  L. Smirnova and  A. Boven 《Island Arc》2000,9(3):284-303

Abstract In northern Kazakhstan the WNW striking Kokchetav megamélange includes different crustal sequences with high‐pressure/ultrahigh‐pressure (HP/UHP) remnants of their 540–520 Ma subduction metamorphism. Two domains separated by the north‐east trending Chaglinka fault are distinguished. The western domain exhibits NE–SW structures within a single Kumdy–Kol megaunit of diamond‐bearing UHP metasediments and high‐temperature (HT) eclogites. The eastern domain consists of the composite Kulet megaunit with the Kulet UHP unit (coesite‐bearing metasediments, whiteschists and eclogites), the Enbek–Berlyk medium‐pressure (MP) unit (kyanite‐bearing, high‐alumina rocks with interleaved coronitic metagabbro), and ortho‐ and paragneisses with eclogites and amphibolites included. All eclogites in the eastern domain are of the relatively low temperature (LT) type. Sillimanite is common and appears after kyanite in the sheared MP unit. A regional and moderately ESE plunging linear fabric coincides with the fold‐axis of the foliation poles from the eastern domain. Whether this also reflects a regional top to the WNW transport, as inferred from the dextral strike‐slip on steeply to SSW dipping foliation, needs further study. Top to the WNW shear is shown by weakly inclined low pressure (LP) cordierite rocks that flank the eastern domain in the south. Some new ³⁹Ar/⁴⁰Ar mica cooling ages (519, 521 Ma) from the Kulet UHP micaschists reflect the same early stage evolutionary event as was previously shown for the Kumdy–Kol UHP rocks (515, 517 Ma) in the west. Similar ³⁹Ar/⁴⁰Ar ages (500, 517 Ma) are recorded by micas and amphibole that outline a top to NNW shear fabric in the non‐subducted Proterozoic basement, north of the megamélange. A 447 Ma overprint of the MP sequences is considered to reflect the strike‐slip deformation with sillimanite and the reworking of an early kyanite‐bearing tectonite. Biotites from the LP cordierite rocks yielded approximately 400 Ma ³⁹Ar/⁴⁰Ar ages. In case they reflect the WNW shear deformation, the latter is considered to be associated with a regional granite magmatism (420–460 Ma) extending south of the eastern domain. In their present different structural domains the Kulet and Kumdy–Kol UHP units display a similar early stage event. Subsequent LP deformation, which is likely to be associated with regional granite magmatism (420–460 Ma), is assumed to have obliterated any common or uniform early exhumation structure for the whole megamélange. The north‐east structured Kumdy–Kol domain is assumed to have preserved the most information about the early stage exhumation. This domain is at an angle to the regional WNW strike of the megamélange.  相似文献   

Homogenization of carbonate-bearing microinclusions in diamond at <Emphasis Type="Italic">P</Emphasis>–<Emphasis Type="Italic">T</Emphasis> parameters of the upper mantle     

A. L. Ragozin  Yu. N. Palyanov  D. A. Zedgenizov  A. A. Kalinin  V. S. Shatsky 《Doklady Earth Sciences》2016,470(2):1042-1045

The staged high-pressure annealing of natural cubic diamonds with numerous melt microinclusions from the Internatsional’naya kimberlite pipe was studied experimentally. The results mainly show that the carbonate phases, the daughter phases in partially crystallized microinclusions in diamonds, may undergo phase transformations under the mantle P–T conditions. Most likely, partial melting and further dissolution of dolomite in the carbonate–silicate melt (homogenization of inclusions) occur in inclusions. The experimental data on the staged high-pressure annealing of diamonds with melt microinclusions allow us to estimate the temperature of their homogenization as 1400–1500°C. Thus, cubic diamonds from the Internatsional’naya pipe could have been formed under quite high temperatures corresponding to the lithosphere/asthenosphere boundary. However, it should be noted that the effect of selective capture of inclusions with partial loss of volatiles in relation to the composition of the crystallization medium is not excluded during the growth. This may increase the temperature of their homogenization significantly between 1400 and 1500°C.  相似文献   

Measurements of optical turbulence in the free atmosphere above Mount Maidanak in 2005–2007     

V. Kornilov  S. Ilyasov  O. Vozyakova  Yu. Tillaev  B. Safonov  M. Ibragimov  N. Shatsky  Sh. Egamberdiev 《Astronomy Letters》2009,35(8):547-554

We present the results of our 2005–2007 campaign to measure the vertical distribution of optical turbulence above Mount Maidanak. The measurements were performed with the MASS instrument, a multi-aperture scintillation sensor that has been widely used for such studies in recent years at many observatories worldwide. Analysis of the data shows that the median seeing in the free atmosphere (at an altitude of 0.5 km and higher) is 0 ″46, while the isoplanatic angle is 2″.47. Given the large time constant (about 7 ms at good seeing), such conditions are favorable for using adaptive optics and interferometric measurements in the visible and near-infrared spectral ranges.  相似文献   

Light Curves of the Type II-P Supernova SN 2017eaw: The First 200 Days     

D.?Yu.?TsvetkovEmail author  S.?Yu.?Shugarov  I.?M.?Volkov  N.?N.?Pavlyuk  O.?V.?Vozyakova  N.?I.?Shatsky  A.?A.?Nikiforova  I.?S.?Troitsky  Yu.?V.?Troitskaya  P.?V.?Baklanov 《Astronomy Letters》2018,44(5):315-323

We present the results of our UBVRI photometry for the type II-P supernova SN 2017eaw in NGC6946 obtained fromMay 14 to December 7, 2017, at several telescopes, including the 2.5-m telescope at the CaucasusHigh-Altitude Observatory of the SAIMSU. The dates andmagnitudes atmaximumlight and the light-curve parameters have been determined. The color evolution, extinction, and peak luminosity of SN 2017eaw are discussed. The results of our preliminary radiation–gasdynamic simulations of its light curves with the STELLA code describe satisfactorily the UBVRI observational data.  相似文献   

Optical Spectroscopy of Quasars Discovered by SRG/eROSITA with a 2.5-m Telescope at the Caucasus Mountain Observatory of SAI MSU     

Dodin  A. V.  Shatsky  N. I.  Belinski  A. A.  Atapin  K. E.  Burlak  M. A.  Zheltoukhov  S. G.  Tatarnikov  A. M.  Postnov  K. A.  Cherepashchuk  A. M.  Belvedersky  M. I.  Borisov  V. D.  Burenin  R. A.  Gilfanov  M. R.  Krivonos  R. A.  Medvedev  P. S.  Meshcheryakov  A. V.  Sazonov  S. Yu.  Sunyaev  R. A.  Khorunzhev  G. A. 《Astronomy Letters》2021,47(10):661-673

Astronomy Letters - Based on observations with the transient double-beam spectrograph (TDS) at the 2.5-m telescope of the Caucasus Mountain Observatory of SAI MSU, we have determined the redshifts...  相似文献   

Chloride-carbonate fluid in diamonds from the eclogite xenolith   总被引：1，自引：0，他引：1  

D. A. Zedgenizov  A. L. Ragozin  V. S. Shatsky 《Doklady Earth Sciences》2007,415(2):961-964

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The characteristic photoluminescence and EPR features of superdeep diamonds (São-Luis,Brazil)     

Olga P. Yuryeva  Mariana I. Rakhmanova  Vladimir A. Nadolinny  Dmitry A. Zedgenizov  Vladislav S. Shatsky  Hiroyuki Kagi  Andrey Yu. Komarovskikh 《Physics and Chemistry of Minerals》2015,42(9):707-722

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Meteorological conditions at the Caucasus Observatory of the SAI MSU from the results of the 2007–2015 campaign     

V. G. Kornilov  M. V. Kornilov  N. I. Shatsky  O. V. Vozyakova  I. A. Gorbunov  B. S. Safonov  S. A. Potanin  D. V. Cheryasov  V. A. Senik 《Astronomy Letters》2016,42(9):616-630

Based on the measurements performed from 2007 to 2015 at the summit of Mount Shatdzhatmaz adjacent to the 2.5-m telescope at the Caucasus Observatory of the SAI MSU, we have determined the statistical characteristics of basic meteorological parameters: the ambient air temperature, the ground wind speed, and the relative humidity. The stability of these parameters over the entire period of our measurements and their variations within an annual cycle have been studied. The median temperature on clear nights is +3.2°C, although there are nights with a temperature below ?15°C. The typical ground wind speed is 3 m s^?1; the probability of a wind stronger than 10 m s^?1 does not exceed 2%. The losses of observing time due to high humidity are maximal in the summer period but, on the whole, are small over a year, less than 10%. We have estimated the absolute water vapor content in the atmosphere, which is especially important for infrared observations. Minimum precipitablewater vapor is observed in December–February; the median value over these months is 5 mm. We additionally provide the wind speeds at various altitudes above the ground (from 1 to 16 km) that we obtained when measuring the optical turbulence. We present the results and technique of our measurements of the annual amount of clear night astronomical time, which is, on average, 1320 h, i.e., 45% of the possible one at the latitude of the observatory. The period from mid-September to mid-March accounts for about 70% of the clear time. A maximum of clear skies is observed in November, when its fraction reaches 60% of the possible astronomical night time.  相似文献