New data on Upper Kimmeridgian-Tithonian biostratigraphy and ammonites of the eastern Crimea     

V. V. Arkad’ev  M. A. Rogov 《Stratigraphy and Geological Correlation》2006,14(2):185-199

Based on ammonites, Upper Kimmeridgian sediments are first established in the Crimean Mountains. The Kimmeridgian-Tithonian boundary recognizable in a continuous section is placed inside the Dvuyakomaya Formation of uniform largely clayey sediments. Assemblages of Kimmeridgian ammonites Lingulaticeras cf. procurvum (Ziegler), Pseudowaagenia gemmellariana Oloriz, Euvirgalithacoceras cf. tantalus (Herbich), Subplanites sp.) and Tithonian forms (?Lingulaticeras efimovi (Rogov), Phylloceras consaguineum Gemmellaro, Oloriziceras cf. schneidi Tavera, and Paraulacosphinctes cf. transitorius (Oppel) are described. A new biostratigraphic scheme proposed for the upper Tithonian-Berriasian of the Crimean Mountains includes the following new biostratigraphic units: the Euvirgalithacoceras cf. tantalus Beds of the upper Kimmeridgian, ?Lingulaticeras efimovi Beds of the lower Tithonian, and Oloriziceras cf. schneidi and Paraulacosphinctes cf. transitorius beds of the upper Tithonian. The middle Tithonian is proposed to consist of the fallauxi and semiforme (presumably) zones. The ammonities found determine the early Kimmeridgian-Berriasian age of the Dvuyakornaya Formation that is most likely in tectonic contact with the underlying Khutoran Formation.  相似文献   

The Kyrgyz-Ata Synform in the South Tien Shan: Structural and kinematic aspects of its evolution     

Yu. A. Morozov  V. G. Talitskii 《Geotectonics》2006,40(1):37-52

The complexes of metamorphic rocks that take part in the tectonic structure of the South Tien Shan are mostly confined to the cores of large synforms and occupy high structural position therein. Problems of their age, origin, metamorphic conditions, and relationships with the adjacent unmetamorphosed Paleozoic sequences have remained debatable throughout the history of geological investigations. The results of detailed studies of the Kyrgyz-Ata Synform, a typical structure of the Turkestan-Alay Zone in the South Tien Shan, are reported in this paper. The metamorphic rocks of the Kan Group participate in the structure of this synform. On the basis of the study of structural assemblages and the kinematic analysis, it is concluded that the multistage evolution of this tectonic unit proceeded under transpressive conditions of volcanic trough “crushing.” The detailed study of rock alteration in the contact zone between the Kan Group and the Middle Devonian basic volcanic rocks allowed us to suggest that the metamorphic Kan Group is not a self-dependent stratigraphic unit but represents an infrastructure (a metamorphosed analogue of the volcanic sequence and underlying rocks) displaced tectonically over its own suprastructure.  相似文献   

Basanites of Mt. Khukhch: First mineralogical-geochemical data on the Neogene K-Na alkaline magmatism in western Kamchatka     

A. B. Perepelov  M. Yu. Puzankov  A. V. Ivanov  T. M. Filosofova 《Doklady Earth Sciences》2006,409(5):765-768

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Managanese and iron in the White Sea: Sedimentation and diagenesis     

A. G. Rozanov  I. I. Volkov  N. M. Kokryatskaya  M. V. Yudin 《Lithology and Mineral Resources》2006,41(5):483-501

Iron and manganese in bottom sediments studied along the sublatitudinal transect from Kandalaksha to Arkhangelsk are characterized by various contents and forms depending on sedimentation environments, grain size of sediments, and diagenetic processes. The latter include redistribution of reactive forms leading to enrichment in Fe and Mn of the surface sediments, formation of films, incrustations, and ferromanganese nodules. Variations in the total Fe content (2–8%) are accompanied by changes in the concentration of its reactive forms (acid extraction) and the concentration of dissolved Fe in the interstitial water (1–14 μM). Variations in the Mn content in sediments (0.03–3.7%) and the interstitial water (up to 500 μM) correspond to a high diagenetic mobility of this element. Changes in the valence of chemical elements results in the redox stratification of sediment strata with maximum concentrations of Fe, Mn, and sulfides. Organic matter of sediments with a considerable terrestrial constituent is oxidized by bottom water oxygen mainly at the sediment surface or in anaerobic conditions within the sediment strata. The role of inorganic components in organic matter oxidation changes from surface sediments, where manganese oxyhydroxide dominates among oxidants, to deeper layers, where sulfate of interstitial water serves as the main oxidant. Differences in river runoff and hydrodynamics are responsible for geochemical asymmetry of the transect. The deep Kandalaksha Bay serves as a sediment trap for manganese (Mn content in sediments varies within 0.5–0.7%), whereas the sedimentary environment in the Dvina Bay promotes its removal from sediments (Mn 0.05%).  相似文献   

A major achievement of Russian science (review and comments on the book Introduction to Tectonophysics)     

V. E. Khain 《Geotectonics》2006,40(1):81-82

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Silicate and salt melts in the genesis of the industrial’noe tin deposit: Evidence from inclusions in minerals     

V. B. Naumov  V. S. Kamenetsky 《Geochemistry International》2006,44(12):1181-1190

The data obtained on melt and fluid inclusions in minerals of granites, metasomatic rocks, and veins with tin ore mineralization at the Industrial’noe deposit in the southern part of the Omsukchan trough, northeastern Russia, indicate that the melt from which the quartz of the granites crystallized contained globules of salt melts. Silicate melt inclusions were used to determine the principal parameters of the magmatic melts that formed the granites, which had temperatures at 760–1020°C, were under pressures of 0.3–3.6 kbar, and had densities of 2.11–2.60 g/cm³ and water concentrations of 1.7–7.0 wt %. The results obtained on the fluid inclusions testify that the parameters of the mineral-forming fluids broadly varied and corresponded to temperatures at 920–275°C, pressures 0.1–3.1 kbar, densities of 0.70–1.90 g/cm³, and salinities of 4.0–75.0 wt % equiv. NaCl. Electron microprobe analyses of the glasses of twelve homogenized inclusions show concentrations of major components typical of an acid magmatic melt (wt %, average): 73.2% SiO₂, 15.3% Al₂O₃, 1.3% FeO, 0.6% CaO, 3.1% Na₂O, and 4.5% K₂O at elevated concentrations of Cl (up to 0.51 wt %, average 0.31 wt %). The concentrations and distribution of some elements (Cl, K, Ca, Mn, Fe, Cu, Zn, Pb, As, Br, Rb, Sr, and Sn) in polyphase salt globules in quartz from both the granites and a mineralized miarolitic cavity in granite were assayed by micro-PIXE (proton-induced X-ray emission). Analyses of eight salt globules in quartz from the granites point to high concentrations (average, wt %) of Cl (27.5), Fe (9.7), Cu (7.2), Mn (1.1), Zn (0.66), Pb (0.37) and (average, ppm) As (2020), Rb (1850), Sr (1090), and Br (990). The salt globules in the miarolitic quartz are rich in (average of 29 globules, wt %) Cl (25.0), Fe (5.4), Mn (1.0), Zn (0.50), Pb (0.24) and (ppm) Rb (810), Sn (540), and Br (470). The synthesis of all data obtained on melt and fluid inclusions in minerals from the Industrial’noe deposit suggest that the genesis of the tin ore mineralization was related to the crystallization of acid magmatic melts. Original Russian Text@ V.B. Naumov, V.S. Kamenetsky, 2006, published in Geokhimiya, 2006, No. 12, pp. 1279–1289.  相似文献   

The late visean-serpukhovian stage in paleozoic reef formation     

V. G. Kuznetsov  A. I. Antoshkina 《Stratigraphy and Geological Correlation》2006,14(2):223-223

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On two types of metalliferous carbonaceous rocks     

I. N. Tomson  O. P. Polyakova  V. Yu. Alekseev  V. A. Baskina 《Geology of Ore Deposits》2006,48(1):74-76

Two types of metalliferous carbonaceous rocks that differ in associated metals are considered. One of them is characterized by gold occurring in finely dispersed arsenopyrite and arsenic-bearing pyrite, and the other, by finely impregnated native metals in carbonaceous matter. Rocks of the first type also contain elements of the platinum group, while those of the second type bear rhenium, silver, iron, molybdenum, and other metals. Graphitic mineralization is usually localized in the shear zone associated with alkaline basalts.  相似文献   

A probabilistic interpretation of the law of earthquake recurrence: Case study of the Kamchatka region     

V. V. Bogdanov 《Doklady Earth Sciences》2006,408(4):635-639

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Computer microtomography of zircon: A new approach to the selection of targets for U-Pb geochronologic studies     

Yu. V. Plotkina  E. B. Sal’nikova  A. B. Kotov  M. D. Tolkachev  M. R. Pavlov 《Petrology》2006,14(2):201-208

The paper reports results obtained by the complex studying of zircon crystals from rocks of various genesis. Zircon is one of the minerals most often used as geochronometers. It also provides genetic information on superimposed processes that is “recorded” in the external and internal morphology of its crystals. This mineral is thoroughly examined to select its unaltered crystals for U-Pb dating by the single-grain method. Zircon grains are selected with the use of optical and electron microscopy and cathodoluminescence. This publication presents the first results obtained by examining zircon by computer microtomography (μCT) and the results of the studying of the external and internal structure by conventional techniques ([optical microscopy and SEM (SE and CL)]. The paper demonstrates the advantages of the application of the μCT techniques to the selection of targets for U-Pb zircon dating: there is no need for the special preparation of the samples and no material is destructed. However, this technique may be not informative enough if the zircon contains inherited core whose density does not differ from the density of the surrounding mineral.  相似文献