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More than 70 samples of Turonian-Danian samples from the eastern and southeastern Russian Plate were studied by the X-ray phase analysis and classical wet chemistry. It has been established that zeolites occur in all studied types of carbonate, siliceous, and clayey rocks. Steadily high zeolite concentrations were revealed in sections of the Santonian formation. Character of zeolite formation was examined simultaneously in both spatiotemporal and lithogenetic aspects. Analysis of the stagewise distribution of zeolites supports the concept of primary volcanogenic nature of the zeolite-forming material and actually represents an indicator of the activity of explosive volcanism in the Late Cretaceous-Paleocene. It is emphasized that high zeolite concentrations in Upper Cretaceous-Paleocene formations are a prospecting guide for zeolite raw material. They can serve as scientific basis for the formulation of prognostic-revision and prospecting works in the study region 相似文献
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A.M. Spiridonov V.D. Kozlov L.D. Zorina V.I. Men’shikov V.A. Bychinskii 《Russian Geology and Geophysics》2010,51(8):846-856
The distribution of gold in rocks from some igneous complexes of the central and southwestern areas of eastern Transbaikalia (Daurian, Aga, and Argun structure-formational zones) was studied by quantitative extraction–atomic-absorption analysis and mass spectrometry with inductively coupled plasma (Element-2 mass spectrometer). High gold concentrations (on average, 0.0043 ppm) are typical of the most widespread hornblende-biotite granodiorites and granites of the main phases of batholith intrusions in the Upper Paleozoic Unda complex in the east of the study area and in the Triassic–Middle Jurassic Kyra complex in the west. The rocks of the Early–Middle Jurassic (Sokhondo) and Middle–Upper Jurassic (Shakhtama, Kharalga, and Kukul’bei) complexes have much lower Au concentrations (mainly 0.0014–0.0030 ppm), with the minimum ones established in the Shakhtama complex. During the magmatic differentiation of granitoid intrusions, the concentrations of gold in the late leucogranite differentiates decreased.The Au concentrations in the studied complexes do not depend on the composition of the host terrigenous rocks of different ages, which evidences the endogenous nature of the revealed differences in Au concentrations in the regional granitoids. Abnormally high concentrations of gold in some studied samples are observed mainly in the regional hydrothermal mineralization occurrences.The classification R-type cluster analysis showed that all variables of the studied igneous rocks are subdivided into three groups by the degree of correlation. Gold shows a distinct tendency to the correlation with siderophile oxy- and sulfurophile groups of metals. The Q-type analysis generally confirmed the correctness of the known formational classification of the regional granitoids. 相似文献
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The role of rifting in the evolution of the continental margin of Eastern Asia: Geophysical evidence
The role of rift processes is analysed in the structural evolution of the continental margins of Eastern Asia including the Indo-China Peninsula and North China plain. Paleoreconstructions were made for the Indo-China Peninsula to characterize individual stages of rifting covering the Late Cretaceous-Eocene, Oligocene-Middle Miocene and Late Pliocene-Early Quaternary epochs. The rifting of continental margins occurred synchronously with spreading processes in marginal seas, whereas the formation of rift structures in the North China plain was concurrent with the formation of a deep-water basin of the Philippine Sea. The development of asthenospheric diapire led to crustal extension and was responsible for the formation of rift structures in marginal seas and continental margins. 相似文献
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Svetlana O. Zorina Oksana V. Pavlova Bulat M. Galiullin Vladimir P. Morozov Alexey A. Eskin 《中国科学:地球科学(英文版)》2017,60(1):58-70
A detailed study of the mineral composition and microstructure of the black shales associated with OAE1a (Eastern Russian Platform), OAE1b (Middle Caspian), and the host rocks has been carried out using X-ray diffraction, scanning electron microscopic, and microprobe analyses. The results provide important constraints for depositional environments in the sedimentary basins. Black shales with pyrite framboids imply euxinic (sulfidic) conditions with increased organic matter preservation. Disintegrating framboids suggest partial or complete dissolution of the organic matter inside the framboids due to increasing water oxygenation. OAE1a on the Eastern Russian Platform is heterogeneous as it includes thin interbeds of concretionary coccolith limestones within the interval of bituminous shales, and correlates with the Lower Aptian Rhagodiscus angustus nannofossil zone. The coccolith limestones indicate short intermittent episodes of interrupted stagnation, rapid oxygenation, and restoration of normal marine conditions. The presence of montmorillonite, albite, microcline, and diopside in the bituminous siltstones and in the host siltstones of OAE1a on the Eastern Russian Platform, as well as a high content of titanium in the black siltstones correlated with OAE1b in the Middle Caspian allow proposing significant input of pyroclastic material into the extant sea. 相似文献
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A.M. Spiridonov L.D. Zorina S.P. Letunov V.Yu. Prokof’ev 《Russian Geology and Geophysics》2010,51(10):1102-1109
Based on comprehensive studies of fluid inclusions in quartz formed at different stages of hydrothermal process, we consider the physicochemical conditions of formation of epithermal ores (K1) in the Balei ore field. The limiting parameters of hydrothermal process have been established: 353–131 °C, 150–30 bars, and salt concentrations of 7.6–0.5 wt.%-NaCl equiv. A specific feature of the ore-forming process at the Balei deposits is a rapid drop in temperature and pressure, which is typical of open hydrothermal systems. The temperature increase at the beginning of each stage evidences pulse-like ore formation. The productive stage coincides with the initiation of a drastic decrease in temperature (<225 °C) and salt concentration in the solution. The deposits resulted from the functioning of the common Balei ore-magmatic system at shallow depths with a high permeability of the host rocks. High-K calc-alkalic magmas might have been sources of gold mineralization. The ore formation zone is localized above intrusive bodies near their roof. It is not ruled out that the Balei gold was partly borrowed from the products of the early cycles (J2-3) of gold mineralization and from the host rocks. 相似文献
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I. V. Chernyshev V. Yu. Prokof’ev N. S. Bortnikov A. V. Chugaev Yu. V. Goltsman V. A. Lebedev Yu. O. Larionova L. D. Zorina 《Geology of Ore Deposits》2014,56(1):1-14
The Darasun ore field situated in the southern West Stanovoi Terrane near the Mongolia-Okhotsk Suture comprises the Darasun (>100 t Au), Talatui (～38.2 t Au), and Teremki (3 t Au) lode gold deposits. In the opinion of many researchers, the Darasun deposit is spatially and paragenetically linked to granodiorite porphyry of the Amudzhikan Complex and related metasomatic rocks (beresites). Whole-rock samples of granodiorite porphyry, monomineralic fractions of plagioclase, K-feldspar, and biotite, as well as sericite from beresite (26 samples in total), were analyzed by the Rb-Sr method. Eight biotite and sericite samples were analyzed by the K-Ar method. The Rb-Sr mineral isochrons obtained for individual granodiorite porphyry samples yielded initial 87Sr/86Sr ratios varying from 0.70560 to 0.70591. The consistent results of both methods allowed us to accept the ages of granodiorite porphyry and beresite as 160.5 ± 0.4 and 159.6 ± 1.5 Ma, respectively. The age of granodiorite porphyry of the Amudzhikan Complex of 160.5 ± 0.4 Ma corresponds to the boundary between the Early and Middle Jurassic and marks the completion of collision between the East Siberian and Mongolia-China continents and related orogeny. Since that time, the eastern Transbaikal region has been involved in the postorogenic (within-plate) stage of evolution, characterized by the formation of large gold, uranium, and other ore deposits. 相似文献
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An event-based depositional model for the Paleocene—Eocene sandy–clayey–siliceous deposits of the Russian Platform was proposed. The model was based on pulsational input of pyroclastic material and intrusion of sandy injectites. These processes should be taken into account to identify the stratigraphic position of the Paleocene–Eocene lithostratigraphic units in the eastern, southeastern, and southern parts of the Russian Platform. 相似文献
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The reality of the global‐scale sedimentation breaks remains controversial. A compilation of data on the Jurassic–Cretaceous unconformities in a number of regions with different tectonic settings and character of sedimentation, where new or updated stratigraphic frameworks are established, permits their correlation. Unconformities from three large reference regions, including North America, the Gulf of Mexico, and Western Europe, were also considered. The unconformities, which encompass the Jurassic‐Cretaceous, the Lower–Upper Cretaceous and the Cretaceous–Palaeogene transitions are of global extent. Other remarkable unconformities traced within many regions at the base of the Jurassic and at the Santonian–Campanian transition are not known from reference regions. A correlation of the Jurassic–Cretaceous global‐scale sedimentation breaks and eustatic curves is quite uncertain. Therefore, definition of global sequences will not be possible until eustatic changes are clarified. Activity of mantle plumes is among the likely causes of the documented unconformities. 相似文献