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991.
This paper reports REE data on resin-asphaltene components of oil from six oil-gas-bearing provinces and on bitumoids from
inferred oil-source rocks (domanikites and bazhenites). It was shown that, regardless of geological-tectonic structure of
the regions, oil composition, depth of reservoirs, and host lithologies, oil exhibits significant REE fractionation, and,
unlike bitumoids, positive Eu anomaly. The (Eu/Sm)n ratio increases from asphaltenes to resins and further to oils. Based on REE distribution in oil, source rocks, and bitumoids,
it was concluded that deep-seated fluids were one of the possible sources that defined the trace element composition of oil. 相似文献
992.
S.V. Efremov S.I. Dril G.P. Sandimirova I.V. Sandimirov 《Russian Geology and Geophysics》2010,51(12):1257-1261
The validity of the Rb/Sr isotopic ages of Cretaceous granitoid complex in the central Chukchi region has been verified. The performed studies showed that the Rb/Sr isotopic ages of late-orogenic granitoids are not reliable. Their variation can be explained in terms of the mixing of primary mantle magmas with continental-crust matter. Most probably, the variation is due to the constant compositions of mixing components and their proportions. 相似文献
993.
U-Th-Pb systematics of precambrian carbonate rocks: Dating of the formation and transformation of carbonate sediments 总被引:1,自引:0,他引:1
O. K. Kaurova G. V. Ovchinnikova I. M. Gorokhov 《Stratigraphy and Geological Correlation》2010,18(3):252-268
The current state in the Pb-Pb dating of the formation and epigenesis of Precambrian carbonate sediments has been reviewed.
The geochemistry of admixture elements (U, Th, Pb, Rb, Sr, Mn, and Fe) constituting carbonate minerals and the redistribution
of the elements in the course of early diagenesis and epigenesis have been considered. The advantages of choosing samples
for Pb-Pb dating on the basis of geochemical criteria similar to those applied for Sr-isotope stratigraphy and the potentialities
of applying different methods of decontamination of specimens, analyzed from surface contamination and possible epigenetic
carbonate phases, were illustrated. By the example of a series of carbonate formations, distinctions in susceptibility of
U-Pb and Rb-Sr systems of carbonate minerals to secondary transformations have been demonstrated. The prospects for using
the method of step solution allowing noncogenetic carbonate generations to be separated and thus the accuracy and reliability
of Pb-Pb dates to be upgraded were considered. 相似文献
994.
Doklady Earth Sciences - 相似文献
995.
996.
Shchapova Yu. V. Votyakov S. L. Ivanov V. Yu. Pustovarov V. A. 《Geology of Ore Deposits》2010,52(7):679-687
The luminescence properties of two single zircon crystals from kimberlite of Yakutia have been studied, excited by the DORIS
HASYLAB synchrotron, Germany, within energy range from the visible to the soft X-ray region (5–25, 50–200, and 500–620 eV)
at temperatures of 300 and 10 K. The luminescence spectra in the range of 2.5 to 6.0 eV and excitation spectra of the main
bands have been examined, the physical nature of the luminescence centers has been discussed, and the luminescence properties
of a crystal containing growth (radiation) structural defects and a crystal with the same impurities but annealed in air at
1200°C are compared. The zoned structure of the mineral has been considered and the value of the energy gap (E
g) in the mineral has been estimated at 7.1 eV. Two groups of luminescence bands caused by impurities of intrinsic (growth,
radiation) nature (E
max = 2.1, 2.7–2.8, and 3.2–3.3 eV) and matrix luminescence (E
max = 4.4−4.7 and 5.4 eV) probably with the participation of excitons were distinguished on the basis of selective excitation
of zircon with different synchrotron energies relative to the gap value (E
excit < E
g, E
excit ∼ E
g, and E
excit ≫ E
g). The short-lived component with a response time of 4 ns has been revealed in the afterglow of zircon in the region of 5.4
eV. 相似文献
997.
Bing Wang Shengtian Yang Changwei Lü Jing Zhang Yujuan Wang 《Environmental Earth Sciences》2010,59(6):1337-1347
Green plants play an important role in energy flows and material cycles. The net primary productivity (NPP) reflects the capability
of vegetation to convert solar energy into photosynthate (fixed carbon). Understanding the factors that contribute to variations
in NPP is of key importance for improving the rock-desertification environment in karst areas. In this paper, the NPP model
(Light Use Efficiency model) is modified on the basis of remote sensing data [moderate resolution imaging spectroradiometer
(MODIS)], climate data and observed information. Then the model is employed to estimate the spatial–temporal variations of
NPP in the Guizhou Province, China. Finally, the NPP differences between karst area and non-karst area, and the relationships
between NPP and climate factors are analyzed. The results show that the NPP estimated using MODIS data are reasonable. The
mean NPP of territorial vegetation is 421.46 gC m−2 year−1; the NPP in the non-karst area is 13.3% higher than that in the karst area; the correlation degree between NPP and precipitation
is better in southeastern and western districts. 相似文献
998.
999.
A. A. Sorokin I. V. Buchko A. B. Kotov S. D. Velikoslavinsky 《Russian Journal of Pacific Geology》2010,4(5):418-428
The Baladek Massif represents a tectonic block located at the boundary between the SE framing of the North Asian craton and
the fold structures of the Galam terrane of the Mongol-Okhotsk fold belt. According to the existing concepts, the rocks of
this massif are regarded as Precambrian complexes of the aforementioned craton. This paper reports the results of studying
the fragment of the Baladek Massif in the Gerbikan River basin. New geochemical data obtained on the gabbros, gabbroanorthosites,
and ultramafic rocks testify to their similarity with typical ophiolite complexes. An underlying complex of metamorphic ultrabasic
rocks, a layered complex of pyroxenites and “cumulate” gabbros, gabbroanorthosites, and a complex of isotropic gabbros were
distinguished within this fragment. It is highly possible that the basic volcanic rocks and jaspers of the Silurian-Lower
Devonian sequences of the Galam segment of the Mongol-Okhotsk fold belt also belong to the inferred ophiolite complex. 相似文献
1000.
I. Yu. Melekestseva V. A. Kotlyarov P. V. Khvorov V. N. Ivanov V. E. Beltenev I. G. Dobretsova 《Geology of Ore Deposits》2010,52(8):800-810
The porous fine-grained to microcrystalline copper-zinc ore of the Semenov-2 hydrothermal field, a site in the Semenov hydrothermal
cluster discovered in 2007 (13°31′N, MAR), is anomalously enriched in Au (22–188 ppm) and Ag (127–1787 ppm). Chalcopyrite,
isocubanite, würtzite, and opal are major minerals; sphalerite, marcasite, pyrite, and covellite are auxiliary; and galena,
pyrrhotite, native gold, silver telluride, barite, and aragonite are sporadic. Gold containing 0.31 to 23.07 wt % Ag occurs
as up to 9-μm-sized subhedral, dendritelike, and elongated grains mostly hosted in opal and less frequently in sphalerite
and in pores within isocubanite-chalcopyrite aggregate. An elongated grain (2 × 4 μm in size) of the Ag-Te phase was found
in a pore. So far only basalts have been dredged from the Semenov-2 field, but anomalous gold and silver concentrations suggest
the influence of ultramafic rocks; the latter were found 1.5 km westward, in the Semenov-1 hydrothermal field. Mineral assemblage
and morphology of gold particles indicate its primary origin in contrast to the hydrothermal fields hosted in basalts, where
gold is a product of remobilization. Zonal gold grains, found on oceanic floor for the first time, are characterized by low
Ag content in the cores and high Ag content in the outer rims, reflecting variation in formation conditions. 相似文献