排序方式： 共有35条查询结果，搜索用时 15 毫秒
1.
N. E. Kozlov E. V. Martynov N. O. Sorokhtin A. A. Ivanov N. M. Kudryashov N. E. Kozlova 《Geochemistry International》2008,46(6):608-613
Rock associations characterized by heterogeneous sets of petrogeochemical parameters were compared by quantifying the degree of their similarity-dissimilarity and searching for discrimination trends between them. Using procedures specially developed for this purpose, it was demonstrated for the first time that the lithotectonic complexes of the Murmansk domain are fundamentally different from those of typical granulite-gneiss terrains and resemble the granite-greenstone terrains of the Baltic shield, Greenland, and Canada. Based on the whole data set, the Murmansk domain can be considered as a deeply eroded Archean granite-greenstone terrain retaining only the tonalite-trondhjemite-gneiss basement with abundant supracrustal enclaves. A trend of the compositional difference between the older and younger rock associations is similar to that between the tholeiitic and boninitic volcanic series. It was suggested that the petrogeochemical “age” trend reflects the initial stage of the compositional evolution of the metamagmatic rocks of the region from metamorphic rocks similar to tholeiites at the early stages to the Paleoproterozoic boninite-like rocks, which are believed to be linked to the unique PGE-bearing province of the northeastern Baltic shield. This implies that the specific metallogenic features of the region emerged already in the Archean, which supported the suggestion on the long duration of geological processes in the Early Precambrian. 相似文献
2.
3.
A. A. Sorokin A. B. Kotov E. B. Sal’nikova N. M. Kudryashov V. P. Kovach 《Stratigraphy and Geological Correlation》2007,15(3):241-257
Magmatic rocks of the Pikan and Un’ya massifs situated in eastern segment of the Mongolian-Okhotsk foldbelt are studied using isotopic-geochronological (U-Pb zircon dating) and geochemical methods. Two rock complexes different in age are recognized in the Pikan massif: the high-Al gabbro-tonalite association of the Middle Ordovician (468 ± Ma) and granodiorite-granite association of the Late Silurian-Early Devonian (415 ± 7 Ma). The Late Ordovician age (454 ± 5 Ma) is established for leucocratic granites of the Un’ya massif. As is suggested, the Pikan and Un’ya massifs are “allogenic blocks” detached from continental framework of the Mongolian-Okhotsk foldbelt and tectonically emplaced into the foldbelt structure at the last stage of its development. 相似文献
4.
The first results of U–Pb geochronological studies of acid volcanic rocks from the Oktyabrsk Complex of the Mamyn Terrane, which had previously been conventionally attributed to the Late Proterozoic, are reported. It is established that rhyodacite of the Gar’–Dzheltulak volcanic field has Late Vendian age (546 ± 14 Ma) and trachyrhyodacite of the Kosmatinsk field has Late Cambrian age (490 ± 2 Ma). As a whole, the data obtained indicate two stages of acid volcanism on the Mamyn Terrane of the eastern part of the Central Asian Fold Belt covering the boundary between the Paleozoic and Neoproterozoic, as well as the Late Cambrian. Based on the geochemical peculiarities of rocks, it may be assumed that the early stage of volcanism was controlled by subduction, whereas the late stage was governed by riftogenic processes. 相似文献
5.
Atkin E. V. Bulatov V.L. Vasiliev O. A. Voronin A. G. Gorbunov N. V. Grebenyuk V. M. Dorokhov V. A. Karmanov D. E. Kovalev I.M. Kudryashov I. A. Kurganov A.A. Merkin M. M. Panov A.D. Podorozhny D. M. Polkov D. A. Porokhovoi S. Yu. Sveshnikova L. G. Tkachev L.G. Tkachenko A. V. Turundaevskiy A. N. Filippov S. B. Shumikhin V. V. 《Astronomy Reports》2019,63(1):66-78
Astronomy Reports - Some results of studies of cosmic rays obtained during the NUCLEON space experiment in 2015–2017 are presented. This experiment was intended for direct measurements of the... 相似文献
6.
A. A. Kalinin O. V. Kazanov N. M. Kudryashov G. F. Bakaev S. V. Petrov D. V. Elizarov L. V. Lyalina 《Geology of Ore Deposits》2017,59(6):453-481
Data on gold ore objects in the Strelna Greenstone Belt in the southeastern Kola Peninsula are presented in the paper. The studied Vorgovy and Sergozero ore occurrences are localized in the zone of tectonic contact of the Neoarchean complexes making up the greenstone belt and the volcanic–sedimentary sequences of the Paleoproterozoic Imandra–Varzuga Zone. The Vorgovy gold occurrence is related to stockwork of carbonate–quartz veins and veinlets hosted in a biotite gneiss transformed into chlorite–sericite–quartz metasomatic rock with pyrrhotite–arsenopyrite dissemination. The Sergozero occurrence is localized in amphibolites corresponding to komatiitic and tholeiitic basalts hosted in biotite gneiss (metapelite). Mineralization is confined to the zone of tectonized contact between komatiitic and tholeiitic basalts, where it is controlled by a strip of metasomatic biotite–calcite rock with gersdorffite–arsenopyrite dissemination. The native gold grains medium to high in fineness are up to 0.1 mm in size and mainly localized at the contact of arsenopyrite and gersdorffite with gangue minerals. Gold mineralization is of superimposed character, and, as indicated by isotopic geochronology, was formed at the retrograde stage of the Svecofennian regional metamorphism. Comparison of ore occurrences localized in the Strelna Greenstone Belt with gold deposits in greenstone belts of the western Fennoscandian Shield and the Superior Province in Canada allows us to suggest a high perspective of the entire Strelna Belt for gold. 相似文献
7.
This paper considers the results of mineralogical, geochemical, and geochronological studies of leucogabbroids of the Karagai Massif located within the Lesser Khingan superterrane of the Central Asian fold belt. The main features of the rock-forming minerals of the gabbroids are the high calcium content of the clinopyroxene corresponding in composition to diopside-salite (Wo48–51En33–39Fs11–16) or augite (Wo22–35En46–47Fs18–33), the high basicity of the plagioclase (An90–92), and the presence of primary magmatic magnesian hornblende. The age of the massif was determined by U-Pb zircon dating as 257 ± 1 Ma. The compositional peculiarities of the gabbroids indicate that they were most probably formed in island-arc or active continental margin settings. With allowance for the existing geodynamic reconstructions and the data obtained in the present study, the formation of the Late Paleozoic gabbroids of the Karagai Massif was presumably related to the final stages of the subduction processes that preceded the collapse of the terranes of the eastern Central Asian fold belt. 相似文献
8.
This paper discusses the results of U-Pb isotopic dating of zircons from hornblendites that cut dunites of the East Khabarny
dunite-clinopyroxenite-websterite-gabbro complex in the South Urals. This complex is included into the structure of the large
Khabarny mafic-ultramafic allochthon, and the set of rocks and their petrogeochemical peculiarities allow this complex to
be compared with the Ural-Alaskan-type complexes. Zircons from hornblendites have been dated on a SHRIMP-II ion microprobe
and by the classical thermo-ionization mass spectrometric method by five fractions. The obtained results are comparable between
each other within the analysis deviation interval and show that hornblendites were formed in the Early Devonian (408–402 Ma).
This age is the upper geochronological limit in estimation of the time when dunites of the East Khabarny complex were formed.
The synchronity of intrusive hornblendite manifestation in most of the Urals in the Early Devonian is discussed. The probable
Early Devonian stage, in addition to the found Vendian and Ordovician-Silurian ones when dunite-clinopyroxenite-gabbro complexes
formed in the Urals, is suggested. 相似文献
9.
A. A. Sorokin Yu. V. Smirnov Yu. N. Smirnova N. M. Kudryashov 《Doklady Earth Sciences》2011,439(1):944-948
The U-Pb geochronological studies showed that metarhyolites from the Turan Group of the Bureya (Turan) Terrane to the east
of the Central Asian Foldbelt are Middle Cambrian (504 ± 8 Ma), not Neoproterozoic in age, as was suggested before. Metarhyolites
are younger than the Early Cambrian terrigenous-carbonate sediments from this terrane characterized by the Atdabanian archaeochyatid.
Considering that volcanic rocks have features of intraplate origin, it may be assumed that their formation corresponds to
the breakup of the Early Paleozoic passive continental margin. 相似文献
10.