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N.N. Kruk A.G. Vladimirov G.A. Babin S.P. Shokalsky N.V. Sennikov S.N. Rudnev N.I. Volkova V.P. Kovach P.A. Serov 《Russian Geology and Geophysics》2010,51(5):431-446
The history of the Vendian–Early Paleozoic formation of protoliths of continental crust in the Gorny Altai segment of the Central Asian fold belt is considered, and their composition, isotopic characteristics, and formation mechanisms are estimated. We have established two stages of crust-forming processes in Gorny Altai: Early and Late Caledonian, with the different structures of formed geoblocks and nature and compositions of crustal protoliths. At the Early Caledonian stage, fragments of oceanic lithosphere of basic composition (MORB, OIT, OIB) (TNd(DM-2st) = 0.65–1.1 Ga) formed, as well as island arcs with andesite-basaltic and andesitic protoliths with low contents of incompatible elements (TNd(DM-2st) = 0.7–0.9 Ga). At the Late Caledonian stage, the redistribution of the substance of these blocks and the external supply of material led to the formation of heterogeneous crust of turbidite basins with an oceanic basement and andesite-dacitic upper-crustal protoliths (TNd(DM-2st) varies from 0.8–0.9 Ga in the framing of the volcanic arc of Altaids to 1.4–1.6 Ga at the boundary of the Altai–Mongolian microcontinent). 相似文献
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S. N. Rudnev A. E. Izokh V. P. Kovach R. A. Shelepaev L. B. Terent’eva 《Petrology》2009,17(5):439-475
The paper presents data on the structure, composition, and age of granitoid associations (Tokhtogeshil’skii Complex) composing
the Kharanur and Sharatologoi polychronous plutons in the northern part of the Ozernala zone in western Mongolia. The Tokhtogeshil’skii
Complex was determined to consist of a number of independent magmatic associations, which were formed at 540–450 Ma, within
three age intervals (540–520, 510–485, and 475–450 Ma), have different composition, were derived from different sources, and
were emplaced in different geodynamic environments. During the first, island-arc stage (540–520 Ma), high-Al plagiogranites
were produced, which belong to tonalite-plagiogranite (531 ± 10 Ma) and diorite (529 ±6 Ma) associations in the Kharanur pluton,
low-Al plagiogranites of the tonalite-plagiogranite association (519 ± 8 Ma) in the Sharatologoi pluton, and rocks of the
Khirgisnur peridotite-pyroxenite-gabbronorite complex (Kharachulu and Dzabkhan massifs). The rocks of the diorite and plagiogranite
associations of the Kharanur pluton have ɛNd(T) from +7.9 to +7.4, TNd(DM) = 0.65 Ga, and (87Sr/86Sr)0 = 0.7038–0.7039. The plagiogranites of the Sharatologoi pluton (tonalite-plagiogranite association) are characterized by
ɛNd(T) from +6.5 to +6.6, TNd(DM) = 0.73–0.70 Ga, and (87Sr/86Sr)0 = 0.7038–0.7039, which suggest predominantly juvenile subduction sources of the parental melts at a subordinate role of ancient
crustal material. During the second, accretionary stage (510–485 Ma), low-Al plagiogranites of the diorite-tonalite-plagiogranite
association of the Sharatologoi pluton (494 ± 10 Ma, M type) were formed. The Sr-Nd isotopic characteristics of these rocks
ɛNd(T) = +6.6, (87Sr/86Sr)0 = 0.7039 are analogous to those of the plagiogranitoids of the early type. This suggests that the melted sources were similar
in composition. During the third, postcollisional stage (475–450 Ma), rocks of the diorite-granodiorite-granite association
were formed (459 ± 10 Ma, type I) in the Kharanur pluton. These rocks have ɛNd(T) = +5.1, TNd(DM) = 0.74 Ga, and (87Sr/86Sr)0 = 0.7096. The parental melts were supposedly derived by means of partial melting of “the Caledonian” juvenile crust with
the addition of more ancient crustal material. 相似文献
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Mobility of trace elements during subduction metamorphism as exemplified by the blueschists of the Kurtushibinsky Range,Western Sayan 总被引：1，自引：0，他引：1
N. I. Volkova S. I. Stupakov G. A. Babin S. N. Rudnev A. A. Mongush 《Geochemistry International》2009,47(4):380-392
In order to evaluate the mobility of trace elements during subduction metamorphism, the geochemistry of blueschists of the Dzhebash Group from the Kurtushibinsky Range of the Western Sayan (basins of the Koyard and Oresh rivers) was studied, and the chemical compositions of high-pressure rocks were compared with weakly altered basalts from the same region. The protoliths of the blueschists were probably metabasalts of similar age from the ophiolitic dike complex, the pillow lavas of the Verkhnekoyardsky Formation crowning them, and the pillow basalts of the Kurtushibinsky Formation. The spatial association of the blueschists with the Kurtushibinsky Formation basalts and identical trace element patterns in these rocks allow us to suppose the cogenetic character of their protoliths. Geological and geochemical data suggest their formation in an oceanic plateau setting, whereas the mafic rocks of the dike complex and the Verkhnekoyardsky Formation show island-arc affinity. A comparison of the Dzhebash Group blueschists with the chemically equivalent Kurtushibinsky basalts showed that high-pressure metamorphism caused only minor changes in their compositions. These rocks are almost indistinguishable with respect to such fluid-immobile components as Ti, P, Zr, Hf, Y, and middle and heavy rare earth elements. On the other hand, the blueschists are strongly depleted in potassium. The selective removal of Rb and Ba during blueschist metamorphism was observed only in those samples that showed the most extensive removal of potassium. 相似文献
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N. N. Kruk O. A. Gavryushkina S. N. Rudnev S. P. Shokalsky E. A. Vasyukova A. B. Kotov E. B. Sal’nikova A. V. Travin V. P. Kovach E. A. Kruk 《Petrology》2017,25(3):318-337
Geological, mineralogical, petrographic, geochemical, and geochronological data are reported for granitoids of the Aturkol Massif (Gorny Altai). It is shown that it was formed in within-plate setting in the Early Triassic, nearly simultaneously with flood basalts of the Kuznetsk Basin and alkalic basite and lampropyre dike swarms in the western Altai-Sayan Fold Region. At the same time, the mineralogical-petrographic, geochemical, and isotope characteristics of the considered granitoids are close to those of I-type granites. Intraplate signatures (elevated HFSE and REE) are recognized only in the least silicic rocks (granosyenites). Obtained data suggest mantle–crustal nature of the granitoids. They were formed by mixing of lamprophyre magmas with high pressure (>10 kbar) crustal melts derived from a mixed source consisting mainly of N-MORB-type metabasites with insignificant admixture of high-Ti basalts and metasedimentary rocks. The contribution of mantle component in the granitoids was insignificant (<20%). Proposed petrogenetic mechanism can provide the formation of large volumes of granitoid magmas with “crustal” geochemical and isotope signatures in an intraplate setting. 相似文献
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We generalize results of geological, geochronological, geochemical, and isotope-geochemical studies of the Vendian–Early Cambrian island-arc plagiogranitoid magmatism in the Altai–Sayan folded area and in the Lake Zone of western Mongolia. Based on these data, we analyzed the scales of development of plagiogranitoid magmatism, studied the petrologic composition and isotope characteristics of granitoids, and established the main sources of plagiogranitoid-generating melts and the leading mechanisms of formation of Early Caledonian juvenile crust. 相似文献
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V. V. Golozubov N. N. Kruk V. I. Kiselyov S. N. Rudnev S. A. Kasatkin E. A. Kruk 《Russian Journal of Pacific Geology》2017,11(2):110-122
A detailed study of a relatively well-exposed fragment of the Barabash Formation in the southern part of the Voznesenka terrane is carried out to specify the geodynamic settings of the Permian volcanogenic and volcanogenic-sedimentary complexes in South Primorye. It is established that the basaltic flows juxtaposed in the studied sequence originated from sharply different sources. The geochemical characteristics indicate that the basalts from the sequence base were presumably derived by melting of oceanic lithospheric mantle or asthenosphere, while the source of the overlying basalts was lithospheric mantle reworked by a subduction process. The basalts are subsequently overlain by tuffaceous–terrigenous and terrigenous rocks and limestones with remains of Capitanian (Middle Permian) fauna. Accessory zircons extracted from the tuffaceous–terrigenous rocks yield an U–Pb concordant age of 233.3 ± 3.3 Ma (Middle Triassic Ladinian Stage) for the youngest zircon population. The obtained data lead us to conclude that the Barabash Formation is a tectonostratigraphic rather than stratigraphic unit and may be a fragment of the Triassic accretionary wedge. The obtained data cast doubt on the accepted assignment of this unit to the Voznesenka terrane. It is more logical to include it in the Laoelin–Grodekov terrane, which represents a fragment of the Late Paleozoic active continental margin. This suggests that the boundary between these blocks should be specified and the timing of the final stage of amalgamation of the Laoelin–Grodekov terrane with the terranes of the Bureya–Khanka orogenic belt should be revised. 相似文献
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S.N. Rudnev G.A. Babin V.P. Kovach V.Yu. Kiseleva P.A. Serov 《Russian Geology and Geophysics》2013,54(1):20-33
The structure, composition, and age of Vendian–Early Cambrian plagiogranitoid associations composing the Kshta and Taraskyr massifs of the Yenisei pluton in the Altai–North Sayan island-arc belt are considered. We have established that these associations formed within 550–520 Ma and differ in petrographic composition and sources. Two stages of island-arc plagiogranitoid magmatism are recognized: early (550–540 Ma, formation of plagiogranitoids of the Kshta (545 ± 8 Ma) and Taraskyr (545 ± 7 Ma) massifs) and late (525–520 Ma, formation of plagiogranitoids of the Maina complex of the Yenisei (524 ± 2 Ma) and Tabat plutons). By petrochemical composition and geochemical characteristics, the rocks of the Kshta massif are high-alumina plagiogranitoids similar to adakites. They might have been produced through the melting of metabasites compositionally similar to N-MORB in equilibrium with garnet-containing restite during the subduction of oceanic slab at ≥ 15 kbar. The rocks of the Taraskyr massif are low-alumina plagiogranites. They formed through the melting of metabasites located in the lower layers and(or) the basement of the island-arc system in equilibrium with plagioclase-containing restite at 3–8 kbar. The low-alumina plagiogranitoids of the Yenisei pluton melted out under the same conditions. Isotope-geochemical studies showed that the Vendian–Early Cambrian plagiogranitoids formed at the early stage are characterized by high positive ∑ Nd(T) values (7.5–4.9), Late Riphean model Nd-age (TNd(DM) = 0.64–0.98 Ga), and Sr isotope ratio varying from 0.7040 to 0.7053. These data point to the juvenile parental melts of the rocks and the varying content of ancient crustal material in the magma generation zone. 相似文献