First Results of Dating Detrital Zircons from the Late Precambrian Quartzite–Schist Sequences of the Chu Block (Southern Kazakhstan)     

Kanygina  N. A.  Tretyakov  A. A.  Degtyarev  K. E.  Pang  K.-N.  Wahg  K. L.  Lee  H.-Y.  Plotkina  J. V. 《Doklady Earth Sciences》2019,489(1):1273-1276

Doklady Earth Sciences - U–Pb geochronological studies of detrital zircons from quartzite–schist sequences of the Akbastau Formation of the Chu Block (northwestern part of the...  相似文献   

Age and sources of granitoids in the junction zone of the Caledonides and Hercynides in southwestern Mongolia: Geodynamic implications     

I. K. Kozakov  V. P. Kovach  E. V. Bibikova  T. I. Kirnozova  N. Yu. Zagornaya  Yu. V. Plotkina  V. N. Podkovyrov 《Petrology》2007,15(2):126-150

The paper reports newly obtained geological, geochronological (U-Pb zircon method), Nd isotopic, and geochemical data on Middle and Late Paleozoic granitoids and metamorphic rocks from the southern slope of the Mongolian Altai and Gobi Altai and on granitoids from the Trans-Altai Gobi. Tectonically, the former rocks are hosted in the margin of a Caledonian paleocontinent, and the latter are localized among island-arc and oceanic complexes related to the development of the Hercynian Southern Mongolian Ocean. According to their geological setting, the intrusive complexes are subdivided into two major groups: (i) related to processes of regional metamorphism and (ii) separated from these processes. Geochemical data suggest that the source of most of the granitoids and metamorphic rocks contained island-arc rocks and their erosion products. Nd isotopic evidence indicates that practically all of the allochthonous granitoids, regardless of their composition, age, and structural setting, have positive ?_Nd(T) values [i.e., belong to the ?(+) type] and could not be formed by the melting of metaterrigenous rocks widespread at the modern erosion level. These granitoids in both the Caledonian and the Hercynian structures have practically identical Late Riphean Nd model ages [T_Nd(DM) = 0.97–0.60 Ga], which become slightly younger in the granitoids of the Hercynides. The exception are ultrametamorphic subautochthonous ?(?) granites of the first group localized in the peripheral part of migmatite fields. The sources of these granitoids could be the host metaterrigenous rocks. The results obtained in the course of this research suggest, with regard for preexisting data on granitoids in the isotopic provinces in Central Asia, that the sources of the Paleozoic granitoids were the rocks of the “juvenile” Caledonian and Hercynian island-arc crust and of the older crust of cratonic blocks with a Early Precambrian and Late Riphean basement, respectively. The Late Riphean crustal material in Caledonian and Hercynian structures related to the development of the corresponding oceanic basins most probably consisted of clastic sediments or relatively small fragments of the Late Riphean crust. The occurrence of this crustal material in the sources of the granitoids can be explained by the involvement of sediments in subduction zones and the participation of these sediments and fragments of Late Riphean complexes in the accretionary-collision processes during the closure of the paleoceanic basins. Simultaneously, the subduction zones received juvenile material that could be later involved in the melting processes together with older rocks.  相似文献   

Early Paleozoic granitoids of the Aqtau-Dzungar microcontinent (Central Kazakhstan)     

K. E. Degtyarev  K. N. Shatagin  A. B. Kotov  E. B. Sal&#;nikova  M. V. Luchitskaya  S. Z. Yakovleva  Yu. V. Plotkina  A. M. Fedoseenko 《Doklady Earth Sciences》2006,411(8):1204-1208

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Neoproterozoic complexes of the shelf cover of the Dzabkhan terrane basement in the Central Asian Orogenic Belt     

I. K. Kozakov  A. B. Kuznetsov  Ch. Erdenegargal  E. B. Salnikova  I. V. Anisimova  Ju. V. Plotkina  A. M. Fedoseenko 《Stratigraphy and Geological Correlation》2017,25(5):479-491

The formation stages of high-grade metamorphic complexes and the related granitoids of the Dzabkhan terrane basement are considered. The age data (U–Pb method, TIMS) of zircons from the trondhjemite block of the eastern part of the Dzabkhan terrane, which is directly overlain by the dolomite sequence of the Tsagaan Oloom Formation, are given. Trondhjemites yield the U–Pb zircon age of 862 ± 3 Ma. In their structural position, they are assigned to typical postmetamorphic formations that determine the formation and cratonization of rocks of the host block. The geochronological study of trondhjemites gives grounds to distinguish fragments of the continental crust in the Dzabkhan terrane basement, the formation of which occurred at different periods of time: ～860 and ～790 Ma. Geological–geochronological and Sm?Nd isotope–geochemical studies indicate that the Dzabkhan terrane basement is not a single block of the Early Precambrian continental crust, but a composite terrane, comprising Neoproterozoic ensialic and island-arc structural and compositional complexes. Correlation of Sr isotopic characteristics with the ⁸⁷Sr/⁸⁶Sr variation curve in the Neoproterozoic and Cambrian seawater shows that carbonate deposits accumulated at the eastern margin of the Dzabkhan terrane near the end of the Neoproterozoic, 700–550 Ma, and in the central part of the terrane in the Early Cambrian, 540–530 Ma.  相似文献   

The Upper Age Boundary of the Formation of the Olondo Fragment of the Tokko–Khani Greenstone Belt,Aldan Shield: U–Pb (ID-TIMS) Geochronological Data     

Kovach  V. P.  Kotov  A. B.  Salnikova  E. B.  Popov  N. V.  Velikoslavinsky  S. D.  Plotkina  J. V.  Wang  K.-L.  Fedoseenko  A. M. 《Doklady Earth Sciences》2020,494(2):767-772

Doklady Earth Sciences - This work presents new U–Pb ID-TIMS geochronological data obtained for the rocks of the metagabbro–diorite–tonalite complex of the Olondo fragment of the...  相似文献