Age and Sources of Lower Mesozoic Metasedimentary Rocks of the Un’ya-Bom Terrane in the Mongol–Okhotsk Fold Belt: Results of U–Pb Geochronological (LA-ICP-MS) and Sm–Nd Isotope Studies

2019 ◽  
Vol 484 (2) ◽  
pp. 115-119 ◽  
Author(s):  
V. A. Zaika ◽  
A. A. Sorokin ◽  
V. P. Kovach ◽  
A. P. Sorokin ◽  
A. B. Kotov
Keyword(s):  
Fold Belt ◽  
Nd Isotope ◽  
Metasedimentary Rocks ◽  
Icp Ms ◽  
Isotope Studies

scholarly journals Age and sources of the Lower Mesozoic metasedimentary rocks of the Un'ja-Bom terrane in the Mongol-Okhotsk fold belt: results of the U–Th–Pb geohronological (LA–ICP–MS) AND Sm–Nd isotope studies

2019 ◽  
Vol 484 (4) ◽  
pp. 455-459
Author(s):  
V. A. Zaika ◽  
A. A. Sorokin ◽  
V. P. Kovach ◽  
A. P. Sorokin ◽  
A. B. Kotov
Keyword(s):  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Fold Belt ◽  
Relative Probability ◽  
Nd Isotope ◽  
Metasedimentary Rocks ◽  
Icp Ms ◽  
Isotope Studies ◽  
Geochemical Studies ◽  
Age Estimates

The results of the U—Th—Pb geochronological studies indicate that in the Un’ja-Bom terrane the youngest peaks on the relative probability curves of ages are 207 and 212 Ma for zircons from the metasiltstone of the Kurnal formation and from the metasiltstone of the Amkan formation. Similar age estimates for the youngest peaks were obtained for the detrital zircons from the metasedimentary rocks of the Tukuringra terrain of the eastern part of the Mongol-Okhotsk belt, which indicates that the Lower Mesozoic flyschoid complexes in the structure of this belt are developed much wider than is currently believed. The results obtained in our U—Th—Pb geochronological and Sm—Nd isotope geochemical studies suggest’s that the sedimentary rocks material was carried to the sedimentation basin mainly from the continental massifs of the Amur superterrane.

scholarly journals Age and sources of the metasedimrntary rocks of the Tokur terrane in the Mongol-Okhotsk fold belt: results of the U–Pb geoсhronological and Lu–Hf isotope studies

2019 ◽  
Vol 486 (4) ◽  
pp. 446-450
Author(s):  
V. A. Zaika ◽  
A. A. Sorokin ◽  
A. P. Sorokin
Keyword(s):  
Detrital Zircons ◽  
Hf Isotope ◽  
Fold Belt ◽  
Metasedimentary Rocks ◽  
The North ◽  
Icp Ms ◽  
North Asia ◽  
Southeastern Margin ◽  
Isotope Studies ◽  
Metamorphic Complexes

This paper presents the results of U–Pb (LA–ICP–MS) and Lu–Hf ­isotope studies of detrital zircons from metasedimentary rocks of the Tokur Terrane. It has been shown that metasedimentary rocks of the Tokur and Ekimchan formations are characterized by similar age peaks of detrital zircons, which indicates a close (or same) age of these formations. The lower age of the sedimentation is determined by the age of the youngest zircons of 326–323 Ma. The upper age boundary is determined of 254–251 Ma, based on the intruded of the Late Permian granitoids. The main sources of zircons in the metasedimentary rocks of the Tokur Terrane are the igneous and metamorphic complexes of the southeast framing of the North Asia Craton. The Tokur Terrane can be considered as a fragment of the Paleozoic accretionary complex, the formation in front of the southeastern margin of the North Asia Craton.

scholarly journals AGE AND SOURCES OF PROTOLITHS OF METASEDIMENTARY ROCKS IN THE EASTERN TUKURINGRA TERRANE OF THE MONGOL-OKHOTSK FOLD BELT: RESULTS OF U-TH-PB, LU-HF, AND SM-ND ISOTOPE STUDIES

2021 ◽  
Vol 40 (3) ◽  
pp. 16-27
Author(s):  
V.A. Zaika ◽  
◽  
A.A. Sorokin ◽  
Keyword(s):  
Early Jurassic ◽  
Late Triassic ◽  
Fold Belt ◽  
North Asian Craton ◽  
Nd Isotope ◽  
Metasedimentary Rocks ◽  
Isotope Data ◽  
The North ◽  
Early Mesozoic ◽  
Isotope Studies

The article presents detrital zircon U-Th-Pb and Lu-Hf isotope data for metasedimentary rocks from the eastern Tukuringra Terrane, as well as whole-rock Sm-Nd isotope data. Our analyses show that the zircons in metasedimentary rocks are mostly early Mesozoic in age. Early Paleozoic and Neoproterozoic zircons are also common, whereas early Precambrian zircons are virtually absent. The age of the youngest zircon population places a lower age limit on the age of the Tungalin Formation at 204 Ma (Late Triassic, Rhaetian), the Dugda Formation at 181 Ma (Early Jurassic, Toarcian), and the Tangomen Formation at 189 Ma (Early Jurassic, Pliensbachian). Essentially all Mesozoic, Paleozoic and Neoproterozoic zircons are characterized by Neo- and Mesoproterozoic Hf-model ages (tHf(DM) = 1.41–0.46 Ga, tHf(C) = 1.55–0.49) and Mesoproterozoic Nd-model ages (tNd(DM) = 1.25–1.10 Ga, tNd(С) = 1.31–1.14). Our results suggest that sediments for deposition were sourced mainly from the continental Amuria Superterrane, but not from the southern margin of the North Asian Craton.

scholarly journals The exotic inim block of the argun continental superterrane of the central asian fold belt: results of U-Th-pb geochronological (LA-ICP-MS) and Sm-Nd isotopic-geochemical studies

2019 ◽  
Vol 484 (6) ◽  
pp. 734-738
Author(s):  
R. O. Ovchinnikov ◽  
A. A. Sorokin ◽  
A. B. Kotov ◽  
E. B. Sal'nikova ◽  
V. P. Kovach ◽  
...  
Keyword(s):  
Continental Crust ◽  
Central Asian Fold Belt ◽  
Fold Belt ◽  
Early Precambrian ◽  
Metasedimentary Rocks ◽  
Tectonic Events ◽  
Central Asian ◽  
Icp Ms ◽  
Archean Crust ◽  
Geochemical Studies

The results of studies indicate that the age of the protoliths of garnet-bearing biotite–sericite–muscovite schists of the Inim Block is <991 Ma, and they are derived from rocks of the Neo-, Meso-, and Paleoproterozoic (as well as Archean) crust. This suggests that the Inim Block is exotic relatively to the Argun Superterrane due to the formation of the protolith of its metasedimentary rocks largely from erosion products of the Early Precambrian continental crust, the presence of which within the Argun Superterrane is not proven. It is not excluded that the Inim Block is a fragment of the Dzhugdzhur–Stanovoi Superterrane implanted in the structure of the Argun Superterrane as a result of Mesozoic tectonic events.

scholarly journals Variations of the 238U/235U isotope ratio in metasedimentary rocks and evidence of changes in sedimentation conditions during the Ediacaran period of the Neoproterozoic

2019 ◽  
Vol 484 (4) ◽  
pp. 472-477
Author(s):  
A. V. Chugaev ◽  
I. V. Chernyshev ◽  
A. E. Budyak ◽  
G. V. Mandzhieva ◽  
A. S. Sadasyuk ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Isotope Ratio ◽  
Redox Conditions ◽  
Fold Belt ◽  
Marine Origin ◽  
Metasedimentary Rocks ◽  
Geological Processes ◽  
Terrigenous Rocks ◽  
Icp Ms ◽  
Sedimentation Conditions

The isotopic composition of uranium is a new geochemical indicator that facilitates reconstruction of the redox conditions of geological processes. In this paper the results of study of the 238U/235U isotope ratio in the Neoproterozoic metasedimentary rocks of the Baikal–Patom fold belt (Northern Transbaikalia) were obtained using the MC-ICP-MS method and 233U+236U double spike. The scale of 238U/235U ratio variations (δ238U = –0.37 to –0.11‰) is within the range of (–0.39 to +0.15‰), typical of metasedimentary terrigenous rocks of marine origin. In terms of the δ238U values, uranium of the BPB rocks studied is heavier than seawater uranium (δ238U = –0.41 ± 0.03). There is a correlation between the δ238U value in the rocks and their position in the stratigraphic section. Variations of the 238U/235U ratio in the terrigenous-carbonate sequences of BPB indicate that the sedimentation conditions changed and euxinic conditions were established in the course of evolution of the paleobasin in the Late Ediacarian Period.

scholarly journals Age and origin of fluorapatite-rich dyke from Baranec Mt. (Tatra Mts., Western Carpathians): a key to understanding of the post-orogenic processes and element mobility

2016 ◽  
Vol 67 (5) ◽  
pp. 417-432 ◽  
Author(s):  
Aleksandra Gawęda ◽  
Krzysztof Szopa ◽  
David Chew ◽  
Urs Klötzli ◽  
Axel Müller ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Tatra Mountains ◽  
Nd Isotope ◽  
Metasedimentary Rocks ◽  
Partial Melt ◽  
Icp Ms ◽  
Mineral Assemblages ◽  
Tatra Mts ◽  
Crustal Origin ◽  
Nd Isotope Composition

AbstractOn the southeastern slope of the Baranec Mount in the Western Tatra Mountains (Slovakia) an apatite-rich pegmatite-like segregation was found in the subvertical fault zone cutting metapelitic rocks. Two zones: felsic (F) and mafic (M) were found, differing in mineral assemblages and consequently in chemistry. Fluorapatite crystals yield a LA-ICP-MS U-Pb age of 328.6 ± 2.4 Ma. A temperature decrease from 634 °C to 454 °C at a pressure around 500 to 400 MPa with oxygen fugacity increasing during crystallization are the possible conditions for formation of the pegmatite-like segregation, while secondary alterations took place in the temperature range of 340 – 320 °C. The Sr-Nd isotope composition of both apatite and whole rock point toward a crustal origin of the dike in question, suggesting partial melting of (P, F, H2O)-rich metasedimentary rocks during prolonged decompression of the Tatra Massif. The original partial melt (felsic component) was mixed with an external (F, H2O)-rich fluid, carrying Fe and Mg fluxed from more mafic metapelites and crystallizing as biotite and epidote in the mafic component of the dyke.

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