The first results of U/Pb dating and isotope geochemical studies of detrital zircons from the neoproterozoic sandstones of the Southern Timan (Djejim-Parma Hill) |
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Authors: | Kuznetsov N B Natapov L M Belousova E A Griffin U L O’Relly S Y Kulikova K V Soboleva A A Udoratina O V |
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Institution: | (1) Staatliche Naturhistorische Sammlungen Dresden, Museum für Mineralogie und Geologie, Königsbrücker Landstrasse 159, 01109 Dresden, Germany;(2) Centre for Global Metallogeny, School of Earth and Geographic Sciences, University of Western Australia, 6009 Nedlands, Western Australia , Australia;(3) GeoForschungsZentrum Potsdam, Telegrafenberg, 14474 Potsdam, Germany;(4) Staatliche Naturhistorische Sammlungen Dresden, Museum für Mineralogie und Geologie, Königsbrücker Landstrasse 159, 01109 Dresden, Germany |
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Abstract: | This report presents the first results of U/Pb dating, isotope-geochemical, and geochemical studies of detrital zircons from
the Neoproterozoic clastic rocks of the Southern Timan. Sixty-one zircon grains were treated, including 51 from red-colored
sandstones and 10 grains from aleurosandstones of the Djejim Formation of the southern Chetlas-Djejim zone (Djejim-Parma Hill).
It was found that the U/Pb-ages of zircons from the rocks of the Djejim Formation, varied from ∼2.97 to ∼1.20 Ga. The studies
of microelement composition in 47 grains (of 61 U/Pb isotope ages obtained), on the basis of several empirical regularities
found formerly, show that the detrital zircons had originated from “granites” (22 grains), “diorites” (12 grains), or their
volcanic analogues, or more rarely, from “syenites” and “basites” (5 and 8 grains, respectively). The Lu/Hf isotope system
of zircons allows one to estimate the model ages (T
DMC) of the substrate magmatic rocks being parental to the zircons considered. In particular, Archean zircons are characterized
by ∼2.84–3.36 Ga model ages of magmaforming rocks. For some of the grains, their model ages (∼2.84 Ga) are close to those
of zircons as such (∼2.7–2.8 Ga), which points to the juvenile character of the substrate from which the parent magma of the
zircons treated was fused. For Proterozoic (to Middle Riphean) zircons, the Lu/Hf isotope system allows one to estimate the
model age of the substrate of their parental rocks within ∼2.00–3.36 Ga, which shows that these rocks were formed under the
recycling of the Archean and Early-Proterozoic crust. The ages obtained for detrital zircons, as well as model ages of the
substrate of the corresponding parental magmatic rocks, are quite comparable to the age of crystalline complexes of the ancient
framework of the East European Platform (EEP), formed in the course of the Archean, Early-Proterozoic, and Early-Middle Riphean
tectonomagmatic events. This permits us to conclude that the Neoproterozoic detrital complexes of the Timan were formed owing
to the erosion of earlier Neoproterozoic and Early Precambrian complexes constituting the Neoproterozoic Baltica continent,
presenting complexes of the passive margin of this continent. A variety of ages of detrital zircons from sandstones and aleurosandstones
from the Djejim Formation of Djejim-Parma Hill, and of the estimates of magmatic rocks parental to these zircons, may be characterized
as a Baltic Provenance signal. |
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