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Growth rate of the preserved continental crust: II. Constraints from Hf and O isotopes in detrital zircons from Greater Russian Rivers

Citation

Wang, CY and Campbell, IH and Stepanov, AS and Allen, CM and Burtsev, IN, Growth rate of the preserved continental crust: II. Constraints from Hf and O isotopes in detrital zircons from Greater Russian Rivers, Geochimica et Cosmochimica Acta, 75, (5) pp. 1308-1345. ISSN 0016-7037 (2011) [Refereed Article]

Copyright Statement

Copyright 2011 Elsevier

DOI: doi:10.1016/j.gca.2010.12.010

Abstract

Detrital zircons from the Ob, Yenisey, Lena, Amur, Volga, Dnieper, Don and Pechora rivers have been analyzed for U–Th–Pb, O and Lu–Hf isotopes to constrain the growth rate of the preserved continental crust in Greater Russia. Four major periods of zircon crystallization, 0.1–0.55, 0.95–1.3, 1.45–2.0 and 2.5–2.9 Ga, were resolved from a compilation of 1366 zircon U/Pb ages. The Archean zircons have δ18O values lying between 4.53‰ and 7.33‰, whereas Proterozoic and Phanerozoic zircons have a larger range of δ18O values in each of the recognized U/Pb time intervals with maximum δ18O values up to 12‰. We interpret the zircons with δ18O between 4.5‰ and 6.5‰ to have been derived from a magmatic precursor that contains little or no sedimentary component. The variable δ18O values of the zircons were used to constrain the 176Lu/177Hf ratios of the crustal source region of the zircons, which, in turn, were used to calculate Hf model ages (TDMV). The crustal incubation time, the time difference between primitive crust formation (dated by TDMV) and crustal melting (dated by zircon U/Pb age), varies between 300 to 1000 Myr for the majority of analyzed zircon grains, but can be up to 2500 Myr. The average TDMV Hf model age weighted by the fraction of zircons in the river load is 2.12 Ga, which is in reasonable agreement with the area-weighted average of 2.25 Ga. The TDMV Hf model age crustal growth curve for zircons with mantle-like δ18O values (4.5–6.5‰), weighted by area, shows that growth of the Great Russian continental crust started at 4.2 Ga, and that there are two principal periods of crustal growth, 3.6–3.3 Ga and 0.8–0.6 Ga, which are separated by an interval of low but more or less continuous growth. An alternative interpretation, in which the average 176Lu/177Hf ratio (0.0115) of the continental crust is used for the Paleoproterozoic zircons from the Lena River, lowers the average TDMV age of these grains by about 500 Myr and delays the onset of significant crustal growth to 3.5 Ga.
   The two principal growth periods recognized in Greater Russia differ from those identified from the Gondwana and the Mississippi river basin, which show peaks at 1.7–1.9 and 2.9–3.1 Ga (Hawkesworth and Kemp, 2006a) and 1.6–2.2 and 2.9–3.4 Ga (Wang et al., 2009), respectively. The older 3.6–3.3 Ga or 3.5–3.3 Ga peak for Greater Russia is slightly older than the older Gondwana-Mississippi peaks, whereas the younger 0.8–0.6 Ga peak is distinctly younger than the youngest peak in either Gondwana or the Mississippi river basin. This suggests that the two major peaks of crustal growth identified in Gondwana and the Mississippi river basin may not be global periods of enhanced continental growth and that the major periods of crustal growth may differ from continent to continent.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geochemistry
Research Field:Inorganic Geochemistry
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Mineral Exploration
Objective Field:Mineral Exploration not elsewhere classified
Author:Stepanov, AS (Mr Sasha Stepanov)
ID Code:95751
Year Published:2011
Web of Science® Times Cited:34
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2014-10-08
Last Modified:2017-11-02
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