U-Pb and Lu-Hf isotope systematics of zircons from the Mississippi River sand; implications for reworking and growth of continental crust

We carried out in situ U-Pb and Lu-Hf isotope analyses of detrital zircons from the Mississippi River in order to understand crustal reworking and continental growth rates. The U-Pb analyses for 416 zircons reveal three major peaks of crust formation at 2.8-2.6 Ga, 1.8-0.9 Ga, and after 0.2 Ga. Init...

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Bibliographic Details
Published in:Geology (Boulder) 2005-06, Vol.33 (6), p.485-488
Main Authors: Iizuka, Tsuyoshi, Hirata, Takafumi, Komiya, Tsuyoshi, Rino, Shuji, Katayama, Ikuo, Motoki, Akihisa, Maruyama, Shigenori
Format: Article
Language:English
Subjects:
absolute age
clastic sediments
continental crust
crust
dates
detritus
experimental studies
fluvial environment
Freshwater
Geochronology
Geology
histograms
ICP mass spectra
Isotopes
laser ablation
laser methods
Lead
Lu/Hf
mass spectra
Mississippi River
nesosilicates
orthosilicates
Precambrian
reworking
sand
Sand & gravel
sediments
silicates
spectra
statistical analysis
stream sediments
U/Pb
United States
Uranium
zircon
zircon group
Zirconium
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Summary:We carried out in situ U-Pb and Lu-Hf isotope analyses of detrital zircons from the Mississippi River in order to understand crustal reworking and continental growth rates. The U-Pb analyses for 416 zircons reveal three major peaks of crust formation at 2.8-2.6 Ga, 1.8-0.9 Ga, and after 0.2 Ga. Initial Hf isotope ratios were obtained for 402 of the dated zircons, and only 8% of the zircons have εHf(#ITT#ME)DM values less negative than -2.5. These data correspond to a crustal residence time of
ISSN:0091-7613
1943-2682
DOI:10.1130/G21427.1