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

Tsuyoshi Iizuka, Takafumi Hirata, Tsuyoshi Komiya, Shuji Rino, Ikuo Katayama, Akihisa Motoki, Shigenori Maruyama

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134 Citations (Scopus)

Abstract

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(T)DM values less negative than -2.5. These data correspond to a crustal residence time of Hf(T)DM population demonstrates that reworking was predominant at 2.5-2.0 Ga and after 0.9 Ga, whereas juvenile crust formation dominated between 2.0 and 1.6 Ga. We calculated the mantle-extraction model ages to estimate the continental growth rate. Approximately half of the grains have model ages between 2.0 and 1.3 Ga, indicating rapid crustal growth during this time. The continental growth rate suggests that 15% and 78% crust in the source region of the zircons formed by 2.5 and 1.3 Ga, respectively.

Original languageEnglish
Pages (from-to)485-488
Number of pages4
JournalGeology
Volume33
Issue number6
DOIs
Publication statusPublished - Jun 2005
Externally publishedYes

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Keywords

  • Continental growth
  • Crustal reworking
  • Laser ablation-ICP-MS
  • Lu-Hf
  • U-Pb
  • Zircon

ASJC Scopus subject areas

  • Geology

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