Zircon effect alone insufficient to generate seawater Nd-Hf isotope relationships.

Chen, Tianyu, Ling, Hong-Fei, Frank, Martin, Zhao, Kui-Dong and Jiang, Shao-Yong (2011) Zircon effect alone insufficient to generate seawater Nd-Hf isotope relationships. Open Access Geochemistry, Geophysics, Geosystems, 12 (5). Q05003. DOI 10.1029/2010GC003363.

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Abstract

[1] Many studies have suggested that continental weathering inputs have controlled the dissolved oceanic budget of hafnium (Hf). However, whether the offset of seawater Nd‐Hf isotope compositions from the terrestrial array can be fully generated by incongruent weathering of continental rocks (the zircon effect) is still not well constrained. In recent years, an increasing amount of combined U‐Pb ages and Hf‐isotopic compositions of riverine detrital zircons have been published. Here a new model of the Nd‐Hf isotopic compositions of the weathered zircon‐free part of the upper continental crust is presented, which is based on published Hf isotope compositions and formation ages of modern riverine detrital zircons combined with Nd isotopic compositions of rocks from the upper continental crust. Our model results indicate that the Nd‐Hf isotopic composition of the weathered zircon‐free part of the upper continental crust is not consistent with the seawater isotopic compositions. This suggests that the elevated seawater Hf isotope compositions for given Nd isotope compositions cannot be fully explained by incongruent zircon weathering of the continents, which is also supported by a recent study demonstrating incongruent weathering of other minerals than zircon.

Document Type: Article
Keywords: Marine chemistry; Zircon effect; Hf‐Nd isotopes; seawater array; continental weathering; Radiogenic isotope geochemistry; Marine geochemistry; Geochemical modeling
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2010GC003363
ISSN: 1525-2027
Projects: Future Ocean
Date Deposited: 10 Nov 2011 11:12
Last Modified: 13 Mar 2018 10:03
URI: http://oceanrep.geomar.de/id/eprint/12544

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