| Autor: |
Godfrey, LV, Zimmermann, B, Lee, D-C, King, RL, Vervoort, JD, Sherrell, RM, Halliday, AN |
| Jazyk: |
angličtina |
| Rok vydání: |
2016 |
| DOI: |
10.1029/2009gc002508 |
| Popis: |
The 176Hf/177Hf ratio of seawater is measured directly with 143Nd/144Nd in a composite vertical profile in the NE Atlantic. The value of εHf of intermediate and deep water exhibits little variation and averages +1.0 ± 0.8; surface water shows a wider range,-5.7 to +3.3. While intermediate and deep water samples plot on, or close to, the seawater Hf-Nd isotope array, defined by ferromanganese deposits, near-surface seawater samples plot between the seawater and terrestrial rock εHf-εNd arrays. It is likely that the shallow water variability in εHf arises from a short residence time of Hf in surface water and isotopically heterogeneous inputs. The difference between surface and intermediate-deep water εHf may be maintained by the release of surface scavenged Hf at depth from a subset of sinking particles; the composition of εNd at middepths reflects overlying surface water and water advected along isopycnals from areas where they outcrop in winter. Uniform εHf values below 1000 m suggest the residence time of Hf may be longer than that of Nd. The radiogenic isotopic composition of seawater Hf relative to Nd and terrestrial rocks suggests that minerals with high Lu/Hf ratios may be preferentially weathered, providing a source of radiogenic Hf to the oceans. © 2009 by the American Geophysical Union. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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