|Hf isotope ratios of marine sediments and Mn nodules: evidence for a mantle source of Hf in seawater|
White, W.M.; Patchett, J.; BenOthman, D. (1986). Hf isotope ratios of marine sediments and Mn nodules: evidence for a mantle source of Hf in seawater. Earth Planet. Sci. Lett. 79(1-2): 46-54
In: Earth and Planetary Science Letters. Elsevier: Amsterdam. ISSN 0012-821X; e-ISSN 1385-013X, meer
Ferromanganese nodules; Hafnium isotopes; Sedimentchemie; Sedimentsamenstelling; Marien
|Auteurs|| || Top |
- White, W.M.
- Patchett, J.
- BenOthman, D.
Hf isotope ratios are reported for 6 Mn nodules and 15 other sediments, including siliceous oozes, red clays and terrigenous sediments. Overall, epsilonHf ranges from -19.8 to +3.5, but only from +0.4 to +3.5 in the Mn nodules. The Indian and Atlantic nodules have epsilonHf values (+0.4 and +0.9) which are only slightly lower than values from Pacific nodules (+1.9 to +3.5). The positive epsilonHf values of the Mn nodules indicate much, and perhaps most, of the Hf in seawater is derived from some "mantle" source such as ocean ridge hydrothermal activity, low-temperature alteration of the oceanic crust, or weathering of the young volcanic terranes of the circum-Pacific region. The dominance of "mantle" sources of Hf may result from a very low flux of Hf from the continents rather than a particularly high volcanic one. A low continental flux may result from retention of Hf in zircon, a mineral which is very resistant to weathering. The near uniformity of Hf in nodules from various oceans suggests a longer seawater residence time for Hf than for Nd, probably because Hf is not readily scavanged by particulate matter.