Vigier, N.; Burton, K.W.; Gislason, S.R.; Rogers, N.W.; Duchene, S.; Thomas, L.; Hodge, E. and Schaefer, B.
|DOI (Digital Object Identifier) Link:||http://dx.doi.org/10.1016/j.epsl.2006.07.001|
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U-series isotopes have been measured in the dissolved phase, suspended load and bedload of the main rivers draining basaltic catchments in Iceland. For the dissolved phase, (234U/238U) and (238U/230Th) range between 1.08 and 2.2, and 7.4 and 516, respectively. For the suspended load and bedload, (234U/238U) and (238U/230Th) range from 0.97 to 1.09 and from 0.93 to 1.05, respectively. Chemical erosion rates, calculated from dissolved major elements, range between 13 and 333 t km− 2 yr− 1. Physical erosion rates have also been estimated, from existing data, and range between 21 and 4864 t/km2/yr, with an average of 519 t km− 2 yr− 1. U-series disequilibria indicate that weathering in Iceland operates at close to steady-state conditions. A model of continuous weathering indicates a maximum weathering timescale of 10 kyr, with an average rate of uranium release into water of 1.6 · 10− 4 yr− 1, which is significant when compared to granitic terrains located at similar latitudes and to tropical basaltic terrains. All river waters display (234U/238U) greater than secular equilibrium, consistent with the effects of alpha-recoil. The same dissolved phase (234U/238U) exhibit a negative trend with physical erosion rates, explained by the dominant effect of close-to-congruent chemical weathering of hyaloclastites in the younger basaltic terrains. Therefore, chemical erosion rate and mineral weathering susceptibility play a major role in determining 234U–238U disequilibria in basaltic river waters. Comparison of global data for river basins in which weathering was recently strongly limited indicates a negative correlation between silicate weathering rates estimated with major elements and the age of weathering estimated with U-series disequilibria. This strongly suggests a key role of time and soil thickness on the chemical erosion of silicates.
|Item Type:||Journal Article|
|Keywords:||U-series disequilibria; Iceland; basalt; erosion; weathering timescale; steady-state|
|Academic Unit/Department:||Science > Environment, Earth and Ecosystems
|Interdisciplinary Research Centre:||Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)|
|Depositing User:||Astrid Peterkin|
|Date Deposited:||26 Mar 2007|
|Last Modified:||14 Jan 2016 16:29|
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