Source versus weathering processes as controls on the Mackenzie river uranium isotope signature ...

• Main Authors: Charbonnier, Quentin, Clarkson, Matthew O., Hilton, Robert G., Vance, Derek
• Format: Text
• Language: English
• Published: ETH Zurich 2023
• Subjects: Weathering; Mackenzie Basin; Uranium stable isotopes; Mackenzie river
• Online Access: https://dx.doi.org/10.3929/ethz-b-000606143; http://hdl.handle.net/20.500.11850/606143

Uranium (U) isotope signatures (δ238U) recorded in sedimentary archives provide insight into the paleo redox state of the ocean. But the robust interpretation of these sedimentary U isotope records requires characterisation of the U isotope signature of rivers, the main source of U to the ocean. The main controlling factors on riverine δ238U remain poorly constrained. Here, we investigate the elemental and isotope signatures of uranium in the dissolved and solid loads of a well-characterised river, the Mackenzie Basin (Canada). In the Mackenzie Basin, the solid load δ238U shows a positive relationship with U and vanadium (V) contents, consistent with the suggestion that particulate δ238U are explained by variable contributions via erosion of silicate and black shale. The δ238U of the dissolved and solid loads are correlated which, at first sight, suggests no U isotope fractionation during chemical weathering, and a purely lithological control on both the river dissolved and solid δ238U. Moreover, ... : Chemical Geology, 625 ...