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The distribution of (234U/238U) activity ratios in river sediments
Geochimica et Cosmochimica Acta ( IF 5 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.gca.2020.09.007
Maude Thollon , Germain Bayon , Samuel Toucanne , Anne Trinquier , Yoan Germain , Anthony Dosseto

Abstract Uranium (U) isotopes can be used to estimate the comminution age of sediments, i.e. the time elapsed from sediment production on continents, via weathering and physical erosion, to deposition in the sedimentary record. The calculation of this comminution age is based on measured (234U/238U) activity ratios in river sediments, and inferred time-dependent recoil effect, which leads to the preferential release of 234U from mineral lattices during erosion processes. In this study, we report on a large-scale (234U/238U) investigation of modern river sediments worldwide, with the aim to determine the extent to which parameters such as grain size, lithology, weathering, climate and geomorphology may influence the distribution of U isotopes in fine-grained sediments. Our extensive dataset (N = 64) includes U isotopic measurements for many of the world’s largest rivers, but also rivers draining particular climatic and geological settings. Our results indicate that sediments collected from river basins draining mostly igneous, metamorphic or volcanic rocks often display (234U/238U) ratios > 1, with clay-size fractions (

中文翻译:

河流沉积物中(234U/238U)活度比的分布

摘要 铀 (U) 同位素可用于估计沉积物的粉碎年龄,即从大陆上的沉积物产生,通过风化和物理侵蚀,到沉积记录中的沉积所经过的时间。该粉碎年龄的计算基于河流沉积物中测量的 (234U/238U) 活动比,以及推断的随时间变化的反冲效应,这导致 234U 在侵蚀过程中从矿物晶格中优先释放。在这项研究中,我们报告了对全球现代河流沉积物的大规模 (234U/238U) 调查,目的是确定粒度、岩性、风化、气候和地貌等参数对河流沉积物分布的影响程度。细粒沉积物中的 U 同位素。我们广泛的数据集 (N = 64) 包括世界上许多最大河流的 U 同位素测量值,但也包括排放特定气候和地质环境的河流。我们的结果表明,从主要排放火成岩、变质岩或火山岩的河流流域收集的沉积物通常显示 (234U/238U) 比率 > 1,粘土粒度分数(
更新日期:2020-12-01
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