Origin of dioctahedral smectites in Lower Eocene Lulehe Formation paleosols (Qaidam Basin, China)

Elevated physical weathering exceeds chemical weathering of clays during the Paleocene-Eocene Thermal Maximum in the continental Bighorn Basin (Wyoming, USA)

“…A subset of 166 whole-rock paleosol samples was manually ground to powder (finer than 0.074 mm) using an agate mortar and pestle. Preparation of oriented clay samples and ethylene glycol (EG) saturated clay samples followed the method of Jackson (1975) and Zhao et al (2021). During the procedure, about 150 mLbuffer solution (CH 3 COONa⋅3H 2 O and CH 3 COOH) and 15 mL 30% H 2 O 2 were used to remove carbonates and organic matter from the whole powder samples, respectively.…”

“…Before best-fit can be obtained, the crystal-chemical curves for each clay mineral were adjusted. The detailed process for setting of parameters for smectites, illite, and I/S can refer to Zhao et al (2021). Peak of kaolinites at ~7.2 Å was fitted by two types of kaolinites with "smaller and larger" mean crystallite thickness at 7.30 and 7.16 Å, respectively.…”

Trends and Transitions in Silicate Weathering in the Asian Interior (NE Tibet) Since 53 Ma

“…This sedimentary archive can provide a continuous record of the response of silicate weathering to the weak uplift of the NE Tibetan Plateau during the Paleogene and rapid uplift during the Neogene (Tapponnier et al, 2001;Yang et al, 2021a). During the past decade, multiple long-term records of silicate weathering history have been acquired from the NE Tibetan Plateau and the adjacent Chinse Loess Plateau, based on element ratios (Song et al, 2013;Sayem et al, 2018;Bao et al, 2019;Ren et al, 2020) and clay minerals (Zhang and Guo, 2014;Sun et al, 2015;Zhang C. et al, 2015;Fang et al, 2016a;Song B. et al, 2018;Ye et al, 2018;Fang et al, 2019b;Liu et al, 2019;Yang et al, 2019;Liu et al, 2020;Ye et al, 2020;Yang et al, 2021b;Zhao et al, 2021). However, the available silicate weathering records from the region are fragmentary because they are derived from diverse time intervals from multiple sections/basins, and they lack comparability due to the use of different elements and minerals.…”

Competitive ion-exchange reactions of Pb(II) (Pb2+/PbCl+) and Ra(II) (Ra2+) on smectites: Experiments, modeling, and implication for 226Ra(II)/210Pb(II) disequilibrium in the environment.

“…Then, to assess: (i) the possible difference in the adsorption properties of Ra(II) and Pb(II) for a swelling clay mineral at low aqueous Pb concentrations (i.e., <10 -10 M), and (ii) discuss these results in the context of 226 Ra(II)/ 210 Pb(II) natural disequilibrium measurements, this study will compare adsorption data previously published for Ra(II) (Robin et al, 2017) with those obtained in the present study for Pb(II) for a Na-beideillite (i.e., a low charge swelling clay). This clay mineral is commonly found in natural environments (Robin et al,2020(Robin et al, , 2015aZhao et al, 2021), and its ion-exchange properties, based on multiple sites, for the main cations of natural waters (i.e., Na + , K + , Ca 2+ and Mg 2+ ) are also well known (Robin et al, 2015b). This last characteristic allows us to test its predictive capacity in several environmental conditions (Ballini et al, 2020;Besançon et al, 2020;de Boissezon et al, 2020;Robin et al, 2020Robin et al, , 2017.…”