FluidNET Science Conference Abstract - Tracing the early stages of secondary clay formation using Li isotopes
Creators: name: Andrea Billarent-Cedillo
name: X.Y. Zhang
name: Helen E. King
name: Oliver Plümper
Publisher: name: Zenodo
Year: 2024

description: Tracing the early stages of secondary clay formation using Li isotopes 

 

Billarent-Cedillo A.*, Zhang X.Y., King H.E., Plümper O. 

Department of Earth Sciences, Faculty of Geosciences, Utrecht University. *a.billarentcedillo@uu.nl

 

The precipitation of clay minerals is an important mechanism for redistributing elements between the hydrosphere and the solid Earth. This process is prevalent in various geological settings, including deep-sea sediments, river deltas, and soils, making secondary minerals a robust tool for tracing processes at Earth’s surface. Despite extensive research on element cycling and isotope partitioning between clay minerals and water in natural systems, only a handful of studies (Hindshaw et al., 2019, Besselink et al., 2020, Lenhardt et al., 2021) have attempted to examine the clay precursors and their impact on the elemental and isotopic signatures of clays. Investigating these early stages of mineralization is important because materials at the Earth’s surface are often poorly crystallized. In this study, we use Li isotopes to assess the reactivity of these clay precursors. Li isotope signature is a powerful tracer to study fluid-rock interaction processes due to its wide range of isotope fractionation at ambient conditions (Misra and Froelich, 2012). A previous study suggested that differences in crystallinity may lead to distinct Li isotope fractionation between fluids and smectite (Vigier et al. 2008). 

 

We synthesized aluminosilicate clay precursors using solutions with variable Si/Al ratios ranging from 0.4 to 2. These solutions were duplicated with the addition of LiCl. We sampled the precipitates formed in the solution and the solution at different time steps over three months. Spectroscopic techniques (Raman, FTIR) and X-ray diffraction (XRD) confirmed the amorphous nature of the solids and revealed differences in the spectrum of precipitates with different Si/Al solutions and within the non-doped and the Li-doped samples. Elemental analysis (ICP-OES and ICP-MS) of the fluid phase shows Li uptake by the amorphous phase varies with Si/Al ratios. The morphology of the clay precursors was further characterized using electron microscopy (SEM and TEM-EDS). Given the small size of the particles (10-50 nm), only TEM-EDS provided insights into the structure and chemical distribution of Al and Si within the nanoparticles. These preliminary results indicate that the initial fluid composition influences the chemistry and the structure of the clay precursors. 

 

References: 

Besselink, R., et al. (2020). Crystal Growth & Design.

Hindshaw, R. S., et al. (2019). Geochimica et Cosmochimica Acta.

Lenhardt, K. R., et al. (2021). Scientific reports.

Misra, S., & Froelich, P. N. (2012). Science.  

Vigier et al. (2008). Geochimica et Cosmochimica Acta.

 

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 956127