TRAPDOR experiments on siliceous sinters from thermal springs
EMSL Project ID
4698a
Abstract
This study proposes to accumulate preliminary data documenting the atomic environment of silicon in thermal spring deposits. These ?siliceous sinters? form at low temperatures (30 to 105 C), under different pH (generally 6 to 9) and water chemistry conditions. Since siliceous sinters are an important site for the preservation of microfossils of ancient microbial lineages, understanding how and when microfossils are preserved in the geological record is critical to unraveling the authenticity of purported fossil organisms. Solid-state silicon, aluminum, and boron NMR spectra are distinct for siliceous sinters formed in different locations and under different thermal and chemical environments. This is known from studies conducted in summers 2002 and 2003. Most recently, cross-polarization experiments with silicon showed two dominant types of silicon environments, Q2 and Q3. Both sites have significant amounts of silanol groups in network modifying sites but it is not know whether other ions populate neighboring cation sites. Other cations could modify the silica network either by terminating silicate chains or by substituting for silicon in the structure. Hypothetically, if consistent differences are noted in the number and type of neighboring cations, then subsequent silica phase transition rates would be affected. This is important in the potential preservation of microfossils from thermal spring environments. Elements of interest are Al, B, Na and C. I propose to use TRAPDOR experiments to determine whether these elements, in addition to protons, occupy nearest neighbor sites in the silicate matrix. Al and B would be network formers, while Na would be a network modifier. C would offer the opportunity to investigate whether silica links directly to microbial surfaces or merely adsorbs to them.
To this end, I propose a limited series of experiments using a small set (4 to 6) samples. TRAPDOR experiments would be conducted by monitoring Si-29 NMR while simultaneously irradiating the sample with Al, B, C or Na resonance frequencies. Potential problems arise because of the proximity of Si-29 and the other resonance frequencies.
Project Details
Project type
Capability Research
Start Date
2004-10-28
End Date
2007-07-18
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Hinman NW, and JM Kotler. 2013. "Aluminum in Silica Phases Formed in Hot Springs." In Aluminum in Silica Phases Formed in Hot Springs, vol. 7, pp. 365-368. Procedia - Earth and Planetary Science, Missoula, MT. doi:10.1016/j.proeps.2013.03.078