Atomic-level investigations of thermal spring deposits: S-NMR of natural siliceous sinters
EMSL Project ID
3318
Abstract
We propose a nuclear magnetic resonance (NMR) study of naturally occurring silica minerals and experimentally produced solids to examine the ultrastructure of silica minerals in hydrothermal systems. Our work also will include a study of the role of organic matter in structuring silica and the role of silica in structuring organic matter. Solid state CP-MAS NMR (cross-polarization - magic-angle spinning, nuclear magnetic resonance) nuclear magnetic resonance spectra of H and Si will be gathered and interpreted to identify short-term and persistent signatures of the reciprocal interaction of silicon with organic matter. Spectra of C and O my also be useful in describing silica ultrastructure. In an earlier version, this proposal focused solely on the search for tetrahedral aluminum in siliceous sinters. During the summer of 2002, a preliminary study of Al in siliceous sinters revealed the very interesting result that only tetrahedral Al is present. We had expected to see some octahedral Al but unfortunately, undetected background signals obscured the octahedral Al signal and we cannot be certain whether it is present. Given the relative strength of the tetrahedral signal, we determined that the remaining signal is be attributed to background. The results have been submitted as part of a proposal to the General Meeting of the NASA Astrobiology Institute and will be presented in February 2003 (Hinman et al., 2003). However, Si NMR revealed interesting results for the few samples analyzed. The experiments for Si NMR required 24-hour collection times and so few spectra were obtained. Nevertheless, peak width and shift differed among samples. It is this aspect that we propose to pursue. This proposal, therefore, is for a renewal of instrument access time. The 400 Varian Unity Plus NMR resides in the Chemistry Department. The instrument is dominantly used for liquids and is fairly heavily used. Solids have not been analyzed on the instrument for over three years and may cause significant down-time. I am requesting 1 week of time on the CMX 300 WB for solids.
Project Details
Project type
Capability Research
Start Date
2003-08-06
End Date
2004-08-10
Status
Closed
Released Data Link
Team
Principal Investigator