Collaborative Research: Improving and calibrating a Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) system for clumped isotope analysis of CO2

University Of Washington, Seattle WA

Investigators

Abstract

The study of “clumped-isotopes” concerns the tendency of heavy isotopes to “clump” into bonds with each other rather than with light isotopes in natural materials, a tendency that is temperature dependent. The co-occurrence of two rare and more massive isotopes of carbon and oxygen clumped in CO2 holds information on the temperature of the most recent chemical reactions involving these molecules. Clumped-isotope geochemistry has been applied to a wide range of subjects – from constraining atmospheric CO2 budgets to the temperature histories of meteorites. Measurements of clumping in CO2 have enabled new advances in reconstructing hydrothermal systems, climate history, paleoelevation, and the cooling history of the upper crust. The primary reason that this methodology is not more widely practiced is the difficulty of the measurement. This award will deliver a new laser-based instrument for measurement of clumped isotopes in carbonates that is much faster, cheaper, and requires less sample material than existing mass spectrometer systems. This new instrument will completely alter the landscape for clumped isotope research, making it a commonplace analysis. Such a system would be adopted quickly by laboratories around the world for application to geologic, oceanographic, biologic, and atmospheric samples, leading to new research possibilities in many scientific disciplines. This project also expands training and educational opportunities in this unusual sub-discipline of geochemistry. This project will support a postdoctoral researcher, strengthen international collaborations, and disseminate results through a conference session on laser methods. The project will also integrate research and education, broaden the participation of underrepresented groups, and broadly disseminate results by supporting a STEM Futures Fellowship research experience for undergraduates who identify with historically underrepresented groups in geoscience. This project builds on our previous funded work to develop a working laser-based (Tunable Infrared Laser Direct Absorption Spectroscopy - TILDAS) instrument for the rapid and precise measurement of clumped isotopologues of CO2 (e.g., 13C18O16O). The basic instrument has been constructed, but additional improvements in stability and development of practical sample processing are needed to produce an instrument that can be used widely in the scientific community. This laser-based measurement has major advantages over the currently used mass spectrometry approach in that it is much faster, taking only 20 minutes of analysis to achieve the required precision. Small sample size (comparable to the smallest mass spectrometer systems, and with the potential for further reductions) and a major increase in through-put will allow geochemists to extract previously unobtainable detailed temperature information from finely layered archives such as shell, fish otoliths, speleothems, soil carbonates, tufas and travertines. Fine sampling will also allow researchers to more effectively dissect diagenetic histories in carbonates, address questions related to solid-state reordering, study zoned fracture-filling cements precipitated in the sub-surface, and study kinetic and vital effects. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.