Neutron computed tomography reconstructions of microbial structures in carbonate and silicate rocks.

by
Wilding, M C, Sumner, D. Y, Lesher C. E.
Department of Geology, University of California at Davis, Davis, CA 95616 United States

Shields, K E, Reap, D, Richards, W J
McClellan Nuclear Radiation Center, 5335 Price Avenue, McClellan, CA

2002, Astrobiology Science Conference, Abstracts


Neutron computed tomography (CT) is a relatively new technique that shows great promise for the non-destructive imaging of organic materials in rocks. Neutron CT, which is analogous to X-ray CT, uses computer algorithms to reconstruct the three-dimensional structure of a sample from a series of N radiographs. The strength of N-CT for imaging biological structures comes from its sensitivity to light elements, especially hydrogen and carbon. Thus, it is a technique that will enhance studies of endolithic and fossil microbial communities, particularly in conjunction with X-ray CT, which is sensitive to heavy elements. N-CT techniques developed at the UC Davis McClellan Nuclear Radiation Center are being refined to obtain the maximum contrast and spatial resolution for organic materials in rock. Transmission intensity tables for water, carbonate, silicates, and organics demonstrate that their scattering profiles are sufficiently different to allow high resolution imaging of the distribution of hydrogen and carbon in diverse rock types. Results to date include detailed images of: 1) organic and fluid inclusions in Neoarchean calcitic microbialites; 2) modern endolithic mircobial communities in calcite; 3) the distribution of water-wetted surfaces in sand; and 4) various experimental combinations of carbonate, organic carbon, and graphite.



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Dawn Y. Sumner
Department of Geology
University of California
Davis, CA 95616
sumner@geology.ucdavis.edu

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