Mogk, David W.

Dr. David W. Mogk

Associate Professor
Department of Earth Sciences
Montana State University
Bozeman, MT
Research Overview

TBI supported the Master's thesis work by Braden Hannah (completed Spring, 2003), supervised by David W. Mogk. This work was focused on characterization of the mineralogy of acid-sulfate hot springs known to host Sulfolobus from the Rabbit Creek and Ragged Hills (Norris Geyser Basin) areas in Yellowstone National Park. Field work included: detailed mapping of the physical distribution of hot springs and related features in these areas; regular sampling of natural waters for geochemical analysis; monitoring temperature and pH of the natural waters; and collection of mineral samples from sediments suspended in the spring waters, from the pool basins, and from surrounding soils. Analytical studies included scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis of the mineral species, including imaging of mineralogical textural features and their relations to microbes and their biofilms. The Rabbit Creek mineralogy includes kaolinite, hematite and varieties of silica species (quartz, opal-A, opal-C, and opal CT), whereas the Ragged Hills location also contains alunite. Residual volcanic glasses also are host to trace minerals such as apatite, zircon, and ilmenite. Analysis of differing grain sizes shows that the finest suspended particles are typically opal-A (i.e. disordered), whereas coarser fractions in the water column and basin sediments contain also opal C or CT and ordered quartz.

Complementary experimental studies (in progress) are investigating the relationship of specific mineral phases (sulfur, quartz, opal, hematite, and kaolinite) as potential substrates for microbial attachment, and as possible sources of nutrients, energy, and metabolic by-products. Further characterization of natural mineral species and geochemical analysis of natural waters will continue to develop baseline databases from which to compare seasonal and long-term variation of the physico-chemical state of these systems. More detailed mineralogical studies are in progress. In addition, analytical studies will expand to include Time-of- Flight SIMS analysis of mineral substrates to search for diagnostic biomarkers; X-ray photoelectron spectroscopy to determine chemical state of the surfaces of mineral substrates; and atomic force microscopy to obtain more detailed images of the surfaces of minerals, particularly where these surfaces may be mediated by microbial attachment