2004 Annual Science Report
University of Colorado, Boulder Reporting | JUL 2003 – JUN 2004
Re-Tracing Steps Towards a Habitable World: The Biogeochemical Evolution of Sulfur on the Early Earth.
*Mass-independent isotope effects in sedimentary rocks by ion microprobe analysis.
We and our NAI collaborators at UCLA have reported on a new high-resolution technique using the UCLA Cameca ims1270 ion microprobe in multicollection mode to investigate mass-independent (Δ33S) sulfur isotope variability in a variety of Precambrian sediments including the oldest known rocks of sedimentary origin (Mojzsis et al. (2003) Geochim. Cosmochim. Acta: 67(9), 1635-1658). We have now moved beyond the feasibility stage and are actively engaged in measuring hundreds of samples spanning the “Great Oxygenation Event” between ~2.47 and 2.33 Ga that irreversibly oxidized the surface zone of the planet.
*Discrimination between preservation of original igneous zircon populations and inherited grains.
We described a method whereby the chemistry of a complex metamorphic rock coupled with U/Th ratios in zircon from the same rock permits direct assessment of zircon “inheritance” vs. true igneous ages. The technique has been used to resolve outstanding problems in the genesis of lower crustal rocks that stabilize the continents (Mojzsis et al. (2003) J. Geol. 111(4), 407-425) as well as overcome the long-standing problem of interpreting primary “igneous” ages from overprinted “metamorphic” ages in the oldest rocks. This new methodology is being extended to samples of described pre-3.7 Ga rocks worldwide (Acasta gneisses, Canada; Manfred Complex, Australia; etc.)
PROJECT INVESTIGATORS:Stephen Mojzsis
PROJECT MEMBERS:Nicole Cates
RELATED OBJECTIVES:Objective 1.1
Models of formation and evolution of habitable planets
Sources of prebiotic materials and catalysts
Earth's early biosphere
Effects of extraterrestrial events upon the biosphere
Co-evolution of microbial communities
Biochemical adaptation to extreme environments
Adaptation and evolution of life beyond Earth
Biosignatures to be sought in Solar System materials
Biosignatures to be sought in nearby planetary systems