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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.

4 Institutions
3 Teams
0 Publications
0 Field Sites
Field Sites

Project Progress

*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.)

    Stephen Mojzsis Stephen Mojzsis
    Project Investigator
    Nicole Cates
    Doctoral Student

    Dominic Papineau
    Doctoral Student

    Dustin Trail
    Graduate Student

    Heather Sickels
    Undergraduate Student

    Objective 1.1
    Models of formation and evolution of habitable planets

    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 4.1
    Earth's early biosphere

    Objective 4.3
    Effects of extraterrestrial events upon the biosphere

    Objective 5.2
    Co-evolution of microbial communities

    Objective 5.3
    Biochemical adaptation to extreme environments

    Objective 6.2
    Adaptation and evolution of life beyond Earth

    Objective 7.1
    Biosignatures to be sought in Solar System materials

    Objective 7.2
    Biosignatures to be sought in nearby planetary systems