Life in the volcanic crust of the early Earth: conditions, timing and depth

Over the past decade, our group has provided convincing evidence that alteration of basaltic glass in pillow lavas of modern and ancient oceanic crust is partially controlled by microbial activity. As a result, bioactivity may have important implications for global chemical fluxes and the evolution of seawater, oceanic crust, and mantle throughout Earth history. Microbial colonization of basaltic glass leads to the formation of characteristic textural, chemical, and isotopic biosignatures that have been d iscovered in in-situ and ancient oceanic crust of all ages (up to 3.5 Ga) worldwide. Our studies thus demonstrate that biomarkers in volcanic rocks can be preserved back to the Archean and have suggested a new geological setting for the development of ear ly life on Earth. The purpose of this proposal is to continue and expand upon our previous studies in volcanic rocks of the very ancient oceanic crust (greenstone belts) by addressing three key questions: 1) how far back in time can we trace bioalteration in pillow lavas; 2) is bioalteraton preserved in pillow of greenstone belts worldwide and what were the key environmental controls; and 3) can we identify and date unique biogeochemical tracers to help us compare ancient microbial activity with modern bi oalteration? These questions will be answered through detailed fieldwork and comprehensive collection of formerly glassy volcanic rocks from well-preserved greenstone belts worldwide ranging in age from 2.0-3.5 Ga. We will conduct now well-established mul tidisiplinary imaging and geochemical techniques and develop state-of-the-art in-situ microbeam geochemical analyses at the micro- and nano-scale. We will ultimately put the results of our project into a global context to help understand how ancient micro bial life became established on the early Earth, what environmental factors controlled its development, and how it interacted with the volcanic component of the solid Earth through time.