SCIENTIFIC DRILLING IN THE BARBERTON GREENSTONE BELT

The Barberton Greenstone Belt in South Africa is a remarkable natural laboratory where conditions at the surface of the Archean Earth can be investigated. Shallow (100-1000m) cores will be drilled in selected volcano-sedimentary successions in order to reconstruct the geodynamics of Archean sedimentation and volcanism, how these processes interacted at the interface between lithosphere-hydrosphere-atmosphere-biosphere, and the environments at the Earth's surface where life first emerged and subsequently evolved. Despite generally good outcrop, nowhere in the Barberton belt are complete sections preserved, and crucial features such as the contacts of lava flows and critical sedimentary rock sequences are not exposed. Drilling is needed to obtain such sections and relatively unaltered samples. Two main targets have been identified. (1) Sedimentary sequences will provide information about erosion and sedimentation on the early Earth, the composition and temperature of Archean seawater, and one site where life may have emerged and evolved. Tidal sequences will inform us about the dynamics of the Earth-Moon system, and spherule layers and impact debris provide information about the nature and magnitude of meteorite impacts. (2) Successions of ultramafic to felsic volcanic rocks will provide new insights into volcanic processes, mantle dynamics, and interaction between oceanic volcanic crust and the hydrosphere and biosphere. The sources of hydrothermal fluids on the ocean floor, driven by circulation of seawater through the volcanic pile, constitute a second habitat of early life. The project is supported by scientists from 17 countries in five continents, by the mineral exploration industry and by the International Continental Drilling Program.