Large relatively high-elevation surfaces with low relief are common on the continents. Such uplifts have a significant impact on the geological record by influencing drainage networks and sediment supply, on climate by modifying atmospheric circulation, and on biogeography and the biota. Work in geodynamics has shown that such uplifts amount to a telling signature of mantle dynamics. Thus, they provide a means to discriminate among hypotheses about how the continental lithosphere and the deeper mantle interact through processes that result in uplift and mass transfer in continental interiors. The Hangay Dome in central Mongolia provides an excellent and accessible laboratory to investigate these processes and determine the degree to which mantle upwelling, mafic underplating, lithospheric foundering or plume activity have been important agents in its uplift. This five-year project proposes to use the Hangay Dome as such a laboratory to coordinate studies of both the structure and state of the lithosphere and the sublithospheric mantle as well as the history of surface uplift and landscape evolution. The project will involve observations and measurements made using broadband seismology, basalt and xenolith petrology and geochemistry, 40Ar/39Ar geochronology, stable-isotope and vesicular-basalt paleoaltimetry, geomorphology and 10Be geochronology, molecular genetics of divergent fish populations, and U-Th/He and 4He/3He thermochronology. The Hangay Dome?s widespread exposures of basaltic lavas, which were erupted over the past 30 Ma across a broad range of elevations, will be key to the integration of all these data. Dating of the basalts will enable linkage of petrologic data bearing on basalt genesis and the nature of the Hangay-Dome mantle with studies that use the lavas as time markers for documenting landscape evolution and the history of surface uplift.
