Deep thermal field and rheology in different plate tectonic settings

Continental rifting and breakup as well as plate convergence and collision create specific geophysical configurations with characteristic thermal fields which in turn lead to characteristic rheological settings. Three-dimensional data-integrated models demonstrate how thermal fields and rheological configurations of the Earth’s crust and uppermost mantle are characteristic depending on the tectonic setting. While the spatial variation of thermal conductivities, variable contributions of radiogenic heat in response to crustal thickness and composition, and variable average geothermal gradients in response to lithosphere thickness are the main controlling factors, their superposed effects may result in a variety of thermal and rheological configurations. We present examples illustrating that rifts can be hot or cold depending on the rifting mode, the amount of stretching and the time since rift initiation. Passive continental margins can be hotter on their oceanic or  continental side depending on the age of the adjacent ocean.  The crust is hotter in orogens than in their forelands due to its thickened radiogenic felsic units compounded by  a superposed topographic effect. This hotter orogenic crust is rheologically weaker -a finding consistent with the absence of deep crustal seismicity in orogens as the Andes or the Alpine Himalayan Chain.