THE SCOTIA SEA GATEWAY: NO OUTLET FOR PACIFIC MANTLE

The Scotia Sea in the South Atlantic holds a prominent position in geodynamics – it has been proposed as a potential mantle outlet from under the shrinking Pacific. This hypothesis has been previously tested by geochemically sampling of dredged rocks upon their mantle domain origin and shear-wave splitting studies. Here, we follow a different and new approach by calculating the present-day dynamic topography of the region in search for a systematic gradual decrease in dynamic topography from west to east. In our view, suchlike systematic variation would clearly indicate present-day mantle flow. To do so, we reconstructed the kinematic history of the Scotia Sea, first, which is characterized by complex back-arc spreading processes active on various time scales. Based on this reconstruction model, we derived an age-grid and calculated the residual (dynamic) topography of Scotia. Our results do not indicate a systematic variation, inferring no present-day mantle flow through Scotia. This result is consistent with the above mentioned previous studies.