EXPLORING THE ROLE OF HOTSPOTS IN INITIATING CONTINENTAL BREAKUP FROM VOLCANIC VOLUMES AT RIFTED MARGINS

Warren Hamilton often criticized the presumed role of hotspots in tectonic processes. One of the most crucial such roles, proposed in the 1970's, is in initiating continental breakup. The concept has survived because of the argument that large volumes of igneous material at volcanic rifted margins require hotspot-induced melting. We explore this issue by estimating the volumes of volcanic material, including seaward dipping reflectors (SDRs) and high velocity lower crust (HVLC). We use cross sectional interpretations of seismic reflection profiles for conjugate margins in the Atlantic and elsewhere. A correlation of magma volumes with proximity to proposed hotspot locations during rifting would favor a hotspot role in rifting. Conversely, correlation with distance to the Euler pole and hence seafloor spreading rate variations during opening would argue against a hotspot role. A further issue involves asymmetries in the width of the zone of volcanics across conjugate margins - are these consistent along strike and how do they arise?