1Introduction Regions of continental break-up are often associated with extensive magmatic activity(e.g.,White and McKenzie,1989).This commonly consists of huge volumes of basalts(flood basalts or rift-related basalts)and variable amounts of silicic volcanics,forming the so-called Large Igneous Provinces(LIPs).In most cases a wide silica gap occurs between silicic and basic compositions,defined as the Daly Gap,with small amounts or an absence of intermediate rocks(e.g.,Bellieni et al.,198…