Back-arc basins

Abstract

As illustrated in this book, oceanic basalts are compositionally diverse. This diversity arises not only from low pressure fractionation in sub-volcanic magma chambers, but also during the solid—liquid fractionation that accompanies melting of the mantle. Isotopic and chemical studies also reveal gross heterogeneity in the composition of the sub-oceanic mantle (Chapter 15) reflecting major differentiation and recycling (e.g. subduction of oceanic crust) throughout the past 2.5 Ga, or even longer. To fully understand, and thus evaluate, all of these factors, it is necessary to study basalt genesis in many tectonic settings. The study of magmatism at destructive plate boundaries provides important information about the scale of crustal recycling, which may in time influence our understanding of the evolution of the crust and mantle.