Volcanism and Tectonic Setting

Since publication of Cas and Wright (1987), the relationship between volcanism and tectonic setting has expanded into an enormous and multidisciplinary topic. In this chapter, we provide an updated review of the known tectonic settings in which volcanism occurs today and the relatively recent past, and the overall geological characteristics of these settings using the plate tectonic model as a global framework for Phanerozoic and Proterozoic times. However, there is little evidence that plate tectonics operated earlier during the Hadean and Archean, which represents almost 50% of geological time, and so we will also consider what the tectonic paradigm for volcanism was during the early history of the Earth. Initially, during the two billion years prior to when plate tectonics developed, the Earth was a magma ocean. This evolved into a single mafic–ultramafic crustal shell (stagnant lid) as the Earth cooled and was affected by mantle plume activity that influenced most volcanism. Buoyant diapiric granitoid plutonism resulting from anatexis of mafic lower crust allowed the Earth’s crust to evolve and “felsify”, leading to cratonic nuclei. Localised, limited subduction (mobile lid) commenced in the late Archean, but global plate tectonics probably didn’t develop as we know it until the Proterozoic (<2,500 Ma). In the post-Proterozoic plate tectonic framework, the first-order division of settings for volcanism is based on the overall prevailing regional tectonic regime: divergent, oblique/strike-slip, “passive or hot spot” (i.e. plume-related), or convergent settings. We describe the styles of volcanism typically found in the various plate margin and intraplate tectonic settings, incorporating information on crustal setting, magma generation, as well as the potential for the formation of Large Igneous Provinces (LIPs), providing examples from ancient terrains. In this discussion we will also introduce some of the more recent geodynamic concepts and their relationship to magmatic and volcanic activity. In particular, seismic tomography has evolved as one of the most powerful tools for studying the structure and dynamics of subduction zones and convergent plate margins. Finally, guidelines are given for the evaluation of the tectonic context in ancient volcanic and mineralised terrains. This chapter provides a dynamic framework to accompany our concluding chapter (Chap. 18 ) on volcanic-hosted resources.