Introduction to a virtual special issue on crustal melting

This virtual special issue represents a collection of papers concerning Crustal Melting selected by the Editor from those published on various aspects of this theme in the JMG since 1982. The papers are grouped into sequences that address topics that have been prominent in the JMG during the last 30 years concerning the origin, evolution and tectonic role of migmatites and migmatitic granulites in crustal evolution. These topics are: Openand closed-system processes in the formation of migmatites and migmatitic granulites; thermobarometry, P–T paths, phase equilibria modelling and retrograde processes in formerly melt-bearing rocks; geochronology in partially melted rocks; and, microstructures, deformation and tectonics of melt bearing rocks. About one-third of the papers published in the JMG since its inception concern the origin, evolution and tectonic significance of migmatites and migmatitic granulites in crustal evolution, including the first special issue published by the JMG concerning Studies in the genesis and deformation of migmatites edited by Tracy & Day (1988; Volume 6, Issue 4, Pages 385–543). Three subsequent Special Issues of the JMG include papers relevant to the theme of this virtual special issue; they are Metamorphic processes: a celebration of the career contribution of Ron Vernon , Processes in granulite metamorphism and Granulites, partial melting and the rheology of the lower crust , edited by Brown & Clarke (2002; Volume 20, Issue 1, Pages 1–213), Brown &White (2008; Volume 26, Issue 2, Pages 121–299) and Brown et al. (2011; Volume 29, Issue 1, Pages 1–166), respectively. The selection of papers in this virtual special issue is by no means comprehensive, but it is intended as a representative selection of what has been published in the JMG over 30 years to give the reader a broad overview of crustal melting. Furthermore, although many papers address more than one topic, each is included only once and has been placed within the most appropriate section.