Caledonian igneous rocks of Britain and Ireland

Abstract

AbstractThe British sector of the Caledonide-Appalachian fold belt, which bridges the Iapetus plate closure zone, has a range of plutonic, volcanic and volcaniclastic lithologies with characteristic space-time variations. The map of Caledonian igneous rocks in the British Isles (Plate 1) is compiled from many sources, some of which predate the use of methods of classification which are based largely on chemical data. In such cases, whilst extensive re-mapping continues, the compilers have had to resort to the collection and analysis of representative samples from the areas in question, the collection sites being based on existing maps. Thus, whilst the references to the mapped areas indicate specific publications, the chemical data on which the coding is based are commonly derived from compilations such as Stillman & Williams (1979) and Stillman & Francis (1979) for volcanic rocks and Sutherland & Pankhurst (1982), Le Bas (1982), Hall (1972) and Brown et al. (1981) for plutonic rocks.The coding system, which is explained fully in the Plate 1 legend, is that accepted by the Plutonics-Volcanics International Working Group of IGCP Project 27 and is intended to provide a shorthand description by which the user of the map may ascertain as much information as possible about the igneous rocks of each locality, many of which cover too small an area on the 1:2 million scale of the map to be reconizable on any conventional system of colour and symbol designation. Given the small scale of Plate 1 the chemical symbols portrayed are a compromise in