Dyke swarms are remnants of large igneous provinces, and are pointers of continental break-up events, as well as indicators for ancient continental reconstructions. These global geodynamic aspects are of crucial significance in tectonics, and with recent developments in high-precision age, dating it has become possible to enter these short-lived magmatic events into a global data base. Every five years, scientists have met to consider new results and potential directions relating to the study of igneous dykes. At the Fifth International Dyke Conference, held in Rovaniemi, Finland in August 2005, igneous dykes, with particular attention to mafic dykes and dyke swarms, came under scrutiny. The properties of dykes, from Archean to Miocene, were explored in terms of mineralogy, geochemistry, isotopes, geochronology and paleomagnetics.  This is a selection of twelve papers presented in Rovaniemi, together with updates of six papers from the South African meeting in 2001. For those who wish to have a summary of the current international status of igneous dykes, and their significance in interpreting geological and tectonic processes, this book is invaluable.