In situ fractionation and inward migration of the solidification front in the Skaergaard intrusion, East Greenland

摘要

For more than 80 years the Skaergaard intrusion, 68°Nin southern East Greenland, has been a foremost naturallaboratory for the study of the crystallisation and fractionation of basaltic magma. This process has been of primeimportance in the evolution of the Earth and other stonyplanets. Models that have been developed and refined during numerous studies of this particular intrusion have beenpart of the foundation for petrogenetic modelling for decades. In later years, vast amounts of new data have beenadded, due to systematic sampling in the field and fromanalysis of exploration drill cores. Methods for the studyon grain-size scale have advanced, and the quest for a wellsupported genetic model for the PGE-Au mineralisationof the intrusion has intensified. The new data and insightquestion the applicability of conventional petrogeneticmodelling, and as a consequence, increasing importance isplaced on in situ crystallisation and fractionation in mushzones at the roof, walls and floor of the intrusion.