Early Precambrian layered intrusions

Abstract

We highlight those features which may be common to all early Precambrian layered intrusions, in order to gain some insight into the processes which gave rise to their emplacement and to the spectacular layering contained in them. We focus on the Bushveld and Stillwater complexes and major dyke-like intrusions (the Great Dyke of Zimbabwe, those in northern Finland and the Jimberlana intrusion of Western Australia) because these are the largest, best preserved and most intensively studied. Anorthosite complexes, layered ultramafic sills and some intensely deformed early Archaean complexes are compared with these major intrusions. For each intrusion the location, age, intrusion form, lithology and parental magma composition (where known) are described. -from Authors