Geochemical characteristics of Precambrian basaltic greenstones

Abstract

One of the most fundamental questions concerning early Precambrian basic magmas is whether or not they are geochemically the same as those produced in equivalent tectonic settings at the present day. However, the geochemical classification of ancient basic igneous suites on the basis of inferred tectonic setting, and the interpretation of ancient tectonic settings based on geochemical criteria are, to a large extent, iterative but circular processes. One of the most significant differences between basic metavolcanic suites of the Archaean and those of post-Archaean times is the abundance of Archaean komatiitic suites. There are few younger analogues with which to compare these suites directly and therefore little can be achieved in terms of identifying temporal changes in these types of magmas. On the other hand, basaltic volcanic rocks have been present throughout the geological record.