Geochemical characteristics of igneous rocks as petrogenetic indicators

Abstract

In Chapter 1 we noted that magmas with distinctive major element characteristics are associated with specific tectonic settings. For example, calcalkaline series magmas are apparently associated uniquely with subduction, while low-K tholeiitic basalts are the typical products of magma generation at constructive plate margins. However, in general, the major element characteristics of primary mantle derived magmas are not particularly sensitive indicators of tectonic setting. Thus tholeiitic basalts are generated at mid-oceanic ridges but also in back-arc basins, oceanic islands, island arcs, active continental margins and continental flood basalt provinces. Fortunately, it is now well established that distinctive trace element and Sr-Nd-Pb isotopic signatures are associated with different magma generation environments, although their petrogenetic interpretation in some instances remains ambiguous (Chs. 5–12).