GMPV3Late-orogenic potassic mafic magmatism: Archaean to present
|Co-Convener: Vojtěch Janoušek|
Potassic mafic rocks are a minor, but ubiquitous, component of late-orogenic granitic plutons that provide information about mantle-crust interactions and the timing of new crustal growth versus crustal recycling. Such rocks are described from the Mesoarchaean to the Recent and include ‘sanukitoids’, ‘appinites’, "durbachites’ and ‘vaugnerites’. Associated granitoids form the ‘sanukitoid suite’ and the ‘high-K calc-alkaline’, ‘sub-alkaline’, ‘magnesio-potassic’ and ‘ferroan A-type’ associations.
There seems to be a general agreement that the origin of potassic mafic rocks is a two-stage process involving: formation of an enriched mafic mantle-derived component and its interaction with crustal melts that form associated granitoids. Both aspects need to be clarified and systematized, first, the mafic component - its source, origin, depth of melting, cause of enrichment, and second, the associated anatectic magmas - how they are related to the mafic component. These types of igneous rocks are generally regarded as minor, anecdotal and only locally relevant. We aim to bring together scientists involved in their study, and draw attention to the fact that Mg-K magmatism is actually a ubiquitous component of the late orogenic period that potentially provides key information about the latest stages of orogenic evolution.
This session invites contributions on the petrology, geochemistry, geochronology and structural controls of the Mg-K mafic rocks and related granitoids: their origin and evolution; tectonic context and geodynamic implications of their formation; and their age. We particularly encourage contributions that attempt to compare and contrast the various rock types, with the ultimate goal of proposing a unified terminology.