Magma Mixing And Mingling Textures In Granitoids: Examples From The Galway Granite, Connemara, Ireland

Abstract

¶Many granitoid intrusions display textural evidence for the interaction of mafic and silicic magmas during their genesis. The ∼ 400 Ma Galway Granite exhibits excellent evidence for magma mixing and mingling both at outcrop/map scale (magma mingling and mixing zones), and at thin-section/crystal scale (mixing textures). These textures – quartz ocelli, rapakivi feldspars, acicular and mixed apatite morphologies, inclusion zones in feldspars, anorthite ‘spikes’ in plagioclase, sphene ocelli, K-feldspar megacrysts in mafic microgranular enclaves (MME), and mafic clots – constitute a textural assemblage whose origin can be explained in terms of magma mixing and mingling models. Furthermore, textures from this assemblage have been recorded throughout the Galway batholith indicating that magma mingling and mixing played a key role during its evolution.