Coupled trace element analysis and cathodoluminescence imaging applied to anatectic aluminous granulites: the metamorphic record of quartz and kyanite

Abstract

Anatectic aluminous granulites from the Grenville Province, Canada, are investigated using trace element analysis and cathodoluminescence (CL) mapping of quartz and kyanite. Two types of quartz: crystals resorbed during partial melting and retrograde pseudomorphs after partial melt, are identified by CL mapping. Titanium-inquartz thermobarometry for each type is evaluated in the context of phase equilibria modelling. Despite the presence of rutile, most quartz did not reach equilibrium Ti concentrations, especially during melt crystallisation. Kyanite porphyroblasts in highpressure samples are found to be composite crystals comprising up to three generations of kyanite, two prograde and one retrograde. These are linked to a metamorphic reaction history consistent with phase equilibria modelling, and are used to provide additional constraints on the P–T evolution of these rocks. Trace element analysis and CL mapping are valuable complements to traditional methods of investigating high-grade metamorphic rocks.