ORIGINAL PAPER The recognition of multiple magmatic events and pre-existing deformation zones in metamorphic rocks as illustrated by CL signatures and numerical modelling: examples from the Ballachulish contact aureole, Scotland Helena Bergman • Sandra Piazolo Received: 18 January 2011 / Accepted: 6 October 2011 Ó Springer-Verlag 2011 Abstract The combination of cathodoluminescence (CL) analysis, temperature and temperature–time calculations, and microstructural numerical modelling offers the possi- bility to derive the time-resolved evolution of a metamor- phic rock. This combination of techniques is applied to a natural laboratory, namely the Ballachulish contact aure- ole, Scotland. Analysis of the Appin Quartzite reveals that the aureole was produced by two distinct magmatic events and infiltrated by associated fluids. Developing micro- structures allow us to divide the aureole into three distinct regions. Region A (0–400 m, 663°C \ T max \ 714°C) exhibits a three-stage grain boundary migration (GBM) evolution associated with heating, fluid I and fluid II. GBM in region B (400–700 m, 630°C \ T max \ 663°C) is associated with fluid II only. Region C ( [ 700 m of contact, T max \ 630°C) is characterised by healed intragranular cracks. The combination of CL signature analysis and numerical modelling enables us to recognise whether grain size increase occurred mainly by surface energy-driven grain growth (GG) or strain-induced grain boundary migration (SIGBM). GG and SIGBM result in either straight bands strongly associated with present-day boundaries or highly curved irregular bands that often fill entire grains, respectively. At a temperature of *620°C, evidence for GBM is observed in the initially dry, largely undeformed quartzite samples. At this temperature, evi- dence for GG is sparse, whereas at *663°C, CL signatures typical for GG are commonplace. The grain boundary network approached energy equilibrium in samples that were at least 5 ka above 620°C. Keywords Annealing  Grain boundary migration  Contact metamorphism  Magmatic events  TitaniQ thermometry  Numerical modelling Introduction The aim of this paper is to investigate how cathodolumi- nescence (CL) patterns can be used as indicators for the activity of microstructural processes and for multiple magmatic events. In order to achieve this, we have chosen to conduct a detailed study on the Appin Quartzite from the Ballachulish contact aureole, Scotland. Our study com- bines detailed analyses of patterns revealed by CL, numerical calculations of the temperature–time (T–t) paths supported by T estimated through trace element analysis and numerical modelling of the microstructural evolution of different pre-annealing microstructures. This unique combination of techniques allows us to establish criteria for the recognition of multiple magmatic events and pre- annealing microstructures in metamorphic rocks that have undergone significant annealing due to either contact or regional metamorphism. When a magmatic intrusion occurs, the host rocks are affected by resultant fluid and temperature changes. Con- tact aureoles represent excellent field areas to study the Electronic supplementary material The online version of this article (doi:10.1007/s00531-011-0731-6) contains supplementary material, which is available to authorized users. H. Bergman  S. Piazolo Department of Geological Sciences, Stockholm University, 106 91 Stockholm, Sweden S. Piazolo (&) Department of Earth and Planetary Sciences, GEMOC ARC National Key Centre, Macquarie University, Sydney, NSW, Australia e-mail: sandra.piazolo@mq.edu.au 123 Int J Earth Sci (Geol Rundsch) DOI 10.1007/s00531-011-0731-6