A New Method for Relating Zircon Crystallisation to Petrogenetic Events

Abstract The trace element contents of zircon can provide unique insights into tectonothermal events, however, interpreting these data and identifying correlations with specific magmatic/metamorphic events be challenging. This limits our ability to construct temporally constrained petrogenetic histories complex metamorphic terranes. Unlocking the information that rare earth (REE) patterns contain is difficult because need quantify differences. We have parametrised shape REE in terms three independent parameters: average abundance, slope, curvature. Quantifying using parameters similar use ratios but an improvement as (1) it uses from all 14 rather than just two; (2) two (e.g. slope curvature) a more robust discriminant single ratio; (3) subtle variations are easily distinguished enabling trends large datasets identified. Quantitative models were constructed showing how shapes change due co-crystallisation other minerals (monazite, apatite, garnet). Diagnostic changes enable crystals or crystal zones accurately related growth hence events. results used interpret zircons high-grade terranes, which experienced multiple deformation (Val Malenco, Italy; Betic Cordillera, Spain; Seram, Indonesia; Lewisian Gneiss Complex, Scotland; Napier East Antarctica) clearly identified crystallised presence garnet. comparison enabled prior to, synchronously with, after garnet Similar monazite. allows relative timing constrained, given importance for geochronology geobarometry has potential evolution event.