Linking age to stage? Processes and pitfalls in dating metamorphic cycles.

Warren, Clare; Mcdonald, Christopher; Mottram, Catherine and Regis, Daniele (2014). Linking age to stage? Processes and pitfalls in dating metamorphic cycles. In: 31st Nordic Geological Winter Conference, 8-10 Jan 2014, Lund, Sweden.

URL: http://geologiskaforeningen.se/31winter.html

Abstract

Mountains form where tectonic plates collide, and the rates and timescales over which crust is buried, transformed, deformed and recycled in these collision zones informs our understanding of crustal (re)cycling processes. Recent advances in analytical capability mean that geochronologists are now able to measure the dates recorded by geochronometers with increasingly precision. Recent data collected via in-situ techniques commonly yield a protracted range of dates rather than a single age. The data therefore suggest that geochronometers may record protracted crystallization over a range of PT conditions rather than a specific ‘event’. The difficulty lies in linking geochronometer crystallization or cooling dates to the precise PT evolution of the host rock. Here we present new insights into the interpretation of metamorphic crystallization (U-Pb) and cooling (Ar/Ar) ages. Trace element data of major and accessory phases are important for fingerprinting accessory phase crystallization reactions. Modelling different cooling path shapes helps to improve interpretation of the Ar/Ar ages. Together the new data help provide precise and reliable rates and timescales of metamorphic cycles.

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