Geological Society of London
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Understanding K-feldspar 40Ar/39Ar data: reconciling models, methods and microtextures

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journal contribution
posted on 2016-06-21, 12:07 authored by Sandra McLaren, W.James Dunlap, Roger Powell

Several descriptions of argon diffusion in K-feldspar have been developed, including the quantitative multiple-diffusion-domain (MDD) and multipath models and the qualitative ‘recrystallization’ model. These models remain contentious and the natural range in behaviour remains poorly understood. Feldspars from the Klokken syenite intrusion show a systematic relationship between 40Ar/39Ar age and microtexture suggesting that the loss of argon from different feldspars operates via different mechanisms such that the existing models represent only end-member scenarios. The MDD model can yield reliable thermal history information only for feldspars with pristine microtexture, with this model best viewed as a cipher for the real (but unknown) domain structure in such samples.