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Sandra McLaren, W. James Dunlap, and Roger Powell
Understanding K-feldspar 40 Ar/ 39 Ar data; reconciling models, methods and microtextures
Journal of the Geological Society of London (2007), 164(5):941-944
Abstract: Index Terms/Descriptors: GeoRef, Copyright 2007, American Geological Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
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 behavior remains poorly understood. Feldspars from the Klokken syenite intrusion show a systematic relationship between 40 Ar/ 39 Ar 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.
age; alkali feldspar; Ar/Ar; diffusion; exsolution; feldspar group; framework silicates; igneous rocks; intergrowths; intrusions; K-feldspar; Klokken Intrusion; layered intrusions; Mesoproterozoic; microperthite; models; plutonic rocks; Precambrian; Proterozoic; recrystallization; silicates; syenites; textures; thermal history; thermochronology; ultrastructure; upper Precambrian