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Crystal-plastic deformation of zircon; a defect in the assumption of chemical robustness

Steven M. Reddy, Nicholas E. Timms, Patrick Trimby, Peter D. Kinny, Craig Buchan and Kevin Blake
Crystal-plastic deformation of zircon; a defect in the assumption of chemical robustness
Geology (Boulder) (April 2006) 34 (4): 257-260


Orientation contrast imaging and quantitative electron backscatter diffraction analysis of a zircon collected from an Indian Ocean gabbro reveal intragrain crystallographic misorientations (up to 14 degrees ) and low-angle orientation boundaries concentrated in the zircon tips. These features represent the formation and migration of dislocations and provide the first evidence of crystal-plastic deformation of zircon under crustal conditions. Panchromatic and wavelength cathodoluminescence (CL), combined with quantitative rare earth element (REE) ion microprobe analyses, demonstrate modification of zircon REE chemistry within the areas of crystal plasticity. These data indicate that the enhanced diffusion of REEs into the zircon is spatially linked to the presence of dislocations that behave as high-diffusivity pathways, increasing bulk diffusion rates and effective diffusion distances in the zircon by several orders of magnitude. In addition, discrete approximately 2 mu m zones of reduced panchromatic CL correspond exactly to the position of low-angle orientation boundaries and demonstrate a defect dependence on CL signal at high dislocation densities. The presence of deformation-related crystal-plastic microstructures in zircon, and their role in modifying elemental diffusion, questions the commonly made assumption of chemical robustness and has fundamental implications for the interpretation of zircon trace-element and isotopic data.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 34
Serial Issue: 4
Title: Crystal-plastic deformation of zircon; a defect in the assumption of chemical robustness
Affiliation: Curtin University of Technology, Tectonics Special Research Centre, Perth, West. Aust., Australia
Pages: 257-260
Published: 200604
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 36
Accession Number: 2006-035335
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2006062
Illustration Description: illus.
S32°43'25" - S32°43'24", E57°15'58" - E57°18'59"
Secondary Affiliation: HKL Technology A/S, DNK, DenmarkJames Cook University, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200619
Program Name: ODPOcean Drilling Program
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