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SUMMARY:Atoms on the move: deformation-induced trace element redistributio
 n in zircon - Sandra Piazolo\, University of Leeds
DTSTART:20170228T120000Z
DTEND:20170228T130000Z
UID:TALK69709@talks.cam.ac.uk
CONTACT:Marian Holness
DESCRIPTION:Trace elements diffuse negligible distances through the pristi
 ne crystal lattice in minerals: this is a fundamental assumption when usin
 g them to decipher geological processes. For example\, the reliable use of
  the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element
  monitor requires minimal radiogenic isotope and trace element mobility.  
 Here\, using atom probe tomography\, we document the effects of crystal-pl
 astic deformation on atomic-scale elemental distributions in zircon reveal
 ing sub-micron scale mechanisms of trace element mobility. Dislocations th
 at move through the lattice accumulate U and other trace elements. Pipe di
 ffusion along dislocation arrays connected to a chemical or structural sin
 k results in continuous removal of selected elements (e.g. Pb)\, even afte
 r deformation has ceased. However\, in disconnected dislocations trace ele
 ments remain locked. Our findings have important implications for the use 
 of zircon as a geochronometer\, and highlight the importance of crystal-pl
 astic deformation on trace element redistribution in minerals.
LOCATION:Tilley Lecture Theatre\, Department of Earth Sciences
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