Hi Andreas and others
As I mentioned before - I agree with the interpretation of Daniela, Dan, Simon and yourself (and perhaps Thorsten and Lutz) that the most likely cause of the disrupted CL pattern is radiation damage, plus/minus related geochemical alteration. The texture is unlike the effects of crystal-plasticity in this case. However, disruption that is limited to cores but not rims is not necessarily a diagnostic feature. It is possible that deformed cores (igneous or metamorphic) could be overgrown by undeformed metamorphic rims. Also, Reddy et al. (2009, CMP, 157 (2), 231-244) documented the occurrence of syn-magmatic crystal-plastic deformation of zircon in an 'undeformed' porphyritic andesite from Java. So, conceivably, deformed igneous cores could also be overgrown by undeformed igneous rims. Apologies for the shameless plugging!
Regards
Nick
_______________________________________
Dr Nick Timms
The Institute for Geoscience Research (TIGeR)
Department of Applied Geology
Curtin University of Technology
GPO Box U1987, Perth, WA 6845, Australia
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_______________________________________
-----Original Message-----
From: Metamorphic Studies Group [mailto:[log in to unmask]] On Behalf Of Andreas Möller
Sent: Tuesday, 18 May 2010 10:52 AM
To: [log in to unmask]
Subject: Re: Zircon CL-pattern -thanks
Hi y'all,
Nick would you agree that deformation is unlikely
the cause for the patterns that Jochen sees in
his zircons. The mottled "brain texture" is
apparently affecting only the interior of the
grains and the rims show undisrupted zoning.
Deformation related features would look
distinctly different, would they not?
But I agree that in other rocks deformation is a
potentially very important modifier of traces and
U-Th-Pb, much admired those papers! 8-)
cheers,
Andreas
>Hi Jochen and others
>
>I agree with the others about the interpretation
>of the zircon CL pattern that you posted to the
>list. However, it might be worth considering
>crystal-plastic deformation and associated
>localized trace element diffusion as another
>potential cause of disruption to primary CL
>patterns in zircon.
>Timms, N.E., and Reddy, S.M., 2009, Response of
>cathodoluminescence to crystal-plastic
>deformation in zircon, Chemical Geology, 261,
>(1-2), 11-23.
>Regards,
>Nick
>
>_______________________________________
>
>Dr Nick Timms
>The Institute for Geoscience Research (TIGeR)
>Department of Applied Geology
>Curtin University of Technology
>GPO Box U1987, Perth, WA 6845, Australia
>
>[Office] Room 312.321.5
>[Phone] +61 (0)8 9266 4372
>[Fax] +61 (0)8 9266 3153
>[Mobile] +61 (0)427 324 199
>[Web - Uni] http://geology.curtin.edu.au/people/nick_timms/timms_profile.cfm
>[Web - personal] http://members.iinet.net.au/~nicktimms/
>Secretary for Specialist Group in Geochemistry,
>Mineralogy and Petrology:
>http://sggmp.gsa.org.au/index.html
>Vice Chair for Geological Society of Australia,
>WA Division: http://wa.gsa.org.au/
>_______________________________________
>-----Original Message-----
>From: Metamorphic Studies Group
>[mailto:[log in to unmask]] On
>Behalf Of Jochen Mezger
>Sent: Monday, 17 May 2010 11:13 PM
>To: [log in to unmask]
>Subject: Zircon CL-pattern -thanks
>
>Thanks to all,
>
>for providing valuable information and hints. I
>have ordered a copy of the RIM zircon volume, and
>got a hold of the Zircon issue of "Elements" (the
>website of Elements apparently does not work at
>the moment). I will also look at some of the recommended authors.
>
>I may also have the chance to get BSE images from
>these zircons. Considering the causes for such
>patchy or mottled textures, Simon called it
>"brain texture" [I like that one; or maybe "BSE
>brain texture" :) ], I should consider myself
>lucky for the fact that one third of the analyses
>of that sample provide meaningful concordant ages.
>
>Best wishes and merci bien,
>
>Jochen
>
>
>***************************************************************************
>Dr. Jochen Mezger
>Lehrbeauftragter - Lecturer
>Allgemeine Geologie
>
>Martin-Luther-Universität Halle-Wittenberg Tel.: 49-0-345-5526120
>Institut für
>Geowissenschaften Fax: 49-0-345-5527220
>Von-Seckendorff-Platz 3
>06120 Halle Email: [log in to unmask]
>GERMANY
>
>http://www.geologie.uni-halle.de/igw/allgeo/staff/mez.html
>http://allgeo.geologie.uni-halle.de/mitarbeiter/jmezger/
>============================================================
>
>"Vous etes des assassins ! -
> You are murderers !" Octave Lapize,
>winner of the 1910 Tour de France
> at the summit of the Tourmalet, Pyrenees
> to Henri Desgranges, organizer of the Tour
>
>
>****************************************************************************
>
--
--------------------------------
Dr. Andreas Moeller
Assistant Professor - Geochronology
University of Kansas
Department of Geology - IGL
2335 Irving Hill Road
Nichols Hall, Room 243/357
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- USA -
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