Thursday, May 15, 2008

Titanium as a cathodoluminescence activator in alkali feldspars

Ian Parsons, David A. Steele, Martin R. Lee, and Charles W. Magee 2008. Titanium as a cathodoluminescence activator in alkali feldspars American Mineralogist, Volume 93, pages 875–879

Albite patches in coarsely mesoperthitic alkali feldspars from the Klokken syenite have oscillatory zoning seen at blue wavelengths using cathodoluminescence. Using a five-spectrometer, high-resolution elemental mapping technique in an electron probe, we show a close correspondence between CL emission intensity and Ti, present at levels up to ~200 ppm. Albite patches were analyzed for major and 16 trace elements by laser-ablation inductively coupled-plasma mass spectrometry. SEM elemental maps acquired simultaneously with the CL showed that a similar zoning pattern is exhibited by Ca, but there is no correlation between CL intensity and Ca concentration. None of the trace elements analyzed correlate with Ti. We conclude that tetrahedral Ti4+ is the most likely activator of blue luminescence in these albitic alkali feldspars possibly because of a defect associated with Al-O-Ti bridges.

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This is an example of a low marginal cost paper. The main purpose of bringing the samples to the ICP lab was a different study, but Ian figured he might as well check this out while everything was in place. The main study was big, complicated, and only just recently went off to reviewers. But this was simpler and more straightforward, so got written up and published first. So it is a great example of why research needs to be structured in a way such that investigators can veer off of their predetermined path if they see the opportunity to potentially figure something out for relatively little time, effort, and cost.

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