Friday, September 05, 2014

Effect of impact energy on SIMS U–Pb zircon geochronology

I have a paper out in pre-publication online availability. The basic gist of it is that we are investigating exactly why SHRIMP is so good at geochronology.  It is a short format conference proceedings paper, so there isn't that much to it.  Basically, we investigated the oxide formation used to calibrate relative U/Pb ionization yields by bombarding natural zircon with a primary ion beam made of 18O2ions.  This way, all the molecular oxide ions were isotopically labeled- 16O if the oxygen originated in the sample, 18O if it was from the primary beam.  We then varied the ion impact energy to see what effect this had on the overall collection efficiency.

One of the other different things about this paper is that I co-wrote it with my dad.  He doesn't know any geology, but since I was about five he has been using SIMS (not SHRIMP, other brands) analysing semiconductors.  He still lives in America, so I don't get to see him much any more, and he's not getting any younger.  So it was nice to have a structured activity to work on together.  The middle author, Jim Ferris, did the atomic force microscopy. Unfortunately due to the short format, we didn't have space for any of his pictures, but he measured the sputter crater volumes, which we needed to calculated useful yields.

Magee C. Jr., Ferris J. and Magee C. Sr. (2014), Effect of impact energy on SIMS U–Pb zircon geochronology, Surface and Interface Analysis, DOI: 10.1002/sia.5629

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