Saturday, March 17, 2012

My First Garnet Age

It's been way too long since I've written a post.  I've saved up a nice long list of topics that I can write about and adventures from the last month and half but just haven't gotten around to writing the posts yet.  I'm hoping that this post will be the first of several over the next couple of days to get more or less caught up and whittle down my idea list.  Instead of going chronologically, I'm going to start with a science update...since that's the cause of my delay in writing anyway. :-)

There has been a lot of exciting science in the past month and a half since I wrote about my first trip to WHOI to use the SEM.  I'm balancing two classes (Geodynamics as well as "Thermodynamics and Kinetics of Tectonometamorphic Processes," which is taught by my adviser) and finally getting pretty close to being independent on most of my research procedures after learning several new steps these past couple of weeks.

The biggest push for research has come over the past two weeks.  This past summer when I did fieldwork in Scotland (see earlier posts if you missed the beautiful Scotland scenery!) I collected several samples and shipped them back here.  In November I sent two of those samples off for crushing and mineral separation and they came back roughly three weeks ago.  As I was in a meeting with my adviser just over two weeks ago, we were talking about research priorities and he mentioned that he would love to have an age for garnet from one of the samples ahead of his upcoming talk at the University of St. Andrews, Scotland on his European speaking tour but he wasn't sure if it was possible.  Normally taking garnet from raw mineral to an age takes us three to four weeks, with two weeks being the absolute fastest speed possible if everything goes according to plan.  I agreed to try and plotted out every step on a calendar, knowing that I would make it with just about 12 hours to spare if I succeeded.  It was also complicated by the fact that I have never completed some of the final steps, because I just hadn't gotten there yet with test samples.

So, basically the last two weeks were two solid weeks of lab work.  It included a second trip to Woods Hole to do SEM work on the Scotland samples (and incidentally learning how to change an SEM filament...), about a week and a half of 12+ hour workdays in the clean lab in my superhero get-up, two days of learning to load samples and how to load the mass spec., and two days of learning how to run our instrument.  (Eventually I'm hoping to write a series of posts to show you some of the basic methods and our instrument, the TIMS.)  Amazingly, my sample survived and I can finally say I have my first garnet age!!  Not only was this the first time I generated an age by doing the procedures from beginning to end, I made it within two weeks (with 11.5 hours to spare), it was a ridiculously small sample (I started with only 4mg of garnet...4 sand grains basically), many of the procedures I was doing independently for the first time or I was learning with supervision for the first time, and the result was right in the expected ballpark!  If you can't tell, I have been quite pleased for the last day or two.

Now that I have my first age under my belt, I can start testing and implementing some of my ideas for changes to the procedure to improve how our lab works with very tiny samples and for further method development on the new garnet dating system I am developing.  While I'm excited about my first data point, there are many improvements to be made and many more points to be gathered.  Onward in the pursuit of science.


  1. You're going to tease us with a headline like that and then not even tell us what the age is? Really? That's no way to reward your loyal readers.

  2. Haha! It was 455 +/- 3 Ma on a two-point isochron, which is ballpark correct for Scotland Grampian. I'm fairly certain the garnet still needs more aggressive cleaning to eliminate inclusion influence and the method still isn't fully developed yet, so it's not publishable yet. :-)

  3. Hooray! And thanks. FWIW, my first date was ~100Ma (U/Pb zircon, conventional TIMS, UW-Madison, circa 1992-93), though I can't recall all the details.