microprobes are fun toys
Feb. 6th, 2009 11:27 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
kareinaI spent this afternoon playing with the microprobe. Today's mission was U-Th-Pb dating of monazite, a (usually very tiny) metamorphic mineral. We've already dated zircon from this sample using the Laser ICPMS and found that there were some zircons which formed around 1200 million years ago, and some which formed around 500 million years ago, both generations of which appear to be metamorphic. There were way more monazite grains than zircon in this sample, so we decided to date the monazite as well, to see if they are from the same generations, because if they are it increases the odds that the dates for both are from the metamorphic growth within this rock, as opposed to having been pre-existing grains whcih got deposited into the mud which eventually metamorphosed into this sample.
The photo is one of the monazite crystals in an electron back-scatter image. This means that bright = heavy elements and dark = light elements. We've adjusted the settings such that only the monazite is bright enough to show at all (it contains heavy rare earth elements in addition to the uranium, thorium, and lead we use to work out its age), and subtle changes in its composition show us as shades of grey.
the spots marked are being analysed as I type, but I made a note of the x-y coordinates, so when I got home from setting them up I was able to use ArcMap to align the photos with the coordinates selected. In a couple weeks time, when I get the results of the dating (the microprobe operator leaves town tomorrow for a conference, and will get us the results when he returns) I will be able to change the spots to colour coordinate with their ages, and see if the different shades of grey correspond to different ages of mineral growth.
However, fun though all of this stuff is, it isn't helping me with the goal of finishing my writing last week. Indeed, when this particular probe session was scheduled, it was assumed that it would be too late to be included in my thesis, but would only appear in a paper we intend to publish once the thesis is done. Tomorrow![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
clovis_t will be heading to the beach with a friend, and plans to catch a "Shakesphere in the Park" play on the way home. I'll stay home and see if I can actually make some real progress on the thesis writing itself, instead of doing fun data acquisition like I did today.
The photo is one of the monazite crystals in an electron back-scatter image. This means that bright = heavy elements and dark = light elements. We've adjusted the settings such that only the monazite is bright enough to show at all (it contains heavy rare earth elements in addition to the uranium, thorium, and lead we use to work out its age), and subtle changes in its composition show us as shades of grey.
the spots marked are being analysed as I type, but I made a note of the x-y coordinates, so when I got home from setting them up I was able to use ArcMap to align the photos with the coordinates selected. In a couple weeks time, when I get the results of the dating (the microprobe operator leaves town tomorrow for a conference, and will get us the results when he returns) I will be able to change the spots to colour coordinate with their ages, and see if the different shades of grey correspond to different ages of mineral growth.
However, fun though all of this stuff is, it isn't helping me with the goal of finishing my writing last week. Indeed, when this particular probe session was scheduled, it was assumed that it would be too late to be included in my thesis, but would only appear in a paper we intend to publish once the thesis is done. Tomorrow
clovis_t will be heading to the beach with a friend, and plans to catch a "Shakesphere in the Park" play on the way home. I'll stay home and see if I can actually make some real progress on the thesis writing itself, instead of doing fun data acquisition like I did today.