New York Times Scientist At Work Blog features a geologist this time.
John Goodge, a professor of geological sciences at the University of Minnesota-Duluth writes about his research and field work in Antarctica along with a good explanation of the various zircon dating methods and the instruments involved in this sophisticated geochemical analysis.
..the A.N.U. has been building a special class of ion probes since the 1980s called Shrimp, which stands for sensitive high-resolution ion microprobe. The name Shrimp belies their actual size. These instruments cover a floor space of about 13 feet by 20 feet. It is by virtue of their size, the so-called turning radius of the mass spectrometer’s magnet, that they are so powerful in dating zircons of only a few tens of microns in size by the U-Pb method. In other words, analyzing something very small sometimes takes something very big.
Not quite the Large Hadron Collider... but impressive nonetheless.
The aim is to reconstruct the evolution of Antarctica crust and for that, dating the rocks accurately is essential. Not all rock samples are exposed as outcrop.. the scientists are relying on rock fragments eroded by glaciers and dumped in moraine deposits to sample pieces of crust hidden under ice.