Thermal Ionization Mass Spectrometry

The Thermal Ionization Mass Spectrometry (TIMS) Laboratory is under the supervision of Dr J.D. Walker. The KU TIMS laboratory in Nichols Hall houses a 1987 version, full automated VG Sector variable 6-collector TIMS with a 10-sample turret, Daly multiplier, optical pyrometer, etc. The Sector was purchased with substantial funding from NSF and is still a state-of-the-art instrument: renovations during the summer of 1995 overhauled the collector cups and replaced the analog Daly system with an ion-counting system for an order of magnitude improvement in sensitivity. High-precision Sr and Nd analyses are routine; typical external and internal previsions for these elements are +/- 20 ppm. Pb analysis on rocks and minerals is also routine: we analyze as little as 25 pg total Pb with blank levels of 0.5 to 3 pg. Replicate analyses of standards give reproducibility of fractionation better than 0.0025%/amu. The main emphasis of TIMS at KU is for geochronology (especially U-Th bearing accessory minderal such as zircon, monazite, rutile, and titanite) and petrologic studies. The low Pb blanks and high sensitivity of our VG Sector allow for routine high-precision geochronological studies. In addition, ²³⁵U and ²³⁰Th spiked samples can be analyzed by isotope dilution by TIMS as well as ICP-MS.