Thermal Ionization Mass
Spectrometry (TIMS)
Lab phone:
520-621-4259
Ducea is a co-P.I. of our department's
TIMS facility. This facility consists of a state of the art clean laboratory.
The analysis of Sr, Nd, Pb, and Hf isotopes on whole-rocks and mineral
separates is routine in the TIMS laboratory of the
We separate U and Pb in 2 ml Bio-Rad
columns with cation resin using HBr as eluent for Pb. Rb and Pb is loaded onto
single Re filaments using silica gel and H3PO4. We load Sr onto single Ta
filaments, sometimes using tantalum oxide slurry. Sm and Nd is typically loaded
onto triple Re filaments. Mass Spectrometric analyses are carried out on two VG
Sector multicollector instruments (Sr, U and Pb on a VG54 and Rb, Sm, and Nd on
a VG354) fitted with adjustable 1011 Faraday collectors and Daly
photomultipliers (Patchett and Ruiz, 1987; Ducea et al., 2002). Concentrations
of Rb, Sr, Nd, U, and Pb are determined by isotope dilution, with isotopic
compositions of Sr, Nd, and Pb determined on the same spiked runs. An off-line
manipulation program is used for isotope dilution calculations.
Much of out U-Th-Pb geochronologic
analyses are more recently conducted in with a newly acquired laser ablation
Micromass Isoprobe, for which analytical methods are currently being developed.
The ICPMS is equipped with 9 faraday collectors, an axial Daly detector, and 4
ion-counting channels. The laser is a Compex 102 ArF Excimer laser,
manufactured by Lamda Physik, with and emission wavelength of 193 nm. The
instrument has a flight tube of sufficient width that U, Th, and Pb isotopes can
be measured simultaneously in static mode. The typical collector configuration
has 202Hg and 204Pb in secondary electron multipliers while 206Pb, 207Pb,
208Pb, 232Th, and 238U are measured with Faraday detectors.
