U/Th dating by SHRIMP RG ion-microprobe mass spectrometry using single ion-exchange beads
Geochimica et Cosmochimica Acta
By: J. L. Bischoff, J. Wooden, F. Murphy, and Ross W. Williams
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Abstract
We present a new analytical method for U-series isotopes using the SHRIMP RG (Sensitive High mass Resolution Ion MicroProbe) mass spectrometer that utilizes the preconcentration of the U-series isotopes from a sample onto a single ion-exchange bead. Ion-microprobe mass spectrometry is capable of producing Th ionization efficiencies in excess of 2%. Analytical precision is typically better than alpha spectroscopy, but not as good as thermal ionization mass spectroscopy (TIMS) and inductively coupled plasma multicollector mass spectrometry (ICP-MS). Like TIMS and ICP-MS the method allows analysis of small samples sizes, but also adds the advantage of rapidity of analysis. A major advantage of ion-microprobe analysis is that U and Th isotopes are analyzed in the same bead, simplifying the process of chemical separation. Analytical time on the instrument is ???60 min per sample, and a single instrument-loading can accommodate 15-20 samples to be analyzed in a 24-h day. An additional advantage is that the method allows multiple reanalyses of the same bead and that samples can be archived for reanalysis at a later time. Because the ion beam excavates a pit only a few ??m deep, the mount can later be repolished and reanalyzed numerous times. The method described of preconcentrating a low concentration sample onto a small conductive substrate to allow ion-microprobe mass spectrometry is potentially applicable to many other systems. Copyright ?? 2005 Elsevier Ltd.
Suggested Citation
Bischoff, J.L., Wooden, J., Murphy, F., and Williams, R.W., 2005, U/Th dating by SHRIMP RG ion-microprobe mass spectrometry using single ion-exchange beads: Geochimica et Cosmochimica Acta, v. 69, no. 7, p. 1841-1846, https://doi.org/10.1016/j.gca.2004.09.017.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | U/Th dating by SHRIMP RG ion-microprobe mass spectrometry using single ion-exchange beads |
| Series title | Geochimica et Cosmochimica Acta |
| DOI | 10.1016/j.gca.2004.09.017 |
| Volume | 69 |
| Issue | 7 |
| Year Published | 2005 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Geochimica et Cosmochimica Acta |
| First page | 1841 |
| Last page | 1846 |