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| Titel |
High-precision measurements of uranium and thorium isotopic ratios by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) |
| VerfasserIn |
Lisheng Wang, Zhibang Ma, Wuhui Duan |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111077
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| Publikation (Nr.) |
 EGU/EGU2015-11142.pdf |
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| Zusammenfassung |
| Isotopic compositions of U-Th and 230Th dating have been widely used in earth sciences,
such as chronology, geochemistry, oceanography and hydrology. In this study, five
ages of different carbonate samples were measured using 230Th dating technique
with U-Th high-precision isotopic measurements by multi-collector inductively
coupled plasma mass spectrometry, in Uranium-series Chronology Laboratory,
Institute of Geology and Geophysics, Chinese Academy of Sciences.In this study, the
precision and accuracy of uranium isotopic composition were estimated by measuring
the uranium ratios of NBS-CRM 112A, NBS-CRM U500 and HU-1. The mean
measured ratios, 234U/238U = 52.86 (±0.04) x 10-6 and δ234U = -38.36 (±0.77) x
10-3 for NBS-CRM 112A, 234U/238U = 10.4184 (±0.0001) x 10-3, 236U/238U
= 15.43 (±0.01) x 10-4 and 238U/235U = 1.00021 (±0.00002) for NBS-CRM
U500, 234U/238U = 54.911 (±0.007) and δ234U = -1.04 (±0.13) x 10-3 for HU-1
(95% confidenceÂlevels). The U isotope data for standard reference materials are in
excellent agreement with previous studies, further highlighting the reliability and
analytical capabilities of our technique. We measured the thorium isotopic ratios of
three different thorium standards by MC-ICPMS. The three standards (Th-1, Th-2
and Th-3) were mixed by HU-1 and NBS 232Th standard, with the 230Th/232Th
ratios from 10-4 to 10-6. The mean measured atomic ratios, 230Th/232Th = 2.1227
(±0.0024) x 10-6, 2.7246 (±0.0026) x 10-5, and 2.8358 (±0.0007) x 10-4 for Th-1,
Th-2 and Th-3 (95% confidenceÂlevels), respectively. Using this technique, the
following standard samples were dated by MC-ICPMS. Sample RKM-4, collected from
Babardos Kendal Hill terrace, was used during the first stage of the Uranium-Series
Intercomparison Project (USIP-I). Samples 76001, RKM-5 and RKM-6 were studied during
the second stage of the USIP program (USIP-II). Sample 76001 is a laminated
flowstone, collected from Sumidero Terejapa, Chiapas, Mexico, and samples RKM-5
and RKM-6 are from the Babardos III terrace and the lower terrace (6 to 10m) of
Curacao, respectively. China RCM GBW04412 was also analyzed. The ages of the five
standard samples mentioned above are 197970±1590 yr BP, 47520±220 yr BP,
129300±650 yr BP, 130830±550 yr BP, and 86940±300 yr BP for samples RKM-4,
76001, RKM-5, RKM-6 and GBW04412, respectively. The results are consistent
with the data of the same samples analyzed in Institute of Global Environmental
Change, Xi’an Jiaotong University and Department of Earth Sciences, University of
Minnesota, USA within errors, which suggests that the technique in our lab is reliable. |
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