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PXCG-1 and PXCG-2: two reference materials for gypsum U–Th dating.
- Source :
- JAAS (Journal of Analytical Atomic Spectrometry); Jun2024, Vol. 39 Issue 6, p1461-1469, 9p
- Publication Year :
- 2024
-
Abstract
- Gypsum is a widespread mineral in various sedimentary deposits. It precipitates from natural aqueous systems with trace amounts of U but almost no Th, rendering it a potentially valuable U–Th geochronometer. However, no gypsum RM for U–Th dating has been available. In this work, two natural gypsum reference materials (PXCG-1, PXCG-2) from the PiXiao cave, southwest China were prepared and characterized for U–Th dating. U–Th contents and isotope ratios were measured on a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) using the isotope dilution technique. Data from three different laboratories show good agreement in <superscript>238</superscript>U content, δ<superscript>234</superscript>U (<superscript>234</superscript>U/<superscript>238</superscript>U relative to secular equilibrium value), <superscript>230</superscript>Th/<superscript>238</superscript>U activity ratio, and <superscript>230</superscript>Th ages (corrected) (corrected by assuming the initial <superscript>230</superscript>Th/<superscript>232</superscript>Th ratio of the average crust value). The recommended values with the uncertainties (2σ) of these two gypsum RMs, <superscript>238</superscript>U content = 1844 ± 39 ng g<superscript>−1</superscript>, δ<superscript>234</superscript>U = 229.3 ± 3.9‰, <superscript>230</superscript>Th/<superscript>238</superscript>Uactivity = 0.5741 ± 0.0036, <superscript>230</superscript>Th ages (corrected) = 66.97 ± 0.31 ka BP for PXCG-1, and <superscript>238</superscript>U content = 1636 ± 50 ng g<superscript>−1</superscript>, δ<superscript>234</superscript>U = 61.0 ± 2.4‰, <superscript>230</superscript>Th/<superscript>238</superscript>Uactivity = 0.9797 ± 0.0034, <superscript>230</superscript>Th ages (corrected) = 260.82 ± 3.39 ka BP for PXCG-2, respectively. Information values of <superscript>232</superscript>Th content, <superscript>230</superscript>Th/<superscript>232</superscript>Th atomic ratio, <superscript>230</superscript>Th age (uncorrected), and δ<superscript>234</superscript>Uinitial are also provided. PXCG-1 and PXCG-2 are the first reported gypsum age RMs for U–Th dating, making them a useful complement to the widely distributed carbonate age reference materials for U–Th disequilibrium dating in Pleistocene–Holocene deposits. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 02679477
- Volume :
- 39
- Issue :
- 6
- Database :
- Complementary Index
- Journal :
- JAAS (Journal of Analytical Atomic Spectrometry)
- Publication Type :
- Academic Journal
- Accession number :
- 177683664
- Full Text :
- https://doi.org/10.1039/d4ja00067f