XIAO Zhi-bin,GENG Jian-zhen,TU Jia-run,ZHANG Ran,YE Li-juan,BI Jun-hui,ZHOU Hong-ying.In situ U-Pb Isotope Dating Techniques for Sandstone-type Uranium Deposits[J].Rock and Mineral Analysis,2020,39(2):262-273 |
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In situ U-Pb Isotope Dating Techniques for Sandstone-type Uranium Deposits |
Received:August 12, 2019 Revised:September 12, 2019 |
DOI:10.15898/j.cnki.11-2131/td.201908120129 |
Key words: sandstone-type uranium deposits U-Pb dating femtosecond laser in situ analysis LA-ICP-MS EMPA free matrix-matching |
Author Name | Affiliation | E-mail | XIAO Zhi-bin | Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China | | GENG Jian-zhen | Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China | mumu1270@163.com | TU Jia-run | Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China | | ZHANG Ran | Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China | | YE Li-juan | Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China | | BI Jun-hui | Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China | | ZHOU Hong-ying | Tianjin Center of Geological Survey, China Geological Survey, Tianjin 300170, China Key Laboratory of Uranium Geology, China Geological Survey, Tianjin 300170, China | |
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Abstract: |
BACKGROUND: Uranium mineral dating has been difficult to ascertain in mineralization chronology. With the development of in situ U-Pb isotope dating technology, it is possible to directly date ore minerals (uranium minerals). However, due to complex occurrences of sandstone-type U deposits, high requirements for laser ablation during in situ dating, and the lack of suitable external calibration standards, the dating accuracy needs to be improved. OBJECTIVES: To solve the problem of shortage of reference materials for in situ U-Pb dating of sandstone-type uranium deposit. METHODS: Two micro in situ U-Pb isotope dating methods are used for sandstone-type uranium deposits, attempting to solve the problem of no matrix-matched standards and improve the dating technology of sandstone-type uranium deposits. A laser ablation multi-collector inductively coupled plasma-mass spectrometer combined with an electron probe for micro-area in situ U-Pb isotope dating technology was established (LA-MC-ICP-MS & EMPA). RESULTS: By optimizing the analytical technique, the Chenjiazhuang granite-type uranium deposit in Qinling was tested, and the ages were consistent with those determined by the isotope dilution-thermoionization mass spectrometry (ID-TIMS), which demonstrated the feasibility of non-matrix matched reference materials for isotope dating. This method was used to data Hongqinghe and Tarangalle sandstone-type uranium deposits in the Ordos Basin. At the same time, in situ U-Pb isotope dating of Hongqinghe and Ningdong sandstone-type uranium samples was carried out by fs-laser ablation multiple-collector inductively coupled plasma-mass spectrometry (fsLA-MC-ICP-MS). In situ U-Pb isotope ages were obtained for these two deposits, indicating that femtosecond laser ablation technology had a good application prospect in the dating of sandstone-type uranium deposits. CONCLUSIONS: Combined LA-MC-ICP-MS and EMPA method can be selected for analysis of simple-texture and relatively old minerals, whereas fsLA-MC-ICP-MS method is recommended for samples requiring high spatial resolution. |
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