EGU2020-12962
https://doi.org/10.5194/egusphere-egu2020-12962
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

The study of the valence and distribution of radiogenic Pb in monazite by using XPS and TEM

Xu Tang, Qiu-li Li, and Lin-xin Gu
Xu Tang et al.
  • Institute of Geology and Geophysics, Chinese Academy of Sciences, Electron Microscopy Laboratory, China (tangxv@mail.iggcas.ac.cn)

Monazite((Ce,Y,La,Th)PO4) is an important phosphate mineral and is one of the widely used minerals for U-Th-Pb dating in geochronology. In this study, we have examined the crystallinity, the valence and coordination of radiogenic Pb in a natural RW-1 monazite standard (ThO2 up to13.5 wt% and Pb up to ~5000 ppm) with a 207Pb/235U age of 904.15 ± 0.26 Ma from a Norwegian pegmatite by using laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy (TEM). The Raman spectrum analysis revealed that this monazite is well crystalline and is not damaged by α-particles. The results of XPS and TEM suggest that the radiogenic Pb produced by the α-decay of U and Th is divalent and radiogenic Pb atom substitutes the Ce-site within the monazite crystal lattice. The qualitative analyses conducted on the HAADF-STEM data reveal heterogeneous distribution of radiogenic Pb within the monazite crystal lattice. This is the first work on the determination of the oxidation state, the atomic location and distribution of radiogenic Pb in a natural monazite (CePO4). The deeply study of radiogenic Pb in monazite at the nanoscale and atomic scale provides a good insight for us to understand the mechanisms of nano-isotopic mobility and the nano-geochronology  that has been poorly understood so far.

How to cite: Tang, X., Li, Q., and Gu, L.: The study of the valence and distribution of radiogenic Pb in monazite by using XPS and TEM, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12962, https://doi.org/10.5194/egusphere-egu2020-12962, 2020

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