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Geoscience ›› 2025, Vol. 39 ›› Issue (03): 704-714.DOI: 10.19657/j.geoscience.1000-8527.2024.042

• Machine Learning and Its Applications in Mineralogy • Previous Articles     Next Articles

Research on the Atomic Level Structure Effects by Rare Earth Elements Substitutions in Allanite of Different Occurrence

XU Jingjing1,2(), LI Lin1,2,*(), YANG Xiaonan3   

  1. 1. Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing 100083, China
    2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Beijing), Beijing 100083, China
    3. The Geological Museum of China, Beijing 100034, China
  • Online:2025-06-10 Published:2025-07-03
  • Contact: LI Lin

Abstract:

Allanite is a common accessory phase in granite, skarn and granite pegmatite. As the major carrier of light rare earth elements (LREE) and trace elements such as Th, U and Sr, allanite can control LREE content well within the critical temperature range of the subduction zone. The effect of changes that its composition to structure have directive influence to the research of earth science. This paper summarise the characteristics of the cell parameters of the three epidote group minerals contain allanite, epidote and zoisite through a series systematic structural and chemical compositional analyses. Such as single-crystal X-ray diffraction (XRD), powder X-ray diffraction, and LA-ICP-MS. We discuss the effects of composition on the structure in the epidote group minerals on the basis of the series of analyses. According to experimental data comparisons, as REE3+ substitutes for Ca2+ and occupies the A2 site, the unit cell parameters a, b, c and V of the epidote-group minerals exhibit corresponding increases. The change in unit cell volume is particularly significant, expanding from 457.92 Å3 to 479.93 Å3, representing a volume increase of approximately 4.8%. Additionally, the (110), ($31\overline{1}$311¯), (222+123+114), (322+$42\overline{4}$424¯), and (307) lattice planes of allanite can indirectly reflect the content and occupancy of REEs within the mineral structure.This study investigates the crystal structure and chemical composition of allanite, revealing the regulatory mechanism of rare earth elements (REEs) substituting for Ca2+ and its geochemical significance.

Background collection

Key words: allanite, REE, crystal structure, cell parameters, polyhedral volume

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