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<p>In the present study, the stability of zircon and xenotime-(Y) are experimentally tested by using a mixture of solids including xenotime-(Y), zircon, albite, K-feldspar, muscovite, biotite, magnetite, SiO<sub>2</sub> and different fluids, i.e. 2&#xa0;M KOH, 2&#xa0;M NaOH, Ca(OH)<sub>2</sub> solution, and CaCl<sub>2</sub> solution, to replicate a granitic alkali- and Fe-enriched environment in four Au-capsules. The experiments were conducted at 200&#xa0;MPa, 650&#xa0;°C and over 7 d. The zircon and xenotime-(Y) were altered at various degrees. The experiment with 2&#xa0;M KOH resulted in the lowest degree of zircon and xenotime-(Y) alteration, whereas experiments with 2&#xa0;M NaOH and Ca(OH)<sub>2</sub>–solution resulted in a moderate degree of alteration with well-developed porosity and partial dissolution of zircon, xenotime-(Y), and magnetite. The U-Pb ages of zircon are significantly disturbed resulting in a reverse discordant trend of data that plot along the concordia curve towards older ages. Xenotime-(Y) U-Pb ages remained mostly undisturbed. The experiment with CaCl<sub>2</sub>–solution was the most effective considering alteration of the entire mineral assemblage. Xenotime-(Y) and zircon are strongly altered with significantly disturbed U-Pb ages. Furthermore, xenotime-(Y) is partially replaced by secondary britholite-(Y). The experimental results provide new insights to our understanding of xenotime-(Y) and zircon interactions with alkali- and alkaline-rich fluids. The particular importance is that of the observed reverse discordant U-Pb ages of altered zircon and, to a lesser degree, xenotime-(Y) towards older ages along the concordia curve, which may be related to coupled U<sup>6+</sup> and Fe<sup>2+</sup> mobilization by Fe-bearing reactive fluids due to dissolution of magnetite.</p>

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Experimental alteration of zircon and xenotime-(Y) using alkali-, and alkaline-rich fluids in an Fe-enriched granitic environment

  • 期刊论文

  • 发表日期：

    2026年5月7日

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  • Fabian Tramm,
  • Bernd Wunder,
  • Bartosz Budzyń,
  • Gabriela A. Kozub-Budzyń,
  • Krzysztof Foltyn,
  • Jiří Sláma

摘要

In the present study, the stability of zircon and xenotime-(Y) are experimentally tested by using a mixture of solids including xenotime-(Y), zircon, albite, K-feldspar, muscovite, biotite, magnetite, SiO2 and different fluids, i.e. 2 M KOH, 2 M NaOH, Ca(OH)2 solution, and CaCl2 solution, to replicate a granitic alkali- and Fe-enriched environment in four Au-capsules. The experiments were conducted at 200 MPa, 650 °C and over 7 d. The zircon and xenotime-(Y) were altered at various degrees. The experiment with 2 M KOH resulted in the lowest degree of zircon and xenotime-(Y) alteration, whereas experiments with 2 M NaOH and Ca(OH)2–solution resulted in a moderate degree of alteration with well-developed porosity and partial dissolution of zircon, xenotime-(Y), and magnetite. The U-Pb ages of zircon are significantly disturbed resulting in a reverse discordant trend of data that plot along the concordia curve towards older ages. Xenotime-(Y) U-Pb ages remained mostly undisturbed. The experiment with CaCl2–solution was the most effective considering alteration of the entire mineral assemblage. Xenotime-(Y) and zircon are strongly altered with significantly disturbed U-Pb ages. Furthermore, xenotime-(Y) is partially replaced by secondary britholite-(Y). The experimental results provide new insights to our understanding of xenotime-(Y) and zircon interactions with alkali- and alkaline-rich fluids. The particular importance is that of the observed reverse discordant U-Pb ages of altered zircon and, to a lesser degree, xenotime-(Y) towards older ages along the concordia curve, which may be related to coupled U6+ and Fe2+ mobilization by Fe-bearing reactive fluids due to dissolution of magnetite.