Apatite serves as a notable host for diverse volatiles, but experimental data concerning the mobilities of volatiles out of its lattice remains scarce. Despite several investigations elucidating the diffusivities of F, Cl, and OH, their interplay mechanism remains poorly understood. Herein, to unveil the mobilities of hydrogen, fluorine, and carbon out of the apatite lattice and their intricate interaction mechanisms during high temperature processes, we carry out annealing experiments at 900, 1000, and 1100 °C on two apatite samples with distinct fluorine contents. Our findings indicate that along the c-axis, hydrogen diffusion coefficients surpass those of fluorine by 2–3 orders of magnitude, with lower activation energies observed. Hydrogen diffusion shows strong anisotropy, with lager diffusivities and lower activation energies along the c-axis than the a-axis. For both hydrogen and fluorine, the Durango apatite shows smaller diffusivities along the c-axis than the Imilchil apatite. Contrarily, carbon diffusion is absent in both samples at these temperatures. These differences in diffusivity may suggest that hydrogen diffuses as OH along the a-axis and as H along the c-axis, while fluorine diffusion relies on hydrogen diffusion along the c-axis. Based on these new data, the capacity of apatite to record volatiles can be evaluated. All volatiles, including hydrogen, is likely preserved within the core of apatite during thermal events from several days to years, such as rapid volcanic eruptions. However, for prolonged thermal events lasting hundreds of millions of years, apatite preserves volatiles for F, Cl and C, but not hydrogen.

中文翻译：

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高温下磷灰石中挥发物（H、F 和 C）的迁移率


磷灰石是多种挥发物的重要宿主，但有关挥发物在其晶格外的迁移率的实验数据仍然很少。尽管多项研究阐明了 F、Cl 和 OH 的扩散性，但它们的相互作用机制仍然知之甚少。在此，为了揭示磷灰石晶格中氢、氟和碳在高温过程中的迁移率及其复杂的相互作用机制，我们对两种具有不同氟含量的磷灰石样品在900、1000和1100℃下进行了退火实验。我们的研究结果表明，沿 c 轴，氢扩散系数超过氟扩散系数 2-3 个数量级，且活化能较低。氢扩散表现出很强的各向异性，沿c轴比a轴具有更大的扩散系数和更低的活化能。对于氢和氟，杜兰戈磷灰石沿 c 轴的扩散率比 Imilchil 磷灰石小。相反，在这些温度下，两个样品中均不存在碳扩散。这些扩散率的差异可能表明氢以 OH 的形式沿 a 轴扩散，以 H 的形式沿 c 轴扩散，而氟的扩散依赖于氢沿 c 轴的扩散。根据这些新数据，可以评估磷灰石记录挥发物的能力。在几天到几年的热事件（例如快速火山喷发）期间，包括氢在内的所有挥发物都可能保存在磷灰石的核心内。然而，对于持续数亿年的长期热事件，磷灰石保留了 F、Cl 和 C 的挥发物，但不保留氢。