We conducted experiments at high pressure (P) and temperature (T) to measure hydrogen solubility in plagioclase (Pl) with a range of compositions (An15 to An94). Experiments were run at 700-850 °C, 0.5 GPa, and f O 2 close to either the Ni-NiO (NNO) or iron-wüstite (IW) oxygen buffers. Experiments at 700 °C on An15 (containing 0.03 wt% FeO) reveal no dependence of H solubility on f O 2 between IW and NNO, but experiments at 800-850 °C on other compositions (with 0.3-0.5 wt% FeO) demonstrate that H solubility is enhanced by a factor of ~2 to 3 at IW compared to NNO, consistent with previous experiments by Yang (2012a) on An58. By analogy with synthetic hydrogen feldspar (HAlSi3O8), we infer that the predominant mechanism for H incorporation in Pl is through bonding to O atoms adjacent to M-site vacancies, and we propose likely O sites for H incorporation based on M-O bond lengths in anhydrous Pl structures. Increased uptake of structurally bound H at low f O 2 is explained by the formation of defect associates resulting from the reduction of Fe3+ in tetrahedral sites to Fe2+, allowing additional H to be incorporated in adjacent M-site vacancies. This mechanism counteracts the expected effect of water fugacity on H solubility. We also speculate on possible substitutions of H on tetrahedral vacancies, as well as coupled H-F substitution. Enhanced incorporation of H in Pl at low f O 2 may have implications for estimating the water content of the lunar magma ocean. However, mechanisms unrelated to low f O 2 are needed to explain high H contents in terrestrial Pl xenocrysts, such as those found in basalts from the Basin and Range.

中文翻译：

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斜长石中的氢掺入

我们在高压 (P) 和高温 (T) 下进行了实验，以测量具有一系列成分（An15 至 An94）的斜长石 (P1) 中的氢溶解度。实验在 700-850 °C、0.5 GPa 和 f O 2 下运行，接近 Ni-NiO (NNO) 或铁-方铁矿 (IW) 氧缓冲液。An15（含 0.03 wt% FeO）在 700 °C 下的实验表明，IW 和 NNO 之间的 H 溶解度对 f O 2 没有依赖性，但在 800-850 °C 下对其他成分（含 0.3-0.5 wt% FeO）的实验表明与 NNO 相比，IW 下 H 的溶解度提高了约 2 到 3 倍，这与 Yang (2012a) 之前在 An58 上的实验一致。通过与合成氢长石 (HAlSi3O8) 类比，我们推断 H 掺入 Pl 的主要机制是通过与 M 位空位相邻的 O 原子键合，我们根据无水 Pl 结构中的 MO 键长提出了可能的 H 结合位点。在低 f O 2 下结构结合的 H 的吸收增加可以解释为由于四面体位点中的 Fe3+ 还原为 Fe2+ 导致的缺陷缔合体的形成，从而允许额外的 H 结合到相邻的 M 位空位中。这种机制抵消了水逸度对 H 溶解度的预期影响。我们还推测了四面体空位上 H 可能的取代，以及耦合的 HF 取代。在低 f O 2 下，H 在 Pl 中的结合增强可能对估计月球岩浆海洋的水含量有影响。然而，需要与低 f O 2 无关的机制来解释陆地 Pl 异晶中的高 H 含量，例如在盆地和山脉的玄武岩中发现的那些。