Natural gem quality orthopyroxene crystals were experimentally dehydrated between 720 °C and 1020 °C, varying silica activity (buffered by olivine-orthopyroxene or orthopyroxene-quartz), oxygen fugacity (log f_O2 relative to the quartz-fayalite-magnetite buffer (QFM) of around +1, -1 and -7) and composition (two different orthopyroxene types) to study these parameters' effects on both the diffusivity of hydrogen and the Fourier transform infrared (FTIR) spectra in orthopyroxene. Hydroxyl profiles were measured across partially dehydrated grains, from which H diffusion coefficients were extracted. Fitting these H diffusion coefficients to the isobaric Arrhenius relationship, log D = log D₀ – E_a/(2.303RT), gives log D₀ of -5.11, -4.93 and -5.52 m²/s, and E_a of 139, 149 and 125 kJ mol^-1 for the [100], [010] and [001] axes, respectively, where D₀ is the pre-exponential factor (m²/s), E_a is the activation energy (kJ mol^-1), R is the universal gas constant (kJ mol^-1 K^-1) and T is the temperature (K). Hydrogen diffusivities at ∼ΔQFM-1 and 700 °C to 1000 °C are between log D = -12.5 to -10.4 m²/s. This is similar to the fastest H diffusivity measured in olivine, suggesting diffusion primarily by a ‘proton-polaron’-type mechanism, whereby the movement of protons through the crystal is associated with Fe redox, with the net result being that dehydration should be accompanied by Fe oxidation. The determined diffusion coefficients are ∼0.3 log units faster than those determined in H-²H self-diffusion experiments (Stalder and Behrens, 2006). The effect of a_SiO2 and ƒ_O2 (between ∼ΔQFM-1 to ∼ΔQFM+1) is only minor or within uncertainty. These data were applied to a natural sample from a xenolith from Las Cumbres in Chilean Patagonia, where orthopyroxene shows >500 µm H loss profiles in length, and olivine shows 50-200 µm Fe-Mg, Y, Ti, V and Sc profiles on millimeter sized crystals. Modelled timescales calculated from a H profile in orthopyroxene, using our H diffusivities along with published values, are considerably shorter (minutes to days) compared to those derived from Fe-Mg inter-diffusion in olivine (weeks to years) from the same xenolith using Fe-Mg diffusivities in olivine. This discrepancy is likely due to H-loss in the natural orthopyroxene representing the timescale between the onset degassing of the host magma and emplacement, whereas Fe-Mg inter-diffusion records the time elapsed between xenolith entrainment and final emplacement. This supports previous assertions that H diffusion in orthopyroxene is sufficiently fast such that many xenolith-hosted orthopyroxene crystals may have suffered significant re-equilibration with the host magma H₂O prior to later degassing-induced H-loss.

在720°C到1020°C之间通过实验对天然宝石品质的邻苯二酚晶体进行脱水，改变了二氧化硅的活性（受橄榄石-邻苯二酚或邻苯二酚-石英缓冲），氧逸度（相对于石英-铁橄榄石-磁铁矿缓冲液（QFM）的log f _O2（大约+ 1，-1和-7）和成分（两种不同的邻苯二酚类型）来研究这些参数对氢的扩散率和邻苯二酚中的傅立叶变换红外（FTIR）光谱的影响。测量了部分脱水谷物中的羟基分布，从中提取了H扩散系数。将这些H扩散系数拟合为等压Arrhenius关系，log D = log D ₀ – E _a /(2.303RT），得出log D ₀对于[100]，[010]和[001]轴，分别为-5.11，-4.93和-5.52 m ² / s的E _a分别为139、149和125 kJ mol ^-1，其中D ₀是-指数因子（m ² / s），E _a是活化能（kJ mol ^-1），R是通用气体常数（kJ mol ^-1 K ^-1），T是温度（K）。在〜ΔQFM-1和700°C至1000°C下的氢扩散率在log D = -12.5至-10.4 m ^2之间/ s。这类似于在橄榄石中测得的最快的H扩散率，表明扩散主要是通过“质子-极化子”型机制进行的，其中质子穿过晶体的运动与Fe氧化还原有关，最终结果是应伴随脱水被铁氧化。所确定的扩散系数比H- ² H自扩散实验（Stalder和Behrens，2006）确定的扩散系数快约0.3 log单位。一个效果_的SiO2和ƒ _O2（在〜QQ-1至〜QFM + 1之间）仅很小，或在不确定范围内。这些数据应用于来自智利巴塔哥尼亚Las Cumbres的异种石的天然样品，其中邻二甲苯的长度损失> 500 µm，橄榄石显示50-200 µm的Fe-Mg，Y，Ti，V和Sc分布。毫米大小的晶体。与我们利用相同的异种岩体从橄榄石中的Fe-Mg相互扩散（几周到几年）得出的模型时间尺度相比，使用邻二甲苯的H曲线计算的模型时标（使用我们的H扩散率和已公开的值）要短得多（几分钟到几天）。 Fe-Mg在橄榄石中的扩散性。这种差异很可能是由于天然邻二甲苯中的H损失代表了主体岩浆开始脱气与位置之间的时间尺度，Fe-Mg互扩散记录了异种石屑夹带和最终置入之间的时间。这支持了先前的论断，即氢在邻苯二茂基中的扩散足够快，以至于许多异种体承载的邻苯二茂基晶体可能与主体岩浆H发生了显着的重新平衡。₂ O之后再进行脱气引起的H损失。