图  1  (a) 热压实验样品的几何外形展示（背景中直尺一小格代表0.5 mm长度）；(b) 硬柱石背散射电子显微镜图像，图中亮点为抛光残留碎片，暗色为孔隙；(c) 硬柱石在200～1 000 cm⁻¹、2 000～6 000 cm⁻¹范围内的拉曼光谱（黑色）及其标准峰（蓝色）^[18] ；(d) 硬柱石的X射线衍射谱（黑色）及标准卡片（红色）^[19]

Figure  1.  (a) Geometry of the hot-pressed lawsonite sample (The scale in the background has a spacing of 0.5 mm per division.); (b) backscattered electron (BSE) image of lawsonite, where bright spots correspond to residual polishing fragments and dark areas indicate pores; (c) Raman spectra of lawsonite in the ranges 200–1 000 cm⁻¹ and 2 000–6 000 cm⁻¹ (black) together with the standard spectrum (blue)^[18] ; (d) X-ray diffraction spectrum of lawsonite (black) and the corresponding reference pattern (red)^[19]

图  2  (a) 超声实验组装及超声信号传输、反射路径；(b) 观测到的超声实验横波信号（“Anvil”表示在碳化钨锤头与Al₂O₃缓冲棒界面的反射信号，“Buffer rod”表示Al₂O₃缓冲棒与样品界面的反射信号，“Sample”表示样品与NaCl界面的反射信号，插图为“Buffer rod”与“Sample”信号重叠）

Figure  2.  (a) Ultrasonic experimental assembly and schematic paths of ultrasonic transmission and reflections; (b) recorded shear-wave signals from the ultrasonic experiment (“Anvil” denotes the reflection at the interface between the WC anvil and the Al₂O₃ buffer rod, “Buffer rod” denotes the reflection at the interface between the Al₂O₃ buffer rod and the sample, and “Sample” denotes the reflection at the interface between the sample and NaCl; the inset shows the overlap of the “Buffer rod” and “Sample” signals.)

图  3  高压下硬柱石的晶胞体积随压力的变化及与前人研究^{[12, 14–16, 24]}的对比

Figure  3.  Pressure dependence of the unit-cell volume of lawsonite and comparison with previous studies^{[12, 14–16, 24]}

图  4  (a) 硬柱石的纵、横波速度随压力的变化，(b) 体积模量和剪切模量随压力的变化（图中黑色方块根据Cook方法得到，实线采用有限应变方程拟合得到）

Figure  4.  (a) P- and S-wave velocities of lawsonite as a function of pressure; (b) bulk and shear moduli of lawsonite as a function of pressure (Black squares denote data obtained using the Cook method, while the solid line represents the fitted finite strain curve.)

图  5  室温下硬柱石及其他矿物的(a) 纵波速度、(b) 横波速度以及(c)$ {v}_{\text{P}}/{v}_{\text{S}} $随压力的变化关系（图中红色数据来自本研究，黑色数据点为前人结果，Gar：石榴石^[26]，Omp：绿辉石^[27]，Law：硬柱石^[12]，Coe：柯石英^[28]，Qtz：石英^[29]，Amp：角闪石^[30] ）

Figure  5.  Pressure dependence of (a) P-wave velocity, (b) S-wave velocity, and (c) $ {v}_{\text{P}}/{v}_{\text{S}} $ for lawsonite and other minerals at room temperature (Red symbols represent data from this study. Black data points denote findings from prior research. Gar: garnet^[26]; Omp: omphacite^[27]; Law: lawsonite^[12]; Coe: coesite^[28]; Qtz: quartz^[29]; Amp: amphibole^[30].)

图  6  沿不同理想化地温梯度条件下硬柱石的纵波和横波速度以及$ {v}_{\text{P}}/{v}_{\text{S}} $随压力的变化（实线）及其与PREM模型的对比（虚线）

Figure  6.  Pressure dependence of P-wave velocity, S-wave velocity, and $ {v}_{\text{P}}/{v}_{\text{S}} $ of lawsonite along different idealized geothermal gradients (solid lines) and their comparison with the PREM model (dashed lines)

图  7  计算地温梯度与不同俯冲带热状态示意图（左右两侧蓝色以及红色区域分别对应日本东北（冷俯冲）和日本西南（暖俯冲）洋壳地温梯度范围^[33]，黑色实线为硬柱石的稳定域^[34]，蓝色曲线为本研究计算所用代表性地温梯度线^[35]）

Figure  7.  Schematic illustration of calculated geothermal gradients and thermal states of different subduction zones (The blue and red shaded regions on the left and right represent the ranges of oceanic crust geotherms for NE Japan cold subduction and SW Japan warm subduction, respectively^[33]. The black solid line denotes the stability field of lawsonite^[34], and the blue curve indicates the representative geothermal gradient adopted in this study^[35].)

图  8  沿俯冲地热计算的纵波和横波速度剖面（底图为各矿物在相应压力-温度条件下的体积分数，根据Hernandez-Uribe等^[13]的研究结果修改）

Figure  8.  Calculated P- and S-wave velocity profiles along the subduction geotherm (The background shows the volume fractions of each mineral phase under the corresponding pressure-temperature conditions, modified after Hernandez-Uribe, et al.^[13])