The role of hot crust in mountain building: Testing the alpha-beta quartz transition as a crustal geothermometer

在控制地壳运动的所有物理参数中，温度可以说是最难精确确定的。与此同时，温度控制着重要的过程，如熔融（岩浆的产生），变形过程从脆性（通常伴随着地震）转变为韧性（没有地震）的深度，以及改变地壳密度的矿物之间的相变，使其更有可能抬升高地（密度较低）或沉入地幔（密度较高）。因此，确定地壳温度的能力对于预测大范围的地壳行为是重要的。石英占地壳的很大一部分，在已知的温度下，它的矿物结构会发生变化。这种变化，也就是温度，可以通过探测穿过材料的地震波速度的特征模式来测量。我们使用地震技术的系统组合来确定石英转变和确定地壳温度。, # 945;-到&amp；#946；石英的相变发生在一个狭窄的温度范围内，即从地球上看到的压力在580至800°C之间。S表面至~40 km深度。与熔化边界和成分边界等其他机制不同，相变会导致压缩地震速度（Vp）急剧增加，但不会伴随切变速度（Vs）的对比。在热英质中地壳造山带中，可以探测到产生P反射但没有P - S转换的界面，推断出的温度和压力与&amp；#945;-&#946；石英过渡和无熔融。本研究采用一套系统的远震观测技术（测试P-S转换和P-P反射/转换来自同一不连续面），结合岩石物理模拟研究了喜马拉雅-西藏和台湾造山带的地壳温度及其地球动力学后果；如果成功，该方法可以在世界范围内广泛应用于控制造山带温度。

Of all physical parameters that control the behavior of the Earth's crust, temperature is arguably the most difficult to determine accurately. At the same time, temperature controls important processes such as melting (generation of magma), the depth at which deformation processes change from brittle (usually accompanied by earthquakes) to ductile (without earthquakes), and phase transitions between minerals that change the density of the crust, making it more likely to lift high terrain (less dense) or sink into the mantle (denser). The ability to determine crustal temperature is therefore important for the prediction of a wide range of crustal behaviors. Quartz makes up a large portion of the Earth's crust and undergoes a change in mineral structure at a known temperature. This change, and therefore the temperature, can be measured by detecting a characteristic pattern in the velocity of seismic waves traversing the material. We use a systematic combination of seismic techniques to pinpoint the quartz transition and determine crustal temperature.The α- to β-phase transition of quartz occurs in a narrow temperature range that lies between 580 to 800°C for pressures seen from the Earth?s surface to ~40 km depth. The phase transition generates a sharp compressional seismic velocity (Vp) increase with no accompanying shear velocity (Vs) contrast, unlike other mechanisms such as melting and compositional boundaries, which create contrasts in both Vp and Vs. The hypothesis tested in this study is: In orogens with a hot felsic middle crust, an interface can be detected that generates P reflections but no P to S conversions, and the inferred temperature and pressure are consistent with the presence of the α-β quartz transition and the absence of melting. This study uses a systematic set of teleseismic observation techniques (tests for the occurrence of P-S conversions and P-P reflections/conversions from the same discontinuity) in combination with petrophysical modeling to investigate crustal temperature and its geodynamic consequences in the Himalaya-Tibet and Taiwan orogens; if successful, the method can be widely applied to constrain the temperature of orogens worldwide.