How large are tectonic deviations from lithostatic pressure in a continent-derived, lithologically heterogeneous Alpine UHP nappe (Koralpe-Saualpe-Pohorje Complex, Austria and Slovenia)?

岩石的流变特性控制着岩石在非均匀应力场中的变形。相邻岩石强度的巨大差异不可避免地导致平均法向应力(即压力)与岩石静压力的偏差。一些理论研究表明，这种偏差可能达到数百兆帕，在这种情况下，它们可能会影响岩石压力记录。由于岩石记录的压力通常被用来根据岩石静压力到深度的换算来估计其埋藏深度，因此这种估计可能是有偏差的。另一方面，构造偏离岩石静压力的明确证据非常稀少，它们发生的规模和规模也鲜为人知。我们提出了一种新的方法，通过系统地比较不同岩石类型(主要是榴辉岩和变质岩)沿阿尔卑斯山超高压推覆的造山带垂直断面的峰值压力来评估震级。对于每种岩石类型，我们将确定峰值压力剖面作为横断面上距离的函数。如果这些剖面重合，就不会有明显构造压力的证据。如果它们表现出系统的变化，这可以解释为不同岩性的流变性的影响，最容易解释的是构造压力。以前的文献数据表明，在奥斯特罗阿尔卑斯山的科拉尔佩-索尔佩-波霍耶复合体中，情况可能确实如此。第二种方法是调查在刚性透镜和被较弱基质包围的层的近场中是否存在露头尺度的构造控制的构造压力变化。我们将使用一种简单的温压方法来研究Koralpe-Saualpe-Pohorje杂岩的样品，这种方法尽可能不依赖复杂的矿物反应。如果岩石记录没有提供构造压力的证据，这将符合应用岩石静压力到深度转换的地球动力学模型。如果是这样的话，在运动学和地球动力学模型中，构造偏离岩石静压力的可能性也应该被考虑到岩性多样化(超)高压单元的其他情况。在运动学恢复造山带平行剖面时，我们将考虑潜在的构造超压，以限制Koralpe-Saualpe-Pohorje杂岩的最大埋藏深度。通过这次恢复，我们的具体目标是估计白垩纪阿尔卑斯山俯冲带中Koralpe-Saualpe-Pohorje杂岩的运动速度，以及可能被俯冲而不返回地表的大陆地壳的数量。这些对EO-阿尔卑斯山俯冲带的估计也可能让我们了解大陆地壳在阿尔卑斯山下方的板块中所占的比例，这些板块将在2017年的SPP中通过地震学方法更详细地解决。

The rheological properties control how rocks deform in a non-uniform stress field. Large differences in the strengths of neighbouring rocks inevitably lead to a deviation of the mean normal stress (i.e. the pressure) from lithostatic pressure. Several theoretical studies have shown that such deviations may reach hundreds of MPa in which case they may influence the petrological pressure record. Since pressures recorded by rocks are commonly used for estimating their burial depth according to a lithostatic pressure-to-depth conversion, such estimates may be biased. On the other hand, unambiguous evidence for tectonic deviations from lithostatic pressure is very scarce and their magnitude and scale at which they occur are poorly known. We propose a novel approach of evaluating the magnitudes by systematically comparing peak pressures of different rock types (mostly eclogites and metapelites) along an orogen-perpendicular transect through an Alpine ultrahigh-pressure nappe. For each rock type, we will determine peak pressure profiles as a function of distance along the transect. If these profiles coincide, there will be no evidence for significant tectonic pressures. If they show a systematic shift, this can be interpreted as an effect of the rheological properties of the different lithologies and can easiest be explained by tectonic pressures. Previous literature data suggest that this may indeed be the case in the Austroalpine Koralpe-Saualpe-Pohorje Complex. A second approach is to investigate if there are outcrop-scale structurally controlled tectonic pressure variations in the near field of rigid lenses and layers surrounded by a weaker matrix. We will investigate samples of the Koralpe-Saualpe-Pohorje Complex with a straightforward thermobarometric methodology that relies as little as possible on complex mineral reactions. If the rock record does not provide evidence for tectonic pressures, this would comply with geodynamic models applying lithostatic pressure-to-depths conversion. If they do, the possibility of tectonic deviation from lithostatic pressure should also be considered for other cases of lithologically diverse (ultra)high-pressure units, both in kinematic and geodynamic models. We will account for potential tectonic overpressure when constraining the maximum burial depth of the Koralpe-Saualpe-Pohorje Complex in a kinematic restoration of an orogen-parallel cross section. By this restoration we aim specifically at estimating the rates of motion of the Koralpe-Saualpe-Pohorje Complex in the Cretaceous Alpine subduction zone and the amount of continental crust that may have been subducted without returning to the surface. These estimates for the Eo-Alpine subduction zone may also give us an idea of the proportion of continental crust in slabs that were imaged below the Alps and are to be resolved in greater detail by seismological methods in SPP 2017.