Abstract. Subduction and exhumation are key processes in the formation of orogenic systems across the world, for example, in the European Alps. For geophysical investigations of these orogens, it is essential to understand the petrophysical properties of the rocks involved. These are the result of a complex interaction of mineral composition and rock fabric including mineral textures (i.e. crystallographic preferred orientations). In this study we present texture-derived elastic anisotropy data for a representative set of different lithologies involved in the Alpine orogeny. Rock samples were collected in the Lago di Cignana area in Valtournenche, in the Italian Northwestern Alps. At this locality a wide range of units of continental and oceanic origin with varying paleogeographic affiliations and tectono-metamorphic histories are accessible. Their mineral textures were determined by time-of-flight neutron diffraction at the Frank Laboratory of Neutron Physics at the JINR in Dubna, Russia. From these data the elastic properties of the samples were calculated. The data set includes representative lithologies from a subduction-exhumation-setting. In subducted lithologies originating from the oceanic crust, the elastic anisotropies range from 1.4 to 5.0 % with average P-wave velocities of 7.01–8.24 km/s and VP / VS-ratios of 1.71–1.76. In the metasediments of the former accretionary prism the elastic anisotropies range from 4.7 to 8.2 %. This tectonic setting displays average P-wave velocities of 6.47–7.23 km/s and VP / VS-ratios of 1.60–1.76. Continental crust which is incorporated in the collisional orogen shows elastic anisotropies ranging from 1.8 to 2.8 % with average P-wave velocities of 6.42–6.51 km/s and VP / VS-ratios of 1.56–1.60. Our results suggest that mafic and felsic rocks in subduction zones at depth may be discriminated by a combination of seismic signatures: lower anisotropy and higher VP / VS ratio for mafic rocks, higher anisotropy and lower VP / VS ratio for felsic rocks and metasediments.

中文翻译：

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俯冲与掘进环境下岩石的弹性各向异性

摘要。俯冲和挖掘是全世界造山系统形成的关键过程，例如在欧洲阿尔卑斯山。对于这些造山带的地球物理研究，必须了解所涉及岩石的岩石物理特性。这些是矿物成分和岩石结构（包括矿物质地）（即晶体学优选的方向）之间复杂的相互作用的结果。在这项研究中，我们介绍了涉及高山造山运动的一组代表性岩性的纹理衍生弹性各向异性数据。岩石样品是在意大利西北阿尔卑斯山的瓦尔图尔嫩切的Lago di Cignana地区收集的。在这个地方，可以找到具有不同古地理隶属关系和构造变质历史的广泛的大陆和海洋单元。它们的矿物质地是通过飞行时间中子衍射在俄罗斯杜布纳JINR的弗兰克中子物理学实验室进行测定的。从这些数据计算出样品的弹性性能。数据集包括俯冲采掘设置中的代表性岩性。在源自大地壳的俯冲岩性中，弹性各向异性范围为1.4％至5.0％，平均P波速度为7.01–8.24 km / s，VP / VS比为1.71–1.76。在以前的增生棱镜的变质沉积中，弹性各向异性为4.7％至8.2％。该构造背景显示平均P波速度为6.47–7.23 km / s，VP / VS比为1.60–1.76。碰撞造山带中的大陆壳表现出的弹性各向异性范围为1.8至2。8％，平均P波速度为6.42–6.51 km / s，VP / VS比率为1.56-1.60。我们的研究结果表明，俯冲带中深部的镁铁质和长英质岩石可能通过地震特征的组合来区分：镁质岩的各向异性较低，VP / VS比值较高，镁质岩和变质沉积物的各向异性较高，VP / VS比值较低。