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首页> 外文期刊>Journal of geodynamics >Microstructures and crystallographic preferred orientations of omphacite in Alpine eclogites: implications for the exhumation of (ultra-) high-pressure units
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Microstructures and crystallographic preferred orientations of omphacite in Alpine eclogites: implications for the exhumation of (ultra-) high-pressure units

机译：高山榴辉岩中辉绿岩的微观结构和晶体学优选取向：对（超）高压单元掘出的影响

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Microstructures and crystallographic preferred orientations (CPOs, textures) of omphacite within eclogites from distinct (ultra-) high-pressure units of the Alps were analysed in order to constrain the deformation conditions during and after high-pressure metamorphism. Especially the omphacite CPOs bear significant details for the reconstruction of the deformational evolution of several units. CPOs from the Austroalpine Koralm-Saualm Complex correspond to S-type fabrics, related to a deformation geometry within the flattening field. This geometry is documented by the shape fabrics, too. Textures described from the Dora Maira Massif show L > S- and L-type CPO fabrics, indicating a plane strain to constrictional deformation geometry. The CPOs from the Adula Nappe may all be described in terms of very well developed L-type fabrics formed within the constrictional field. Constrictional strain (axial elongation) is interpreted to have started at the peak of high-pressure metamorphic conditions and was continued along the retrograde path. Omphacite CPOs from the Eclogite Zone of the Tauern Window show a continuous transition from S- to L-type fabrics, corresponding to the transition from coarse-grained eclogites to finegrained eclogite mylonites. This evolution is related to the final phases of the prograde evolution and coincides with a transition from a flattening to a constrictional deformation geometry. This is indicated by the shape fabrics, too. The constrictional geometry prevailed along the retrograde section of the PT path. The evolution of microstructures and CPOs is assumed to correlate with the deformation geometry, which is directly linked with the mechanisms of exhumation. S-type fabrics predominantely occur within eclogites exhumed by crustal extension, in particular the Koralm-Saualm Complex. L > S- and L-type fabrics predominantely occur within eclogites exhumed by extrusion within a low-angle corner ("subduction channel"), in particular the Dora Maira Massif, the Adula Nappe, and the Eclogite Zone. S-type CPOs from the Eclogite Zone were formed along the prograde path and are assumed to indicate compressional deformation related to the burial of this unit.
机译：为了限制高压变质过程中和变形后的变形条件，对阿尔卑斯山不同（超）高压单元的榴辉岩中辉绿岩的微观结构和晶体学优选取向（CPO，织构）进行了分析。尤其是绿辉石CPO在重建几个单元的变形演化方面具有重要的细节。来自Austroalpine Koralm-Saualm Complex的CPO对应于S型织物，与展平场中的变形几何形状有关。该几何形状也通过形状织物来记录。从Dora Maira地块描述的纹理显示L> S和L型CPO织物，表明平面应变到收缩变形几何形状。来自Adula Nappe的CPO都可以用在狭窄领域内形成的非常发达的L型织物来描述。收缩应变（轴向伸长）被认为是从高压变质条件的峰值开始的，并一直沿逆行路径继续。来自Tauern窗的榴辉岩区的绿辉石CPO显示出从S型到L型织物的连续过渡，这对应于从粗粒榴辉岩到细粒榴辉岩my石的转变。这种演变与渐进演化的最后阶段有关，并且与从扁平变形到收缩变形的几何形状相吻合。这也由形状织物表示。收缩几何沿PT路径的逆行段占主导地位。假定微结构和CPO的演变与变形几何相关，而变形几何与掘尸机制直接相关。 S型织物主要存在于被地壳扩展发掘的榴辉岩中，特别是在Koralm-Saualm Complex中。 L> S和L型织物主要发生在通过挤压在低角度拐角处（“俯冲通道”）挤出的榴辉岩中，特别是在Dora Maira Massif，Adula Nappe和榴辉岩带中。来自榴辉岩带的S型CPO沿着前进路径形成，并被认为表明与该单元的埋葬有关的压缩变形。

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