As seismic data from the lower crust becomes more readily available, it is important to link seismic properties to the ongoing processes within lower crustal evolution. This includes high temperature, pre‐ and post‐migmatization solid state deformation as well as melt‐present deformation. We selected two tonalitic migmatites with variable former melt content (one metatexite and one diatexite) from the lower crustal Daqingshan area, northern North China Craton to assess the link between seismic properties and rock structure and rheology. Field observation along with microstructural features suggest that the characteristics of hornblende and plagioclase within the residuum of the metatexite can be used to derive information on the pre‐melt deformation. Residuum's plagioclase CPO (crystallographic preferred orientations) is consistent with high temperature dislocation creep as the main deformation mechanism; similarly, hornblende shows a strong CPO related to dislocation creep. During syn‐melt (melt present) conditions, phenocrysts of plagioclase in the metatexite's neosome and K‐feldspar and peritectic hornblende in the diatexite's neosome are present. The rheology of the rock was dominated by melt; hence is inferred to follow Newtonian flow. After melt crystallization deformation is minor but again dominated by dislocation creep. The seismic properties (seismic velocity, anisotropy, Vp/Vs ratio, etc.) for pre‐ and post‐melt have similar values expected values for solid mafic rocks, whilst the syn‐melt seismic velocities are generally lower and Vp/Vs ratios and seismic anisotropies are higher.

中文翻译：

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预先熔融，部分熔融和后固溶时斜长石蒙脱石的变形行为和推断的地震特性

随着来自下地壳的地震数据变得更容易获得，将地震属性与下地壳演化中正在进行的过程联系起来非常重要。这包括高温，在迁移之前和之后的固态变形以及在熔体中的变形。我们从华北克拉通北部大地山下地壳中选出了两种熔体含量不同的前生熔融含量的成矿辉锰矿（一种变质岩和一种透辉石），以评估地震特性与岩石结构和流变学之间的联系。现场观察以及微观结构特征表明，该变质岩残留物中的角闪石和斜长石的特征可用于获得有关预熔变形的信息。残留物 斜长石CPO（晶体学优选取向）与高温位错蠕变为主要变形机理是一致的；同样，角闪石显示出与位错蠕变有关的强CPO。在同融（存在熔体）条件下，变质岩新生物中有斜长石的隐晶石，而无辉石新生物中存在钾长石和包晶角闪石。岩石的流变学主要是融化。因此可以推论服从牛顿流。熔体结晶后变形很小，但又以位错蠕变为主。熔化前和熔化后的地震特性（地震速度，各向异性，Vp / Vs比等）的期望值与实心基性岩的期望值相近，而合成熔化地震速通常较低，而Vp / Vs比和地震各向异性较高。