Development of migmatites and the role of viscous segregation in high-T metamorphic complexes: Example from the Ryoke Metamorphic Complex, Mikawa Plateau, Central Japan
Development of migmatites and the role of viscous segregation in high-T metamorphic complexes: Example from the Ryoke Metamorphic Complex, Mikawa Plateau, Central Japan
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混合岩的形成和高温变质杂岩中粘性偏析的作用：以日本中部三河高原 Ryoke 变质杂岩为例
DOI：
10.1016/j.lithos.2009.11.012
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发表时间：
2010
期刊：
影响因子：
3.5
通讯作者：
K. Miyazaki
中科院分区：
文献类型：
--
作者：
K. Miyazaki
日本中部三川高原的良奥变质杂岩包含保存完好的白垩纪高温（高t）变质时期形成的地质和热构造。这些结构可以用普遍的熔体迁移模型来解释。然而，熔体的估算通量远远高于长英质熔体压实流的预期通量。因此，需要额外的构造力和/或熔体分离到脉网或层。本文介绍了单剪切变形下非混相粘性流体结构演化的数值模拟结果，并讨论了粘性偏析在热地壳中普遍熔体流动中的作用。非混相黏性流体的单剪切变形数值模拟结果表明，低黏性流体分离成透镜状和层状。这种偏析是一种粘性偏析，它的发生是为了使系统中的能量耗散最小化。能量耗散率与粘度成正比。因此，这一过程有望普遍发生在粘度差较大的非混相粘性流体中，是部分熔融岩石中熔体聚焦的重要过程。数值模拟得到的构造与混杂岩相似。模拟结果表明，在部分熔融的岩石中，随机分布的熔体会分裂成透镜状或分层状，并发生渐进的单剪切变形。变形强化偏析过程中，熔体网络会动态形成。如果这一过程在热地壳中以小到大的尺度发生，由于浮力的作用，熔体将有效地向上输送。在高t变质杂岩中，低构造水平普遍存在的杂岩可能代表了地壳尺度黏性分离形成的“化石”熔融路径。
The Ryoke Metamorphic Complex of the Mikawa Plateau, Central Japan, contains well-preserved geological and thermal structures formed during Cretaceous high-temperature (high-T) metamorphism. These structures can be explained by a pervasive melt migration model. However, the estimated flux of melt is much higher than that expected for compaction flow of felsic melt. An additional tectonic force and/or melt segregation to network of veins or layers is therefore required. This paper presents the results of numerical modeling of the structural evolution of immiscible viscous fluids under simple-shear deformation, and discusses the role of viscous segregation in enabling pervasive melt flow in hot crust. The results of numerical modeling of simple-shear deformation of immiscible viscous fluids reveal that low-viscosity fluids segregate into lenses and layers. This segregation is a type of viscous segregation that takes place to minimize the dissipation of energy in the system. The rate of energy dissipation is proportional to viscosity. Therefore, this process is expected to occur universally in immiscible viscous fluids with large viscosity contrasts, and is an important process in focusing melt in partially melted rocks. The structures produced by the numerical simulation are similar to those of migmatites. The simulation results suggest that melts distributed randomly in partially melted rock will segregate into lenses or layers with progressive simple-shear deformation. During deformation-enhanced segregation, a melt network will form dynamically. If this process occurs at small to large scales in the hot crust, melts will be effectively transported upward due to buoyancy forces. It is possible that pervasive migmatites at low structural levels within high-T metamorphic complexes may represent “fossil” melt pathways formed by crustal-scale viscous segregation.
日本西南部 Ryoke 变质带的热演化：构造和数值模拟：评论
DOI：
--
发表时间：
2002
期刊：
The Island Arc 11
影响因子：
--
作者：
Yasutaka Y;Wallis S;Ikeda T
通讯作者：
Ikeda T