Inspired by exhumed subduction shear zones that commonly exhibit block-in-matrix characteristics (mélanges), we create synthetic models with different proportions of strong clasts within a weak matrix and compare them to natural mélange outcrops. Using 2D Finite Element visco-plastic numerical simulations in simple shear kinematic conditions, we determine the effective rheological parameters of such a two-phase medium, comprising blocks of basalt embedded within a wet quartzitic matrix. We treat our models and their structures as scale-independent and self-similar and upscale published field geometries to km-scale models, compatible with large-scale far-field observations. Like in the laboratory deformation experiments, we vary confining pressures, temperatures and strain rates to evaluate effective rheological estimates for a natural subduction interface. As expected, the block-in-matrix ratio affects deformation and strain localization, with the effective dislocation creep parameters (A, n, and Q) varying between the values of the strong and the weak phase, in cases where both materials deform by viscous creep. At conditions where the blocks are frictional and the matrix viscous, the mélange deforms effectively by dislocation creep but the locally frictional deformation of the blocks leads to higher stresses. This results in an effective value of the stress exponent, n, greater than that of both pure phases, as well as an effective rate-dependent viscosity lower than that of the weak phase. In combination with an appropriate evolution law for the block concentration of a mélange, our effective rheology parameters may be used in large scale geodynamic models as a proxy for a heterogeneous subduction interface.

受通常表现出块状基质特征（混杂岩）的高架俯冲剪切带的启发，我们创建了在弱基质中具有不同比例的强碎屑的合成模型，并将其与天然混杂岩露头进行了比较。在简单的剪切运动学条件下，使用2D有限元粘塑性数值模拟，我们确定了这种两相介质的有效流变参数，包括埋在湿石英基体中的玄武岩块。我们将模型及其结构视为独立于比例的，自相似的和已发布的高级场几何，直至千米级模型，与大规模远场观测值兼容。像在实验室变形实验中一样，我们改变围压，温度和应变率，以评估自然俯冲界面的有效流变估计值。不出所料，矩阵的比例会影响变形和应变局部化，并具有有效的位错蠕变参数（如果两种材料都因粘性蠕变而变形，则A，n和Q）会在强相和弱相的值之间变化。在块体摩擦且基体粘性的条件下，混杂体会因位错蠕变而有效变形，但块体的局部摩擦变形会导致较高的应力。这导致应力指数n的有效值大于两个纯相的有效值，并且有效速率依赖的粘度低于弱相。结合针对混杂岩块体浓度的适当演化规律，我们的有效流变参数可用于大规模地球动力学模型中，作为非均质俯冲界面的代理。