Abstract Analogue sand-box experiments have been set up to illustrate and analyze the control exerted by lithological heterogeneities on the evolution of a model fold-and-thrust belt (FTB). The structural architecture within many FTBs is highly sensitive to pretectonic obstacles (e.g., basement highs or intrusive bodies). To address FTB evolution with emphasis on the latter, we perform a series of experiments that include tabular cohesive blocks surrounded by a layered sandpack of negligible cohesion. Two degrees of cohesion are tested (low vs high cohesion) as well as different geometrical boundary conditions (longer axis parallel vs oblique relative to the main far-field stress). Modeling results show a tendency of sequential faults to avoid rigid obstacles, enhancing frontal accretion and propagation of the deformation front. Structural traces have arcuate patterns in map-view, strongly consistent with the geometry of the underlying block/obstacle. High-cohesion models show major deviations on the structural pattern with respect to models with low-cohesion blocks. We find that the rheological contrasts between rock types have an important effect on the structure of the upper crust, controlled by the degree of the contrast and the geometry (orientation) of the discordant block. An interesting aspect of our results is that orientation of the block plays a considerable role on whether new thrusts cut the block or stresses propagate towards the foreland through the cohesive body. Block obliquity also influences the generation of back-thrusts. These features are compared to natural cases as well as to other physical models of FTBs. We suggest that irregular structural patterns in FTBs may shed light on the presence of buried rock bodies (intrusive bodies, metamorphic complexes or crystalline basement highs) within the components of the deformed rock sequence.

中文翻译：

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粘性块体取向对褶皱冲断带构造纹路的影响——基于类比建模的评价

摘要 建立了模拟沙箱实验来说明和分析岩性非均质性对模型褶皱冲断带（FTB）演化的控制。许多 FTB 内的结构结构对构造前障碍（例如，地下室高位或侵入体）高度敏感。为了解决 FTB 演化并强调后者，我们进行了一系列实验，其中包括由可忽略的内聚力的分层沙包包围的板状内聚块。测试了两个内聚度（低与高内聚力）以及不同的几何边界条件（长轴平行与相对于主要远场应力的倾斜）。建模结果表明，连续断层有避开刚性障碍物的趋势，增强了变形锋的锋面增生和传播。结构轨迹在地图视图中具有弧形图案，与底层块/障碍物的几何形状高度一致。高内聚模型相对于具有低内聚块的模型显示结构模式的主要偏差。我们发现岩石类型之间的流变对比对上地壳的结构有重要影响，受对比程度和不协调块体的几何（取向）控制。我们的结果的一个有趣的方面是，块体的方向在新的推力是否切割块体或应力通过粘性体向前陆传播方面起着相当大的作用。块倾角也会影响反推力的产生。这些特征与自然情况以及 FTB 的其他物理模型进行了比较。