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Abstract Major influences on the architecture of orogens include the overall thermal conditions of orogeny (hot vs. cold) and the angle of collision (orthogonal vs. oblique). In the French Massif Central of the Variscan orogen, a cold‐orogen style crustal nappe architecture was interpreted in the Haut‐Allier, located in the core of the orogen. Based on this model, the Variscan orogenic crust is described as the superposition of three main allochthonous tectonic units juxtaposed along major thrust faults. However, based on a detailed structural analysis, we have found instead that the region is dominated by a network of anastomosing conjugate and coeval dextral and sinistral shear zones striking WNW‐ESE and ENE‐WSW, respectively. The dextral WNW‐trending shear zones are predominant, whereas the sinistral NE shear zones are mainly located in the eastern part of the massif. Between these sub‐vertical shear zones, a sub‐horizontal foliation is observed. Our results indicate that all planar fabrics were partially synchronous during suprasolidus low‐pressure‐high‐temperature conditions. Strain partitioning occurred from high‐temperature suprasolidus conditions to subsolidus retrogression and may represent orogen‐parallel flow, suggesting hot‐orogen style. These results call into question the validity of the crustal nappe model in the Haut‐Allier. Based on new structural data and related observations, we propose a new model in which metamorphic gaps between tectonic units are explained by the juxtaposition of different structural domains by displacement along strike‐slip shear zones. 

Continents are constantly moving, and sometimes they collide. When continents collide, they crumple, and thicken. Mountain ranges form in this “crash zone.” Deep rocks at the bottom of a crash zone are hot because they are so deep. Hot materials—even rocks—become weak. Hot rocks deep underground can move by flowing, even though they are mostly solid. First, they flow sideways and then upwards in large blobs. When upward-moving blobs are only a few kilometers below the surface of the Earth, they cool and harden into bell shapes (domes). Flowing rocks cause the crash zone to collapse and spread out. Continents go back to their pre-collision thickness. They are not exactly the same as before collision, though: some rocks that used to be at the bottom of the continents are now at the top! We can see these formerly deep parts of continents in rock domes all over the world.