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The 200 Ma, 24-km-diameter Rochechouart impact structure was formed in granitic intrusive and metamorphic rocks of Variscan age (400–300 Ma) close to the margin of the Mesozoic sea. Fractured basement and autochthonous breccias form a several-decameter-thick semicontinuous zone over an 18–20-km-diameter zone. Impact melt rocks, suevite, and polymict lithic breccia are spread over an ~15 km inner zone, forming a centro-symmetric deposit inclined 0.6°N. No topographic expression of the central uplift exists. The crater floor is at the same elevation (~±50 m) over a zone at least 20 km in diameter, corresponding to the central part of the original crater. The pre-erosional diameter of the crater is probably larger than previously thought and possibly reached 40–50 km. The structure appears much less eroded than previously thought, as the sequence of crater fill is complete as exposed near Chassenon. The suevite in Chassenon is capped by an ash-like horizontal deposit of very glass-poor, fine-grained, lithic debris derived from basement rocks. Material with similar grain size and composition is observed in centimeter- to meter-thick multilayered glass-bearing intercalations (dikes) cutting through the suevite. The integrity of the Chassenon sequence strikingly contrasts with the age and morphology of the structure, implying that a rapid and thick sedimentary deposit has covered the crater to protect it from erosion. The impactoclastic top deposit also firmly constrains the thickness and volume of the initial crater fill, which appear extremely depleted (by a factor of 5 or more) compared with similar-sized impact structures and model-based calculations. This anomaly remains unexplained. All the impactites, including the glass-poor and glass-free impactites, are characterized by a prominent K-metasomatism signifying pronounced postimpact hydrothermal activity. Exposed in isolated occurrences from the center to the periphery of the inner 15-km-diameter zone, impact melt rocks are extremely unlikely to have formed a continuous sheet. They display a large variety of textures, grading from pure melt rock into basal suevite, which are distinct in composition, texture, and setting from the main suevite body forming the top of the impact deposit. Heterogeneity and relative inefficiency in mixing are characteristic of the whole impact deposit, resulting in heterogeneous melts at the scale of hand specimens, but also at the kilometer scale, as suggested by close ties between the composition of melt-bearing rocks and the subjacent target rocks.

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