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Évolution structurale et thermique des Calédonides d’Écosse

Abstract : Colisionnal wedges are typically described as analogue to frictio- nal superficial wedges. The frictional wedges display localized deformations propagating in sequence and rooting on a basal decollement level. Howe- ver rocks mechanics predicts that, below the brittle-ductile transition, rocks behvior change drastically and deformation occurrs both with localized and distributed patterns, thus suggesting possible first order differences between crustal-scale wedge and accretionary prisms. To better understand how a ductile wedge is built, the present study focuses on the Northern Highglands Caledonian nappe stack to characterize when and how they accreted one to another. To capture this deep stacking, occurring at temperatures above 400-500 ̊C, we performed high temperature thermochronolgy : SIMS U-Pb dating of apatites, which happens to be a powerful tool for distinguishing age populations in polymetamorphic terranes, and 40Ar/39Ar dating on mi- cas. U-Pb data suggest a cooling at the scale of the wedge near 415-400 Ma. Our 40Ar/39Ar data is consistent with this cooling in the internal part of the wedge near 415 Ma. The Naver thrust appears to be the older active shear zones, that ceased early in the Scandian sequence. Then, 40Ar/39Ar data sug- gest that ductile deformation occurred coevally on the Ben Hope and Moine shear zones from 440 Ma to 415 Ma, before final localization on the Moine thrust and exhumation and cooling of the whole stacked sequence before 410 Ma.
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  • HAL Id : tel-03294803, version 1

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Ella Jewison. Évolution structurale et thermique des Calédonides d’Écosse. Sciences de la Terre. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS613⟩. ⟨tel-03294803⟩

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