Emplacement of eo-alpine high-pressure rocks in the austroalpine Ötztal complex (texel group, italy/austria) / emplacement de roches de haute pression éo-alpines dans le complexe austroalpin de l'Ötztal (massif de texel, italie du nord)

In the southeastern Ötztal basement remnants of eo-Alpine high-pressure metamorphism as well as deformation related to the emplacement of these eclogites are preserved. The eo-Alpine age of the two main ductile deformation phases is constrained by Ar-Ar and Rb-Sr mica cooling ages of about 80 Ma, providing a lower, and by deformed Permo-Mesozoic rocks, providing an upper time limit. While high-pressure minerals (M₁) are aligned along structures of the first deformation phase (D₁), subsequently grown amphibolite facies minerals (M₂) are late-to post-kinematic with respect to the third phase (D₃). D, is characterized by non-coaxial deformation producing an E-W oriented stretching lineation, the younger phases D₂ and D₃ by folding, where the older set of folds strikes N-S, the younger one E-W. These results imply a basic change of tectonic movement direction during the eo-Alpine event. Structural and petrological evidences favour a two-stage exhumation model, where tectonic exhumation (D₁, D₂ and D₃) is correlated with the first stage, statically overprinted under amphibolite facies conditions (M₂). As there is no evidence of significant deformation after this stage, erosion and surface uplift most probably represent the relevant processes for the last part of the exhumation path. During this stage the high-pressure rocks were exhumed from amphibolite facies conditions to the surface.