Abstract

Quantitative thermobarometry of garnet + biotite + sillimanite f cordierite pelitic assemblages from the Canigou massif, and constraints based on consideration of high-grade metapelitic reaction equilibria, indicate that peak temperatures during Hercynian metamorphism reached 725 ± 25°C at depths of 16 = 2 km (4.5 ± 0.5 kbar). This corresponds to an average peak geothermal gradient of 45–50°C km−1, which is in broad agreement with results from studies of granulite-facies assemblages in the Pyrenees, but is significantly lower than gradients proposed for some other amphibolite-facies areas in the terrane. It is suggested that the claims by numerous authors for peak Hereynian geothermal gradients in the Pyrenees in excess of 70–100°C km−1 fail to consider the effects of post-metamorphic attenuation of metamorphic sequences and the unreliable nature of P estimates made in the absence of suitable assemblages for quantitative thermobarometry.

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