Abstract
We produced a pressure-temperature-time path in order to determine the exhumation rate of the deepest subducted Alpine rocks. In situ dating of peak-metamorphic titanite in an eclogite facies calc-silicate rock indicates that subduction to pressures of ∼3.5 GPa was reached at 35.1 ± 0.9 Ma. Titanite formed during two decompression stages, at 1 ± 0.15 GPa and ∼0.4–0.5 GPa, and yielded ages of 32.9 ± 0.9 Ma and 31.8 ± 0.5 Ma, respectively. Combining the age data and making assumptions about the conversion of pressure to depth yield mean exhumation rates of 3.4 cm/yr and 1.6 cm/yr. These rates imply that exhumation acted at plate tectonic speeds similar to subduction, and was significantly faster than erosion. We suggest that fast exhumation is driven by a combination of tectonic processes involving buoyancy and normal faulting.
