Could peridotite hydration reactions have provided a contributory driving force for Cenozoic uplift and accelerated subsidence along the margins of the North Atlantic and Labrador Sea?

摘要

This study evaluates the hypothesis that peridotite hydration reactions (e.g. serpentinisation) at the landward termination of transform fracture zones provide a contributory driving force for coupled uplift and accelerated subsidence along the margins of the North Atlantic and Labrador Sea in the Cenozoic. This evaluation is partly based on the extent and rate of serpentinisation, calculated by Skelton et aL. (2005) by using seismic velocity as a proxy for progress of the serpentinisation reactions. The hypothesis is supported by 1) spatial coincidence between most of the uplifted segments of the margin with the landward termination of transform fracture zones, 2) the theoretical capacity of serpentinisation to generate 102-103 m of uplift at a rate of mm.a' to cm.a'1 which is consistent with observations from the margin, and 3) the potential for landward material flow of a hydrated peridotite inclusion, providing a mechanism for sustaining uplift and its pairing with accelerated subsidence. Also, serpentinisation is more effective than other metamorphic reactions (e.g. granulite to amphibolite, eclogite to amphibolite) as a driving force for uplift. Shortfalls of this model are that 1) extensive peridotite hydration is unlikely at depths exceeding 10-20km and 2) the timing of uplift requires that pulses of extensive peridotite hydration occurred along inactive segments of transform fracture zones. We conclude mat the volume expansion caused by peridotite hydralion was probably insufficient to account for widespread uplift during the Cenozoic. However, we suggest that the following processes could occur at or near the landward terminations of transform fracture zones: 1) volume expansion caused by extensive peridotite hydration beneath thinned crust at or near the ocean-continent transition and 2) mechanical weakening caused by limited peridotite hydration beneath thicker continental crust. These processes may have important implications for models aimed at explaining Cenozoic uplift and accelerated subsidence.