Is orogenesis a net sink or source of atmospheric CO_2?

摘要

In global carbon cycle models, orogenesis is often viewed as a sink for atmospheric CO_2, acting on tectonic timescales. However, recent attempts to quantify fluxes for CO_2 produced by metamorphic reactions and released to the atmosphere suggest that these are an order-of-magnitude greater than CO_2 uptake by chemical weathering of silicate minerals, and that metamorphic CO_2 is released on millennial timescales. These hypotheses have gained support from both measurements of CO_2 emissions from present-day orogenic hot springs and chromatographic modelling of carbonation reactions in metamorphic rocks from ancient orogens. In this article I review research that attempts to quantify metamorphic CO_2 release fluxes, focussing specifically on studies conducted in the SW Scottish Highlands.