『Abstract
In order to evaluate the importance of hydrologic processes in
controlling chemical weathering rates, a reactive transport analysis
is used to interpret chemical weathering rate data for a range
of systems. An analysis of weathering rates for granitic material
shows that weathering rates depend most strongly on fluid residence
times and fluid flow rates, and depend very weakly on material
age. Over moderate fluid residence times from 5 days to 10 yr,
characteristic of soils and some aquifers, transport-controlled
weathering explains the orders of magnitude variation in weathering
rates to a better extent than material age. For fluid residence
times greater than 10 yr, characteristic of some aquifers, saprolites,
and most marine sediments, a purely thermodynamic-control on chemical
weathering rates sustains chemical weathering - this control may
be due to clay precipitation, which can drive weathering of primary
minerals, or microbial processes which alter the fluid chemistry
via the oxidation of organic matter. In addition, this analysis
suggests that the apparent time dependence of chemical weathering
rates commonly used to model the evolution of Earth's landforms
may be attributable to transport-controlled weathering and the
evolution of hydrologic properties over time. If hydrologic processes
are the primary control on chemical weathering rates, the nature
of the temperature dependence of chemical weathering rates is
also altered.
Keywords: weathering; dissolution kinetics; transport-limited;
erosion; climate change; feedback』
1. Introduction
1.1. Transport-controlled weathering
2. Materials and methods
2.1. Weathering rates, length scales and fluid residence
times in non-eroding environments
2.2. Reactive transport approach for equilibration length scales
and 1-D erosion
3. Results and discussion
3.1. Interpretive model for transport-limited weathering
3.2. Evidence for transport-control of natural systems
3.3. Weathering in extreme environments
3.4. Implications for the temperature dependence of chemical
weathering rates
3.5. Implications for the time dependence of chemical weathering
rates
3.6. Implications of transport-controlled weathering in active
tectonic environments
4. Conclusion
Acknowledgments
References