『Abstract
　⁴⁰Ar/³⁹Ar incremental heating ages for twenty one grains of cryptomelane, collected at 0, 42, 45, and 60 m depths in the Cachoeira Mine weathering profile, Minas Gerais, permit calculating long-term (10 Ma time scale) weathering rate (saprolitization rate) in SE Brazil. Pure well-crystallized cryptomelane grains with high K contents (3-5 wt.％) yield reliable geochronological results. The ⁴⁰Ar/³⁹Ar plateau ages obtained decrease from the top to the bottom of the profile (12.7±0.1 to 7.6±0.1 Ma at surface; 7.6±0.2 to 6.1±0.2 Ma at 42 m; and 7.1±0.2 to 5.9±0.1 Ma at 45 m; 6.6±0.1 to 5.2±0.1 Ma at 60 m), yielding a weathering front propagation rate of 8.9±1.1 m/m.y. From the geochronological results and the mineral transformations implicit by the current mineralogy in the weathering profiles, it is possible to calculate the saprolitization rate for the Cachoeira Mine lithologies and for adjacent weathering profiles developed on granodiorites and schists. The measured weathering front propagation rate yields a saprolitization rate of 24.9±3.1 t/km²/yr. This average long-term (＞10 Ma) saprolitization rate is consistent with mass balance calculations results for present saprolitization rates in weathering watersheds. These results are also consistent with long-term saprolitization rates estimated by combining cosmogenic isotope denudation rates with mass balance calculations.

Keywords: Weathering rate; chemical denudation; ⁴⁰Ar/³⁹Ar geochronology; Miocene; SE Brazil』

1. Introduction
2. Regional and local geology
3. Sampling and analytical procedures
4. Results
5. Discussion
　5.1. Estimating regional weathering rates from weathering geochronology
　5.2. Comparison with weathering rates obtained by other methods
　5.3. Factors controlling weathering rates
6. Conclusions
Acknowledgements
Appendix A. Supplementary data
References