『Abstract
　A 2 m-thick spheroidal weathering profile, developed on a quartz diorite in the Rio Icacos watershed (Luquillo Mountains, eastern Puerto Rico), was analyzed for major and trace element concentrations, Sr and Nd isotopic ratios and U-series nuclides (²³⁸U-²³⁴U-²³⁰Th-²²⁶Ra). In this profile a 40 cm thick soil horizon is overlying a 150 cm thick saprolite which is separated from the basal corestone by a 〜40 cm thick rindlet zone. The Sr and Nd isotopic variations along the whole profile imply that, in addition to geochemical fractionations associated to water-rock interactions, the geochemical budget of the profile is influenced by a significant accretion of atmospheric dusts. The mineralogical and geochemical variations along the profile also confirm that the weathering front does not progress continuously from the top to the base of the profile. The upper part of the profile is probably associated with a different weathering system (lateral weathering of upper corestones) than the lower part, which consists of the basal corestone, the associated rindlet system and the saprolite in contact with these rindlets. Consequently, the determination of weathering rates from ²³⁸U-²³⁴U-²³⁰Th-²²⁶Ra disequilibrium in a series of samples collected along a vertical depth profile can only be attempted for samples collected in the lower part of the profile, i.e. the rindlet zone and the lower saprolite. Similar propagation rates were derived for the rindlet system and the saprolite by using classical models involving loss and gain processes for all nuclides to interpret the variation of U-series nuclides in the rindlet-saprolite subsystem. The consistency of these weathering rates with average weathering and erosion rates derived via other methods for the whole watershed provides a new and independent argument that, in the Rio Icacos watershed, the weathering system has reached a geomorphological steady-state. Our study also indicates that even in environments with differential weathering, such as observed for the Puerto Rico site, the radioactive disequilibrium between the nuclides of a single radioactive series (here ²³⁸U-²³⁴U-²³⁰Th-²²⁶Ra) can still be interpreted in terms of a simplified scenario of congruent weathering. Incidentally, the U-Th-Ra disequilibrium in the corestone samples confirms that the outermost part of the corestone is already weathered.』

1. Introduction
2. Study area and sample collection
3. U-series methodology and analytical methods
　3.1. U-series modeling
　3.2. Analytical techniques
4. Results and first interpretations
　4.1. Mineralogical and petrological observations through the outcrop profile
　4.2. The evolution of the chemical composition in the different lithological units
　4.3. The evolution of the Sr and Nd isotopic compositions in the different lithological units
　4.4. The U-Th-Ra disequilibria
　　4.4.1. Corestone
　　4.4.2. Rindlets and saprolite
5. Discussion
　5.1. Variations of the major and trace element concentrations in bedrock and rindlets
　5.2. Variations of the major and trace element concentrations in the saprolite
　5.3. Variations of Sr and Nd isotopes ratios in saprolite
　5.4. Variations of U-series nuclides and determination of weathering rates
　　5.4.1. Determination of production rate in the lower saprolite
　　5.4.2. Determination of production rate in the 2003-2004 rindlets
　5.5. Geomorphological and geochemical implications
　　5.5.1. Implications for the regolith formation
　　5.5.2. Implications for the application of U-series methodology
6. Conclusions
Acknowledgments
Appendix A1. Solving the system of eqs. (A1)-(A5)
Appendix A2. Analytical solutions of the ordinary differential equations eqs. (A1)-(A5)
Appendix B. Supplementary data
References