Ge/Si and Sr/Sr tracers of weathering reactions and hydrologic pathways in a tropical granitoid system |
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Authors: | Louis A Derry Julie C Pett-Ridge Andrew C Kurtz Joseph W Troester |
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Institution: | aCornell University, Department of Earth and Atmospheric Sciences, Ithaca, NY 14853, USA;bBoston University, Department of Earth Sciences, Boston, MA 02215, USA;cUnited States Geological Survey, Caribbean Water Science Center, Guaynabo, PR 00965, USA |
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Abstract: | Ge/Si and 87Sr/86Sr data from primary and secondary minerals, soil waters, and stream waters in a tropical granitoid catchment quantitatively reflect mineral alteration reactions that occur at different levels within the bedrock–saprolite–soil zone. Near the bedrock–saprolite interface, plagioclase to kaolinite reaction yields low Ge/Si and 87Sr/86Sr. Higher in the regolith column, biotite weathering and kaolinite dissolution drive Ge/Si and 87Sr/86Sr to high values. Data from streams at base flow sample the bedrock–saprolite interface zone, while at high discharge solutes are derived from upper saprolite–soil zone. Coupled Ge/Si and 87Sr/86Sr can be effective tools for quantifying the importance of specific weathering reactions, and for geochemical hydrograph separation. |
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Keywords: | Germanium Silica Ge/Si Strontium isotopes Weathering reactions Hydrograph separation |
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