期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 450, 期 -, 页码 381-391出版社
ELSEVIER
DOI: 10.1016/j.epsl.2016.06.012
关键词
chemical weathering; Andes; Amazon; Pyrite; oxidation
资金
- NSF [EAR-1227192, EAR-1455352]
- USC fellowship
- C-DEBI fellowship
- NSERC scholarship
- Clarendon Fund Ph.D. scholarship
- Directorate For Geosciences
- Division Of Earth Sciences [1455352] Funding Source: National Science Foundation
The correlation between chemical weathering fluxes and denudation rates suggests that tectonic activity can force variations in atmospheric pCO(2) by modulating weathering fluxes. However, the effect of weathering on pCO(2) is not solely determined by the total mass flux. Instead, the effect of weathering on pCO(2) also depends upon the balance between 1) alkalinity generation by carbonate and silicate mineral dissolution and 2) sulfuric acid generation by the oxidation of sulfide minerals. In this study, we explore how the balance between acid and alkalinity generation varies with tectonic uplift to better understand the links between tectonics and the long-term carbon cycle. To trace weathering reactions across the transition from the Peruvian Andes to the Amazonian foreland basin, we measured a suite of elemental concentrations (Na, K, Ca, Mg, Sr, Si, Li, SO4, and Cl) and isotopic ratios (Sr-87/Sr-86 and delta S-34) on both dissolved and solid phase samples. Using an inverse model, we quantitatively link systematic changes in solute geochemistry with elevation to downstream declines in sulfuric acid weathering as well as the proportion of cations sourced from silicates. With a new carbonate-system framework, we show that weathering in the Andes Mountains is a CO2 source whereas foreland weathering is a CO2 sink. These results are consistent with the theoretical expectation that the ratio of sulfide oxidation to silicate weathering increases with increasing erosion. Altogether, our results suggest that the effect of tectonically-enhanced weathering on atmospheric pCO(2) is strongly modulated by sulfide mineral oxidation. (C) 2016 Elsevier B.V. All rights reserved.
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