Schopka,H.H., Derry,L.A. and Arcilla,C.A.(2011): Chemical weathering, river geochemistry and atmospheric carbon fluxes from volcanic and ultramafic regions on Luzon Island, the Philippines. Geochimica et Cosmochimica Acta, 75, 978-1002.

『フィリピンのルソン島における火山岩および超塩基性岩地域からの化学風化と河川水の地球化学的性質と大気炭素フラックス』

『Abstract
　We investigated rates of chemical weathering of volcanic and ophiolitic rocks on Luzon Island, the Philippines. Luzon has a tropical climate and is volcanically and tectonically very active, all factors that should enhance chemical weathering. Seventy-five rivers and streams (10 draining ophiolites, 65 draining volcanic bedrock) and two volcanic hot springs were sampled and analyzed for major elements, alkalinity and 87Sr/86Sr. Cationic fluxes from the volcanic basins are dominated by Ca2+ and Mg2+ and dissolved silica concentrations are high (500-1900μM). Silica concentrations in streams draining ophiolites are lower (400-900μM), and the cationic charge is mostly Mg2+. The areally weighted average CO2 export flux from our study area is 3.89±0.21×106 mol/km2/yr, or 5.99±0.64×106 mol/km2/yr from ophiolites and 3.58±0.23×106 mol/km2/yr from volcanic areas (uncertainty given as ±1 standard error, s.e.). This is 〜6-10 times higher than the current best estimate of areally averaged global CO2 export by basalt chemical weathering and 〜2-3 times higher than the current best estimate of CO2 export by basalt chemical weathering in the tropics. Extrapolating our findings to all tropical areas, we estimate that around one tenth of all atmospheric carbon exported via silicate weathering to the oceans annually is processed in these environments, which amount to 〜1％ of the global exorheic drainage area. Chemical weathering of volcanic terranes in the tropics appears to make a disproportionately large impact on the long-term carbon cycle. 』

1. Introduction
2. Geology and climate
　2.1. Zambales and Angat ophiolites
　2.2. Luzon Volcanic Arc
　2.3. Southern Sierra Madre
　2.4. Bicol Volcanic Arc
　2.5. Climate
3. Methods
　3.1. Fieldwork
　3.2. Laboratory analyses
　3.3. Hydrology
　3.4. Uncertainty propagation in flux calculations
4. Results and discussion
　4.1. Major elements
　4.2. Sr isotopes
　4.3. Sources of solutes
　　4.3.1. Regional trends in sources of solutes - atmospheric inputs　　
　　4.3.2. Regional trends in sources of solutes - high-temperature weathering
　　4.3.3. Regional trends in sources of solutes - low-temperature weathering
　4.4. Element fluxes
5. Implications for global CO2 export
6. Conclusions
Acknowledgments
Appendix 1. Sensitivity analysis for solute source allocations
Appendix A. Supplementary data
References

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