Stream geochemistry, chemical weathering and CO(2) consumption potential of andesitic terrains, Dominica, Lesser Antilles

• Published in: Geochimica et cosmochimica acta Vol. 74; no. 1; pp. 85 - 103
• Main Authors: Goldsmith, Steven T, Carey, Anne E, Johnson, Brent M, Welch, Susan A, Lyons, W Berry, McDowell, William H, Pigott, Jeffrey S
• Format: Journal Article
• Language: English
• Published: 01-01-2010
• ISSN: 0016-7037
• DOI: 10.1016/j.gca.2009.10.009

Recent studies of chemical weathering of andesitic-dacitic material on high-standing islands (HSIs) have shown these terrains have some of the highest observed rates of chemical weathering and associated CO(2) consumption yet reported. However, the paucity of stream gauge data in many of these terrains has limited determination of chemical weathering product fluxes. In July 2006 and March 2008, stream water samples were collected and manual stream gauging was performed in watersheds throughout the volcanic island of Dominica in the Lesser Antilles. Distinct wet and dry season solute concentrations reveal the importance of seasonal variations on the weathering signal. A cluster analysis of the stream geochemical data shows the importance of parent material age on the overall delivery of solutes. Observed Ca:Na, HCO(3):Na and Mg:Na ratios suggest crystallinity of the parent material may also play an important role in determining weathering fluxes. From total dissolved solids concentrations and mean annual discharge calculations we calculate chemical weathering yields of (6-106 t km(-2) a(-1)), which are similar to those previously determined for basalt terrains. Silicate fluxes (3.1-55.4 t km(-2) a(-1)) and associated CO(2) consumption (190-1575 x 10(3) mol km(-2) a(-1)) determined from our study are among the highest determined to date. The calculated chemical fluxes from our study confirm the weathering potential of andesitic-dacitic terrains and that additional studies of these terrains are warranted.