The silicon isotopic composition of the Ganges and its tributaries. Fontorbe, G., De La Rocha, C. L., Chapman, H. J., & Bickle, M. J. Earth And Planetary Science Letters, 381:21--30, November, 2013.
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The silicon isotopic composition (delta Si-30) of the headwaters of the Ganges River, in the Himalaya, ranged from +0.49 +/- 0.01 parts per thousand to +2.17 +/- 0.04 parts per thousand at dissolved silicon (DSi) concentrations of 38 to 239 mu M. Both the concentration and isotopic composition of DSi in the tributaries increased between the highest elevations to where the Ganges leaves the Himalayas at Rishikesh. The tributaries exhibit a linear correlation between delta Si-30 and DSi that may represent mixing between a low DSi, low delta Si-30 (e.g., 40 mu M, +0.5 parts per thousand) component potentially reflecting fractionation during adsorption of a small fraction of silicon onto iron oxides and a high DSi, high delta Si-30 component (e.g., 240 mu M, +1.7 parts per thousand) produced during higher intensity weathering with a greater proportional sequestration of weathered silicon into secondary minerals or biogenic silica. On the Ganges alluvial plain, in the Ganges and the Yamuna, Gomati, and their tributaries, DSi ranged from 122 to 218 mu M while delta Si-30 ranged from +1.03 +/- 0.03 parts per thousand to +2.46 +/- 0.06 parts per thousand. Highest values of delta Si-30 occurred in the Gomati and its tributaries. In general, the lower DSi and higher delta Si-30 of DSi in these rivers suggests control of both by removal of DSi by secondary mineral formation and/or biogenic silica production. A simple 1-dimensional model with flow through a porous medium is introduced and provides a useful framework for understanding these results. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
@article{fontorbe_silicon_2013,
	title = {The silicon isotopic composition of the {Ganges} and its tributaries},
	volume = {381},
	issn = {0012-821X},
	doi = {10.1016/j.epsl.2013.08.026},
	abstract = {The silicon isotopic composition (delta Si-30) of the headwaters of the Ganges River, in the Himalaya, ranged from +0.49 +/- 0.01 parts per thousand to +2.17 +/- 0.04 parts per thousand at dissolved silicon (DSi) concentrations of 38 to 239 mu M. Both the concentration and isotopic composition of DSi in the tributaries increased between the highest elevations to where the Ganges leaves the Himalayas at Rishikesh. The tributaries exhibit a linear correlation between delta Si-30 and DSi that may represent mixing between a low DSi, low delta Si-30 (e.g., 40 mu M, +0.5 parts per thousand) component potentially reflecting fractionation during adsorption of a small fraction of silicon onto iron oxides and a high DSi, high delta Si-30 component (e.g., 240 mu M, +1.7 parts per thousand) produced during higher intensity weathering with a greater proportional sequestration of weathered silicon into secondary minerals or biogenic silica. On the Ganges alluvial plain, in the Ganges and the Yamuna, Gomati, and their tributaries, DSi ranged from 122 to 218 mu M while delta Si-30 ranged from +1.03 +/- 0.03 parts per thousand to +2.46 +/- 0.06 parts per thousand. Highest values of delta Si-30 occurred in the Gomati and its tributaries. In general, the lower DSi and higher delta Si-30 of DSi in these rivers suggests control of both by removal of DSi by secondary mineral formation and/or biogenic silica production. A simple 1-dimensional model with flow through a porous medium is introduced and provides a useful framework for understanding these results. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.},
	language = {English},
	journal = {Earth And Planetary Science Letters},
	author = {Fontorbe, Guillaume and De La Rocha, Christina L. and Chapman, Hazel J. and Bickle, Michael J.},
	month = nov,
	year = {2013},
	keywords = {ACL, E3, Ganges, Himalayas, WOS, chemical weathering, river chemistry, silicon isotopes},
	pages = {21--30}
}
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