Silicate weathering in the Ganges alluvial plain
(2015) In Earth and Planetary Science Letters 427. p.136-148- Abstract
- The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimiting the Ganges alluvial plain. Despite constituting approximately 80% of the basin, weathering processes in the peninsula and alluvial plain have received little attention. Here we present an analysis of 51 water samples along a transect of the alluvial plain, including all major tributaries. We focus on the geochemistry of silicon and its isotopes. Area normalised dissolved Si yields are... (More)
- The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimiting the Ganges alluvial plain. Despite constituting approximately 80% of the basin, weathering processes in the peninsula and alluvial plain have received little attention. Here we present an analysis of 51 water samples along a transect of the alluvial plain, including all major tributaries. We focus on the geochemistry of silicon and its isotopes. Area normalised dissolved Si yields are approximately twice as high in rivers of Himalaya origin than the plain and peninsular tributaries (82, 51 and 32 kmol SiO2 km(-2) yr(-1), respectively). Such dissolved Si fluxes are not widely used as weathering rate indicators because a large but variable fraction of the DSi mobilised during the initial weathering process is retained in secondary clay minerals. However, the silicon isotopic composition of dissolved Si (expressed as delta Si-30) varies from +0.8 parts per thousand in the Ganges mainstem at the Himalaya front to +3.0 parts per thousand in alluvial plain streams and appears to be controlled by weathering congruency, i.e. by the degree of incorporation of Si into secondary phases. The higher delta Si-30 values therefore reflect decreasing weathering congruency in the lowland river catchments. This is exploited to quantify the degree of removal using a Rayleigh isotope mass balance model, and consequently derive initial silica mobilisation rates of 200, 150 and 107 kmol SiO2 km(-2) yr(-1), for the Himalaya, peninsular India and the alluvial plain, respectively. Because the non-Himalayan regions dominate the catchment area, the majority of initial silica mobilisation from primary minerals occurs in the alluvial plain and peninsular catchment (41% and 34%, respectively). (C) 2015 The Authors. Published by Elsevier B.V. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/7972529
- author
- Frings, Patrick LU ; Clymans, Wim LU ; Fontorbe, Guillaume LU ; Gray, William ; Chakrapani, Govind J. ; Conley, Daniel LU and De La Rocha, Christina
- organization
- publishing date
- 2015
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- weathering, lowland, Ganges, dissolved silica, silicate weathering, silicon isotopes
- in
- Earth and Planetary Science Letters
- volume
- 427
- pages
- 136 - 148
- publisher
- Elsevier
- external identifiers
-
- wos:000359330800015
- scopus:84937239505
- ISSN
- 1385-013X
- DOI
- 10.1016/j.epsl.2015.06.049
- language
- English
- LU publication?
- yes
- id
- 2188a50c-a5c3-4d37-bd48-99c99e782637 (old id 7972529)
- date added to LUP
- 2016-04-01 10:52:45
- date last changed
- 2022-04-28 02:18:56
@article{2188a50c-a5c3-4d37-bd48-99c99e782637,
abstract = {{The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimiting the Ganges alluvial plain. Despite constituting approximately 80% of the basin, weathering processes in the peninsula and alluvial plain have received little attention. Here we present an analysis of 51 water samples along a transect of the alluvial plain, including all major tributaries. We focus on the geochemistry of silicon and its isotopes. Area normalised dissolved Si yields are approximately twice as high in rivers of Himalaya origin than the plain and peninsular tributaries (82, 51 and 32 kmol SiO2 km(-2) yr(-1), respectively). Such dissolved Si fluxes are not widely used as weathering rate indicators because a large but variable fraction of the DSi mobilised during the initial weathering process is retained in secondary clay minerals. However, the silicon isotopic composition of dissolved Si (expressed as delta Si-30) varies from +0.8 parts per thousand in the Ganges mainstem at the Himalaya front to +3.0 parts per thousand in alluvial plain streams and appears to be controlled by weathering congruency, i.e. by the degree of incorporation of Si into secondary phases. The higher delta Si-30 values therefore reflect decreasing weathering congruency in the lowland river catchments. This is exploited to quantify the degree of removal using a Rayleigh isotope mass balance model, and consequently derive initial silica mobilisation rates of 200, 150 and 107 kmol SiO2 km(-2) yr(-1), for the Himalaya, peninsular India and the alluvial plain, respectively. Because the non-Himalayan regions dominate the catchment area, the majority of initial silica mobilisation from primary minerals occurs in the alluvial plain and peninsular catchment (41% and 34%, respectively). (C) 2015 The Authors. Published by Elsevier B.V.}},
author = {{Frings, Patrick and Clymans, Wim and Fontorbe, Guillaume and Gray, William and Chakrapani, Govind J. and Conley, Daniel and De La Rocha, Christina}},
issn = {{1385-013X}},
keywords = {{weathering; lowland; Ganges; dissolved silica; silicate weathering; silicon isotopes}},
language = {{eng}},
pages = {{136--148}},
publisher = {{Elsevier}},
series = {{Earth and Planetary Science Letters}},
title = {{Silicate weathering in the Ganges alluvial plain}},
url = {{http://dx.doi.org/10.1016/j.epsl.2015.06.049}},
doi = {{10.1016/j.epsl.2015.06.049}},
volume = {{427}},
year = {{2015}},
}