DOI: 10.1016/j.epsl.2019.115871
论文题名: Weathering dynamics of Large Igneous Provinces (LIPs): A case study from the Lesotho Highlands
作者: Chen Y. ; Hedding D.W. ; Li X. ; Greyling A.C. ; Li G.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2020
卷: 530 语种: 英语
中文关键词: critical zone
; landscape evolution
; regolith
; soil
; water-rock reaction
英文关键词: Basalt
; Erosion
; Floods
; Geochemistry
; Reservoirs (water)
; Silicates
; Soils
; Temperature distribution
; Critical zones
; Landscape evolutions
; Large Igneous Provinces (LIPs)
; Lesotho Highlands Water Project
; regolith
; Temperature dependence
; Terrestrial cosmogenic nuclides
; Water-rock reactions
; Weathering
; chemical weathering
; erosion rate
; flood basalt
; igneous geochemistry
; landscape evolution
; large igneous province
; radiocarbon dating
; regolith
; water-rock interaction
; Karoo
; Lesotho
; South Africa
英文摘要: Basaltic terrains contribute a significant component to the global silicate weathering flux despite their limited areal coverage. A strong correlation between chemical weathering flux and climatic factors such as temperature in volcanically inactive basaltic fields implies that weathering of basalt might have played an important role in maintaining the habitability of the Earth and the balance of the geological carbon cycle. However, the low erosion rate of flood basalt provinces on tectonically quiescent cratons, where the clear climate dependence of weathering rate has been observed, implies a ‘supply-limited’ weathering regime so that weathering fluxes are expected to be controlled by physical erosion rather than climate. This work tests the weathering dynamics of flood basalts by investigating the weathering flux of the Karoo LIP on the Lesotho Highlands where an extremely low rate of denudation has been recorded through terrestrial cosmogenic nuclide dating and sediment flux. Stream chemistry of the rivers from the Lesotho Highlands shows typical characteristics of basalt weathering with Ca and Mg as the dominant cations and HCO3 − as the dominant anion. Strong spatial and seasonal variability of solute concentration, possibly linked to a dilution effect, is observed. However, the giant Katse Reservoir of the Lesotho Highlands Water Project (LHWP) effectively averages the spatial and seasonal variability of the solute concentration. The average solution concentration and long-term runoff of the Katse Reservoir give an average atmospheric CO2 consumption rate of 0.26 ± 0.02 × 106 mol/km2/yr (mean ± standard deviation). The chemical weathering flux requires complete alteration of primary silicates and, therefore, a ‘supply-limited’ weathering regime is suggested given the low denudation rate. Nevertheless, the chemical weathering rate of the Lesotho Highlands, as well as other low-eroding basaltic plateaus, is still consistent with the global correlation between temperature and the rate of basalt weathering. A production-limited denudation rate, modulated by temperature, is suggested to reconcile the paradox between the observed temperature dependence of chemical weathering rates and ‘supply-limited’ weathering regimes. © 2019 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/164919
Appears in Collections: 气候变化与战略
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作者单位: MOE Key Laboratory of Surficial Geochemistry, Department of Earth and Planetary Sciences, Nanjing University, Nanjing, 210023, China; Department of Geography, University of South Africa, Pioneer Avenue, Florida, 1710, South Africa; SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China
Recommended Citation:
Chen Y.,Hedding D.W.,Li X.,et al. Weathering dynamics of Large Igneous Provinces (LIPs): A case study from the Lesotho Highlands[J]. Earth and Planetary Science Letters,2020-01-01,530