Erosion sources determined by inversion of major and trace element ratios and strontium isotopic ratios in river water: The Congo Basin case

Négrel, Philippe; Allègre, Claude J.; Dupré, Bernard; Lewin, É.

doi:10.1016/0012-821x(93)90023-3

Cited by 440 publications

(273 citation statements)

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“…The model uses Na-normalized elemental ratios (Cl:Na, Ca:Na, and Mg:Na) to partition the dissolved load between silicate, carbonate, evaporite, and precipitation sources (e.g., ref. 40 and details in SI Appendix). We apply our model to all samples from the world's large river database (28) and a subset of samples from the glacial (n = 84) database due to the data requirements.…”

Section: Resultsmentioning

confidence: 99%

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Torres

Moosdorf

Hartmann

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

159

171

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Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO 2 , we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO 2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean-atmosphere CO 2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO 2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O 2 . Future work on glaciation-weathering-carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.weathering | carbon cycle | glaciation | oxidation | sulfide E pisodes of glaciation represent some of the most dramatic changes in the history of Earth's climate. Basic questions remain unanswered about why the planet has occasionally but not always supported glaciers, about why some glaciations have been more intense than others, and about how glaciers have shaped Earth's landscapes, chemical cycles, and climate. Before the Phanerozoic (i.e., before ∼540 Mya), several glaciations are thought to have approached complete or near-complete planetary ice cover ("Snowball Earth" events; ref. 1). In contrast, more recent glaciations, including the Quaternary glaciations of the last million years, have been characterized by oscillating climate with ice extent limited to high latitudes even during glacial maxima (2). The formation of ice cover has long been known to fundamentally alter Earth's environment, changing albedo (3), influencing atmospheric and ocean circulation (4), and reshaping landscapes (5). These diverse effects may contribute to planetary-scale feedbacks that influence the transition to and the evolution of glaciation.Chemical weathering influences the composition of the atmosphere by releasing ionic species from minerals that alter the alkalinity and redox condition of the ocean-atmosphere system. Weathering of silicate minerals produces alkalinity, removing carbon from the at...

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Section: Resultsmentioning

confidence: 99%

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Torres

Moosdorf

Hartmann

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

159

171

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“…The radiogenic neodymium and strontium isotopes are generally considered to be reliable indicators of the provenance of sediments because the geological bodies have different Nd-Sr isotopic compositions that depend on their origins and ages [24][25][26][27]. Geologically, the CR Basin consists of variable strata from the Archean to the Quaternary period.…”

Section: Causes Of Seasonal Variations In Riverine Isotopic Compositionsmentioning

confidence: 99%

“…As a result, the Nd-Sr isotopic signatures of the sediments have been useful for identifying their sources and studying erosion processes [2, [26][27][28][29][30]. In addition, the Nd-Sr isotopic signatures of geological time scale sediments have been widely used to probe evolution of the Asian monsoon and the uplift history of Tibetan Plateau [31][32][33][34][35][36][37][38][39].…”

mentioning

confidence: 99%

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

et al. 2011

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“…Quantification of the rainwater input requires knowledge of the chemical composition of the rain over the studied drainage basin (Likens et al, 1977;Meybeck, 1983;Négrel et al, 1993). Here, the mean chemical composition of the rainfall at Tours over 1.5 years (Grosbois et al, 2000) was used, weighted by the quantity of each rain event.…”

Section: Correction For Atmospheric Inputmentioning

confidence: 99%

“…The correction for atmospheric contribution for any element Z in the river water can therefore be estimated by multiplying the river's Cl concentration (Cl ref Z/Cl ratio of rainwater (Meybeck, 1983;Négrel et al, 1993). Note that chloride in the atmosphere originates from sea salts and from a wide range of human activities and that the release of Cl from rocks has only been identified in the case of evaporite weathering (Meybeck, 1979).…”

Section: Correction For Atmospheric Inputmentioning

confidence: 99%

Variability of⁸⁷Sr/⁸⁶Sr in water draining granite revealed after a double correction for atmospheric and anthropogenic inputs

Petelet‐Giraud

Négrel

Casanova

2003

Hydrological Sciences Journal

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In a geochemical characterization of surface waters draining granites of the Vienne district, France, isotopic signatures strictly linked to water-rock interactions were determined by applying a double correction for atmospheric and anthropogenic inputs; the former based on the conservative behaviour of Cl and the latter based on the Sr concentrations and isotopic signatures, which are the only variables with clearly identifiable characteristics. The double-correction concept was validated by comparing the results with the theoretical Sr isotopic signature of water in equilibrium with the parent rock. The weathering model is based on the preferential dissolution of the three main Sr-bearing mineral phases: plagioclase, potassium feldspar and biotite. The Sr isotopic signatures of the waters are in good agreement with the calculated ones. The relative scattering observed for waters draining the same plutonic intrusion can be explained by water-rock interactions within different layers of the weathering profile. Résumé Cette étude présente la caractérisation géochimique d'eaux de surface drainant des granitoïdes, dans la région de Vienne, en France. L'identification de la signature isotopique des eaux uniquement liée à l'interaction eau roche a été appréhendée par une double correction des apports atmosphériques et anthropiques. La correction atmosphérique est basée sur le comportement conservatif du Cl. La correction anthropique n'a été réalisée que sur les signatures isotopiques et les teneurs en Sr, qui sont les seules variables dont les caractéristiques sont clairement identifiables. Ce concept de double correction a été validé par comparaison avec la signature isotopique en Sr théorique d'une eau en équilibre avec une roche mère. Le modèle d'altération utilisé s'appuie sur la dissolution des trois principaux minéraux contenant du Sr (plagioclase, feldspath-K et biotite). Les signatures isotopiques en Sr des eaux sont similaires à celles issues du calcul. La relative dispersion des signatures au sein d'un même batholite peut s'expliquer par des interactions eau-roche dans différents niveaux du profil d'altération. Key words

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Erosion sources determined by inversion of major and trace element ratios and strontium isotopic ratios in river water: The Congo Basin case

Cited by 440 publications

References 24 publications

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

Variability of⁸⁷Sr/⁸⁶Sr in water draining granite revealed after a double correction for atmospheric and anthropogenic inputs

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Erosion sources determined by inversion of major and trace element ratios and strontium isotopic ratios in river water: The Congo Basin case

Cited by 440 publications

References 24 publications

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Seasonal variations in the Sr-Nd isotopic compositions of suspended particulate matter in the lower Changjiang River: Provenance and erosion constraints

Variability of87Sr/86Sr in water draining granite revealed after a double correction for atmospheric and anthropogenic inputs

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Variability of⁸⁷Sr/⁸⁶Sr in water draining granite revealed after a double correction for atmospheric and anthropogenic inputs