气候变化领域集成服务门户(CCPortal): Reconciling chemical weathering rates across scales: Application of uranium-series isotope systematics in volcanic weathering clasts from Basse-Terre Island (French Guadeloupe)

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DOI	10.1016/j.epsl.2019.115874
	Reconciling chemical weathering rates across scales: Application of uranium-series isotope systematics in volcanic weathering clasts from Basse-Terre Island (French Guadeloupe)
	Guo J.; Ma L.; Gaillardet J.; Sak P.B.; Pereyra Y.; Engel J.
发表日期	2020
ISSN	0012821X
卷号	530
英文摘要	To elucidate the factors that contribute to the orders of magnitude difference generally observed in apparent weathering rates across scales, we utilized a U-series isotopic technique to directly determine the duration and rates of chemical weathering recorded in weathering clasts. In this study, we systematically compiled 15 individual volcanic weathering clasts collected from eight andesitic watersheds along a gradient of mean annual precipitation ranging from ∼1600 mm to 6400 mm on the tropical volcanic Basse-Terre Island of French Guadeloupe. We measured U-series isotope compositions to quantify weathering advance rates along the core-rind transects in these weathering clasts. Total rind formation ages, the length of time it took for these weathering clasts to form from andesitic rock fragments or volcanic clasts in the soil zones, range from 60 kyr to 300 kyr. As expected for each individual core-rind weathering transect, the rind ages generally increase almost linearly with distance away from the core-rind boundary. The derived clast weathering rates range from 0.08 ± 0.04 to 0.34 ± 0.01 mm kyr−1, and the rates exhibit a strong positive correlation (R2=0.74) with the annual runoff values of these watersheds. This correlation documents the first direct evidence that weathering over geological timescales on the island is controlled by the amount of precipitation and corroborates the relationship that was previously reported for the riverine weathering fluxes at Basse-Terre Island in Guadeloupe, but measured with much shorter time scales. The clast-scale rates (inferred for the characteristic length scale of mm) are compared to the watershed-scale rates of Basse-Terre Island (length scale of km): constantly higher rates are observed at the watershed scales than the clast scale and the discrepancy equals ∼1800 ± 400 times, despite changes in watershed characteristics such as watershed size, relief, and runoff values. The discrepancy is attributed to the fractal nature of the roughness and surface area across scales. For example, the presence of undulations and fractures (e.g. roughness) at the bedrock-saprolite contact of the watershed, which is generally not assessed in the watershed surface area estimates, is most likely the main contributor to the constant rate difference of ∼1800 times. © 2019 Elsevier B.V.
关键词	French Guadeloupe river weathering fluxes U-series isotopes weathering clasts weathering rates
英文关键词	Erosion; Geochemistry; Isotopes; Runoff; Surface roughness; Uranium; Volcanoes; Watersheds; Geological timescales; Guadeloupe; Mean annual precipitation; Surface area estimates; U-series isotopes; Uranium-series isotopes; Watershed characteristics; Weathering rates; Weathering; andesite; chemical weathering; clast; correlation; river water; roughness; uranium isotope; weathering rate; Basse Terre; Guadeloupe; Leeward Islands [Lesser Antilles]
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202625
作者单位	Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968, United States; Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, F-75005, France; Department of Earth Sciences, Dickinson College, Carlisle, PA 17013, United States
推荐引用方式 GB/T 7714	Guo J.,Ma L.,Gaillardet J.,et al. Reconciling chemical weathering rates across scales: Application of uranium-series isotope systematics in volcanic weathering clasts from Basse-Terre Island (French Guadeloupe)[J],2020,530.
APA	Guo J.,Ma L.,Gaillardet J.,Sak P.B.,Pereyra Y.,&Engel J..(2020).Reconciling chemical weathering rates across scales: Application of uranium-series isotope systematics in volcanic weathering clasts from Basse-Terre Island (French Guadeloupe).Earth and Planetary Science Letters,530.
MLA	Guo J.,et al."Reconciling chemical weathering rates across scales: Application of uranium-series isotope systematics in volcanic weathering clasts from Basse-Terre Island (French Guadeloupe)".Earth and Planetary Science Letters 530(2020).