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DOI	10.1016/j.gca.2020.10.021
	Lithium isotope signatures of weathering in the hyper-arid climate of the western Tibetan Plateau
	Weynell M.; Wiechert U.; Schuessler J.A.
发表日期	2021
ISSN	167037
起始页码	205
结束页码	223
卷号	293
英文摘要	This study of Lithium (Li) isotopes in surface waters and sediments in the catchment of Lake Bangong and the Upper Indus on the western Tibetan Plateau aims to identify processes that control Li isotope variations during weathering under a cold and hyper-arid climate. Additionally, Li isotope ratios in the Yarlung Tsangpo – Brahmaputra River were investigated. The lake and river sediments of Lake Bangong catchment display remarkable low δ7Li values between −4.7‰ and −0.6‰ relative to L-SVEC. Li isotopes in river bed sediments correlate with weathering intensity tracers such as the chemical index of alteration (CIA), K/(Na + K), or Na/Ti, and δ7Li values decrease continuously within the sediment cascade. These observations cannot be explained by mixing of different lithologies but reflects increasing intensity of weathering. The hyper-arid climate on the western plateau results in considerably long sediment residence times, which allows for overcoming the limitation of water availability on chemical weathering reactions. Samples from the Lake Bangong basins display low δ7Li values between +8.1‰ and +11.1‰. The major inflows have dissolved δ7Li values of +6.1‰ and +8.9‰. High Li/Na ratios in the stream waters indicate some contribution of hydrothermal Li. However, low δ7Li values in surface waters result from impeded silicate weathering processes in the thin soils. The samples from Indus headwaters and Yarlung Tsangpo provide evidence for low δ7Li all over the western and southern Tibetan Plateau. Using data of the Bangong Co, the Indus headwaters, and Yarlung Tsangpo, as well as published data from the northeastern plateau, we explore what controls Li isotope variation across the Tibetan plateau. Mass balance calculations suggest that similar proportions of dissolved Li and particulate Li are exported by river water and sediments on the western plateau. In contrast, high δ7Li values around +17‰ of the dissolved load in rivers on the northeastern Tibetan Plateau reflect a particulate Li export flux that is about five times higher than the export flux of dissolved Li. There is no first-order control by silicate weathering rates. The δ7Li differences largely follow the precipitation gradient across the Tibetan Plateau, which results in high net-incorporation of Li into clays on the northeastern but limits soil formation on the western Tibetan Plateau and, therefore limited, processing of lithium in the weathering zone. © 2020 Elsevier Ltd
英文关键词	Cold desert; Lithium isotopes; Tibetan Plateau; Weathering regime
语种	英语
scopus关键词	Geochimica et Cosmochimica Acta
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/158314
作者单位	Institute of Geological Sciences; Freie Universität Berlin; Malteser Straße 74-100; Berlin; Germany; GFZ German Research Centre for Geosciences; Earth Surface Geochemistry; Telegrafenberg; Potsdam; Germany; State Key Laboratory of Marine Geology; School of Ocean and Earth Science; Tongji University; Shanghai; China
推荐引用方式 GB/T 7714	Weynell M.,Wiechert U.,Schuessler J.A.. Lithium isotope signatures of weathering in the hyper-arid climate of the western Tibetan Plateau[J],2021,293.
APA	Weynell M.,Wiechert U.,&Schuessler J.A..(2021).Lithium isotope signatures of weathering in the hyper-arid climate of the western Tibetan Plateau.,293.
MLA	Weynell M.,et al."Lithium isotope signatures of weathering in the hyper-arid climate of the western Tibetan Plateau".293(2021).