气候变化领域集成服务门户(CCPortal): Impact of fluid-rock interaction on water uptake of the Icelandic crust: Implications for the hydration of the oceanic crust and the subducted water flux

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DOI	10.1016/j.epsl.2020.116210
	Impact of fluid-rock interaction on water uptake of the Icelandic crust: Implications for the hydration of the oceanic crust and the subducted water flux
	Kleine B.I.; Stefánsson A.; Halldórsson S.A.; Barnes J.D.
发表日期	2020
ISSN	0012821X
卷号	538
英文摘要	Oceanic crust is a major transport medium of water into the mantle wedge and the convecting mantle. Yet, the water content of the oceanic crust remains uncertain. Active geothermal systems situated at on-land spreading centers provide a unique opportunity to study the hydration of the oceanic crust, with well constrained systems and boreholes reaching depths of >4 km. Here, we present hydrogen isotope data of geothermal fluids and altered basalt for three Icelandic geothermal systems: the meteoric water fed system at Krafla and the seawater fed systems at Reykjanes and Surtsey. The bulk rock δD values of altered and hydrated basalts from these localities, which exhibit significantly higher water contents (up to 8.9 wt.%) than magmatic (non-hydrated) basalts, vary greatly from −125 to −96‰ at Krafla, from −80 to −46‰ at Reykjanes and from −78 to −46‰ at Surtsey. The corresponding fluids have δD values of −84.1 to −81.1‰ at Krafla, −23.1 to −14.9‰ at Reykjanes and +2.1 to +4.3‰ at Surtsey. Comparison of isotope modeling results to the natural data reveals that hydration of the Icelandic crust and corresponding hydrogen isotopic characteristics are controlled by (1) the isotope composition of the source fluid, (2) isotope fractionation between the aqueous geothermal fluids and the alteration minerals formed, and (3) the type and quantity of alteration minerals formed. These factors in turn depend on the extent of fluid-rock interaction and temperature. Using the same modeling approach and expanding it to datasets available for the oceanic crust, we assessed the hydration state and δD values of the oceanic crust as a function of depth. We show that 1400 to 1650 Tg H2O/yr is added to the igneous oceanic crust upon alteration by seawater and that the upper part (<2 km) of oceanic crust hosts almost 50% of the added water. The corresponding hydrogen isotope composition of the hydrated crust was calculated to an average of −55±6‰. Upon subduction and subsequent dehydration, 80–90% of water with δD values of −35 to −10‰ will be released to the crustal forearc and mantle wedge. The remaining dehydrated slab with δD values of ∼−160 to −85‰ is expected to be transported to deeper levels modifying the mantle's water budget and isotopic composition. © 2020 Elsevier B.V.
关键词	fluid-rock interaction hydrogen isotopes oceanic crust water cycling
英文关键词	Basalt; Budget control; Geothermal fields; Hydrogen; Isotopes; Seawater; Constrained systems; Fluid-rock interaction; Hydrogen isotope; Isotope compositions; Isotope fractionation; Isotopic composition; Oceanic crust; Water cycling; Hydration; basalt; geothermal system; hydration; hydrogen isotope; hydrological cycle; isotopic composition; oceanic crust; water flux; water uptake; Iceland; Krafla; Reykjanes Peninsula; Surtsey
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/202701
作者单位	Nordic Volcanological Center, Institute of Earth Science, University of Iceland, Reykjavik, Iceland; Department of Geological Sciences, University of Texas at Austin, United States
推荐引用方式 GB/T 7714	Kleine B.I.,Stefánsson A.,Halldórsson S.A.,et al. Impact of fluid-rock interaction on water uptake of the Icelandic crust: Implications for the hydration of the oceanic crust and the subducted water flux[J],2020,538.
APA	Kleine B.I.,Stefánsson A.,Halldórsson S.A.,&Barnes J.D..(2020).Impact of fluid-rock interaction on water uptake of the Icelandic crust: Implications for the hydration of the oceanic crust and the subducted water flux.Earth and Planetary Science Letters,538.
MLA	Kleine B.I.,et al."Impact of fluid-rock interaction on water uptake of the Icelandic crust: Implications for the hydration of the oceanic crust and the subducted water flux".Earth and Planetary Science Letters 538(2020).