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Chlorine isotope ratios record magmatic brine assimilation during rhyolite genesis

Chlorine isotope ratios record magmatic brine assimilation during rhyolite genesis


Titill: Chlorine isotope ratios record magmatic brine assimilation during rhyolite genesis
Höfundur: Ranta, Eemu Johannes
Halldórsson, Sæmundur Ari   orcid.org/0000-0002-4724-8578
Barnes, J. D.
Jónasson, Kristján   orcid.org/0000-0002-9066-3128
Stefánsson, Andri
Útgáfa: 2021-01-13
Tungumál: Enska
Umfang: 5
Deild: Faculty of Earth Sciences
Science Institute
Faculty of Industrial Engineering, Mechanical Engineering and Computer Science
Birtist í: Geochemical Perspectives Letters; 16()
ISSN: 2410-339X
DOI: https://doi.org/10.7185/GEOCHEMLET.2101
Efnisorð: Hraun; Gosberg; Klór; Klórsamsætur; Klórsamsætur; Chlorine isotopes; Hydrosaline fluids; Magmatic brine; Magmatic volatiles; Silicic magma; Magma mush; Environmental Chemistry; Geology; Geochemistry and Petrology
URI: https://hdl.handle.net/20.500.11815/2719

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Tilvitnun:

Ranta , E J , Halldórsson , S A , Barnes , J D , Jónasson , K & Stefánsson , A 2021 , ' Chlorine isotope ratios record magmatic brine assimilation during rhyolite genesis ' , Geochemical Perspectives Letters , vol. 16 , pp. 35-39 . https://doi.org/10.7185/GEOCHEMLET.2101

Útdráttur:

Magmatic volatile phases within crustal silicic magma domains influence key volcanic processes such as the build up to eruptions and formation of magmatic-hydrothermal ore deposits. However, the extent and nature of fluid-melt interaction in such environments is poorly understood, as geochemical signals in volcanic rocks originating from pre-eruptive volatile processes are commonly overprinted by syn-eruptive degassing. Here, we use δ37Cl as a conservative tracer of brine-melt interaction on a broad suite of silicic volcanic rocks from Iceland. We find that the δ37Cl values of silicic rocks are systematically shifted to more negative values compared to associated basalts and intermediate rocks by up to 2.9 . These large shifts cannot be explained by well known processes inherent to silicic magma genesis, including crustal assimilation, mineral-melt fractionation and syn-eruptive degassing. Instead, we show that low δ37Cl values in silicic rocks can be attributed to assimilation of magmatic brines that are formed and stored in long lived crustal magma mushes. Our results indicate that magmatic brine assimilation is a fundamental, but previously unrecognised part of rhyolite genesis.

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Publisher Copyright: © 2021 The Authors.

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