The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles

The extent to which Earth’s sub-continental lithospheric mantle modulates the flux of volatile elements from our planet’s deep interior to its atmosphere (via volcanism) is poorly constrained. Here, we focus on “off-craton” sub-continental lithospheric mantle because this long-lived reservoir potent...

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Main Authors: Gibson, Sally, Rooks, Eve, Day, Jason, Petrone, Chiara, Leat, Phillip
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier 2020
Subjects:
Online Access:https://www.repository.cam.ac.uk/handle/1810/302686
https://doi.org/10.17863/CAM.49757
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spelling ftunivcam:oai:www.repository.cam.ac.uk:1810/302686 2024-01-21T10:00:17+01:00 The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles Gibson, Sally Rooks, Eve Day, Jason Petrone, Chiara Leat, Phillip 2020 application/vnd.openxmlformats-officedocument.wordprocessingml.document https://www.repository.cam.ac.uk/handle/1810/302686 https://doi.org/10.17863/CAM.49757 eng eng Elsevier http://dx.doi.org/10.1016/j.gca.2020.02.018 Geochimica et Cosmochimica Acta https://www.repository.cam.ac.uk/handle/1810/302686 doi:10.17863/CAM.49757 Attribution-NonCommercial-NoDerivatives 4.0 International https://creativecommons.org/licenses/by-nc-nd/4.0/ Mantle Volatiles Global volatile cycles Pyroxenite Peridotite Article 2020 ftunivcam https://doi.org/10.17863/CAM.49757 2023-12-28T23:19:41Z The extent to which Earth’s sub-continental lithospheric mantle modulates the flux of volatile elements from our planet’s deep interior to its atmosphere (via volcanism) is poorly constrained. Here, we focus on “off-craton” sub-continental lithospheric mantle because this long-lived reservoir potentially acts as both a volatile “sink” and “source” during major heating and rifting events. The sub-continental lithospheric mantle is primarily formed of peridotites with subordinate amounts of pyroxenites. While both lithologies are dominated by nominally-volatile-free mantle minerals, some of these phases have been shown to contain non-negligible amounts of H2O (e.g. 100’s of ppmw in clinopyroxene). Data for volatile elements other than Li are, however, limited. We present new, high-precision, in-situ Secondary Ion Mass Spectrometry analyses of H, F, Cl, Li and B in olivine and pyroxenes from well-characterised garnet- and spinel-bearing peridotites and pyroxenites (from southern Patagonia and the Antarctic Peninsula). Our study confirms that clinopyroxene is the main host of H2O and F. The maximum F contents we report (up to 154 ppmw) are higher than those in previous studies and occur in Ti-Cr diopsides in highly-metasomatised peridotites and Ti-Al augites from clinopyroxenite veins. Water contents of clinopyroxenes (up to 615 ppmw) are within the range previously published for continental mantle. Lithium concentrations are low (<5 ppmw) in all analysed phases and both Cl and B are below detection levels (14 ppmw and 0.03 ppmw, respectively). Unique to our study is the large variation in major- and trace-element concentrations of the clinopyroxenes, which allows us to place quantitative constraints on how volatiles are stored in the mantle. We demonstrate that: (i) F contents of clinopyroxenes closely correlate with Ti and (ii) D_H^(Cpx-Opx) and D_F^(Cpx-Opx)is systematic and inversely correlated with temperature. Despite the redistribution of volatiles during sub-solidus re-equilibration, we show that the ... Article in Journal/Newspaper Antarc* Antarctic Antarctic Peninsula Apollo - University of Cambridge Repository Antarctic The Antarctic Antarctic Peninsula Patagonia
institution Open Polar
collection Apollo - University of Cambridge Repository
op_collection_id ftunivcam
language English
topic Mantle
Volatiles
Global volatile cycles
Pyroxenite
Peridotite
spellingShingle Mantle
Volatiles
Global volatile cycles
Pyroxenite
Peridotite
Gibson, Sally
Rooks, Eve
Day, Jason
Petrone, Chiara
Leat, Phillip
The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles
topic_facet Mantle
Volatiles
Global volatile cycles
Pyroxenite
Peridotite
description The extent to which Earth’s sub-continental lithospheric mantle modulates the flux of volatile elements from our planet’s deep interior to its atmosphere (via volcanism) is poorly constrained. Here, we focus on “off-craton” sub-continental lithospheric mantle because this long-lived reservoir potentially acts as both a volatile “sink” and “source” during major heating and rifting events. The sub-continental lithospheric mantle is primarily formed of peridotites with subordinate amounts of pyroxenites. While both lithologies are dominated by nominally-volatile-free mantle minerals, some of these phases have been shown to contain non-negligible amounts of H2O (e.g. 100’s of ppmw in clinopyroxene). Data for volatile elements other than Li are, however, limited. We present new, high-precision, in-situ Secondary Ion Mass Spectrometry analyses of H, F, Cl, Li and B in olivine and pyroxenes from well-characterised garnet- and spinel-bearing peridotites and pyroxenites (from southern Patagonia and the Antarctic Peninsula). Our study confirms that clinopyroxene is the main host of H2O and F. The maximum F contents we report (up to 154 ppmw) are higher than those in previous studies and occur in Ti-Cr diopsides in highly-metasomatised peridotites and Ti-Al augites from clinopyroxenite veins. Water contents of clinopyroxenes (up to 615 ppmw) are within the range previously published for continental mantle. Lithium concentrations are low (<5 ppmw) in all analysed phases and both Cl and B are below detection levels (14 ppmw and 0.03 ppmw, respectively). Unique to our study is the large variation in major- and trace-element concentrations of the clinopyroxenes, which allows us to place quantitative constraints on how volatiles are stored in the mantle. We demonstrate that: (i) F contents of clinopyroxenes closely correlate with Ti and (ii) D_H^(Cpx-Opx) and D_F^(Cpx-Opx)is systematic and inversely correlated with temperature. Despite the redistribution of volatiles during sub-solidus re-equilibration, we show that the ...
format Article in Journal/Newspaper
author Gibson, Sally
Rooks, Eve
Day, Jason
Petrone, Chiara
Leat, Phillip
author_facet Gibson, Sally
Rooks, Eve
Day, Jason
Petrone, Chiara
Leat, Phillip
author_sort Gibson, Sally
title The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles
title_short The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles
title_full The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles
title_fullStr The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles
title_full_unstemmed The role of sub-continental mantle as both “sink” and “source” in deep Earth volatile cycles
title_sort role of sub-continental mantle as both “sink” and “source” in deep earth volatile cycles
publisher Elsevier
publishDate 2020
url https://www.repository.cam.ac.uk/handle/1810/302686
https://doi.org/10.17863/CAM.49757
geographic Antarctic
The Antarctic
Antarctic Peninsula
Patagonia
geographic_facet Antarctic
The Antarctic
Antarctic Peninsula
Patagonia
genre Antarc*
Antarctic
Antarctic Peninsula
genre_facet Antarc*
Antarctic
Antarctic Peninsula
op_relation https://www.repository.cam.ac.uk/handle/1810/302686
doi:10.17863/CAM.49757
op_rights Attribution-NonCommercial-NoDerivatives 4.0 International
https://creativecommons.org/licenses/by-nc-nd/4.0/
op_doi https://doi.org/10.17863/CAM.49757
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