Flux melting of subducting carbonated sediments: An experimental study
Subduction zones play a critical role in the global carbon cycle by regulating carbon exchange between the Earth's surface and interior. Processes that are known to release carbon from the slab, including metamorphic decarbonation and carbonate dissolution, cannot explain the high CO2 flux in m...
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| Format: | Article |
| Language: | English |
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Elsevier
2023-11-01
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| Series: | Geosystems and Geoenvironment |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2772883823000419 |
| _version_ | 1797670238391631872 |
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| author | Wei Chen Guoliang Zhang Takahashi Eiichi Li Li |
| author_facet | Wei Chen Guoliang Zhang Takahashi Eiichi Li Li |
| author_sort | Wei Chen |
| collection | DOAJ |
| description | Subduction zones play a critical role in the global carbon cycle by regulating carbon exchange between the Earth's surface and interior. Processes that are known to release carbon from the slab, including metamorphic decarbonation and carbonate dissolution, cannot explain the high CO2 flux in magmatic arcs. Slab melting is the least considered mechanism for carbon mobilization at subarc depths based on the high solidus temperatures of carbonated lithologies, which were experimentally determined under dry or H2O-absent conditions. Subducted sediments are major carbon carriers, however, their melting behaviour with excess H2O remains largely unexplored. Here, we perform fluid-present melting, high-pressure experiments at 750–1100 °C and 2.5–4 GPa using starting compositions similar to global average subducted sediments to determine the solidus, melting relations and carbonate stability fields. The onset of melting is between 750 and 800 °C at 2.5 GPa and between 850 and 900 °C at 4 GPa. Dolomite melts out on or close to the solidus, whereas crystalline aragonite persists >150 °C above the solidus. Flux melting of carbonated sediment at moderately hot subduction zones is examined to be feasible in the framework of the previously constructed dehydration history of the underlying serpentinites, providing a pathway to transfer carbon from the slab to the subarc mantle. However, complete breakdown of refractory aragonite requires at least 50 °C higher than that predicted for the hottest slab P‒T paths. Thus, even in the presence of H2O, partial subducted carbon may survive the melting event occurring at shallow regions and reach considerable mantle depths. |
| first_indexed | 2024-03-11T20:56:51Z |
| format | Article |
| id | doaj.art-7eb47472471a4b5f98fc1ac86dfa9764 |
| institution | Directory Open Access Journal |
| issn | 2772-8838 |
| language | English |
| last_indexed | 2024-03-11T20:56:51Z |
| publishDate | 2023-11-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Geosystems and Geoenvironment |
| spelling | doaj.art-7eb47472471a4b5f98fc1ac86dfa97642023-09-30T04:55:52ZengElsevierGeosystems and Geoenvironment2772-88382023-11-0124100218Flux melting of subducting carbonated sediments: An experimental studyWei Chen0Guoliang Zhang1Takahashi Eiichi2Li Li3Center of Deep Sea Research Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, ChinaCenter of Deep Sea Research Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266000, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China; Corresponding author at: Center of Deep Sea Research Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China.State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, ChinaState Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, ChinaSubduction zones play a critical role in the global carbon cycle by regulating carbon exchange between the Earth's surface and interior. Processes that are known to release carbon from the slab, including metamorphic decarbonation and carbonate dissolution, cannot explain the high CO2 flux in magmatic arcs. Slab melting is the least considered mechanism for carbon mobilization at subarc depths based on the high solidus temperatures of carbonated lithologies, which were experimentally determined under dry or H2O-absent conditions. Subducted sediments are major carbon carriers, however, their melting behaviour with excess H2O remains largely unexplored. Here, we perform fluid-present melting, high-pressure experiments at 750–1100 °C and 2.5–4 GPa using starting compositions similar to global average subducted sediments to determine the solidus, melting relations and carbonate stability fields. The onset of melting is between 750 and 800 °C at 2.5 GPa and between 850 and 900 °C at 4 GPa. Dolomite melts out on or close to the solidus, whereas crystalline aragonite persists >150 °C above the solidus. Flux melting of carbonated sediment at moderately hot subduction zones is examined to be feasible in the framework of the previously constructed dehydration history of the underlying serpentinites, providing a pathway to transfer carbon from the slab to the subarc mantle. However, complete breakdown of refractory aragonite requires at least 50 °C higher than that predicted for the hottest slab P‒T paths. Thus, even in the presence of H2O, partial subducted carbon may survive the melting event occurring at shallow regions and reach considerable mantle depths.http://www.sciencedirect.com/science/article/pii/S2772883823000419Deep carbon cycleSubduction zoneCarbonated sedimentHigh-pressure experiments |
| spellingShingle | Wei Chen Guoliang Zhang Takahashi Eiichi Li Li Flux melting of subducting carbonated sediments: An experimental study Geosystems and Geoenvironment Deep carbon cycle Subduction zone Carbonated sediment High-pressure experiments |
| title | Flux melting of subducting carbonated sediments: An experimental study |
| title_full | Flux melting of subducting carbonated sediments: An experimental study |
| title_fullStr | Flux melting of subducting carbonated sediments: An experimental study |
| title_full_unstemmed | Flux melting of subducting carbonated sediments: An experimental study |
| title_short | Flux melting of subducting carbonated sediments: An experimental study |
| title_sort | flux melting of subducting carbonated sediments an experimental study |
| topic | Deep carbon cycle Subduction zone Carbonated sediment High-pressure experiments |
| url | http://www.sciencedirect.com/science/article/pii/S2772883823000419 |
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