Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin
Abstract Copper isotopes (δ65Cu) in hydrothermal fluids have the potential to provide information on ore‐forming processes occurring below the seafloor, but Cu isotope data from high‐temperature fluids are scarce. Here, we examine the extent to which coexisting sulfide minerals in a hydrothermal chi...
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| Format: | Article |
| Language: | English |
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Wiley
2024-02-01
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| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2023GC011349 |
| _version_ | 1797262489253052416 |
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| author | Apolline Samin Desiree L. Roerdink Eoghan P. Reeves Johannes Scheffler Wolfgang Bach Andreas Beinlich John W. Jamieson Olivier Rouxel |
| author_facet | Apolline Samin Desiree L. Roerdink Eoghan P. Reeves Johannes Scheffler Wolfgang Bach Andreas Beinlich John W. Jamieson Olivier Rouxel |
| author_sort | Apolline Samin |
| collection | DOAJ |
| description | Abstract Copper isotopes (δ65Cu) in hydrothermal fluids have the potential to provide information on ore‐forming processes occurring below the seafloor, but Cu isotope data from high‐temperature fluids are scarce. Here, we examine the extent to which coexisting sulfide minerals in a hydrothermal chimney can preserve fluid Cu isotope ratios using a fluid‐solid pair of a black smoker (333°C) from the Roman Ruins vent area (PACMANUS) in the Manus Basin. Two ca. 3 cm long transects through the chalcopyrite‐rich chimney wall show an increase in δ65Cu from 0.48 to 2.28‰ from the interior to the exterior, coupled with limited variation in sulfide δ34S (1.52–4.72‰). The Cu isotopic composition of chalcopyrite from the innermost wall closely resembles the δ65Cu value of the paired hydrothermal fluid, indicating that chalcopyrite in the inner ∼5 mm of the chimney records the Cu isotope ratio of the venting fluid. Beyond this, an increase in sulfide δ65Cu toward the exterior correlates with an increase in the relative abundance of secondary Cu sulfides. The appearance of bornite coincides with the presence of small barite crystals, suggesting this represents a redox gradient between reduced hydrothermal fluids and oxidized seawater admixing inwards. Elevated δ65Cu in this zone can be explained by the precipitation of secondary Cu sulfides from 65Cu‐enriched fluids formed during oxidative chalcopyrite dissolution. Our findings indicate that interactions with oxidizing seawater shift chalcopyrite δ65Cu values over small spatial scales, and that caution must be applied if chimney sulfides are used to reconstruct δ65Cu values of high‐temperature hydrothermal fluids. |
| first_indexed | 2024-03-07T21:33:23Z |
| format | Article |
| id | doaj.art-16abba80724046b1aed8a6abb9508faf |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-04-24T23:57:55Z |
| publishDate | 2024-02-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-16abba80724046b1aed8a6abb9508faf2024-03-14T10:55:31ZengWileyGeochemistry, Geophysics, Geosystems1525-20272024-02-01252n/an/a10.1029/2023GC011349Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus BasinApolline Samin0Desiree L. Roerdink1Eoghan P. Reeves2Johannes Scheffler3Wolfgang Bach4Andreas Beinlich5John W. Jamieson6Olivier Rouxel7Department of Earth Science and Centre for Deep Sea Research University of Bergen Bergen NorwayDepartment of Earth Science and Centre for Deep Sea Research University of Bergen Bergen NorwayDepartment of Earth Science and Centre for Deep Sea Research University of Bergen Bergen NorwayDepartment of Earth Science and Centre for Deep Sea Research University of Bergen Bergen NorwayMARUM‐Center for Marine Environmental Sciences & Department of Geosciences University of Bremen Bremen GermanyDepartment of Earth Science and Centre for Deep Sea Research University of Bergen Bergen NorwayDepartment of Earth Science Memorial University of Newfoundland St. John's NL CanadaDepartment of Marine Geosciences IFREMER Plouzané FranceAbstract Copper isotopes (δ65Cu) in hydrothermal fluids have the potential to provide information on ore‐forming processes occurring below the seafloor, but Cu isotope data from high‐temperature fluids are scarce. Here, we examine the extent to which coexisting sulfide minerals in a hydrothermal chimney can preserve fluid Cu isotope ratios using a fluid‐solid pair of a black smoker (333°C) from the Roman Ruins vent area (PACMANUS) in the Manus Basin. Two ca. 3 cm long transects through the chalcopyrite‐rich chimney wall show an increase in δ65Cu from 0.48 to 2.28‰ from the interior to the exterior, coupled with limited variation in sulfide δ34S (1.52–4.72‰). The Cu isotopic composition of chalcopyrite from the innermost wall closely resembles the δ65Cu value of the paired hydrothermal fluid, indicating that chalcopyrite in the inner ∼5 mm of the chimney records the Cu isotope ratio of the venting fluid. Beyond this, an increase in sulfide δ65Cu toward the exterior correlates with an increase in the relative abundance of secondary Cu sulfides. The appearance of bornite coincides with the presence of small barite crystals, suggesting this represents a redox gradient between reduced hydrothermal fluids and oxidized seawater admixing inwards. Elevated δ65Cu in this zone can be explained by the precipitation of secondary Cu sulfides from 65Cu‐enriched fluids formed during oxidative chalcopyrite dissolution. Our findings indicate that interactions with oxidizing seawater shift chalcopyrite δ65Cu values over small spatial scales, and that caution must be applied if chimney sulfides are used to reconstruct δ65Cu values of high‐temperature hydrothermal fluids.https://doi.org/10.1029/2023GC011349seafloor hydrothermal systemscopper isotopesblack smokerchalcopyrite‐rich chimney |
| spellingShingle | Apolline Samin Desiree L. Roerdink Eoghan P. Reeves Johannes Scheffler Wolfgang Bach Andreas Beinlich John W. Jamieson Olivier Rouxel Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin Geochemistry, Geophysics, Geosystems seafloor hydrothermal systems copper isotopes black smoker chalcopyrite‐rich chimney |
| title | Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin |
| title_full | Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin |
| title_fullStr | Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin |
| title_full_unstemmed | Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin |
| title_short | Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin |
| title_sort | preservation of hydrothermal fluid copper isotope signatures in chalcopyrite rich chimneys a case study from the pacmanus vent field manus basin |
| topic | seafloor hydrothermal systems copper isotopes black smoker chalcopyrite‐rich chimney |
| url | https://doi.org/10.1029/2023GC011349 |
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