Abstract
This study presents experimental, geochemical modeling, and field data focusing on the partitioning of osmium (Os) between pyrite and fluid upon precipitation at conditions representative of mid-ocean ridge hydrothermal environments. Dissolved Os partitions strongly into pyrite upon precipitation at experimental conditions, 350 °C and 50 MPa, with a representative relative Os/Fe partition coefficient, DPyrite-FluidOs/Fe, between 10 and 15. Integrating the experimentally determined DPyrite-FluidOs/Fe into a geochemical model indicates that a significant amount of Os is retained within the subseafloor due to sulfide precipitation induced by mixing of conductively heated seawater with pristine high temperature hydrothermal fluids that are enriched in dissolved metals, such as Os and Fe. Comparison with existing Os concentration and isotopic data of hydrothermal fluids and sulfide minerals from a wide range of hydrothermal systems with the experimental and modeling constraints suggest that modern high temperature hydrothermal systems are a minor source of unradiogenic Os to the modern global ocean dissolved Os budget due to the majority of Os being sequestered into sulfide minerals formed within and on the seafloor.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 240-255 |
| Number of pages | 16 |
| Journal | Geochimica et Cosmochimica Acta |
| Volume | 293 |
| DOIs | |
| State | Published - Jan 15 2021 |
| Externally published | Yes |
Bibliographical note
Funding Information:The paper benefited from constructive comments and recommendations of the anonymous reviewer, Dr. Tatsuo Nozaki, and GCA-AE, Dr. Jun-Ichiro Ishibashi. This study was funded primarily through the Flint Postdoctoral Fellowship awarded to DDS. DDS conducted the experiments and wrote the majority of the manuscript with the assistance of JK. LRY wrote the GWB script to allow for complex simulation of fluid mixing. BMT compiled Os thermodynamic data into an internally consistent thermodynamic database and coordinated mineralogical characterization of pyrite precipitates. ADR performed the Os concentration and isotopic measurements of the experimental solutions, product pyrite, and the natural sulfide presented in this study. WES provided the experimental equipment necessary for this study and acknowledges support from a National Science Foundation (NSF) grant (NSF-OCE-1736670). LRY was funded by the NSF Postdoctoral Research Fellowship in Biology (NSF-DBI-1812035). DDS would like to thank Dr. Dionysis Foustoukos (Carnegie Institute of Science) for sharing knowledge on experimental studies focused on Os. DDS also thanks Dr. Changle Wang and Cerys Holstege (Yale University) for providing assistance on the processing of samples and concentration measurements by ICP-MS. Finally, DDS would like to thank NSF and WHOI, the crew, the ECS team, ECS mentors, Drs. Dan Fornari (WHOI) and Mike Perfit (University of Florida), co-chiefs of the ECS cruise, Drs. Elizabeth Trembath-Reichert (Arizona State University) and Ross Parnell-Turner (Scripps Institute of Oceanography), and the NDSF HOV Alvin and AUV Sentry scientific teams aboard the R/V Atlantis on the AT42-06 expedition to the EPR 9°50’N hydrothermal system (NSF-OCE-1834797). Simone Pujatti and Robert Marr (both UCalgary) are thanked for their assistance with Raman spectroscopy and EMP/EDS analyses, respectively. Copyright for the image of P-vent ( Fig. 1 (a)) is by WHOI 2018, NDSF, Alvin Group, and NSF.
Funding Information:
The paper benefited from constructive comments and recommendations of the anonymous reviewer, Dr. Tatsuo Nozaki, and GCA-AE, Dr. Jun-Ichiro Ishibashi. This study was funded primarily through the Flint Postdoctoral Fellowship awarded to DDS. DDS conducted the experiments and wrote the majority of the manuscript with the assistance of JK. LRY wrote the GWB script to allow for complex simulation of fluid mixing. BMT compiled Os thermodynamic data into an internally consistent thermodynamic database and coordinated mineralogical characterization of pyrite precipitates. ADR performed the Os concentration and isotopic measurements of the experimental solutions, product pyrite, and the natural sulfide presented in this study. WES provided the experimental equipment necessary for this study and acknowledges support from a National Science Foundation (NSF) grant (NSF-OCE-1736670). LRY was funded by the NSF Postdoctoral Research Fellowship in Biology (NSF-DBI-1812035). DDS would like to thank Dr. Dionysis Foustoukos (Carnegie Institute of Science) for sharing knowledge on experimental studies focused on Os. DDS also thanks Dr. Changle Wang and Cerys Holstege (Yale University) for providing assistance on the processing of samples and concentration measurements by ICP-MS. Finally, DDS would like to thank NSF and WHOI, the crew, the ECS team, ECS mentors, Drs. Dan Fornari (WHOI) and Mike Perfit (University of Florida), co-chiefs of the ECS cruise, Drs. Elizabeth Trembath-Reichert (Arizona State University) and Ross Parnell-Turner (Scripps Institute of Oceanography), and the NDSF HOV Alvin and AUV Sentry scientific teams aboard the R/V Atlantis on the AT42-06 expedition to the EPR 9?50?N hydrothermal system (NSF-OCE-1834797). Simone Pujatti and Robert Marr (both UCalgary) are thanked for their assistance with Raman spectroscopy and EMP/EDS analyses, respectively. Copyright for the image of P-vent (Fig. 1(a)) is by WHOIy 2018, NDSF, Alvin Group, and NSF.
Publisher Copyright:
© 2020 Elsevier Ltd
Keywords
- Mid-ocean ridge hydrothermal systems
- Osmium
- Partitioning
- Pyrite