Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Geochemistry, Geophysics, Geosystems Année : 2024

Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin

Apolline Samin
Desiree L. Roerdink
  • Fonction : Auteur
Eoghan P. Reeves
Johannes Scheffler
  • Fonction : Auteur
Wolfgang Bach
Andreas Beinlich
  • Fonction : Auteur
Olivier Rouxel

Résumé

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.
Fichier principal
Vignette du fichier
Geochem Geophys Geosyst - 2024 - Samin - Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich.pdf (2.78 Mo) Télécharger le fichier
Origine : Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

hal-04540165 , version 1 (11-04-2024)

Licence

Paternité

Identifiants

Citer

Apolline Samin, Desiree L. Roerdink, Eoghan P. Reeves, Johannes Scheffler, Wolfgang Bach, et al.. Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin. Geochemistry, Geophysics, Geosystems, 2024, 25 (2), e2023GC011349 (17p.). ⟨10.1029/2023GC011349⟩. ⟨hal-04540165⟩
0 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More