Publication Date:
2022-10-26
Description:
© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wilckens, F. K., Reeves, E. P., Bach, W., Seewald, J. S., & Kasemann, S. A. Application of B, mg, li, and sr isotopes in acid-sulfate vent fluids and volcanic rocks as tracers for fluid-rock interaction in back-arc hydrothermal systems. Geochemistry Geophysics Geosystems, 20, (2019): 5849-5866, doi: 10.1029/2019GC008694.
Description:
The Manus Basin hosts a broad range of vent fluid compositions typical for arc and back‐arc settings, ranging from black smoker to acid‐sulfate styles of fluid venting, as well as novel intermediate temperature and composition “hybrid” smokers. We investigated B, Li, Mg, and Sr concentrations and isotopic compositions of these different fluid types as well as of fresh and altered rocks from the same study area to understand what controls their compositional variability. In particular, the formation of acid‐sulfate and hybrid smoker fluids is still poorly understood, and their high Mg concentrations are explained either by dissolution of Mg‐bearing minerals in the basement or by mixing between unmodified seawater and magmatic fluids. Mg isotope ratios of the acid‐sulfate fluids from the Manus Basin are seawater‐like, which supports the idea that acid‐sulfate fluids in this study area predominantly form by mixing between unmodified seawater and a Mg‐free magmatic fluid. Changes in the B, Li, and Sr isotope ratios relative to seawater indicate water‐rock interaction in all acid‐sulfate fluids. Further, the combination of δ7Li with B concentrations of the same fluids links changes in δ7Li to changes in (1) basement alteration, (2) water‐to‐rock ratios during water‐rock interaction, and/or (3) the reaction temperature. These isotope systems, thus, allow tracing of basement composition and acid‐sulfate‐driven alteration of the back‐arc crust and help increase our understanding of hydrothermal fluid‐rock interactions and the behavior of fluid‐mobile elements.
Description:
The authors would like to thank the crew of the R/V Melville and R/V Sonne as well as the technical groups of ROV Jason II and ROV MARUM‐QUEST. This study was part of MARUM project GB4 and was funded by the DFG‐Research Centre/Cluster of Excellence “The Ocean in the Earth System” at MARUM—Centre for Environmental Sciences, University of Bremen (EXC309/FZT15) and was supported from the German Research Foundation (DFG) Major Research Instrumentation Program (INST 144/308‐1). We would also like to thank Dionysis Foustoukos and an anonymous reviewer for the thorough reviews, which improved the manuscript a lot. The data reported in this paper are archived in Pangaea (https://doi.pangaea.de/10.1594/PANGAEA.908303).
Keywords:
Hydrothermal fluids
;
Back‐arc
;
Basement alteration
;
Acid‐sulfate
Repository Name:
Woods Hole Open Access Server
Type:
Article
Permalink
