Magmatic Contributions to Seafloor Hydrothermal systems Revealed by Native Sulfur Isotopes
Table of Contents
Recent research published in Marine Chemistry demonstrates a direct link between magmatic processes and the metal content of seafloor hydrothermal vents.A study led by Vesselin dekov and colleagues reveals that native sulfur (S0) found at these vents carries isotopic signatures indicative of magmatic degassing, specifically of zinc.This finding provides new evidence for how metals are transported from the Earth’s interior to the ocean.
Background: Seafloor Hydrothermal Vents and Metal Sources
Seafloor hydrothermal vents are fissures in the ocean floor that release geothermally heated water. These vents are known to be hotspots for various chemical elements, including economically important metals like zinc, copper, and gold. The origin of these metals has been a long-standing question in marine geochemistry. Traditionally,sources were thought to be primarily derived from seawater interaction with rocks,or leaching from the oceanic crust. However, the new research suggests a significant contribution directly from magma.
New Isotopic Evidence from Native Sulfur
The research team analyzed the isotopic composition of native sulfur (S0) collected from seafloor hydrothermal systems. Sulfur isotopes (specifically, ratios of 34S to 32S) can reveal the source of the sulfur. The study found that the sulfur exhibited isotopic signatures suggesting two primary sources:
* Terrestrial Mantle Sulfide: Sulfur originating from the Earth’s mantle.
* Synproportionation of Magmatic SO2 and H2S: A process where sulfur dioxide (SO2) and hydrogen sulfide (H2S) gases, both released from magma, combine and alter the isotopic composition of the sulfur.A higher δ34S value in the sample indicates this process.
Crucially, the sulfur also carried isotopic signatures of zinc (δ66Zn) that were lighter than those found in the bulk silicate Earth. This indicates the zinc originated from a magmatic source. This is because magmatic degassing carries a distinct zinc isotopic signature.
“Thus, the seafloor hydrothermal native S0 provides new isotopic evidence for direct magmatic contribution of metals to seafloor hydrothermal systems and appears to be a messenger for magmatic volatile metal discharge in the ocean,” the authors state in thier publication. https://doi.org/10.1016/j.marchem.2025.104585
Implications for Understanding Metal Fluxes in the Ocean
This research has significant implications for understanding the global cycling of metals in the ocean and the formation of seafloor massive sulfide deposits.It suggests that magmatic degassing is a more important source of metals to hydrothermal systems than previously thought.
* Magmatic Volatiles as a Transport Mechanism: The study highlights the role of volatile compounds (like SO2 and H2S) released from magma as key carriers of metals to the seafloor.
* Refining models of Ore Deposit Formation: Understanding the magmatic contribution to hydrothermal systems is crucial for developing more accurate models of how seafloor massive sulfide ore deposits form. These deposits are important sources of copper, zinc, and othre valuable metals.
* Impact on Ocean Chemistry: Magmatic degassing influences the overall chemical composition of seawater, and this research provides a new tool for quantifying that impact.
Key Takeaways
* Native sulfur at seafloor hydrothermal vents provides a novel way to trace the source of metals.
* Isotopic analysis reveals a significant magmatic contribution to metal fluxes in these systems.
* Magmatic degassing, via SO2 and H2S, is a key transport mechanism for metals from the Earth’s interior to the ocean.
* This research improves our understanding of ore deposit formation and ocean chemistry.
Future Research
Further research will focus on quantifying the relative contributions of different magmatic sources to seafloor hydrothermal systems and exploring the global extent of this phenomenon. Investigating other metals beyond zinc, and examining vents associated with different types of volcanic activity, will also be important next steps. The study, published in December 2025, represents a significant advancement in our understanding of the complex interplay between magmatic processes and the ocean surroundings.
Citation: Dekov, V., Guéguen, B., Yamanaka, T., Koschinsky, A., Petersen, S., Paul, S. A. L., kleint, C.,Bach,W., & de Lange, G. J. (2025). Magmatic volatile contributions to seafloor hydrothermal systems revealed by native S isotopes. Marine Chemistry, 273, 104585. [https://doi.org/10.1016/j.marchem.2025.104585](https://doi.org/10.1016/j.marchem.202
Keep reading