426 / 2024-09-16 20:19:39
In situ Raman quantitative detection of the different magmatic-hydrothermal fluids from the same magma source at the DESMOS caldera
In situ,,Raman quantitative detection,,magmatic-hydrothermal,hydrogoen
Session 40 - Geochemical characteristics of submarine hydrothermal systems and the evolution of hydrothermal plumes
Abstract Accepted
Shichuan Xi / Laoshan Laboratory
Qinglei Sun / Institute of Oceanology, Chinese Academy of Sciences
Ruifang Huang / South China Sea Institute of Oceanology, Chinese Academy of Sciences
Zhendong Luan / Institute of Oceanology, Chinese Academy of Sciences
Zengfeng Du / Institute of Oceanology, Chinese Academy of Sciences
Lianfu Li / Laoshan Laboratory
Xin Zhang / Institute of Oceanology, Chinese Academy of Sciences
Submarine magmatic-hydrothermal system represents a unique hydrothermal system caused by the direct mixing of magmatic volatiles with seawater, which generates huge material and heat fluxes, and shows broad range of chemical and physical variability. However, the fluid components, especially gases, vary as a result of drastic temperature and pressure changes during the measurement process, affecting the accurate assessments of the hydrothermal fluxes.

Recently, we developed a high temperature resistant (up to 450°C) Raman insertion probe for hydrothermal vent (RiP-Hv) that can be applied to hydrothermal fluid measurement. Here, a high-precision in situ Raman quantitative technique was used for the hydrothermal fluids at the Onsen site and a newly found site named Faxian in a magmatic-hydrothermal system at the DESMOS caldera, Manus back-arc basin. The maximum in situ H2 concentration (8.56 mmol/kg) and measured H2 concentration in the lab (26.51 mmol/kg) at the Onsen site are the highest values ever reported in the similar hydrothermal systems. In contrast, the diffuse fluid at the Faxian site was characterized by rich H2S (7.78 mmol/kg,) but without H2. The differences at mixing contents of seawater induced different geochemical reactions and fluxes of hydrogen and hydrogen sulfide. Furthermore, the existence of hydrogen- and sulfide-oxidizing genes suggests that the oxidation of hydrogen and hydrogen sulfide are the energy sources of the microbial communities at the two sites even within the same magma source.

Approximately 75% of submarine volcanic activity are distributed at the volcanic arc and back-arc and accompanied with diverse microbial communities, which suggests widespread submarine magmatic-hydrothermal systems contribute to studying the hydrothermal fluxes, and relationships between early life and volcanism based on in situ detection.