The Application of Raman Shift of Sulfate in Temperature Detection of Deep-Sea Hydrothermal Fluid

Abstract

Hydrothermal field is a typical deep-sea extreme environment where there are various sulfide minerals and special ecological communities. The research on the physicochemical characters of hydrothermal fluid is essential to the understanding of hydrothermal activities. The laser Raman spectroscopy has been used both at the qualitative and quantitative analysis, especially the in situ detections in the deep sea. In this paper, we simulated the hydrothermal fluid environment characterized by high temperature and high pressure, and discussed the availability of the Raman shifts of water and sulfate for detecting the temperature of the deep-sea hydrothermal fluids. The experiment results showed that the Raman shifts of the nu(1) (H2O) and nu(1) (SO42-) were sensitive to the temperature. However, the Raman shifts of the nu(1) (H2O) are also affected by the concentration of sulfate obviously, which is an obstacle to calculating the temperature of the hydrothermal fluid. On the contrary, the Raman shift of the nu(1) (SO42-) is insensitive to the concentration of sulfate and fluid pressure, which makes it a good choice to calculate the temperature of the hydrothermal fluid. Therefore, we established the liner relationship equationof the nu(1) (SO42-) Raman shift with temperature: R-nu 1 ((SO42-)) = -0. 03T+980. 69, R-2 = 0. 998 6, which is also suitable for the in situ measurements of the hydrothermal fluid in the deep sea.