硫酸根拉曼频移用于深海热液温度探测的方法探讨

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

作为一种典型的深海极端环境,热液区域不仅分布着各种硫化物矿产,而且孕育着特殊的生态群落,对热液流体理化性质的研究有助于深入了解热液的运动机制。激光拉曼光谱技术除了定性分析方面的优势外,已经被逐步用于定量分析,并且在原位探测中发挥了重要作用。该研究模拟了深海热液喷口流体的高温高压环境,探讨了水分子和硫酸根离子的拉曼光谱在热液流体温度探测中的应用价值。通过对水峰ν_1(H_2O)、硫酸根ν_1(SO_4^(2-))的拉曼频移与温度、离子浓度的关系进行研究,结果表明水峰ν_1(H_2O)和硫酸根ν_1(SO_4^(2-))的拉曼频移随温度表现出明显的变化,水峰ν_1(H_2O)的拉曼频移受流体硫酸根浓度的影响明显,因此不适用于硫酸根离子浓度变化明显的热液流体温度的测量。相比之下,ν_1(SO_4^(2-))的拉曼频移对流体硫酸根浓度和流体压力不敏感,为温度的反演提供了很好的依据。建立了ν_1(SO_4^(2-))的拉曼频移与温度的线性方程:Rν_1(SO_4^(2-))=-0.03T+980.69,其中,R^2=0.998 6,可用于对深海热液喷口流体温度的原位探测等实际应用。

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 theν1(H 2O)andν1(SO 2-4)were sensitive to the temperature.However,the Raman shifts of theν1(H 2O)are also affected by the concentration of sulfate obviously,which is an obstacle to calculating the tem perature of the hydrothermal fluid.On the contrary,the Raman shift of theν1(SO 2-4)is insensitive to the concentration of sulfate and fluid pressure,which makes it a good choice to calculate the temperature of the hydr othermal fluid.Therefore,we established the liner relationship equationof theν1(SO 2-4)Raman shift with temperature:Rν1(SO 2-4)=-0.03 T+980.69,R 2=0.998 6,which is also suitable fo r the in situ measurements of the hydrothermal fluid in the deep sea.