Journal of Marine Sciences ›› 2017, Vol. 35 ›› Issue (4): 34-43.DOI: 10.3969/j.issn.1001-909X.2017.04.004

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Characteristics of water chemistry and constituents of particles in the hydrothermal plume near 6°48′N, Carlsberg Ridge, Northwest Indian Ocean

JIANG Zi-jing1,2, HAN Xi-qiu1,2, WANG Ye-jian1,2, QIU Zhong-yan1,2   

  1. 1. Second Institute of Oceanography, SOA, Hangzhou 310012, China;
    2. Laboratory of Submarine Geosciences, SOA, Hangzhou 310012, China
  • Received:2017-03-07 Revised:2017-04-10 Published:2022-11-21

Abstract: In 2015, a hydrothermal field named Daxi was discovered during the Chinese DY33 cruise at 6°48′N, Carlsberg Ridge, Northwest Indian Ocean. The chemistry of water samples and particles of a CTD station near Daxi Hydrothermal Field was studied. In the water depth of 3 150~3 400 m, the water chemistry shows slight depletion of Cl, Br, Mg and intense enrichment of DFe and DMn. The concentrations of Cl, Br, Mg deplete 2.87%~5.27%, 3.21%~4.53% and 2.52%~3.82%, respectively, when comparing to background seawater. It is suggested that the hydrothermal fluid has been subjected to phase separation, resulting in the depletion of Cl and Br. The depletion of Mg suggests that the hydrothermal plume has been well mixed with the ambient seawater and the contribution of hydrothermal fluid is account for about 3.90%. The concentrations of DFe and DMn reach to 127 nmol/L and 29.0 nmol/L, respectively, for the sample collected at 3 150 m water depth. The particles have been investigated under scanning electron microscope and analyzed by energy dispersive X-Ray spectrometer. The results show that among the particles in the water depth of 2 900~3 400 m, there are more iron oxides or hydroxides (49.1%~95.2% FeO) present, and this discovery is consistent with the enrichment of DFe and DMn in the water samples. According to the current speed and the diffuse radius of Fe(Ⅱ), the calculated value of Fe(Ⅱ) oxidation half-live in Daxi hydrothermal field is 0.56~2.22 h.

Key words: Carlsberg Ridge, Daxi Hydrothermal Field, hydrothermal plumes, chemical anomalies of seawater, constituents of particles

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