The hydrothermal activity in Dragon Flag field is much more recent than that of Duanqiao or Mt. The maximum age of the relict chimney in Duanqiao hydrothermal filed is close to that of the chimneys from Mt. This study is the first to estimate the growth rate of chimneys in the SWIR. The estimated mean growth rate of the sulfide chimney is <0.02 mm/yr. The periodic character of hydrothermal activity may be related to the heat source provided by the interaction of local magmatism and tectonism. Hydrothermal activity of Duanqiao probably started about 84.3 (☐.5) kyrs ago and ceased about 0.737 (☐.023) kyrs ago. Four main episodes of hydrothermal activity were determined according to the restricted results: 68.9–84.3, 43.9–48.4, 25.3–34.8, and 0.7–17.3 kyrs. Twenty-eight subsamples from a relict chimney and massive sulfides were dated using the 230Th/ 238U method. Duanqiao hydrothermal field is located between the Indomed and Gallieni fracture zones at the central volcano, at 50☂8′E in the ultraslow-spreading Southwest Indian Ridge (SWIR).
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