Discovery and characterization of a new hydrothermal field at 2N on the slow-spreading Carlsberg Ridge

A new hydrothermal field (Tianshi) was discovered on the rift valley wall through plume anomaly surveys and geological work conducted in 2012 and 2018 between 2 degrees 35 ' N and 2 degrees 43 ' N of the slow-spreading Carlsberg Ridge (CR). Here, the results of two expeditions conducted to detect and characterize the new hydrothermal field are reported. Mineralogical and geochemical data, as well as 14C ages of a sediment core collected near the field are presented to reveal the hydrothermal history. Results show that the Tianshi field is a basalt-hosted hydrothermal system. Geochemical data of the sediments collected near the field indicate a strong hydrothermal contribution, and hydrothermal Fe and Cu fluxes range from 30 to 155 mg/(cm2.ka) and 0.59 to 11.49 mg/(cm2.ka), respectively. Temporal variations in the fluxes of hydrothermal Fe indicate that there have been at least three amplified hydrothermal venting events (H1, H2, and H3) in the Tianshi field over the last 35.2 ka, in 28.6-35.2 ka BP, 22.0-27.6 ka BP, and 1.2-11.4 ka BP, respectively. Hydrothermal event H2 was driven by an increased magmatic production associated with sea level fall during the Last Glacial Maximum, while event H3 was promoted by tectonic activity associated with a rapid sea level rise. This study further verified the role of sea level change in modulating hydrothermal activity on mid-ocean ridges.