Chemical and Isotopic Compositions of Hydrothermal Fluids at Snail, Archaean, Pika, and Urashima Sites in the Southern Mariana Trough

Abstract

Hydrothermal fluids were collected from five hydrothermal fields around the Southern Mariana Trough backarc spreading center for chemical and isotopic analyses. Yamanaka site was interpreted as inactive, so we present results from Snail, Archaean, Pika and Urashima sites. The slightly low pH and negative alkalinity suggests a little bit input of magmatic volatiles, supported by high CO 2 concentrations. Consequently low pH would lead to the hydrothermal fluids rich in Fe compared to the MOR hydrothermal fluids. Keywords

The Effect of Arc Proximity on Hydrothermal Activity Along Spreading Centers: New Evidence From the Mariana Back Arc (12.7°N–18.3°N)

“…The highest Δ E and ΔNTU plumes were found at the latitude of the Pika/Urashima site (12.939°N), whereas we detected only a weak ΔNTU plume at the Snail site (12.953°N), a plume that may have originated elsewhere given the lack of a Δ E signal. This change is consistent with the precipitous decline in vent fluid temperature documented between May 2003 and March 2004 (Ishibashi et al, ) and continuing into 2012 when ROV measurements found 45°C fluids discharging from Snail (Toki et al, ). However, temperatures at Snail rebounded to at least 190°C in 2014 (https://www.pmel.noaa.gov/eoi/marianas/SRoF-Ironman-2014-CruiseReport-withdivelogs.pdf).…”

“…On segment 18.28N, three active sites (Central Trough, Burke, and Alice Springs/Ilium) were discovered during Alvin dives in 1987, close to the peaks of two bathymetric highs along this segment (Figure 8a). All three were apparently ''high-temperature'' in 1987 (Campbell et al, 1987;Hessler & Lonsdale, 1991), and Ishibashi et al (2015) reported temperatures >2678C at Alice Springs/Illium in 1996. However, all authors note that the observed discharging fluids were ''clear,'' not black smoke.…”

Endemicity of the cosmopolitan mesophilic chemolithoautotroph Sulfurimonas at deep-sea hydrothermal vents

“…To consider the physicochemical conditions of the Sulfurimonas populations' habitats, the physical and chemical properties of the endmember hydrothermal fluids at each of the hydrothermal fields/sites were analysed. The chemical compositions of the SMT vent fluids were analysed as described previously (Toki et al, 2015). Concentrations of H 2 (Archaean, Pika and Urashima sites), CO 2 and CH 4 (Archaean site) in the endmember fluids were calculated by extrapolation of Mg = 0 using a linear regression of the water chemistry data.…”

Hydrogenimonas urashimensis sp. nov., a hydrogen-oxidizing chemolithoautotroph isolated from a deep-sea hydrothermal vent in the Southern Mariana Trough

“…The chimney structure was taken with R/V Yokosuka and DSV Shinkai 6500 from the Baltan chimney at the Urashima site (12º55.3'N, 143º38.9'E) in the Southern Mariana Trough in 2010. The physical and chemical characterization of the vent emissions has been described elsewhere [10]. After retrieval on board, the sample was anaerobically suspended in 20 ml sterilized MJ synthetic sea water [14,15] containing 0.05% (w/v) sodium sulfide in a 100 ml glass bottle (Schott Glaswerke) tightly sealed with a butyl-rubber cap under a gas phase of 100% N2 (0.1 MPa).…”

“…The Southern Mariana Trough is a spreading back-arc basin, where geochemically diverse hydrothermal sites have been discovered [10]. The geochemical diversity would provide diverse habitats and a great metabolic potential of microbial communities [11].…”