Chemical composition of hydrothermal fluids in the central and southern Mariana Trough backarc basin

Ishibashi, Jun-ichiro; Tsunogai, Urumu; Toki, Tomohiro; Ebina, Naoya; Gamo, Toshitaka; Sano, Yuji; Masuda, Harue; Chiba, Hitoshi

doi:10.1016/j.dsr2.2015.06.003

Cited by 24 publications

(12 citation statements)

References 47 publications

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“…Tivey et al, 2002). Ten-year results of little to no natural change in the end-member chemical composition have been documented in the Mariana back-arc basin (Alice Springs, 32 mm·year −1 ; Beaulieu, 2015;Ishibashi et al, 2015). In the present study, at least some stability in the endmember fluid chemical composition is indirectly evident from observations of consistent edifice deposition (hydrothermal fluid precipitate) and the realized distributions of vent-associated fauna.…”

Section: Ventingmentioning

confidence: 53%

Long-Term Stability of Back-Arc Basin Hydrothermal Vents

Preez

Fisher

2018

Front. Mar. Sci.

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Since the discovery of hydrothermal vents 40-years ago, long-term time-series have focused on mid-ocean ridge systems. Based on these studies, hydrothermal vents are widely considered to be dynamic, ephemeral habitats. Under this premise, national, and international regulatory bodies are currently planning for the commercial mining of polymetallic sulfide deposits from hydrothermal vents. However, here we provide evidence of longevity and habitat stability that does not align with historic generalizations. Over a 10-year time-series focused on the back-arc basin systems off the west coast of the Kingdom of Tonga (South Pacific), we find the hydrothermal vents are remarkably stable habitats. Using high-resolution photo mosaics and spatially explicit in situ measurements to document natural changes of five hydrothermal vent edifices, we discovered striking stability in the vent structures themselves, as well as in the composition and coverage of the vent-associated species, with some evidence of microdistribution permanence. These findings challenge the way we think about hydrothermal vent ecosystems and their vulnerability and resilience to deep-sea mining activities.

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Section: Ventingmentioning

confidence: 53%

Long-Term Stability of Back-Arc Basin Hydrothermal Vents

Preez

Fisher

2018

Front. Mar. Sci.

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“…On segment 18.2°N, 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 a). All three were apparently “high‐temperature” in 1987 (Campbell et al, ; Hessler & Lonsdale, ), and Ishibashi et al () reported temperatures >267°C at Alice Springs/Illium in 1996. However, all authors note that the observed discharging fluids were “clear,” not black smoke.…”

Section: Distribution Of Vent Sites On the Mariana Back‐arc Spreadingmentioning

confidence: 99%

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

Baker

Walker

Chadwick

et al. 2017

Geochem Geophys Geosyst

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Back‐arc spreading centers (BASCs) form a distinct class of ocean spreading ridges distinguished by steep along‐axis gradients in spreading rate and by additional magma supplied through subduction. These characteristics can affect the population and distribution of hydrothermal activity on BASCs compared to mid‐ocean ridges (MORs). To investigate this hypothesis, we comprehensively explored 600 km of the southern half of the Mariana BASC. We used water column mapping and seafloor imaging to identify 19 active vent sites, an increase of 13 over the current listing in the InterRidge Database (IRDB), on the bathymetric highs of 7 of the 11 segments. We identified both high and low (i.e., characterized by a weak or negligible particle plume) temperature discharge occurring on segment types spanning dominantly magmatic to dominantly tectonic. Active sites are concentrated on the two southernmost segments, where distance to the adjacent arc is shortest (<40 km), spreading rate is highest (>48 mm/yr), and tectonic extension is pervasive. Re‐examination of hydrothermal data from other BASCs supports the generalization that hydrothermal site density increases on segments <90 km from an adjacent arc. Although exploration quality varies greatly among BASCs, present data suggest that, for a given spreading rate, the mean spatial density of hydrothermal activity varies little between MORs and BASCs. The present global database, however, may be misleading. On both BASCs and MORs, the spatial density of hydrothermal sites mapped by high‐quality water‐column surveys is 2–7 times greater than predicted by the existing IRDB trend of site density versus spreading rate.

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“…The Alice Springs site is on the flank of an axial volcano in the central part of the Mariana Trough, and the Forecast Vent site, at which the hydrothermal fluid temperature is relatively low (∼202°C), is at the summit of a seamount at the southern end of the trough (Figure d). Enrichment of the fluids in CO 2 gas has been observed at both sites, suggesting an effect of subducting slab materials below the Mariana Trough [ Gamo et al ., ; Ishibashi et al ., ].…”

Section: Geological Settingsmentioning

confidence: 99%

Lithium isotopic systematics of submarine vent fluids from arc and back‐arc hydrothermal systems in the western Pacific

Araoka

Nishio

Gamo

et al. 2016

Geochem Geophys Geosyst

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The Li concentration and isotopic composition (d 7 Li) in submarine vent fluids are important for oceanic Li budget and potentially useful for investigating hydrothermal systems deep under the seafloor because hydrothermal vent fluids are highly enriched in Li relative to seawater. Although Li isotopic geochemistry has been studied at mid-ocean-ridge (MOR) hydrothermal sites, in arc and back-arc settings Li isotopic composition has not been systematically investigated. Here we determined the d 7 Li and 87 Sr/ 86 Sr values of 11 end-member fluids from 5 arc and back-arc hydrothermal systems in the western Pacific and examined Li behavior during high-temperature water-rock interactions in different geological settings. In sediment-starved hydrothermal systems (Manus Basin, Izu-Bonin Arc, Mariana Trough, and North Fiji Basin), the Li concentrations (0.23-1.30 mmol/kg) and d 7 Li values (14.3& to 17.2&) of the end-member fluids are explained mainly by dissolution-precipitation model during high-temperature seawater-rock interactions at steady state. Low Li concentrations are attributable to temperature-related apportioning of Li in rock into the fluid phase and phase separation process. Small variation in Li among MOR sites is probably caused by low-temperature alteration process by diffusive hydrothermal fluids under the seafloor. In contrast, the highest Li concentrations (3.40-5.98 mmol/kg) and lowest d 7 Li values (11.6& to 12.4&) of end-member fluids from the Okinawa Trough demonstrate that the Li is predominantly derived from marine sediments. The variation of Li in sediment-hosted sites can be explained by the differences in degree of hydrothermal fluid-sediment interactions associated with the thickness of the marine sediment overlying these hydrothermal sites. Key Points:First Li isotopic report on submarine vent fluids from arc and back-arc hydrothermal systems Li in vent fluids can be explained mainly by dissolution-precipitation model during seawater-rock and seawater-sediment interactions Variation in Li due to diffusive hydrothermal fluid and the degree of hydrothermal fluid-sediment interaction

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Chemical composition of hydrothermal fluids in the central and southern Mariana Trough backarc basin

Cited by 24 publications

References 47 publications

Long-Term Stability of Back-Arc Basin Hydrothermal Vents

Long-Term Stability of Back-Arc Basin Hydrothermal Vents

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

Lithium isotopic systematics of submarine vent fluids from arc and back‐arc hydrothermal systems in the western Pacific

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