Unique chemistry of the hydrothermal solution in the mid‐Okinawa Trough Backarc Basin

Sakai, Hitoshi; Gamo, Toshitaka; Kim, E. ‐S; Shitashima, Kiminori; Yanagisawa, Fumitaka; Tsutsumi, M.; Ishibashi, Jun Ichiro; Sano, Yuji; Wakita, Hiroshi; Tanaka, Takeo; Matsumoto, Takumi; Naganuma, Takeshi; Mitsuzawa, K.

doi:10.1029/gl017i012p02133

Cited by 117 publications

(82 citation statements)

References 12 publications

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“…The Okinawa Trough is a backarc basin in the rifting to spreading stage characterized by the development of normal faulting of transitional crust (atypical crust with mantle-derived material) and frequent magma intrusions, which provides a favorable geological environment for the development of seafloor hydrothermal systems [8,41,42]. As of 2016, there were at least 15 deep-sea hydrothermal fields reported in the Okinawa Trough based on the InterRidge data base, including the Minami-Ensei (e.g., [10]), Iheya North [9,11,43], Jade [7,13], Hakurei [8], Hatoma [44][45][46], Yonaguni Knoll IV [12,14,47], and Tangyin hydrothermal fields [48,49]. The Iheya North knoll hydrothermal field (27 ∘ 47.2 N, 126 ∘ 53.9 E) is located at a water depth about 1,000 m along the eastern slope of a small knoll, part of the Iheya North knoll volcanic complex ( Figure 1; [8]).…”

Section: Geological Settingmentioning

confidence: 99%

“…Clear hydrothermal fluid with a temperature of up to 220 ∘ C was found to be discharging from 1 to 2 m high hydrothermal mounds and fissures (e.g., [8,13]). The hydrothermal fluids from the Clam hydrothermal field are characterized by anomalously high alkalinity (2.5-10.3 mmol l −1 ), NH 4 + (0.6-4.4 mmol kg −1 ), and CO 2 / 3 He ratios (e.g., [6,7,13,53]). Based on a temperature of 220 ∘ C, the end-member fluid is assumed to contain about 20 mmol kg −1 Mg 2+ and 10 mmol kg −1 SO 4 2− [6,53].…”

Section: Geological Settingmentioning

confidence: 99%

“…In the Okinawa Trough, the vent fluid chemistry of seafloor hydrothermal systems has been characterized by enrichment in CO 2 , CH 4 , NH 4 + , and K + compared with those in typical sediment-free midocean ridge (MOR) hydrothermal fluids (e.g., [6][7][8][9][10][11][12][13][14]). The high K + content (6.9-79.2 mmol kg −1 ) in the estimated source fluid is typical for the Iheya North knoll hydrothermal field due to hydrothermal reaction with K-enriched felsic rocks.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

et al. 2018

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Studies of the major components of hydrothermal plumes in seafloor hydrothermal fields are critical for an improved understanding of biogeochemical cycles and the large-scale distribution of elements in the submarine environment. The composition of major components in hydrothermal plume water column samples from 25 stations has been investigated in the middle and southern Okinawa Trough. The physical and chemical properties of hydrothermal plume water in the Okinawa Trough have been affected by input of the Kuroshio current, and its influence on hydrothermal plume water from the southern Okinawa Trough to the middle Okinawa Trough is reduced. The anomalous layers of seawater in the hydrothermal plume water columns have higher K + , Ca 2+ , Mn 2+ , B 3+ , Ca 2+ /SO 4 2− , and Mn 2+ /Mg 2+ ratios and higher optical anomalies than other layers. The Mg 2+ , SO 4 2− , Mg 2+ /Ca 2+ , and SO 4 2− /Mn 2+ ratios of the anomalous layers are lower than other layers in the hydrothermal plume water columns and are consistent with concentrations in hydrothermal vent fluids in the Okinawa Trough. This suggests that the chemical variations of hydrothermal plumes in the Tangyin hydrothermal field, like other hydrothermal fields, result in the discharge of high K + , Ca 2+ , and B 3+ and low Mg 2+ and SO 4 2− fluid. Furthermore, element ratios (e.g., Sr 2+ /Ca 2+ , Ca 2+ /Cl − ) in hydrothermal plume water columns were found to be similar to those in average seawater, indicating that Sr 2+ /Ca 2+ and Ca 2+ /Cl − ratios of hydrothermal plumes might be useful proxies for chemical properties of seawater. The hydrothermal K + , Ca 2+ , Mn 2+ , and B 3+ flux to seawater in the Okinawa Trough is about 2.62-873, 1.04-326, 1.30-76.4, and 0.293-34.7 × 10 6 kg per year, respectively. The heat flux is about 0.159-1,973 × 10 5 W, which means that roughly 0.0006% of ocean heat is supplied by seafloor hydrothermal plumes in the Okinawa Trough.

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Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

et al. 2018

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“…Thermal breakdown of complex hydrocarbons, typically derived from organic matter in sediments, has been documented on sedimented mid-ocean ridges such as in Guaymas Basin (Simoneit, 1983) and Middle Valley on the Juan de Fuca Ridge (Davis et al, 1993). It has also been invoked to explain high CH, concentrations at an unsedimented ridge, the Endeavour segment of the Juan de Fuca Ridge ) and at an intracontinental back-arc spreading axis in the Okinawa Trough (Sakai et al, 1990;Gamo et al, 1991). Biological production by bacteria commonly occurs at Galapagos-type low-temperature vents (Lilley et al, 1983;Jannasch and Mottl, 1985 ), and it may occur at higher temperatures as well (Baross et al, 1982).…”

Section: Variable Cand/mn and Diverse Origins Of Chmentioning

confidence: 99%

“…Possible causes of high CH4 relative to Mn at these sites include ( 1) thermal decomposition of sedimentary organic matter at the Endeavour , Guaymas Basin (Simoneit, 1983)) and Okinawa Trough (Sakai et al, 1990;Gamo et al, 1991) sites; (2) active volcanism at the eruptive site on the EPR at 9"39 to 53 'N (this paper) and on Teahitia and Macdonald hotspot seamounts (Stuben et al, 1992), possibly accompanied by magma degassing; and (3 ) serpentinization reactions on the Mid-Atlantic Ridge near 15"05 ' N (Charlou et al, 1991 b) . Among back-arc spreading axes, the Okinawa Trough and the North Fiji Basin fall into this high-C&/Mn group, the former because it is intracontinental and thus contains organic-rich sediment (lshibashi et al, 1988), and the latter because its vents are vapor rich due to phase separation (lshibashi et al, 1994).…”

Section: Variable Cand/mn and Diverse Origins Of Chmentioning

confidence: 99%

Manganese and methane in hydrothermal plumes along the East Pacific Rise, 8°40′ to 11°50′N

Mottl

Sansone

Wheat

et al. 1995

Geochimica et Cosmochimica Acta

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Abstract-In November, 1991, we surveyed the water column for hydrothermal plumes along 350 km of the East Pacific Rise axis from 8'40 ' to 1 lo50 ' N, using a combination of physical and chemical measurements. Our survey included the two major ridge segments north and south of the Clipperton Transform Fault at about lO"lO'N, both limbs of the overlapping spreading centers (OSC's) at 9"03 'N and 1 lo45 'N, and a 30&m section of the next ridge segment to the south. We found vigorous plumes along most of this ridge axis, in keeping with its magmatically robust cross-section, axial summit caldera, and shallow, magma-related seismic reflector. These plumes were detectable by both physical (temperature and light attenuation) and chemical (dissolved Mn and CR) measurements, although the chemical measurements were more sensitive. The least active sections were the southern third of the northern segment from lo"20 to 52'N and the OSCs, especially the OSC at ll"45'N. Plumes there had weak Mn and CH4 signals and were barely detectable by physical methods. These axial sections were the only ones surveyed that lie deeper than 2600 m and appear to be magma starved. The most active sections on the northern segment gave stronger signals for Mn and temperature than for CH, and light attenuation, whereas the opposite was true on the southern segment, which was the site of a volcanic eruption at 9"45-52'N only seven months prior to our cruise. On the northern segment the four physical and chemical plume tracers correlated positively and linearly with one another, suggesting that the segment was fed by relatively uniform endmember fluids with a mean C&Nn molar ratio of 0.075. The southernmost section surveyed, from 8"42' to 9'08 'N, closely resembled the northern segment. The rest of the southern segment fell into three sections with different CHJMn ratios: 9"39 to 53'N with CHJMn as high as 10, 9'08 to 39'N with CHJMn of 0.51, and 9"53 ' to lO"07'N with CH,/Mn of 0.85. The section with the highest CHJMn was the site of the volcanic eruption, which produced high-temperature, low-salinity, gas-rich vent fluids carrying abundant bacterial Darticles. The high CH, concentradons are clearly associated with the volcanic eruption, but the origin of the CH, is uncle&.

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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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Unique chemistry of the hydrothermal solution in the mid‐Okinawa Trough Backarc Basin

Cited by 117 publications

References 12 publications

Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

Manganese and methane in hydrothermal plumes along the East Pacific Rise, 8°40′ to 11°50′N

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

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