Venting of Carbon Dioxide-Rich Fluid and Hydrate Formation in Mid-Okinawa Trough Backarc Basin

Sakai, Hitoshi; Gamo, Toshitaka; Kim, E. S.; Tsutsumi, M.; Tanaka, Takeo; Ishibashi, Jun-ichiro; Wakita, Hiroshi; Yamano, Makoto; Oomori, Tamotsu

doi:10.1126/science.248.4959.1093

Cited by 291 publications

(194 citation statements)

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“…The highest CO 2 concentrations, found in the lower Cl fluids at Snowcap and Satanic Mills (Fig. 5.5b, Table 5.2), are among the highest reported to date for vent fluids (Karl et al, 1988;Butterfield et al, 1990;Sakai et al, 1990a,b;Von Damm, 1995;German and Von Damm, 2003;Lupton et al, 2006) and are comparable to those observed in black smoker fluids at the back-arc JADE site, Okinawa Trough (Sakai et al, 1990b). In addition to the higher concentrations relative to Vienna Woods, CO 2 is more 13 C-enriched at PACMANUS, with endmember δ 13 C CO2 values varying from -4.1‰ to -2.3‰ (Table 5.2).…”

Section: H 2 H 2 S Ch 4 Co and Cosupporting

confidence: 54%

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Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Reeves¹

2010

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This thesis presents the results of four discrete investigations into processes governing the organic and inorganic chemical composition of seafloor hydrothermal fluids in a variety of geologic settings. Though Chapters 2 through 5 of this thesis are disparate in focus, each represents a novel investigation aimed at furthering our understanding of subsurface geochemical processes affecting hydrothermal fluid compositions. Chapters 2 and 3 concern the abiotic (nonbiological) formation of organic compounds in high temperature vent fluids, a process which has direct implications for the emergence of life in early Earth settings and sustainment of present day microbial populations in hydrothermal environments. Chapter 2 represents an experimental investigation of methane (CH 4 ) formation under hydrothermal conditions. The overall reduction of carbon dioxide (CO 2 ) to CH 4 , previously assumed to be kinetically inhibited in the absence of mineral catalysts, is shown to proceed on timescales pertinent to crustal residence times of hydrothermal fluids. In Chapter 3, the abundance of methanethiol (CH 3 SH), considered to be a crucial precursor for the emergence of primitive chemoautotrophic life, is characterized in vent fluids from ultramafic-, basalt-and sediment-hosted hydrothermal systems. Previous assumptions that CH 3 SH forms by reduction of CO 2 are not supported by the observed distribution in natural systems. Chapter 4 investigates factors regulating the hydrogen isotope composition of hydrocarbons under hydrothermal conditions. Isotopic exchange between low molecular weight n-alkanes and water is shown to be facilitated by metastable equilibrium reactions between alkanes and their corresponding alkenes, which are feasible in natural systems. In Chapter 5, the controls on vent fluid composition in a backarc hydrothermal system are investigated. A comprehensive survey of the inorganic geochemistry of fluids from sites of hydrothermal activity in the eastern Manus Basin indicates that fluids there are influenced by input of acidic magmatic solutions at depth, and subsequently modified by variable extents of seawater entrainment and mixing-related secondary acidity production. CHAPTER 1 IntroductionSeafloor hydrothermal systems associated with the generation of oceanic crust represent a dramatic expression of heat and mass transfer from the interior of the Earth. In addition to profound effects on ocean chemistry, convective circulation of seawater through volcanically active oceanic crust leads to the formation of metal sulfide deposits. In addition, seafloor hot springs are often invoked as ideal settings from which early microbial life could have emerged.Since the initial discovery of low temperature venting at the Galápagos Spreading Center in 1977 (CORLISS et al., 1979), our understanding of the composition and diversity of hydrothermal solutions has expanded greatly. During convection through oceanic crust of basaltic composition, O 2 -replete seawater reacts with crustal rock, typically producin...

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Section: H 2 H 2 S Ch 4 Co and Cosupporting

confidence: 54%

“…Trends of increasing δ 13 C CO2 with arc proximity have been observed in other back-arc vent fluids, such as the Lau Basin (Proskurowski et al, 2006) and the Okinawa Trough/Mariana Arc (cf. Sakai et al (1990b) and Lupton et al (2006)). …”

Section: Magmatic Co 2 F and CLmentioning

confidence: 99%

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Reeves¹

2010

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“…Diffusive shimmering vents and inactive chimneys have been recognized, along the active venting, in a NE-SW direction . Emission of liquid CO 2 was identified at both extensions of the chimney line (Sakai et al 1990). At the southwestern extension of the chimney line, thick layered consolidated structure plausibly consisted of amorphous silica and native sulfur was recognized at~500 m apart from the TBS chimney.…”

Section: Jade Hydrothermal Field In the Izena Holementioning

confidence: 92%

Hydrothermal Activity in the Okinawa Trough Back-Arc Basin: Geological Background and Hydrothermal Mineralization

Ishibashi

Ikegami

Tsuji

et al. 2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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The Okinawa Trough is a back-arc basin behind the Ryukyu trench-arc system and located along the eastern margin of the Eurasian continent. Sulfide and sulfate mineralization associated with hydrothermal activity has been recognized in ten hydrothermal fields in the Okinawa Trough. Hydrothermal mineralization recognized in these fields is commonly represented by coexisting occurrence of zinc-and lead-enriched polymetallic sulfides and abundant sulfate minerals. The mineralogy and geochemical signatures present has led researchers to suggest these areas may be a modern analogue for the formation of ancient Kuroko-type volcanogenic massive sulfide (VMS) deposits. Recent seafloor drilling during IODP (Integrated Ocean Drilling Program) Expedition 331 documented the subseafloor structure of a hydrothermal system at the Iheya North Knoll. Mineral textures and hydrothermal assemblages present in the drilled cores obtained from a hydrothermal mound in the proximal area are consistent with Kuroko-type mineralization. Based on geochemical studies, the intra-field diversity of mineralization commonly recognized in the Okinawa Trough can be explained by subseafloor phase separation of the hydrothermal fluid, which reflects shallow water depth (from 700 to 1,600 m). The subseafloor phase separation may. play an important role to accumulate metal elements beneath the seafloor. Based on geophysical and geological studies, the Okinawa Trough is considered a back-arc basin in the rifting stage. Such a tectonic setting is characterized by development of normal faulting in brittle continental crust and frequent intrusion of a magma, which can be expected to provide favorable environment for development of a hydrothermal system Keywords

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“…The main difference from rocky fauna is that most sedimentary fauna are shared between methane seep sites in Sagami Bay and Nankai Trough (Watanabe et al 2010). This can be attributed to the similarity of vent fauna in the Okinawa Trough to the methane seep fauna, in addition to the high concentration of methane and CO 2 in vent fluids (Sakai et al 1990). …”

Section: Faunal Zonation In a Vent Fieldmentioning

confidence: 99%

Vent Fauna in the Okinawa Trough

Watanabe

Kojima

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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In deep-sea hydrothermal vent fields, faunal distribution is associated with geochemical environments generated by hydrothermal vent activity. The Okinawa Trough is located between the Eurasian Continent and the Ryukyu Arc, and is characterized by sedimentassociated fauna associated with vents. In this chapter, the faunal distribution in hydrothermal vent fields in the Okinawa Trough is summarized at inter-and intra-field levels, and its relationship with geochemical environments and species-specific ecologies is discussed. Although the zonation of sediment-associated fauna is not distinct, the fauna on rocky seabed can be categorized into four zones based on thermal conditions. Genetic connectivity among conspecific populations in the Okinawa Trough appears to be common; further, a few faunal groups, such as tubeworms, show connectivity to regions outside of the Okinawa Trough. The faunal composition of vent communities in the Okinawa Trough has been categorized into three groups: the Minami-Ensei Knoll, Yoron Hole, and middlesouthern Okinawa Trough. To determine more precisely the relationships between faunal composition and environmental factors in the Okinawa Trough vent fields, both generalized and vent-specific environmental factors should be measured simultaneously with quantitative faunal sampling for analyses. Keywords

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Venting of Carbon Dioxide-Rich Fluid and Hydrate Formation in Mid-Okinawa Trough Backarc Basin

Cited by 291 publications

References 9 publications

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Hydrothermal Activity in the Okinawa Trough Back-Arc Basin: Geological Background and Hydrothermal Mineralization

Vent Fauna in the Okinawa Trough

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