Helium isotopic composition of hydrothermal fluids from the Manus back-arc Basin, Papua New Guinea

Fourré, Élise; Jean‐Baptiste, Philippe; Charlou, Jean-Luc; Donval, Jean-Pierre; Ishibashi, J.

doi:10.2343/geochemj.40.245

Cited by 17 publications

(8 citation statements)

References 21 publications

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“…Despite being located 100-150m apart, the three fluids exhibited a narrow range of temperatures (273-285°C) and compositions (Tables 5.1 and 5.2) suggesting that the Vienna Woods field is fed by a common source fluid. Measured temperatures, pH (25C) and endmember fluid composition have remained relatively constant since previous expeditions in 1990 and 1995 (Lisitsyn et al, 1993;Auzende et al, 1996;Gamo et al, 1997;Douville et al, 1999;Fourre et al, 2006). In general, almost all aspects of the chemistry of fluids venting at Vienna Woods are similar to observations from basalt-hosted hydrothermal systems in MOR settings (Von Damm, 1995;German and Von Damm, 2003).…”

Section: Temperaturesupporting

confidence: 65%

“…As stated previously, Mn abundances in Vienna Woods fluids only suggest temperatures near 350°C and so it is possible that the high Cl endmembers do not reflect active phase separation at depth in 2006, but rather entrainment/depletion of residual brines formed during previous phase separation events (Shanks and Seyfried, 1987;Von Damm and Bischoff, 1987;Von Damm, 1988;Butterfield et al, 1997;Schoofs and Hansen, 2000;Von Damm et al, 2005). Brine entrainment would be consistent with the chronic venting of Cl-rich fluids at Vienna Woods since 1990 (Lisitsyn et al, 1993;Auzende et al, 1996;Gamo et al, 1997;Douville et al, 1999;Fourre et al, 2006) and the apparent absence of any Cl-depleted conjugate fluids.…”

Section: Phase Separation and CL Variabilitymentioning

confidence: 81%

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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: Temperaturesupporting

confidence: 65%

Section: Phase Separation and CL Variabilitymentioning

confidence: 81%

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

Reeves¹

2010

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“…EMZV in (a) indicates the location of the Eastern Manus Volcanic Zone. Douville et al, 1999a,b;Gena et al, 2001Gena et al, , 2006Fourre et al, 2006). Fluids samples were collected during this study at two sites (D1 and D2; Fig.…”

Section: Desmos Calderamentioning

confidence: 99%

Submarine venting of magmatic volatiles in the Eastern Manus Basin, Papua New Guinea

Seewald

Reeves

Bach

et al. 2015

Geochimica et Cosmochimica Acta

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The SuSu Knolls and DESMOS hydrothermal fields are located in the back-arc extensional transform zone of the Eastern Manus Basin. In 2006, highly acidic and RSO 4 -rich vent fluids were collected at both sites and analyzed for the chemical and isotopic composition of major and trace species. Fluids exiting the seafloor have measured temperatures from 48 to 215°C and are milky white in appearance due to precipitation of elemental S 0 . Vent fluid concentrations of Na, K, and Mg are depleted by as much as 30% relative to seawater, but have the same relative abundance. In contrast, the fluids are highly enriched in dissolved RCO 2 , Cl, SiO 2(aq) , Fe, and Al relative to seawater. Measured pH (25°C) ranged from 0.95 to 1.87 and aqueous RSO 4 ranged from 35 to 135 mmol/kg. The chemical and isotopic composition points to formation via subsurface mixing of seawater with a Na-, K-, Mg-, and Ca-free, volatile-rich magmatic fluid exsolved from subsurface magma bodies during a process analogous to subaerial fumarole discharge. Estimates of the magmatic end-member composition indicate a fluid phase where H 2 O > SO 2 > CO 2 % Cl > F. The hydrogen and oxygen isotopic composition of H 2 O and carbon isotopic composition of RCO 2 in the vent fluids strongly suggest a contribution of slab-derived H 2 O and CO 2 to melts generated in the mantle beneath the Eastern Manus volcanic zone. Abundant magmatically-derived SO 2 undergoes disproportionation during cooling in upflow zones and contributes abundant acidity, SO 4 2À , and S 0 to the venting fluids. Interaction of these highly acidic fluids with highly altered mineral assemblages in the upflow zone are responsible for extensive aqueous mobilization of SiO 2(aq), Fe, and Al. Temporal variability in the speciation and abundance of aqueous S species between 1995 and 2006 at the DESMOS vent field suggests an increase in the relative abundance of SO 2 in the magmatic end-member that has mixed with seawater in the subsurface. Results of this study constrain processes responsible for the formation of hot-spring fluids in magmatically active back-arc environments and the resulting chemical exchange between the lithosphere and water column.

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“…5; we have not plotted the Alice Springs field because we lack data for He . Those reported for the Valu Fa Ridge in the Lau Basin (Takai et al, 2008), the Manus Spreading Center and Pual Ridge in the Manus Basin (Fourre et al, 2006), the White Lady site in the North Fiji Basin (Ishibashi et al, 1994b), Suiyo Seamount in the Izu-Bonin Arc (Tsunogai et al, 1994), northwest caldera sites in Brothers Seamount in the Kermadec Arc (de Ronde et al, 2011), and for hydrothermal fields in the North and South-East Pacific Rise (Merlivat et al, 1987;Jean-Baptiste et al, 1997) are also shown.…”

Section: Gas Geochemistrymentioning

confidence: 86%

“…4. In the same figure, the ratios from other arc-backarc systems in the western Pacific, the Valu Fa Ridge (VFR) in the Lau Basin (Takai et al, 2008), the Pual Ridge and Manus Spreading Center in the Manus Basin (Fourre et al, 2006), the White Lady site in the North Fiji Basin (Ishibashi et al, 1994b), Suiyo Seamount in the Izu-Bonin Arc (Tsunogai et al, 1994) (Sano et al, 1998). These ratios are within the typical range of MORB ( 3 He/ 4 He ¼8 71R/R A ) and are similar to those of the EPR hydrothermal fluids (Fig.…”

Section: Gas Geochemistrymentioning

confidence: 91%

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

Ishibashi

Tsunogai

Toki

et al. 2015

Deep Sea Research Part II: Topical Studies in Oceanography

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Helium isotopic composition of hydrothermal fluids from the Manus back-arc Basin, Papua New Guinea

Cited by 17 publications

References 21 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

Submarine venting of magmatic volatiles in the Eastern Manus Basin, Papua New Guinea

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

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