Acidic and sulfate-rich hydrothermal fluids from the Manus back-arc basin, Papua New Guinea

Gamo, Toshitaka; Okamura, Kei; Charlou, Jean-Luc; Urabe, Tetsuro; Auzende, Jean-Marie; Ishibashi, Jun-ichiro; Shitashima, Kiminori; Chiba, Hitoshi; Cruise, Shipboard Scientific Party of the ManusFlux

doi:10.1130/0091-7613(1997)025<0139:aasrhf>2.3.co;2

Cited by 184 publications

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“…Several outcrops of heavily bleached rocks cemented with native sulfur were observed near active vents, presumably reflecting advanced argillic alteration by acid-sulfate type fluids (Brimhall and Ghiorso, 1983;Gena et al, 2001;Binns et al, 2007). However, no 'white smoker activity' similar to the DESMOS caldera site (Gamo et al, 1997;Gamo et al, 2006) has been observed anywhere on Pual Ridge. A new site, Fenway, was discovered ~200m south of Satanic Mills at 1710m depth during this expedition ( Fig.…”

Section: Pacmanus and Northeast Pualmentioning

confidence: 98%

“…This assumption is based on experimental evidence for near-quantitative removal of Mg from seawater during hydrothermal interactions with basalt, andesite, and rhyolite at reaction zone conditions typical of seafloor hydrothermal systems Seyfried and Bischoff, 1981;Hajash and Chandler, 1982;Shiraki et al, 1987;Ogawa et al, 2005). It has been suggested that the highly acidic nature of many backarc basin fluids may reverse Mg uptake reactions thereby invalidating the assumption that a near-zero Mg composition exists prior to seawater admixing (Gamo et al, 1997;Douville et al, 1999;Butterfield et al, 2003). For the purposes of our interpretations, however, calculated 'endmember' compositions are assumed to contain no Mg as per convention.…”

Section: Calculation Of Endmember Compositionsmentioning

confidence: 99%

“…Discharge of magmatic fluids directly into the water column has been observed above submarine arc volcanoes Nakagawa et al, 2006;Lupton et al, 2008) and seamounts (Cheminée et al, 1991;Gamo et al, 1993;de Ronde et al, 2005;Resing et al, 2007), and contributions of magmatic acid-volatile species and water to hydrothermal fluids have been reported in a few locations (Sedwick et al, 1992;McMurtry et al, 1993;Gamo et al, 1997;Zengqian et al, 2005;Nakagawa et al, 2006). In general, however, active magmatichydrothermal systems hosted in felsic crust have been historically under-sampled despite the prevalence of hydrothermal activity associated with back-arc volcanism in the western Pacific (Ishibashi and Urabe, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…Several large areas of hydrothermal activity have been discovered in the EMVZ (Fig. 5.1a) in the last two decades, including the DESMOS caldera (Gamo et al, 1993;Gamo et al, 1997), SuSu Knolls (Binns et al, 1997;Moss and Scott, 2001;Tivey et al, 2006;Hrischeva et al, 2007) and PACMANUS vent fields (Binns and Scott, 1993).…”

Section: Geological Settingmentioning

confidence: 99%

“…In contrast to MOR settings, where CO 2 is the dominant volatile degassed, the exsolution of large quantities of H 2 O and CO 2 from water-rich silicic magmas can be accompanied by acid-volatile species such as SO 2 , HCl and HF. Subsequent entrainment of water-rich magmatic fluids into existing hydrothermal circulation cells could substantially lower pH, thereby influencing the transport of dissolved metals and styles of crustal alteration (Gamo et al, 1997;Gena et al, 2001;Gamo et al, 2006;. Moreover, magmatic fluids have long been proposed as an additional source of economically important metals (i.e.…”

Section: Introductionmentioning

confidence: 99%

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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: Pacmanus and Northeast Pualmentioning

confidence: 98%

Section: Calculation Of Endmember Compositionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Reeves¹

2010

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Hydrothermal Venting at Hinepuia Submarine Volcano, Kermadec Arc: Understanding Magmatic‐Hydrothermal Fluid Chemistry

Stucker

Walker

Ronde

et al. 2017

Geochem Geophys Geosyst

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The Hinepuia volcanic center is made up of two distinct edifices aligned northwest to southeast, with an active cone complex in the SE. Hinepuia is one of several active volcanoes in the northern segment of the Kermadec arc. Regional magnetic data show no evidence for large-scale hydrothermal alteration at Hinepuia, yet plume data confirm present-day hydrothermal discharge, suggesting that the hydrothermal system may be too young to have altered the host rocks with respect to measurable changes in magnetic signal. Gravity data are consistent with crustal thinning and shallow mantle under the volcanic center. Following the discovery of hydrothermal plumes over Hinepuia, the submersible Shinkai 6500 was used to explore the SE cone and sample hydrothermal fluids. The chemistry of hydrothermal fluids from submarine arc and backarc volcanoes is typically dominated by water-rock interactions and/or magmatic degassing. Chemical analyses of vent fluids show that Hinepuia does not quite fit either traditional model. Moreover, the Hinepuia samples fall between those typically ascribed to both end-member fluid types when plotted on a K-Mg-SO 4 ternary diagram. Due to evidence of strong degassing, abundant native sulfur deposition, and H 2 S presence, the vent sampled at Hinepuia is ultimately classified as a magmatic-hydrothermal system with a water-rock influence. This vent is releasing water vapor and magmatic volatiles with a notable lack of salinity due to subcritical boiling and phase separation. Magmatic-hydrothermal fluid chemistry appears to be controlled by a combination of gas flux, phase separation processes, and volcano evolution and/or distance from the magma source.

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Geochemical observations within the water column at the CO₂‐rich hydrothermal systems Hatoma Knoll and Yonaguni Knoll IV, in the southern Okinawa Trough

et al. 2016

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The Okinawa Trough is one of three known hydrothermal sites worldwide where liquid carbon dioxide is emitted from the seafloor into the water column. In March 2008, investigations were performed at two active areas, Yonaguni Knoll IV and Hatoma Knoll, in order to identify impacts of hydrothermal venting on the water column chemistry. Vertical profiles of pH and redox potential (Eh) were recorded and discrete water samples were taken for the analysis of total carbon dioxide (CT) and helium (3He, 4He). Anomalies with respect to reference stations (ΔCT, ΔpH) and 3He with respect to saturation with the atmosphere (3Heexcess) were used to characterize the impact of hydrothermal vents. These data indicate that the flux of CO2 into the water column is dominated by hot hydrothermal CO2‐rich vents located in close proximity to the liquid CO2 emission sites. Bubbles and droplets sampled at the cold gas outlets at Hatoma Knoll differed considerably from the water column regarding CO2/3He ratios, and thus, provide additional evidence that cold liquid phase CO2 is of minor importance for the total CO2 flux at both hydrothermal systems. Although hydrothermal vents at back‐arc basins are known to emit large amounts of acids other than CO2, the correlation between ΔpH and ΔCT at both research areas clearly suggests that the observed pH reduction is mainly caused by the addition of CO2. Deviating ΔCT/3He and ΔCT/ΔpH ratios and the prevailing water currents indicate a yet undiscovered vent site at the flank of a seamount in the northeast.

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Acidic and sulfate-rich hydrothermal fluids from the Manus back-arc basin, Papua New Guinea

Cited by 184 publications

References 0 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 Venting at Hinepuia Submarine Volcano, Kermadec Arc: Understanding Magmatic‐Hydrothermal Fluid Chemistry

Geochemical observations within the water column at the CO₂‐rich hydrothermal systems Hatoma Knoll and Yonaguni Knoll IV, in the southern Okinawa Trough

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Acidic and sulfate-rich hydrothermal fluids from the Manus back-arc basin, Papua New Guinea

Cited by 184 publications

References 0 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 Venting at Hinepuia Submarine Volcano, Kermadec Arc: Understanding Magmatic‐Hydrothermal Fluid Chemistry

Geochemical observations within the water column at the CO2‐rich hydrothermal systems Hatoma Knoll and Yonaguni Knoll IV, in the southern Okinawa Trough

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Geochemical observations within the water column at the CO₂‐rich hydrothermal systems Hatoma Knoll and Yonaguni Knoll IV, in the southern Okinawa Trough