Geochemistry and Mineralogy of Gold-Rich Hydrothermal Precipitates From the Eastern Manus Basin, Papua New Guinea

Moss, R.W.; Scott, S. D.

doi:10.2113/gscanmin.39.4.957

Cited by 72 publications

(55 citation statements)

References 41 publications

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“…During the last two decades, areas of hydrothermal activity have been discovered in the Eastern Manus volcanic zone (Fig. 1), including the DESMOS caldera, the SuSu Knolls area, and the PACMANUS and Northeast Pual sites located on Pual Ridge (Binns and Scott, 1993;Gamo et al, 1993Gamo et al, , 1997Gamo et al, , 2006Auzende et al, 1997Auzende et al, , 2000Binns et al, 1997;Gena et al, 2001Gena et al, , 2006Moss and Scott, 2001;Tivey et al, 2006;Hrischeva et al, 2007;Craddock et al, 2010;Reeves et al, 2011).…”

Section: Geologic Settingmentioning

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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Section: Geologic Settingmentioning

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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“…At the Brothers volcano in the Kermadec island arc, located at a water depth of 1600 m, active black smokers and massive sulfide deposits are present on the caldera wall, as are sulfur-rich fumaroles and very-low-pH vent fluids (de Ronde et al, 2005). At the PACMANUS vent area on Pual Ridge in the eastern Manus Basin, sulfide deposits are enriched in Au, Ag, Pb, As, Sb, and Ba relative to mid-ocean ridge deposits (Scott and Binns, 1995;Moss and Scott, 2001;Binns et al, 2002). At the DESMOS caldera, farther east in the Manus Basin, advanced argillic alteration of the lavas is observed (i.e., alteration of igneous rocks to alunite (KAl 3 (SO 4 ) 2 (OH) 6 ), aluminum-rich clay, and quartz ± pyrite), proposed to result from alteration by acidsulfate fluids; vent fluids with extremely low pH (as low as 0.87) are also present (Gamo et al, 1997;Seewald et al, 2006).…”

Section: B Y M a R G A R E T K I N G S T O N T I V E Ymentioning

confidence: 99%

Generation of Seafloor Hydrothermal Vent Fluids and Associated Mineral Deposits

Tivey¹

2007

Oceanog.

341

211

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“…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%

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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Geochemistry and Mineralogy of Gold-Rich Hydrothermal Precipitates From the Eastern Manus Basin, Papua New Guinea

Cited by 72 publications

References 41 publications

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

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

Generation of Seafloor Hydrothermal Vent Fluids and Associated Mineral Deposits

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

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