The role of magmas in the formation of hydrothermal ore deposits

Hedenquist, Jeffrey W.; Lowenstern, Jacob B.

doi:10.1038/370519a0

Cited by 1,538 publications

(757 citation statements)

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“…Though Cl contents were highly variable between samples at F3 with similar Mg (517 -589mmol/kg) due to the vigorously boiling nature of the fluid, using the endmember Cl value (562mmol/kg) the fluid approximates a ~3.3 wt.% NaCl equivalent solution. Endmember δD H2O and δ 18 O H2O values from Vienna Woods and PACMANUS vent fields, with axes expanded to show compositions of mantle-derived water (MDW; Taylor, 1979b;Ohmoto, 1986) and subduction-related volcanic vapors (SRVV; Giggenbach, 1992;Hedenquist and Lowenstern, 1994). For clarity, the inset shows the data at a larger scale and 1s analytical errors.…”

Section: Resultsmentioning

confidence: 99%

“…The isotopic signature of 'juvenile' or mantle-derived magmatic water is estimated to have a narrow range of δD H2O (-65±20‰) and δ 18 O H2O (+6±1‰), (Taylor, 1979b;Ohmoto, 1986). In contrast, waters degassed from silicic arc magmas (subduction-related volcanic vapors, SRVV) may have much higher δD H2O (-10 to -30‰) and δ 18 O H2O (+6 to +10‰) values (Giggenbach, 1992;Hedenquist and Lowenstern, 1994). Degassing-related fractionation and slab-derived seawater inputs can both increase the δD H2O value of magmatic waters at convergent margins Giggenbach, 1992;Taylor, 1997;Pineau et al, 1998;Shaw et al, 2008).…”

Section: Isotopic Evidence For Magmatic H 2 Omentioning

confidence: 99%

“…While it is impossible to accurately constrain the isotopic composition of magmatic water added, the array of A crude estimate of the minimum quantity of magmatic H 2 O added to circulating fluids can be constrained by simple hydrogen isotope mass balance. For this calculation we assume that the effects of phase separation on δD H2O are negligible, magmatic H 2 O at all PACMANUS areas have a uniform δD H2O of -30‰ (the lower limit of SRVV compositions (Giggenbach, 1992;Hedenquist and Lowenstern, 1994)) and the circulating fluids into which magmatic waters are entrained have δD H2O values similar to Vienna Woods fluids (+2.4‰) due to prior water/rock reaction. With these assumptions in mind, a 1wt% magmatic H 2 O fraction is required to produce the composition observed in Roman Ruins fluid RMR1 (the highest δD H2O value in Fig.…”

Section: Isotopic Evidence For Magmatic H 2 Omentioning

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: Resultsmentioning

confidence: 99%

Section: Isotopic Evidence For Magmatic H 2 Omentioning

confidence: 99%

Section: Isotopic Evidence For Magmatic H 2 Omentioning

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 is evident from the composition of fluid inclusions trapped in phenocrysts (Roedder, 1965;Kamenetsky et al, 1986;Coombs and Roedder, 1994;Sobolev and Nikogosian, 1994;Lowenstern, 1995;Yang and Scott, 1996) and gases in vesicles from quenched glasses (Moore et al, 1977;Moore, 1979;Javoy and Pineau, 1991). In contrast, water may dominate in the fluid phase at subsurface pressures, especially in the case of H 2 O-enriched subduction-related magmas, as observed in arc -backarc glasses (e.g., Garcia et al, 1979;Danyushevsky et al, 1992;Alt et al, 1993), melt inclusions (Sobolev and Naumov, 1985), emanations from arc volcanoes (Hedenquist and Lowenstern, 1994) and comparison of H 2 O contents in glasses and melt inclusions (Sobolev and Chaussidon, 1996). Thus, most basaltic (for an exception, see Gurenko et al, 1988) and all felsic magmas are fluid-saturated during crystallisation, and produce a volatile phase in the form of fluid bubbles (Bottinga and Javoy, 1990).…”

Section: Origin Of Precipitates In Fluid Bubblesmentioning

confidence: 99%

Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluids?

et al. 2002

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Hypotheses for the formation of many types of hydrothermal ore deposits often involve the direct contribution of magmarelated fluids (e.g., Cu -Mo -Au porphyries) or their superimposition on barren hydrothermal cells (e.g., volcanic-hosted massive sulfide deposits). However, the chemical and phase compositions of such fluids remain largely unknown. We report preliminary results of a comprehensive study of fluid bubbles trapped inside glassy melt inclusions in primitive olivine phenocrysts and pillow-rim glasses from basaltic magmas from different tectonic environments, including mid-ocean ridges (Macquarie Island, SW Pacific and Mid-Atlantic Ridge 43°N Fracture Zone), ocean islands (Hawaii) and a variety of modern and ancient backarc -island arc settings (eastern Manus Basin, Okinawa and Vanuatu Troughs, Troodos, New Caledonia and Hunter Ridge -Hunter Fracture Zone). Fluid bubbles from all localities, studied using electron microscopy with EDS and laser Raman spectroscopy, are composed of CO 2 -( ± H 2 O ± sulfur)-bearing vapor and contain significant amounts of amorphous (Na -K -Ca -Fe alumino-silicates and dissorded carbon) and crystalline phases. The crystals are represented mainly by carbonates (magnesite, calcite, ankerite, dolomite, siderite, nahcolite and rhodochrosite), sulfates (anhydrite, gypsum, barite and anglesite), and sulfides (pyrite, arsenopyrite, chalcopyrite and marcasite), though other minerals (brukite, apatite, halite, clinoenstatite, kalsilite, nepheline, amphibole and mica) may occur as well. We argue that chemical components (e.g., C, H, S, Cl, Si, Al, Na, K, Fe, Mn, Cr, Ca, Mg, Ba, Pb and Cu) that later formed precipitates in fluid bubbles were originally dissolved in the magmatic fluid, and were not supplied by host glasses or phenocrysts after entrapment. Magma-related fluid rich in dissolved metals and other non-volatile elements may be a potential precursor to ore-forming solutions. D

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“…Most of deposits around the Miaoershan-Yuechenling complex pluton have W-Sn (Mo) element association and high temperature alteration such as greisenization, suggesting they are related to magmatic hydrothermal activities. Magmatic hydrothermal deposits are genetic related to an aqueous volatile phase exsolved from silicate melts [32,[38][39][40][41][42][43][44][45][46] or fluids in equilibrium with silicate melts. If the silicate melts underwent mineralization processes during the ascending and crystallization of the melts, the aqueous volatile phase resolved from the melts should have reacted with the adjacent country rocks.…”

Section: Formation Of Ore Deposits Around the Miaoershanyuechenling Cmentioning

confidence: 99%

Indosinian isotope ages of plutons and deposits in southwestern Miaoershan-Yuechengling, northeastern Guangxi and implications on Indosinian mineralization in South China

Liang

Huang

et al. 2012

Chin. Sci. Bull.

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The Miaoershan-Yuechengling complex pluton is the largest granitoid complex in the western Nanling metallogenic belt with a surface exposure of >3000 km 2 . The complex pluton is composed of an early stage granitoid batholith and late stage small intrusions. The early stage batholith contains mainly medium-grained porphyritic mica granite and porphyritic monzonite granite, whereas the late stage intrusions are composed of muscovite granite porphyry and muscovite monzonitic granite. There are many W-Sn-Mo-Pb-Zn-Cu ores in the contact zone between the batholith and strata, forming an ore-rich belt around the batholith. Based on zircon LA-ICP-MS U-Pb ages, the southwestern part of the early stage batholith formed at 228.7 ± 4.1 Ma (MSWD = 2.49), with slightly earlier magmatic activity at 243.0 ± 5.8 Ma (MSWD = 2.62). The Yuntoujie muscovite granite was associated with W-Mo mineralization and has a zircon LA-ICP-MS U-Pb age of 216.8 ± 4.9 Ma (MSWD = 1.44). The Re-Os isochron age of molybdenite from the Yuntoujie W-Mo ore was 216.8 ± 7.5 Ma (MSWD = 11.3). Our new isotope data suggest that the late stage intrusive stocks from the southwestern Miaoershan-Yuechengling batholith were closely associated with W-Mo mineralization from the Indosinian period. These new results together with previous isotope data, suggest that South China underwent not only the well-known Yanshanian mineralization event, but also a widespread Indosinian metallogenic event during the Mesozoic period. Therefore, South China has a greater potential for Indosinian mineralization than previously thought such that more attention should be given to the Indosinian ore prospecting in South China. The Nanling metallogenic ore belt is well known for its WSn-Be-Nb-Ta-REE mineralization and has attracted much attention from geoscientists worldwide. A large amount of the work from South China has examined the temporal and spatial distributions of the granitoids and their associated mineralizations . Most of that work focuses on the granitoids and related deposits in the middle and the eastern parts of the Nanling ore belt, whereas there is less research from the western part of Nanling ore belt. South China underwent both Indosinian and Yanshanian structural-magmatic events with more focus on the Yanshanian stage mineralization. The Miaoershan-Yuechengling complex pluton is the largest granitoid pluton outcrop in the western Nanling metallogenic belt. Many W-Sn (Mo) and Pb-Zn-Cu deposits

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The role of magmas in the formation of hydrothermal ore deposits

Cited by 1,538 publications

References 60 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

Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluids?

Indosinian isotope ages of plutons and deposits in southwestern Miaoershan-Yuechengling, northeastern Guangxi and implications on Indosinian mineralization in South China

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