On the Sr isotope and REE compositions of anhydrites from the TAG seafloor hydrothermal system

Humphris, Susan E.; Bach, Wolfgang

doi:10.1016/j.gca.2004.10.004

Cited by 49 publications

(32 citation statements)

References 48 publications

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“…LREE are obviously depleted and Eu anomalies are enhanced in real hydrothermal fluids when comparing to the ideal mixing fluids, which indicate LREE and Eu are fractionated during mixing. The distribution coefficients between anhydrite and fluids for LREE and Eu 2+ are larger than those for HREE under the crystallographic control (Morgan and Wandless, 1980), hence anhydrite could cause the LREE-rich and negative Eu anomaly fluidsnormalized REE patterns (Humphris and Bach, 2005;Mills and Elderfield, 1995). Anhydrite is easy to precipitate when high temperature vent fluids mix with seawater, so we hypothesize that the LREE-depleted patterns and the enhanced positive Eu anomalies in CBF and SWS fluids are caused by the crystochemical exchange with anhydrite.…”

Section: Y/ho Ratios and Mixing With Seawatermentioning

confidence: 91%

Geochemistry of REE and yttrium in hydrothermal fluids from the Endeavour segment, Juan de Fuca Ridge

et al. 2008

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Rare earth element and yttrium in hydrothermal fluids sampled from six high temperature vents and two diffuse flow sites on the Endeavour segment, Juan de Fuca Ridge by US-CHINA Joint Deep Dive Cruise in Aug. 2005 were analyzed by ICP-MS after being pre-concentrated by 20-fold. According to the species distributions calculated by GWB, the chondritenormalized REE patterns (REE CN ) of these fluids are characterized by LREE enrichment and positive Eu anomalies, which are mainly controlled by complexing with chloride. The (La/Yb) CN ratio does not correlate significantly with fluoride. Sulfate content are low in most high temperature fluids except in Gremlin vent fluids. Certain amounts of REE are complexed with sulfate that likely originates from oxidation of magmatic SO 2 and/or H 2 S in Gremlin. Sulfates, mostly come from seawater, are also responsible of large percentage of REE complexes in diffuse fluids.It is shown by the character of REY concentrations and the Y/Ho ratios that REE removed by Fe, Mn-oxyhydroxides is negligible in most of high temperature vent fluids. However, the Y/Ho ratios in Gremlin (Y/Ho = 160) and Faulty Towers (Y/Ho = 140) vent fluids are higher than that in other high temperature vent fluids, suggesting REE removal controlled by coprecipitation and scavenging. The negative Ce anomalies in diffuse fluids also result from the scavenging of mineral particles in the oxidizing conditions when mixing with seawater. Compared to ideal mixing fluids calculated by Mg content, two diffuse fluids display LREE-depleted patterns and enhanced positive Eu anomalies. Based on the REE characteristics of anhydrite, the REE distribution patterns of diffuse fluids are probably influenced largely by anhydrite precipitation under the seafloor at diffuse fluids sites. It is interesting to notice that the HREE CN pattern of Mothra vent fluids is similar to sediments but different from the sediment-starved hydrothermal fluids, suggesting they are likely remolded by the sediments in water-rock interaction zone and/or upflow zone nearby Mothra vent field. The provenance and character of these sediments bears further investigation.Keywords: hydrothermal fluids, rare earth element, Juan de Fuca Ridge, species abundance, Europium anomaly (Fouquet et al., 1993).Although the characteristics of REY in MOR systems have been well documented, the factors controlling the patterns and distributions of REY in hydrothermal fluids are still in debate. Klinkhammer et al. (1994a) systematically studied the REE of hydrothermal fluids from eight deep-sea hydrothermal areas and predicted that the REE distribution is dominated by crystochemical exchange with plagioclase phenocrysts. However, laboratory experiments indicated interstitial material and some secondary minerals are the main REE sources in the rock (Bach and Irber, 1998). Furthermore, coprecipitating with metal particles (German et al

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Section: Y/ho Ratios and Mixing With Seawatermentioning

confidence: 91%

Geochemistry of REE and yttrium in hydrothermal fluids from the Endeavour segment, Juan de Fuca Ridge

et al. 2008

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“…, respectively, in hydrothermal fluid that has mixed with SO 4 2À -rich seawater) (Von Damm, 1990;Tivey et al, 1999;Hannington et al, 2005;Humphris and Bach, 2005). Mineral precipitation is driven mainly by the changes in temperature, pH, fO 2 , and concentration of dissolved ions that accompany the mixing of hot hydrothermal fluid and cold seawater, although fluid temperature can also be affected by conductive cooling and heating (Tivey and McDuff, 1990;Hannington et al, 1995;Tivey, 1995;Tivey et al, 1999;Ruiz-Agudo et al, 2015).…”

Section: +mentioning

confidence: 99%

Precipitation and growth of barite within hydrothermal vent deposits from the Endeavour Segment, Juan de Fuca Ridge

Jamieson

Hannington

Tivey

et al. 2016

Geochimica et Cosmochimica Acta

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Hydrothermal vent deposits form on the seafloor as a result of cooling and mixing of hot hydrothermal fluids with cold seawater. Amongst the major sulfide and sulfate minerals that are preserved at vent sites, barite (BaSO 4 ) is unique because it requires the direct mixing of Ba-rich hydrothermal fluid with sulfate-rich seawater in order for precipitation to occur. Because of its extremely low solubility, barite crystals preserve geochemical fingerprints associated with conditions of formation. Here, we present data from petrographic and geochemical analyses of hydrothermal barite from the Endeavour Segment of the Juan de Fuca Ridge, northeast Pacific Ocean, in order to determine the physical and chemical conditions under which barite precipitates within seafloor hydrothermal vent systems. Petrographic analyses of 22 barite-rich samples show a range of barite crystal morphologies: dendritic and acicular barite forms near the exterior vent walls, whereas larger bladed and tabular crystals occur within the interior of chimneys. A two component mixing model based on Sr concentrations and 87 Sr/ 86 Sr of both seawater and hydrothermal fluid, combined with 87 Sr/ 86 Sr data from whole rock and laser-ablation ICP-MS analyses of barite crystals indicate that barite precipitates from mixtures containing as low as 17% and as high as 88% hydrothermal fluid component, relative to seawater. Geochemical modelling of the relationship between aqueous species concentrations and degree of fluid mixing indicates that Ba 2+ availability is the dominant control on mineral saturation. Observations combined with model results support that dendritic barite forms from fluids of less than 40% hydrothermal component and with a saturation index greater than $0.6, whereas more euhedral crystals form at lower levels of supersaturation associated with greater contributions of hydrothermal fluid. This document is a U.S. government work and is not subject to copyright in the United States.from cyclical oscillations in hydrothermal fluid flux. Barite chemistry and morphology can be used as a reliable indicator for past conditions of mineralization within both extinct seafloor hydrothermal deposits and ancient land-based volcanogenic massive sulfide deposits.

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“…Eu is expected to be divalent in hydrothermal solutions at high temperatures (>250 °C) (Sverjensky, 1984). Eu 2+ possibly forms stable complexes with Cl -in hydrothermal solutions (e.g., Humphris and Bach, 2005) (Fig. 3h).…”

Section: Preservation Of Ree (Except Eu) In Chlorite Rocks: Ree Budgementioning

confidence: 99%

Geochemical characteristics of chloritization of mafic crust from the northern Oman ophiolite: Implications for estimating the chemical budget of hydrothermal alteration of the oceanic lithosphere

Yoshitake

Arai

Ishida³

et al. 2009

Journal of Mineralogical and Petrological Sciences

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We examined dike -like chlorite rocks that replaced isotropic gabbro and dolerite in northern Oman ophiolite in order to understand the chemical budget of hydrothermal alteration of the oceanic lithosphere. During chloritization, the concentrations of Si, Ca, Na, and K decreased, while those of Fe increased. REE (rare -earth elements), except Eu, which showed a strong depletion in the chlorite rocks, were immobile during chloritization, which was caused by the downward (recharge) flow of circulated seawater. A portion of Fe was supplied from the overlying mafic extrusives, possibly through the alteration of their plagioclases. We found Ti -rich minerals such as rutile and titanite to be the reservoirs of most REE in the chlorite rocks. If the residual fluid, after chloritization, moves upward, it can realize the positive Eu anomaly of the seafloor vent fluids. And, if the fluid is transported to deeper parts of the oceanic lithosphere, rodingites, serpentinites (antigorite rocks), and diposidites with a positive Eu anomaly are formed within gabbros and mantle peridotites.

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On the Sr isotope and REE compositions of anhydrites from the TAG seafloor hydrothermal system

Cited by 49 publications

References 48 publications

Geochemistry of REE and yttrium in hydrothermal fluids from the Endeavour segment, Juan de Fuca Ridge

Geochemistry of REE and yttrium in hydrothermal fluids from the Endeavour segment, Juan de Fuca Ridge

Precipitation and growth of barite within hydrothermal vent deposits from the Endeavour Segment, Juan de Fuca Ridge

Geochemical characteristics of chloritization of mafic crust from the northern Oman ophiolite: Implications for estimating the chemical budget of hydrothermal alteration of the oceanic lithosphere

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