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  • AGU (American Geophysical Union)  (19)
  • Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag  (3)
  • 1
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    Faulting and off-axis submarine massive sulfide accumulation at slow spreading mid-ocean ridges: A numerical modeling perspective (2017)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 18 (6). 2305-2320 .
    Details
    Publication Date: 2020-02-06
    Description: The potential of mining seafloor massive sulfide deposits for metals such as Cu, Zn, and Au is currently debated. One key challenge is to predict where the largest deposits worth mining might form, which in turn requires understanding the pattern of subseafloor hydrothermal mass and energy transport. Numerical models of heat and fluid flow are applied to illustrate the important role of fault zone properties (permeability and width) in controlling mass accumulation at hydrothermal vents at slow spreading ridges. We combine modeled mass-flow rates, vent temperatures, and vent field dimensions with the known fluid chemistry at the fault-controlled Logatchev 1 hydrothermal field of the Mid-Atlantic Ridge. We predict that the 135 kilotons of SMS at this site (estimated by other studies) can have accumulated with a minimum depositional efficiency of 5% in the known duration of hydrothermal venting (58,200 year age of the deposit). In general, the most productive faults must provide an efficient fluid pathway while at the same time limit cooling due to mixing with entrained cold seawater. This balance is best met by faults that are just wide and permeable enough to control a hydrothermal plume rising through the oceanic crust. Model runs with increased basal heat input, mimicking a heat flow contribution from along-axis, lead to higher mass fluxes and vent temperatures, capable of significantly higher SMS accumulation rates. Nonsteady state conditions, such as the influence of a cooling magmatic intrusion beneath the fault zone, also can temporarily increase the mass flux while sustaining high vent temperatures.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2017GC006880
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    New Insights into the mineralogy of the Atlantis II deep metalliferous sediments, Red Sea (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 16 (12). pp. 4449-4478.
    Details
    Publication Date: 2019-09-23
    Description: The Atlantis II Deep of the Red Sea hosts the largest known hydrothermal ore deposit on the ocean floor and the only modern analog of brine pool-type metal deposition. The deposit consists mainly of chemical-clastic sediments with input from basin-scale hydrothermal and detrital sources. A characteristic feature is the millimeter-scale layering of the sediments, which bears a strong resemblance to banded iron formation (BIF). Quantitative assessment of the mineralogy based on relogging of archived cores, detailed petrography, and sequential leaching experiments shows that Fe-(oxy)hydroxides, hydrothermal carbonates, sulfides, and authigenic clays are the main “ore” minerals. Mn-oxides were mainly deposited when the brine pool was more oxidized than it is today, but detailed logging shows that Fe-deposition and Mn-deposition also alternated at the scale of individual laminae, reflecting short-term fluctuations in the Lower Brine. Previous studies underestimated the importance of nonsulfide metal-bearing components, which formed by metal adsorption onto poorly crystalline Si-Fe-OOH particles. During diagenesis, the crystallinity of all phases increased, and the fine layering of the sediment was enhanced. Within a few meters of burial (corresponding to a few thousand years of deposition), biogenic (Ca)-carbonate was dissolved, manganosiderite formed, and metals originally in poorly crystalline phases or in pore water were incorporated into diagenetic sulfides, clays, and Fe-oxides. Permeable layers with abundant radiolarian tests were the focus for late-stage hydrothermal alteration and replacement, including deposition of amorphous silica and enrichment in elements such as Ba and Au.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015GC006010
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Geochemistry of vent fluid particles formed during initial hydrothermal fluid–seawater mixing along the Mid-Atlantic Ridge (2011)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 12 . Q0AE05.
    Details
    Publication Date: 2018-03-13
    Description: We present geochemical data of black smoker particulates filtered from hydrothermal fluids with seawater-dilutions ranging from 0–99%. Results indicate the dominance of sulphide minerals (Fe, Cu, and Zn sulphides) in all samples taken at different hydrothermal sites on the Mid-Atlantic Ridge. Pronounced differences in the geochemistry of the particles between Logatchev I and 5°S hydrothermal fields could be attributed to differences in fluid chemistry. Lower metal/sulphur ratios (Me/H2S 〈 1) compared to Logatchev I result in a larger amount of particles precipitated per liter fluid and the occurrence of elemental sulphur at 5°S, while at Logatchev I Fe oxides occur in larger amounts. Systematic trends with dilution degree of the fluid include the precipitation of large amounts of Cu sulphides at a low dilution and a pronounced drop with increasing dilution. Moreover, Fe (sulphides or oxides) precipitation increases with dilution of the vent fluid by seawater. Geochemical reaction path modeling of hydrothermal fluid–seawater mixing and conductive cooling indicates that Cu sulphide formation at Logatchev I and 5°S mainly occurs at high temperatures and low dilution of the hydrothermal fluid by seawater. Iron precipitation is enhanced at higher fluid dilution, and the different amounts of minerals forming at 5°S and Logatchev I are thermodynamically controlled. Larger total amounts of minerals and larger amounts of sulphide precipitate during the mixing path when compared to the cooling path. Differences between model and field observations do occur and are attributable to closed system modeling, to kinetic influences and possibly to organic constituents of the hydrothermal fluids not accounted for by the model.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2011GC003704
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Shallow submarine hydrothermal systems in the Aeolian Volcanic Arc, Italy (2009)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 90 (13). pp. 110-111.
    Details
    Publication Date: 2019-09-23
    Description: The majority of known high-temperature hydrothermal vents occur at mid-ocean ridges and back-arc spreading centers, typically at water depths from 2000 to 4000 meters. Compared with 30 years of hydrothermal research along spreading centers in the deep parts of the ocean, exploration of the approximately 700 submarine arc volcanoes is relatively recent [de Ronde et al., 2003]. At these submarine arc volcanoes, active hydrothermal vents are located at unexpectedly shallow water depth (95% at 〈1600-meter depth), which has important consequences for the style of venting, the nature of associated mineral deposits, and the local biological communities. As part of an ongoing multinational research effort to study shallow submarine volcanic arcs, two hydrothermal systems in the submerged part of the Aeolian arc have been investigated in detail during research cruises by R/V Poseidon (July 2006) and R/V Meteor (August 2007). Comprehensive seafloor video surveys were conducted using a remotely operated vehicle, and drilling to a depth of 5 meters was carried out using a lander-type submersible drill. This research has resulted in the first detailed, three-dimensional documentation of shallow submarine hydrothermal systems on arc volcanoes
    Type: Article , NonPeerReviewed
    Format: text
    Format: text
    DOI: 10.1029/2009EO130002
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    OceanRep: Article in a Scientific Journal - without review
  • 5
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    Physical and chemical processes of seafloor mineralization at mid-ocean ridges (1995)
    AGU (American Geophysical Union)
    In:  In: Seafloor Hydrothermal Systems: Physical, Chemical, Biological, and Geological Interactions. , ed. by Humphris, S. E., Zierenberg, R. A., Mullineaux, L. S. and Thomson, R. E. Geophysical Monograph Series, 91 . AGU (American Geophysical Union), Washington, DC, pp. 115-157. ISBN 0-87590-048-8
    Details
    Publication Date: 2016-05-31
    Type: Book chapter , PeerReviewed
    Format: text
    DOI: 10.1029/GM091p0115
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    OceanRep: Book chapter
  • 6
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    Metal resource potential and fluxes at a slow-spreading mid-ocean ridge segment: M127 – Blue Mining @ Sea, seismic and magnetic investigations (2020)
    Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
    In:  In: DFG Status Conference Research Vessels 2020. Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Jülich, pp. 101-103. ISBN 978-3-95806-479-9
    Details
    Publication Date: 2020-07-08
    Type: Book chapter , NonPeerReviewed
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    OceanRep: Book chapter
  • 7
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    M127: Metal fluxes and resource potential at the slow-spreading TAG mid-ocean ridge segment (26°N, MAR) (2020)
    Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
    In:  In: DFG Status Conference Research Vessels 2020. Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Jülich, pp. 97-100. ISBN 978-3-95806-479-9
    Details
    Publication Date: 2020-07-08
    Type: Book chapter , NonPeerReviewed
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    OceanRep: Book chapter
  • 8
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    Heat flow and mineralogy of TAG relict high-temperature hydrothermal zones: Mid-Atlantic Ridge 26°N, 45°W (1996)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 23 (23). pp. 3507-3510.
    Details
    Publication Date: 2016-05-12
    Description: Submersible investigations employing heat flow measurements (12 stations), sampling and imagery of the two relict high-temperature hydrothermal zones of the TAG field, the Alvin and Mir sulfide zones, elucidate relations between heat sources and mineralization including an active sulfide mound that has been the focus of prior studies. Values of heat flow in the Mir zone and at the margin of the active mound are inversely proportional to distance from adjacent volcanic centers. This observation supports the hypothesis that intrusions at volcanic centers adjacent to the high-temperature hydrothermal zones supply the heat to drive hydrothermal activity. The chronology of hydrothermal deposits in the different zones indicates that the intrusions are episodic with field-wide high-temperature hydrothermal events recurring at intervals of tens of thousands of years, while activity at individual zones may recur at intervals of hundreds to thousands of years. A sequence of hydrothermal deposits ranges to at least 140,000 years ago from massive sulfides forming at the active mound, to recrystallization of sulfides in the active and relict zones, to pyritization of an inactive mound in the Alvin zone; low-temperature mineral phases precipitate before, during and after the sulfides.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/96GL03257
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Young volcanism and related hydrothermal activity at 5°S on the slow-spreading southern Mid-Atlantic Ridge (2007)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 8 (Q11002).
    Details
    Publication Date: 2019-09-24
    Description: The effect of volcanic activity on submarine hydrothermal systems has been well documented along fast- and intermediate-spreading centers but not from slow-spreading ridges. Indeed, volcanic eruptions are expected to be rare on slow-spreading axes. Here we report the presence of hydrothermal venting associated with extremely fresh lava flows at an elevated, apparently magmatically robust segment center on the slow-spreading southern Mid-Atlantic Ridge near 5°S. Three high-temperature vent fields have been recognized so far over a strike length of less than 2 km with two fields venting phase-separated, vapor-type fluids. Exit temperatures at one of the fields reach up to 407°C, at conditions of the critical point of seawater, the highest temperatures ever recorded from the seafloor. Fluid and vent field characteristics show a large variability between the vent fields, a variation that is not expected within such a limited area. We conclude from mineralogical investigations of hydrothermal precipitates that vent-fluid compositions have evolved recently from relatively oxidizing to more reducing conditions, a shift that could also be related to renewed magmatic activity in the area. Current high exit temperatures, reducing conditions, low silica contents, and high hydrogen contents in the fluids of two vent sites are consistent with a shallow magmatic source, probably related to a young volcanic eruption event nearby, in which basaltic magma is actively crystallizing. This is the first reported evidence for direct magmatic-hydrothermal interaction on a slow-spreading mid-ocean ridge.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2006GC001509
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    High-resolution magnetics reveal the deep structure of a volcanic-arc-related basalt-hosted hydrothermal site (Palinuro, Tyrrhenian Sea) (2015)
    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 16 (6). pp. 1950-1961.
    Details
    Publication Date: 2017-04-12
    Description: High-resolution magnetic surveys have been acquired over the partially sedimented Palinuro massive sulfide deposits in the Aeolian volcanic arc, Tyrrhenian Sea. Surveys flown close to the seafloor using an autonomous underwater vehicle (AUV) show that the volcanic-arc-related basalt-hosted hydrothermal site is associated with zones of lower magnetization. This observation reflects the alteration of basalt affected by hydrothermal circulation and/or the progressive accumulation of a nonmagnetic deposit made of hydrothermal and volcaniclastic material and/or a thermal demagnetization of titanomagnetite due to the upwelling of hot fluids. To discriminate among these inferences, estimate the shape of the nonmagnetic deposit and the characteristics of the underlying altered area—the stockwork—we use high-resolution vector magnetic data acquired by the AUV Abyss (GEOMAR) above a crater-shaped depression hosting a weakly active hydrothermal site. Our study unveils a relatively small nonmagnetic deposit accumulated at the bottom of the depression and locked between the surrounding volcanic cones. Thermal demagnetization is unlikely but the stockwork extends beyond the limits of the nonmagnetic deposit, forming lobe-shaped zones believed to be a consequence of older volcanic episodes having contributed in generating the cones.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2015GC005769
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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