GLORIA — GEOMAR Library Ocean Research Information Access

1

Online Resource

Global quantification of methane hydrates (2013)

Kretschmer, Kerstin [VerfasserIn]

Kiel

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Keywords: Hochschulschrift

Type of Medium: Online Resource

Pages: 1 Online-Ressource (83 Seiten = 7 MB) , Graphen, Karten

Edition: 2022

URL: https://oceanrep.geomar.de/22795/

Language: English

Note: Zusammenfassung in deutscher und englischer Sprache

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2

Article

Neptun, Pluto und die tiefen Wasserkreisläufe unseres Planeten Erde (2010)

Rüpke, Lars 1975-

Bremen : MARUM

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In: Expedition Erde, Bremen : MARUM - Zentrum für Marine Umweltwissenschaften, 2010, (2010), Seite 100-107, 9783000307720

In: year:2010

In: pages:100-107

Type of Medium: Article

Pages: zahlr. Ill. (farb.), graph. Darst., Kt.

Language: German

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3

Online Resource

Coupled mechanical and hydrothermal modeling of crustal accretion at intermediate to fast spreading ridges (2011)

Theißen-Krah, Sonja 1981-

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In: Earth and planetary science letters, Amsterdam [u.a.] : Elsevier, 1966, 311(2011), 3/4, Seite 275-286, 1385-013X

In: volume:311

In: year:2011

In: number:3/4

In: pages:275-286

Description / Table of Contents: The genesis of oceanic crust at intermediate to fast spreading ridges occurs by the crystallization of mantle melts accumulated in at least one shallow melt lens situated below the ridge axis. Seismic reflection data suggest that the depth of this melt lens is inversely correlated with spreading rate and thereby magma supply. The heat released in it by crystallization and melt injection is removed by a combination of hydrothermal cooling and diffusion. Due to the different time scales of hydrothermal cooling and crustal accretion, numerical models have so far focused on only one of the two processes. Here we present the results from a coupled model that solves simultaneously for crustal accretion and hydrothermal cooling. Our approach resolves both processes within one 2D finite-element model that self-consistently solves for crustal, mantle, and hydrothermal flow. The formation of new oceanic crust is approximated as a gabbro glacier, in which the entire lower crust crystallizes in one shallow melt lens. We find that the depth of the melt lens and the shape of hot (potentially molten) lower crust are highly dependent on the ridge permeability structure. The predicted depth of the melt lens is primarily controlled by the permeability at the ridge axis, whereas the off-axis permeability determines the width of hot lower crust. A detailed comparison of the modeling results with observed locations of the melt lens at intermediate to fast spreading ridges shows that only a relatively narrow range of crustal permeabilities is consistent with observations. In addition, we find significant deviations between models that resolve or parameterize hydrothermal cooling: the predicted crustal thermal structures show major differences for models that predict the same melt lens location. This illustrates the importance of resolving hydrothermal flow in simulations of crustal accretion.

Type of Medium: Online Resource

Pages: graph. Darst

ISSN: 1385-013X

DOI: 10.1016/j.epsl.2011.09.018

Language: English

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Modeling fluid flow in sedimentary basins with sill intrusions: Implications for hydrothermal venting and climate change (2013)

Iyer, Karthik ; Rüpke, Lars ; Galerne, Christophe Y.

AGU (American Geophysical Union) | Wiley

In: Geochemistry, Geophysics, Geosystems, 14 (12). pp. 5244-5262.

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Publication Date: 2018-02-28

Description: Large volumes of magma emplaced within sedimentary basins have been linked to multiple climate change events due to release of greenhouse gases such as CH4. Basin-scale estimates of thermogenic methane generation show that this process alone could generate enough greenhouse gases to trigger global incidents. However, the rates at which these gases are transported and released into the atmosphere are quantitatively unknown. We use a 2D, hybrid FEM/FVM model that solves for fully compressible fluid flow to quantify the thermogenic release and transport of methane and to evaluate flow patterns within these systems. Our results show that the methane generation potential in systems with fluid flow does not significantly differ from that estimated in diffusive systems. The values diverge when vigorous convection occurs with a maximum variation of about 50%. The fluid migration pattern around a cooling, impermeable sill alone generates hydrothermal plumes without the need for other processes such as boiling and/or explosive degassing. These fluid pathways are rooted at the edges of the outer sills consistent with seismic imaging. Methane venting at the surface occurs in three distinct stages and can last for hundreds of thousands of years. Our simulations suggest that although the quantity of methane potentially generated within the contact aureole can cause catastrophic climate change, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative δ13C excursions observed in the fossil record over short time scales (〈 10,000 years).

Type: Article , PeerReviewed

Format: text

DOI: 10.1002/2013GC005012

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Interrelation between rifting, faulting, sedimentation, and mantle serpentinization during continental margin formation-including examples from the Norwegian Sea (2013)

Rüpke, Lars H. ; Schmid, Daniel W. ; Perez-Gussinye, Marta ; [et al.]

AGU (American Geophysical Union) | Wiley

In: Geochemistry, Geophysics, Geosystems, 14 (10). pp. 4351-4369.

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Publication Date: 2018-02-28

Description: The conditions permitting mantle serpentinization during continental rifting are explored within 2-D thermotectonostratigraphic basin models, which track the rheological evolution of the continental crust, account for sediment blanketing effects, and allow for kinetically controlled mantle serpentinization processes. The basic idea is that the entire extending continental crust has to be brittle for crustal scale faulting and mantle serpentinization to occur. The isostatic and latent heat effects of the reaction are fully coupled to the structural and thermal solutions. A systematic parameter study shows that a critical stretching factor exists for which complete crustal embrittlement and serpentinization occurs. Increased sedimentation rates shift this critical stretching factor to higher values as sediment blanketing effects result in higher crustal temperatures. Sediment supply has therefore, through the temperature-dependence of the viscous flow laws, strong control on crustal strength and mantle serpentinization reactions are only likely when sedimentation rates are low and stretching factors high. In a case study for the Norwegian margin, we test whether the inner lower crustal bodies (LCB) imaged beneath the Møre and Vøring margin could be serpentinized mantle. Multiple 2-D transects have been reconstructed through the 3-D data set by Scheck-Wenderoth and Maystrenko (2011). We find that serpentinization reactions are possible and likely during the Jurassic rift phase. Predicted thicknesses and locations of partially serpentinized mantle rocks fit to information on LCBs from seismic and gravity data. We conclude that some of the inner LCBs beneath the Norwegian margin may be partially serpentinized mantle.

Type: Article , PeerReviewed

Format: text

DOI: 10.1002/ggge.20268

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6

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Coupled mechanical and hydrothermal modeling of crustal accretion at intermediate to fast spreading ridges (2011)

Theissen-Krah, Sonja ; Iyer, Karthik ; Rüpke, Lars ; [et al.]

Elsevier

In: Earth and Planetary Science Letters, 311 (3-4). pp. 275-286.

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Publication Date: 2019-09-23

Description: The genesis of oceanic crust at intermediate to fast spreading ridges occurs by the crystallization of mantle melts accumulated in at least one shallow melt lens situated below the ridge axis. Seismic reflection data suggest that the depth of this melt lens is inversely correlated with spreading rate and thereby magma supply. The heat released in it by crystallization and melt injection is removed by a combination of hydrothermal cooling and diffusion. Due to the different time scales of hydrothermal cooling and crustal accretion, numerical models have so far focused on only one of the two processes. Here we present the results from a coupled model that solves simultaneously for crustal accretion and hydrothermal cooling. Our approach resolves both processes within one 2D finite-element model that self-consistently solves for crustal, mantle, and hydrothermal flow. The formation of new oceanic crust is approximated as a gabbro glacier, in which the entire lower crust crystallizes in one shallow melt lens. We find that the depth of the melt lens and the shape of hot (potentially molten) lower crust are highly dependent on the ridge permeability structure. The predicted depth of the melt lens is primarily controlled by the permeability at the ridge axis, whereas the off-axis permeability determines the width of hot lower crust. A detailed comparison of the modeling results with observed locations of the melt lens at intermediate to fast spreading ridges shows that only a relatively narrow range of crustal permeabilities is consistent with observations. In addition, we find significant deviations between models that resolve or parameterize hydrothermal cooling: the predicted crustal thermal structures show major differences for models that predict the same melt lens location. This illustrates the importance of resolving hydrothermal flow in simulations of crustal accretion.

Type: Article , PeerReviewed

Format: text

DOI: 10.1016/j.epsl.2011.09.018

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Controls of bathymetric relief on hydrothermal fluid flow at mid-ocean ridges (2012)

Bani Hassan, Nasser ; Iyer, Karthik ; Rüpke, Lars H. ; [et al.]

AGU (American Geophysical Union)

In: Geochemistry, Geophysics, Geosystems, 13 . Q05002.

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Publication Date: 2019-09-23

Description: We present quantitative modeling results for the effects of surface relief on hydrothermal convection at ocean-spreading centers investigating how vent site locations and subsurface flow patterns are affected by bathymetry induced sub-seafloor pressure variations. The model is based on a 2-D FEM solver for fluid flow in porous media and is used to simulate hydrothermal convection systematically in 375 synthetic studies. The results of these studies show that bathymetric relief has a profound effect on hydrothermal flow: bathymetric highs induce subsurface pressure variations that can deviate upwelling zones and favor venting at structural highs. The deviation angle from vertical upwelling can be expressed by a single linear dependence relating deviation angle to bathymetric slope and depth of the heat source. These findings are confirmed in two case studies for the East Pacific Rise at 9°30′N and Lucky Strike hydrothermal fields. In both cases, it is possible to predict the observed vent field locations only if bathymetry is taken into account. Our results thereby show that bathymetric relief should be considered in simulations of submarine hydrothermal systems and plays a key role especially in focusing venting of across axis hydrothermal flow onto the ridge axis of fast spreading ridges.

Type: Article , PeerReviewed

Format: text

DOI: 10.1029/2012GC004041

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Control of reaction kinetics on mantle serpentinization and double Benioff zones (2012)

Iyer, Karthik ; Rüpke, Lars H. ; Grevemeyer, Ingo ; [et al.]

CAU

In: [Poster] In: The Lübeck Retreat, Collaborative Research SFB 574 Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanisms for Natural Disasters, 23.05.-25.05.2012, Lübeck . The Lübeck Retreat: final colloquium of SFB 574; May 23-25, 2012: program & abstracts ; p. 13 .

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Publication Date: 2012-10-12

Description: The subduction of partially serpentinized oceanic mantle may potentially be the key geologic process leading to the regassing of Earth’s mantle and also has important consequences for subduction zone processes such as element cycling, slab deformation, and intermediate-depth seismicity. Little is known about the quantity of water that is retained in the slab during mantle serpentinization. Recent studies using thermodynamical and/or experimental models of subduction zone processes have assumed that the mantle is uniformly serpentinized to a depth determined from the equilibrium stability of serpentine minerals in P-T space. This approach yields an incomplete picture of the pattern of serpentinization that may occur during bending-related faulting; an initial state that is essential for quantifying subsequent dehydration processes. In order to provide further constraints on the pattern of hydration and the amount of water trapped in the subducting mantle, we build a 2-D reactive-flow model incorporating the kinetic rate-dependence of serpentinization based on experimental results. After simulating hydration processes at the trench outer-rise, we find that the water content in serpentinized mantle strongly depends on the age of the subducting lithosphere and subduction rate, with values ranging between 1.8x105 and 4.0x106 kgm-2 reactive water uptake into the subducting mantle column. Serpentinization also results in a reduction in surface heat flux towards the trench caused by advective downflow of seawater into the reaction region. Observed heat flow reductions are larger than the reduction due to the minimum-water downflow needed for partial serpentinization, predicting that active hydrothermal vents and chemosynthetic communities should also be associated with bend-fault serpentinization. Model results agree with previous studies that the lower plane of double Benioff zones can be generated due to dehydration of serpentinized mantle at depth. The depth-dependent pattern of serpentinization including reaction kinetics predicts a separation between the two Benioff planes consistent with seismic observations.

Type: Conference or Workshop Item , NonPeerReviewed

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