How Hydrothermal Cooling and Magmatic Sill Intrusions Control Flip‐Flop Faulting at Ultraslow‐Spreading Mid‐Ocean Ridges

Geochemistry Geophysics Geosystems, Journal Year: 2024, Volume and Issue: 25(2)

Published: Feb. 1, 2024

Abstract “Flip‐flop” detachment mode represents an endmember type of lithosphere‐scale faulting observed at almost amagmatic sections ultraslow‐spreading mid‐ocean ridges. Recent numerical experiments using imposed steady temperature structure show that axial maximum is essential to trigger flip‐flop faults by focusing flexural strain in the footwall active fault. However, ridge segments without significant melt budget are more likely be a transient thermal state controlled, least partly, dynamics themselves. Therefore, we investigate which processes control lithosphere and how feedbacks with deformation mechanisms can explain patterns. We present results 2‐D thermo‐mechanical modeling including serpentinization reactions dynamic grain size evolution. The model features novel form parametrized hydrothermal cooling along fault zones as well rheological effects periodic sill intrusions. find interplay zone intrusions facilitates mode. Hydrothermal pushes into footwall, while near further weaken rock promote formation new opposite polarity. Our allows us put constraints on magnitude two processes, obtain most reasonable budgets heat fluxes if both considered. Furthermore, frequently observe other modes our complementing yield potentially robust alternative interpretation for existing observations.

Language: Английский

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On the Relative Importance of Buoyancy and Thickening of Aging Lithosphere in Mantle Upwelling and Crustal Production Beneath Global Mid‐Ocean Ridge System

Journal of Geophysical Research Solid Earth, Journal Year: 2024, Volume and Issue: 129(5)

Published: May 1, 2024

Abstract Beneath mid‐ocean ridges, mantle upwelling and decompression melting are fundamental processes contributing to the formation of oceanic crust. Previous geodynamic models have suggested that driven by separating plates can be intensified thermochemical buoyancy thickening aging lithosphere, resulting in thicker However, relative contributions these factors crustal accretion remain uncertain. We conducted numerical modeling three scenarios investigate this: (a) buoyant flow incorporating age‐dependent lithospheric as a reference; (b) passive isolate effect buoyancy; (c) neglect its effect. Models performed under varying potential temperatures (Tp), viscosity structures, spreading rates. The model‐predicted thickness suggests both lithosphere increasingly contribute production rate decreases. given range reference viscosities examined here (10 19 –10 20 Pa s), except ultraslow rates with lower warmer Tp, impact predominates over buoyancy. Furthermore, importance buoyancy‐induced increases decrease. Variations Tp further amplify variability compared at fast‐spreading ridges where dominates, when combined 3‐D effects on altering axial ultraslow‐spreading ridge segments. This 4‐D melt may explain observed more variable ridges.

Language: Английский

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Hydrothermal carbon reduction in the absence of minerals

Geochimica et Cosmochimica Acta, Journal Year: 2024, Volume and Issue: 381, P. 60 - 74

Published: July 26, 2024

Abiotic synthesis of CH4 in seafloor hydrothermal fluids is generally assumed to occur via heterogeneous reactions on mineral surfaces. Stepwise homogeneous reduction CO2 has, however, been suggested as an alternative (but sluggish) abiotic pathway CH4, potentially metastable species intermediate oxidation states. In this study, we examine the effect two temperature-dependent methylated − methanol (CH3OH) and methanethiol (CH3SH), formation rates under long-term simulated conditions. Aqueous solutions containing formic acid (H13COOH, generating 13CO2 H2) were heated with without H2S at 300–325 °C (35 MPa) a flexible Au reaction cell over several years added minerals. Substantial 13C-labeled CH3OH production from was observed 4.3 yr, aqueous varying abundance – strong function dissolved H2 and, inversely, temperature. slower 325 lower concentrations (in equilibrium H2), faster 300 °C, accompanying equilibrium-controlled increase CH3OH. Fastest occurred following injection H13COOH, which led rapid (<4 days) CH3SH that subsequently decomposed further 0.8 partly 13CH4. Heating 13CH4 345–387 (33–35 presence oxidizing hematite-magnetite-pyrite assemblage, yielded no detectable after 112 days indicating reverse inhibited favorable thermodynamics. Neither direct nor CO2-CH3SH evident implying play disparate roles carbon CH4. Longer chain hydrocarbons (C2+ alkanes) remained low throughout experiments. abundances previously reported vent Von Damm field correlate strongly demonstrably HCOOH there, suggesting study may also fluids. A comparison mineral-free here experiments involving minerals indicates proceeds similar purported transition metal-catalyzed production, than either olivine or ultramafic rock. Previous claims substantial mineral-catalyzed abiogenic are therefore not supported by our study. Homogeneous be significant source compounds characterized decadal (or longer) residence times, such those found mineral-hosted inclusions occluded fractures igneous basement, requiring only moderate temperatures abundant proceed.

Language: Английский

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Hydrothermal vents supporting persistent plumes and microbial chemoautotrophy at Gakkel Ridge (Arctic Ocean)

Frontiers in Microbiology, Journal Year: 2024, Volume and Issue: 15

Published: Oct. 3, 2024

Hydrothermal vents emit hot fluids enriched in energy sources for microbial life. Here, we compare the ecological and biogeochemical effects of hydrothermal venting two recently discovered volcanic seamounts, Polaris Aurora Gakkel Ridge, ice-covered Central Arctic Ocean. At both sites, persistent plumes increased up to 800 m into deep In non-buoyant plumes, rates carbon fixation were strongly elevated compared background values 0.5-1 μmol

Language: Английский

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Gold mineralization in the hydrothermal field at the termination of a detachment fault: A case study of the Tianxiu Vent Field

Mineralium Deposita, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 28, 2024

Language: Английский

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