Footwall Geology and Deformation at Flip‐Flop Mid‐Ocean Ridge Detachment Faults: 64°35′E Southwest Indian Ridge (SWIR)

Geochemistry Geophysics Geosystems, Год журнала: 2025, Номер 26(1)

Опубликована: Янв. 1, 2025

Abstract Using bathymetry and ROV dives, we investigate two successive flip‐flop detachment faults (D1 active, D2 older) in the near‐amagmatic 64°35′E region of SWIR. Kilometer‐sized benches on upper slopes D1 footwall form degraded breakaway. Scarps at top expose fault zone with deformed serpentinized peridotite, sigmoidal phacoids, planar fractures, serpentinite microbreccia/gouge horizons. Two sections show contrasting deformation styles, corresponding to distinct morphological domains, which relate strength. One section documents corrugations, outcrops dominated by fractures thin, discontinuous dives this corrugated domain that NNE‐trending km‐spaced ridges WNW‐trending narrow shipboard correspond, respectively, broad undulations (mega‐corrugations) several antithetic minor normal (cumulated horizontal offset ∼285 m). The other section, lacking ridges, fault, has thicker more continuous horizons, indicating a weaker fault. abundance such weak gouges probably reflects hydrous fluid availability during deformation. We link mega‐corrugations western km‐scale lobes emergence damage up ∼600 m‐thick mega‐phacoids less peridotite. Small are interpreted as due bending forces footwall. Our findings highlight three‐dimensional, non‐planar structural variability exhumed along ridge‐axis.

Язык: Английский

The Effect of Brittle‐Ductile Weakening on the Formation of Faulting Patterns at Mid‐Ocean Ridges

Tectonics, Год журнала: 2025, Номер 44(2)

Опубликована: Янв. 31, 2025

Abstract Although seafloor spreading is one of the most prominent plate tectonic processes, its development and faulting pattern diversity are incompletely understood. This study addresses how brittle‐ductile weakening affects formation patterns at centers using 3D magmatic‐thermomechanical numerical models. Grain size evolution brittle/plastic strain‐dependent friction coefficient fully coupled into A spectrum patterns, from asymmetric long‐lived detachment faults developing by same polarity to short‐lived flip‐flop mode symmetric conjugate faults, documented in our Systematic results indicate that fault strength reduction axial brittle layer thickness two pivotal factors controlling modes. Through varying initial coefficients, we found strong with significant very polarity, while weak leads slight reduction, forming faults. In addition, thermal structure, influenced rates, hydrothermal cooling, mantle potential temperature, turn, controls patterns. To test a damage mechanism physical basis, investigate grain root We compared layer, oceanic appears be less sensitive which mainly due relatively shallow spontaneously accreting lithosphere

Язык: Английский

Massive Sulfide Deposition at the 13°30’N Oceanic Core Complex: Lessons Learned From Coupled Hydro‐Thermo‐Mechanical Modeling

Geochemistry Geophysics Geosystems, Год журнала: 2025, Номер 26(6)

Опубликована: Июнь 1, 2025

Abstract Young oceanic lithosphere created at mid‐ocean spreading centers is subject to complex magmatic, tectonic and hydrothermal processes, especially in regions of widespread detachment faulting. This study focuses on the core (OCC) Mid Atlantic Ridge 13°30’N. The OCC hosts active Semenov‐2 vent field four inactive fields, including exceptionally large Semenov‐4 sulfide deposit (10 Mt), which located near emergence a fault. To relationship between faulting fluid circulation we couple models for mechanical deformation flow. Our aim identify role controlling location size deposition. First, develop baseline model tectono‐magmatic evolution using data‐based sequence magnitude position axial magmatic diking. resulting history provides dynamic framework modeling flow through porous rock, incorporating seafloor topography evolution. We then examine impact various fault zone permeability structures heat sources results show that combination topographic influence, anisotropic along zone, transient shallow plume interactions can efficiently reorganize system. Increasing horizontal distance source field, however, significantly reduces stability. Modeled mass rates suggest fields like TAG result from focusing across entire along‐axis extent structure.

Язык: Английский