Serpentinization faults and their role in the tectonics of slow spreading ridges

Francis, T. J. G.

doi:10.1029/jb086ib12p11616

Cited by 142 publications

(91 citation statements)

References 48 publications

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“…Combination of geological field observations, petrological data and geophysical evidence (mostly seismic and gravity data) indicates that at very-slow spreading rates the lower crust may not comprise solely magmatic gabbros, but may consist at least partially of serpentinized peridotite [Cannat, 1993]. The upper mantle might be highly serpentinized [Francis, 1981] or contain magma that has been frozen and trapped due to increased cooling resulting h'om the very slow spreading (Cannat [1996] suggests that the amount of frozen melt in the upper mantle may be as high as 25% down to 10-20 km depth).…”

Section: Introductionmentioning

confidence: 99%

geophysical and geochemical constraints on crustal accretion at the very‐slow spreading mohns ridge

Klingelhöfer

Géli

White³

2000

Geophysical Research Letters

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Section: Introductionmentioning

confidence: 99%

geophysical and geochemical constraints on crustal accretion at the very‐slow spreading mohns ridge

Klingelhöfer

Géli

White³

2000

Geophysical Research Letters

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“…Still, serpentinites are common in Atlantic fracture zones, along the Mid-Atlantic Ridge and elsewhere [e.g., Juteau et al, 1990], and there is a growing conviction among some researchers that serpentinites must constitute a volumetrically-significant fraction of crust produced at slowspreading ridges. Francis [1981], for example, reasoned that the lower crust (layer 3) along the Mid-Atlantic Ridge may be composed of serpentinized peridotire because the thickness of Copyright 1997 by the American Geophysical Union.…”

Section: Introductionmentioning

confidence: 99%

A new assessment of the abundance of serpentinite in the oceanic crust

Carlson

Miller

1997

Geophysical Research Letters

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Abstract.The 'gabbro' model of the composition of the oceanic crust has prevailed for more than two decades, but serpentinites are common along much of the Mid-Atlantic Ridge, and elsewhere, leading to renewed debate over the abundance of serpentinites in crust created at slow-spreading ridges. Based on data from both oceanic and ophiolite samples, it has also been suggested that serpentinites are not distinguishable from meta-gabbros and diabases by their seismic properties. We have made new statistical analyses of the relationship between V s and Vp in oceanic gabbro and diabase samples and serpentinized peridotires, and compared them to in situ s-wave and p-wave velocities derived from Expanding Spread Profiles (ESPs) acquired in the Atlantic. Our findings demonstrate: (1) that there is some overlap of the properties of gabbroic samples taken from ophiolites with the properties of serpentinites, but (2) over the range of typicallayer 3 seismic velocities, the seismic properties of oceanic gabbros and diabases are distinctly different from the properties of serpentinites, and (3) that in situ seismic velocities are in excellent agreement with the properties of the gabbros, while the shear velocities in serpentinites are significantly lower. Partially-serpentinized peridotire is certainly present, but not abundant in 'normal' oceanic crust.

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“…Fluid flow at mid-ocean ridges cools the oceanic lithosphere [Sclater et al, 1980], drives the biological and chemical evolution of hydrothermal systems [Murton et al, 1999], and controls the rheology and tectonics of the lithosphere [Francis, 1981]. Fluids 163 present in the mantle alter ultramafic rocks to serpentine, which can strongly influence the strength of the oceanic lithosphere [e. g., Escartin et al, 1997a;Moore et al, 1997].…”

Section: Introductionmentioning

confidence: 99%

Experimental and seismological constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers

deMartin¹

2007

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Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal accretion and extension. Experimental results from drained, triaxial deformation experiments on partially molten olivine reveal that melt extraction rates are linearly dependent on effective mean stress when the effective mean stress is low and non-linearly dependent on effective mean stress when it is high. Microearthquakes recorded above an inferred magma reservoir along the TAG segment of the Mid-Atlantic Ridge delineate for the first time the arcuate, subsurface structure of a long-lived, active detachment fault. This fault penetrates the entire oceanic crust and forms the high-permeability pathway necessary to sustain long-lived, high-temperature hydrothermal venting in this region. Long-lived detachment faulting exhumes lower crustal and mantle rocks. Residual stresses generated by thermal expansion anisotropy and mismatch in the uplifting, cooling rock trigger grain boundary microfractures if stress intensities at the tips of naturally occurring flaws exceed a critical stress intensity factor. Experimental results coupled with geomechanical models indicate that pervasive grain boundary cracking occurs in mantle peridotite when it is uplifted to within 4 km of the seafloor. Whereas faults provide the high-permeability pathways necessary to sustain high-temperature fluid circulation, grain boundary cracks form the interconnected network required for pervasive alteration of the oceanic lithosphere. This thesis provides fundamental constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers.

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Serpentinization faults and their role in the tectonics of slow spreading ridges

Cited by 142 publications

References 48 publications

geophysical and geochemical constraints on crustal accretion at the very‐slow spreading mohns ridge

geophysical and geochemical constraints on crustal accretion at the very‐slow spreading mohns ridge

A new assessment of the abundance of serpentinite in the oceanic crust

Experimental and seismological constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers

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