Seismic Properties of Serpentinized Peridotite from the Mariana Forearc

Ballotti, Dean M; Christensen, Nikolas I.; Becker, Keir

doi:10.2973/odp.proc.sr.125.161.1992

Cited by 6 publications

(2 citation statements)

References 22 publications

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“…The serpentine mudflow material is less dense than surrounding peridotite (Ballotti et al 1992) and should tend to rise because of gravitational instability, but a mixture of serpentinized fault gouge and slab-derived fluids would not be strong enough (e.g., Phipps & Ballotti 1992) to push, diapirically, through surrounding massive peridotite. A conduit for the rise of the serpentinite mud must be created, and extensional deformation is required for an eruption to be initiated.…”

Section: Seismicity As An Eruptive Trigger?mentioning

confidence: 99%

Serpentinite Mud Volcanism: Observations, Processes, and Implications

Fryer

2012

Annu. Rev. Mar. Sci.

114

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Large serpentinite mud volcanoes form on the overriding plate of the Mariana subduction zone. Fluids from the descending plate hydrate (serpentinize) the forearc mantle and enable serpentinite muds to rise along faults to the seafloor. The seamounts are direct windows into subduction processes at depths far too deep to be accessed by any known technology. Fluid compositions vary with distance from the trench, signaling changes in chemical reactions as temperature and pressure increase. The parageneses of rocks in the mudflows permits us to constrain the physical conditions of the decollement region. If eruptive episodes are related to seismicity, seafloor observatories at these seamounts hold the potential to capture a subduction event and trace the effects of eruption on the biological communities that the slab fluids support, such as extremophile Archaea. The microorganisms that inhabit this high-pH, extreme environment support their growth by utilizing chemical constituents present in the slab fluids. Some researchers now contend that the serpentinization process itself may hold the key to the origin of life on Earth.

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Section: Seismicity As An Eruptive Trigger?mentioning

confidence: 99%

Serpentinite Mud Volcanism: Observations, Processes, and Implications

Fryer

2012

Annu. Rev. Mar. Sci.

114

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“…The crustal thicknesses determined for the Caribbean and plateau localities in Table 4 (Table 4). Velocities under-3.5 km/s are most likely to represent sedimentary rock, although Ballotti et al [1992] demonstrated that elevated porosity can significantly reduce velocity in serpentinite, and some shipboard velocity measurements of serpentinite recovered during DSDP Leg 84 off Guatemala were in this range [von Huene et al, 1985].…”

Section: Comparison With Other Marginsmentioning

confidence: 99%

Structure of the Costa Rica convergent margin, offshore Nicoya Peninsula

Christeson¹,

McIntosh²,

Shipley³

et al. 1999

J. Geophys. Res.

108

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Abstract. We present the results of a seismic refraction survey conducted offshore Costa Rica near the Nicoya Peninsula. A dip profile and three strike profiles were carried out over 22 ocean bottom hydrophones and seismographs and were also recorded by land receivers. These data are used to construct a crustal structure model of the convergent margin from 20 km seaward of the Middle America Trench onto the Nicoya Peninsula. The best constrained portion of our model is the velocity at the top of the margin wedge immediately below the slope apron. Velocities increase from 3.5 to 4.2 to 4.6 km/s at distances of 10, 20, and 30-50 km landward of the trench.These velocities are higher than observed within margin wedges at other well-studied convergent margins but lower than the velocities within the adjacent Nicoya Complex, which are --5.5 km/s at similar depths below the surface. We interpret the margin wedge velocities as indicating that material similar to the Nicoya Complex extends seaward to near the lower slope but that fracturing, alteration, or accretion processes have lowered the velocity of the margin wedge with respect to the Nicoya Complex. The seismic refraction data cannot constrain the exact thickness or velocity of a possible low-velocity zone (LVZ) overlying the subducting plate; however, geologically reasonable structures are only produced with a LVZ <400 m thick. Velocities in the upper part of oceanic layer 2 are-•3.5-4.0 km/s within the subducting slab. These velocities are unusually low for oceanic crust of this age and may correlate with a proposed highly permeable zone at the top of the subducting crust. The top of the subducted slab is well resolved, and deepens from 5 km depth at the trench to 15-16 km depth at the Nicoya Peninsula coastline. The dip angle of the subducting plate increases from 6 ø to 13 ø at a distance of-30 km from the trench. Interplate seismicity appears to become common-•55 km from the trench where the plate boundary is at-•14 km depth.

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The Identity of Petrophysical Properties of Oceanic Serpentinites and Continental Granitoids: Implications for the Recognition of Buried Hydrocarbon-bearing Serpentinite Geobodies

Manuella

Carbone

2019

Geotecton.

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Seismic Properties of Serpentinized Peridotite from the Mariana Forearc

Cited by 6 publications

References 22 publications

Serpentinite Mud Volcanism: Observations, Processes, and Implications

Serpentinite Mud Volcanism: Observations, Processes, and Implications

Structure of the Costa Rica convergent margin, offshore Nicoya Peninsula

The Identity of Petrophysical Properties of Oceanic Serpentinites and Continental Granitoids: Implications for the Recognition of Buried Hydrocarbon-bearing Serpentinite Geobodies

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