Magnetotelluric image of the fluid cycle in the Costa Rican subduction zone

Worzewski, Tamara; Jegen, Marion; Kopp, Heidrun; Brasse, Heinrich; Castillo, Waldo Taylor

doi:10.1038/ngeo1041

Cited by 154 publications

(142 citation statements)

References 25 publications

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“…Atg antigorite serpentinite, CPx clinopyroxene, OPx orthopyroxene, and Ol olivine. Olive symbols olivine aggregate and dark green symbols pyroxene-rich peridotite resolution of 2D electrical conductivity images has greatly improved (Wannamaker, et al 2014;Worzewski, et al 2011) with imaging of fluid paths that can be compared with seismic tomography. Typical values of conductivity range between 10 −3 and 10 −4 and 1 S.m 1 , the lower values being defined by the background sensitivity in cold and fluid-poor regions, and the highest observed in zones where fluids and melts are abundant.…”

Section: Magnetotelluricsmentioning

confidence: 99%

“…Magnetotellurics made great improvements in providing more accurate pictures of subduction zones from early studies that depicted rough limits between compartments of a few tens of kilometers to recent studies that give resolution of a few kilometers (Wannamaker, et al 2014;Worzewski, et al 2011). In the forearc region, the most prominent structures are high-conductivity zones that are located near the limit between the serpentinized mantle and the base of the overriding plate (Fig.…”

Section: Fluid Composition From Magnetotelluric Datamentioning

confidence: 99%

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Mantle hydration and Cl-rich fluids in the subduction forearc

Reynard

2016

Prog. in Earth and Planet. Sci.

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In the forearc region, aqueous fluids are released from the subducting slab at a rate depending on its thermal state. Escaping fluids tend to rise vertically unless they meet permeability barriers such as the deformed plate interface or the Moho of the overriding plate. Channeling of fluids along the plate interface and Moho may result in fluid overpressure in the oceanic crust, precipitation of quartz from fluids, and low Poisson ratio areas associated with tremors. Above the subducting plate, the forearc mantle wedge is the place of intense reactions between dehydration fluids from the subducting slab and ultramafic rocks leading to extensive serpentinization. The plate interface is mechanically decoupled, most likely in relation to serpentinization, thereby isolating the forearc mantle wedge from convection as a cold, potentially serpentinized and buoyant, body. Geophysical studies are unique probes to the interactions between fluids and rocks in the forearc mantle, and experimental constrains on rock properties allow inferring fluid migration and fluid-rock reactions from geophysical data. Seismic velocities reveal a high degree of serpentinization of the forearc mantle in hot subduction zones, and little serpentinization in the coldest subduction zones because the warmer the subduction zone, the higher the amount of water released by dehydration of hydrothermally altered oceanic lithosphere. Interpretation of seismic data from petrophysical constrain is limited by complex effects due to anisotropy that needs to be assessed both in the analysis and interpretation of seismic data. Electrical conductivity increases with increasing fluid content and temperature of the subduction. However, the forearc mantle of Northern Cascadia, the hottest subduction zone where extensive serpentinization was first demonstrated, shows only modest electrical conductivity. Electrical conductivity may vary not only with the thermal state of the subduction zone, but also with time for a given thermal state through variations of fluid salinity. High-Cl fluids produced by serpentinization can mix with the source rocks of the volcanic arc and explain geochemical signatures of primitive magma inclusions. Signature of deep high-Cl fluids was also identified in forearc hot springs. These observations suggest the existence of fluid circulations between the forearc mantle and the hot spring hydrothermal system or the volcanic arc. Such circulations are also evidenced by recent magnetotelluric profiles.

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Section: Magnetotelluricsmentioning

confidence: 99%

Section: Fluid Composition From Magnetotelluric Datamentioning

confidence: 99%

Mantle hydration and Cl-rich fluids in the subduction forearc

Reynard

2016

Prog. in Earth and Planet. Sci.

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“…In northwestern Costa Rica and southern Nicaragua, local earthquake seismic tomography data published by DeShon et al (2006) and Syracuse et al (2008), wide-angle refraction seismic by Sallarès et al (2001) and a magnetotelluric survey by Worzewski et al (2011) show a steeply dipping slab. For central Costa Rica, where the seamount segment of the Cocos plate subducts, local earthquake seismic tomography data by Husen et al (2003), Arroyo et al (2009) and Dinc et al (2010) show a shallower subduction angle.…”

Section: Tectonic Settingmentioning

confidence: 99%

Estado de esfuerzos estáticos en la interface de placas Coco-Caribe en Costa Rica: Interpretación mecánica para el origen de asperezas en la zona sismogénica

Lücke¹

2015

Rev. Geol. Amér. Central

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ABSTRACT:The forearc region along the Central American Subduction Zone shows a series of trench-parallel positive gravity anomalies with corresponding gravity lows along the trench and toward the coast. These features extend from Guatemala to northern Nicaragua. However, the Costa Rican section of the forearc does not follow this pattern due to the segmentation of the along-trench gravity low, the absence of the coastal low, and the presence of emerged continental mass along the forearc gravity high at the Nicoya Peninsula. Geodetic and seismological studies along the Costa Rican Subduction Zone suggest the presence of coupled areas in the seismogenic zone beneath the Nicoya Peninsula prior to the 7.6 Mw magnitude earthquake of September 5th, 2012. These areas have previously been associated with asperities. Based on the structure of the overriding plate, former publications have proposed a mechanical model for the origin of asperities along the Chilean convergent margin, in which the dense igneous material in the forearc of the overriding plate above the seismogenic zone modifies/disturbs the state of static stress and influences seismogenic processes. In Costa Rica, surface geology and gravity data indicate the existence of dense basalt/gabbro crust overlying the seismogenic zone where the coupling is present. Bouguer anomaly values in this region reach up to 120×10 -5 m/s 2 and are the highest for Costa Rica. In this research, the state of static stress on the Cocos-Caribbean plate interface is calculated based on the geometry and on the density distribution of a 3D litosphere density model of the subduction zone as interpreted from gravity data from combined geopotential models. Results show a spatial correlation between the coupled areas at the Nicoya Peninsula and the presence of anomalies on the static state of stress on the plate interface. The stress anomalies were calculated for the normal component of the vertical stress on the seismogenic zone and were interpreted as being generated by the dense material which makes up the forearc in the area.

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“…This approximation could have an impact on the anomaly pattern beneath the Principal Cordillera. The ocean and oceanic subducting plate were represented as 0.3 and 1000 Ωm bodies, respectively (Worzewski et al 2011;Brasse et al 2009). The resistivity of the ocean was fixed and the bathymetry included, while the top of the oceanic plate was based on the Slab 1.0 model (Hayes et al 2012), and its resistivity was allowed to change during the inversion.…”

Section: Data Acquisition and Processingmentioning

confidence: 99%

Preface

Kimura¹

2013

Earth Planets Space

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A profile of broadband magnetotelluric stations was acquired between 2009 and 2016 at 35°-36°S in the Southern Volcanic Zone of the Chilean Andes to image the subduction zone and its relation with the volcanic arc at this latitude. This transect extends from the Coastal Cordillera across the Central Valley and the volcanic arc of the Principal Cordillera to the Argentine border. Two active volcanic complexes are found along this profile: Tatara-San Pedro is located on the modern volcanic front, and the Laguna del Maule volcanic field is found approximately 30 km to the east. The latter exhibits considerable signs of unrest, such as uplift rates of up to 25 cm/year, and has produced a high concentration of silicic eruptions in the last 25 ky. The data covered the period range from 0.001 to 1000 s. Robust processing techniques were used, including remote reference, and dimensionality was investigated by estimation of geoelectric strike, skew and analysis of the induction arrows. The data were modeled using a 2D inversion algorithm to produce a resistivity model which was consistent with surface geology and seismicity. The final resistivity model shows a generally resistive fore-arc structure, coincident with the tectonic environment, and a wide conductive region from the volcanic front to the east. This suggests a broad region of magmatism throughout the arc, related to three distinct magma bodies, associated with the Tatara-San Pedro and Laguna del Maule volcanic complexes and the Mariposa Geothermal System.

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Magnetotelluric image of the fluid cycle in the Costa Rican subduction zone

Cited by 154 publications

References 25 publications

Mantle hydration and Cl-rich fluids in the subduction forearc

Mantle hydration and Cl-rich fluids in the subduction forearc

Estado de esfuerzos estáticos en la interface de placas Coco-Caribe en Costa Rica: Interpretación mecánica para el origen de asperezas en la zona sismogénica

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