Fluid and deformation regime of an advancing subduction system at Marlborough, New Zealand

Wannamaker, Philip E.; Caldwell, T. G.; Jiracek, George R.; Maris, Virginie; Hill, G. J.; Ogawa, Yasuo; Bibby, H. M.; Bennie, S. L.; Heise, Wiebke

doi:10.1038/nature08204

Cited by 202 publications

(159 citation statements)

References 32 publications

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“…Geophysical exploration results confirmed that a large number of high conductivity anomalies have been observed in metamorphic belts (Xiao et al, 2007;Wannamaker et al, 2009;Zeng et al, 2015). Metamorphic rocks (e.g., slate, schist, gneiss, granulite and eclogite) with different degrees of metamorphism play an important role because of their widespread distribution in regional metamorphic belts.…”

Section: Introductionsupporting

confidence: 56%

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Dai

Sun

et al. 2018

Solid Earth

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Abstract. The electrical conductivity of gneiss samples with different chemical compositions (W A = Na 2 O + K 2 O + CaO = 7.12, 7.27 and 7.64 % weight percent) was measured using a complex impedance spectroscopic technique at 623-1073 K and 1.5 GPa and a frequency range of 10 −1 to 10 6 Hz. Simultaneously, a pressure effect on the electrical conductivity was also determined for the W A = 7.12 % gneiss. The results indicated that the gneiss conductivities markedly increase with total alkali and calcium ion content. The sample conductivity and temperature conform to an Arrhenius relationship within a certain temperature range. The influence of pressure on gneiss conductivity is weaker than temperature, although conductivity still increases with pressure. According to various ranges of activation enthalpy (0.35-0.52 and 0.76-0.87 eV) at 1.5 GPa, two main conduction mechanisms are suggested that dominate the electrical conductivity of gneiss: impurity conduction in the lower-temperature region and ionic conduction (charge carriers are K + , Na + and Ca 2+ ) in the higher-temperature region. The electrical conductivity of gneiss with various chemical compositions cannot be used to interpret the high conductivity anomalies in the Dabie-Sulu ultrahigh-pressure metamorphic belt. However, the conductivity-depth profiles for gneiss may provide an important constraint on the interpretation of field magnetotelluric conductivity results in the regional metamorphic belt.

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Section: Introductionsupporting

confidence: 56%

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Dai

Sun

et al. 2018

Solid Earth

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“…Such complex tectonic settings suggest complex subsurface structures that may be related to the characteristic seismicity. Because electrical resistivity is sensitive to the presence of fluids, and subsequently the elasticity of the media, it is important to investigate how resistivity structures relate to earthquake generation Fujinawa et al 2002;Goto et al 2005;Guerer and Bayrak 2007;Wannamaker et al 2009;Yoshimura et al 2009;Ichihara et al 2011Ichihara et al , 2014Ichihara et al , 2016Ogawa et al 2014;Kaya et al 2013). To investigate the relationship between earthquakes and electrical resistivity structure, we gathered and analyzed the broadband (typically 0.003-10,000 s) magnetotelluric (MT) and telluric data, which resolve the resistivity structure from the surface to the depth of the upper mantle.…”

Section: Introductionmentioning

confidence: 99%

Seismicity controlled by resistivity structure: the 2016 Kumamoto earthquakes, Kyushu Island, Japan

Aizawa

Asaue

Koike

et al. 2017

Earth Planets Space

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The M JMA 7.3 Kumamoto earthquake that occurred at 1:25 JST on April 16, 2016, not only triggered aftershocks in the vicinity of the epicenter, but also triggered earthquakes that were 50-100 km away from the epicenter of the main shock. The active seismicity can be divided into three regions: (1) the vicinity of the main faults, (2) the northern region of Aso volcano (50 km northeast of the mainshock epicenter), and (3) the regions around three volcanoes, Yufu, Tsurumi, and Garan (100 km northeast of the mainshock epicenter). Notably, the zones between these regions are distinctively seismically inactive. The electric resistivity structure estimated from one-dimensional analysis of the 247 broadband (0.005-3000 s) magnetotelluric and telluric observation sites clearly shows that the earthquakes occurred in resistive regions adjacent to conductive zones or resistive-conductive transition zones. In contrast, seismicity is quite low in electrically conductive zones, which are interpreted as regions of connected fluids. We suggest that the series of the earthquakes was induced by a local accumulated stress and/or fluid supply from conductive zones. Because the relationship between the earthquakes and the resistivity structure is consistent with previous studies, seismic hazard assessment generally can be improved by taking into account the resistivity structure. Following on from the 2016 Kumamoto earthquake series, we suggest that there are two zones that have a relatively high potential of earthquake generation along the western extension of the MTL.

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“…In subduction zones, the subducting slab is the obvious fluid source, either by direct dewatering in the early subduction stage, or by hydration-dehydration reactions with increasing slab depth and increasing temperatures and pressures (e.g. Wannamaker et al 2010). Fluids released from the slab may percolate into the overlying mantle wedge, and farther into the lower crust, and account there for high conductivity anomalies.…”

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confidence: 99%

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Becken

Ritter

2011

Surv Geophys

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Fluids residing in interconnected porosity networks have a significant weakening effect on rheology of rocks and can strongly influence deformation along fault zones. The magnetotelluric (MT) technqiue is sensitive to interconnected fluid networks, and can image these zones on crustal and upper mantle scales. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, fault creep is supported. In response to fluid flux from deeper levels in combination with meteoric and crustal metamorphic fluid supply, and in response to fault creep, high-conductivity zones develop as fault zone conductors in the brittle portion of crust. In turn, the absence of crustal fluid pathays may be characteristic for mechanically locked segments. MT models suggest that those fluids are trapped at depth and kept at high pressures. It is speculated that fluids may infiltrate neighbouring rocks and induce non-volcanic tremor. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, strain provides a means to develop and maintain permeability structure, and thus electrical conductivity, within the damage zone. Accordingly, these conductivity models played an important role in pin-pointing the SAFOD drilling location near Parkfield. *abstractClick here to download abstract: abstract.txt Surv. Geophys. manuscript No.In this paper, we consider MT studies at the SAF near Hollister and Carrizo The SAF has also been a target for telluric (Madden et al. 1993;Park et al. 2007) and magnetotelluric monitoring (e.g. Kappler et al. 2010). These installations attempted to monitor long-term electric (and magnetic) field variations of internal origin due to resistivity variations assiciated with earthquakes, large scale fluid flow or other causes. To date, it was not possible to identify significant field variations which can be attributed to tectonic processes. In this paper, we don't discuss details of this issue. 7The main objective of this paper is to review the MT results from the SAF in combination with other geophysical, geological and geochemical data and models in order to address fluid-related processes and their potential implications on the geodynamic setting, active tectonic processes and the mechanical ...

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Fluid and deformation regime of an advancing subduction system at Marlborough, New Zealand

Cited by 202 publications

References 32 publications

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Effect of chemical composition on the electrical conductivity of gneiss at high temperatures and pressures

Seismicity controlled by resistivity structure: the 2016 Kumamoto earthquakes, Kyushu Island, Japan

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

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