Dimensionality imprint of electrical anisotropy in magnetotelluric responses

Martí, Anna; Queralt, Pilar; Ledo, Juanjo; Farquharson, Colin G.

doi:10.1016/j.pepi.2010.07.007

Cited by 36 publications

(15 citation statements)

References 36 publications

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“…For 2‐D isotropic Earth it should be perpendicular or parallel to the electrical strike. Therefore, the induction vector can be used to determine the electrical strike and to identify if the magnetotelluric responses are affected by electrical anisotropy and other interferences [ Jones , ; Pek and Verner , ; Heise and Pous , , ; Brasse et al ., ; Martí et al ., ]. The induction vector from the real part of the tipper [ Parkinson , ] should point toward to conductive body near the site.…”

Section: Magnetotelluric Datamentioning

confidence: 99%

“…We also noted that the impedance phases at two sites (14‐W15 and 14‐W16; Figure c) are significantly over 90°. The effect can be resulted from different causes [ Weckmann et al ., ; Heise and Pous , , ; Wannamaker , ; Brasse et al ., ; Martí et al ., ]. To get rid of this trouble, we excluded these two data sets in the following isotropic inversion.…”

Section: Magnetotelluric Datamentioning

confidence: 99%

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Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Yang

Sheng

et al. 2016

JGR Solid Earth

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The fate of subducted oceanic slabs can provide important clues to plate reconstruction through Earth history. Since oceanic slabs in continental collision zones are typically not well preserved, ancient subduction zones have rarely been imaged by geophysical techniques. Here we present an exception from the Darbut belt in the Junggar accretionary collage in the southern Altaids of Asia. We deployed a 182 km long magnetotelluric (MT) profile including 60 broadband sounding sites across the belt. Quality off‐diagonal impedances were inverted by a three‐dimensional scheme to image resistivities beneath the profile. The resistivity model along with MT impedance phase ellipses and induction vectors were tested and interpreted in detail. Combining geological and geophysical observations, mineral physical experiment, and geodynamic modeling results, the MT transect suggests a fossil intraoceanic subduction zone during the Late Paleozoic in the western Junggar that has been well preserved due to lack of significant subsequent tecto‐thermal events.

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Section: Magnetotelluric Datamentioning

confidence: 99%

Section: Magnetotelluric Datamentioning

confidence: 99%

Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Yang

Sheng

et al. 2016

JGR Solid Earth

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“…The cause of observed anisotropy, particularly for the mantle, is still debated, with hydrogen diffusion along olivine a-axes [Mackwell and Kohlstedt, 1990;Bahr and Duba, 2000;Gatzemeier and Tommasi, 2006;Jones et al, 2012] and interconnectivity of a conductive mineral phase (e.g., graphite) along grain boundaries [Jones et al, 1992;Mareschal et al, 1995], being the primary candidates for mantle materials. The presence of anisotropy in the lithosphere is increasingly being taken into account when undertaking MT interpretation [Baba et al, 2006;Martí et al, 2010;Evans et al, 2011;Le Pape et al, 2012] and can manifest itself in macroscale or microscale. Crustal anisotropy can result from different orientations of fluid-filled structures (i.e., strain-induced) or layering of materials with varying physical properties [Wannamaker, 2005;.…”

Section: Data Analysis and Decompositionmentioning

confidence: 99%

Lithospheric structure of an Archean craton and adjacent mobile belt revealed from 2‐D and 3‐D inversion of magnetotelluric data: Example from southern Congo craton in northern Namibia

et al. 2013

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[1] Archean cratons, and the stitching Proterozoic orogenic belts on their flanks, form an integral part of the Southern Africa tectonic landscape. Of these, virtually nothing is known of the position and thickness of the southern boundary of the composite Congo craton and the Neoproterozoic Pan-African orogenic belt due to thick sedimentary cover. We present the first lithospheric-scale geophysical study of that cryptic boundary and define its geometry at depth. Our results are derived from two-dimensional (2-D) and three-dimensional (3-D) inversion of magnetotelluric data acquired along four semiparallel profiles crossing the Kalahari craton across the Damara-Ghanzi-Chobe belts (DGC) and extending into the Congo craton. Two-dimensional and three-dimensional electrical resistivity models show significant lateral variation in the crust and upper mantle across strike from the younger DGC orogen to the older adjacent cratons. We find Damara belt lithosphere to be more conductive and significantly thinner than that of the adjacent Congo craton. The Congo craton is characterized by very thick (to depths of 250 km) and resistive (i.e., cold) lithosphere. Resistive upper crustal features are interpreted as caused by igneous intrusions emplaced during Pan-African magmatism. Graphite-bearing calcite marbles and sulfides are widespread in the Damara belt and account for the high crustal conductivity in the Central Zone. The resistivity models provide new constraints on the southern extent of the greater Congo craton and suggest that the current boundary drawn on geological maps needs revision and that the craton should be extended further south.

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“…Preliminary results from the study from Rödder and Junge (2012) shows how, by combining the information from the MT phase tensor and the DC apparent resistivity tensor, it is possible to identify uniquely the presence of anisotropy. Martí et al (2010) studied the imprints of anisotropic media responses in the WAL rotational invariants. The tests were made using synthetic 1D and 2D anisotropic models, computing the responses with the code of Pek and Verner (1997), and adding 1% random noise.…”

Section: Dimensionality Toolsmentioning

confidence: 99%

The Role of Electrical Anisotropy in Magnetotelluric Responses: From Modelling and Dimensionality Analysis to Inversion and Interpretation

Martí

2013

Surv Geophys

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The study of electrical anisotropy in the Earth, defined as the electrical conductivity varying with orientation, has experienced important advances in the last years regarding the investigation of its origins, how to identify and model it, and how it can be related to other parameters, such as seismic and mechanical anisotropy. This paper aims to provide a theoretical background and to be a review of the current state of the art of electrical anisotropy using electromagnetic methods in the frequency domain, focusing mainly on magnetotellurics. The aspects that will be considered are the modelling of the electromagnetic fields with anisotropic structures, the analysis of their responses to identify these structures, and how to properly use these responses in inversion and interpretation. Also, an update on the most recent case studies involving anisotropy is provided.

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Dimensionality imprint of electrical anisotropy in magnetotelluric responses

Cited by 36 publications

References 36 publications

Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Lithospheric structure of an Archean craton and adjacent mobile belt revealed from 2‐D and 3‐D inversion of magnetotelluric data: Example from southern Congo craton in northern Namibia

The Role of Electrical Anisotropy in Magnetotelluric Responses: From Modelling and Dimensionality Analysis to Inversion and Interpretation

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