A Review of Recent Developments in the Study of Regional Lithospheric Electrical Structure of the Asian Continent

Zhang, Letian

doi:10.1007/s10712-017-9424-4

Cited by 15 publications

(10 citation statements)

References 104 publications

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“…A similar combination of channelized fluid and melt, aligned with the direction of lower‐crustal deformation, is inferred beneath the eastern Tibetan plateau (Bai et al, ). Three‐dimensional studies observing anisotropy are rare, though we note that 3‐D isotropic inverse models covering the entire Tibetan plateau reveal alternating conductive and resistive stripes in the lower crust (Zhang, ), similar to our observations.…”

Section: Source Of Lower‐crustal Conductivity and Anisotropysupporting

confidence: 86%

Crustal Magmatism and Anisotropy Beneath the Arabian Shield—A Cautionary Tale

et al. 2019

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Volcanism in Saudi Arabia includes a historic eruption close to the holy city of Al Madinah. As part of a volcanic hazard assessment of this area, magnetotelluric (MT) data were collected to investigate the structural setting, the distribution of melt within the crust, and the mantle source of volcanism. Interpretation of a new 3-D resistivity model includes a shallow graben beneath thin lava fields (Harrats), a melt-free upper crust, and decompression melting in the asthenosphere below thin lithosphere. Within the lower crust the model images elongate conductivity anomalies, one of which was attributed in a previous MT study to melt. The regional MT data, combined with perspective from geology and geophysical modeling, suggest the lower crust is anisotropic with no interconnected melt zones. These divergent interpretations have distinct hazard implications and highlight the importance of large survey aperture and anisotropic modeling to MT studies of volcanic regions. Lower-crustal anisotropy extends beyond the Harrat, with the most conductive direction oriented N10°E and a factor of 3-5, determined from 2-D anisotropic inversion, between the most and least conductive directions. The enhanced conductivity is likely due to interconnected grain boundary graphite, while the anisotropy direction reflects either frozen-in fabric from Neoproterozoic stabilization of the Arabian Shield or modern ductile deformation driven by channelized asthenospheric flow coupled through a thin rigid mantle lid. Asthenospheric melt is interpreted to transect the crust primarily through diking, with limited melt storage and short residence times in the crust.Plain Language Summary Volcanism within the lava fields, or Harrats, of Saudi Arabia includes historic eruptions, such as an eruption in 1256 CE near the holy city of Al Madinah. As part of a volcanic hazard assessment of northern Harrat Rahat, geophysical studies produced a three-dimensional model of electrical resistivity of the crust and upper mantle. In contrast to a more local study, the model shows no evidence of magma in the crust. This is consistent with other evidence in the region that suggests magma does not stay in the crust for long times but ascends rapidly from the upper mantle to the surface. This finding provides a snapshot in the lifecycle of this volcanic field and is important to understanding the hazards it poses. Our model also finds deep electrical anisotropy, probably due to a preferred direction or "fabric" in the lower crust. This fabric may be ancient, frozen in millions of years ago when the crust formed. Alternately, it may be caused by ongoing flow in the ductile lower crust in response to deeper mantle flow.

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Section: Source Of Lower‐crustal Conductivity and Anisotropysupporting

confidence: 86%

Crustal Magmatism and Anisotropy Beneath the Arabian Shield—A Cautionary Tale

et al. 2019

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“…The conductive layers in this study are located mostly in the Lhasa terrane. Previous studies (Dong et al, 2016;Jin, 2009;Le Pape et al, 2015;Liang et al, 2018;Unsworth et al, 2005;Zhang, 2017) indicated that the conductive layers in the southern Tibetan Plateau may be caused by partial melting and/or aqueous fluids, and possibly related to mineralization in the Gangdese metallogenic belt (Sheng, Jin, Liang, et al, 2019;Wang et al, 2017b). The subducted Indian lithospheric mantle beneath the present-day Lhasa terrane is generally considered to be formed of anhydrous eclogite, and thus cannot supply additional water for the lower crust (Nábělek & Nábělek, 2014).…”

Section: Estimating Water Contentmentioning

confidence: 99%

“…The water content and the content of carbon dioxide (CO 2 ) in the lithospheric mantle must also be taken into consideration. According to previous studies the water content is estimated to be 100 ppm and the amount of carbon dioxide is estimated to be 0.82 times the water content (Katz et al, 2003;Vozar et al, 2014;Zhang, 2017).…”

Section: Estimating Pressure and Temperaturementioning

confidence: 99%

Lithospheric Structure Near the Northern Xainza‐Dinggye Rift, Tibetan Plateau–Implications for Rheology and Tectonic Dynamics

et al. 2021

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“…Widespread thermal springs might be one of the reasonable explanations for shallow sporadic conductors. Using SinoProbe MT array data in Tibet, this thick resistive cover was also imaged in recent studies (Dong et al, 2016(Dong et al, , 2020Zhang, 2017).…”

Section: Resistivity Modelmentioning

confidence: 99%

“…Seismic and magnetotelluric (MT) data could be used as constraints to understand subsurface structures and the physical states of the lithosphere beneath the Himalayan‐Tibetan orogen (Brown et al., 1996; Dong et al., 2020; Gao et al., 2016; Kind et al., 1996, 2002; Makovsky & Klemperer, 1999; Makovsky et al., 1996; J. Nabelek et al., 2009; Nelson et al., 1996; Pham et al., 1986; X. Tian, Chen, et al., 2015; Unsworth et al., 2005; Wei et al., 2001; Zhang, 2017). The features of crustal high electrical conductivity and low seismic velocity have been highlighted in most previous studies.…”

Section: Introductionmentioning

confidence: 99%

Middle Crustal Partial Melting Triggered Since the Mid‐Miocene in Southern Tibet: Insights From Magnetotelluric Data

et al. 2021

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A weak middle crust induced by fluid phases is generally considered to exist beneath the Himalayan‐Tibetan orogen; however, there remains controversy regarding the interpretation of high‐conductivity and low‐velocity regions imaged in various geophysical studies. To better understand middle crustal rheological behaviors and associated triggering mechanisms beneath southern Tibet, we present a geoelectrical model derived from a three‐dimensional magnetotelluric inversion in this study. An effective conductivity of 0.3 S/m at depths of 10–28 km indicates a high melt fraction of ∼35 vol% in the Lhasa terrane. In the Tethyan Himalayan orogen, an effective conductivity of <0.2 S/m corresponds to a melt fraction <15 vol%, which is lower than previous estimations. We obtain very low viscosities either from laboratory data (1010–1012 Pa s) or empirical models (1016–1018 Pa s). A combination of radiogenic heat and strain heating may account for the weakened middle crust. We prefer a weak coupling between crustal east‐west extensions and mantle lithospheric deformations.

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A Review of Recent Developments in the Study of Regional Lithospheric Electrical Structure of the Asian Continent

Cited by 15 publications

References 104 publications

Crustal Magmatism and Anisotropy Beneath the Arabian Shield—A Cautionary Tale

Crustal Magmatism and Anisotropy Beneath the Arabian Shield—A Cautionary Tale

Lithospheric Structure Near the Northern Xainza‐Dinggye Rift, Tibetan Plateau–Implications for Rheology and Tectonic Dynamics

Middle Crustal Partial Melting Triggered Since the Mid‐Miocene in Southern Tibet: Insights From Magnetotelluric Data

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