scholarly journals Magnetotelluric multiscale 3-D inversion reveals crustal and upper mantle structure beneath the Hangai and Gobi-Altai region in Mongolia

2019 ◽  
Author(s):  
Johannes Käufl ◽  
Alexander Grayver ◽  
Matthew Comeau ◽  
Alexey Kuvshinov ◽  
Michael becken ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Mantle Structure ◽  
Altai Region ◽  
Upper Mantle Structure

scholarly journals Magnetotelluric multiscale 3-D inversion reveals crustal and upper mantle structure beneath the Hangai and Gobi-Altai region in Mongolia

2020 ◽  
Vol 221 (2) ◽  
pp. 1002-1028 ◽  
Author(s):  
J S Käufl ◽  
A V Grayver ◽  
M J Comeau ◽  
A V Kuvshinov ◽  
M Becken ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Data Acquisition ◽  
Upper Mantle ◽  
Spatial Scales ◽  
Mantle Structure ◽  
Central Mongolia ◽  
Altai Region ◽  
Upper Mantle Structure ◽  
Resistivity Model ◽  
And Inversion

SUMMARY Central Mongolia is a prominent region of intracontinental surface deformation and intraplate volcanism. To study these processes, which are poorly understood, we collected magnetotelluric (MT) data in the Hangai and Gobi-Altai region in central Mongolia and derived the first 3-D resistivity model of the crustal and upper mantle structure in this region. The geological and tectonic history of this region is complex, resulting in features over a wide range of spatial scales, which that are coupled through a variety of geodynamic processes. Many Earth properties that are critical for the understanding of these processes, such as temperature as well as fluid and melt properties, affect the electrical conductivity in the subsurface. 3-D imaging using MT can resolve the distribution of electrical conductivity within the Earth at scales ranging from tens of metres to hundreds of kilometres, thereby providing constraints on possible geodynamic scenarios. We present an approach to survey design, data acquisition, and inversion that aims to bridge various spatial scales while keeping the required field work and computational cost of the subsequent 3-D inversion feasible. MT transfer functions were estimated for a 650 × 400 km2 grid, which included measurements on an array with regular 50 × 50 km2 spacing and along several profiles with a denser 5–15 km spacing. The use of telluric-only data loggers on these profiles allowed for an efficient data acquisition with a high spatial resolution. A 3-D finite element forward modelling and inversion code was used to obtain the resistivity model. Locally refined unstructured hexahedral meshes allow for a multiscale model parametrization and accurate topography representation. The inversion process was carried out over four stages, whereby the result from each stage was used as input for the following stage that included a finer model parametrization and/or additional data (i.e. more stations, wider frequency range). The final model reveals a detailed resistivity structure and fits the observed data well, across all periods and site locations, offering new insights into the subsurface structure of central Mongolia. A prominent feature is a large low-resistivity zone detected in the upper mantle. This feature suggests a non-uniform lithosphere-asthenosphere boundary that contains localized upwellings that shallow to a depth of 70 km, consistent with previous studies. The 3-D model reveals the complex geometry of the feature, which appears rooted below the Eastern Hangai Dome with a second smaller feature slightly south of the Hangai Dome. Within the highly resistive upper crust, several conductive anomalies are observed. These may be explained by late Cenozoic volcanic zones and modern geothermal areas, which appear linked to mantle structures, as well as by major fault systems, which mark terrane boundaries and mineralized zones. Well resolved, heterogeneous low-resistivity zones that permeate the lower crust may be explained by fluid-rich domains.

LASA anomalies and their relations to crust and upper-mantle structure

1970 ◽  
Author(s):  
H.M. Iyer ◽  
A.R. Jackson ◽  
J.H. Healy ◽  
T.E. Landers
Keyword(s):  
Upper Mantle ◽  
Mantle Structure ◽  
Crust And Upper Mantle ◽  
Upper Mantle Structure

scholarly journals Upper mantle structure of eastern Asia from multimode surface waveform tomography

2006 ◽  
Vol 111 (B10) ◽  
Author(s):  
Keith Priestley ◽  
Eric Debayle ◽  
D. McKenzie ◽  
S. Pilidou
Keyword(s):  
Upper Mantle ◽  
Mantle Structure ◽  
Eastern Asia ◽  
Upper Mantle Structure ◽  
Waveform Tomography

Upper mantle structure of the western United States

1973 ◽  
Vol 78 (11) ◽  
pp. 1870-1880 ◽  
Author(s):  
Ralph A. Wiggins ◽  
Donald V. Helmberger
Keyword(s):  
United States ◽  
Upper Mantle ◽  
Western United States ◽  
Mantle Structure ◽  
Upper Mantle Structure

Higher Modes of Rayleigh Waves and Upper Mantle Structure

1972 ◽  
pp. 93-100 ◽  
Author(s):  
V. I. Frantsuzova ◽  
A. L. Levshin ◽  
G. V. Shkadinskaya
Keyword(s):  
Upper Mantle ◽  
Rayleigh Waves ◽  
Mantle Structure ◽  
Higher Modes ◽  
Upper Mantle Structure
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