Seismogenic structures in western Yunnan revealed by three-dimensional magnetotelluric imaging

2020 ◽  
Author(s):  
Qinghua Huang ◽  
Tao Ye ◽  
Xiaobin Chen
Keyword(s):  
Three Dimensional ◽  
Magnetotelluric Data ◽  
Block Boundary ◽  
Strong Earthquakes ◽  
Yunnan Region ◽  
Continental Block ◽  
Western Yunnan ◽  
Resistivity Model ◽  
Seismogenic Structures ◽  
Magnetotelluric Imaging

<p>Influenced by the extrusion of Tibetan blocks and Indo-Burmese collision, the region in western Yunnan is associated with active seismicity and Quaternary volcanoes. Based on broadband magnetotelluric data collected in western Yunnan, we obtain a three-dimensional crustal electrical resistivity model after various data processing and three-dimensional inversion test. The above resistivity model reveals the seismogenic structures of the moderate and strong earthquakes in this tectonic region. We investigate the possible relationship between the seismicity and the electrical structure in western Yunnan region. The results indicate that earthquakes in this region tend to occur in the transition zone between the resistive and conductive structures. Our results also show that one resistive body imaged at the mid-lower crust may have blocked the previously proposed crustal channel flow along this intra-continental block boundary to the east of Tibetan Plateau. Our resistivity model suggests a bifurcation of the crustal flow in western Yunnan. This bifurcated crustal flow structure may play an important dynamical role in the seismogenesis of the earthquakes in western Yunnan.</p>

Three‐dimensional inversion of magnetotelluric data for a resistivity model with arbitrary anisotropy

2021 ◽  
Author(s):  
Wenxin Kong ◽  
Handong Tan ◽  
Changhong Lin ◽  
Martyn Unsworth ◽  
Benjamin Lee ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Magnetotelluric Data ◽  
Resistivity Model ◽  
Arbitrary Anisotropy

Deep electrical structure of northern Alberta (Canada): implications for diamond exploration

2009 ◽  
Vol 46 (2) ◽  
pp. 139-154 ◽  
Author(s):  
Erşan Türkoğlu ◽  
Martyn Unsworth ◽  
Dinu Pana
Keyword(s):  
Subduction Zone ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Three Dimensional ◽  
Diamond Formation ◽  
Magnetotelluric Data ◽  
Diamond Exploration ◽  
Upper Mantle Structure ◽  
Resistivity Model ◽  
Northern Alberta

Geophysical studies of upper mantle structure can provide constraints on diamond formation. Teleseismic and magnetotelluric data can be used in diamond exploration by mapping the depth of the lithosphere–asthenosphere boundary. Studies in the central Slave Craton and at Fort-à-la-Corne have detected conductors in the lithospheric mantle close to, or beneath, diamondiferous kimberlites. Graphite can potentially explain the enhanced conductivity and may imply the presence of diamonds at greater depth. Petrologic arguments suggest that the shallow lithospheric mantle may be too oxidized to contain graphite. Other diamond-bearing regions show no upper mantle conductor suggesting that the correlation with diamondiferous kimberlites is not universal. The Buffalo Head Hills in Alberta host diamondiferous kimberlites in a Proterozoic terrane and may have formed in a subduction zone setting. Long period magnetotelluric data were used to investigate the upper mantle resistivity structure of this region. Magnetotelluric (MT) data were recorded at 23 locations on a north–south profile extending from Fort Vermilion to Utikuma Lake and an east–west profile at 57.2°N. The data were combined with Lithoprobe MT data and inverted to produce a three-dimensional (3-D) resistivity model with the asthenosphere at 180–220 km depth. This model did not contain an upper mantle conductor beneath the Buffalo Head Hills kimberlites. The 3-D inversion exhibited an eastward dipping conductor in the crust beneath the Kiskatinaw terrane that could represent the fossil subduction zone that supplied the carbon for diamond formation. The low resistivity at crustal depths in this structure is likely due to graphite derived from subducted organic material.

scholarly journals Electrical resistivity modeling around the Hidaka collision zone, northern Japan: regional structural background of the 2018 Hokkaido Eastern Iburi earthquake (Mw 6.6)

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Hiroshi Ichihara ◽  
Toru Mogi ◽  
Hideyuki Satoh ◽  
Yusuke Yamaya
Keyword(s):  
Three Dimensional ◽  
High Resistivity ◽  
Reverse Fault ◽  
Magnetotelluric Data ◽  
Epicentral Area ◽  
Collision Zone ◽  
Conductive Zone ◽  
Significant Area ◽  
Resistivity Model ◽  
Hidaka Collision Zone

Abstract The Hidaka collision zone, the collision boundary between the NE Japan and Kurile arcs, is known to be an ideal region to study the evolution of island arcs. The hypocenter of the 2018 Hokkaido Eastern Iburi earthquake (Mw 6.6) in the western part of the Hidaka collision zone was unusually deep for an inland earthquake, and the reverse fault that caused the earthquake has an uncharacteristically steep dip. In this study, we used three-dimensional inversion to reanalyze broadband magnetotelluric data acquired in the collision zone. The inverted resistivity model showed a significant area of high resistivity around the center of the collision boundary. We also identified a conductive zone beneath an area of serpentinite mélange in a zone of high P–T metamorphic rocks west of the high-resistivity zone. The conductive zone possibly reflects areas rich in pore fluids related to the formation and elevation of the serpentinites. Sensitivity tests indicated the need for additional magnetotelluric survey data to delineate the resistivity distribution around the epicentral area of the 2018 earthquake although the resistivity model showed a conductive zone in this area.

Three-dimensional inversion of controlled-source audio-frequency magnetotelluric data based on unstructured finite-element method

2020 ◽  
Vol 17 (3) ◽  
pp. 349-360
Author(s):  
Xiang-Zhong Chen ◽  
Yun-He Liu ◽  
Chang-Chun Yin ◽  
Chang-Kai Qiu ◽  
Jie Zhang ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
Audio Frequency ◽  
Magnetotelluric Data ◽  
Controlled Source ◽  
Element Method

scholarly journals Crustal architecture of a metallogenic belt and ophiolite belt: implications for mineral genesis and emplacement from 3-D electrical resistivity models (Bayankhongor area, Mongolia)

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Matthew J. Comeau ◽  
Michael Becken ◽  
Alexey V. Kuvshinov ◽  
Sodnomsambuu Demberel
Keyword(s):  
Electrical Resistivity ◽  
Crustal Structure ◽  
Three Dimensional ◽  
Suture Zone ◽  
Fault System ◽  
Magnetotelluric Data ◽  
Low Resistivity ◽  
Ophiolite Belt ◽  
Geological Processes ◽  
Metallogenic Belt

AbstractCrustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust (< 25 km) is found to be generally highly resistive (> 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture—including the major crustal boundary—acts as a first‐order control on the location of the metallogenic belt.

scholarly journals Concealed porphyry delineation based on nonlinear three-dimensional density-difference inversion: An example in the Beiya mine area, Western Yunnan, China

China Geology ◽  
2019 ◽  
Vol 2 (3) ◽  
pp. 340-351
Author(s):  
Jian Yang ◽  
◽  
Sheng-xian Liang ◽  
Qiao Wang ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Density Difference ◽  
Mine Area ◽  
Western Yunnan

Magnetotelluric imaging of a fossil oceanic plate in northwestern Xinjiang, China

Geology ◽  
2020 ◽  
Vol 48 (4) ◽  
pp. 385-389 ◽  
Author(s):  
Y.X. Xu ◽  
B. Yang ◽  
A.Q. Zhang ◽  
S.C. Wu ◽  
L. Zhu ◽  
...  
Keyword(s):  
Subcontinental Lithospheric Mantle ◽  
Oceanic Plate ◽  
Continental Lithosphere ◽  
Magnetotelluric Data ◽  
Long Period ◽  
Continental Plate ◽  
Formation And Evolution ◽  
Magnetotelluric Imaging ◽  
Plate Subduction ◽  
Continental Accretion

Abstract Because an oceanic plate colliding with a continental plate will usually be subducted and recycled into the deep mantle, a fossil oceanic plate after the closure of an ancient ocean has rarely been imaged in the subcontinental lithospheric mantle. This has led to a long-standing debate about the fate of subducted ocean plates. The problem can be addressed by imaging the lithosphere in a continental accretion zone with past ocean subduction. We present a study using long-period magnetotelluric data that reveals a large shallow-mantle conductor in a Phanerozoic accretion area in northwestern Xinjiang, China. This conductor extends &gt;300 km laterally at depths from 120 to 220 km and resembles a segment of a fossil oceanic plate. The reduced resistivity is ascribed to the volatile-bearing metasomatic minerals, based on its relatively fertile nature and low temperature. Our results demonstrate that an oceanic plate can be trapped in continental lithosphere, underscoring the significance of oceanic plate subduction to continental accretion, and shedding new light on our understanding of continental formation and evolution.

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