scholarly journals Crustal Electrical Structure of the Zhaheba Complex Imaged by Magnetotelluric Data and Its Tectonic Implications

2021 ◽  
Vol 11 (21) ◽  
pp. 10013
Author(s):  
Pingchuan Zhang ◽  
Changqing Yu ◽  
Xiangzhi Zeng
Keyword(s):  
Junggar Basin ◽  
High Resistivity ◽  
Precambrian Basement ◽  
Structure And Properties ◽  
Uppermost Mantle ◽  
Magnetotelluric Data ◽  
Northern Margin ◽  
Electrical Structure ◽  
Low Resistivity ◽  
Intrusive Rocks

A Magnetotelluric profile stretching northward from the Wulungu Depression (on the northern margin of the Junggar Basin) to the Dulate arc (crossing the Zhaheba–Aermantai ophiolite belt) was carried out in an attempt to probe the crustal structure and properties of the East Junggar, NW China. Along the profile, the inversion model was used to determine the electrical structure of the crust and uppermost mantle. The results revealed that the crust of the eastern Junggar Basin is composed of the shallow low resistivity layer and underlying high resistivity bodies. There is a crustal detachment in the basement: the upper layer is a Hercynian folded basement and the lower is a Precambrian basement. The Zhaheba complex is characterized by relatively high resistivity, with a thickness of ~5 km, the bottom controlled by the Zhaheba–Aermantai fault. The crust of the Yemaquan arc is composed of the residual continental crust, characterized by stable resistance. The exposed intrusive rocks are characterized by irregular resistors. The crust of the Dulate arc is characterized by relatively low resistivity. The shallow low resistivity layers represent the Zhaheba depression composed of the Devonian-Permian volcanic and sedimentary rocks. The crustal conductive anomalies are related to the magmatism and mechanism of metal deposits in the post-collision period.

Magnetotelluric observations in the western Ouachita Mountains, southeastern Oklahoma

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1680-1688 ◽  
Author(s):  
Kevin L. Mickus
Keyword(s):  
Drill Hole ◽  
High Resistivity ◽  
Geologic Mapping ◽  
Gulf Coastal Plain ◽  
Ouachita Mountains ◽  
Arkoma Basin ◽  
Magnetotelluric Data ◽  
Low Resistivity ◽  
Northern Border ◽  
Seismic Reflection Profiles

The first magnetotelluric (MT) analysis of the Ouachita Mountains region is presented. Magnetotelluric data acquired at 19 sites along a 60-km profile in southeastern Oklahoma were used to image the western extension of the Ouachita Mountains and to determine the poorly known subsurface interaction between the Pennsylvanian Tishomingo‐Belton uplift and the subsurface extension of the exposed western Ouachita Mountains. Drill‐hole data, geologic mapping, seismic reflection profiles, and 1-D and 2-D MT-derived models indicate that lying beneath the low‐resistivity Gulf Coastal Plain sediments are 2–3 km of deep‐water lower Pennsylvanian (Jackfork Group) sediments and 6–8 km of Ouachita facies lithologies, mainly consisting of the Stanley Group. Beneath the profile’s northern section are 2–4 km of Atoka Formation sediments, probably deposited within the Arkoma basin, that underlie thrusted zones of the Stanley Group. The most unique feature is a high‐resistivity zone beneath stations 7–9, interpreted to be Precambrian/Cambrian granite similar to that exposed in the Tishomingo‐Belton uplift. A deep (5–6 km) low‐resistivity zone that may represent the northern border of the subsurface extension of the Broken Bow uplift is located along the Texas/Oklahoma border; however, this zone is not required by the MT data.

scholarly journals Identification of "WS" geothermal field system by analyzing TE, TM, and TE-TM of 2D magnetotelluric inversion models

2019 ◽  
Vol 1 (2) ◽  
pp. 41
Author(s):  
Triana Triana ◽  
Tony Yulianto ◽  
Udi Harmoko ◽  
Iqbal Takodama
Keyword(s):  
Geothermal Field ◽  
Reservoir Rock ◽  
High Resistivity ◽  
Geothermal System ◽  
Magnetotelluric Data ◽  
Low Resistivity ◽  
A Value ◽  
Te Mode ◽  
Tm Mode ◽  
Representative Model

Magnetotelluric data has been carried out at the "WS" geothermal field to analyze the resistivity model resulting from 2D inversion of magnetotelluric data in TE, TM and TE-TM modes. Base on the three models produced, the mode is determined to produce the most representative model to assist in the interpretation of the "WS" geothermal system. There is a step of modes separation, namely TE (Tranverse Electric) and TM (Transverse Magnetic) modes in processing MT data. Each mode produces a 2D model with different conductivity properties. The analysis results of the three modes explain that TE mode is dominated by low resistivity with a range of values of 10-35 Ωm and medium resistivity with a value range of 35-250 Ωm and a vertical resistivity contrast. The TM mode describes the high resistivity in the Southwest and the center of the track with a value of more than 470 sehinggam resulting in lateral resistivity contrast. While the TE-TM mode produces a model that is not much different from TM mode, only the distribution of the resistivity value is a combination with TE mode. This mode describes the distribution of resistivity both vertically and laterally. Based on the analysis of the three modes, it can be concluded that the TE-TM mode is the mode that produces the most representative model. Interpretation model shows that from the TE-TM mode we have a low resistivity distribution (10-35 Ωm) represent a cap rock zone, reservoir rock with a medium resistivity distribution (35-380 Ωm), resistive zone with a high resistivity distribution (more than 380 Ωm), and the existence of the three of faults structures ro be a controller system of the "WS" geothermal.

Geophysical characterization of the Menengai volcano, Central Kenya Rift from the analysis of magnetotelluric and gravity data

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. B187-B199 ◽  
Author(s):  
Antony Munika Wamalwa ◽  
Kevin L. Mickus ◽  
Laura F. Serpa
Keyword(s):  
Gravity Data ◽  
Gravity Models ◽  
High Resistivity ◽  
Geothermal System ◽  
Low Density ◽  
Fracture Density ◽  
Density Region ◽  
Magnetotelluric Data ◽  
Low Resistivity ◽  
2D Resistivity

In this study, we qualitatively analyze detailed gravity and broadband magnetotelluric data in and surrounding the Menengai volcano of the East African rift in Kenya to assess geothermal potential of the region. Three-dimensional gravity models obtained by inverting residual gravity anomalies and 2D resistivity models obtained by inverting the transverse electric and transverse magnetic magnetotelluric modes show several common features. Our models show that a low-resistivity zone above a higher resistivity zone correlates with a low-density region located 1–4 km beneath the volcano. These zones may be related to a high temperature gradient or hydrothermally altered, fractured rocks. Additionally, a low-resistivity ([Formula: see text]) and a low-density region located approximately 4–6 km below the volcano may be related to molten material that is the source of heat for the geothermal system. The low-resistivity ([Formula: see text]) regions that correlated with a denser ([Formula: see text]) region within the caldera are bounded by high-resistivity ([Formula: see text]), high-density ([Formula: see text]) volcanic units implying that the dense and electrically resistive volcanic material is relatively cool and lacks significant fluid content that can lower resistivity. At shallow depths, 0.5–1.5 km below the caldera, a low-resistivity and low-to-moderate density region is interpreted as a zone with high fracture density that consists of clay minerals resulting from hydrothermal alteration. These results agree well with the results from previous seismic studies on the depth of the suggested molten rocks.

scholarly journals Studying the Depth Structure of the Kyrgyz Tien Shan by Using the Seismic Tomography and Magnetotelluric Sounding Methods

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 122
Author(s):  
Irina Medved ◽  
Elena Bataleva ◽  
Michael Buslov
Keyword(s):  
Seismic Tomography ◽  
High Velocity ◽  
Fault Zones ◽  
Magnetotelluric Sounding ◽  
Tien Shan ◽  
High Resistivity ◽  
Low Velocity ◽  
Low Resistivity ◽  
Velocity Models ◽  
Fluid Saturation

This paper presents new results of detailed seismic tomography (ST) on the deep structure beneath the Middle Tien Shan to a depth of 60 km. For a better understanding of the detected heterogeneities, the obtained velocity models were compared with the results of magnetotelluric sounding (MTS) along the Kekemeren and Naryn profiles, running parallel to the 74 and 76 meridians, respectively. We found that in the study region the velocity characteristics and geoelectric properties correlate with each other. The high-velocity high-resistivity anomalies correspond to the parts of the Tarim and Kazakhstan-Junggar plates submerged under the Tien Shan. We revealed that the structure of the Middle Tien Shan crust is conditioned by the presence of the Central Tien Shan microcontinent. It manifests itself as two anomalies lying one below the other: the lower low-velocity low-resistivity anomaly, and the upper high-velocity high-resistivity anomaly. The fault zones, limiting the Central Tien Shan microcontinent, appear as low-velocity low-resistivity anomalies. The obtained features indicate the fluid saturation of the fault zones. According to the revealed features of the Central Tien Shan geological structure, it is assumed that the lower-crustal low-velocity layer can play a significant role in the delamination of the mantle part of the submerged plates.

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.

The Effects of Current Leakage on Electroadhesion Forces in Rolling Friction and Magnetic Flux Density Distribution on the Surface of Rolling Element Bearings

1988 ◽  
Vol 110 (3) ◽  
pp. 448-455 ◽  
Author(s):  
Har Prashad
Keyword(s):  
Magnetic Flux ◽  
Flux Density ◽  
Rolling Friction ◽  
High Resistivity ◽  
Magnetic Flux Density ◽  
Rolling Element Bearings ◽  
Electrical Fields ◽  
Low Resistivity ◽  
Pure Rolling ◽  
Rolling Element

The present work deals with the investigations carried out on the various rolling element bearings after being operated under the influence of electric fields, and pure rolling friction on the roller bearing test machine. The significant magnetic flux density was detected on surfaces of the bearings lubricated with low-resistivity grease under the influence of electrical fields. No such phenomenon was observed either on bearings using high or low-resistivity greases under pure rolling friction or on bearings lubricated with high-resistivity grease under the influence of electrical fields. New bearing surfaces do not show significant magnetic flux density but it has been detected after long operation on different motor bearings, lubricated with low resistivity greases. The electroadhesion forces in the bearings using low-resistivity greases increase under the influence of electrical fields in contrast to those with high resistivity greases. Under pure rolling friction resistivity of greases do not affect the electroadhesion forces. The investigations reported in this paper along with the study of damaged/corrugated surfaces, and deterioration of the used greases [1, 2, 3], the leakage of current leading to failure of the noninsulated motor bearings can be established.

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