Electrical Structure and Fault Features of Crust and Upper Mantle beneath the Western Margin of the Qinghai-Tibet Plateau:Evidence from the Magnetotelluric Survey along Zhada-Quanshui Lake Profile

The magnetotelluric （MT） survey along the Zhada （札达）-Quanshui （泉水） Lake profile on the western margin of the Qinghai （青海）-Tibet plateau shows that the study area is divided into three tectonic provinces by the Yalung Tsangpo and Bangong （班公）-Nujiang （怒江） sutures. From south to north these are the Himalayan terrane, Gangdise terrane, and Qiangtang （羌塘） terrane. For the study area, there are widespread high-conductivity layers in the mid and lower crust, the top layers of which fluctuate intensively. The high-conductivity layer within the Gangdise terrane is deeper than those within the Qiangtang terrane and the Himalaya terrane, and the deepest high-conductivity layer is to the south of the Bangong-Nujiang suture. The top surface of the high-conductivity layer in the south of the Bangong-Nujiang suture is about 20 km lower than that in the north of it. The high-conductivity layer within the Gangdise terrane dips toward north and there are two high-conductivity layers within the crust of the southern Qiangtang terrane. In the upper crust along the profile, there are groups of lateral electrical gradient zones or distortion zones of different scales and occurrence indicating the distribution of faults and sutures along the profile. According to the electrical structure, the structural characteristics and space distribution of the Yalung Tsangpo suture, Bangong.Nujiang suture, and the major faults of Longmucuo （龙木错） and Geerzangbu are inferred.

Crustal Electrical Structure and Deep Metallogenic Potential in Northern Wuyi Area(South China),based on Magnetotelluric Data

The northern Wuyi area,which is located in the northern Wuyi metallogenic belt,has superior mineralization conditions.The Pingxiang-Guangfeng-Jiangshan-Shaoxing fault(PSF)extends across the whole region regardless of whether or how the PSF relates to the near-surface mineralization.We carried out an MT survey in the region and obtained a reliable 2D model of the crustal electrical structure to a depth of 30 km.In the resistivity model,we inferred that a continuous high conductivity belt that ranges from the shallow to deep crust is a part of the PSF.Then,we estimated the fluid content and pressure gradient to identify the deep sources of fluid as well as its pattern of motion pattern.Finally,we proposed a model for the deep metallogenic migration processes that combines geological data,fluid content data,pressure gradient data,and the subsurface resistivity model.The model analysis showed that the Jiangnan orogenic belt and the Cathaysia block formed the PSF during the process of com.The deep fluid migrated upward through the PSF to the shallow crust.Therefore,we believe that the PSF is an ore-forming fluid migration channel and that it laid the material basis for large-scale mineralization in the shallow crust.

Lithospheric Electrical Structure across the Eastern Segment of the Altyn Tagh Fault on the Northern Margin of the Tibetan Plateau

Project INDEPTH （InterNational DEep Profiling of Tibet and the Himalaya） is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a component of magnetoteUuric （MT） work in the 4th phase of the project, MT data were collected along a profile that crosses the eastern segment of the Altyn Tagh fault on the northern margin of the plateau. Time series data processing used robust algorithms to give high quality responses. Dimensionality analysis showed that 2D approach is only valid for the northern section of the profile. Consequently, 2D inversions were only conducted for the northern section, and 3D inversions were conducted on MT data from the whole profile. From the 2D inversion model, the eastern segment of the Altyn Tagh fault only appears as a crustal structure, which suggests accommodation of strike slip motion along the Altyn Tagh fault by thrusting within the Qilian block. A large-scale off-proffie conductor within the mid-lower crust of the Qilian block was revealed from the 3D inversion model, which is probably correlated with the North Qaidam thrust belt. Furthermore, the unconnected conductors from the 3D inversion model indicate that deformations in the study area are generally localized.

Determining water well sites based on electrical structure in Taobei District of Baicheng

Drilling a well randomly would lead to high uncertainties and could not meet the demand of water supply from the increasing population.It is in dire need to improve success rate of well drilling.The high-density resistivity method offers us a good choice.In this study,high-density resistivity method is used for groundwater survey in five villages in the Taobei District of Baicheng.The data obtained by high-density resistivity method is inverted through Res2dinv software.It is found that the electrical structure is characterized by a horizontal layer distribution,and the resistivity shows a"high-medium low-low"feature from shallow to deep.Moreover,obvious electrical gradient zones are identified in the strata below each section,which are interpreted as tectonic weak zones,i.e.,the faults.The low-resistance anomaly areas are inferred to be favorable aquifers.The results show that high-density resistivity exploration is an efficient and practical method for determining water well sites in rural areas and can provide a guide for finding water resources in the area.

Electrical Structure of Yarlung Zangbo Suture from Magnetotelluric Profiling of INDEPTH-MT

The INDEPTH MT results show that there are no electrical features of deep fractures along the Yarlung Zangbo River, but a large high conductivity body exists in the area between Gyangze and Rinbung. It dips northward, extends downward up to the depth of about 55 km and indicates the exposure of the possible real position of the Yarlung Zangbo suture. There are three sets of electrical gradient and distorted zones reflecting the structure of faults in the high conductivity region. These three fault belts, which dip northward and gradually converge downward to the main fault belt, and a series of south dipping faults in the north side form the exhaled structural characteristics of the Yarlung Zangbo suture. There is a close relationship between the large high conductivity body and the underground thermal state.

An Investigation of Deep Electrical Structure of Qiangtang Basin,Xizang(Tibet),China

In order to study the deep geoelectrical structure and the regional geological structure and detect potential oil and gas areas in Qiangtang basin in northern Xizang (Tibet ), 222 MT soundings were conducted along three N - S MT profiles across the basin .The MT results indicate that the south and north parts of the Qiangtang basin have a good contrast in the deep electri cal structure . In the south Qiangtang , there are generally two high conductivity layers in the crust . The first is at a depth of about 10 - 25 km and possesses a resistivity of about 10 - 80 Ωm .The second ,the high conductivity layer in the lower crust ,is at a depth of about 40 - 70 km with 3 - 50 Ωm .In the north Qiangtang .there is generally one high conductivity layer .It is at a depth of about 10 - 30 km and the resistivity is about 1-60 Ωm . The thickness of the second high conductivity layer in both the south Qiangtang and the Bangong-Nujiang suture is much greater than that of the first .The thickness of the lithosphere is about 110-120 km for the Bangong-Nujiang suture ,115 km for the south Qiangtang and 100-130 km for the north Qiangtang . On the difference of the deep electrical structures of the crust between the south and the north Qiangtang , we believe that it is related to the eastward flow of the crustal substance .

Three-dimensional electrical structure model of the Yangbajain geothermal field in Tibet:Evidence obtained from magnetotelluric data

The Yangbajain Geothermal Field in Tibet is located in the fault subsidence basin of the central Yadong-Gulu Rift Valley.The spatial distribution of the field is controlled by mountain-front fault zones on the northwestern and southeastern sides of the basin.Geothermal power has been generated in Yangbajain for more than 40 years.However,owing to the lack of threedimensional(3D) geophysical exploration data,key geological issues related to the partial melt body of the Yangbajain Geothermal Field,such as its location,burial depth,and geometric form,as well as the ascending channel of the geothermal fluid,have for a long time been controversial.In this study,3D inversion was performed using measured geo-electromagnetic total impedance tensor data from 47 survey points.The extracted horizontal sections at different depths and profiles,and at different lines,reflect the 3D electrical structure model of the geothermal field in the study area.Subsequently,three findings were obtained.First,the partial melt body,located below the China-Nepal Highway extending along the northeast direction,is the heat source of the Yangbajain Geothermal Field.The burial depth range of the molten body was determined to range between approximately 6.2 and 14 km.Moreover,the geothermal fluid ascended a horn-shaped circulation channel with an up-facing opening,located in the northern section of the sulfur ditch area.The study results revealed that deep rock fissures(>2 km) were not well developed and had poor permeability.In addition,no layered heat reservoirs with high water richness were observed in the northern part of the study area.However,the application of enhanced geothermal system(EGS) technology in the northern region would be essential to improving the power generation capacity of the Yangbajain Geothermal Field.In addition,the study found no deep high-temperature heat storage areas in the southern region of the study area.

Crustal Electrical Structure of the Wuwei Basin,Lower Yangtze Region of China,and Its Geological Implications

The Wuwei Basin is one of the most important oil-and gas-bearing basins in the Meso-Cenozoic basin groups in the Lower Yangtze River region.It has great shale gas resource prospects.The formation mechanism of this basin is poorly studied for lack of constraining data for deep structures.In this paper,a crustal electrical structure model of the Wuwei Basin and the adjacent areas is constructed based on the two-dimensional inversion of a magnetotelluric(MT)sounding profile achieved with the nonlinear conjugate gradient method.The results show that large-scale low-resistance bodies have developed in the underlying middle and lower crust of the Wuwei Basin,and are different from the uplifts on the two sides according to their high-resistance electrical characteristics.The electrical structure and regional geological and geophysical data suggest that the peak zone of the Chuzhou-Chaohu foreland fold-and-thrust belt is located on the east bank of the Yangtze River(Wuhu Section),which,together with the main thrust fault belt in the east,forms a typical thrust structure belt.An early Yanshanian sinistral strike-slip fault developed in the deep part of the Wuwei Basin,which may have controlled the formation and evolution of the basin,whereas the tectonic inversion of the early-developed thrust faults is relatively weak.These findings provide a geophysical basis for future studies of basin tectonic evolution and regional tectonic frameworks.

Characteristics of the three-dimensional deep electrical structure in the Helan Mountains-Yinchuan Basin and its geodynamic implications

Located in the north segment of the North-South seismic belt where the Alxa block(AB)and the Ordos block(OB)contact,the Helan Mountains-Yinchuan Basin(HLM-YCB)constitutes a typical normal faulting basin-mountain structure on the Chinese mainland.The 1739 M8.0 Pingluo earthquake occurred in the Yinchuan fault depression basin with such a basinmountain structure.Data on five magnetotelluric profiles encompassing distinct segments of the HLM-YCB were utilized for three-dimensional(3D)joint inversion in order to collect fine 3D electrical structure information at a crustal and upper mantle scale across the entire region.The electrical structure between the main blocks in the HLM-YCB and adjacent areas is characterized by east-west horizontal blocks OB,YCB,and HLM,which are divided by the Yellow River fault(F5)with the HLM eastern piedmont fault(F2)as electrical boundary zones on the east and west sides.The two main block units,AB and OB,exhibit an obvious layered resistivity structure.Besides,the HLM-YCB is characterized by a typical basin-mountain structure with the mountains as a high-resistivity body and the basin as a low-resistivity body,and in the northern YCB a large-scale lowresistivity structure exists,extending to the upper mantle,probably derived from the upwelling of mantle-derived materials.It is speculated from a combination of recent 3D crustal movement field information and other data that the HLM-YCB is an active tectonic zone formed via regional tensile action.The formation of the HLM-YCB lies in the interaction of the Tibetan Plateau(TP),AB,and OB and abnormal mantle activities beneath the YCB.The HLM-YCB reflects the joint action of upwelling and diffluence caused by the underplating of hot materials from the deep mantle with gravity and the redistribution of regional tectonic stress on the earth’s surface,which may be the main dynamic reason for the 1739 M8.0 Pingluo earthquake.

A review on developments in the electrical structure of craton lithosphere

Cratons have a long history of evolution.In this paper,applications of the magnetotelluric method used in the study of craton lithosphere over the past 30 years were reviewed,examining case studies of cratons in North America,South America,Asia,Australia,and Africa.The nuclei of the Archean cratons,for example the Kalahari Craton and Rae Craton,are usually characterized by thick and highly resistive lithospheric roots.During or after the formation of the cratons,tectonothermal events,such as collision,mantle plume,and asthenosphere upwelling led to the formation of high-conductivity zones in the craton lithosphere,which could be attributed to the increased hydrogen content(of nominally anhydrous minerals),higher iron content,and formation of graphite films or sulfides along the grain boundary of minerals.These conductive zones are characterized by resistivity discontinuities in craton lithosphere.In particular,the conductive zones include(1)large-scale lithospheric mantle conductors beneath the Slave Craton,Gawler Craton,and central part of North China Craton(Trans-North China Orogen);(2)near-vertical high-conductivity zone associated with the fossil subduction zone beneath the Dharwar Craton and Slave Craton;and(3)regional lateral electrical discontinuities,such as a conductive anomaly under the Bushveld Complex of the Kaapvaal Craton.The eMoho refers to the electrical discontinuity in the crust-mantle boundary.In existing research,this has been detected under the condition of extremely high lithospheric resistivity with only a slight decrease in the lower crust,and in the case of a very thin conductive lower crust or the lack thereof.In the resistivity model,the unique"mushroom-like"lower crust-lithosphere mantle conductor and very thin lower crust layer of the North China Craton may represent lithosphere destruction and/or thinning.We also find that some of the cratons are still not well understood.Therefore,extensive three-dimensional inversion and joint interpretation of geochemical,geophysical,and geologic data are necessary to understand the tectonic evolutionary history of craton lithosphere.

Resistivity Logs of the Chinese Continental Scientific Drilling Main Hole:Implication for the Crustal Electrical Structure of Dabie-Sulu Terrane,Central-Eastern China

To understand the electrical structure of the Sulu（苏鲁） terrane,we analyzed the resis-tivity logs of the Chinese Continental Scientific Drilling main hole（CCSD-MH） and obtained the statis-tical characteristics of the resistivity log of ultrahigh-pressure（UHP） metamorphic rocks.To check the logs＇ quality,we compared the resistivity log data with the core test data.The two datasets show a good coherence.On the whole,the resistivity of the UHP metamorphic rocks from the CCSD-MH is very high（mostly higher than 1 000 ？？m）.From orthogneiss to paragneiss,amphibolite,retrograded eclogite,rutile eclogite,phengite eclogite,and ultramafic rock,the resistivity decreases gradually.The fracture zone,enrichment of metal minerals,and serpentinization of peridotite can probably cause the decrease of resistivity.Comparing the electrical structure of the crust of Dabie（大别） terrane and Sulu terrane,we can conclude that（1） the electrical structure of the crust of Dabie terrane and Sulu terrane shows a very big difference,（2） the high-resistivity zone of the north Sulu orogen extended to a very great depth（60 km）,but the high-resistivity zone of Dabie orogen is over the depth of 25 km.

Crust and Upper Mantle Electrical Resistivity Structure in the Panxi Region of the Eastern Tibetan Plateau and Its Significance

The Panxi region is located in the frontal zone of positive squeezing subduction and side squeezing shearing between the Indian plate and the Eurasian plate. The long-period magnetotelluric （LMT） and broadband magnetotelluric （MT） techniques are both used to study the deep electrical conductivity structure in this region; magnetic and gravity surveys are also performed along the profile. According to the 2-D resistivity model along the Yanyuan-Yongshan profile, a high- conductivity layer （HCL） exists widely in the crust, and a high-resistivity block （HRB） exists widely in the upper mantle in general, as seen by the fact that a large HCL exists from the western Jinpingshan tectonic zone to the eastern Mabian tectonic zone in the crust, while the HRB found in the Panxi tectonic zone is of abnormally high resistivity in that background compared to both sides of Panxi tectonic zone. In addition, the gravity and magnetic field anomalies are of high value. Combined with geological data, the results indicate that there probably exists basic or ultrabasic rock with a large thickness in the lithosphere in the Panxi axial region, which indicates that fracture activity once occurred in the lithosphere. As a result, we can infer that the high-resistivity zone in the Panxi lithosphere is the eruption channel for Permian Emeishan basalt and the accumulation channel for basic and ultrabasic rock. The seismic sources along the profile are counted according to seismic record data. The results indicate that the most violent earthquake sources are located at the binding site of the HRB and the HCL, where the tectonic activity zone is generally acknowledged to be; however, the earthquakes occurring in the HCL are not so violent, which reflects the fact that the HCL is a plastic layer, and the fracture threshold of a plastic layer is low generally, making high stress difficult to accumulate but easy to release in the layer. As a result, a higher number of smaller earthquakes occurred in the HCL at Daliangshan tectonic zone, and violent earthquakes occurred at the binding site of high- and low-resistivity blocks at the Panxi tectonic zone.

The Electrical Conductivity Structure of the Lanping–Simao Basin and its Implications for Mineralization

Objective The Lanping-Simao Basin in western Yunnan, located in the southeastern margin of the Tibetan Plateau, is tectonically in the transition zone between the Gondwana and Eurasia tectonic domains. It is also the frontier zone of northeastern extrusion of the Indochina Plate towards the Eurasia Plate as well as the escape zone for the deep material. The middle axial tectonic zone, also known as the Lanping-Simao Fault （LSF） in previous study, is a giant intraplate tectonic belt composed of a series of narrow uplift belt, rupture depression zone, metamorphic belt, alteration belt and marginal fracture system, which were formed by the compressional uplift of the central depression of the Lanping-Simao Basin. This tectonic unit controls the geological evolution, seismic activity, hot spring distribution and ore formation of the LanpingSimao Basin since the Mesozoic and Cenozoic.

Effects of Si δ-Doping Condition and Growth Interruption on Electrical Properties of InP-Based High Electron Mobility Transistor Structures

The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration （Nd） is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.

Deep electrical conductivity structure in the Great Wall Station area， Fildes Peninsula， West Antarctica

MT measured in Great Wall Station area shows that the electrical conductivity major axis of the Wind Valley Fault is 110°NE and the crustal thickness in the Fildes Peninsula is about 22. 3 km. The crust contains four main resistivity layers with their thicknesses being 1. 3 km, 6. 7 km, 1. 2 km and 13.1 km respectively. The upper crustal thickness is 9. 2 km and the lower crustal thickness is 13. 1 km.

Structural,Morphological and Electrical Properties of In-Doped Zinc Oxide Nanostructure Thin Films Grown on p-Type Gallium Nitride by Simultaneous Radio-Frequency Direct-Current Magnetron Co-Sputtering

Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.

Illumination and Voltage Dependence of Electrical Characteristics of Au/0.03 Graphene-Doped PVA/n-Si Structures via Capacitance/Conductance-Voltage Measurements

Au/n-Si （MS） structures with a high dielectric interlayer （0.03 graphene-doped PVA） are fabricated to investigate the illumination and voltage effects on electrical and dielectric properties by using capacitance-voltage （C-V） and conductance-voltage （G/w-V） measurements at room temperature and at 1 MHz. Some of the main electrical parameters such as concentration of doping atoms （ND）, barrier height （ ФB（ C - V） ）, depletion layer width （WD） and series resistance （Rs） show fairly large illumination dispersion. The voltage-dependent profile of surface states （Nss） and resistance of the structure （Ri ） are also obtained by using the dark-illumination capacitance （Cdark- Cm） and Nicollian-Brews methods, respectively, For a clear observation of changes in electrical parameters with illumination, the values of ND, WD, ФB（O- V） and Rs are drawn as a function of illumination intensity. The values of ND and WD change almost linearly with illumination intensity. On the other hand, Rs decreases almost exponentially with increasing illumination intensity whereas ФB（C - V） increases. The experimental results suggest that the use of a high dielectric interlayer （0.03 graphene-doped PVA） considerably passivates or reduces the magnitude of the surface states. The large change or dispersion in main electrical parameters can be attributed to generation of electron-hole pairs in the junction under illumination and to a good light absorption. All of these experimental results confirm that the fabricated Au/0.03 graphene-doped PVA/n-Si structure can be used as a photodiode or a capacitor in optoelectronic applications.

Structural Transformations and Multiferroic Properties of Bi_(1-x)Eu_(x)Fe_(0.95)Co_(0.05)O_(3)(x=0.05,0.10,0.15,and 0.20)

Bi_(1-x)Eu_(x)Fe_(0.95)Co_(0.05)O_(3 )(x=0.05,0.10,0.15,and 0.20) nanoparticles were prepared through the sol-gel technique.Its structure,local electronic structure,magnetic and electric properties were systematically investigated.X-ray diffraction data show(104),(110) bimodal alignment and high angular migration,indicating that with the increase of Eu substitution at Bi site,the structure of BFO undergoes a continuous change in crystal structure.The hysteresis loop and the FC/ZFC curve show how magnetism varies with the size of the field and temperature.Finally,the causes of magnetic changes were analyzed by studying SXAS and hysteresis loops.

A layered multifunctional framework based on polyacrylonitrile and MOF derivatives for stable lithium metal anode

Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.