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3D model of Svecofennian Accretionary Orogen and Karelia Craton based on geology,reflection seismics,magnetotellurics and density modelling:Geodynamic speculations

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Geoscience Frontiers 2020年第3期11卷 999-1023页

作者： Michael V.Mints Victor N.Glaznev Olga M.Muravina Elena Yu Sokolova Geological Institute RASMoscowRussia Voronezh State University VoronezhRussia Schmidt Institute of Physics of the Earth RASMoscowRussia All-Russian Research Geological Oil Institute MoscowRussia

A 3D model of deep crustal structure of the Archaean Karelia Craton and late Palaeoproterozoic Svecofennian Accretionary Orogen including the boundary zone is *** model is based on the combination of data from geological mapping and reflection seismic studies,along profiles 1-EU,4 B,FIRE-1-2 a-2 and FIRE-3-3 a,and uses results of magnetotelluric soundings in southern Finland and northern Karelia.A seismogeological model of the crust and crust-mantle boundary is compared with a model of subhorizontal velocity-density layering of the *** TTG-type crust of the Palaeoarchaean and Mesoarchaean microcontinents within the Karelia Craton and the Belomorian Province are separated by gently dipping greenstone belts,at least some of which are *** structure of the crust was determined mainly by Palaeoproterozoic tectonism in the intracontinental settings modified by a strong collisional compression at the end of the *** insights into structure,origin and evolution of the Svecofennian Orogen are *** accretionary complex is characterized by inclined tectonic layering:the tectonic sheets,~15 km thick,are composed of volcanic-sedimentary rocks,including electro-conductive graphite-bearing sedimentary rocks,and electro-resistive granitoids,which plunge monotonously and consecutively *** reaching the level of the lower crust,the tectonic sheets of the accretionary complex lose their distinct *** the seismic reflection pattern they are replaced by a uniform acoustically translucent medium,where separate sheets can only be traced *** crust-mantle boundary bears a diffuse character:the transition from crust to mantle is recorded by the disappearance of the vaguely drawn boundaries of the tectonic sheets and in the gradual transition of acoustically homogeneous and translucent lower crust into transparent *** the effect of endogenic heat flow,the accretionary complex underwent high-temperatu

关键词： Reflection seismics magnetotellurics Svecofennian accretionary Orogen Svecofennian Ocean 3D crustal model Velocity-density layering

Imaging the Architecture of Mineral Systems and the Pathways of Ore-forming Fluids across Mongolia with magnetotellurics

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Acta Geologica Sinica(English Edition) 2024年第S01期98卷 11-13页

作者： Matthew J.COMEAU Rafael RIGAUD Erdenechimeg BATMAGNAI Shoovdor TSERENDUG Sodnomsambuu DEMBEREL Michael BECKEN Alexey KUVSHINOV Department of Geoscience&Engineering Delft University of Technology The Netherlands Institute of Geophysics ETHZürichSwitzerland Institute of Astronomy and Geophysics Mongolian Academy of SciencesUlaanbaatarMongolia Institut für Geophysik Universität MünsterGermany

In the framework of a mineral system approach,a combination of components is required to develop a mineral *** includes the whole-lithosphere architecture,which controls the transport of ore-forming fluids,and favorable tectonic and geodynamic processes,occurring at various spatial and temporal scales,that influence the genesis and evolution of ore-forming fluids(Huston et al.,2016;Groves et al.,2018;Davies et al.,2020).Knowledge of the deep structural framework can advance the understanding of the development of a mineral system and the emplacement of mineral *** geophysical exploration carried out with this aim is increasingly important for targeting new ore deposits in unexplored and underexplored regions(Dentith et al.,2018;Dentith,2019).

关键词： magnetotellurics electrical resistivity mineral exploration mineral emplacement ore fluids fluid transport

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

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Journal of Earth Science 2023年第6期34卷 1744-1757页

作者： Xiaobo Zhang Penghui Zhang Meixing He Dashuang He Fagen Pei Yaoyang Zhang Yan Peng Institute of Geophysical and Geochemical Exploration Chinese Academy of Geological SciencesLangfang 065000China National Research Center for Geo-exploration Technology Langfang 065000China College of Earth Sciences Chengdu University of TechnologyChengdu 610059China

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 *** has great shale gas resource *** formation mechanism of this basin is poorly studied for lack of constraining data for deep *** 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 *** 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 *** 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 *** 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 *** findings provide a geophysical basis for future studies of basin tectonic evolution and regional tectonic frameworks.

关键词： Wuwei Basin Lower Yangtze deep structure electrical structure fold-and-thrust belt shale gas magnetotellurics geophysics

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

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Acta Geologica Sinica(English Edition) 2022年第3期96卷 791-805页

作者： LUO Fan Lü Qingtian ZHANG Kun YAN Jiayong Colin GFARQUHARSON ZHANG Chong FU Guangming School of Geophysics and Measurement-control Technology' East China University of TechnologyNanchang 330013China Chinese Academy of Geological Sciences Beijing 100037China China Deep Exploration Center China Geological Survey&Chinese Academy of Geological SciencesBeijing 100037China Department of Earth Sciences Memorial University of NewfoundlandSt.John'sNL A1B 3X5Canada

The northern Wuyi area,which is located in the northern Wuyi metallogenic belt,has superior mineralization *** Pingxiang-Guangfeng-Jiangshan-Shaoxing fault(PSF)extends across the whole region regardless of whether or how the PSF relates to the near-surface *** carried out an MT survey in the region and obtained a reliable 2D model of the crustal electrical structure to a depth of 30 *** the resistivity model,we inferred that a continuous high conductivity belt that ranges from the shallow to deep crust is a part of the ***,we estimated the fluid content and pressure gradient to identify the deep sources of fluid as well as its pattern of motion ***,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 analysis showed that the Jiangnan orogenic belt and the Cathaysia block formed the PSF during the process of *** deep fluid migrated upward through the PSF to the shallow ***,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.

关键词： magnetotellurics crustal electrical structure PSF deep metallogenic background model northern Wuyi area

Implications for the lithospheric structure of Cambay rift zone,western India:Inferences from a magnetotelluric study

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Geoscience Frontiers 2020年第5期11卷 1743-1754页

作者： Nagarjuna Danda C.K.Rao Amit Kumar P.Rama Rao P.B.V.Subba Rao Dr.K.S.Krishnan Geomagnetic Research Laboratory IIGAllahabad221505India Indian Institute of Geomagnetism New PanvelNavi Mumbai410218India Department of Geophysics Andhra UniversityVisakhapatnam530003India

Broad-band and long-period magnetotelluric(MT)data were acquired along an east-west trending traverse of nearly 200 km across the Kachchh,Cambay rift basins,and Aravalli-Delhi fold belt(ADFB),western *** regional strike analysis of MT data indicated an approximate N59°E geoelectric strike direction under the traverse and it is in fair agreement with the predominant geological strike in the study *** decomposed transverse electric(TE)-and transverse magnetic(TM)-data modes were inverted using a nonlinear conjugate gradient algorithm to image the electrical lithospheric structure across the Cambay rift basin and its surrounding *** studies show a thick(~1-5 km)layer of conductive Tertiary-Mesozoic sediments beneath the Kachchh and Cambay rift *** resistive blocks indicate presence of basic/ultrabasic volcanic intrusives,depleted mantle lithosphere,and different Precambrian structural *** crustal conductor delineated within the ADFB indicates the presence of fluids within the fault zones,sulfide mineralization within polyphase metamorphic rocks,and/or Aravalli-Delhi sediments/*** observed conductive anomalies beneath the Cambay rift basin indicate the presence of basaltic underplating,volatile(CO2,H2 O)enriched melts and channelization of melt fractions/fluids into crustal depths that occurred due to plume-lithosphere *** variations in electrical resistivity observed across the profile indicate that the impact of Reunion plume on lithospheric structures of the Cambay rift basin is more dominant at western continental margin of India(WCMI)and thus support the hypothesis proposed by Campbell&Griffiths about the plume-lithosphere interactions.

关键词： Cambay rift Deccan basalts magnetotellurics Partial melt Reunion plume

Study on new optimum parameters in MT repeated survey

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Acta Seismologica Sinica(English Edition) 1994年第4期7卷 603-610页

作者：张云琳刘晓玲安海静司玉兰蒋梅张五四李志雄 1. Seismological Bureau of Hainan Province 570004 Haikou China 2. Earthquake Research Institute of Lanzhou State Seismological Bureau 730000 Lanzhou China

The first MT monitoring profile with initial shape both at home and abroad has been built in the northern margin of the Qinghai-Tibet Plateau. Based on MT data observed before and after the eight earthquakes of M=5-7 from 1988 to 1992,a new parameter-mean resistivity has been introduced. The results show that indicates not only the major feature of decreasing-increasing and recovering to notmal value, but also synchronism of phase or the variation in a large area, 'lead or delay' among different small areas and the amplitude decreasing with the increase of the distance from the epicenter. Two characters mentioned above might correspond to reginal field precursor of the tectonic generating earthquake and field precursor of the tectonic kinematics. This paper analyses the errors of observed data and the cause of variation. The MT profile optimum parameter system consists of parameter,apparent resistivity,twisting degree and the principal-axis azimuth which might provide quantitative criterion for the physical prooes of the great destructive earthquake and moderate and short-term earthquake prediction.

关键词： magnetotellurics mean resistivity prospecting depth MT optimum parameter MT monitoring optimum depth

2D magnetotelluric inversion based on ResNet

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Artificial Intelligence in Geosciences 2023年第1期4卷 119-127页

作者： LiAn Xie Bo Han Xiangyun Hu Ningbo Bai Institute of Geological Survey China University of GeosciencesWuhan430074China Hubei Subsurface Multi-Scale Imaging Key Laboratory School of Geophysics and GeomaticsChina University of GeosciencesWuhan430074China Key Laboratory of Geological Survey and Evaluation of Ministry of Education China University of GeosciencesWuhan430074China

In this study,a deep learning algorithm was applied to two-dimensional magnetotelluric(MT)data *** with the traditional linear iterative inversion methods,the MT inversion method based on convolutional neural networks(CNN)does not rely on the selection of the initial model parameters and does not fall into the local *** the CNN inversion models can provide a clear electrical interface division,their inversion results may remain prone to abrupt electrical interfaces as opposed to the actual underground electrical *** solve this issue,a neural network with a residual network architecture(ResNet-50)was constructed in this *** the apparent resistivity and phase pseudo-section data as the inputs and with the resistivity parameters of the geoelectric model as the training labels,the modified ResNet-50 model was trained end-to-end for producing samples according to the corresponding production strategy of the study *** experiments,the training of the ResNet-50 with the dice loss function effectively solved the issue of over-segmentation of the electrical interface by the cross-entropy function,avoided its abrupt inversion,and overcame the computational inefficiency of the traditional iterative *** proposed algorithm was validated against MT data measured from a geothermal field prospect in Huanggang,Hubei Province,which showed that the deep learning method has opened up broad prospects in the field of MT data inversion.

关键词： magnetotellurics 2D inversion Residual network Deep learning

Investigating the Whole-lithosphere Structure of a Mineral System——Pathways and Source of Ore-forming Fluids Imaged with Magnetotelluric Modeling

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Acta Geologica Sinica(English Edition) 2021年第S01期95卷 73-75页

作者： Matthew J.COMEAU Michael BECKEN Alexey V.KUVSHINOV Sodnomsambuu DEMBEREL Erdenechimeg BATMAGNAI Shoovdor TSERENDUG Institut für Geophysik Universitat MünsterGermany Institute of Geophysics ETHZürichSwitzerland Institute of Astronomy and Geophysics Mongolian Academy of SciencesUlaanbaatarMongolia

Whole-lithosphere structure has direct implications for both the genesis of minerals and the locations of mineral emplacement;thus knowledge of the deep structural framework of the lithosphere can advance understandin... 详细信息

关键词： magnetotellurics electrical resistivity lithosphere structure mineral exploration metal belt oreforming fluids mineral emplacement fluid transport

Analytic Solution to the MT Responses of a Two-Segment Model with Axially Anisotropic Conductivity Structures Overlying a Perfect Insulator

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吉林大学学报（地球科学版） 2016年第4期46卷 1260-1267页

作者： Qin Linjiang Yang Changfu Second Institute of Oceanography State Oceanic Administration Key Laboratory of Submarine Geosciences State Oceanic Administration School of Earth Sciences Zhejiang University

The analytic solution of the magnetotelluric fields for an idealized 2-D model which is composed of two segments with diagonal anisotropy underlain by aperfect insulator basement is considered using aquasi-static analytic *** analytic magnetotelluric responses for a particular model are *** resulting analytic solution could be used to check the numerical solutions given by numerical algorithms before more complex situations are investigated.

关键词： anisotropy magnetotellurics analytic solution two-dimensionalanisotropy magnetotellurics analytic solution two-dimensionalanisotropy magnetotellurics analytic solution two-dimensional