Showing papers in "Chinese Journal of Geophysics in 2017"

Application of an enhanced theta-based filter for potential field edge detection: a case study of the luzong ore district

Abstract: Edge detection plays an important role in interpreting potential field data, and is widely used to delineate geologic boundaries and structures. Geologic boundaries can be determined by tracing the enhanced analytical signal, and many filters are developed to detect and enhance the edges. Horizontal and vertical derivatives are commonly used to enhance edge features, but they can only outline the edges of large-amplitude anomalies. In order to display large and small amplitude anomalies simultaneously, some balanced filters have been proposed. We define new filters based on the Theta map method, using 2nd order horizontal and vertical directional derivatives, and display large and small amplitude edges simultaneously. These methods were tested on synthetic gravity data, and compared with other traditional filters; the results show that the new filters can achieve better results and reveal more details. The method has been applied to gravity-magnetic data acquired in the Luzong ore district in the Middle-Lower Yangtze River Valley Metallogenic Belt (MLYB, Eastern China). Based on the relations between lithology, density and magnetic susceptibility, the calculated results were analyzed. The edge detection results accurately depict the location of the Tanlu fault zone. A gravity boundary north of the Yangtze River is interpreted to be part of the Yangtze River fault. The identified boundaries from the magnetic data are consistent with the margins of the Luzong basin, and indicate that the bounding faults dip towards the basin. Some ring-like closed boundaries occur in the periphery of the Luzong basin. Recent exploration results confirm that there are buried intrusions beneath the gravity-magnetic anomaly bodies, where Fe-Cu skarn mineralization is present. The results of this study provide significant insights for regional deep-level Fe-Cu exploration.

A study on the rock physics model of gas reservoir in tight sandstone

Abstract: According to the ultrasonic data of 51 measured core samples from 17 wells in the Sulige gas field, 304 groups of elastic parameters data including VP/VS and Poisson's ratio are obtained corresponding to different porosities and water saturations. The optimized rock physics corrections among the bulk modulus, Poisson's ratio, and gas saturation indicate that the Brie model (e=2) can fairly characterize the properties of upper Paleozoic Permian H8 reservoir in the Sulige gas field. Therefore, the proposed rock physics is able to estimate the physical parameters variation of tight sandstone reservoirs with gas-bearing saturation level. The proposed rock physics model is applied to predict gas-water reservoir by utilizing multi-wave seismic data of the Sulige gas field. The field test indicates that this model is capable of characterizing attributes of the target zone and predicting the gas-bearing reservoir.

Regional characteristics of stress state of main seismic active faults in mid‐northern part of sichuan‐yunnan block

Abstract: We restore the seismic source spectrums of 1012 earthquakes (2.0 ≤ ML ≤ 5.0) in the mid-northern part of Sichuan-Yunnan seismic block between January 1, 2009 and December 31, 2015, then calculate the source parameters (e.g., seismic moments M0, focal scale r and stress drop Δσ) and fit the calibration relationship between these parameters. Based on the regional seismic tectonic background, the distribution of active faults and seismicity, the study area is divided into four statistical units. For each unit the stress distribution characteristics, change of stress drop with location, correlation between the stress-strain loading and the dynamic process of regional deformation, are discussed respectively. The results show that seismic moments M0 are consistent with the magnitude-moment relation that lgM0 = 0.92ML + 10.46. The relationship between stress drop and magnitude is consistent with the result gained by Nuttli that intraplate earthquake follows the ISD model, with a statistical relationship lgΔσ = 0.31 lgM0 – 3.92. Seismic source stress drop results show the following, (1) The stress at the end of the Jinshajiang fault is low, the overall sliding rate of the fault unit is high, and strong earthquake activity is very rare. In the fault belt consisting of three secondary faults, stress-strain loading deceases gradually from northwest to southeast along Litang fault, the northwest section which is relatively locked is more likely to accumulate strain than southeast section. (2) Stress drop of Xianshuihe fault zone is divided by Kangding, the southern section is low and northern section is high. Southern section (Kangding-Shimian) is difficult to accumulate higher strain in the short term, but in northern section (Garze-Kangding), moderate and strong earthquakes have not filled the gaps of seismic moment release, there is still a high stress accumulation in partial section. (3) High stress-drop events were concentrated on Anninghe-Zemuhe fault zone, strain accumulation of this unit is strong, and stress level is the highest, earthquake risk is high. (4) On Lijiang-Xiaojinhe fault zone, stress drop characteristics of different magnitude earthquakes are not the same, which is related to complex tectonic setting, the specific reasons still need to be discussed deeply. Stress background in the Muli area is low and may be affected by the local tectonic environment. The study also shows that, (1) Stress drops display a systematic change with different faults and locations, high stress-drop events occur mostly in the fault intersection area. Faults without locking condition and mainly creeping are mainly characterized by low stress drop. (2) Contrasting to what is commonly thought that “strike-slip faults are not easy to accumulate stress”, Xianshuihe fault zone and Anninghe-Zemuhe fault zone all exhibit high stress levels, which may be due to that the magnitude and intensity of medium-strong earthquakes are not enough to release the accumulated energy. On the other hand, in the complex dynamics of regional deformation, when the tectonic force blocking fault movement and its contribution to accumulation of stress plays a key role, the earthquake of same magnitude will release higher stress drop.

Dem development and precision analysis for antarctic ice sheet using cryosat-2 altimetry data

Abstract: Digital elevation models (DEMs) are of fundamental importance to many geoscientific and environmental studies in Antarctic and due to relatively poor coverage by ground based surveys, the main data source for constructing an Antarctic DEM is satellite altimetry. The newest operating satellite-borne altimeter with ice applications is the ESA satellite CryoSat-2, which was launched in April 2010. CryoSat-2 provides altimetry data up to a latitude of 88°S/N, which is a significant improvement to previous satellite-borne altimeters. Based on two full cycles of CryoSat-2 observations acquired between December 2012 and January 2015, we derived a new DEM for the Antarctic Ice Sheet. The accuracy of generated DEM depends largely on the interpolation method adopted and five widely used interpolation methods were compared using the Cross Validation method. The Kriging method yielded better estimates for the Antarctic Ice Sheet and was adopted when constructing the final DEM. For the CryoSat-2 LRM data we followed an iterative approach to correct for the surface slope, and the slope correction was applied to each data point using the relocation method. Data gap beyond the latitudinal limit of the CryoSat-2 mission (88°S) was filled by contour data from Antarctic Digital Database (ADD). Finally, we present a new Antarctic DEM with a pixel size of 1 km×1 km. The accuracy of the final DEM was assessed by ICESat, IceBridge and GPS data and compared with four widely used Antarctic DEMs namely Bamber 1 km DEM, ICESat DEM, RAMPv2 DEM and JLB97 DEM. The results show that the CryoSat-2 DEM has an uncertainty of 0.73±8.398 m. The vertical accuracy of the DEM is better than 1 m at domes, better than 4 m for the ice shelves, better than 10 m for the interior ice sheet and over 150 m for the rugged mountainous and coastal areas.

A second‐order synchrosqueezing s‐transform and its application in seismic spectral decomposition

Abstract: The Synchrosqueezing S-transform (SSST) is a novel approach for time-frequency (T-F) representation of non-stationary signals. By “squeezing” T-F spectrum of the S-transform (ST) of a signal, the SSST can obtain a high-resolution T-F spectrum. However, when the phase of a signal varies non-linearly with time, the instantaneous frequency (IF) of the signal calculated by the SSST would be inaccurate, causing reduction of the resolution of the T-F spectrum. In order to improve its performance in imaging such signals, we modify the formula of IF with the help of the second-order partial derivatives of time and frequency, and propose a second-order Synchrosqueezing S-transform (SSST2nd). Synthetic examples show that the SSST2nd not only has obviously higher resolution than commonly used T-F transforms, but also images the signals of which the IFs vary quadratically or sinusoidally with time better than the SSST. We apply the SSST2nd to perform spectral decomposition of seismic data for natural gas exploration. The results illustrate that the SSST2nd can be used to well detect frequency spectral anomalies correlated with natural gas accumulations. Therefore, it can be concluded that the SSST2nd is a good potential technique for seismic interpretation.

An experimental study on resistivity and conductive mechanism in low-permeability reservoirs with complex wettability

Abstract: As the clay film developed in low-permeability lithologic reservoirs absorbs oil, reservoirs become oil-wet, which results in abnormally high resistivity oil-water layers and water layers. Such layers bring great challenges to the identification of oil and water layers. In order to make clear the resistivity response characteristics and conductive mechanism in reservoirs with different wettability, cores were selected in Chang 8 formation, Yanchang group, Upper Triassic, the western Ordos basin of China. Experiments were conducted with these samples to simulate the process of oil displacing water, ageing and water displacing oil. In addition, the contact angles of thin slices after washing oil were also tested. The experimental results show that abnormally high resistivity cores are not completely water-wet after washing oil. However, the formation factors of abnormally high resistivity cores and normal resistivity cores have little difference. In the process of oil displacing water, the relationship between normal resistivity core resistivity index and water saturation is linear in a log-log plot, while that of abnormally high resistivity cores is convex. The resistivity of abnormally high resistivity cores remains unchanged during ageing process. Combining the analysis of nuclear magnetic resonance (NMR) T2 spectra under different conditions, it can be inferred that wettability of abnormally high resistivity cores has become less water-wet after oil displacing water, whereas the ageing process has little effect on the wettability. In the process of water displacing oil, the relation between abnormally high resistivity core resistivity index and water saturation is almost linear, which shows that the conductive structure of rock is not changed. Based on the analyses and discussions of these experimental results, a hydrocarbon accumulation mode and the corresponding conductive mechanism are proposed for low-permeability reservoirs with complex wettability. It shows that abnormally high resistivity water layers are caused by the destruction of continuous conductive paths under oil-wet condition. The researches and experiments are of great importance for understanding the conductive mechanism, identifying oil and water layers and evaluating water flooded formations in low-permeability reservoirs with complex wettability.

A preliminary study of submarine cold seeps by seismic oceanography techniques

Abstract: Submarine cold seeps are widely distributed in the continental margin seas around the world. In this study, we apply a conventional multichannel seismic reflection (seismic oceanography) method to image the water column near the seafloor in order to detect cold seeps. In addition to analyzing the fluid escape structures, we also describe and discuss the development positions, seismic reflection characteristics as well as features of the cold seeps. The seismic reflection from the water column is very weak; therefore, the seismic sections above and below the seafloor are processed in two different sequences as follows:(1) geometry definition, direct wave attenuation and amplitude recovery, high-pass filter, common midpoint sorting, constant velocity (seawater sound velocity) stack, and post-stack FK filter in some sections; and (2) data quality control, amplitude recovery, 6~100 Hz bandpass filter, multiple attenuation, deconvolution, velocity analysis, normal move-out correction, common midpoint stack, post-stack noise attenuation, 4~70 Hz bandpass filter, and FX migration. The processed sections are then assembled together along the seafloor after carefully adjusting the color scale. The analysis shows that active cold seeps primarily present plume, broom, and/or irregular shapes that have weak and chaotic seismic reflections in the water column. The seismic reflection amplitude is enhanced at times; this could be attributed to the suspension of mud or particles in the water column. Cold seepage activities are typically associated with fluid escape structures, including mud diapirs, pipes, faults, fractures, gas chimneys, seabed pockmarks, and mud volcanoes. This indicates fluid migration from deep to shallow strata, fluid seepage or escape at the seafloor, as well as the formation of widespread cold seep activities. All the results herein are derived from a comprehensive interpretation of the seismic sections of the water columns and strata; however, further field studies, theoretical simulations, and experiments are required to confirm these conclusions.

Correlation between emission intensities in dayside auroral arcs and precipitating electron spectra

Abstract: More than 20000 dayside auroral arcs of the 557.7 and 630.0 nm emission intensities have been statistically studied, and the dependences of the I557.7/I630.0 ratio on the I557.7 emission intensity have been determined. The 557.7 nm emission intensity has two maximum values in the hot spot and warm spot regions, with average values of 2.2 and 2.9 kR, respectively. But there is a maximum near magnetic noon for 630.0 nm emission intensity, with an average value of 1.5 kR. In the I557.7 emission range 0.1~10 kR, the I557.7/I630.0 ratio tends to increase from 0.2 to 9. The correlation between emission intensity and precipitating electron spectra has been investigated using 17 cases of DMSP passing through 40 auroral arcs above Chinese Arctic Yellow River Station (YRS). We obtain the equations that the average energy of the electrons is proportional to the I557.7/I630.0 ratio. There is a positive correlation between the total energy flux of the electrons and the I557.7 emission intensity. The typical region of electron precipitation, where the auroral arcs were observed, was the boundary plasma sheet (BPS) in the prenoon and postnoon sectors. We also found some low-energy precipitating electrons from the region of mantle, where the arcs are located poleward of dayside auroral oval. The magnetic source region of the precipitating electrons with low energy was identified as the low latitude boundary layer (LLBL) adjacent to magnetic noon. Arcs are located in the lower latitude in this region.

Shale reservoir conductive mechanism simulation based on percolation network

Abstract: The shale gas reservoir storage space mainly includes micro pores and cracks of micron and nano scale. Owing to the complex pore network, as well as high content of kerogen and clay minerals in shale matrix and existence of conductive minerals, especially pyrite, the shale reservoir conductive mechanism is quite different from that of conventional reservoir, and the I-Sw curve obtained by core electricity experiment is non-linear which makes traditional evaluation models such as Archie's law not suitable. Aiming at these issues, according to actual core experiment and CT scan data, a three dimensional percolation network is established with randomized algorithm and the node voltage and current are calculated through over-relaxation iteration algorithm. With this network, the reasons for non-Archie property and the influence factors of shale reservoir are analyzed. Simulation results show that pore structure, shape and size, mineral composition and formation water resistivity have different effects on the reservoir resistivity. By changing the setting value, single-correlation between the reservoir resistivity and these factors can be built, and percolation correction model is also developed to calculate shale reservoir water saturation. The method has achieved a good effect in a certain shale gas field in Sichuan, China, which presents a good application prospect and provides a new thought on solving complex problems in shale gas field exploration and development with network simulation methods.

Comparison and analysis of several planetary boundary layer schemes in wrf model between clear and overcast days

Abstract: In the present study, several most commonly used planetary boundary layer (PBL) parameterization schemes in the WRF model are utilized together with the observational data at Shouxian (from August to December, 2008). The present work is a part of Atmospheric Radiation Measurement (ARM) facility supported by the U.S. Department of Energy installed at Shouxian in China. In this study, we compared the simulation effect of meteorological elements and the structure of PBL over typical farmlands underlying surface from different parameterization schemes between clear and overcast days. The observational results revealed that for the simulation of cloud status, non-local schemes such as ACM2 and YSU are superior to the local schemes. Further, the ACM2 scheme is better in simulating temperature and vapor at a height of 2 m from the surface, and the MYJ scheme has an advantage over other schemes when simulating the wind direction or its speed. Also, for the simulation of potential temperature and vapor profile, non-local schemes (ACM2 and YSU) are superior to the local schemes both during clear and overcast days. It is depicted that the ACM2 scheme has better advantages when simulating under weak stable conditions and humidity inversion structure during night time. Moreover, for the simulation of wind speed profile, the MYJ and MYNN2.5 schemes are the best respectively during the clear and overcast days, under unstable day time condition. However, when considering weak stable condition, ACM2 scheme has a minimum deviation on clear days and YSU scheme is the best choice on overcast days. From the overall results, ACM2 scheme is superior both on clear and overcast days, when simulation is based on typical farmland underlying surface.

Interpretation of csamt single-component data

Abstract: Following the magnetotelluric method, the apparent resistivity of the controlled source audio-frequency magnetotelluric method is usually derived from the ratio of electric field and magnetic field. For CSAMT, as the source power current density is known, both of the electric and magnetic field components are related to the resistivity of the earth. The apparent resistivity can be obtained from the single electric field or magnetic field. In this paper, we put forward the inversion and interpretation methods for component data of CSAMT after analyzing the data features. During the curve fitting inversion, in order to deduct real formation and obtain finer resistivity-depth section, the number of frequency of curves is regarded as the inversion earth layers number. The all-zone electric component apparent resistivity inversion is developed. Then, the phase is introduced into the inversion process to cancel the static offset. The prospecting for water-filled goaf in Shanxi Province suggests that the single component interpretation is useful.

Numerical simulation and characteristics analysis of dual laterolog in cavernous reservoirs on the basis of 3d‐fem

Abstract: Cavernous carbonate formations are characterized by strong heterogeneity, which results in the complex electric logging responses and the difficulty in the logging identification and evaluation. Numerical simulation of electric logging tools is helpful to figure out the logging response characteristics in these formations and could provide theoretical support for cave recognition and evaluation. In this paper, based on three dimensional finite element methods, a local refinement technique is adopted for the accurate discretization and simulation of complex sphere caves. Then, the response characteristics and sensitivity of dual laterolog to caves around and penetrated by wellbore are analyzed, finally the differences of sensitive scope between deep and shallow laterolog are studied. The results show that the dual laterolog response decreases significantly when cave exists. Affected by cave boundary and the investigation depth of dual laterolog tool, the logging response for caves penetrated by wellbore is very complicated, however it exhibits parabolic-like characteristic for caves around wellbore. Compared with caves around wellbore, the dual laterolog is much more sensitive to caves penetrated by wellbore. For caves around wellbore, the maximum sensitive distance for deep and shallow laterolog between the cave boundary and well wall is 0.5 m and 0.3 m, respectively.

Role of snow depth in the influence of el niño on summer climate anomalies over east asia

Abstract: With the datasets of Global Land Data Assimilation System (GLDAS) NOAH land surface model, GPCC monthly mean rainfall, and NCAR/NCEP global monthly mean reanalysis from 1948 to 2010, by using methods of filtering, composite and linear regression and correlation, the characteristics of Eurasian snow depth anomalies in El Nino mature winter, its influences on soil moisture after snow melting, and finally on East Asian summer monsoon are investigated, and the main conclusions are as follows: In El Nino mature winter, snow depth in regions of the Iranian Plateau, the northeast of Lake Balkhash and the southern Tibetan Plateau increases remarkably, so are the related snow melting and soil moisture. The above-mentioned three regions are identified as the key regions for snow depth to store and extend the El Nino signals. In spring, the snow begins to melt, and the soil moisture increases correspondingly, thus the El Nino signals are transmitted from winter snow depth to soil moisture in spring. As a result, sensible heat flux decreases and latent heat flux increases, and the atmospheric circulations are greatly influenced. The anomalous soil moisture in the Iranian plateau is most important for the East Asian summer monsoon in El Nino decaying summer, since it has similar impact pattern on the anomalous summer precipitation as the El Nino composite. The spring and summer soil moisture in both the southern Tibetan plateau and the northeast of Lake Balkhash increase simultaneously, which significantly contribute to the increased precipitation in North China. Therefore, to investigate and predict the East Asian summer monsoon variability by using El Nino signal, the roles of snow depth in storing and modulating El Nino impacts in those key regions should be considered.

A global weak form element free method for direct current resistivity forward simulation

Abstract: We present a global weak form element free method (EFM) for simulation of direct current resistivity. EFM is a new numerical simulation method developed on the basis of the finite element method (FEM). The key point of this method is the absence of elements and the nodes free from the elemental restraint, which makes it very flexible and simple in pre-processing. It utilizes the nodes of local support domain to construct shape functions to achieve the accurate approximations of the local domain. Approximations of EFM are of high order and boundary conditions are enforced simply, because the radial point interpolation method (RPIM) is used to construct shape function. Therefore, EFM is more suitable to simulate complex models than FEM. First, the boundary value problem and the corresponding variational problem of direct current resistivity forward simulation are derived starting with the partial differential equation of current field. Second, the construction of RPIM shape function is introduced in details. Third, equations of the global weak form EFM for direct current resistivity are derived in details based on RPIM shape function. Then, a Fortran program is written according to the equations. By this program, a homogeneous half-space model was used to verify our element free approach. At the same time, we compared the solutions of EFM and FEM in details which shows that the solutions of EFM are more accurate. Furthermore, the solutions indicate the correctness and effectiveness of the EFM for direct current resistivity forward simulation. Finally, we improve the simulation accuracy successfully by refining nodes arbitrarily, and the solutions of EFM forward simulation for complex geoelectric models show that EFM has a high degree of flexibility.

Crustal magnetic anomalies and geological structure in the yunnan region

Abstract: Based on the geomagnetic field model (NGDC-720) established by the U.S. National Geophysical Data Center, the spatial variations of crustal magnetic anomalies in the Yunnan region were studied, including the distribution of magnetic anomalies and their gradients, attenuation of magnetic anomalies with altitude, and the contributions of components with different wavelengths to overall magnetic anomalies. The magnetic anomalies were compared with other geophysical data such as gravity anomalies, terrestrial heat flow, and seismic activities to reveal similarities and differences, and the relationship between crustal magnetic anomalies and geological structure was studied. The research results show that the magnetic anomalies are relatively weak in the Sanjiang (Three Rivers) and western Yunnan orogenic belts to the west of the Lijiang-Xiaojinhe and Red River fault zones, and relatively strong in the rhombic block. The crustal magnetic anomalies in the study region were mainly generated by the shallow magnetic bodies superposed on the background of weak magnetism basement. The satellite magnetic anomalies show that the middle Yunnan depression area has clear dipole field characteristics. The positive and negative magnetic anomaly zones distributed along the Red River fault zone have consistent strikes with that of the faults. The Lijiang-Xiaojinhe fault, the Red River fault, the Kangding-Yiliang-Shuicheng fault and the Mile-Shizong-Shuicheng fault zones surrounding the rhombic block are transition belts between strong and weak magnetic anomalies. The places with active seismicity and the areas with high terrestrial heat flow values have negative or relatively weak crustal magnetic anomalies.

Time‐domain electromagnetic diffusion and imaging depth for airborne electromagnetic data

Abstract: To study the electromagnetic (EM) diffusion of a time-domain airborne electromagnetic (AEM) system, we first calculate the frequency-domain EM field inside the earth based on the continuity boundary condition and then transform it into time-domain via a Fourier transform. We calculate the EM fields induced by a step pulse for a homogeneous half-space and a two-layer earth model and display the EM diffusion in the earth as 2D vectors or 3D animated time-varying contours (like the “smoke ring”). These time-domain current rings display the true EM diffusion, because they demonstrate the spatial variation and decay of underground EM fields with time. The study of the EM current rings shows that the EM diffusion is strongly influenced by the resistivity structure inside the earth. In a conductive earth, the current ring diffuses slowly but decays fast, while in a resistive earth it diffuses fast but decays slowly. The induced current for a vertical magnetic dipole forms a single current ring that propagates with time outward and downward, while for a horizontal magnetic dipole, the induced current forms two stacked current rings in the underground, diffusing with time into the deep earth. Based on the EM current ring, we find that the imaging depth for AEM data is about 0.55 times the EM diffusion depth. By showing the underground induced current as vectors and 3D time-varying animated contours, the EM diffusion and smoke ring are clearly observed. An animated EM smoke ring offers more information than a static contour of current density. The relation between imaging depth and diffusion depth is further confirmed by the smoke rings. Study on EM smoke ring can not only offer an insight into EM diffusion in the earth, but can also assist in airborne EM data interpretation.

Surface deformation and early warning magnitude of 2016 kaikoura (new zealand) earthquake from high‐rate gps observations

Abstract: On 13th November 2016, the Kaikoura region of New Zealand was struck by a major Mw7.8 earthquake. In this study, coseismic deformation field is derived from 1 Hz high-rate GPS observations based on the GAMIT track solution module, combining with PCA spatial filtering method firstly. Then the 5 s peak displacement of P-wave (Pd) and the peak ground displacement (PGD) are extracted from the real-time simulated kinematic displacements of the trackRTr module. Finally, the warning magnitude is calculated from the statistical regression model. Our results indicate that the duration time of the kinematic deformation is up to 2 min. The KAIK and HANM stations, which are closest to the epicenter, have secondary severe deformation. And the deformation amplitude of the north stations of the epicenter is larger than that of the south. The static coseismic deformation field from high-rate GPS observations shows the characteristics of the focal mechanism of strike-slip after thrust. In addition, the Pd warning magnitudes from different stations have a significant difference, with the maximum magnitude difference of Mw2.5. Considering the timeliness and reliability of the warning magnitude jointly, the warning magnitude from the four-station PGD joint warning method of reasonable spatial distribution can reach its initial stability (Mw7.56) at 23 s after the event, while final stability (Mw7.78) at 110 s, which is consistent with the USGS moment tensor magnitude (Mw7.8).

Locating of concealed skarn iron ore deposit based on multivariate information constraints: a case study of beiya gold mine in yunnan province

Abstract: Skarn deposit is one of the main gold-polymetallic deposits in Beiya, Yunnan, and constrained by its porphyries, structures and stratums, the favorable ore-prospecting spaces are contact zones between intermediateacid rocks and carbonatite. Based on the physical characteristics of rocks, we realized the transition between target geological body and the geophysical field and extracted the useful information. Skarn iron deposits are characterized by low-medium resistivity in contact zone, low density of porphyries, high susceptibility and high polarizability of the iron ore. Utilizing the geological and geophysical information, we analyzed ore-controlling factors in different stages, implemented the locating of concealed skarn iron deposits, established a geophysical exploration mode, verified the validity of the study method on the periphery of the ore district and obtained favorable exploration results. We also proposed a locating and predicting method for the concealed skarn iron deposits, which is applicable to Beiya and other similar ore-forming geological conditions.