Table of Content

10 February 2023, Volume 37 Issue 01

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Geophysics and Information Technology

Development of the Chinese Continental Scientific Deep Drilling: Perspectives and Suggestions

ZOU Changchun, WANG Chengshan, PENG Cheng, WU Caowei, GAO Yuan

2023, 37(01):  1-14.  DOI: 10.19657/j.geoscience.1000-8527.2022.101

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As the most direct and important method to detect the Earth’s deep interior, scientific drilling plays a key role in solving the strategic technological issue of deep Earth exploration. This study briefly reviews the development and current situation of domestic and international continental scientific drilling and deep drilling, and analyzes the characteristics and trends of continental scientific drilling development. We summarized the Chinese Continental Scientific Drilling, its key scientific and technological issues, as well as challenges and opportunities. Accordingly, we proposed the development goals, priorities and approaches of the Chinese Continental Scientific Drilling. Continental scientific deep drilling can provide a unique pathway for investigating global concerns in Earth sciences, such as geodynamic processes, geohazards, mineral and energy resources, and environmental changes. However, its implementation depth is constrained by ultra-high temperature and ultra-high pressure in harsh borehole environments. Modern scientific advances have promoted the development of various technologies in continental scientific drilling, which provide important support for ultra-deep and extra-deep drilling. The Chinese Continental Scientific Drilling should aim for 9,000-15,000 m extra-deep boreholes, focusing on scientific issues in the fields of ultra-deep, deep-time and deep-observation. Priority development directions can include deep Earth tectonics, deep-life, deep-climate, and deep-resources. The priority detection technologies can include those for drilling, logging, and long-term observation in ultra-high temperature-pressure environments. Priority should also be given to the experimental technique development for ultra-deep matter, dynamics processes, and petrophysics. This would promote a breakthrough in the capacity and level of Earth interior detection in China.

Lithospheric Electrical Structure of Eastern Segment of Central Asian Orogenic Belt and Its Tectonic Implications

LI Bo, JIN Sheng, YE Gaofeng, WEI Wenbo

2023, 37(01):  15-30.  DOI: 10.19657/j.geoscience.1000-8527.2022.069

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The eastern segment of the Central Asian Orogenic Belt (CAOB) in central Inner Mongolia has always been a hot research field in the Earth’s internal dynamics and global change. Tectonic study in this region is of great significance given its important role in understanding the CAOB formation. A 364 km-long magnetotelluric sounding (MT) profile in the eastern CAOB is collected in this study. The profile starts from the northwest near the national border in Dongwuqi of Inner Mongolia, and extends to the southeast through the Northern Orogenic Belt (NOB), Solonker Suture Zone (SSZ) and Southern Orogenic Belt (SOB), and terminates about 30 km west of Wengniuteqi of Inner Mongolia. Based on the data analysis results, 2D inversions were conducted on the dataset. Resulting model shows that the electrical structure of the lithosphere along the profile is characterized by NS-trending transverse blocking. The NOB is generally characterized by low resistivity; The SSZ is the transition zone of the electrical characteristics of the whole section from low to high resistivity; The SOB is mainly characterized by high resistivity. The low resistivity characteristics of NOB indicate that the region is unstable, which may be caused by the residual oceanic crust or asthenospheric upwelling after the Paleo-Asian Ocean closure. The SSZ electrical structure indicates that a new tectonic event may have occurred after the suturing. The high resistivity characteristics of the SOB indicate that the basement is stable and “cold”, and the fluid content is very low, with the geometric characteristics of the electrical structure reflecting the thickened lithosphere. The regional electrical structure characteristics along the profile indicate that new tectonic events, such as asthenospheric fluid ascent and lithospheric thickening, may have occurred after the collision between the Siberian and North China Cratons. In addition, the regional electrical structure is consistent with the suture zone characteristics, which provides new deep geophysical evidence for the continuous accretion model of tectonic evolution in the eastern CAOB.

Dam Structure and Hydrogeological Conditions of Tianchi Lake in Tianshan Mountains: Perspectives from Electrical Resistivity Tomography and Accumulation Deposit Structure

SHANG Yanjun, JIN Weijun, YI Xuetao, JIANG Dongting, HASAN Muhammad

2023, 37(01):  31-39.  DOI: 10.19657/j.geoscience.1000-8527.2022.070

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The accumulation dam structure at the northern exit of Tianchi Lake in Tianshan Mountains is controlled by its origin and evolution, which affects its groundwater hosting and seepage characteristics. The bedrock burial depth and water diversion structure are crucial to the dam stability, which remains unresolved for many years. Based on geological survey, we used electrical resistivity tomography, optical luminescence dating and hydrochemical analysis to detect the structure of Tianchi Lake accumulation dam, and to determine the age of material formation and the hydrogeological features of the dam. The results show that the Tianchi accumulates are over 100 meter-thick, and the upper shallow massive boulder layer and lower aquifer is 30-40 meter and 30-50 meter thick, respectively, which was underlain by igneous rock complex. Groundwater in the middle part of the dam infiltrates intensively and replenishes the western Xiaotianchi Lake. There are many overflow points and discharge channels on the left bank of the Feilong Stream in the east, which control the seasonal occurrence of shallow spring there. An EW-striking fault (inclining to the upstream) is present beneath the hill of the meteorological station, which forms an aquitard in the Tianchi Lake and rises the phreatic water level. The major water diversion structure model (composed of fault and stratigraphic structure) in the accumulation body is preliminarily constructed. We calculated that the groundwater discharge of the Tianchi dam is 1200 m³/d, whilst the total water discharge is 52×10⁴-113×10⁴ m³/d (from winter to summer).

High-precision Earthquake Locations and Deep Fault Characteristics Beneath Xianyou Area, Fujian Province

GUAN Luning, JIANG Guoming

2023, 37(01):  40-47.  DOI: 10.19657/j.geoscience.1000-8527.2022.071

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Xianyou area is located in the middle part of the Fujian southeastern coastal region. Historical seismicity events around Xianyou are relatively rare, and the area belongs to a weak seismic area with few earthquakes. However, since Jinzhong Reservoir in this area started to operate in May 2010, earthquake activities became more frequent near the reservoir area. To deeper our understanding in the seismicity, seismic distribution characteristics, and search for local concealed faults, based on the seismic travel time data provided by the China Seismological Bureau, the double-difference relocation method was used to relocate the earthquakes in the Xianyou area in the past decade, and more accurate source positions were obtained. According to our results, fitting deep faults to search for concealed faults. The results also show that: (1) The relocated hypocenters are more concentrated. They can be divided into four active regions according to earthquake occurrence time, and are mainly distributed along the NW direction on both sides of the secondary Shicang fault at Shaxian-Nanridao. (2) Focal depth of Xianyou earthquake swarm after relocation is mainly 8-11 km. The focal depth of the seismic belt on the left side of the Shicang fault is 6-12 km; The seismic strip on the right side shows obvious stratification. The earthquakes on the northwestern side of the upper layer are relatively disperse, while those on the southeastern side are relatively intensive. The focal depth is 6-12 km on the left side, while there are fewer earthquakes on the lower layer, with focal depth of 14-23 km. (3) According to the relocated source position, three deep fault planes are fitted by the singular value decomposition method, and they dip to the southwest and strike northwest, consistent with the dip and strike of the Shicang and Tongguan faults. Based on previous studies and our results, we speculated that Shicang fault is not the main seismogenic fault, but the deep steeply concealed faults on both sides of it, which are indirectly affected by the reservoir impoundment, triggering earthquakes.

Three-dimensional Magnetic Structure and Geological Structural Characteristics of Shuangjianzishan in Southeastern Inner Mongolia

JIA Zhengyuan, WANG Fenggang, SUO Kui, GUO Lei, GUAN Ye

2023, 37(01):  48-57.  DOI: 10.19657/j.geoscience.1000-8527.2022.072

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The Shuangjianzishan Ag-Pb-Zn deposit, located in the middle-southern section of the Great Xing'an Range, is the largest silver-polymetallic deposit discovered in the region in recent years. It is a hydrothermal deposit that has undergone multistage mineralization. Magnetic anomaly has a strong correlation with mineralization, and the magnetic structure can well reflect the ore-controlling structures. In this study, building on various existing information, a three-dimensional inversion of high-precision magnetic data of about 1200 square kilometers in the study area is carried out, and the local three-dimensional magnetic structure within 5 km is obtained. The main conclusions are: (1) The high magnetic intrusion is mainly distributed in the middle and northwest, and shows a NE-SW-elongated distribution; (2) The study area comprises four major structural units and six sub-structural units; (3) The overall local fault structure shows as a NE-SW trend, and the southern fault structure changes to NW-SE trending; (4) There are various concealed magmatic rock units in the central and southeastern parts of the study area, which are mainly intermediate-felsic igneous rocks.

Using the Potential Field Separation Method to Extract the Gravity Anomalies Caused by the Ice Sheet in the Polar Region: Taking Model Test as An Example

TANG Hai, WANG Jun, ZOU Changchun, GUO Lianghui, LIU Yandong, ZHOU Zhiwen, FANG Yuan

2023, 37(01):  58-66.  DOI: 10.19657/j.geoscience.1000-8527.2022.06.073

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To improve the gravity data processing quality and reduce the impact of super-thick ice sheet on gravity data interpretation, it is important to separate the gravity anomalies caused by ice sheet from the superimposed anomalies. To address this problem, we establish two continental polar ice structural models and simulate the Bouguer gravity anomalies of these models. Subsequently, three separation methods (i.e., polynomial fitting, upward continuation, and preferential filtering) are used to extract the ice sheet-related gravity anomalies. Based on the results, the application effects of different separation methods are compared and analyzed. Our results demonstrate that the polynomial fitting method is effective when the density interface fluctuation is relatively gentle, but artificial anomalies are easily introduced when the interface fluctuates greatly. The upward continuation method works well in discriminating anomalies caused by shallower sources. However, due to the greater depth of the polar model and unreasonable continuation height selection, insufficient separation occurs in the test. The preferential filtering method yields better separation result for the complex model, but its performance depends greatly on the frequency band selection. Therefore, when stripping the gravity anomalies caused by polar ice sheet, due to the complex geological conditions (e.g., thickness and fluctuation of polar ice sheets), available geological and geophysical materials should be adopted to determine the appropriate separation method for specific conditions.

Three-dimensional Inversion for Resistivity Method Based on Multiplicative Regularization

XIE Haijun, TAN Handong, MA Fengqun

2023, 37(01):  67-73.  DOI: 10.19657/j.geoscience.1000-8527.2022.074

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To reduce the multiplicity of geophysical inversion solution, additive objective functions are usually used, i.e., the data term and regularization term. Inversion based on additive objective function has the problem of optimizing the regularization factor, which usually requires much inversion calculations. This study systematically analyzed and implemented the 3D resistivity inversion method, based on multiplicative objective function (i.e., multiplication of the data term and regularization term). The problem of optimizing regularization factor is absent in the inversion of multiplicative objective function. We used the unstructured finite element method for resolving the 3D forward problem, and the L-BFGS (Limited-memory Broyden-Flecher-Goldfarb-Shanno) method for 3D inversion. The feasibility and effectiveness of our approach is verified by using the synthetic data of the theoretical model. The results show that the inversion method (based on multiplicative objective function) can reliably recover the resistivity value, shape and position of anomalies.

Three-dimensional Full-time Airborne TEM Modeling with Shift-and-Invert Krylov Subspace Method and Response Characteristic Analysis

DONG Yan, TAN Handong, FU Xing

2023, 37(01):  74-83.  DOI: 10.19657/j.geoscience.1000-8527.2022.075

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To study the fulltime response characteristics of airborne TEM with complex geoelectric models, it is necessary to develop a 3D forward algorithm with transmitted waveform consideration. Based on the unstructured tetrahedral mesh and the Shift-and-Invert Krylov subspace (SAI Krylov) method, we achieve the fulltime 3D edge finite-element simulation of airborne transient electromagnetic, by using the source processing technology-based dipole discretization technique. We simulate the shape of the transmitting loop by topography, and then the instantaneous current pulse technology is used to simulate the transmitting waveform. The numerical simulation algorithm developed here is verified by the analytical solutions of the uniform half-space model, under the excitation of step wave, half-sine wave, triangle wave, and trapezoidal wave, and by the calculation results of the 3D FETD algorithm of the VTEM actual transmitting waveform. The anomaly spherical model with uplifted terrain is designed, and the characteristics of airborne transient electromagnetic response are calculated and analyzed. The fulltime 3D numerical simulation algorithm of airborne TEM (based on SAI Krylov subspace) is suitable to calculate the response of complex geoelectric models, and is highly accurate.

Response Characteristics of 3D Tensor CSAMT

LIU Xiao, SONG Shuanglin, TAN Handong, YU Feiyang, WANG Wanhui, YAN Yujun, LEI Xiang

2023, 37(01):  84-89.  DOI: 10.19657/j.geoscience.1000-8527.2022.038

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Tensor CSAMT can fully describe three-dimensional (3D) geoelectric information, and is more suitable for geological exploration under complex geological conditions. Strategy of decomposing the total field into primary and secondary field is adopted here, and the large-scale linear equations are formed by different approximate differentiation. The 3D forward modeling results of tensor CSAMT are obtained according to these equations. By calculating the response of low-resistivity and high-resistivity targets, the Kania apparent resistivity and apparent impedance phase show low and high anomaly for low-resistivity and high-resistivity body, respectively. The frequency of which the apparent impedance phase reaches the extreme value is higher than that when the apparent resistivity reaches the extreme value. Tensor CSAMT is more sensitive to low-resistivity body than to high-resistivity body. Under the same condition, the abnormal area position of high-resistivity body moves upward compared with low-resistivity body. A survey case in the study area shows that the underground abnormal body can be qualitatively judged via the Kania apparent resistivity anomaly, which facilitates geological problem solving. This study provides a basis for tensor CSAMT 3D inversion.

3D Inversion of Time-lapse Controlled Source Audio-frequency Magnetotellurics

HU Qixuan, TAN Handong, YU Cui

2023, 37(01):  90-98.  DOI: 10.19657/j.geoscience.1000-8527.2021.156

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Time-lapse monitoring is an effective way to observe underground dynamic changes. Geophysical inversion results could be affected by systemic factors, including measurement errors, noise pollution in the studied environment, and the inversion ambiguity. If time-lapse geophysical data is inverted separately at different times, the results may have poor comparability, which would affect the monitoring of time-lapse geophysics. For the actual needs of the controlled-source audio frequency magnetotelluric (CSAMT) in the monitoring field, we integrated the observation data at different moments for inversion, and constructed resistivity models at different moments (mutually constrained) for three-dimensional inversion of the time-lapse CSAMT. Three types of models were designed to perform without time-lapse constraint inversion and time-lapse inversion comparison trial calculations of synthetic data, which verified the inversion algorithm and its effectiveness. The inversion results show that by adding adjacent time model constraints, the time-lapse controllable source inversion can better focus on the anomaly locations, reduce the noise impact and local environment changes, and minimize the impact of inversion artifacts. Our findings have laid a good foundation for the application of time-lapse CSAMT.

Effect of Transmitter Waveform on 1D Modeling and Inversion of Transient Electromagnetic Method Data

WANG Shengtao, LIN Changhong, WANG Xudong

2023, 37(01):  99-106.  DOI: 10.19657/j.geoscience.1000-8527.2022.059

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We have developed a 1D modeling and inversion algorithm for transient electromagnetic method (TEM) data with transmitter waveform. The source is a horizontal rectangular loop for the implementation. Through the Duhamel integral, the step response was converted to the response generated by the trapezoidal waveform. In the inversion, the Occam strategy is adopted to obtain a smooth layered model. The synthetic examples show that the time derivatives of the vertical magnetic fields, dB/dt, and the inversion results are distorted to different extents by the turn-on, steady and turn-off times. The investigated model response shows that the turn-on, steady, and turn-off times mainly affect the TEM data at late, intermediate-late, and early gate times, respectively. Furthermore, the distortions become greater with increasing durations of the turn-on, steady and turn-off times. Inversion results of the synthetic data indicate that the turn-on times have only minor influence on the inversion results, whilst the turn-off and steady times affect the inversion results of the shallow and deep parts, respectively.

Development of the Analog Circuit in Expendable Current Profiler

LI Pengyu, ZHANG Qisheng, ZHOU Keyu, LIN Zucan, JIANG Xingyuan

2023, 37(01):  107-113.  DOI: 10.19657/j.geoscience.1000-8527.2022.076

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Expendable current profiler (XCP) is an observation instrument for rapid measurement of ocean current based on the principle that ocean current cuts the geomagnetic field to produce induced electric field. When the geomagnetic field is stable, the magnitude of the induced electric field predominantly rests with the velocity of the ocean current. Therefore, the motion characteristics of the current can be explored by measuring the induced electric field originated from the ocean current. In this paper, the analog circuit used in XCP was developed, and the acquisition and preprocessing of electrode signal, compass coil signal and temperature signal in XCP were realized. The main functions of the analog circuit are as follows: (1) the multi-stage amplification of the electrode signal and the coil signal is realized through the INA128 amplification circuit; (2) considering that the frequency of the electrode signal and the coil signal is 16 Hz, a second-order band-pass filter circuit with a central frequency of 16 Hz is added to the circuit to extract the effective signal; (3) compensate hardware circuit is adopted to overcome that strong interference of the induced electric field resulted from the sinking of the XCP probe. The experimental results show that the analog circuit is stable and reliable, and it can filter the noise and extract the front-end weak signal for multi-stage amplification to meet the needs of practical applications.

Application of Robust Principal Component Analysis in Seismic Data Erratic Noise Suppression

FU Yonghai, LI Fan, GAO Jianjun, JIA Hao, YUAN Yijun, CHEN Haifeng, LI Chaolin

2023, 37(01):  114-120.  DOI: 10.19657/j.geoscience.1000-8527.2022.06.077

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Improving the signal-to-noise ratio of seismic data is an important goals of seismic data processing. Although conventional seismic data de-noising methods can effectively suppress random noise, they are less effective in suppressing outlier or erratic noise with non-Gaussian distribution. In this paper, we present a robust principal component analysis (RPCA) method to suppress erratic noise in seismic data. This method yields ideal noise-free data by implementing robust low-rank approximation to seismic data in the frequency-space domain. For the constructing objective function, the nuclear norm minimization model is used to obtain ideal low-rank approximation data, and the l₁ norm minimization model is adopted to estimate the outlier noise. Furthermore, the inversion problem is solved with the augmented Lagrange multiplier method. De-noising results of the synthetic data and real data verify the effectiveness of this method. Meanwhile comparison with de-noising results of the conventional F-XY domain prediction filtering method also demonstrates that the proposed method can both effectively suppress erratic noise and protect the effective wave energy properly.

Inter-layer Multiple Attenuation Method based on Predictive Filtering

SHOU Hao, SUN Luping, DING Ling

2023, 37(01):  121-126.  DOI: 10.19657/j.geoscience.1000-8527.2022.078

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Because of the small time difference with the reflected signal, it is difficult to completely remove inter-layer multiples at the near offset. The presence of near offset multiples on the gathers increases the inversion multiplicity. In addition, false reflection by multiples on the stack section also increases the interpretation risk. In this study, an attenuation method of inter-layer multiples based on predictive filtering is proposed. First, the multiples of middle and long offset are attenuated by dip filtering; Second, the gathers containing residual inter-layer multiples are sorted in random order; Third, the residual inter-layer multiples are removed by predictive filtering. Through testing the actual data, our method presented here has good attenuation effect on inter-layer multiples, with short offset and small time difference.

Quantitative Characterization of Hydrate Occurrence Mode in Marine Pore-filling Gas Hydrate Reservoirs: Constraints from Acoustic and Resistivity Log Data

WANG Shengyi, ZOU Changchun, PENG Cheng, WANG Hongcai, LU Jingan, KANG Dongju, WU Caowei, LAN Xixi, XIE Yingfeng

2023, 37(01):  127-137.  DOI: 10.19657/j.geoscience.1000-8527.2022.066

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In marine pore-filling natural gas hydrate reservoirs, hydrates are mainly produced in four occurrence modes: contact-cemented, grain-coated, matrix-supported, pore-suspended. Discrepancies in reservoir elastic-electrical properties are caused by different hydrate occurrence modes, and integrated acoustic and resistivity log data processing can effectively identify the hydrate occurrence mode. We used petrophysical models to simulate the reservoir acoustic and electrical responses, based on common log data (incl. resistivity and longitudinal velocity), and identified hydrate occurrence modes and calculated hydrate saturation. We also quantitatively characterized the occurrence modes, via calculating the relative proportion of the four hydrate occurrence modes. Actual drilling data from three typical marine hydrate reservoirs (i.e., Shenhu area of the South China Sea, Blake Ridge in North America, Hikurangi margin in New Zealand) were used as examples to quantify the hydrate reservoir occurrence mode: (1) In the hydrate reservoir at Shenhu Site SH2, hydrates are predominantly matrix-supported, accounting for ~64% of the total; (2) In the reservoir at Blake Ridge Site 994C, the hydrates are mainly of contact-cemented (27%) and grain-coated (51%) modes; (3) In the hydrate reservoir at Hikurangi Site U1518B, the hydrates are mainly of grain-coated (32%) and matrix-supported (47%) modes. Previous experimental studies on hydrate formation and occurrence mode show that the hydrates are more likely to be stored as contact-cemented, grain-coated and matrix-supported mode, which supports the analytical reliability. The integrated acoustic and electrical log data processing here enables the quantitative evaluation of hydrate reservoir occurrence mode in marine pore-filling gas hydrate reservoirs.

Effect of Methane from Natural Gas Hydrate Decomposition on Marine Life

GUO Zihao, LI Canping, CHEN Fengying, GOU Limin, WANG Hongtao, ZENG Xianjun, LIU Yilin, TIAN Xinyu

2023, 37(01):  138-152.  DOI: 10.19657/j.geoscience.1000-8527.2022.034

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With changing seabed environment and the intensification of global warming, more natural gas hydrates have decomposed and released large amount of methane into the oceans. Some of the methane would ascend through the seawater and enter the atmosphere, which would increase the atmospheric greenhouse gas concentration, and thereby exacerbate global warming. From the perspective of methane release and migration pathways, the direct/indirect effects of methane on marine life are elucidated and summarized: (1) hydrates decompose to release methane, which is an indispensable compound in lifeform formation. This provides energy and material for autotrophic microorganisms, and supplies the food base of cold-spring biota. This maintains cold-spring biota based on a food chain of chemoautotrophic bacteria, which multiply in the cold-spring ecosystem; (2) some of the methane gas would diffuse and dissolve in the seawater, which causes seawater acidification. Seawater acidification would both affect the biosynthesis of calcium carbonate shells (calcification) and accelerate the shell dissolution; (3) as a strong greenhouse gas, the released methane in the atmosphere would exacerbate global warming. In addition, the melting of the polar permafrost would also release large amount of methane into the atmosphere, which generates an adverse cycle. The warming of seawater would affect the survival, metabolism, reproduction, development and immune response of marine life and other biological activities. Our findings provide important reference for future research on the impact of methane on marine ecosystem.

Remote Sensing Alteration and Structure Analysis Based on Fractal Theory: A Case Study of Duobaoshan Area of Heilongjiang Province

ZHAO Zhonghai, CHEN Jun, QIAO Kai, CUI Xiaomeng, LIANG Shanshan, LI Chenglu

2023, 37(01):  153-163.  DOI: 10.19657/j.geoscience.1000-8527.2022.019

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Mineralization-alteration information extraction and structural interpretation are of great significance for metallogenic prediction. Fractal theory can be used to reveal the fine structure of hidden information in complex terrain features, in the field of remote sensing geology, and the theories and new methods for remote sensing mineralization/alteration information extraction and quantitative analysis of geological/structural interpretations. This study mainly used Landsat-8 OLI images and related geological data to study the alteration and structural fractal characteristics of the Duobaoshan area in Heilongjiang Province, based on analysis theory. The interference removal+band ratio+principal component analysis+fractal threshold segmentation method was used to extract the alteration anomaly information. Dimension contour map of linear structure and alteration was obtained by box dimension method of fractal theory, and its spatial distribution and fractal characteristics were analyzed. The structural and alteration information were superimposed to compare with the high value area of structural and alteration fractal dimension, and with the metallogenic geological background. The results show that the high-value area of remote sensing alteration fractal dimension coincides with the alteration data-intensive area, and the structural fractal results are consistent with the spatial distribution of ore-forming structures. The superimposed information combines the advantages of the two, i.e., eliminates interference, narrows the exploration scope, and more effectively highlights the favorable ore-forming sites. Here, the fractal feature analysis method of remote sensing alteration anomaly and structural information superposition is first applied. This method can increase the utilization and accuracy of remote sensing information, and is also more consistent with the actual metallogenic geological background and exploration results. It can be used as a new theory and method for comprehensive prospecting prediction of remote sensing data, and provides theoretical basis and prospecting direction for future exploration work in the area.

Inversion of Gravity Anomaly Based on AlexNet Deep Neural Network

LIU Caiyun, LI Mengdi, XIONG Jie, WANG Rong

2023, 37(01):  164-172.  DOI: 10.19657/j.geoscience.1000-8527.2022.079

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In order to solve the problems of traditional inversion methods, such as dependence of initial model and long time for calculation, this paper proposes a noval gravity anomaly inversion method based on AlexNet deep neural network. This method designs an Alex inversion network (AlexInvNet) for gravity anomaly inversion inspired by classical deep neural network AlexNet firstly; constructs labeled datasets by forward modeling using a large number of synthetic density models secondly; uses the dataset train the AlexInvNet thirdly; and finally inputs the gravity anomaly data to the trained AlexInvNet to obtain the inversion result directly. The inversion experimental results of synthetic models show that this method can invert the position and density of anomaly body accurately, with good generalization and anti-noise ability, better than the full connected network deep learning inversion method. The field data inversion result demonstrates that this method can solve gravity anomaly inversion problem effectively.

Magnetic Anomaly Inversion Based on Convolutional Neural Network

XUE Ruijie, XIONG Jie, ZHANG Yue, WANG Rong

2023, 37(01):  173-183.  DOI: 10.19657/j.geoscience.1000-8527.2021.150

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To resolve the problems of traditional inversion methods, such as initial model dependence and long calculation time, we proposed a magnetic anomaly inversion method based on convolutional neural network. With this method, a number of magnetic anomalous body models were designed to perform forward simulation, which generated various sample data-sets. Subsequently, a new VGG magnetic anomaly inversion network (VGGINV) was designed based on the classic convolutional neural network VGG-13. After that, the sample data-set was used to train the network and optimize the network parameters. Finally, inversion experiment was performed based on this theoretical model and actual field data. The experimental results show that the proposed method can accurately invert the position and magnetization of magnetic anomaly, with strong learning ability and certain generalization ability, and can effectively solve problems in magnetic anomaly data inversion.

Relationship Between Rainfall and Sunspot Activity Cycle in Zhengzhou Based on Wavelet Analysis

QI Shiyang, SHEN Chen, LIU Xiaobiao, ZHANG Mengjiao, MA Xinming

2023, 37(01):  184-196.  DOI: 10.19657/j.geoscience.1000-8527.2022.080

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In order to study the correlation-ship of sunspot activity and regional rainfall, we used the continuous wavelet transform method to study the precipitation data of Zhengzhou city (Xinzheng station) since 1980 and the variation of the number of sunspots, and studied the correlation between the two in different periods. Further, rainfall and sunspots were proceed by cross wavelet transform and wavelet coherence spectrum analysis. The rainfall was predicted by sunspots observation number according to the relationship between the two. The results show that there are positive and negative differences in the correlation between the two in different periods. The first main rainfall period scale is a 21-year one, with a 14-year period obtained under this main period scale. Similarly, the first main sunspot period scale is a 16-year one, with a 11-year period obtained under this main period scale, consistent with experience value. The three extra year of rainfall (than sunspots) can explain the positive and negative differences in the curve correlation at different periods. The correlation between rainfall and sunspots is significant on an 8 to 12 year timescale (1992 to 2008) with regular time lag. The rainfall vs. sunspot activity correlation is important on the timescale of 2-4 a and 7-10 a, with regular lag during 1991-2004 and 2006-2013, respectively. There is no obvious correlation between the two in other time scales. Correlation analysis showed that according to the empirical formula for the time delay, rainfall can be predicted from sunspot observations. The results show that the latest peak rainfall is near 2022, close to the 2021 “7·20 heavy rain” in Zhengzhou. The next rainfall valley year is likely around 2028, and the precipita-tion fluctuation or decrease may be greater than before.

Geochemistry and Remote Sensing Geology

Differences of Cadmium Mobility in Paddy Soils from Different Parent Materials in the Pearl River Delta and Its Influencing Factors

WANG Jiaxin, HOU Qingye, YE Danjun, YANG Zhongfang, YU Tao

2023, 37(01):  197-207.  DOI: 10.19657/j.geoscience.1000-8527.2023.01.21

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With the rapid development of economy, heavy metals in soil exceed the environment standards more and more seriously, especially for Cd. The mobile fraction of Cd in soils is affected by various factors, but there are few reports about its influencing factors from the perspective of different parent materials. We collected and measured 235 paddy soil samples which were formed by Quaternary sediments, acid intrusive rocks and terrigenous clastic rocks in the Pearl River Delta. The physicochemical characteristics of paddy soils were summarized, and factors affecting total and the mobile fractions of Cd were discussed. The results showed that there were significant differences in physicochemical properties, total Cd concentrations of paddy soil formed by different parent materials. The average concentrations of CaO, K₂O, Na₂O, TFe₂O₃, cation exchange capacity (CEC), pH, organic matter and clay in paddy soil formed by Quaternary sediments are significantly higher than those of acid intrusive rocks and terrigenous clastic rocks. Cd in paddy soil developed from Quaternary sediments exceed the standard most seriously. Meanwhile, the concentration of Cd in mobile fractions extracted by different metho-ds in this type soil is also the highest. The correlation between the total Cd concentration and soil physicoche-mical parameters in paddy soil formed by terrigenous clastic rocks is stronger than that of the other two types of parent materials. The correlation between the total Cd concentration and soil physicochemical parameters in paddy soil formed by acid intrusive rock is weak. The total Cd concentration has an important impact on Cd in mobile fractions. In addition, the correlation between Cd in mobile fraction and pH, organic matter, TFe₂O₃ of paddy soils developed from Quaternary sediment is significantly higher than that of the other two types of parent materials. The correlation between Cd in mobile fraction and Tl, CEC, clay and Mn in paddy soil formed by terrigenous clastic rocks is significantly higher than that of the other two types of parent materials. Cd in mobile fraction is mainly affected by the total Cd,CEC, TFe₂O₃ and Mn in paddy soils formed by acid intrusive rocks.

Distribution of Trace Elements and Its Influencing Factors in Jiedong District, Jieyang City, Guangdong Province

LI Hui, WEN Hanhui, CAI Limei, XU Yaohui, LUO Jie, MEI Jingxian, XU Shubang

2023, 37(01):  208-216.  DOI: 10.19657/j.geoscience.1000-8527.2023.01.22

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The five elements of B, Cu, Mn, Zn and Mo in the soil of Jiedong district of Jieyang City in Guangdong Province were studied. Based on the contents and distribution characteristics of these trace elements, the influencing factors of trace element contents in soil were analyzed from four aspects: parent material, land use mode, pH and organic matter content. GIS spatial analysis, SPSS mathematical statistics and correlation analysis were used to analyze the content, spatial distribution characteristics and influencing factors of soil trace elements in Jiedong district. The results show that the average contents of B, Cu and Mn in Jiedong district are 18.0 mg/kg, 14.5 mg/kg and 313 mg/kg, respectively, and the contents are all in a deficient level. The ave-rage content of Zn is 77.3 mg/kg, which is generally at a relatively rich level. The average content of Mo is 1.31 mg/kg, which is abundant. Correlation analysis shows that B, Cu, Mn, Zn and Mo are all affected by the parent material and land use patterns. The contents of B and Mn are the highest in soil derived from siltstone, Cu and Mo are the highest in soil derived from tuff, Zn is the highest in soil derived from Quaternary sediments. The contents of B, Cu are the highest in farmland soil and Mn, Zn and Mo are the highest in construction land. Soil pH has a positive correlation with B, Cu, Mn and Zn (P<0.01). Soil organic matter is positively correlated with B, Cu and Zn (P<0.001) and negatively correlated with Mn.

Geochemical Characteristics and Influencing Factors of Germanium in Surface Soil of Lishui District, Nanjing City

ZHOU Mo, LIANG Xiaohong, ZHANG Ming, WEN Bangyong, TANG Zhimin, ZHAN Long

2023, 37(01):  217-226.  DOI: 10.19657/j.geoscience.1000-8527.2023.01.23

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Germanium (Ge) is an essential trace element for life and has extensive health care effects on the human body. It is valuable to develop Ge-rich soil, whereas the research on soil Ge is still insufficient in China.Based on the results of land quality geochemical survey in Lishui district, Nanjing, the content and spatial distribution characteristics of Ge in surface soil and the influence of geological background on soil Ge were studied in this paper.The results revealed that the average Ge content in surface soil of Lishui district was 1.40 mg/kg, which was mainly controlled by geological background and its spatial distribution was highly consistent with geological background.The high value area of Ge content is mainly the outlying area of J₃d^1-2, and the lithology is mainly trachyandensite and andesite, while the Quaternary sediment distribution area has relatively low Ge content.There was no significant relationship between Ge and pH value in the soil, there was a certain negative correlation with organic matter content, and an obvious positive correlation with Cr, Co, Ni and As. The Ge-rich soil area in the study area is 84.18 km², accounting for 10.84% of the total area of the whole region, and there is basically no Ge deficient area in the whole region.In this paper, the content, spatial distribution and influencing factors of Ge in surface soil of Lishui district, Nanjing were discussed, which can provide basic data for the ecological geochemical study of Ge in soil in China, and have guiding significance for the scientific development and utilization of Ge-rich soil resources.

Remote Sensing Prospecting Information Extraction and Mineral Prediction Based on Medium and High Resolution Data in Hongshishan, Inner Mongolia

LIAN Chenqin, FENG Zhiming, LIU Yongxin, LEI Congcong

2023, 37(01):  227-232.  DOI: 10.19657/j.geoscience.1000-8527.2023.01.24

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The Hongshishan area of Inner Mongolia is located in the East Tianshan-Xing’an metallogenic belt and has good metallogenic conditions. However, poor natural conditions and low level of basic geological survey restrict mineral exploration in this area, so it is of great significance to use remote sensing to conduct polymetallic prospecting. OLI data were used in this study, and the mineralization anomalies such as iron stain and hydroxyl group were extracted by mask, lossless linear stretching, eigenvector principal component transformation, density segmentation, anomaly filtering, while the fracture information was extracted by pseudo-color synthesis and linear stretching. Based on the multivariate information, two target areas were delineated and one of them was further explored. High-resolution PLEIADES data, image fusion, color synthesis, histogram stretching and other methods were used to delineate the giant quartz veins in key exploration areas. On the basis of remote sensing interpretation, the field investigation proves that there are several mineralization points in the key exploration area. This study shows that the combination of medium-resolution OLI data and high-resolution PLEIADES data can greatly improve the efficiency of geological prospecting, which has important guiding significance for further prospecting in this area.

Tourism Earth Science

Characteristics and Scientific Values of “Canyon and Danxia” Landform in Hualong County, Qinghai Province

LIU Xinlan, ZHANG Xujiao, LI Junlei, WANG Yifan, ZHANG Xiangge, YUAN Xiaoning, WANG Kaiya, WANG Chongge, LIU Jiang, HOU Engang

2023, 37(01):  233-244.  DOI: 10.19657/j.geoscience.1000-8527.2023.031

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“Canyon and Danxia” is a composite landscape formed by both internal and external geological processes, and has great landscape and scientific value. The Lamu river in Hualong county (Qinghai Province) is a primary tributary of the Yellow River, where typical angular unconformity and Danxia landform are developed. This makes Hualong a suitable area for studying the Qinghai-Tibetan Plateau uplift and the Yellow River evolution. Aiming at elucidating its morphology, genesis, and chronology, this field study focuses on the rock formation, strata and tectonic setting of “Canyon and Danxia” landform. We systematically concluded the driving force and formation processes of the landscape in the Lamu canyon, and discussed its implications to the Qinghai-Tibetan Plateau uplift and the Yellow River evolution. The Lamu canyon is composed of the Neoproterozoic Hualong Complex gneiss (~900 Ma) and Paleogene Xining Group red glutenite (~54 Ma) with an angular unconformity. The Danxia landform in the canyon was developed when the Qinghai-Tibetan Plateau started uplifting at 8 Ma. After the Hualong Basin was cut by the Yellow River at 1.1 Ma, the canyon developed “Canyon and Danxia” landform via continuous river incision and gravitational collapse. The canyon is precipitous and the Danxia landform is lifelike, which are typical, unique and rare national-class geoheritage. It has important research value on the uplift of the Qinghai-Tibetan Plateau, the evolution of the Yellow River, and the Cenozoic climate and environment.