(1) high-altitude exploration
Through high-altitude exploration (remote sensing, satellite gravity, aeromagnetism and airborne radioactivity), the concealed rock mass and ore-controlling structures are identified, the concealed state of important ore-bearing strata and structures (regional deep faults and major geological interfaces) and rock mass is revealed, the distribution of concealed geological bodies and deep geological bodies is inferred, a three-dimensional inferred comprehensive information geological map which is of great significance to the analysis of metallogenic geological background and the division of metallogenic belts is compiled, and the technical route for the evaluation and research of metallogenic prospect and deep prospecting potential is carried out.
1. airborne geophysical technology
Airborne geophysical prospecting is fast, efficient, economical and less affected by topography, and can be used for resource exploration in deserts, swamps, lakes, oceans, forests and areas where terrain cutting is serious and people can't reach. Realize fast, efficient, multi-scale and deep stereo detection of resources.
Evaluation of effectiveness of aerogeophysics: The results of aerogravity and magnetic exploration are effective methods to study regional geological structures and geological prospecting, and play an important role in metal mineral exploration. Gravity and magnetic exploration can directly find ore bodies under favorable conditions, or indirectly find ore bodies by studying rock bodies or structures related to the deposit.
2. Aerial remote sensing exploration technology
Taking Gejiu tin-copper polymetallic metallogenic area in Yunnan Province as an example, this paper studies the standardized application of aerial remote sensing geological solid mineral exploration, which mainly includes the following two aspects: ① interpretation of line ring structure (data: ETM+(129044: 2000/1/02); ② Extraction of alteration anomaly information from multispectral remote sensing (data: ETM+(129044: 2000/1/02).
Evaluation of aerial remote sensing exploration effect: the key of aerial remote sensing exploration technology lies in the acquisition of remote sensing data. The data obtained by Gejiu at present include MSS image data (resolution 80m) of multispectral scanners carried on landsat- 1 and landsat-2 satellites, TM images (resolution 30m) of thematic imagers carried on landsat-4 and landsat-5 satellites, and Hyperion data (EO- 1 satellite) of hyperspectral satellite remote sensing. The application of aerial remote sensing data in solid mineral exploration mainly has the following three characteristics.
Remote sensing image (1), with its macro, objectivity, richness and multi-level geological information, has achieved more and more obvious results in geological research and mineral prediction. Not only the linear structure and ring structure in remote sensing images provide a lot of information for the study of ore-controlling geological structures, but also the extraction of remote sensing alteration information based on the spectral curves of rocks and minerals is of great significance for delineating alteration zones and predicting metallogenic targets.
(2) The development trend of remote sensing is the improvement of spatial resolution and spectral resolution. The remote sensing data used by predecessors are mainly TM data. Using TM data to study the structural information in Gejiu area is still very effective, but in order to extract more accurate structural and alteration information, higher resolution remote sensing data must be used. At present, there are high-resolution remote sensing data such as SPOT and Quickbird on the market;
(3) Metallogenic prediction based on comprehensive information: extracting structural zones and alteration zones is the main target of remote sensing information extraction in this area. Using the strategy of combining structural information with alteration information extraction, combined with geophysical, geochemical and geological information in the working area, the multi-source information is comprehensively analyzed to delineate the metallogenic prospect.
(2) Surface geochemical exploration
This paper studies the prospecting methods, technical parameters, prospecting results and main problems adopted in different exploration periods, especially the successful experience and failure lessons in extracting indicator anomalies, delineating prospecting targets, identifying concealed mines and improving exploration depth. This paper systematically summarizes the historical achievements from the gradual exploration of surface placer tin ore to interlayer oxide ore and skarn sulfide ore in rock contact zone after 2007, and then to the newly discovered granite-type tin-copper polymetallic deposit in rock mass, puts forward the key technical parameters and workflow of ground-scale mineral exploration, and demonstrates the technical route of delineation, prediction and evaluation of prospecting targets in the periphery and depth of the mining area by combining typical geological, geophysical and geochemical exploration profiles and some deep-hole data.
1. Investigation of regional water system sediments
Through systematic sampling and analysis of river valley sediments (including sediments near lakes), the distribution of elements in river sediments is studied, geochemical anomalies are found, and prospecting areas and favorable metallogenic areas are delineated, which provides a basis for further fine geochemical exploration and geological investigation. The sediments in the river valley system are mainly washed by surface water, which brings loose materials on the ground slope into the river valley and continues to be transported along the river valley, in which abnormal materials are distributed in an elongated shape along the transport direction. Therefore, geochemical exploration personnel are commonly known as scattered streams. The source of this anomaly should be traced against the direction of sediment transport. The anomaly source may be hundreds of meters or even thousands of meters upstream of the anomaly sample point, and the spatial relationship between ore and anomaly is alienated. However, due to the long transportation distance of this abnormal substance, the anomaly formed is easy to find, and it can be found with sparse samples, so it is especially suitable for the rough prospecting stage.
Technical parameters and effectiveness evaluation of regional water system sediments;
Sampling and test requirements: ① Sampling medium: Fine-grained materials (silt or silty sand) are generally collected in river sediment measurement, and fine sand can be collected if there is no sampling place for such sediments. The metal content in sediments with different particle sizes is different, so it is difficult to collect similar substances at all sampling points in the work. Therefore, the variable bias caused by sampling particle size difference can be greatly suppressed by uniformly sieving the collected samples (generally passing through 80 mesh sieve). In the area covered by aeolian sand, it is necessary to mine extremely coarse-grained materials to eliminate the interference of aeolian sand; ② Sampling density: The sampling density of river sediment measurement is related to the size of the target area to be delineated and the amount of information to be obtained. 1:The sampling density of river sediments in the area of 200,000 is 1 ~ 2 /km2, and then a sample is assembled in a 4km2 grid. In the national planning, the sampling density of river sediments is per square kilometer 1 point, and the sample combination within 4km2 is submitted for analysis, which is the highest sampling density in China. The drainage sediments in Gejiu area are 4km2；; ③ 39 elements (including 6 compounds) were tested in each combined sample. Therefore, river sediment survey can find geochemical anomalies in the region and obtain prospecting information.
2. Tectonic geochemistry
Tectonic geochemistry mainly studies the complex transformation of ore-controlling structures and the spatial distribution law of ore-forming elements under certain geochemical conditions, discusses the migration law of ore-forming fluids and the evolution process of chemical elements under the control of tectonic stress field, reveals the occurrence law of useful substance components in various tectonic environments, and guides metallogenic prediction, prospecting and production and development. Tectonic geochemical exploration techniques and methods are significant progress in new techniques and methods of concealed deposit exploration since 1970s, which can directly and quantitatively evaluate the ore-forming material composition of deep ore bodies. The former Soviet Union first applied the method of fault structure geochemistry to find concealed ore, and achieved remarkable results. China began to introduce geochemical exploration methods in the early 1970s, and applied this method to the prospecting practice of concealed deposits after the mid-1980s. Tectonic geochemistry can effectively infer deep concealed mineralization from the anomaly of surface element formation.
Tectonic geochemical method is feasible in Gejiu mining area and has the following three advantages.
(1) The stratigraphic conditions in Gejiu mining area are relatively simple, mainly carbonate rocks of Gejiu Formation. The geochemical data of fault tectonic rocks can exclude the interference of various backgrounds to some extent. Compared with surrounding rocks, the content of tectonic rocks is higher, which can enhance the deep metallogenic information. The former is generally several times, dozens to hundreds of times. Tectonic activities make faults a channel for the distribution of ore-forming materials, which leads to abnormal mineralization of faults and contact zones, so tectonic rocks are particularly obvious.
(2) Various ore bodies in Gejiu are controlled by faults and fault structures. Firstly, for vein sulfide deposits far away from the granite contact zone, there are east-west main faults, secondary faults associated with the main faults and the intersection of faults and favorable strata. Generally, the deflection position along the strike of the main fault is the best, and the ore body along the fault plane tends to be thicker from slow to steep. The secondary fracture intersecting or parallel to the main fault widens the fracture zone and makes the ore body thicker and richer. Secondly, for layered deposits (interlayer oxide deposits) far away from the contact zone, the position and shape of ore bodies are mainly controlled by stratigraphic lithology and structure. Generally, interlayer oxide deposits are shallow buried and controlled by surface structure, and ore bodies are produced in groups and belts. The ore-bearing strata are related to the emplacement height of ore-forming granite bodies. The structural ore-controlling property of this kind of deposits is mainly manifested in the control of folds, faults and contact structures on the distribution of ore bodies; Thirdly, for the skarn deposit in the granite contact zone, the structural ore control of the deposit shows the dual control of contact structure and fault structure in the mineralization process. The ore body is located in complex rock mass, especially in the structural intersection zone.
(3) Gejiu fault is developed, and the surface marks are obvious, which is conducive to the development of tectonic geochemical sampling.
This book studies the chemical data of the structural area of Gaosong ore field, and discusses the demonstration process of delineating the prospecting target area by using structural geochemistry.
Considering all kinds of methods and actual geological conditions, the lower limit of anomaly of Ag, As, Cu, Mn, Pb, Sn and other elements is finally determined: Ag is 0.15; As is15; Cu is10; Mn is 200; Pb is110; Sn is 1 1 (unit × 10-6).
Pan-kriging interpolation gridding is performed on the tectonic geochemical data of main ore-forming elements to generate the trend surface diagram of elements (Figure 4-40). Combined with the lower limit of anomaly, the area larger than the lower limit of anomaly is extracted to evaluate the tectonic geochemical primary halo anomaly:
Sn: The main abnormal areas are concentrated in the northern part of the study area, with a large area. The main distribution areas are as follows: ① At the intersection of JD.COM-Lianhuashan-Song Ge fault, the highest Sn content in the area can reach 660× 10-6, with an average value of 17.03× 10-6, which is much higher than the lower limit of the whole area; ② The granite uplift in Songshujiao ore field lies between Changnaotang fault and Lutangba fault, with the highest Sn content of 15000× 10-6 and the average value of 293.32×10-6; ③ At the intersection of Song Ge -F 1 15 fault in the east of Dajing where the10 ore group is located, the abnormal area is large, with the maximum value of 203× 10-6 and the average value of 9.78×10-6; ④ In the middle of the study area, along the Mawei fault, the primary halo anomaly is multi-peaked, with the maximum value of 35.9 1× 10-6 and the average value of 9.00× 10-6, and the element content is generally uniform; ⑤ In the south of the study area, at the intersection of the hump mountain and the explosive magazine fault, the maximum value is18.71×10-6, and the average value is 5.9 1× 10-6, which is slightly higher than the lower limit of anomaly; There are also some small primary halo anomalies, such as the local section of Dajingshan fault in Tuofengshan survey area, and there are small-scale local anomalies in the local section of Axizhai fault in Axizhai survey area.
Cu: The main abnormal areas are basically consistent with Cu, and the main abnormal areas are concentrated in the northern and central parts of the study area, especially the Dajingdong-Mahuitou-Lutangba fault zone, which is large in scale and has the highest content, being180.21×10-6.
Figure 4-40 Anomaly Diagram of Primary Halo of Main Metal Elements in Gaosong Ore Field
Pb: The anomaly area is mainly located in the southern and northern sections of Lutangba fault in the study area, especially at the intersection of Lutangba fault, Tuofengshan fault and explosive magazine fault, with large-scale primary halo anomaly; In addition, there are local anomalies in Axizhai survey area.
Zn: the abnormal area is basically consistent with Pb.
Ag: The abnormal area is mainly concentrated at the intersection of Lutangba fault and explosive magazine fault, and there are obvious Ag anomalies in the middle area of Machui fault and the hump mountain survey area.
Mn: The abnormal area is mainly located in the south-central part of the study area, between the explosive magazine and the hump mountain fault, and in the local area of Dajing Nanshan in the hump mountain area. There is also a certain manganese anomaly area in the Lutangba fault area in the northeast.
Through the above analysis, the Gaosong ore field has roughly delineated five favorable mineralization areas from north to south (Figure 4-4 1). ① The clamping area between Changnaotang fault in the northeast of the study area and the northern part of Lutangba fault is Songjiao ore field and granite uplift, which contains primary halo superimposed by Sn, Zn and Ag; (2) Near the intersection of Dajingdong and Lutangba fault, the west side of Lutangba fault and the north side of Dajingdong fault are superimposed with primary halos including Sn, Cu, Pb, Zn and Ag; ③ The clamping area of Mahuitou fault, Gao 'a fault and Lutangba fault: it is a structural favorable place where Sn, Cu and Pb primary halos are superimposed; ④ Intersection of Hump Fault and Dadeng Nanshan Fault: Mn anomalies are common in this area, as well as Zn and Ag anomalies; ⑤ The southern section of Lutangba fault at the intersection of explosive magazine fault and hump mountain: There is abnormal superposition of multi-element primary halo, including Sn, Cu and Zn. , is the axis of Wuzishan anticlinorium.
Fig. 4-4 1 primary halo anomaly map of Tian Xi Cu-Pb-Zn-Ag comprehensive structure in Gaosong Mine.
Tectonic geochemical technical parameters and effectiveness evaluation;
Sampling test requirements: ① Sampling media, collecting structural rocks along faults and fractures, mainly brown (hematite) mineralized dolomite, brown (hematite) mineralized dolomite breccia and dolomite in this area; (2) Carry out structural investigation and study at the same time, pay attention to the structural pattern and time evolution law of the investigation area, the discrimination between metallogenic and non-metallogenic structures, and the control of structures on hydrothermal alteration and various dikes. (3) Regular grid sampling is not required, but the layout of irregular grid sampling points must consider the control of the structural framework of the measurement area, and there should be appropriate sample control for large conductive structures; ④ The test and analysis depend on the specific deposit. For Gejiu, the samples mainly quantitatively analyze tin and copper, lead, zinc, manganese, arsenic, antimony, bismuth, mercury, tungsten, molybdenum, silver and fluorine that may be related to tin mineralization, and the analysis accuracy and quality are controlled according to relevant specifications.
Main features and advantages: Tectonic geochemical prospecting technology is to infer deep concealed mineralization by analyzing geochemical halos of ore-forming indicator elements in the structure. Gejiu prospecting exploration has the following advantages: ① strengthening weak anomalies and more effectively detecting weak geochemical anomalies formed by buried mineralization in the deep surface; (2) Reducing the exploration cost, taking the structural framework as the main control standard and adopting irregular grid sampling can reduce the sampling quantity without missing mineralization; (3) It is more convenient to explain anomalies because the control of structure on mineralization and halo is fully considered; ④ Concealed mineralization does not necessarily occur directly under the abnormal center, but depends on the appearance of abnormal structures formed by roots. Faults can make the center of tectonic geochemical anomalies obviously deviate from the metallogenic center; ⑤ Tectonic geochemistry has an effective prospecting significance for oxidized ore bodies and vein ore bodies in this area, and also has an indication function for deep-fault skarn ore bodies; ⑥ Research shows that in areas with good landscape geological conditions, 1: 5000 and 1: 2000 are used to delineate the prospecting target area, and1:1000-1:500 is used to check and dissect the anomalies and construct the original structure. Lead, zinc and manganese; w、Mo； The abnormal combination of arsenic, antimony, bismuth and ore-forming elements has good evaluation significance for deep prospecting. ⑦ Like other geochemical exploration methods, the structural primary halo is also limited by surface exposure, cap rock conditions and fault structure development. Surface anomalies are not necessarily mine-induced anomalies, and there are ore bodies in the deep, but they are not necessarily surface anomalies, so it is difficult to determine the depth of ore bodies reflected by anomalies.
3. Energy spectrum measurement
Among the ore-forming hydrothermal activities related to granite, there are U and Th hydrothermal activities. Granite, especially late granite, has the highest content of U and Th in all kinds of rocks. U and Th are enriched in the late stage, which can enter the fluid phase and become important elements of ore-forming hydrothermal activity. Generally, the contents of U and Th in limestone strata are low, and the superposition of different changes caused by hydrothermal activity is easy to show in low background. Therefore, the energy spectrum measurement by detecting the radioactive intensity of U, Th and K samples can show that. The geological characteristics of Gejiu mining area and the open mineralized hydrothermal activity system provide the possibility for energy spectrum measurement. From 2000 to 200 1, Institute of Geochemistry, Chinese Academy of Sciences conducted γ -ray spectrum measurements in Axizhai and Daqing East Area of Gejiu mining area, which provided a basis for prospecting and exploration. In the surface bedrock measurement of Gaosong ore field in Gejiu mining area, the energy spectrum intensity values representing U and Th can reflect the intensity of ore-forming hydrothermal activity to a certain extent, and the higher the U/Th value, the stronger the near-ore alteration, which can be used as a reference to measure the abnormal effectiveness.
The contents of U and Th in soil are much higher than those of surface bedrock and tectonic rocks, and one or two orders of magnitude higher than those of surface bedrock. In addition, the contents of U and Th in soil samples of different profiles are quite different, which is suitable for known mineralization. Because the soil represents the local homogenization effect, the random stability of sampling is good. Because the content of uranium and thorium is much higher than that of bedrock, the energy spectrum measurement is rarely disturbed by background and direct interference. In addition, due to the high content of U and Th in tectonic rocks, the energy spectrum measurement of weathered superimposed soil with tectonic rocks may show the tectonic hydrothermal activity at the measurement point or profile to some extent than that of bedrock without tectonic rocks.
In Axizhai survey area, the total track anomaly measured by surface bedrock and soil energy spectrum is basically consistent with the U-track anomaly range, and the total track anomaly range is slightly scattered than the U-track anomaly range, which is suitable for a wider range of th activities. Compared with the anomaly of soil energy spectrum, the anomaly of soil energy spectrum is more confined to the structural fault zone, because the soil contains weathered structural rocks with high radioactive content, which leads to the anomaly in the structural fault zone with strong mineralized hydrothermal activity.
Combined with the anomaly of U-channel and U/Th value, the high anomaly area of U-channel is basically confined to the triangle of Ziaxi fault and Ziaxi fault. If the high U-channel anomaly and high U/Th value are taken as the center of ore-forming hydrothermal activity, the center of ore-forming hydrothermal activity in this area can be limited to the triangle sandwiched by Qi 'axi fault, Qi 'axi fault and Gao 'axi fault. Moreover, the center of mineralization activity is likely to be at the intersection of Qi 'axi fault and Ma 'draft fault and the eastern region, and the soil energy spectrum is abnormal. The difference between them may reflect the deviation between hydrothermal activity center (source) and metallogenic center. It reflects the migration direction of ore-forming hydrothermal solution in this area.
Energy spectrum measurement can solve the following two geological problems.
(1) Study and delineate the distribution range of hydrothermal mineralization alteration zone. For example, in hydrothermal sulfide mineralization alteration zone, sericitization, argillization, potassium feldspar and other potassium alterations often occur. At the same time, it often contains some axis and thorium radioactive elements. Therefore, the distribution of hydrothermal sulfide mineralization zone and the prospecting prospect of metal deposits can be delineated simply and quickly by γ -ray spectrum. (2) The boundary and distribution of strata magmatic rocks and metamorphic rocks can be accurately and quickly delineated, and even the boundary and distribution of smaller geological units in the above-mentioned geological bodies, such as the distribution of sedimentary rocks, magmatic rocks and metamorphic rocks, and even the stratification in sedimentary rocks, the boundary between central facies and marginal facies of intrusive rocks and other major geological problems. So as to achieve the purpose of indirect prospecting.
4. Geochemical methods of soil secondary halo
Soil geochemistry is a geochemical exploration method to systematically collect loose ground cover samples, analyze their element content or other geochemical characteristics, and find soil anomalies in order to achieve the purpose of mineral exploration.
Geochemical technical parameters and effectiveness evaluation of soil secondary halo;
According to People's Republic of China (PRC) * * and China Geology and Mineral Industry Standard "Specification for Soil Geochemical Investigation" DZ/T0 145-94, the main methods, technical requirements and rules in soil geochemical investigation are stipulated, which are applicable to geological exploration of metal minerals. Soil survey for geological exploration of uranium, geothermal and nonmetallic minerals.
Soil geochemistry has the following characteristics in solving the prospecting problem: ① sampling is easy and it can adapt to different geological landscapes and geological conditions; ② As an important exploration object of surface geochemical exploration, soil has the advantages of easy detection, little artificial influence on sampling, strong representativeness and objectivity. Combined analysis with bedrock primary halo and structural primary halo can complement and correct each other, which may provide more and more comprehensive deep prospecting information; ③ The delineation of secondary anomalies by soil geochemistry can effectively indicate the prospecting information.
5. Gas geochemical exploration methods
Gas geochemical prospecting methods are called gas logging and gas logging for short. Geochemical exploration with gas as sampling object. According to the medium of gas occurrence, it can be divided into atmospheric gas measurement (ground gas measurement and air gas measurement), soil gas measurement, rock gas measurement, inclusion gas measurement, soil solid gas measurement and so on. By systematically measuring the chemical composition or geochemical characteristics of gas components, it can find gas anomalies related to exploration targets and find or predict targets. The gases used for gas measurement mainly include mercury, iodine, carbon dioxide, sulfur dioxide, hydrogen sulfide, oxygen, hydrocarbon gas, sulfur, carbon oxides, neon, radon and so on.
Validity evaluation of gas geochemical exploration methods;
Gas geochemical exploration method is in the experimental stage in Gejiu area, and has not been used in large-scale mineral exploration practice, so it can be used as an auxiliary means of mineral exploration.
(3) Ground geophysical exploration
In the development of metal ore exploration, the important role of geophysics has gradually emerged. With the deepening of geophysical knowledge, especially the progress of geophysical exploration methods, equipment and data processing, its exploration ability is also constantly improving. At present, under the demand of searching for deep and blind ore, geophysical exploration has gradually made some contributions to the macro-strategy of prospecting.
The basic feature of geophysical exploration is to study geophysical fields and physical phenomena. Such as geomagnetic field, geoelectric field, etc. Instead of directly studying rocks and minerals. The physical field obtained by geophysical methods and techniques is the function of different physical interfaces in rock strata, which contains many information such as structure and sedimentation. Table 4- 19 gives some common geophysical exploration methods in Gejiu area.
Table 4- 19 Table of Common Geophysical Exploration Methods
(4) Underground exploration
As a century-old mine, Gejiu has completed open-pit mining and basic mining. At present, it is mainly mined underground. There are a large number of tunnels and various drilling projects in Gejiu main mines, which provide a foundation for underground exploration. Through the systematic collection of typical drilling, tunnel prospecting data, prospecting engineering and large-scale geophysical and geochemical exploration data, a true three-dimensional ore body model, three-dimensional "soft" (three-dimensional topography, geophysical inversion, digital imaging, etc. ) and "hard (measured borehole data at different elevations)" data are comprehensively simulated, and a three-dimensional (positioning) model of the spatial distribution law of ore bodies is established for deep mining.
Validity evaluation of tunnel-borehole primary halo;
Primary halo in tunnel drilling is a geochemical prospecting method. Through the study of tunnel-borehole primary halo, we can find out the law of underground mineralization and enrichment, including the spatial distribution of single element and the distribution of element combination, and find out the spatial distribution characteristics of elements around the ore body. Inferring ore bodies through the combination of front and back elements can narrow the prospecting target area, and even directly determine the specific target area, which is helpful to study geological structure and find blind ore. At the same time, the systematic analysis of tunnel-borehole primary halo by using geochemical samples in tunnels and boreholes is low in cost and simple in operation, which can be widely used in production practice.
Validity evaluation of the study of grade regularity;
Establishing the three-dimensional grade change model of main ore bodies can effectively explore the spatial change law of main ore-forming elements and effectively guide prospecting. It is required to fully collect the grade data of each middle section and borehole, and find out the change law by using relevant mathematical geology and three-dimensional modeling methods.
(v) Selection of demonstration technologies
According to the metallogenic model and magnetic, density and electrical characteristics of Gejiu super-large tin-copper polymetallic deposit, combined with the accumulation of geophysical and geochemical exploration work for many years, Gejiu mining area can adopt the following combination of exploration methods in deep and peripheral prospecting practice in the future:
(1) Deepen the interpretation of gravity and magnetic data, determine the large structural framework, the distribution of magnetic basement, the possible depth and boundary of concealed rock mass by combining with the extraction of remote sensing structural information, and carry out targeted high-precision magnetic survey and anatomy on the ground when necessary;
(2) Based on the depth interpretation of gravity and magnetic data, the spatial structure (occurrence, scale and shape) of fault fracture zone over 800 ~ 2000m can be explained by using high-power (effective power supply current is more than 5 years) controlled-source audio-frequency magnetotelluric method, and the depth of upper and lower interfaces of low-resistivity geological bodies can be determined. In CSAMT, the occurrence and spatial distribution of rock mass and main strata can be roughly determined. It provides a reference for other geophysical and geochemical methods to verify anomalies and borehole layout, and pays attention to the unfavorable factors brought by human interference in mining areas and areas where surrounding rocks are mainly carbonate rocks, such as large grounding resistance, small power supply current (generally only about 3 years), terrain cutting and large height difference.
(3) TEM and EH4 measurements can be assisted in areas with less interference to further verify the distribution of interlayer fracture zones;
(4) Using the high-precision magnetic survey on the ground and referring to the rock mass structure and spatial structure, quickly find out the distribution of basalt and determine the prospecting direction of basalt-related deposits;
(5) On the basis of the above comprehensive geophysical anomaly evaluation, explain and optimize the anomaly in combination with geological conditions, carry out targeted geochemical survey of structural primary halo, and carry out geochemical sampling of tunnels or boreholes in conditional areas to verify the comprehensive geophysical anomaly.