Comprehensive analysis of remote sensing geology and multivariate information in Yulong copper belt

The comprehensive study of remote sensing geology in Yulong metallogenic belt is an effective method to find the target area of known deposit types in this area. Therefore, the study of qualitative and quantitative interactive interpretation is an important aspect to extract new regional metallogenic information and deepen the existing geological understanding in this area. On the basis of fully collecting and studying predecessors' data, with the purpose of not doing repetitive work and striving for improvement and innovation, we have drawn up a specific research plan as shown in Figure 2- 19.

There are only a few research results (He Yunzhong, 1992) and some image processing data in the remote sensing geological research data in this area. The focus of this study is the quantitative study of remote sensing geology and the comprehensive study of various geoscience information, trying to make the degree of remote sensing geology research in this area take a step forward from qualitative research to quantitative research. The research results show that not only some new genetic information and geological knowledge are obtained, but also the level and accuracy of remote sensing geological research in this area are further improved.

(A) remote sensing image processing

Digital image processing is based on the collected TM image digital tape, which processes the digitally recorded radiation values (pixel values) in order to accurately identify all kinds of remote sensing information and extract functional images and related data that are beneficial to geological interpretation. On the basis of preliminary visual interpretation and research, according to the characteristics of plateau TM images and the geological background of the study area, we chose the following processing methods.

Figure 2- 19 Geological Research Process of Remote Sensing Images

1. Image restoration processing

Image restoration processing generally refers to correcting or compensating radiation distortion, system noise (such as banding phenomenon), random noise, geometric distortion and high-frequency information loss generated in the imaging process. This recovery process is also called "pretreatment".

(1) Striping processing: Striping phenomenon is a kind of system noise with a certain direction and period, which appears as a continuous strip with uniform width in the direction parallel to the scanning line on the image. This phenomenon still exists even after radiation calibration. We equalize the histogram of the basic image and eliminate all possible errors.

(2) Geometric correction: Through the preliminary inspection of the image, we found that the image displayed by the original data has skew and line leakage. Through translation, correction and image mosaic, possible errors are eliminated.

(3) Sampling: According to the selected study area, we sampled the original data in different proportions to ensure that the key study areas and various geological features can be fully displayed.

2. Determination of study area and false color synthesis.

According to the collected data and the preliminary interpretation results, we selected the approximate range of 9715 ′ ~ 98 30 ′ east longitude and 313140 ′ north latitude, and took1/50,000 as the approximate range. TM457, TM53 1 and TM32 1 were compared in the synthesis of pseudo color. The results show that because the study area is located in the southwest plateau, except TM7 band, the near infrared spectrum response value is strong, and the information intensity of other bands is low because of the weak atmospheric radiation. Comparatively speaking, the synthetic effect of TM53 1 is ideal, which not only highlights the general structural lines such as faults, folds and regional large joints in this area, but also shows the ring structure and concealed structure well.

(2) Visual interpretation signs

Yulong metallogenic belt is a part of Tethys-Himalaya metallogenic belt, which is located in Qiangtang-Changdu micro-block (middle section). On the remote sensing image of the study area, the overall structural line direction is NW-NW, faults are developed, and the fold structure image is clear. The main exposed stratum is Triassic, followed by Quaternary loose sediments. According to the research of image visual interpretation and image processing, we summarize the remote sensing geological interpretation marks in this area as follows:

1. Tone mark

Due to faulting, there are different lithology, strata, structures and landforms on both sides, so it appears as abnormal tone line, abnormal zone or abnormal interface on the image. The depth, thickness and concealment of abnormal tone line clearly reflect the linear structural characteristics and the intersection relationship with other structures. At the same time, the difference of block tones on both sides of the linear image also reflects the occurrence of fault structures.

2. Structural signs

Discontinuous distribution of fold turning ends, fault zones and structural lines, regular distribution of rock mass production, discontinuity of rock strata on both sides, sudden interruption of geomorphological features or other structural lines are all clearly shown in the image.

3. Texture features

On the remote sensing images, there are some differences in strata, landforms, water system pattern, structural line direction, strength and distribution characteristics of structural development on both sides of the fault, which provides basic conditions for statistical analysis of remote sensing images. According to the interpretation of these signs, Figure 2-20 is a comprehensive interpretation diagram of the structural framework in this area.

Figure 2-20 Comprehensive Interpretation Map of Structural Framework in the Study Area by Remote Sensing

(3) Visual interpretation and analysis

The structural features of this area are clearly displayed on the image and can be well explained. Except for the near NW-NNW regional faults, secondary folds and faults are developed, and the regional faults are mainly reverse faults, which extend far away. The development of large joints, stratigraphic boundaries and linear image features has created basic conditions for further statistical analysis of linear bodies.

As can be seen from the interpretation map, the fault structures in this area are relatively developed, among which the NW-trending fault is the most obvious, followed by the nearly EW-trending and NW-trending faults. The main frame of NW-trending structure that controls the structure in this area is clearly displayed in remote sensing images. Most cracks are wavy and extend far, reflecting the mechanical properties of compression-compression-torsion. However, the structural development of this group outside this area is obviously reduced and the scale is relatively small. The NE-trending and nearly EW-trending faults in the interpretation area are small in scale, and most of them have straight structural lines and stable extension, intersecting with NW-trending faults.

The NW-trending fault generated in this area is relatively undeveloped, but a hidden fault explained is located in the middle of the map, showing a stable regional extension, which developed earlier than the NW-trending structure. Although this hidden fault has not been mentioned in previous research results, we believe that this hidden fault not only exists, but also plays an important role in controlling the development of structures and the formation of Yulong porphyry copper deposit in this area. This nearly NW-trending concealed fault is located next to the intermediate-acid intrusive rock mass along the Yulong-Xingxing fault line, which is likely to be a channel for magma to enter upwards. In addition, the blocks on both sides of the buried fault show differences in tone, particle morphology, landform and structural distribution characteristics in the whole map.

Fault structures are closely related to the formation and enrichment of various minerals. The fault zone is not only a passage for magma and mineral liquid to rise, but also an important factor to control the deposition and distribution of strata. Therefore, synthesizing all kinds of information and analyzing the genetic characteristics of fault structure itself and its relationship with mineralization not only laid a reliable analytical foundation for further metallogenic prediction, but also provided ideas for further research. According to the results of visual interpretation, we can get the following understanding.

This area is dominated by (1) NW-trending structure, which generally has the characteristics of multiple movements, and its mechanical properties are mostly compressive-compressive-torsional. It plays an important role in controlling and guiding the magma and ore-bearing rocks in the area, forming an obvious magmatic tectonic active zone. Therefore, from the structural point of view, the prospecting work of Yulong metallogenic belt should obviously pay attention to the NW-NE structural belt and its adjacent fault intersection.

(2) Although the NE-trending fault is reflected in the geophysical field, it is not obvious, and it is mainly distributed near the NW-trending fault. Although the scale is small, it is widely distributed. We can see that they are dislocated by NW and NW-trending structures and cut off by NW and NW-trending structures in different parts. Therefore, they may belong to the products of two tectonic stress fields, and it is speculated that most of them belong to shell-like faults and shallow primary structures.

(3) The NW-trending structure, represented by the early buried faults, restricted the development of the NW-trending structure in the later period, which may be a passage for the intrusion of intermediate-acid magma, and it is speculated that it is mainly a buried deep fault. In addition, there are small-scale NW-trending structural outputs in some areas.

(4) Interpretation of linear structure

One of the most effective aspects of remote sensing geological application is the study of geological structure. Remote sensing images can intuitively and realistically reflect various geological structural elements and effectively reveal hidden structures. In particular, remote sensing images show a large number of linear and annular structures, which provide important information for analyzing the relationship between local structures and regional structures, and between shallow structures and deep structures.

Basic geological characteristics of linear body

Linear body refers to any natural line or linear arrangement in remote sensing images. In most cases, it is expressed by its own color line or the difference of image tone and graphic structure on its two sides, or by its own unique terrain or the difference of landscape and water system types on its two sides. In most cases, linear body is related to structural elements, which is actually the surface display of linear geological structure or structural elements. Therefore, we have made a systematic linear interpretation of the study area (Figure 2-2 1).

On the remote sensing image, the study area has some linear image characteristics besides the fault structures in different directions. In the linear image of intrusive rock mass, there is no dislocation or small displacement of rocks on both sides, and most of them show negative topography such as valleys. This linear body reflects the big joint. However, the linear images developed in sedimentary rocks or negative metamorphic rocks reflect stratigraphic boundaries, folds, faults or geomorphological features, with obvious lithological differences. These linear bodies with geological significance can extract geological genetic information through further statistical analysis, and also provide a basic guarantee for further remote sensing geological statistical analysis.

Fig. 2-2 1 interpretation of linear bodies in Yulong copper mine

2. Analysis of ring structure characteristics

Ring structure refers to the ring image related to or controlled by geological process, especially the ring structure of Yulong and Hengxingcuo can be clearly seen in the remote sensing image of this area. Interpretation and analysis show that the formation of this annular image feature may be controlled by the following actions, or by the combination of these actions: ① the annular image formed by intrusive body and possible concealed rock mass; ② Annular image formed by alteration zone or contact metamorphic zone; (3) Annular images formed by fold structures or possibly concealed fold structures; (4) Ring image formed by tectonic landform.

(5) Statistical analysis of image features

Remote sensing technology and methods have formed two branches today. Traditional "image remote sensing" technology emphasizes the graphic characteristics of data, and common sensors (cameras) and corresponding analysis technologies (visual interpretation) have been applied for a long time, and have been proved to be practical and effective by extensive application (Chen Jianping, 1997, 1998). Using different methods of remote sensing geostatistics, the information reflecting the genetic characteristics of rock mass is extracted, and the genesis and contrast of rock mass are comprehensively analyzed, which provides quantitative and graphical information for the genetic analysis of rock mass. The tectonic evolution of the interpretation area is long-term, multi-stage and complex superposition in time, which are reflected in the statistical analysis results of linear bodies. It is the characteristics of these tectonic activities and the differences in time and space development that control and restrict the geomorphology, hydrology and lithology in the region. Therefore, the characteristics of rock mass production area and loose sedimentary development area are different linear body characteristics, which represent the different genetic relationship between tectonic activity and magmatic activity. The trend of remote sensing geological research is to infiltrate macro-geological research into different micro-geological research levels and branches; Combine the characteristics of image visual interpretation with computer image processing and statistical analysis; Comprehensive analysis of different geoscience research results can improve the applicability and effectiveness of remote sensing geological research.

1. Extraction of statistical parameters of linear bodies

Linear body refers to any natural line or linear arrangement in remote sensing images. Linear bodies are mostly related to structural elements; Generally speaking, the orientations of linear bodies are almost orthogonal, and most of them have preferred orientations. Therefore, the characteristics of linear bodies can reflect the basic structural pattern of a region.

On the basis of line interpretation, we collected the basic parameters of statistical analysis: line length (L), direction (G) and line number (N). Figure 2-22 is the histogram of linear volume length and frequency in this area. The curve characteristics close to normal distribution show that the distribution of linear volume length is random, which means that human factors in linear volume interpretation have not caused systematic errors. In other words, the linear body interpretation results can objectively reflect the structural geological characteristics of this area, and the interpretation results are true and reliable.

2. Linear bulk density and frequency analysis

The isodensity map of linear bodies reflects the numerical and structural characteristics of the spatial density distribution of linear bodies. Combined with the frequency analysis of linear bodies, it can provide deep structural information and prospecting clues. Figure 2-23 is an isoline diagram for calculating the length of linear bodies in each grid with a sampling grid of 40×20, and Figure 2-24 is an isoline diagram for calculating the number of linear bodies in each grid with the same sampling grid. From the analysis of the characteristics of the two maps, it can be seen that there are obvious differences in the density and frequency of linear bodies on both sides of the NW-trending structural belt, with dense isolines in the southwest and relatively sparse in the northeast. The corresponding distribution of the NW-trending fault zone is consistent with the outline arrangement of the linear volume density isoline graphic structure (Figure 2-25), and there is an obvious gradient zone in numerical value, which reflects the overall distribution characteristics of faults in this area.

Figure 2-22 Histogram of Linear Volume Length and Frequency

Figure 2-23 Linear Volume Density Diagram

Figure 2-24 Linear Volume Frequency Diagram

Figure 2-25 Isodensity Diagram of Structure

Linear volume density and linear volume frequency are different in genetic sense. The concept of linear volume density refers to the sum of linear volume lengths per unit area, which is mainly controlled by the magnitude of the force and the time effect of its stable duration, reflecting the strength of the force of crustal movement and the persistence of tectonic movement. The concept of linear body frequency refers to the number of linear bodies per unit area, which mainly depends on the control of micro-cracks and micro-geomorphological characteristics produced by tectonic action, reflecting the intensity of crustal movement and the characteristics of tectonic swell. Therefore, the linear density and linear frequency reflect the intensity characteristics of crustal movement force and are restricted by the physical properties of the surface; The difference is that the linear plastid density is the development feature of the main structural outline in process of crustal movement and the indication of the overall characteristics of the formed structural belt; Linear body frequency reflects the display characteristics of local tectonic stress concentration parts, and is also the reference information of possible tectonic intersection parts.

3. Azimuth-length frequency analysis of linear body

Figure 2-26 shows the length and azimuth distribution characteristics of regional structures, and Figure 2-27 shows the length and azimuth distribution characteristics of linear bodies. They calculate the sum of the lengths of each group of linear bodies with an interval of 3 in the azimuth grouping of the interpretation area, and draw the graphs of length and frequency respectively. Its purpose is to understand the orientation optimization characteristics of linear body output and the spatial distribution characteristics of the indicated regional structure. The length and frequency of nearly 20% in the figure determine the abnormal line, which is divided into non-abnormal azimuth area (online) and abnormal azimuth area (offline). In terms of structural length and azimuth distribution characteristics in Figure 3-8, the peaks of non-abnormal areas are mainly concentrated in three intervals: 126 ~ 144, 108 and 170, namely, northwest, near east-west and northwest. On the contrary, there is no obvious concentrated area of azimuth advantage in the range below the abnormal line, which shows that tectonic movement has obvious control effect on this area, which is consistent with the visual interpretation results. In the characteristics of line length and azimuth distribution in Figure 2-27, the first-order peaks of non-abnormal areas are also concentrated in northwest, near east and northwest. However, the secondary peak has no obvious direction to form a platform, and almost all the peaks in each angle group are above the abnormal line. Therefore, the developed linear body not only represents the regional main structural framework, but also includes secondary and local structural features and micro-geomorphological features, and the overall characteristics of the linear body reflect the spatial distribution characteristics of regional structural features.

Figure 2-26 Regional Structural Orientation-Length Frequency Diagram

Figure 2-27 Azimuth-Length Frequency Diagram of Linear Body

4. Analysis of azimuth anomaly

Azimuth anomaly is an effective scanning method to reflect the local characteristics of linear azimuth on the basis of linear volume density, which can determine the abnormal target area without bias and reflect the combined characteristics of linear volume distribution pattern. For intrusive rock mass, it generally has the characteristics of local stress field reflected by magmatic rock structure, or the distribution pattern of local linear bodies different from surrounding rock.

Figure 2-28 is to sample the linear body interpretation map with a certain sampling net, calculate the ratio of the length of the linear body with abnormal azimuth in each unit to the sum of the length of the linear body in this unit, so as to obtain the anomaly index of each unit, and then interpolate to make an isoline map (azimuth anomaly map). Obviously, the index is not affected by the density change caused by different structural units. The higher the azimuth anomaly index, the less affected by the regional dominant azimuth structure, so this method can highlight the local structural characteristics more. The comparative analysis shows that: ① most areas in the interpretation area belong to non-abnormal areas, reflecting that the regional structure has obvious control over this area; (2) Yulong copper mine is located at the edge of the intersection of NW and NW structures, but there is no abnormal area distribution, which indicates that the output of Yulong copper mine is obviously controlled by regional structures; ③ Stellar complex is located at the edge of the intersection of local anomalies and structures in different directions, which reflects that magmatic activity in this area is obviously controlled by tectonism.

Figure 2-28 Linear Body Direction Anomaly Diagram

5. Central symmetry analysis

The central symmetry map can be used to delineate the characteristics of equiaxed intrusive rock mass, dome structure and basement structure, and provide important information for prospecting and regional geological research. Put the calculated central symmetry value in the center of the grid and interpolate the contour map. The central symmetry is only related to the central symmetry of the azimuth distribution of linear bodies within the grid, which has the characteristics of definite range of values, monotonous and stable values, and harsh delineation of anomalies. The anomaly of the central symmetric isoline can be divided into three levels.

These include:

Rapid location prediction of main copper deposits (bodies)

Figure 2-29 is the central symmetrical contour map of the study area. It can be seen from the figure that: ① most areas in the interpretation area belong to non-abnormal areas, which are consistent with the overall characteristics of the study area and are mainly composed of sedimentary rocks; (2) Most of the abnormal areas are located near the regional tectonic line, and the abnormal areas in the southwest of the study area are obviously more than those in the northeast, and the major axes of the abnormal areas are slightly arranged in the east-west and northeast directions; (3) Yulong copper deposit and Hengxing complex are located at the edge of the intersection of local anomalies and structures in different directions, reflecting the characteristics of magmatic activity and local structural development.

Figure 2-29 Isogram of Symmetry Degree of Linear Body Center

(6) Multi-source information analysis of target area optimization in Yulong metallogenic belt

Metallogenic prediction of multivariate geoscience information is based on various geological data, through the analysis of geological laws, under the prior premise of geological understanding, and according to the basic theories and methods of various disciplines, comprehensive geological interpretation is made on various geological, geophysical, geochemical and remote sensing data. Based on the characteristics of metallogenic anomalies, this paper analyzes the relationship between various comprehensive information, and describes the basic metallogenic geological characteristics with more comprehensive and detailed comprehensive information. Taking these comprehensive and useful information as comprehensive signs of mineral distribution law, we can distinguish, extract and classify them, so as to get the prediction results of mineral resources.

1. Geochemical characteristics

Geochemical characteristics refer to the objective reflection of the distribution, distribution, enrichment, dispersion, symbiotic combination and migration of the chemical components of the crust and the earth. The geochemical behavior of elements has a general law, and the migration and enrichment law of elements can provide important reference information for regional prospecting. Based on the sediment survey map of1/200,000 drainage system, this study selected the work division consistent with the interpretation area. In the research process, referring to some previous research results and based on different computer processing results, the related contents are discussed around regional prospecting.

Figure 2-30 Statistical Chart of Gold Element Data Characteristics in Yulong Copper Mine Area

According to1/200,000 rural drainage sediment survey map, the node data is read with the grid size of 1 cm× 1 cm. Therefore, it is necessary to statistically analyze these data to determine their reliability. Figure 2-30 is the statistical chart of gold element data, figure 2-3 1 is the statistical chart of copper element data, and figure 2-32 is the statistical chart of molybdenum element data. By comparing the statistical figures of main ore-forming elements, it can be seen that the three kinds of data have random distribution characteristics and have two high-value areas, and the curve characteristics of copper and molybdenum are very similar.

Figure 2-3 1 Statistical Chart of Copper Data Characteristics of Yulong Copper Mine

Figure 2-32 Statistical Chart of Molybdenum Data Characteristics in Yulong Copper Mine

Figure 2-33 shows the distribution and prospect of copper anomalies after treatment. There are two obvious high-value anomaly areas in Yulong copper mine and Hengxingcuo area, and the direction line connecting the two anomalies is NNE, which is in line with the regional concealed structural line (? The direction lines are the same. Figure 2-34 shows the distribution and prospect of gold deposits in this area. The high-value anomaly area of gold element is concentrated near Yulong copper mine, and it is also partially displayed in Triassic strata in this area, reflecting the good prospect of further gold geological prospecting in the periphery of Yulong mining area and metallogenic belt. Figure 2-35 is the distribution and perspective view of molybdenum in this area. The characteristics of the directional line connecting the two anomalies are consistent with the distribution characteristics of copper anomalies, which may reflect their genetic similarity.

2. Trend analysis of main ore-forming elements

Trend analysis is to find out the general variation law of some geological variables after processing, and at the same time, it can also separate the observed values into local variation characteristics. After smoothing, the random components in the data are eliminated, thus achieving the purpose of highlighting the overall characteristics. The key to the accuracy of trend analysis lies in the choice of trend surface time. In the study, the regression equation is used to test the F test value and the simulation goodness EE. The significance test of regression effect is mainly based on the F test value, and EE is only for reference. Table 2- 1 lists the f values at different trend surface times within a certain confidence interval α.

Figure 2-33 Abnormal Distribution and Perspective of Copper

Figure 2-34 Gold Element Distribution and Stereograph

Figure 2-35 Distribution and Perspective of Molybdenum Element

Through the fourth and fifth trend analysis of copper in this area, it is concluded that:

EE4=0.803 F4=2.500 1

EE5=0. 1523 F5=3.5496

Through the fourth and fifth trend analysis of gold in this area, it is concluded that:

EE4 = 0. 1309 F4 = 4.3 143

EE5=0.2402 F5=6.2452

Table 2- 1 F test value table

Through the fourth and fifth trend analysis of molybdenum in this area, it is concluded that:

EE4=0.0859 F4=2.6926

EE5=0. 1668 F5=3.9546

Comparing the calculated results with Table 2-2, it can be seen that for copper, gold and molybdenum, when α=0.0 1, F4 and F5 calculated by quartic and quintic trend surface analysis are both greater than the F test value of 2.42, and the quintic trend surface regression effect is more significant.

For a more intuitive observation, Figure 2-36 is a perspective view of copper trend analysis in the study area. As can be seen from the figure, its distribution presents low anomaly areas in northwest, south and east, and high anomaly areas in the middle. In the north-south direction, there are high anomaly areas in the south and low anomaly areas in the east. Figure 2-37 is the perspective view of gold trend analysis in the study area, and Figure 2-38 is the perspective view of molybdenum trend analysis in the study area. The results of comparative analysis show that the spatial distribution trends of the three main ore-forming elements are similar. Referring to the R-type cluster pedigree diagram of the main ore-forming elements (Figure 2-39), it is proposed that there are genetic relations among the main ore-forming elements of copper, gold and molybdenum, which may be affected by NW-NW concealed faults. ) and related to regional magmatic activity.

Figure 2-36 perspective view of copper quintic trend

Figure 2-37 perspective view of five gold trends

Figure 2-38 perspective view of molybdenum pentad trend

Figure 2-39r- Cluster Pedigree Diagram of Main Metallogenic Elements

3. Comprehensive analysis of regional metallogenic information

Table 2-2 compares the abundance of crustal elements in Yulong Copper Mine and Hengxingcuo area, the abundance of crustal elements in Chinese mainland, the regional background value and the characteristics of main ore-forming elements. Obviously, the main ore-forming elements in the study area have high geochemical background, and the main ore-forming elements in Yulong copper mine and Hengxingcuo area have high abnormal characteristics under high background conditions, which undoubtedly provides strong evidence for finding the same type of metallogenic prospect in Yulong metallogenic belt in this area.

Table 2-2 Abundance characteristics of main ore-forming elements (w B/ 10-6, w(Au)/ 10-9)

As mentioned above, we think that Yulong pluton and Hengxing fault pluton may be controlled by NW-NW concealed structure, and the two points have metallogenic anomalies very different from the background in many aspects, which are very eye-catching in different analysis maps. On the basis of such background data, no matter what method is chosen for comprehensive analysis, the known Yulong deposit and the measures to predict the stars in the target area are the most obvious identification targets. Therefore, what is more striking is whether there is good consistency between the main ore-forming elements in NNE, which is enough to show that they may belong to ore-forming anomalies with the same genesis and background conditions. For this reason, we cut the element distribution profile of Yulong and Stellar Dislocation in the northwest. Figure 2-40 shows the relationship between copper and molybdenum, and the overall trend is very consistent, except that the copper of Yulong is higher than that of Stellar Dislocation. Figure 2-4 1 shows the relationship between copper and gold. The overall characteristics of the two are not consistent. The gold deposit near Hengxingcuo is not obvious, but it reflects that the gold deposit near Yulong has a good prospecting prospect in this direction. Figure 2-42 is a composite diagram of gold, copper and molybdenum isolines. Yulong and Xingxing fault have comprehensive anomalies of gold, copper and molybdenum, and other areas in the area are all gold anomalies.

Figure 2-40 Relationship between Copper and Molybdenum

Figure 2-4 1 copper-gold relationship diagram

Fig. 2-42 Isograms of Copper, Gold and Molybdenum

As we all know, the Yulong metallogenic belt is 400 kilometers long from north to south and 30 ~ 70 kilometers wide from east to west. The direction of the tectonic line gradually changes from north to south and from northwest to southeast, and the north expands and the south converges. Generally speaking, the Yulong metallogenic belt has the following characteristics:

(1) From north to south, there are five large and medium-sized deposits, namely Yulong, Zhalaga, Mangzong, Xiaduo Songduo and Marathon, among which Yulong deposit has the strongest mineralization. In addition, Xiatianduo, Hengxingcuo, Narigongma, Gegongnong, Seri, Rurige, Chamo, Chongbo Motor, Seli and Shashalaniba are all located in the Yulong porphyry copper belt.

(2) Ore-bearing porphyries all intrude into Triassic and its underlying strata, and the direct surrounding rocks are Jiaoga Formation of Lower Permian and Marathon Formation of Lower Triassic, Jiapila Formation of Upper Triassic, Bolila Formation and Adoula Formation, except for the pre-Carboniferous in the northern part of the ore belt in summer. Ore-bearing rocks mainly invade the Lower Triassic Marathon Group (T 1m) and the Upper Triassic Jiapila Group (T3j), among which Jiapila Group is the most important, and the deposits produced are often large and medium-sized. Complex rocks related to ore-bearing rocks and alteration mineralization can emplace or influence the Middle and Lower Jurassic.

(3) According to the isotopic age, Himalayan magmatism in this area can be divided into three relatively early (57 ~ 4 1 Ma), middle (40 ~ 35 Ma) and late (34 ~ 25 Ma) episodes. From north to south, it shows that the alkalinity of ore-bearing rock mass increases, the age value increases, the emplaced horizon ages and the mineralization intensity decreases.

(4) Mineralized bodies in Yulong metallogenic belt are mainly concentrated in the top and side of mushroom-shaped rock mass with high emplacement, as well as the structure and surrounding rock of its internal and external contact zone. No matter the shape of ore body, the type of ore deposit (body), the type of mineral products or the specific enrichment place, it is closely related to the exposed position, occurrence and rock type of rock mass in space. The main ore-bearing porphyries in Yulong metallogenic belt are mostly shallow or shallow to medium denudation, but the denudation depth of ore-bearing porphyries seems to have nothing to do with the denudation degree of ore bodies.

(5) The known ore deposits (bodies) in Yulong metallogenic belt are obviously equidistant along NW-NW direction. If this feature is superimposed with geophysical data (Figure 2-43), its regularity will be clearer.

Therefore, we think that copper (molybdenum) deposits have a good prospecting prospect in the northwest of Yulong metallogenic belt, from Yulong (ore deposit) to Hengxingcuo (ore occurrence) and then to Xiatianduo (ore occurrence). Table 2-3 lists the characteristics of mineralization anomalies (according to Yunnan Geophysical and Geochemical Exploration Team 199 1).

Hengxingcuo copper polymetallic prospecting target area includes Hengxingcuo copper-molybdenum mineralization point and Bailongqiong copper-zinc mineralization point. The important mineralization anomalies are Hengxingcuo (HS-64 B 1), Bailongqiong (HS-57 B 1), Suoru (HS-58 B 2), Glagon (HS-65 B 2) and so on. The existing research results show that the abnormal combination of Cu, Mo, W, Bi and Au in Stellar dislocation is related to porphyry copper mineralization, and the peripheral polymetallic mineralization is related to the hydrothermal activity of intermediate-acid magma. Purple sand shale of Upper Triassic Jiapila Formation is exposed in Hengxingcuo area, and NW-trending faults run through the whole area. Yanshanian granite is produced as bedrock, and Himalayan adamellite intrudes into Yanshanian granite and Middle-Upper Triassic. The main mineralization anomalies of copper-molybdenum deposits in summer are Xiatianduo (HS-82 B 1), Gaogang (HS-86 B 2), Maqianglong (HS-87 C) and Zhequanyong (HS-88 B 2). Many anomalies in summer are closely related to many short-axis anticlines in summer, and their long-axis direction is northwest. The monzogranite porphyry in ore-bearing rock mass is closely related to NW-trending and NW-trending faults, and the abnormal combination of copper, molybdenum, tungsten, bismuth and gold is closely related to ore-bearing porphyry rock mass and copper-molybdenum mineralization. The strata exposed in this area include siltstone of Upper Triassic Duogaila Formation, mudstone mixed with sandstone, shale mixed with sandstone of Adoula Formation, limestone of Bolila Formation, purple-gray green sandstone and glutenite of Jiapila Formation. Middle Triassic limestone sandstones in summer; Many groups of rhyolite and tuff interbedded with sandstone in Marathon Formation of Lower Triassic. Copper polymetallic deposits have been found in the area in summer, copper polymetallic skarn deposits have been found in the periphery of porphyry, and copper molybdenum mineralization has been found in the contact zone inside and outside porphyry.

To sum up, we draw the following conclusions:

Figure 2-43 Distribution Characteristics of Known Deposits (Bodies) in Yulong Metallogenic Belt

Table 2-3 Abnormal characteristics of main ore-forming elements (w B/ 10-6, w(Au)/ 10-9) in Yulong metallogenic belt.

(1) In the geological work of copper deposits in Yulong metallogenic belt, we should strengthen the investment in geological prospecting and scientific research in the area north of Yulong, and the preferred prospecting target area should be Hengxingcuo area, so it is suggested to carry out further work;

(2) Yulong copper mine and its adjacent areas have good gold mineralization, which is worthy of further gold geological research and prospecting;

(3) There is copper-molybdenum mineralization in Yulong metallogenic belt, but whether there is large-scale gold mineralization deserves further study.