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Dongguashan Copper Mine in Tongling, Anhui Province
I. Building blocks

Dongguashan copper mine is one of the most important copper mines in Tongling Shizishan ore field. The geotectonic unit in Tongling area belongs to the middle part of the Yangtze platform depression under the Yangtze paraplatform.

Second, the mining area geology

(1) stratum

The surface of the mining area is covered by Quaternary, and the upper Devonian to middle Triassic (D3W-P2D-T 1Y-T2D) is exposed by drilling. There are many ore-bearing strata in the ore field. From Carboniferous to Triassic, industrial ore bodies of different scales are produced in each stratum. The ore-bearing strata of Dongguashan deposit are Huanglong Formation of Middle-Upper Carboniferous, Chuanshan Formation (C2) and Yinkeng Formation of Lower Triassic (T 1y). The main lithologic characteristics of ore-bearing strata are briefly described as follows:

1.C2 Huanglong Formation and Chuanshan Formation of Upper Carboniferous

This layer is the host part of the main ore body of Dongguashan Copper Mine, with a thickness of 59 ~ 73m. The lithologic characteristics are: the lower part is dark gray thick dolomite, and the bottom is gray-brown to brown argillaceous sandstone cemented timely fine-grained rock with a thickness of 3 ~ 14 cm. The middle part is light-dark gray medium-thick layered limestone. The upper part is gray-light gray thick layered quartzite and dark gray limestone with spherical structure. The lower part is metamorphic gray-white dolomite marble and dolomite marble. The limestone in the middle and upper part is metamorphic to sugar marble. The areas with strong metamorphism are altered into magnesium skarn and calcareous skarn respectively.

2. Lower Triassic Yinkeng Formation (T 1y)

The thickness of this formation is 1 10 ~ 145 m, the lower part is blue-gray thin marl, light yellow calcareous shale with thin-medium thickness and lenticular limestone, and the upper part is light brown-brown calcareous shale with thin-medium thickness limestone. The top is gray thick-thick limestone with a thickness of 8 ~ 30m. After metamorphism, the lower part is grayish brown diopside amphibole and siliceous amphibole mixed with marble and diopside garnet skarn, and the bottom is biotite amphibole mixed with felsic amphibole. The upper part is hornfel mixed with marble, or an interlayer with unequal thickness composed of skarn, hornfel and marble; The top is white thick-extremely thick layered marble, which is often eroded into massive skarn near the contact zone with rock mass.

(2) Structure

The ore field is located in the northeast of Qingshan anticline, the secondary fold of Datong-Shun 'an syncline, and the composite part of the east-west structural magmatic belt of Tongling-Daijiahui (Figure 2- 133). The anticline is 22.5km long and 8km wide, and it is an asymmetric short-axis fold with a strike of 40 ~ 50, and it is "S" shaped on the plane. Some anticlines in the ore field are about 4km long, and the axial plane tends to the southeast, and the northwest wing is steeper than the southeast wing. Due to the influence of superimposed structures in the later period, the shape of the axis of the anticline is complex, with double peaks or multiple peaks, and it inclines or reverses to NW locally, and gradually relaxes and opens below -400 m elevation, with simple shape. On the axis of anticline and the southeast wing, collapse structures and interlayer fracture structures are developed on the interface with great differences in lithology and lithofacies, and the vertical scale decreases from bottom to top. Interlayer collapse structure and fault structure are important ore-controlling structures for multi-layer mineralization, especially the superimposed composite parts with east-west and north-northwest crossing folds are more conducive to mineralization.

The faults developed in different periods in the ore field are composed of east-west, north-south, north-northeast and northwest faults. The intersection of faults in different periods and directions controls the emplacement of magma and the distribution of rock masses in this area.

(3) Magmatic rocks

The exposed area of the rock mass in the ore field is 2.5km2, and the maximum exposed area of a single rock mass is 0.625km2 The magmatic rock mass is controlled by the grid structure and communicates with each other at different elevations, forming a shallow-ultra-shallow grid vein wall system with a length of 3km and a width of about 1km. The shallow and middle-deep magma mainly intruded along the north-south and north-north faults, resulting in small dikes and dikes. It is inferred that the deep part is a "mother-child" compound large rock mass. According to the isotopic composition characteristics of Sr, H, O and S (according to the analysis results of the whole rock sample, the initial ratio of Sr isotope is 0.7095, δ 18O=9.90‰, δD=95.07‰), it is inferred that the magma originated from the deep crust and belongs to the crust-mantle magma. K-Ar isotopic age is 147 ~ 160 ma.

The intrusive rocks are mainly calc-alkaline diorite and granodiorite, followed by alkaline pyroxene diorite and diorite. Late dikes include diorite porphyry, granite porphyry, granodiorite porphyry, lamprophyre and diabase.

The SiO _ 2 content of calc-alkaline intrusive rocks is 59.0 1% ~ 6 1.64%, and the SiO _ 2 content of alkaline intrusive rocks is 50.8 1% ~ 57.32%, both exceeding the average content of similar rocks in China, and the Na2O content is greater than K2O;. . The alkalinity coefficient [w (Na2O+K2O)/w (FeO+Fe2O3+MnO-MgO)] is between 1. 1 ~ 1.4 (the former is slightly higher than the latter). The abundance of trace elements in each rock mass is relatively high, among which Cu and Au are relatively high, with Cu above 65× 10-6 and the highest being 355× 10-6. Au is generally between (2 ~ 10) × 10-9, and the highest is 24× 10-9.

The copper, gold and sulfur deposits in this ore field are closely related to magmatic rocks, mainly calc-alkaline diorite, diorite and granodiorite, followed by alkaline pyroxene diorite and diorite. The closed and semi-closed structures formed by the surrounding rock-rock support grid are often the space where deposits occur.

Three. geology of ore deposits

(1) ore body characteristics

Dongguashan deposit is located in the northern part of Datuanshan deposit in plane and in the deep part of Datuanshan deposit in profile.

1. Distribution, shape, occurrence and scale of ore bodies

This deposit is the largest in the C2 layer of Shizishan orefield (Figure 2- 134). The main ore body is 3000 meters long, 200 ~ 800 meters wide and generally 30 ~ 45 meters thick (the axis of anticline and the side of rock mass are thicker, with the maximum thickness of 85 meters), which is layered and gently inclined. The bottom plate is D3w silty shale (metamorphic amphibole), the top boundary can reach the lower part of Qixia Formation (P 1q), and the bottom boundary is below the top of Yuewutong Formation (D3w). The occurrence of the ore body is consistent with the surrounding rock, and the shape is saddle-shaped, and it is undulating due to the secondary uplift along the strike. It is inclined to the northeast with an inclination of 6 ~ 20. The buried depth of the ore body is -800 ~-900 m, and the scale of the deposit is large.

Figure 2- 133 Geological Schematic Diagram of Tongling Shizishan Ore Field Figure 2- 133 Geological Map of Tongling Shizishan Ore Field

T2t—— Tongtoujian Formation; T2y—— Yueshan Formation; T2d—— East Maanshan Formation; T 1n 2—— the upper member of Nanlinghu Formation; T 1n 1— Lower member of Nanlinghu Formation; T1h-and Longshan formation; T1y-yinkeng formation; η δ ν-pyroxene monzodiorite; η δ ο-syenite diorite; γ δ-granodiorite; γ δ π-granodiorite porphyry; η γ π adamellite; M- marble; Skb-banded skarn skm-massive skarn; Brsk-skarn in breccia tube; Skbr-breccia skarn; Skcu-copper-bearing skarn; Py- pyrite; Pr- pyrrhotite; Gn- iron cap; The bimodal fold axis of Qingshan anticline; 2-minor anticline axis and syncline axis; 3- Broken zone; 4- failure; 5- Unconformity boundary; 6- stratigraphic boundary; 7- stratigraphic group boundary; 8— Boundary of stratigraphic section; 9— Geological boundary; 10- Marble Boundary Line

2. Ore type and ore structure

The ore type is complex. From the floor to the roof of the ore body, it is roughly as follows: copper-bearing amphibole type-copper-bearing serpentine type-copper-bearing pyrrhotite type-copper-bearing pyrite anhydrite type-copper-bearing pyrite type-copper-bearing skarn type, and copper-bearing syenite type appears at the edge of the rock mass. The copper-bearing serpentine rock type is stably distributed at the bottom of the ore body, extending along the bottom horizon of C2+3, and the copper mineralization is weakened, and gradually becomes pyrite layer and serpentine dolomite. Copper-bearing pyrrhotite type, copper-bearing magnetite type, copper-bearing pyrite anhydrite type and copper-bearing pyrite type appear alternately or lack one or two, which are distributed in the middle and upper parts of ore bodies. The copper-bearing skarn type is mainly developed beside the rock mass and distributed in the top and middle of the ore body.

Figure 2- 134 Section of Exploration Line 58 in Dongguashan Copper Mine

Q- four yuan; T 1n—— Nanlinghu Formation; T 1 H3—— the upper member of Longshan Formation; T1h 2-the middle section of Longshan formation; T 1h 1- Lower member of Longshan Formation; T1y-yinkeng formation; P2d—- Dalong Formation; P2L-Longtan Formation; P1g-Gu Feng group; P1q-Qixia formation; C2- Huanglong+Chuanshan Formation; D3w 2—— Upper member of Wu Tong Formation; γ δ π-granodiorite porphyry; η δ ο-syenite diorite; η δ ο skarnized diorite; ηδνbr- breccia pyroxene diorite; Skbr-breccia skarn; 1- fracture zone; 2- copper ore body

Ore structures are mainly layered, banded, massive, disseminated and reticulate. The ore structure includes colloid, triad, aggregate and metasomatic filling. The zoning and ore structure of the above ore types show that the deposit has the characteristics of exogenous and endogenous superposition.

3. Mineral composition

The mineral composition of the ore is complex, and the metal minerals are mainly chalcopyrite, chalcopyrite, pyrite and magnetite, followed by paste magnetite, colloidal pyrite, white iron ore, sphalerite, galena, siderite and a small amount of scheelite, chalcopyrite, natural gold, arsenopyrite, hematite and molybdenite. Non-metallic minerals mainly include garnet, diopside, tremolite, serpentine, anhydrite, talc, yingshi, calcite and dolomite, while minor minerals include phlogopite, actinolite, olivine, silicomagnesite, gypsum, chlorite, epidote and wollastonite.

The ore is mainly composed of copper, sulfur and iron, accompanied by gold, silver, selenium, tellurium and other metals and dispersed elements. The average copper content of the ore body is 1.0 1%, which is rich in the middle and gradually poor in the southwest and northeast. It is rich near the rock mass, and it is gradually poor away from the rock mass. The average grade of gold is 0.24× 10-6, and that of silver is 8.67× 10-6. Copper is rich in copper-bearing pyrite anhydrite, copper-bearing pyrite and copper-bearing pyrrhotite, but poor in other types of ores. Gold and silver are mainly concentrated in the middle of the ore body, and the content of copper-bearing pyrite anhydrite ore is the highest.

(2) Contact metamorphism and surrounding rock alteration

contact metamorphism

Contact metasomatic metamorphism and thermal contact metamorphism are very common in ore fields, with the strongest in the central part, forming a strong metamorphic center in the north-south direction, and the metamorphic degree gradually weakens with the distance from the surrounding rock mass. In the vicinity of the contact zone between rock mass and surrounding rock, contact metasomatism metamorphism is dominant, and thermal contact metamorphism is dominant far from the contact zone. The contact zone between rock mass and surrounding rock can be roughly divided into: granodiorite-skarn granodiorite-internal skarn-massive skarn-layered (banded) skarn-skarn marble (skarn hornblende)-marble (hornblende)-limestone (shale). Because of the different physical and chemical properties of surrounding rocks, metamorphic minerals are also different. General sandstone metamorphic quartzite; Dolomite and dolomite marble are metamorphic to tremolite, olivine and silicomagnesite skarn; Limestone metamorphic marble, local calcium iron garnet skarn; Impurity limestone is metamorphic to diopside and garnet skarn; The argillaceous shale and siliceous rocks are metamorphic to diopside hornblende and siliceous hornblende, and diopside skarn and wollastonite skarn are strongly metamorphic.

2. Hydrothermal alteration

Hydrothermal alteration is common in ore fields, but the zoning is not obvious. The main alterations are potash feldspar, epidote, chloritization, carbonation, silicification, sericitization, kaolin, serpentine and so on. Among them, potash feldspar, epidote, sericitization and kaolin are mainly developed in the rock mass side of the contact zone. Alterations closely related to copper-gold mineralization mainly include potash feldspar, carbonation, silicification and serpentine.

Four. mineralize

(1) Metallogenic conditions and enrichment of ore-forming materials

1. Control of sedimentary strata on copper mineralization

C2+3, the main ore-bearing stratum of Dongguashan copper deposit, mainly controls mineralization from three aspects: the existence of original sedimentary strata, easily explainable lithology and favorable lithologic combination. The primary sedimentary layer is mainly 13 colloidal pyrite layer sandwiched in the dolomite section in the lower part of Huanglong Formation, which was deposited in the transgression period in the early Middle Carboniferous. Colloidal pyrite is strawberry-shaped and spherical, alternating with dolomite to form layered structure. Q- cluster analysis of trace elements in rocks and ores shows that the correlation coefficient between collophanite and dolomite * * * formation in the same borehole and dolomite * * * formation in ore-free strata far away from rock mass is 90%. It shows that collophanite and dolomite are simultaneously deposited. There are layered colloidal pyrite, anhydrite and a small amount of siderite in the deposit, which is undoubtedly the blank layer of pyrite. For copper ore bodies, it plays an important role as a precipitant or catalyst, promoting the metasomatism and precipitation of copper-bearing hydrothermal solution after magmatic period and forming important copper ore bodies. Carbonate rocks are favorable ore-forming surrounding rocks, and evaporites such as dolomite and anhydrite in this mining area seem to be more favorable than carbonate rocks. The lithologic combination of D3w-C2+3-P 1q is sandstone shale-dolomite (anhydrite)-limestone-shale, and carbonate rocks which are easy to metasomatism are sandwiched in sandstone shale with poor permeability of roof and floor, which is the ore-forming horizon for the formation of ore bodies by selective metasomatism.

2. The controlling effect of magmatic rocks on copper mineralization

Although there is primary collophanite in the deposit, the mineralization is mainly controlled by diorite. In the deep contact zone between Baocun and Qingshanjiao, there are not only C2+3 full-thickness copper mineralization, but also some skarnization and copper mineralization in the upper P 1q limestone and the lower D3w upper sandstone shale. The thickness of the ore body between the rock masses increases, and the grade is the richest. With leaving the rock mass, the thickness and grade decrease. The sulfur isotope δ34S value also shows decreasing zonation, which indicates that magmatic rocks are the carriers of mineral fluids and the main ore-forming controlling factors.

3. Tectonic ore-controlling effect

Tectonic conditions play a very important role in controlling mineralization and local enrichment of ore bodies. Ore bodies are mainly controlled by anticline axis, NE-trending torsional deformation, interlayer detachment surface and EW-trending folds. The bedding detachment structure related to the anticline formation further expanded into ore storage space after the late structural superposition. The three strike planes of the bottom plate D3w and the top plate P 1q are NNE, and the south and north ends of the ore body are uplifted, reflecting the east-west superimposed folds. The axial deflection of the trend surface of P 1q roof is greater than that of D3w floor, indicating that there is differential sliding between the upper strata, and the interlayer detachment surface is compounded by NE-direction torsion, forming a subsidence space favorable for mineralization. The trend contour lines of ore body thickness and grade are about 27 and10, which are basically consistent with the NNE fault zone, indicating that mineralization and enrichment are controlled by the fault zone. Steep fault zone, interlayer detachment structure between D3w and P 1q, and favorable physical and chemical space are important structural control factors for the formation of ore bodies with stable thickness and large extension range.

To sum up, the ore-forming conditions of Dongguashan deposit are that magmatic hydrothermal solution brings copper, C2+3 provides geochemical space, sulfur and a small amount of copper source, and the NNE tectonic stress field is the driving force for the rise of ore liquid. The distribution and enrichment of ore-forming fluids are controlled by the NE-trending torsional deformation and the composite superposition of the detachment surface and the east-west structure of the anticline axis.

(2) Division of metallogenic periods and stages.

The formation of ore bodies in this deposit can be divided into sedimentary diagenetic stage and magmatic hydrothermal stage, with magmatic hydrothermal stage as the main stage, and further divided into four stages: metamorphism, skarnization, oxidation and timely sulfide. There are obvious differences in mineral assemblage and element assemblage in each stage.

Sedimentary diagenetic stage. In the early Middle Carboniferous, it was in the environment of tidal flat depression, and part of the lithofacies changed to deposit collophanite and anhydrite. In the process of sedimentary mineralization, pyrite with spherical and strawberry structure is formed due to the participation of bacteria, which constitutes the basic conditions for mineralization in this area.

Magmatic hydrothermal period. Thermal metamorphic halo is widely developed in this area, and subsequent contact metasomatism and hydrothermal process are superimposed on this basis.

Metamorphic stage: magma intrusion metamorphic surrounding rocks, high rock mass as the main heat source, forming a large-scale metamorphic halo. Thermal gradient depends on the size and shape of rock mass. Argillaceous rocks undergo thermal metamorphism to form hornfels, limestone to form marble, and impure dolomite to form ferromagnesium silicate. Primary collophanite has been transformed, and its fabric is collophanite-fine-coarse, lamellar-banded-massive, and its composition is collophanite-pyrite-pyrrhotite-magnetite.

Sika metallogenic stage: with the cooling and consolidation of magma and the accumulation of gas, liquid and hydrothermal solution, contact metasomatism replaced hydrothermal metamorphism. The hot fluid moves along the fault structure, contact zone and interlayer detachment structure. When the hot fluid metasomatism with calc-magnesia rocks along the interlayer, interlayer skarn can be formed, and magnesium skarn can be formed in the dolomite section at the bottom of Huanglong Formation. Early forsterite and diopside, such as phlogopite, serpentine and talc, were influenced by late hydrothermal solution. With the decrease of temperature and the enhancement of H2O, olivine is transformed into talc and serpentine. Thermal fluid and limestone metasomatism form calc-skarn, which is simple in composition and consists of garnet and diopside. The development degree of layered skarn basically depends on three conditions: high temperature hydrothermal solution containing SiO _ 2 is the necessary source to improve SiO _ 2; Lithology with good porosity and permeability and easy interpretation; Both the upper and lower layers have impermeable layers to limit the lateral flow of hydrothermal solution along the permeable layer and the replacement of surrounding rock.

Oxidation stage: This stage is an environment with high fo2 and low fs2, and the main indicator minerals are magnetite and hydrous silicate minerals. Magnetite can form an independent natural type ore. With the increase of K2O in hydrothermal solution, phlogopite and hydrothermal carbonate minerals, mainly calcite and a small amount of iron calcite or siderite, appear.

Timely sulfide stage: it is the main stage of metallogenic activity, and the ore-bearing hydrothermal solution rises along favorable structural parts. Due to the temperature drop, the addition of sulfur and the mixing of external solutions such as formation water, the complex of ore-forming materials is unstable and precipitated. Under the reduction condition, copper-containing substances are precipitated in minerals such as magnetite and garnet. The mineral crystallization sequence is molybdenite-pyrrhotite-pyrite-chalcopyrite-sphalerite-galena. Among them, pyrrhotite, pyrite and chalcopyrite have multi-periods. Associated alteration minerals mainly include quartz, calcite, chlorite, sericite, serpentine, talc, phlogopite and potash feldspar. Sulfide is disseminated in the interlayer between skarn and anhydrite, and a large number of massive sulfide ores are formed outside skarn. From the outside of the rock mass, pyrrhotite-pyrite has a trend of mutual growth and decline, and chalcopyrite also decreases accordingly; The vertical direction is amphibole (or altered diorite)-talc serpentine-magnetite-massive sulfide (anhydrite)-garnet skarn (anhydrite) from bottom to top. Chalcopyrite mineralization is mainly distributed in talc serpentine to garnet skarn, followed by amphibole or altered diorite.

(3) Sources of ore-forming materials and ore-bearing fluids

According to the geochemical characteristics and stable isotopes of the deposit, the copper ore-forming materials in this area are mainly related to magmatism, and the main basis is as follows:

1. The trace element pedigree Q cluster analysis of chalcopyrite, syenite diorite and regional Huanglong Formation (C2h) dolomite in Dongguashan copper mine shows that chalcopyrite is related to syenite diorite, but not closely related to host country dolomite.

2. The lead isotopic composition of galena in Dongguashan copper deposit is relatively uniform, with 206Pb/204Pb between18.032 ~18.271and 207pb between15.648 ~15.

3. The colloidal pyrite layer deposited at the bottom of C2h in this area contains about 0. 1% copper, and a small amount of chalcopyrite appears. The abundance value of C2h copper is 18μg/g, which is lower than the regional background value.

4. According to the screening results of Cu grade, B representing the origin of magmatic rocks accounts for 90%, and A representing the origin of strata accounts for 10%, that is, 90% of Cu comes from magmatic hydrothermal solution.

As far as the source of ore-bearing fluid is concerned, the hydrogen isotopic composition of mineral fluid inclusions in Dongguashan copper mine during the isochronous sulfide period is-86.3 ‰ ~-94.3% O, δ18 δ DH2O+3.4 ‰ ~+7.6 ‰, which is close to the magmatic water number proposed by Taylor and represents the magmatic hydrothermal range in this area. The hydrogen and oxygen isotopes of colloidal pyrite and galena in the ore are-133.2 ‰ and-139. 1 ‰ respectively, and the-18 of H2O is-17.9 ‰ and-18.6. Therefore, it is considered that magmatic water is the main ore-forming fluid in the early stage and formation water is added in the later stage. The ore-bearing fluid is a mixed circulating fluid mixed with groundwater and magmatic water, and the pH value of the ore-forming solution is 4.9 1 ~ 6.26, which is alkaline in the early stage.

Figure 2- 135 Metallogenic model of Shizishan ore field in Tongling, Anhui Province.

T2d—— East Maanshan Formation; T 1n—— Nanlinghu Formation; T1h-and Longshan formation; T1y-yinkeng formation; P2d—- Dalong Formation; P2L-Longtan Formation; P1g-Gu Feng group; P1q-Qixia formation; C2- Huanglong+Chuanshan Formation; D3w 2—— Upper member of Wu Tong Formation; Silurian system; η δ ο-γ δ-calcium alkaline series; 1- breccia tube; 2— mineralization range of skarn; 3- copper (gold) ore body; 4- molybdenum ore body; 5- silver (gold) ore body; 6- pyrite ore body; 7- veinlet disseminated copper mineralization; 8- copper-bearing timely vein; 9— Metallogenic elements; 10— Magmatic gas and liquid; 1 1- formation water and Tianshui; 12- ore-forming fluid; 13- magma chamber presumption; 14- sedimentary pyrite layer; 15-rich molybdenum deposit; ① Copper, sulfur, iron and gold in Dongguashan; ② copper (gold and sulfur) in Datuanshan; ③ Porphyry copper mineralization

(4) Metallogenic temperature and pressure

The temperature measurement data of inclusions in Dongguashan deposit at each metallogenic stage are as follows:

Skarn stage: the explosive temperature of garnet is 410 ~ 425℃; Oxidation stage: 350 ~ 400℃ for the timely homogenization method, and 300 ~ 365℃ for the explosion temperature of magnetite. The calculated temperature of pyrite-chalcopyrite mineral pair is 20 1 ~ 434℃, and that of pyrrhotite-chalcopyrite mineral pair is 190 ~ 372℃. The above temperature measurement results show that the temperature range is large, which indicates that the mineralization time is long, and the reasonable mineralization temperature in hydrothermal stage is 400 ~ 200℃.

(5) Genetic types of ore deposits

In view of the fact that the mineralization has a certain sedimentary material basis, the mineralization mainly occurs in the hydrothermal sulfide stage after skarnization, especially controlled by horizons, so it is determined that its genetic type is stratabound skarn type.

(vi) Metallogenic model

According to the occurrence horizon, there are Dongguashan, Huashupo, Laoyaling, Datuanshan, Lion Mountain, Houshan Lake Village and Jiguanshi deposits from bottom to top. Although the occurrence horizons of each deposit are different, they are all controlled by unified structure, magmatic rocks and other factors, forming a "multi-in-one" or "multi-layer" ore field model (Figure 2- 135), which is composed of hydrothermal vein type, breccia tube type, stratabound skarn type and skarn type. Dongguashan deposit is a stratabound skarn deposit located in the lower part of the "multi-storey building" model. The metallogenic model of Shizishan ore field has the following main characteristics:

1. Mineralization is mainly controlled by syntectic calc-alkaline intermediate-acid rocks, with small rock branches and surrounding rock branches in the shallow part and large rock masses in the deep part.

2. The structure has obvious zonation in the vertical direction. From deep to shallow, the sequence is interlayer detachment structure-contact zone-breccia tube-fault structure, and different structures correspondingly control different ore body shapes.

3. The ore-forming surrounding rock is mainly C2+3-t1h, and the interface between rocks and strata with different physical and chemical properties is a favorable host bed.

4. The ore bodies are mainly layered-quasi-layered, and copper is the main ore-forming element. There are still differences in element combination among various types of deposits.

5. Minerals are mainly the products of magmatism, and ore-bearing fluid is a mixed ore-forming fluid of magmatic water and groundwater, and the driving force of ore-bearing fluid is mainly the heat source related to magmatic intrusion.

Five, prospecting indicators

(1) Signs of wall rock alteration: Marbling, keratinization and skarnization are developed on the surface. Silicification, potash feldspar, talc and serpentine are important signs of wall rock alteration near the mining area.

(2) Geophysical and geochemical indicators: high gravity (9.5×10-5 ~12×10-5m/S2), medium magnetic force (400 ~ 500 nt), low resistivity, high activation rate and other anomalies, and high concentrations of Cu, Ag and Pb. The longitudinal development degree is much better than that of transverse Cu primary halo, which is a prospecting indicator of stratabound skarn deposit (Dongguashan).

(3) Using the concept of metallogenic series and the metallogenic model of Shizishan ore field to guide prospecting.