Method for deducing depth and thickness of ore body controlled by thrust fault in hydrothermal deposit

Abstract

The invention discloses a method for deducing the depth and thickness of an ore body controlled by a thrust fault in a hydrothermal deposit, and the method comprises the steps: determining the metallogenic structure of the hydrothermal deposit, analyzing and controlling the mechanical property difference of the structure of the ore body in different directions, and judging the difference characteristics of metallogenic space based on the geomechanics theory and method of a mine field; and deducing the ore body extension depth and thickness controlled by the thrust fault. The method can be effectively applied to depth extension and thickness estimation of known ore bodies, positioning prediction of hidden ore bodies and efficient arrangement of prospecting engineering, and serves for mine deep prospecting, storage increasing and production increasing.

Description

Technical Field

[0001] The invention relates to a method for inferring the depth and thickness of an ore body controlled by a thrust fault in a hydrothermal deposit, and belongs to the field of mineral resource exploration. Background Art

[0002] Hydrothermal deposits have typical characteristics such as multiple types of ore-controlling structures, complex ore-controlling mechanisms, variable morphology and occurrence of ore bodies, and uneven scale of ore bodies. Accurately grasping the morphological characteristics, distribution patterns and control mechanisms of hydrothermal deposits or ore bodies controlled by common thrust faults in nature is crucial for locating and predicting hidden ore bodies in the deep and periphery of such deposits and the layout of exploration projects. The kinematic classification of faults in structural geology is relatively broad. Most faults in nature are complex faults, and their relative movement directions are often oblique. Such faults have both horizontal left or right translational movements and vertical compression or tension movements. Therefore, it is difficult to restore the actual movement process of the fault by analyzing the kinematic classification of a single fault, which restricts the location prediction of hidden ore bodies controlled by thrust faults. Summary of the invention

[0003] The present invention provides a method for inferring the depth and thickness of an ore body controlled by a thrust fault in a hydrothermal deposit. The method analyzes the difference characteristics of the mechanical properties of the fracture structures in different directions controlling the ore body, can determine the spatial difference of mineralization, and then infer the depth and thickness of the ore body, and predict deep concealed ore bodies, providing a basis for verifying engineering layout.

[0004] The method for inferring the depth and thickness of the ore body controlled by the thrust fault in the hydrothermal deposit of the present invention is as follows:

[0005] Step 1: Determination of the thrust fault occurrence that controls the distribution of ore bodies

[0006] Applying the theory and methods of mine field geomechanics, through the detailed analysis of the ore-controlling structures in the mining area, we analyze the structural spatial geometry, kinematics, mechanics, material physics, dynamics and other characteristics that control the mineralized alteration zones and ore bodies in the area, determine the ore bodies controlled by the thrust faults, and determine the occurrence of the thrust faults;

[0007] Step 2: Use stress unit to analyze the mathematical relationship between thrust faults and their derived low-order metallogenic structural surfaces and the spatial distribution of ore bodies, and construct a geometric analysis diagram of the metallogenic structural surface ( Figure 1 ),Depend on Figure 1 The derivation formula is as follows:

[0008] The displacement in the long axis direction (P) of the ore body is:

[0009] H P =H C ·cosβ (1)

[0010] HP =H τ ·cosγ·cosβ (2)

[0011] H P = H σ1 ·cos(α+β-γ)·cosγ·cosβ (3)

[0012] The displacement in the true thickness direction (Q) of the ore body is:

[0013] H Q = H C ·sinβ (4)

[0014] H Q = H τ ·cosγ·sinβ (5)

[0015] H Q = H σ1 ·cos(α+β-γ)·cosγ · sinβ (6)

[0016] The displacement of the principal compressive stress σ1 in the true thickness direction (Q) of the ore body (H σ1 ) is:

[0017] H O =H i ·cos(β-γ) (7)

[0018] H O = H σ1 ·sin(α+β-γ)·cos(β-γ) (8)

[0019] In which, it is assumed that the displacement H in the direction of the principal compressive stress σ1 σ1 , all the above are derivations on the cross section;

[0020] H τ :H σ1 the displacement component along the strike of the thrust fault;

[0021] H i :H σ1 the displacement component along the direction perpendicular to the thrust fault;

[0022] H O : Displacement of principal compressive stress σ1 in the true thickness direction (Q) of the ore body (H σ1 ) quantity;

[0023] H C :H τ The displacement component along the low-order metallogenic structural plane (C plane) of the thrust fault;

[0024] HP :H C The displacement component along the long axis of the ore body (P);

[0025] H Q :H C The displacement component along the true thickness direction of the ore body (Q);

[0026] α is the angle between the σ1 direction and the left-hand torsion plane;

[0027] β is the angle between the σ3 direction and the left-hand torsion plane;

[0028] γ is the angle between the thrust fault and its low-order mineralization structural plane (C plane);

[0029] λ is the dip angle of the thrust fault;

[0030] It is known that α and β are fixed values, and γ is a variable; according to actual geological information, it can be known that H i =0,H τ is a fixed value;

[0031] According to formula (2), γ and H P Inversely proportional; the smaller the angle between the thrust fault and its low-order mineralization structural surface (C surface), the greater the displacement component in the long axis direction (P) of the ore body, that is, the deeper the ore body is.

[0032] According to formula (7), H O = 0, the true thickness of the ore body is affected by H Q Control, according to formula (5), γ and H Q It is inversely proportional; it also indicates that the smaller the angle between the thrust fault and its low-order mineralization structural surface (C surface), the greater the displacement component in the true thickness direction (Q) of the ore body, that is, the greater the true thickness of the ore body.

[0033] In geomechanics research, each structural surface of the stress unit has its corresponding definition, such as Figure 2 As shown in d, the AOB surface is a tensile surface, the COD surface is a compressive surface, the AC and BD surfaces are left-hand torsion surfaces, and the AD and BC surfaces are right-hand torsion surfaces ( Figure 2 d). Based on this, when the thrust fault tilts toward SE, the three end members of the left-lateral torsional, compressional, and right-lateral torsional of the low-order mineralization structural surface (C surface) are selected ( Figure 2 a, b, c), analyze the control of various mechanical properties on the depth and true thickness of the ore body; the study believes that the ore body ( Figure 2 e)>the ore body controlled by left-lateral compression-torsion faults ( Figure 2 e)>the ore body controlled by right-lateral compression-torsion faults ( Figure 2e)>the ore body controlled by right-lateral torsional-compression faults ( Figure 2 e). When the thrust fault tilts toward NW, the ore body controlled by right-lateral transpressional fault structure>the ore body controlled by right-lateral transpressional fault>the ore body controlled by left-lateral transpressional fault>the ore body controlled by left-lateral transpressional fault structure surface; the smaller the angle between the thrust fault and the low-order mineralization structural surface (C surface), the greater the extended depth and true thickness of the controlled ore body, and the more favorable it is for mineralization.

[0034] Step 3: Depth estimation of known ore bodies

[0035] Based on the conclusion that the smaller the angle between the low-order mineralization structural surface and the thrust fault, the greater the extended depth and true thickness of the ore body, the ore body group controlled by the same thrust fault is compared to infer the extended depth and thickness of more than one known ore body in the ore body group, and then the prospecting target area is delineated;

[0036] Step 4: Prediction of hidden ore body location

[0037] When a large number of low-order mineralization structural surfaces appear in favorable mineralization areas, and the mechanical properties of the low-order mineralization fault structural surfaces are left-lateral compression-torsion and left-lateral compression-torsion, it indicates the existence of hidden ore bodies in the deep, and then the prospecting target area is delineated;

[0038] When the thrust fault tilts toward the NW, a large number of low-order mineralization structural surfaces appear in the favorable mineralization area, and the mechanical properties of the low-order mineralization fault surface are right-lateral compression and torsional and right-lateral compression and torsional, which indicates the existence of hidden ore bodies in the deep, and then the prospecting target area is delineated;

[0039] Step 5: Exploration Project Layout

[0040] For thrust faults with different dip angles, the relationship between the dip angle of the thrust fault, the mechanical properties of the low-order mineralization structural surface (C surface) and the dip angle of the ore body extension direction on the profile is analyzed ( Figure 4 );

[0041] In order to facilitate calculation, it is assumed that the dip angle is 0° as the starting point. The thrust fault rotates counterclockwise when it is NW-dipping and clockwise when it is SE-dipping ( Figure 5 );f (x)da is the inclination of the thrust fault, θ is the inclination of the ore body; f (x)da ∈[0,90°],θ∈[-45°,135°].

[0042] Therefore, if the occurrence of the thrust faults controlling the ore body group is known, combined with the mechanical properties of the low-order mineralization structural surface (C surface), the inclination angle θ of the ore body extension can be reduced to within 22.5°.

[0043] The relationship between the mechanical properties of the low-order mineralization structural surface (C surface) and the inclination angle of the ore body is as follows:

[0044] (1) When the mechanical properties of the low-order mineralization structural surface are left-hand torsional:

[0045] The inclination angle of the ore body is θ = f (x)da -45°;

[0046] (2) When the mechanical properties of the low-order mineralization structural surface are left-lateral torsion and compression:

[0047] The inclination angle of the ore body is θ = [f (x)da ,f (x)da +22.5°]-45°;

[0048] (3) When the mechanical properties of the low-order mineralization structural surface are left-lateral compression and torsion:

[0049] The inclination angle of the ore body is θ = [f (x)da +22.5°,f (x)da +45°]-45°;

[0050] (4) When the mechanical properties of the low-order mineralization structural surface are compressive:

[0051] The inclination angle of the ore body is θ = f (x)da +45°-45°;

[0052] (5) When the mechanical properties of the low-order mineralization structural surface are right-lateral compression and torsion:

[0053] The inclination angle of the ore body is θ = [f (x)da +45°,f (x)da +90°-22.5°]-45°;

[0054] (6) When the mechanical properties of the low-order mineralization structural surface are right-lateral torsion and compression:

[0055] The inclination angle of the ore body is θ = [f (x)da +90°-22.5,f (x)da +90°]-45°;

[0056] (7) When the mechanical properties of the low-order mineralization structural surface are right-lateral torsional:

[0057] The inclination angle of the ore body is θ = f (x)da +90°-45°.

[0058] Advantages and technical effects of the present invention:

[0059] (1) Applicable to deep positioning, prospecting and prediction of hydrothermal deposits of copper, lead, zinc, gold, antimony, silver and other minerals controlled by thrust faults;

[0060] (2) It can quickly infer the depth and thickness of known ore bodies, guide the efficient layout of deep prospecting projects, and significantly reduce the costs of analytical testing, geophysical and geochemical surveying, and prospecting and exploration;

[0061] (3) It can locate and predict the location of hidden ore bodies controlled by thrust faults;

[0062] (4) The method is relatively simple and easy to apply, which can significantly shorten the deep prospecting and exploration period and reduce its cost;

[0063] (5) It can significantly reduce the influence of multi-factor interference and multi-solution of geophysical or geochemical anomalies, and can guide the interpretation of geophysical and geochemical anomalies;

[0064] (6) This method is applicable to scales of 1:1000 to 1:10000. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Schematic diagram of the geometric analysis of the control of thrust faults and their low-order mineralization structural structures on the ore body.

[0066] Figure 2 It is the theoretical end-member distribution diagram of the inclination angle of the thrust fault and its low-order mineralization structural surface; 1 is the thrust fault, 2 is the low-order mineralization structural surface derived from the thrust fault, and 3 is the ore body or concealed ore body (a is left-lateral torsional, b is compressive, c is right-lateral torsional, d is stress unit body, and e is the distribution range of mechanical properties).

[0067] Figure 3 This is the actual cross-section of the I-6 and I-8 ore bodies in a lead-zinc deposit in northeastern Yunnan; 1 is the stratigraphic code, 2 is the conformity contact relationship, 3 is the parallel unconformity contact relationship, 4 is the fault, 5 is the known ore body, 6 is the predicted ore body, 7 is the ideal model of the ore body shape, and 8 is the elevation.

[0068] Figure 4 It is a relationship diagram between local principal compressive stress, interlaminar fault zone and its lower-order compressive surface at special angles.

[0069] Figure 5 Schematic diagram of calculation of SE and NW tilt angles of interlayer fractures;

[0070] Figure 6 It is the extension speculation of known ore bodies and the layout of prospecting projects; 1 is a massive lead-zinc ore body, 2 is a massive pyrite body, 3 is a calcite vein, 4 is a sphalerite vein, 5 is a galena vein, 6 is a dolomite vein, 7 is a stratigraphic pattern, 8 is a fault, 9 is an ore body boundary, 10 is a mineralized alteration zone, 11 is a known ore body, 12 is an interlayer fault zone, 13 is a low-order fault, 14 is a predicted ore body, and 15 is a suggestion for the layout of prospecting projects;

[0071] Figure 7It is a prospecting prediction for concealed ore bodies and a layout diagram for prospecting projects. DETAILED DESCRIPTION

[0072] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the contents described above, and the methods in the examples are conventional methods unless otherwise specified;

[0073] Example 1: Extension and depth inference of deep ore bodies in a hydrothermal germanium-rich lead-zinc deposit in Sichuan, Yunnan and Guizhou

[0074] 1. Determination of the occurrence of thrust faults that control the distribution of ore bodies

[0075] By applying the theory and methods of mining field geomechanics and making a detailed analysis of the ore-controlling structures in the mining area, we analyze the spatial geometry, kinematics, mechanics, material physics, chronology, and dynamics of the fault structures that control the mineralized alteration zones in the mining area, determine the ore bodies controlled by the thrust faults, and determine the occurrence of the thrust faults.

[0076] In the middle and late Indosinian period and the early Yanshan period, due to the action of the NW-SE regional tectonic stress field, the NE-trending MP left-lateral oblique strike-slip fault and its NE-trending MMS compound inversion anticline and the SN-trending left-lateral torsional LZH fault were formed in the mining area, forming a typical oblique strike-slip-fault-fold structural belt, which jointly controlled the formation of the MP germanium-rich lead-zinc deposit. During the large-scale migration and "penetration" of deep mineralization hydrothermal fluids along the oblique strike-slip fault-fold belt to the shallow part, the Pb, Zn and other mineralization elements in the basement were continuously leached and extracted, forming a Pb-rich ore deposit. 2+ 、Zn 2+ The continuously concentrated and enriched deep-source fluid "penetrates" along the ore-conducting structure MP fault, passes through the SN left-trending torsional LZH fault, the NNW left-trending torsional-tensional fault, and the NE left-trending compressive-torsional cutting fault, and enters the NE left-trending compressive interlayer fault zone in the carbonate rock of the ore-bearing strata (Zaige Formation, Baizuo Formation and Weining Formation). Because the ore-forming fluid is blocked by the clastic rock barrier layer, it mixes with the reducing basin fluid in the carbonate rock under the barrier layer, and sulfide precipitation occurs to form mineralization, forming a set of structural-mineralization alteration combination zoning and a group of ore bodies with different ore types dominated by lead and zinc.

[0077] The ore bodies (groups) of this deposit are controlled by interlayer fault zones with NE-oriented left-directed compression. The interlayer fault zones with compression can be regarded as thrust faults in the profile. The I-6 and I-8 ore bodies are the largest ore bodies that have been discovered so far in this deposit. They belong to the I ore body group of the Hedong mining section and are located on the NW wing D3zg of the MMS compound inverted anticline. 3-2 It is distributed obliquely in the interlayer fault zone in carbonate rocks.

[0078] According to formula (2), γ and H PInversely proportional; the smaller the angle between the interlayer fault zone and its lower-order compression / torsion-compression surface C that controls the ore body, the greater the displacement component in the direction of the long axis P of the ore body, that is, the deeper the ore body extends. Combined with the theory of geomechanics, it can be known that when the low-order mineralization structural surface (C surface) is a compression-compression surface, the depth of the ore body controlled is greater than that of the ore body controlled by the compression-torsion surface, that is, the depth of the I-8 ore body is greater than that of the I-6 ore body.

[0079] According to formula (7), H O = 0, the true thickness of the ore body is affected by H Q Control, according to formula (5), γ and H Q Inversely proportional; similarly, the smaller the angle between the interlayer fault zone and its low-order mineralization structural surface (C surface), the greater the displacement component of the true thickness of the ore body in the Q direction, that is, the greater the true thickness of the ore body; combined with the theory of geomechanics, it can be known that when the low-order mineralization structural surface (C surface) is a torsional-compressive surface, the true thickness of the ore body controlled is greater than that of the ore body controlled when it is a compressive-torsional surface; that is, the true thickness of the I-8 ore body is greater than that of the I-6 ore body.

[0080] The smaller the angle between the thrust fault and the low-order mineralization structural plane (C plane), the greater the depth and true thickness of the controlled ore body. The displacement component in the direction of the long axis P of the ore body is significantly greater than that in the direction of the true thickness Q of the ore body, and the former is controlled by the torsional compression surface, while the latter is controlled by the torsional tension surface; when the ore-forming fluid enters the open space, the fluid and the surrounding rock undergo thermal dissolution, and the compression effect is obviously more conducive to the thermal dissolution than the tension effect. Although the σ1 displacement component in the direction of the true thickness Q of the ore body has not actually displaced, the potential energy of its force and the displacement component in the direction of the true thickness Q of the ore body jointly drive the occurrence of thermal dissolution between the ore-forming fluid and the surrounding rock in the direction of the true thickness Q, resulting in the difference in mineralization space between the I-8 ore body and the I-6 ore body in the depth and true thickness directions.

[0081] 2. Depth inference of known ore bodies and layout of prospecting projects

[0082] The smaller the angle between the low-order mineralization structural surface (C surface) and the interlayer fault, the greater the depth and true thickness of the ore body, and the more favorable it is for mineralization ( Figure 3 ). According to the rules of structural control of ore, the I-6 ore body is mainly controlled by the left-running compression-torsion surface, and the I-8 ore body is mainly controlled by the left-running compression-torsion surface. Because they are controlled by the same interlayer fault zone, the relative fault distances are consistent. Therefore, the vertical opening space of the I-8 ore body is larger than that of the I-6 ore body. It is inferred that the vertical extension of the I-8 ore body is greater than that of the I-6 ore body. The deep part of the I-8 ore body extends to at least 150m elevation, and the ore body below the 250m elevation reverses to the NW and extends to the depth with a pinch-out trend ( Figure 3 ).

[0083] from Figure 6It can be seen that the dip angle of the interlayer fault zone is 80°. According to the detailed analysis of the mineralization structure, the low-order fault in the 430m middle section of the I-8 ore body is NE35°∠80°SE, and the fault is a left-lateral torsional fault.

[0084] For low-order mineralization structural surface (C surface), it is left-hand torsional: the inclination angle of the ore body extending deeper is θ = f (x)da -45°=80°-45°=35°, because the interlayer fault zone is SE-inclined ( Figure 5 ), which is consistent with the actual dip angle of the I-8 ore body;

[0085] Therefore, the parameters of the drilling project ZK-01 are as follows: azimuth 310°, inclination 70°, designed hole depth 400m ( Figure 6 ); After engineering verification, a concealed ore body was discovered deep in the I-8 ore body.

[0086] 3. Concealed ore body positioning and prospecting project layout

[0087] from Figure 7 It can be seen that the dip angle of the interlayer fault zone is 45°. According to the detailed analysis of the mineralization structure, the low-order fault is left-lateral torsional ( Figure 7 );

[0088] For low-order mineralization structural plane (C plane) when it is left-lateral torsional-compressive:

[0089] The inclination angle of the ore body is θ = [f (x)da ,f (x)da +22.5°]-45°=[45°,45°+22.5°]=[0°,22.5°];

[0090] Therefore, the predicted distribution range of the inclination angle of the concealed ore body is between 0° and 22.5°; Figure 5 ), so the parameters of the prospecting project DBDZK-5# are as follows: azimuth 330°, inclination 85°, designed hole depth 650m ( Figure 7 ); after engineering verification, a deep hidden ore body was discovered.

Claims

1. A method for inferring the depth and thickness of an ore body controlled by a thrust fault in a hydrothermal deposit, characterized in that: Here are the steps: (1) Applying the theory and methods of ore-field geomechanics, through detailed analysis of the ore-controlling structures in the mining area, analyze the spatial geometry, kinematics, mechanics, material physics, dynamics and other characteristics of the ore-forming structures that control the mineralized alteration zones and ore bodies in the mining area, determine the distribution characteristics of the ore bodies controlled by the thrust faults, and determine the occurrence of the thrust faults; (2) The stress unit is used to analyze the mathematical relationship between the thrust fault and its low-order metallogenic structural surface and the spatial distribution of the ore body. The control characteristics of the mechanical properties of the low-order metallogenic structural surface on the extended depth and true thickness of the ore body are as follows: When the thrust fault is inclined to SE, for the low-order mineralization structural surface, the ore body controlled by the left-line transpressional fault structure is > the ore body controlled by the left-line transpressional fault > the ore body controlled by the right-line transpressional fault > the ore body controlled by the right-line transpressional fault; when the thrust fault is inclined to NW, for the low-order mineralization structural surface, the ore body controlled by the right-line transpressional fault structure is > the ore body controlled by the right-line transpressional fault > the ore body controlled by the left-line transpressional fault > the ore body on the left-line transpressional fault structural surface; moreover, the smaller the angle between the low-order mineralization structural surface and the thrust fault, the greater the extended depth and true thickness of the controlled ore body, and the more favorable it is for mineralization; (3) Inference of deep extension depth and thickness of known ore bodies The smaller the angle between the low-order mineralization structural surface and the thrust fault, the greater the extended depth and true thickness of the controlled ore body; by comparing the ore body groups controlled by the same thrust fault, the extended depth and thickness of more than one known ore body in the ore body group can be inferred, and then the deep prospecting target area can be delineated; (4) Prediction of concealed ore bodies When the thrust fault tilts toward SE, a large number of low-order mineralization structural surfaces appear in favorable mineralization areas, and the mechanical properties of the low-order mineralization fault surface are left-lateral compression and torsional and left-lateral compression and torsional, which indicates the existence of hidden ore bodies in the deep, and thus the prospecting target area is delineated; When the thrust fault tilts toward the NW, a large number of low-order mineralization structural surfaces appear in the favorable mineralization area, and the mechanical properties of the low-order mineralization fault surface are right-lateral compression and torsional and right-lateral compression and torsional, which indicates the existence of hidden ore bodies in the deep, and then the prospecting target area is delineated; (5) Layout of prospecting projects According to the mechanical properties of the low-order mineralization structural surface and the inclination of the thrust fault, the inclination of the ore body is determined, and then the prospecting project is arranged; ① When the mechanical properties of the low-order mineralization structural surface are left-hand torsional: The inclination angle of the ore body is θ = f (x)da -45°; ② When the mechanical properties of the low-order mineralization structural plane are left-lateral torsion and compression: The inclination angle of the ore body is θ = [f (x)da ,f (x)da +22.5°]-45°; ③ When the mechanical properties of the low-order mineralization structural surface are left-lateral compression and torsion: The inclination angle of the ore body is θ = [f (x)da +22.5°,f (x)da +45°]-45°; ④ When the mechanical properties of the low-order mineralization structural surface are compressive: The inclination angle of the ore body is θ = f (x)da +45°-45°; ⑤ When the mechanical properties of the low-order mineralization structural surface are right-lateral compression and torsion: the inclination angle of the ore body θ = [f (x)da +45°,f (x)da +90°-22.5°]-45°; ⑥ When the mechanical properties of the low-order mineralization structural surface are right-lateral torsion and compression: the inclination angle of the ore body θ = [f (x)da +90°-22.5,f (x)da +90°]-45°; ⑦ When the mechanical properties of the low-order mineralization structural surface are right-lateral torsional: the inclination angle of the ore body extending deeper θ = f (x)da +90°-45°; where f (x)da is the dip angle of the thrust fault.

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