Prospecting method of Zijinshan copper-gold deposit based on surface geology and rock physical properties

Abstract

The present invention discloses a prospecting method for the Zijinshan copper-gold deposit based on surface geology and rock properties, which relates to the technical field of prospecting methods and includes the following steps: Step 1: Obtain the spatial position of underground magnetic rock bodies through magnetic field observation and inversion according to the prospecting target; Step 2: Find the old strata and magnetic rock bodies or hidden rock bodies on the surface; Step 3: Infer the maximum mineralization depth through drilling rock physical property testing; Step 4: Predict the mineralization range based on geochemical anomalies, comprehensive geophysical anomalies, and geological anomalies; Step 5: Drill verification and modify the prospecting range; Step 6: Summarize the hydrothermal magma diagenesis and mineralization model. The present invention adopts the above-mentioned prospecting method for the Zijinshan copper-gold deposit based on surface geology and rock properties, identifies the intense alteration zone through core physical property observation, and then determines the location of the ore body by combining geology and other geophysical and geochemical methods; The magnetic susceptibility of the rock in the depth direction reveals the diagenesis and mineralization environment; The magnetic susceptibility of the aeromagnetic three-dimensional inversion infers several hidden igneous rock bodies.

Description

Technical Field

[0001] The present invention relates to the technical field of prospecting methods, and in particular to a prospecting method for the Zijinshan copper-gold mine based on surface geology and rock physical properties. Background Art

[0002] The early detection methods of Zijinshan gold and copper mineral resources were mainly based on surface surveys and drilling "trial and error method", from the surface to the underground, from the known to the unknown. However, as the mining depth increased, the cost of drilling prospecting using the "trial and error method" increased sharply, and exploring new methods and technologies became the only option to improve quality and efficiency.

[0003] In recent years, the integration of near-infrared spectroscopy (NIR) scanning technology with geochemical primary halo models has enabled the prediction of deep mineralization. Large-scale mineral exploration in the Zijinshan area also utilizes remote sensing to identify alteration zones. This approach falls into two main categories: one uses remote sensing imagery to interpret various structures related to mineralization and ore-control; the other uses multispectral remote sensing data to extract information about alteration anomalies. However, spectral techniques are limited to the surface of rocks and minerals and cannot predict the properties of underlying rocks and minerals. Geophysical exploration, on the other hand, leverages the deep penetration of physical fields into rocks and minerals to identify geological anomalies related to mineralization, such as igneous bodies, faults, lithologic interfaces, and uplift structures. Geologists have conducted extensive geophysical research using deep-depth methods such as gravity, aeromagnetic, artificial seismic, and magnetotelluric sounding to delineate deep faults and tectonic units in the Zijinshan area, providing new insights. Based on magnetic, electrical, geochemical, and regional gravity data, a geological, geophysical, and geochemical model of the ore field has been established. The model suggests that gravity and magnetic anomalies along this belt reflect the distribution of granodiorite, and that its inner and outer contact zones represent favorable locations for prospecting. For older mining areas, the most valuable resource is the thousands of drill cores, valuable physical materials from depths of 1,000-2,000 meters underground. These cores contain a wealth of geological information, and their value must be fully utilized and exploited. For example, core physical properties, chemical composition, and mineralization age are crucial for studying mineral formation, as these rock characteristics cannot be obtained using any surface exploration methods. Summary of the Invention

[0004] The purpose of the present invention is to provide a prospecting method for the Zijinshan copper-gold deposit based on surface geology and rock physical properties, to search for strongly altered rock masses with physical properties such as high polarizability, low magnetic susceptibility and relatively high density located between old strata and magnetic rock masses, and to provide favorable target areas for prospecting.

[0005] To achieve the above objectives, the present invention provides a method for prospecting the Zijinshan copper-gold deposit based on surface geology and rock physical properties, comprising the following steps:

[0006] Step 1: Conduct aeromagnetic or ground-based geomagnetic field observations in the target area and perform three-dimensional inversion of residual magnetic anomalies to obtain the spatial position of the magnetic susceptibility of igneous rocks closely related to mineralization, that is, the range of magnetic susceptibility in plane and at depth;

[0007] Step 2: Generally, metal mineralization is associated with ancient strata and enters the shallow surface through uplift. Therefore, finding the exposed area of the old strata is a key step. Another key step is to find the exposed or concealed igneous rock area.

[0008] Step 3: Conduct rock physical property testing, paying particular attention to the physical properties of the drill core, including magnetic susceptibility, polarizability, density, and resistivity. Based on the combination of physical properties, the temperature of the rock-forming and mineralization environment can be inferred, the interface between the strongly altered medium- and low-temperature hydrothermal mineralization environment and the high-temperature magma can be identified, and the deepest mineralization depth can be inferred.

[0009] Step 4: Combine geochemical anomalies and comprehensive geophysical anomalies to narrow the prospecting target area;

[0010] Step 5: Drilling verification: Based on the chemical analysis of the mineral content of the drill core, the prospecting range is revised;

[0011] Step 6: Summarize the mineralization model.

[0012] Preferably, in step 1, magnetic rock bodies (magnetic granite) are searched by aeromagnetic or ground-based geomagnetic observation methods. The magnetic rock bodies can be inferred to be high-temperature magma systems, accompanied by medium- and low-temperature magmatic hydrothermal systems (non-magnetic granite). In the medium- and low-temperature magma systems or on the contact zone, strong alteration often occurs, forming enriched metal ores.

[0013] Preferably, the old strata in step 2 include Proterozoic (Sinian Period, etc.), Paleozoic (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian), and Mesozoic (Triassic, Jurassic, Cretaceous). These old strata indicate that the region has experienced earth uplift.

[0014] Preferably, the purpose of the drill core physical properties tested in step 3 is to infer the igneous rock diagenesis and mineralization environment, medium and low temperature environment (or alteration mineralization environment): low magnetic susceptibility 0-1000SI*10 -6 , high polarization rate 5-30%, high density 2.7-3.5g / cm 3 , low resistivity 10-2000Ω·m; high temperature environment physical property combination is: high magnetic susceptibility 1000-n*10000SI*10 -6 , low polarization rate 0-5%, stable density 2.5-2.7g / cm 3 , higher resistivity 1000-n*10000Ω·m.

[0015] Preferably, in step 4, geochemical anomalies and comprehensive geophysical anomalies are combined to narrow the prospecting target area.

[0016] Preferably, in step five, the drilling verification is performed, and a comprehensive assessment is made based on the mineralization rate of the core analysis to revise the prediction range.

[0017] Therefore, the present invention adopts the above-mentioned Zijinshan copper-gold prospecting method based on surface geology and rock physical properties. The core of the present invention is to propose a new prospecting method and a new mineralization model, that is, the magnetic rock body left by high-temperature magma activity is obtained through magnetic field observation, the strong alteration zone is identified through core physical property observation, and the location of the ore body is determined by combining geology and other physical and chemical exploration methods; the mineralization model points out that the metal materials and sulfides in the lower crust or upper mantle are brought to the shallow surface by hot steam and liquid for alteration and enrichment, and after rock formation and mineralization, they are pushed to a higher position by the bottom magma activity or the crust to accept geological effects such as weathering and erosion; the magnetic susceptibility of the rock in the depth direction reveals the rock formation and mineralization environment; the rock polarization rate in the depth direction reveals that there is a strong induced polarization effect above the elevation of the site, indicating that the rock alteration and mineralization are intense; the horizontal slices of the magnetic susceptibility of the aeromagnetic three-dimensional inversion reveal the hidden magnetic rock bodies at an altitude of -600m: Shicao rock body, Luoboling rock body, Ximei rock body, Chishui rock body and Xinwuxia rock body, all of which are significant prospecting signs.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the prospecting flow chart of the present invention;

[0020] Figure 2 The horizontal slice characteristics of the magnetic susceptibility at an elevation of -600m of the three-dimensional aeromagnetic anomaly inversion result of the present invention;

[0021] Figure 3 The magnetic susceptibility versus elevation curve of the drill core of the present invention;

[0022] Figure 4 The curve showing the change of polarizability of the drilled core with elevation of the present invention;

[0023] Figure 5 This is the rock-forming and mineralization model of the Zijinshan mining area of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0025] Unless otherwise defined, the technical or scientific terms used in the present invention shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0026] Example

[0027] See also Figure 1-5 The present invention provides a method for prospecting the Zijinshan copper-gold deposit based on surface geology and rock physical properties, comprising the following steps:

[0028] Step 1: Based on the prospecting target, conduct aeromagnetic or ground magnetic field observations and perform three-dimensional inversion to convert magnetic anomalies into rock magnetic susceptibility parameters. This method is low-cost and highly efficient and can identify magnetic rock bodies left behind by magmatic activity. Generally, various metal minerals are formed around the alteration of the magma system.

[0029] Step 2: Older strata exposed at the surface reflect uplift of the crust or mantle (magma intrusion) in the region. Overlying strata are weathered and eroded, exposing older strata to the surface. Mineral deposits formed over hundreds of millions of years are subsequently pushed to the surface. Older strata include those from the Proterozoic (Sinian Period, etc.), the Paleozoic (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian), and the Mesozoic (Triassic, Jurassic, Cretaceous).

[0030] Step 3: Testing rock properties is the basic work of geophysical prospecting. Generally, only the physical properties of rocks and minerals exposed on the surface are collected and tested. The present invention specifically refers to the multi-property measurement of drill cores, that is, the magnetic susceptibility, polarizability, density and resistivity of all drill cores are tested. Its purpose is twofold: one is to find the strongly altered section and directly prospect for minerals, with the main parameter being polarizability; the other is to determine the maximum depth of mineralization, that is, to find the interface between low magnetic susceptibility and high magnetic susceptibility, which is the interface between medium-low temperature and high-temperature magma.

[0031] Step 4: Finding a strongly altered section does not guarantee that it is the target mineral species, so chemical analysis is required. At the same time, it must be combined with other geological and geophysical data to finally determine and narrow the prospecting target area.

[0032] Step 5: Drilling verification. Based on the chemical analysis of the mineral content of the drill core, the prospecting range is revised. The approximate prospecting target area is determined through step 4. The core is taken out through drilling and the chemical composition of the rock is analyzed. It is possible that some places in the target area have industrial-grade ores, while some places only have mineralization and no ores with industrial mining value.

[0033] Step 6. The mineralization model is to understand the activity process of the entire magmatic hydrothermal system from the perspective of geological time. It must conform to the general logic of magmatic activity and be consistent with the rock physical property data that has been obtained. The deduction of the rock-forming and mineralization process can provide a reference for expanding the scope of prospecting.

[0034] First, the understanding of the mineralization model was changed. The Zijinshan mining area is now considered part of a large-scale, rift-like, low-temperature hydrothermal volcanic swarm mineralization system. Mineralization occurred within granite bodies, and later in the process of formation, volcanic activity or crustal movement pushed the rocks to a high surface. The mineralization area and thickness are enormous, with a mineralization thickness of approximately 1,600 meters. Significant prospecting indicators are presented: ① On the horizontal plane, with the Zijinshan mining area as the center, aeromagnetic methods were used to determine the distribution of magnetic rock bodies. Granites between magnetic rock bodies and older strata (Sinian, Devonian, or Cretaceous) were identified as potential mineralization areas. ② In depth, from the surface downward, when potash (reddened) granite, biotite granite, or increased magnetic properties of the rock body appear, it is considered that the boundary of the non-mineralization zone has been reached and excavation should be stopped. ③ Rock polarizability, density, and magnetic susceptibility were tested. A combination of high polarizability, relatively high density, and low magnetic susceptibility indicates strong mineralization and potential for metal deposits such as gold, copper, silver, and molybdenum.

[0035] Figure 2 The results of three-dimensional aeromagnetic anomaly inversion show the horizontal slice characteristics of magnetic susceptibility at an elevation of -600m, indicating several hidden high-magnetic rock bodies: Shicao rock body, Luoboling rock body, Jingmei rock body, Chishui rock body and Xinwuxia rock body.

[0036] Figure 3 The magnetic susceptibility curves of five typical boreholes are shown. Four of them have a very obvious high magnetic susceptibility interface. The area above this interface is low magnetic susceptibility (0-1000SI×10 -6The medium-to-fine-grained granite ranges from an elevation of approximately 200 meters in the northeast to -873 meters in the southwest. Rock magnetism generally originates from remanent magnetism generated by the Earth's magnetic field when high-temperature magma cools below the Curie temperature (approximately 480-580°C). This remanent magnetism, known in geology as "magnetic fossils," remains unchanged for a long time. This suggests that low and high magnetic susceptibility values reveal the temperature and mineralization environment of rocks and ores. Medium-to-low temperatures are suitable for hydrothermal alteration of copper and gold (high sulfur is a chemical indicator), resulting in weak or no magnetism. High temperatures in the parent magma generate remanent magnetism in the rock as it cools. This also suggests that the underlying interface for mineralization in the Zijinshan area is granites with high magnetic susceptibility (such as potassium feldspar granite, porphyritic granodiorite, monzogranite, and biotite granite).

[0037] Figure 4 The polarizability parameter characterizes the pure induced polarization effect (i.e., charge-discharge effect) of rocks and minerals. This induced polarization effect is stronger when the rocks and minerals are severely altered and the metal content increases. Judging from the borehole polarizability parameters below, with the exception of ZK2404, which has a relatively low polarizability value, the other four boreholes all exhibit high polarizability anomalies, ranging from approximately 5% to 25%. ZK2404 is located north of the Jingmei rock mass and directly south of DZK106, meaning that the polarizability anomaly becomes shallower and weaker towards the south. Future prospecting directions are north and northwest of DZK106. It can also be seen that the polarizability anomaly in ZK2417 has not bottomed out, indicating continued downward excavation.

[0038] Figure 5 The Zijinshan mining area's rock-forming and mineralization model is presented. It consists of a rift-like, low-temperature hydrothermal volcanic cluster, which, after millions of years of continuous alteration and mineralization, has formed an area covering tens of square kilometers. The deepest mineralization area reaches -800 meters above sea level, and the thickness of intense mineralization is approximately 1,600 meters. Aeromagnetic methods are used to determine the distribution of magnetic rock bodies, centered on the Zijinshan mining area. Granites between magnetic rock bodies and older strata (Sinian, Devonian, or Cretaceous) are considered to have mineralization potential. Vertically, from the surface downward, when potash (reddened) granite, biotite granite, or a rock mass with increased magnetic properties appears, it is considered that the boundary of the non-mineralized area has been reached, and excavation is stopped.

[0039] Therefore, the present invention adopts the above-mentioned structure of the Zijinshan copper-gold prospecting method based on surface geology and rock physical properties. The core of the present invention is to propose a new prospecting method and a new mineralization model, that is, the magnetic rock body left by high-temperature magma activity is obtained through magnetic field observation, the strong alteration zone is identified through core physical property observation, and the location of the ore body is determined by combining geology and other physical and chemical exploration methods; the mineralization model points out that the metal materials and sulfides in the lower crust or upper mantle are brought to the shallow surface by hot steam and liquid for alteration and enrichment, and after rock formation and mineralization, they are pushed to a higher position by the bottom magma activity or the crust to accept geological effects such as weathering and erosion; the magnetic susceptibility of the rock in the depth direction reveals the rock formation and mineralization environment; the rock polarization rate in the depth direction reveals that there is a strong induced polarization effect above the elevation of the site, indicating that the rock alteration and mineralization are intense; the concealed igneous rock bodies revealed by the horizontal slices of the magnetic susceptibility of the aeromagnetic three-dimensional inversion: Shicao rock body, Luoboling rock body, Ximei rock body, Chishui rock body and Xinwuxia rock body are all significant prospecting signs.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. The Zijinshan copper-gold prospecting method based on surface geology and rock physical properties is characterized by: The following steps are involved: Step 1: Based on the prospecting target, conduct aeromagnetic or ground geomagnetic field observations in the target area and perform three-dimensional inversion of the residual magnetic anomaly to obtain the spatial position of the magnetic susceptibility of igneous rocks that is closely related to mineralization; Step 2: Find an area that meets the surface geological conditions. There must be exposed Proterozoic, Paleozoic, or Mesozoic strata, as well as exposed or concealed igneous rock bodies. Step 3: Conduct rock physical property testing, focusing on the physical properties of the drill core, including magnetic susceptibility, polarizability, density, and resistivity, and infer the temperature of the rock-forming and mineralization environment based on the combination of physical properties; Step 4: Combine geochemical anomalies and comprehensive geophysical anomalies to narrow the prospecting target area; Step 5: Drilling verification: Based on the chemical analysis of the mineral content of the drill core, the prospecting range is revised; Step 6: Summarize the mineralization model. The mineralization model is to understand the activity process of the entire magmatic hydrothermal system from the perspective of geological time. It should be consistent with the general logic of magmatic activity and the obtained rock physical property data, and deduce the rock-forming and mineralization process to provide a reference for expanding the scope of prospecting. The rock magnetic susceptibility in the three-dimensional underground space obtained after the large-area magnetic field observation and three-dimensional inversion in step 1; In step 3, the drill core was tested to infer the igneous rock formation and mineralization environment. The physical property combination of the medium and low temperature environment is: low magnetic susceptibility , high polarization rate 5~30%, higher density , lower resistivity ; High temperature environment physical property combination: high magnetic susceptibility , low polarization rate 0~5%, stable density , higher resistivity ; In step 4, based on comprehensive geophysical anomalies, geochemical methods are used to analyze the metal content in rocks and ores and narrow down the mineralization target area.

2. The Zijinshan copper-gold prospecting method based on surface geology and rock physical properties according to claim 1 is characterized in that: In step five, drilling verification is carried out and the prospecting target area is modified according to the ore grade.

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