Rutile-based porphyry type copper ore hydrothermal evolution and mineralization prediction method

Abstract

The invention relates to a rutile-based porphyry type copper ore hydrothermal evolution and mineralization prediction method. The method comprises the following steps: marking the position of rutile in a rock mass sample; dividing the rock mass sample at the same position into two parts, preparing one part of the rock mass sample into a probe piece, delineating the position of rutile in the probe piece, and determining the enrichment degree, occurrence state, color and particle size of the rutile in different alteration zones according to the crystal form and internal structure characteristics of the rutile; performing rutile backscatter photography and energy spectrum analysis to obtain the variation trend of the inclusion mineral content of the rutile in different alteration zones; performing in-situ micro-area element analysis on the other part of rutile to obtain content data of main trace elements in the rutile; and based on the position of the rutile alteration zone, the hydrothermal center is determined, and then the mineralization potential is determined. According to the method, the efficiency and accuracy of prospecting from the porphyry type copper ore bed are improved, and the problems that prospecting of the deep edge of the ore bed is large in difficulty, long in period and low in efficiency are solved.

Description

Technical Field

[0001] This invention relates to the field of mineral resource exploration technology, and in particular to a method for predicting the hydrothermal evolution and mineralization of porphyry copper deposits based on rutile. Background Technology

[0002] Porphyry copper deposits are one of the world's most important copper resource types, contributing over 80% of copper and molybdenum resources. The formation of porphyry copper deposits involves complex magmatic-hydrothermal processes and the evolution of ore-forming fluids; therefore, accurately identifying their hydrothermal evolution and assessing their mineralization potential is a crucial objective of geological exploration. During the mineralization process of porphyry copper deposits, specific alteration mineral assemblages with significant spatial differentiation form outward from the metal-rich hydrothermal center; this phenomenon is known as alteration zoning. From the center of the porphyry copper body outward, alteration zones develop sequentially: potassic alteration → sericitization → argillaceous alteration → propylitic alteration. These alteration zones and mineralization zoning exhibit spatial correspondence. The type and zoning of alteration zones can help determine the mineralization potential of different areas; generally, ore bodies are mostly hosted in the transition zone between potassic and sericitized zones. This zoning not only reflects the dynamic evolution of ore-forming fluids but is also a core basis for predicting the location of ore bodies.

[0003] Currently, there are two main methods for predicting the hydrothermal evolution process and mineralization potential of porphyry copper deposits:

[0004] (1) Geological methods: Relying on professional personnel to conduct petrographic analysis, rock specimens are observed visually in the field to observe the mineral formation sequence and their mutual substitution relationships, reflecting the changes in temperature and chemical properties of hydrothermal fluids. Based on the alteration characteristics of the surrounding rocks, the diffusion paths of hydrothermal fluids and different mineralization stages are identified. Combined with microscopic identification of rock thin sections, the mineral composition, grain size, and relative content of phenocrysts and matrix are observed, and the distribution and interrelationships of alteration minerals are recorded to reveal the connection with hydrothermal activity. The location of the mineralization center and the hydrothermal evolution process are inferred through the zoning characteristics of alteration minerals. Furthermore, by assessing the content, distribution, and grade variation trends of mineralized minerals, the enrichment degree of the ore-forming hydrothermal fluids is inferred. Combined with existing porphyry copper deposit models (such as the Lowell-Guilbert model), the mineralization characteristics of the study area are compared with those of the classical model to assess whether there is mineralization potential.

[0005] (2) Remote sensing imagery and spatial modeling: Multispectral and hyperspectral remote sensing data are used to identify surface mineral anomalies within the region. Based on remote sensing influences, the spatial distribution of mineral assemblages is extracted, alteration zones (such as potassic alteration, sericitization, phyllostification, and advanced argillaceization) are drawn, and the geometric characteristics and relative positions of the alteration zones are analyzed to determine possible hydrothermal centers. Digital simulations are used to extract the structure of faults and the morphology of intrusive bodies, analyze their spatial relationship with mineralization, and identify possible mineralization channels and fluid migration directions. The mineralization anomaly data and geological data extracted from remote sensing are integrated to establish a regional metallogenic geological model and analyze the metallogenic controlling factors.

[0006] Using geological methods and remote sensing imagery to determine the thermal evolution of porphyry copper deposits has certain value and is an important tool for geological exploration. However, it still has some limitations and shortcomings, mainly including the following:

[0007] (1) Due to the influence of later geological processes, the mining area may have experienced multiple phases of hydrothermal activity and later alteration, which may have caused the early alteration characteristics to be covered or changed by later alteration, making it difficult to determine the time sequence of hydrothermal activity. Tectonic activities such as faults and folds may be destroyed or reshaped the ore body and alteration zoning, resulting in information confusion and affecting the accuracy of hydrothermal evolution.

[0008] (2) Subjective information is strong. Geological mapping and the identification of alteration zones depend heavily on the researcher's experience and judgment, which may lead to subjective bias. Geological methods with limited regional coverage mainly rely on field observations, which have limited revelation of hydrothermal evolution processes in deep and distant areas of mining areas.

[0009] (3) When using mineralogical and mineral assemblage analysis methods, the mineral composition in porphyry copper deposits is usually quite complex. Many minerals can transform into each other under hydrothermal action. Therefore, relying solely on mineralogical analysis to determine the hydrothermal evolution process is easily interfered with and it is not easy to accurately determine the changes in hydrothermal composition. The mineral characteristics of different alteration zones may overlap, and due to the influence of multiple hydrothermal phases, it is difficult to distinguish the hydrothermal evolution process at each stage.

[0010] (4) Isotope analysis and geochemical analysis have limitations. Changes in oxygen isotopes reflect the source, temperature, and water-rock reaction process of hydrothermal fluids. By analyzing the oxygen isotopes of minerals, the temperature of hydrothermal fluids and the source of oxygen can be estimated. Sulfur isotopes provide information on the source of sulfur in hydrothermal fluids and the redox conditions of hydrothermal fluids, helping to determine the stage of hydrothermal evolution and the mineralization process. However, although the analysis of oxygen, sulfur, and other isotopes can provide information on the source of hydrothermal fluids and the mineralization environment, their isotopic composition is often affected by various factors such as the interaction between multiple hydrothermal fluids and the surrounding rocks and mineral changes. The mineralization process of porphyry copper deposits usually involves complex hydrothermal composition evolution. The migration and precipitation characteristics of elements such as Fe, Cu, and Ti under different conditions may be complex and variable. Therefore, the results of elemental analysis may not be able to simply reflect the entire process of hydrothermal evolution.

[0011] (5) Spatial resolution limitations: Conventional remote sensing data has limited spatial resolution, making it difficult to accurately identify small-scale alteration zones and the migration direction of ore-forming fluids. High-resolution images are costly and have limited coverage, making it difficult to meet the needs of comprehensive exploration of large-scale mining areas. Spectral resolution limitations also hinder the detailed identification of minerals. Multispectral remote sensing images, in particular, have limited spectral resolution, making it impossible to accurately distinguish mineral-related minerals. Furthermore, because a single pixel in a low-resolution image may contain multiple minerals, mineral characteristic information is confused, leading to mixed pixel problems. Additionally, surface cover, such as snow and glaciers in high-altitude areas, interferes with the spectral signals of rocks and minerals. Long-term weathering may obscure the spectral characteristics of primary minerals, making it difficult to reflect the true information of hydrothermal evolution processes. Summary of the Invention

[0012] The purpose of this invention is to provide a method for predicting the hydrothermal evolution and mineralization of porphyry copper deposits based on rutile. By using rutile, an alteration material widely found in porphyry copper deposits, as an indicator of whether porphyry copper deposits are mineralized, this method not only improves the efficiency and accuracy of prospecting in porphyry copper deposits, but also solves the problems of high difficulty, long cycle, and low efficiency in prospecting in the deep edges of deposits.

[0013] To achieve the above-mentioned objectives, the embodiments of the present invention provide the following technical solutions:

[0014] A method for hydrothermal evolution and mineralization prediction of porphyry copper deposits based on rutile includes the following steps:

[0015] Step 1: Collect rock samples within the mining area at fixed intervals, screen out rock samples containing rutile, and mark the location of rutile in the rock samples;

[0016] Step 2: Divide the rock mass sample from the same location into two parts. Make a probe slide from one part of the rock mass sample, delineate the location of rutile in the probe slide, and determine the enrichment degree, occurrence state, color and grain size of rutile in different alteration zones by the crystal form and internal structure characteristics of rutile, and obtain the variation trend of rutile morphological characteristics in different alteration zones.

[0017] Step 3: Use scanning electron microscopy to perform rutile backscatter photography and energy dispersive spectroscopy analysis on the rutile-delineated areas in the probe slide to obtain the variation trend of rutile inclusion mineral content in different alteration zones.

[0018] Step 4: Perform laser-etched inductively coupled plasma mass spectrometry in-situ micro-area elemental analysis on another part of the rutile to obtain the content data of major and trace elements in the rutile and obtain the variation trend of the content of major and trace elements in the rutile in different alteration zones.

[0019] Step 5: Analyze the elemental content data in the rutile sample and the changing trends obtained in Steps 2, 3, and 4. Based on the location of the alteration zone where the rutile is located, determine the hydrothermal center and thus the mineralization potential.

[0020] Furthermore, step 1 specifically includes the following steps:

[0021] Rock samples were collected at fixed intervals from different alteration zones within the mining area. The alteration zones developed sequentially from the inside to the outside as follows: potassium silicate alteration zone → chlorite-sericite alteration zone → pyrite-sericite alteration zone → cyanite alteration zone.

[0022] The rock samples were treated with tribromomethane heavy liquid to remove minerals and select those containing rutile. During the selection process, magnetic separation was used to separate magnetite to ensure that the purity of rutile was greater than 95%.

[0023] Furthermore, in step 4, the major and trace elements in rutile include: Al, Ca, K, Cu, Ni, Co, Pb, Sc, Zr, Sb, Sr, Ba, Na, Au, Mo, V, Cr, Mn, Fe, W, Nb, Hf, Ta, Th, and REE.

[0024] Furthermore, in step 5, hydrothermal centers are determined according to the following criteria, thereby determining the mineralization potential:

[0025] (1) The larger the grain size and the darker the color of rutile, the closer it is to the mineralization center and the closer it is to the ore-bearing site, and the greater its mineralization potential.

[0026] (2) The more sphene a rutile inclusion contains, the closer it is to the mineralization center; the more xenotime and monazite mineral assemblages a rutile inclusion contains, the closer it is to the hydrothermal center.

[0027] (3) If the content of elements Cr and Sr is low, and the content of elements Sc, V, Zr, Hf, W and U is high, then the alteration zone is a mineralized alteration zone. The closer the rutile is to the hydrothermal center, the higher the mineralization potential. If the content of elements Sc, V, Zr, Sb and Hf is low, and the content of elements Cr, Fe and Sr is high, then the alteration zone is a non-mineralized alteration zone. The farther the rutile is from the hydrothermal center, the lower the mineralization potential.

[0028] Compared with existing technologies, the beneficial effects of this invention are as follows: By analyzing the content of major and trace elements Al, Ca, K, Cu, Ni, Co, Pb, Sc, Zr, Sb, Sr, Ba, Na, Au, Mo, V, Cr, Mn, Fe, W, Nb, Hf, Ta, Th, and REE in rutile from different alteration zones, variation curves about alteration zones can be generated. The variation trends and extreme values ​​of the curves can be identified. Combined with microscopic morphological characteristics and the type of inclusion minerals, the mineralization potential of hydrothermal centers can be analyzed and predicted. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The potassium silicate alteration zone of the No. 1 ore body in the Xiongcun mining area in Example 2 of this invention ( Figure 1 a, b, c, d, i), sericitization alteration zone ( Figure 1 In the e, f, j) rutile and sphene in the surrounding phyllitic alteration zone ( Figure 1 Microscopic features and backscattered images of g, h, and k in the image;

[0031] Figures 2(a), 2(b), and 2(c) are curves showing the content of some major and trace elements in rutile in Example 2 of the present invention. Among them, (a) is the Cr element content curve, (b) is the Sc element content curve, (c) is the V element content curve, (d) is the Fe element content curve, (e) is the Sr element content curve, (f) is the Zr element content curve, (g) is the Nb element content curve, (h) is the Sb element content curve, (i) is the Hf element content curve, (j) is the W element content curve, and (k) is the U element content curve.

[0032] Figure 3 This is a flowchart of the method of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance, or suggesting any such actual relationship or order between these entities or operations. Additionally, the terms "connected," "linked," etc., can refer to a direct connection between elements or an indirect connection via other elements.

[0035] Example 1:

[0036] This invention is achieved through the following technical solutions, such as... Figure 3 As shown, a method for hydrothermal evolution and mineralization prediction of porphyry copper deposits based on rutile includes the following steps:

[0037] Step 1: Collect rock samples within the mining area at fixed intervals, screen out rock samples containing rutile, and mark the location of rutile in the rock samples.

[0038] Rock samples were collected at fixed intervals from different alteration zones within the mining area. The alteration zones, from the inside out, are: potassic silicate alteration zone → chlorite-sericite alteration zone → pyrite-sericite alteration zone → propylitic alteration zone. The rock samples were treated with tribromomethane heavy liquid to remove low-density minerals such as quartz and feldspar, and rutile-containing samples were selected. During the selection process, magnetic separation of magnetite was employed to ensure that the purity of rutile was greater than 95%.

[0039] Rutile, as an alteration mineral, is widely distributed in strongly altered porphyry systems associated with copper mineralization, and it is present in multiple stages of deposit formation. This scheme reveals that the enrichment level, grain size, and chemical composition of rutile can reflect the intensity of hydrothermal alteration and mineralization. Therefore, this scheme uses the mineral typographic characteristics of rutile in different alteration zones to guide mineral exploration. Since the physical structure and chemical composition of rutile vary significantly across different alteration zones, the evolution stage of ore-forming fluids can be inverted based on the typographic mineral characteristics of rutile (including enrichment level, occurrence state, color, grain size, and major and trace element characteristics). This evolution stage is directly related to the spatial distribution of alteration zones (from the center to the periphery). Therefore, by combining alteration zone zoning models with rutile geochemical data, the mineralization potential of the region can be accurately determined.

[0040] However, current research on rutile in different alteration zones of porphyry mineralization systems is limited. Previous studies have mostly used electron probe microanalysis (EPMA) to analyze rutile geochemical data, focusing only on single-element analysis and exhibiting low precision in trace element detection, potentially revealing issues such as Ti and O vacancies. Compared to minerals susceptible to weathering or alteration (such as montmorillonite and kaolinite), rutile demonstrates high stability in hydrothermal and later-stage environments. Its chemical composition is less susceptible to external interference, allowing it to record key information about mineralization events over long periods, especially in multi-stage superimposed mineralization systems. Existing hydrothermal evolution identification techniques for porphyry copper deposits lack systematic utilization of key single minerals, have limited data indicators, and cannot quickly quantify mineralization potential. This invention addresses the problems of existing techniques for identifying hydrothermal evolution in porphyry copper deposits, such as the lack of systematic utilization of key single minerals, limited data indicators, and inability to quickly quantify mineralization potential. By exploring the relationship between rutile enrichment, occurrence state, color, grain size, and major and trace element characteristics and mineralization processes, this invention establishes a method for rapidly determining the hydrothermal evolution process and predicting the mineralization potential of porphyry copper deposits using the characteristics of rutile typological minerals in different alteration zones. This method has significant practical implications for guiding the exploration of porphyry deposits.

[0041] This innovative approach employs a "dual-channel sample preparation method," where rutile-containing rock samples from the same sampling location are divided into two parts. One part is used to prepare probe slides and analyze the morphological characteristics of rutile and its inclusion minerals; the other part is used for single-mineral selection analysis of the major and trace element content of rutile. This zonal sampling-dual-sample system processing method ensures high data consistency and cross-sectional comparability, providing a foundation for judging the trend of major and trace element content indicators.

[0042] Step 2: Divide the rock mass sample from the same location into two parts. Make a probe slide from one part of the rock mass sample, delineate the location of rutile in the probe slide, and determine the enrichment degree, occurrence state, color and grain size of rutile in different alteration zones by the crystal form and internal structure characteristics of rutile, and obtain the variation trend of rutile morphological characteristics in different alteration zones.

[0043] A portion of the collected rock samples was ground into probe slides, which were then examined under a microscope to pinpoint the location of rutile. Microscopic observation of the rutile morphology revealed a non-monotonic grain size variation from the center of the alteration zone outwards, exhibiting a trend of "small → large → small," with a positive correlation between grain size and temperature. This grain size variation fully reflects the entire process of the ore-forming fluid, from "Ti enrichment, high temperature, and strong activity" to "Ti depletion, low temperature, and weak activity."

[0044] Large-grained rutile can serve as a marker feature of sericitization zones, and the potassic zones (chalcopyrite and bornite enrichment areas) in porphyry copper deposits are important areas for the precipitation of Cu from ore-forming fluids. Therefore, the distribution range of large-grained rutile can indicate the potential location of mineralization zones.

[0045] Step 3: Using a scanning electron microscope, the region in the probe slide delineated by rutile is subjected to rutile backscatter photography and energy dispersive spectroscopy analysis to obtain the variation trend of rutile inclusion mineral content in different alteration zones.

[0046] If the backscattered images at the same location have consistent brightness, they are considered to be from the same generation. Energy dispersive spectroscopy (EDS) analysis can determine whether there are other mineral inclusions inside rutile, such as sphene, xenotime, monazite, quartz, plagioclase, etc., and the content variation trend of various mineral inclusions.

[0047] Step 4: Perform laser-etched inductively coupled plasma mass spectrometry in-situ micro-area elemental analysis on another portion of rutile to obtain the content data of major and trace elements in rutile and obtain the variation trend of the content of major and trace elements in rutile in different alteration zones.

[0048] Another portion of rutile used for single-mineral selection in step 1 was subjected to in-situ micro-area elemental analysis using laser-induced polarization-inductively coupled plasma mass spectrometry (LA-ICP-MS). Rutile particles larger than 10 micrometers with euhedral or subhedral shape, free of bubbles and flaking on the surface were selected to obtain the content data of major and trace elements. Major and trace elements include Al, Ca, K, Cu, Ni, Co, Pb, Sc, Zr, Sb, Sr, Ba, Na, Au, Mo, V, Cr, Mn, Fe, W, Nb, Hf, Ta, Th, and REE.

[0049] Calculate the average value of the major and trace element contents in all rutiles, and create a curve showing the change of this average value with alteration zones to obtain the changing trend of the major and trace element contents in rutiles in different alteration zones.

[0050] Based on the obtained data on major and trace element contents, comparing the changes in the contents of major and trace elements in rutile within different alteration zones, if the contents of Fe, Al, Mg, K, Ca, Pb, Cu, Mn, Ni, and Co decrease from the center of the hydrothermal fluid outwards through potassic alteration → chlorite-sericite alteration → pyrite-sericite alteration, while the contents of Zr, Hf, Cr, and Mo increase sequentially from potassic alteration → chlorite-sericite alteration, this reflects the evolution of the fluid from a reducing (Fe enrichment) to an oxidizing (Fe loss) state. In this case, the Cu content exhibits significant zonation in each alteration zone: potassic alteration zone (20-50 ppm) > chlorite-sericite alteration zone (10-30 ppm) > pyrite-sericite alteration zone (<10 ppm). The Cu content from the center outwards of the alteration zone is positively correlated with the Cu mineralization intensity; the decreasing Cu content reflects the Cu content in the fluid. 2+ The decrease in activity is related to the precipitation of sulfides caused by the decrease in hydrothermal temperature and sulfur fugacity. If Cu / V > 5 in the potassic alteration zone, it indicates high mineralization potential; if Cu / V < 1 in the cyanitic alteration zone, it indicates low mineralization potential. The LaN / YbN ratio in the REE fractionation model gradually decreases from the potassic alteration zone (9) → chlorite-sericite alteration zone (4.8) → pyrite-sericite flower zone (3.4), indicating that the enrichment of light rare earth elements gradually weakens as the alteration zone moves outward, and the hydrothermal fluid evolves from high-temperature closure to low-temperature opening. Overall, it is consistent with the spatial zoning pattern of mineralization.

[0051] Meanwhile, W and V also have a synergistic indicative effect: the W content is significantly increased in the potassic silicate zone (>50ppm) and is related to Cu / Mo coprecipitation, which means that there are more dissolved metal components in the hydrothermal fluid and the mineralization is strong. When W>50ppm and V>200ppm, it indicates the presence of unexposed Cu-Mo ore bodies at depth and is positively correlated with Cu mineralization.

[0052] The above methods can be directly used for identifying hydrothermal evolution stages and determining mineralization intensity. Furthermore, the introduction of a zonal comparison mechanism analyzes elemental content changes in alteration assemblages, providing a new method for quantitative evaluation. Target area delineation can be completed within 7 days through in-situ micro-area analysis of rutile using LA-ICP-MS combined with microscopic identification, reducing exploration costs by 60%.

[0053] Step 5: Analyze the elemental content data in the rutile sample and the changing trends obtained in steps 2, 3, and 4. Based on the location of the rutile in the alteration zone, determine the hydrothermal center according to the following criteria, and then determine the mineralization potential:

[0054] (1) The larger the grain size and the darker the color of rutile, the closer it is to the mineralization center (i.e., the sericitization zone), and the closer it is to the ore-bearing location, the greater its mineralization potential.

[0055] (2) The more sphene a rutile inclusion contains, the closer it is to the mineralization center (i.e., the sericitization zone). The more xenotime and monazite mineral assemblages a rutile inclusion contains, the closer it is to the hydrothermal center (i.e., the potassic zone).

[0056] (3) The major and trace element contents of ore-bearing alteration zones generally have the following characteristics: low Cr and Sr, high Sc, V, Zr, Hf, W, and U; the relevant elements of non-ore-bearing alteration zones generally have the following characteristics: low Sc, V, Zr, Sb, and Hf, high Cr, Fe, and Sr. Therefore, the lower the Cr and Sr content, the higher the Sc, V, Zr, Hf, W, and U content, the closer the rutile is to the hydrothermal center, and the higher its mineralization potential; the lower the Sc, V, Zr, Sb, and Hf content, the higher the Cr, Fe, and Sr content, the farther the rutile is from the hydrothermal center, and the lower its mineralization potential.

[0057] According to a specific embodiment of the present invention, the criterion for judging mineralization potential is as follows: if the alteration zone where the rutile is located is a mineralization alteration zone, then the mineralization potential is high (the probability of finding related minerals is >50%), and a mineralization target area is delineated within a certain radius based on the location of the rutile. If the alteration zone where the rutile is located is a non-mineralization alteration zone, then the mineralization potential is low (the probability of finding related minerals is <50%), and no mineralization target area delineation is performed.

[0058] This invention can generate variation curves of alteration zones by analyzing the content of major and trace elements Al, Ca, K, Cu, Ni, Co, Pb, Sc, Zr, Sb, Sr, Ba, Na, Au, Mo, V, Cr, Mn, Fe, W, Nb, Hf, Ta, Th, and REE in rutile from different alteration zones. By identifying the variation trends and extreme values ​​of the curves and combining them with microscopic morphological characteristics and the types of mineral inclusions, the invention can further analyze the hydrothermal center and predict its mineralization potential.

[0059] Example 2:

[0060] This embodiment takes the Xiongcun copper-gold deposit on the southern margin of the central section of the Gangdise metallogenic belt in Tibet as an example to verify the predictive effect of the present invention on the hydrothermal evolution process and mineralization potential of porphyry copper deposits.

[0061] Rutile from ore bodies I and II (both already identified as copper deposits) in the mining area was selected as the research object. Petrographic observation of hydrothermal alteration assemblages was used to identify the alteration zoning of the deposit. Rutile-bearing rock samples were taken from different depths in the mining area. According to the Xiongcun mining area, from the porphyry body outwards and from shallow to deep, the alteration zones are: potassic silicate alteration zone, chlorite-sericite alteration zone, pyrite-sericite alteration zone, and peripheral propylitic alteration zone. Ore body I was mainly collected from the potassic silicate alteration zone, chlorite-sericite alteration zone, and pyrite-sericite alteration zone, while ore body II was mainly collected from the pyrite-sericite alteration zone and the peripheral propylitic alteration zone.

[0062] To determine the mineral and chemical characteristics of rutile in different alteration zones, rutile rock samples were taken from drill cores of different alteration zones in the mining area. These samples were then cut in the laboratory to prepare probe slides with a thickness of approximately 0.03-0.05 mm. The slides were then identified under an electron microscope, and the location and grain size of rutile in each rock sample were observed and recorded.

[0063] In the potassium silicate alteration zone of ore body I, rutile is mainly columnar and irregularly granular, with grain size mostly concentrated between 50-100 μm, and a few grains reaching 200 μm. A set of perfect cleavage is visible on the surface of the grains. Under the microscope, it is yellowish-brown or dark red. There are few inclusion minerals in rutile, but a few grains contain at least two kinds of unknown inclusion minerals. Furthermore, no sphene was found in this alteration zone.

[0064] In the sericitized alteration zone of ore body II, rutile is mainly irregularly granular, with a few rhomboid granules, often forming granular aggregates. The grain size is concentrated between 70-120 μm, and it appears brownish-green under the microscope. Sphene is also visible in the sericitized alteration zone, and quartz and plagioclase are often developed at its edges. A large amount of rutile enrichment was found in the propylitized alteration zone surrounding ore body II. In this alteration zone, rutile is mainly irregularly granular, with a few columnar forms. The granules are mostly distributed between 50-100 μm, mostly associated with sphene, and also contain pyrite and unknown inclusions. In thin sections, wedge-shaped and irregularly granular sphene can be seen distributed between quartz grains, with sphene grain sizes reaching up to 250 μm.

[0065] The rutile contains numerous inclusions of minerals, including: (a) in the potassium silicate alteration zone of ore body I, the inclusions of rutile include apatite, xenotime, mica (residual biotite), and Ti-rich pyrite; (b) in the chlorite-sericite alteration zone of ore body I, the inclusions of rutile include mica, feldspar, Ti-rich pyrite, zircon (ZrTiO4), sphene, pseudorutile, and Cu-Fe sulfides; (c) in ore body I... The rutile inclusions in the pyrite-sericite alteration zone include quartz, feldspar, mica, zircon (ZrTiO4), and fluorapatite; (d) the rutile inclusions in the cyanitic alteration zone surrounding orebody II include feldspar, quartz, apatite, mica, Cu-Fe sulfides, and zircon (ZrTiO4); (e) the rutile inclusions in the sodium alteration-calcification superimposed potassium silicate alteration zone of orebody II are rare.

[0066] In-situ micro-area elemental analysis of rutile in each rock mass sample was performed using LA-ICP-MS. Based on the measured major and trace element content data, the average values ​​of each major and trace element in rutile from different alteration zones were calculated, and then curves showing the variation of each average value with alteration zone were plotted as shown in Figures 2(a), 2(b), and 2(c).

[0067] The mineral chemical composition of rutile varies somewhat in different alteration zones of Ore Body I. In the potassic silicate alteration zone, the total elemental content is low, mostly below 97%. TiO2 content ranges from 93.31% to 99.06%, Fe2O3 from 0.03% to 0.40%, V2O5 from 0.31% to 1.80%, BaO from 0.52% to 0.67%, Cr2O3 is less than 0.19%, and WO3 is less than 0.34%. WO3 content varies greatly, ranging from less than 0.03% to 7.04%. In the pyrite-sericite alteration zone, the TiO2 content of rutile is relatively stable, V2O5 ranges from 0.62% to 1.03%, BaO from 0.62% to 0.71%, and WO3 is less than 0.16%.

[0068] The rutile content in ore body II is relatively low. Limited studies show that the TiO2 content of rutile in its sodium alteration-calcification superimposed potassium silicate alteration zone ranges from 92.27% to 97.62%, with a few low TiO2 particles mainly due to higher SiO2 content (up to 3.21%). Fe2O3 is distributed at 0.29% to 0.62%, V2O5 at 0.68% to 1.03%, BaO at 0.51% to 0.57%, Cr2O3 at less than 0.07%, and WO3 at less than 0.38%. The rutile content in the cyanitic alteration zone surrounding the No. 2 ore body is relatively rich, and the TiO2 content is relatively uniform, ranging from 96.85% to 99.32%; Fe2O3 ranges from 0.06% to 1.03%, V2O5 from 0.39% to 1.45%, BaO from 0.51% to 0.64%, Cr2O3 is less than 0.46%, and WO3 content is low.

[0069] In-situ micro-area elemental analysis by LA-ICP-MS on different alteration zones revealed certain differences in the geochemical characteristics of rutile elements. These differences are mainly reflected in the following aspects: (a) From potassic alteration → chlorite-sericite alteration → pyrite-sericite alteration, the elements with decreasing content are Fe, Al, Mg, K, Ca, Pb, Cu, Mn, Ni, and Co; (b) From potassic alteration → chlorite-sericite alteration → pyrite-sericite alteration, the elements with increasing content are Zr, Hf, Cr, and Mo, with Cr and Mo showing little difference in content between the potassic alteration and chlorite-sericite alteration zones; (c) In the potassic alteration and chlorite-sericite alteration zones, the elements with decreasing content are Fe, Al, Mg, K, Ca, Pb, Cu, Mn, Ni, and Co; (d) In the potassic alteration and chlorite-sericite alteration zones, the elements with decreasing content are Zr, Hf, Cr, and Mo, with Cr and Mo showing little difference in content between the two alteration zones; The elements present in comparable amounts in the three alteration zones of mudstone-sericite alteration, pyrite-sericite alteration, and chlorite-sericite alteration include Sc, Sb, Ta, Na, Sr, Ba, Th, and Au; (d) the elements in the alteration zone of potassic silicate alteration > pyrite-sericite alteration > chlorite-sericite alteration include K and REE; (e) the elements in the alteration zone of chlorite-sericite alteration > potassic silicate alteration > pyrite-sericite alteration are mainly V; (f) the elements in the alteration zone of chlorite-sericite alteration > pyrite-sericite alteration > potassic silicate alteration are W.

[0070] Furthermore, based on the study of the geochemical characteristics of rutile elements in the cyanitic alteration zone surrounding ore body II, the elements with higher content than those in the three alteration zones of ore body I include Fe, Si, Mg, Ca, Pb, Na, Cr, Mn, Sr, Ba, REE, and Th, while the elements with lower content than those in the three alteration zones include Sc, Sb, and Hf. Other trace elements are similar in content to those in the three alteration zones of ore body I.

[0071] Based on the aforementioned rutile occurrence state, elemental geochemical characteristics, and inclusion mineral types, combined with the mineral assemblage characteristics of different hydrothermal alteration stages, the formation mechanism of rutile in the potassium silicate alteration stage may be mainly controlled by: K(Fe,Mg,Ti)3(Si3Al)O 10 (OH)2 + S2 = K(Mg,Fe)3(Si3Al)O 10 (OH)2 + FeS2 + TiO2. Furthermore, during the potassic silicate alteration stage, a large amount of rutile coexists with Ti-poor phlogopite, and the Cu content of rutile decreases sequentially from the potassic silicate alteration, chlorite-sericite alteration, to the pyrite-sericite alteration zone. Since the chemical composition of hydrothermal rutile is mainly influenced by the fluid composition and precursor minerals, the Cu content of biotite in the potassic silicate alteration zone is extremely low. This change in Cu content most likely reflects the change in Cu content in the fluid. Therefore, the Cu content in rutile can serve as an indicator element for judging the strength of mineralization and the evolution of hydrothermal fluids. Rutile in the potassic silicate alteration zone contains a large number of rare earth element-rich inclusions (mainly monazite, with smaller amounts of apatite and xenotime), and has a higher ∑REE content compared to other alteration zones. La in rutile... N / Yb NThere is moderate fractionation, with the alteration zones being 9, 4.8, and 3.4 in the potassium silicate alteration, chlorite-serice alteration, and pyrite-serice alteration zones, respectively. Both REE and Y form complexes with F, therefore the solubility of rare earth elements is controlled by the activity of F in the hydrothermal fluid. Compared to other alteration zones, the presence of abundant rare earth mineral inclusions in rutile within the potassium silicate alteration zone may indicate that F had higher activity during the potassium silicate alteration process.

[0072] The formation of rutile in the chlorite-sericite alteration zone is complex. Some sphene is encased within rutile. Besides the Ti released from biotite alteration into phlogopite, some sphene also transforms into rutile. The transformation of sphene into rutile mainly occurs in S-poor, CO2-rich sericitization alteration zones, where sphene transforms into rutile, calcite, and quartz; or in S-rich, strongly oxidizing environments, where sphene transforms into rutile, anhydrite, and quartz. The association of rutile with Cu-Fe sulfides in this alteration zone indicates an overall S-rich environment. Rutile formation is likely primarily controlled by the transformation of Ti-rich biotite into Ti-poor phlogopite or its alteration into chlorite, and secondarily by the reaction: CaTiSiO5 + SO3 = TiO2 + CaSO4 + SiO2. The chlorite-sericite alteration zone of the Xiongcun No. 1 orebody has a significantly higher ore grade than other alteration zones, but its distribution range is relatively narrow. The rutile within this alteration zone contains Cu-Fe sulfide inclusions, indicating substantial precipitation of ore-forming materials. Notably, the W content of rutile in this chlorite-sericite alteration zone is also higher than in other alteration zones, consistent with the trend in Cu and Au grade variations in the corresponding samples. Therefore, W in rutile is a potential indicator element for mineralization. The V content in the chlorite-sericite alteration zone is also higher than in other alteration zones.

[0073] Rutile is considered the only Ti-rich mineral in the pyrite-sericite alteration zone. In the Xiongcun No. 1 ore body, the Zr, Hf, Cr, and Mo content in rutile from the pyrite-sericite alteration zone is significantly higher than in other alteration zones. Fluid-immobile elements such as Zr, Hf, and Cr did not decrease during the alteration process but rather increased significantly, reflecting the importance of rutile inheriting trace elements from its precursor minerals. Rutile is associated with mica in the pyrite-sericite alteration zone, suggesting that the release of Ti from mica during alteration may be the main mechanism of its formation. Zirconium-titanium zircon was found in some rutile grains, possibly indicating the following reaction: ZrSiO4 + TiO2 = ZrTiO4 + SiO2. This reaction also exists in the chlorite-sericite alteration zone. The Zr content in biotite in the chlorite-sericite alteration and pyrite-sericite alteration is significantly higher than in the potassium silicate alteration, which may explain the presence of Zr-rich inclusions in the rutile in both.

[0074] The Fe, Mg, Mn, and Sr elements in the phyllitic alteration zone surrounding orebody II are higher than those in different alteration zones of orebody I. The high Cr content in rutile may also originate from precursor minerals, possibly reflecting the involvement of more mafic magma. Furthermore, the Sc, Sb, and Hf contents in the phyllitic alteration zone are relatively low. Increased oxygen fugacity leads to an increased Sb partition coefficient; when oxygen fugacity increases, Sb is predominantly distributed as Sb. 5+ Entering the rutile. The Sb in the rutile of the peripheral cyanitic alteration zone is significantly lower than that in different alteration zones of ore body I and the sodium alteration-calcification superimposed potassium silicate alteration zone of ore body II (136 ppm), which may indicate that the magma oxygen fugacity in the peripheral cyanitic alteration zone is low. This is consistent with the magma oxygen fugacity results obtained by zircon trace element quantitative analysis (ΔFMQ+1.1 for the ore-bearing porphyry of ore body I, ΔFMQ+1.29 for the ore-bearing porphyry of ore body II, and ΔFMQ+0.96 for the non-ore-bearing porphyry surrounding ore body II).

[0075] Experiments on the distribution of V between rutile and melt suggest that in the oxidized state (V is V0), V0 is used to distribute V0. 4+ V 5+ When present, V exhibits the lowest partition coefficient, while reduction conditions result in the highest partition coefficient. When oxygen fugacity is between QFM and NNO, V has a higher partition coefficient (D) between rutile and melt. V =40-141). The compatibility of different valence states V is as follows: V 4+> V 3+ >V 5+ This means that under oxidizing conditions, V increases in the form of V. 4+ Existence, V 4+ / ΣV increases, due to V 4+ It has higher compatibility, D V It will increase; under reducing conditions, V increases with V 3+ Existence, V 3+ / ΣV increases, due to V 3+ With Nb 5+ Coupling substitution of Ti in rutile leads to an increase in Nb in rutile; however, when oxidation conditions are sufficiently high, V increases with Vo. 5+ Existence, V 5+ / ΣV increases, due to V 5+ It has the lowest compatibility, D V It will decrease. In the chlorite-sericite alteration zone of the Xiongcun mining area, V and Nb enter rutile as compensating charges, while in other alteration zones, Ti is jointly replaced by ion clusters. From a correlation perspective, except for the potassic silicate alteration zone where Nb and V are negatively correlated to some extent, there is no correlation between the two in other alteration zones.

[0076] like Figure 1 The image shows the potassium silicate alteration zone of ore body No. 1 in the Xiongcun mining area. Figure 1a, b, c, d, i), sericitization alteration zone ( Figure 1 In the e, f, j) rutile and sphene in the surrounding phyllitic alteration zone ( Figure 1 Microscopic features and backscattered images of g, h, and k in the image. Based on Figure 1 Figures 2(a), 2(b), and 2(c) show the minimum values ​​of Cr and Sr in rutile and the maximum values ​​of Sc, V, Zr, Hf, W, and U, which appear between the chlorite-sericite alteration zone and the pyrite-sericite alteration zone. Microscopic identification also reveals sphene inclusions. The minimum values ​​of Sc, V, Zr, Sb, and Hf and the maximum values ​​of Cr, Fe, and Sr appear near the cyanitic alteration zone. Therefore, the chlorite-sericite alteration zone and the pyrite-sericite alteration zone are identified as the main mineralization sites with significant mineralization potential, allowing for target area delineation. According to the actual exploration results of the mining area, the main mineralization zone of the Xiongcun deposit No. 1 ore body is located in the sericite alteration zone. The results obtained from the microscopic characteristics of rutile, the type of inclusion minerals, and the characteristics of mineral chemical composition in the examples are largely consistent, indicating that the results of this invention are reliable.

[0077] In addition, accessory minerals or alteration minerals such as apatite and chlorite in porphyry copper deposits can also be used to help predict the direction and approximate location of potential mineralization centers, as well as to assess the scale of mineralization. Taking apatite as an example, its chemical composition can quickly and effectively determine the center location of mineralization in porphyry deposits. Apatite from different alteration zones in porphyry deposits exhibits significantly different cathodoluminescence (CAT) patterns and trace element compositions. The CAT of unaltered apatite shows both yellow and brown colors. Apatite with a yellow CAT pattern has high Mn (MnO: 0.3%~0.5%; Mn / Fe ratio > 1) and REE+ Y content, while apatite with brown CAT features has lower Mn content but higher S and REE+ Y content. The CAT of apatite in the potassic silicate alteration zone is green, and the Mn / Fe ratio (Mn / Fe ≈ 1) is lower than that in unaltered apatite. Apatite in the sericitized alteration zone exhibits gray cathodoluminescence images. The REE content in apatite gradually decreases in both the potassium silicate alteration zone and the sericitized zone. On the chondrite-normalized REE distribution map of apatite, unaltered apatite shows a strong negative Eu anomaly, while apatite in the sericitized alteration zone lacks an Eu anomaly. Therefore, variations in REE content in apatite can effectively reveal subtle changes in the formation environment.

[0078] Therefore, in a certain porphyry deposit, the cathodoluminescence image and trace element content of apatite can effectively and quickly determine the alteration zone and mineralization center of porphyry mineralization. However, apatite as an indicator mineral is not applicable to the No. I and No. II ore bodies of the Xiongcun deposit. Compared with ruthenium, which appears in all alteration zones, apatite only exists in the potassium silicate zone and is not universal.

[0079] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for predicting the hydrothermal evolution and mineralization of porphyry copper deposits based on rutile, characterized in that, Includes the following steps: Step 1: Collect rock samples within the mining area at fixed intervals, screen out rock samples containing rutile, and mark the location of rutile in the rock samples; Step 2: Divide the rock mass sample from the same location into two parts. Make a probe slide from one part of the rock mass sample, delineate the location of rutile in the probe slide, and determine the enrichment degree, occurrence state, color and grain size of rutile in different alteration zones by the crystal form and internal structure characteristics of rutile, and obtain the variation trend of rutile morphological characteristics in different alteration zones. Step 3: Use scanning electron microscopy to perform rutile backscatter photography and energy dispersive spectroscopy analysis on the rutile-delineated areas in the probe slide to obtain the variation trend of rutile inclusion mineral content in different alteration zones. Step 4: Perform laser-etched inductively coupled plasma mass spectrometry in-situ micro-area elemental analysis on another part of the rutile to obtain the content data of major and trace elements in the rutile and obtain the variation trend of the content of major and trace elements in the rutile in different alteration zones. Step 5: Analyze the elemental content data in the rutile sample and the changing trends obtained in Steps 2, 3, and 4. Based on the location of the alteration zone where the rutile is located, determine the hydrothermal center and thus the mineralization potential.

2. The method for hydrothermal evolution and mineralization prediction of porphyry copper deposits based on rutile according to claim 1, characterized in that, Step 1 specifically includes the following steps: Rock samples were collected at fixed intervals from different alteration zones within the mining area. The alteration zones developed sequentially from the inside to the outside as follows: potassium silicate alteration zone → chlorite-sericite alteration zone → pyrite-sericite alteration zone → cyanite alteration zone. The rock samples were treated with tribromomethane heavy liquid to remove minerals and select those containing rutile. During the selection process, magnetic separation was used to separate magnetite to ensure that the purity of rutile was greater than 95%.

3. The method for hydrothermal evolution and mineralization prediction of porphyry copper deposits based on rutile according to claim 1, characterized in that, In step 4, the major and trace elements in rutile include: Al, Ca, K, Cu, Ni, Co, Pb, Sc, Zr, Sb, Sr, Ba, Na, Au, Mo, V, Cr, Mn, Fe, W, Nb, Hf, Ta, Th, and REE.

4. The method for hydrothermal evolution and mineralization prediction of porphyry copper deposits based on rutile according to claim 3, characterized in that, In step 5, the hydrothermal center is determined according to the following criteria, thereby determining the mineralization potential: (1) The larger the grain size and the darker the color of rutile, the closer it is to the mineralization center and the closer it is to the ore-bearing site, and the greater its mineralization potential. (2) The more sphene a rutile inclusion contains, the closer it is to the mineralization center; the more xenotime and monazite mineral assemblages a rutile inclusion contains, the closer it is to the hydrothermal center. (3) If the content of elements Cr and Sr is low, and the content of elements Sc, V, Zr, Hf, W and U is high, then the alteration zone is a mineralized alteration zone. The closer the rutile is to the hydrothermal center, the higher the mineralization potential. If the content of elements Sc, V, Zr, Sb and Hf is low, and the content of elements Cr, Fe and Sr is high, then the alteration zone is a non-mineralized alteration zone. The farther the rutile is from the hydrothermal center, the lower the mineralization potential.

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