Ion adsorption type rare earth ore prospecting method based on multi-element composite mineralization mode

Abstract

The invention discloses an ion adsorption type rare earth ore prospecting method based on a multi-element composite mineralization mode, and belongs to the technical field of rare earth ore geological exploration. The method comprises the following steps: firstly, collecting the existing exploration and research data of the known granite weathered crust type rare earth deposit; analyzing the ore-forming basic elements of the known granite weathering crust ion adsorption type rare earth ore deposit; then field geological survey and sample collection are carried out on the known granite weathered crust ion adsorption type rare earth ore deposit; determining each metallogenic mode element by utilizing analysis test data and field survey data; analyzing the formation cause of the ore deposit, establishing a prospecting mark, and constructing a multi-component composite mineralization mode of the granite weathering crust type rare earth ore deposit. And finally, prospecting target area prediction is carried out. For the known high-altitude granite weathering crust ion adsorption type rare earth deposit, multiple exploration technologies are organically fused, the special environment of the high-altitude area is optimized, a multi-element composite mineralization mode is constructed, and brand-new theoretical guidance and technical means are provided for prospecting of ion adsorption type rare earth ore in the high-altitude area.

Description

Technical Field

[0001] The present invention relates to a prospecting method for ion-adsorption type rare earth ore based on a multi-element composite metallogenic model, belonging to the technical field of rare earth ore geological exploration. Background Art

[0002] Rare earth resources are indispensable raw materials or auxiliary materials in the fields of high technology and new materials, and are strategic resources related to the development of emerging industries. Ion-adsorption type rare earth ore, also known as weathered crust type rare earth deposit, is a scarce and precious resource among rare earth resources and is the main source of global heavy rare earth resources. The rare earth elements in these deposits are concentrated and mineralized in the surface weathered crust, with complete rare earth elements, and are characterized by easy beneficiation, high recovery rate, and low mining cost. In particular, they are famous for enriching medium and heavy rare earths, so they have attracted much attention.

[0003] Ion-adsorption type rare earth ore was first discovered in 1969 in the weathered crust of granitic rocks in Longnan area, Ganzhou, China. Later, considerable rare earth resources were also discovered in the weathered crusts of bedrocks such as alkaline igneous rocks (basic-ultrabasic rocks, alkaline granite, alkaline rocks) and metamorphic rocks. Ion-adsorption type rare earth ore is mainly developed in the weathered crust, especially in the weathered crusts of medium-acid granite, acid volcanic rock, metamorphic rock, and limestone. The rare earth elements in these weathered crusts are mainly concentrated in the completely weathered layer and have different degrees of light-heavy rare earth differentiation. The rare earth elements mainly come from the weathering and decomposition of easily weathered and moderately weather-resistant (including) rare earth accessory minerals in the bedrock, such as allanite, monazite, rare earth fluorocarbonate, xenotime, fergusonite, etc. Clay minerals and iron and manganese oxides formed by the weathering of main rock-forming minerals such as feldspar, mica, and hornblende are the main hosting carriers of ionic rare earths in this type of deposit.

[0004] However, ion-adsorption rare earth deposits are usually formed during the Indosinian-Himalayan period and have experienced a long geological history and evolution process. The formation of such deposits often undergoes a complex multi-element composite mineralization process. The complexity of the mineralization mechanism is mainly reflected in aspects such as the mineralization age and the diversity of the parent rock, the geochemical characteristics of rare earth elements, the diversity and genesis of rare earth minerals, the migration and enrichment process of rare earth elements, and the influence of weathering. The interaction and superposition between multiple ore-controlling systems result in an extremely complex and variable control system for such deposits. Therefore, it is difficult to accurately infer the evolution of the mineralization process of the deposit, which brings great difficulties to the exploration work. The construction of mineralization theories and models is the main driving force for major breakthroughs in prospecting and exploration. The ion-adsorption rare earth mineralization theory with Chinese characteristics has played a huge role in the exploration and prospecting prediction of rare earth ores in China. However, compared with the rare earth mineralization types in the low-altitude areas of southern China, the research degree of the ion-adsorption rare earth mineralization type mainly in granite weathering crust in the orogenic belt with high altitude is relatively low, lacking effective mineralization models and exploration methods, making the geological exploration units often have little effect in the process of carrying out rare earth ore exploration in this type of area. For the prospecting of ion-adsorption rare earth ores, the traditional prospecting means and methods include: geological information prospecting method, heavy sand prospecting method, geochemical prospecting method, remote sensing prospecting method, etc. However, the traditional exploration means are restricted by exploration equipment and technology, and the accuracy of resource exploration is restricted to a certain extent. It is difficult to accurately locate potential mineral resources. In addition, due to the thickness of the overburden layer and the complexity of the deep geological environment, it also leads to great exploration difficulties, and the traditional exploration methods face severe challenges in practical applications. Therefore, there is an urgent need for a scientific and effective method to reveal the mineralization of granite weathering crust type ion-adsorption rare earth ores, providing theoretical guidance and technical support for deposit exploration and development.

[0005] In view of the key technical problems that the formation law of granite weathering crust type ion-adsorption rare earth deposits in high-altitude areas is not clear and the prospecting target area is difficult to delineate, the present invention proposes a method suitable for constructing a mineralization model of granite weathering crust type ion-adsorption rare earth ores, providing new ideas and methods for the exploration and development of granite weathering crust type ion-adsorption rare earth ores. Summary of the Invention

[0006] In order to overcome the problems in the background art, the object of the present invention is to provide a prospecting method for ion-adsorption rare earth ores based on a multi-element composite metallogenic model, which can effectively determine the key geological information for the formation of granite weathering crust-type ion-adsorption rare earth deposits, simulate the geological process of ion-type rare earth mineralization, construct a multi-element composite metallogenic model for known typical weathering crust-type ion-adsorption rare earth deposits for the first time, and provide a scientific basis for prospecting work deployment. Through its interconnections and synergistic effects, this rare earth ore prospecting technical method realizes the improvement of prospecting success rate, the accuracy of ore body positioning, the reduction of exploration cost, the enhancement of exploration accuracy, the reduction of environmental damage, and the improvement of resource utilization rate, which is of great significance for promoting the rational development and sustainable utilization of mineral resources.

[0007] To achieve the above object, the present invention is realized through the following technical solutions:

[0008] A prospecting method for ion-adsorption rare earth ores based on a multi-element composite metallogenic model, comprising the following steps:

[0009] (1) Collection and collation of existing exploration and research data of known granite weathering crust-type rare earth deposits;

[0010] (2) Analysis and determination of the basic elements for the formation of known granite weathering crust ion-adsorption rare earth deposits;

[0011] (3) Conducting field geological surveys and sample collections on known granite weathering crust ion-adsorption rare earth deposits;

[0012] (4) Analyzing and testing the samples collected in step (3), and using the analysis and test data and field geological survey data to determine each metallogenic model element;

[0013] (5) Analyzing the genesis of the deposit, establishing prospecting criteria, and constructing a multi-element composite metallogenic model for granite weathering crust-type rare earth deposits;

[0014] (6) Using the multi-element composite metallogenic model and related prospecting criteria to predict prospecting target areas; in the predicted prospecting target areas, constructing manual percussion sampling drill projects for verification, so as to delineate ore-producing areas.

[0015] More preferably, in the step (1), the collected data includes: regional geological maps, mine geological maps, remote sensing maps, geophysical and geochemical maps, the tectonic setting, metallogenic belts, natural geographical environment, topographic and geomorphic features, geological background of the survey area, tectonic evolution, and weathering crust evolution background.

[0016] More preferably, the basic elements for the formation of the known ion-adsorption rare earth deposits in granite weathering crusts include: geotectonic background, metallogenic belts and zones, geological characteristics of the deposits, metallogenic environment, metallogenic age, regional metallogenic types and alteration, ore-controlling conditions, geochemical anomalies, and sources of ore-forming materials.

[0017] More preferably, the geotectonic background includes geotectonic position, position of metallogenic belts, geophysical characteristics, characteristics of tectonic evolution, and characteristics of weathering crust evolution.

[0018] More preferably, the field geological survey includes: conducting geological section surveys in the field, judging the contact relationships of rock intrusions, recording the main and accessory minerals of granite for field identification, observing the structure and types of rocks for preliminary classification, tectonic occurrence, alteration types, and mineralization characteristics, investigating the weathering degree of granite, including the thickness of the weathered layer, stratification characteristics, and the influence of weathering on the physical and mechanical properties of rocks, and preliminarily judging the ore-controlling factors of rare earth ores in the weathering crust.

[0019] More preferably, the collected samples include the collection of chemical analysis samples, rock and mineral identification samples, isotope analysis and age determination samples.

[0020] More preferably, step (4) specifically includes: summarizing the metallogenic geological background of granite weathering crust type rare earth deposits based on field investigation and research data and various analysis and test data; determining the ore-controlling factors of rare earth mineralization through detailed research on the ore characteristics and mineralization alteration in the mining area; analyzing the mineralization characteristics and associated elements by using the main and trace element analysis data of systematic samples on the basis of the study of weathering crust alteration zoning; and determining the prospecting criteria and studying the mineralization process of ion-adsorption rare earth deposits on the basis of the ores in the deposit.

[0021] More preferably, the analysis and test data include: results of rock and mineral identification, main and trace element analysis data, isotope analysis data, composition data, and single mineral zircon dating.

[0022] More preferably, step (5) specifically includes: through step (4), extracting the key metallogenic geological elements of granite weathering crust ion-adsorption rare earth deposits, analyzing the genesis of the deposits, and compiling a metallogenic model diagram of the known granite weathering crust ion-adsorption rare earth deposits by using systematic metallogenic theory according to the obtained geological analysis data.

[0023] Advantages of the present invention:

[0024] (1) Compared with the traditional prospecting method based on a single metallogenic model, the present invention for the first time proposes a prospecting method based on a multiple composite metallogenic model for known granite weathering crust ion-adsorption rare earth deposits, comprehensively considering the interaction and superposition of various metallogenic factors and processes. Through data collection and secondary development, field geological investigation, analysis and testing, indoor comprehensive research and metallogenic model construction, the technical process is clear and highly operable, effectively defining the key geological information for the formation of ion-adsorption rare earth deposits, establishing a metallogenic model for ion-adsorption rare earth deposits, breaking through the previous simple understanding of the metallogenic mechanism, providing a new theoretical guidance for prospecting ion-adsorption rare earth ores in high-altitude areas, and helping to more comprehensively and accurately predict the distribution and enrichment law of ore bodies.

[0025] (2) The present invention organically integrates a variety of exploration technical means to form a comprehensive prospecting technology system. For example, it combines various methods such as geochemical exploration, remote sensing technology, and geological modeling. Through comprehensive analysis at multiple scales and dimensions, it can more accurately delineate the prospecting target area, improve the prospecting efficiency and success rate. This innovative integration of technical methods enables effective exploration of ion-adsorption rare earth ores in the complex geological environment of high-altitude areas.

[0026] (3) In view of the special natural conditions and geological background in high-altitude areas, the present invention specifically optimizes and improves the prospecting method. High-altitude areas usually have characteristics such as complex terrain, harsh climate, and fragile ecological environment, and traditional prospecting methods are often difficult to apply. The present invention fully considers these factors and develops exploration technologies and work processes suitable for high-altitude areas, filling the technical gap in this field and providing effective technical means for the exploration of ion-adsorption rare earth ores in high-altitude areas. Description of the Drawings

[0027] Figure 1 Schematic diagram of the weathering crust stratification characteristics of a granite weathering crust type rare earth ore in Yunnan.

[0028] Figure 2 Identification result diagram of the ore-forming parent rock thin section of a granite weathering crust type rare earth ore in Yunnan. (a) is the rock photo, (b) is the polarized light micrograph, and (c) is the TIMA mineral identification image.

[0029] Figure 3 Chondrite-normalized diagrams of rare earth elements and trace elements of the ore-forming parent rock of a granite weathering crust type rare earth ore in Yunnan. (a) is the chondrite-normalized diagram of rare earth elements, and (b) is the trace element spider diagram.

[0030] Figure 4 Zircon U-Pb age concordia diagram (a) and weighted average age diagram (b) of the ore-forming parent rock of a granite weathering crust type rare earth ore in Yunnan.

[0031] Figure 5 It is the metallogenic model diagram of a certain granite weathering crust type rare earth ore in Yunnan.

[0032] Figure 6 It is the schematic diagram of the ore body characteristics of a certain granite weathering crust type rare earth ore in Yunnan. Specific implementation manners

[0033] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0034] In the embodiments and comparative examples of the present invention, chemical reagents not described are all experimented with commercially available analytical pure ones.

[0035] Example 1

[0036] The method of the present invention is implemented in a certain granite weathering crust type ionic rare earth ore in Yunnan, and good prospecting results have been obtained. The specific analysis content and technical methods are as follows.

[0037] Step 1: Collection and collation of existing exploration and research data of a certain granite weathering crust type ionic rare earth ore in Yunnan.

[0038] Systematically collect exploration and research data of granite weathering crust type ionic rare earth ore. Analyze, summarize and re-develop the previous data, fully master the basic data of granite weathering crust type ionic rare earth ore, verify the reliability of data from different sources, and define the work that needs to be supplemented and the missing data in the previous work. Collect previous research data and reports related to regional geological maps, mine geological maps, remote sensing maps, geophysical and geochemical maps, the tectonic setting, metallogenic belts, natural geographical environment, topographic and geomorphic features, geological background of the survey area, tectonic evolution and weathering crust evolution background.

[0039] Step 2: Analyze and determine the basic elements for the formation of a certain granite weathering crust type ion-adsorbed rare earth deposit in Yunnan

[0040] Analyze and determine the basic elements for constructing the metallogenic model, including the tectonic setting, metallogenic belts, metallogenic environment, ore-bearing strata lithologic assemblage, metallogenic age, regional metallogenic type and alteration, natural geographical ore control conditions, geochemical anomalies, heavy mineral anomalies, petrology and mineralogy characteristics of the metallogenic parent rock, and the source of ore-forming materials of a certain granite weathering crust type ion-adsorbed rare earth deposit in Yunnan, and analyze the controlling factors for the formation of the deposit.

[0041] The geotectonic position of the ore deposit is located in the first-order geotectonic unit of the Gangdese-Himalayan orogenic system (Ⅸ), the second-order tectonic unit of the Gangdese-Chayu arc-basin system (Ⅸ-1), and the third-order tectonic unit of the Bangor-Tengchong magmatic arc (Ⅸ-1-3). The metallogenic province and belt belong to the Tengchong (orogenic system) metallogenic province (Ⅱ1), the Tengchong (magmatic arc) Sn-W-Be-Nb-Ta-Rb-Li-Fe-Pb-Zn-Au metallogenic belt (Mz; Kz) (Ⅲ2), and the Donghe-Mingguang (Yanshanian magmatic arc) Sn-Cu-Pb-Zn-Ag-Fe-Mn ore belt (Ⅳ4). Due to long-term sedimentation, tectonics, and magmatic evolution, a special geological background has been formed in this area. Most of the sedimentary strata in the study area are missing, and the oldest exposed strata are the Paleoproterozoic Gaoligongshan Group belonging to the crystalline basement of this block, and its lithology is mainly gray and light gray schist and gneiss. The Neogene Mangbang Formation (N2m) strata are exposed at the edge of the rock mass and are in unconformable contact with the granite. Its lithology is a set of continental sedimentary conglomerate, sandstone, and claystone intercalated with lignite seams. The Quaternary diluvial and proluvial deposits are mainly distributed in the area of the rock mass edge and mountain basins.

[0042] In addition to geological conditions such as rocks, lithology, and structures, natural geographical conditions such as climate, topography, geomorphology, and vegetation are also important ore-forming conditions for weathered crust ion-adsorbed rare earth ores. From the distribution of multiple discovered ion-adsorbed rare earth ore occurrences, they are concentrated in low-latitude areas (individually >26°) at latitudes of 22° to 26° north and altitudes generally of 1000 to 2000 m (some greater than 2100 m), mostly belonging to the subtropical-tropical monsoon climate, with medium and low mountain topography with low tectonic denudation (the elevation difference is generally 100 to 500 m, some 600 to 800 m), and well-developed valleys and vegetation. Except for the relatively high altitude and large elevation difference, the other conditions are basically the same as those of ion-adsorbed rare earth ores in areas such as southern Jiangxi and southern Guangdong in China.

[0043] Under the hot, humid, and rainy climate conditions, sufficient oxygen, groundwater, and vegetation are conducive to the strong chemical weathering of rocks. In an acidic environment rich in humic acid, rare earth minerals in the bedrock (ore-forming parent rock) dissociate into water-soluble ionic REE 3+ , and rock-forming minerals such as feldspar are oxidized and altered to form a large amount of clay minerals mainly composed of kaolinite; REE 3+During the processes of atmospheric precipitation and groundwater infiltration, due to the change in acidity (pH value), continuous precipitation is adsorbed by clay minerals and finally accumulates to form ore. Due to certain differences in the chemical properties of each rare earth element, their migration ability or the ability to be adsorbed by clay minerals is different, resulting in different enrichment horizons in the weathered crust. Cerium (Ce) is separated from other light rare earth elements earliest and is deposited in the upper part of the completely weathered layer or the lower part of the sub-clay layer, while other light rare earth elements are enriched in the upper-middle part of the completely weathered layer below it; due to the larger atomic number of heavy rare earth elements, their downward migration speed is faster than that of light rare earth elements, so they are mostly enriched in the middle-lower part of the completely weathered layer.

[0044] Tectonic conditions also have an obvious controlling effect on the formation of rare earth deposits. Deep major faults directly control the formation and development of several major tectonic magmatic belts and deep metamorphic belts in Yunnan, and the rare earth metallogenic belts (and related anomaly belts) overlap with the deep metamorphic rock belts and tectonic-magmatic rock belts in spatial distribution.

[0045] Regional folded anticlines and the associated compressional shear fracture zones often control the distribution of ore-bearing intrusive rock bodies. The primary fractures at the top and edge of the rock bodies are the development sites of the rock body alteration zones, thus directly controlling the occurrence of altered granite-type rare earth mineralization; at the same time, the metasomatism occurring along the fractures further enriches the rare earth elements in the ore-forming parent rock of the weathered crust ion-adsorption type rare earth ore or changes the rare earth element distribution pattern of it, such as the superposition of heavy rare earth mineralization on the light rare earth enrichment type ore-forming parent rock.

[0046] Tectonic movements have an obvious restrictive effect on the formation and preservation of the weathered crust. Structures such as fractures, fissures, and joints developed in the bedrock (ore-forming parent rock) destroy the rock structure, facilitating the infiltration and drainage of atmospheric precipitation and groundwater, forming a good oxidation environment, which is conducive to the weathering of rocks and the dissociation of rare earth elements; a relatively stable tectonic environment can form thick and large weathered crusts and preserve them intact.

[0047] Step 3: Conduct field geological surveys and sample collections on a granite weathered crust type ion-adsorption rare earth deposit in Yunnan.

[0048] Conduct field geological surveys on a granite weathered crust type ion-adsorption rare earth deposit in Yunnan, and carry out regional metallogenic geological background surveys. The strata in the mining area mainly expose the Proterozoic Gaoligongshan Group (Pt1GL.), the Neogene Mangbang Formation (N2m), the Quaternary strata (Q), etc. Controlled by regional faults, they are generally distributed in a north-southwest-east direction. The metamorphic rocks of the Lower Proterozoic Gaoligongshan Group are mainly schist, gneiss, and granulite; the Cenozoic sediments are scattered. The tectonic activities in the area are intense. A small number of anticline and syncline structural features can be seen in the Paleoproterozoic Gaoligongshan Group in the area, mostly wide and gentle folds formed by the early schistose rock layers due to later orogenic movements.

[0049] The ionic rare earth ore bodies in the area are mainly hosted in the weathered crust of the granite rock mass. The rock mass occurs as a batholith and is distributed in a belt along the northeast-southwest direction. The outcropping area of the rock mass is relatively large, about 160 km 2 . The lithologies exposed in the rock mass mainly include porphyritic medium-coarse-grained biotite monzogranite, gneissic granite, quartz diorite and a small amount of mylonite. Among them, porphyritic medium-coarse-grained biotite monzogranite is the main one, and the total rare earth content of the rock is generally high. Alteration characteristics: The wall rock alteration in the area mainly includes argillization, kaolinization, sericitization, potassic alteration, limonitization and chloritization, etc. Argillization, kaolinization and sericitization are common and occur in each unit of Triassic biotite monzogranite, which are important signs for the formation of ion-adsorption type rare earth ore in the weathered crust. Chloritization and limonitization are mostly distributed along the NE-trending fault structural fissures.

[0050] The rare earth ore-bearing weathered crust formed by weathering has gradually transitional vertical stratification characteristics. According to the comprehensive characteristics such as color, structure, texture and dissociation of mineral components, and newly formed minerals, the completely preserved rare earth ore-bearing weathered crust is divided into humus layer, clay layer, completely weathered layer, semi-weathered layer ( Figure 1 ). Below the weathered crust is the weakly weathered layer and bedrock of granite. The characteristics and thickness changes of each layer of the weathered crust are as follows:

[0051] 1. Humus soil layer: mainly grayish-brown humus soil. It is gray, grayish-brown, with extremely loose structure, well-developed plant roots inside, and relatively high organic matter content, with a thickness of 0 - 0.50 m.

[0052] 2. Clay layer: brownish-red and yellowish-brown clay. It is brownish-red, yellowish-brown, grayish-yellow, the original rock structure has completely disappeared, the soil structure is compact, the permeability is poor, the viscosity is strong, and it has a slippery feeling when rubbed by hand. The mineral composition is mainly clay minerals, with a small amount of quartz. This layer shows a gradual change relationship with the underlying completely weathered layer, and the boundary is blurred. The thickness is 0.00 - 4.20 m.

[0053] 3. Completely weathered layer: mainly sandy clay and sandy clay. It is light yellow, light flesh-red, variegated (light flesh-red mixed with grayish-yellow), light grayish-white, etc. The original rock structure has basically disappeared, the mineral composition is mainly clay minerals, with less quartz and biotite. The parent rock is granite-like rock, and the clay minerals are the alteration products of feldspar, and quartz and biotite are residual minerals. The soil structure is slightly dense, the porosity is medium, it can be rolled into a strip when rubbed by hand, and it has a slippery feeling. The thickness is 2.00 - 26.6 m. This layer is the main ore-bearing horizon and an important target horizon for rare earth ore deposit exploration. The boundary between this layer and the underlying semi-weathered layer is not clear, showing a gradual transition relationship, marked by the appearance of weathered plagioclase remains.

[0054] 4. Semi-weathered layer: It is gray, light grayish-white clayey sandy soil and sandy soil. The thickness is generally 3 - 20 m. The original rock structure is basically retained, with medium-fine (coarse) grain structure and massive structure. The mineral composition is mainly feldspar, followed by quartz and less biotite. Most feldspars have been altered into clay minerals, quartz is in anhedral granular form, and biotite is in flaky form. The soil structure is loose, with medium porosity, brittle, and has an obvious sandy feeling when rubbed by hand and cannot form strips. The bottom of this layer has not been seen. It shows a gradual transition relationship with the underlying bedrock.

[0055] 5. Bedrock: The lithology is mainly medium-coarse grained porphyritic biotite monzogranite: medium-coarse grained porphyritic structure, massive structure, the rock is fresh and unweathered, controlled by regional tectonics, and locally fragmented.

[0056] Based on the basic elements of mineralization of a granite weathering crust-type ion-adsorption rare earth deposit in Yunnan determined by the analysis in Step 2, including the geotectonic background, metallogenic belts, metallogenic environment, ore-hosting stratigraphic rock formations, metallogenic age, regional metallogenic types and alteration, natural geographical ore-controlling conditions, geochemical anomalies, weathering crust stratification characteristics, etc., petrological and mineralogical characteristics of the ore-forming parent rock, and the source of ore-forming materials. Combining the field investigation results, mineralized and altered samples were systematically collected, including chemical analysis samples, rock and mineral identification samples, isotope analysis and age determination samples. The field investigation and sample collection work refer to the standard of "Specifications for Mineral Geological Exploration - Rare Earth" (DZ / T 0204 - 2022).

[0057] Step 4: Use the analytical test data and field investigation data to define each element of the metallogenic model.

[0058] The samples collected in Step 3 were respectively analyzed and tested, and analytical test data were obtained through a professional geological laboratory, including rock and mineral identification results, major and trace element analysis data, isotope analysis data, composition data, and single mineral zircon dating.

[0059] Petrological and mineralogical characteristics of the ore-forming parent rock: To explore the relationship between the genesis of granite parent rock and the initial enrichment mechanism of rare earth elements, 23 fresh samples were collected from the rock mass. The thin section identification results are as follows:

[0060] Structure and texture: Porphyritic texture, metasomatic porphyritic, metasomatic residue, island, clean edge and other textures ( Figure 2 ).

[0061] The rock is composed of matrix and vein. The matrix is porphyritic granite with porphyritic texture. The phenocrysts are plagioclase, quartz, orthoclase, biotite, etc., and the grain size is generally > 1 - 5 mm. The matrix consists of fine-grained (< 1 mm) plagioclase, quartz, orthoclase, biotite, etc., with phaneritic granitic texture. Affected by marginal migmatization and the injection of late alkali fluids associated with the rock mass, plagioclase and quartz are metasomatized to form potassium feldspar porphyroblasts, but the metasomatism is not complete. In the porphyroblasts, metasomatic residue, clean edge, striped and other textures often appear.

[0062] Mineral composition:

[0063] Matrix: It is porphyritic biotite granite, and the phenocrysts are plagioclase, quartz, biotite, etc. The matrix consists of plagioclase, quartz, orthoclase, and biotite less than 1 mm in size, with a porphyritic fine-grained granite structure. The content accounts for 60±, and the mineral characteristics are as follows:

[0064] Plagioclase: Colorless, with an unclean surface, euhedral to subhedral tabular and fractured. It has albite twins and zoning under orthogonal polarization, and occurs as phenocrysts and in the matrix. Most of it has been sericitized and argillized.

[0065] Quartz: Colorless, subhedral to anhedral and fractured, with low positive relief and first-order pale yellow interference color under orthogonal polarization. It occurs as phenocrysts and in the matrix.

[0066] Orthoclase: Colorless, subhedral to anhedral, fractured. It has a striation structure under orthogonal polarization and mostly occurs in the matrix. The contents of plagioclase, quartz, and orthoclase account for about 45%.

[0067] Biotite: Brown, flaky, with significant pleochroism, dark brown to light yellowish brown, medium positive relief, with a set of extremely perfect cleavage, brown abnormal interference color under orthogonal polarization, parallel extinction. A small amount occurs as phenocrysts, and most occur in the matrix, with a content of (10 - 15%).

[0068] The phenocryst is potassium feldspar: mostly occurs as porphyroblasts, wide tabular, with well-developed grid twins and striation structure under orthogonal polarization. The content accounts for about 40%.

[0069] During the later supergene process, the rock mass has weathered into a weathered layer: syenogranite is light gray, showing a porphyritic structure ( Figure 2 (a)), mainly composed of quartz (20 - 23%), potassium feldspar (45 - 50%), plagioclase (20 - 22%), and biotite (3 - 5%) (see Figure 2 (b)). The size of these minerals is 1 - 10 mm. The rare earth-bearing accessory minerals include monazite, xenotime, apatite, zircon, allanite, and ilmenite. According to the images of the Tescan Integrated Mineral Analyzer (TIMA), most of their sizes are less than 1 mm ( Figure 2 (c)). The syenogranite has slight alteration, and plagioclase and biotite are partially altered to sericite and sericite respectively.

[0070] Ore characteristics:

[0071] The ore shows a sandy and clay-like structure, mainly composed of clay and quartz, followed by a small amount of feldspar, chlorite, biotite, etc.; the rare earth minerals include thorium-rich monazite, allanite, and an unnamed rare earth mineral rich in manganese and lead. Other heavy minerals include magnetite, ilmenite, limonite, garnet, zircon, galena, columbite, etc.

[0072] Geochemical characteristics of rocks:

[0073] Analysis data show that the ore-forming parent rock, biotite monzogranite, has relatively uniform rock chemical composition. Its SiO2 content varies slightly, ranging from 66.42% to 70.85%, Al2O3 content from 14.33% to 15.30%, MgO content is relatively low, from 0.53% to 1.2%, CaO content from 0.81% to 3.01%, K2O content from 4.43% to 6.35%, Na2O from 1.67% to 2.85%, K2O / Na2O = 1.55 - 3.92, the Rittmann index σ of the rock is 2.09 - 2.95, and the aluminum saturation index is A / CNK = 0.97 - 1.35 (average 1.08). It has the characteristics of low S, high K and Ca, and belongs to high-K calc-alkaline meta-aluminous to peraluminous granite.

[0074] The total rare earth content of the rock is relatively high (265.40×10 -6 ~706.8×10 -6 ), which is a prerequisite for the formation of ion-adsorption rare earth ore related to granite. The characteristics of rare earth elements show that (La / Sm) N = 4.34 - 7.02 (average 5.46), (Gd / Yb) N = 1.18 - 3.86 (average 2.35), indicating that the fractionation of light rare earth elements is stronger than that of heavy rare earth elements. In the chondrite-normalized distribution pattern of rare earth elements ( Figure 3 (a)), the rare earth elements generally show a right-tilted distribution pattern with light rare earth enrichment and heavy rare earth depletion. The weak negative Eu anomaly may indicate that the rare earth element distribution curves of the samples have great similarity, suggesting that they are likely to be a homologous magma sequence, and with the increase of magma differentiation degree and alkalinity degree, the content of heavy rare earths decreases slightly. The rock δEu = 0.32 - 0.45 (average 0.40), indicating that the magma has experienced strong plagioclase separation (molten residue or fractional crystallization) during diagenesis. δCe = 0.81 - 0.94 (average 0.90), and Ce shows a very weak negative anomaly, indicating that the rock is mainly formed in a reducing environment. Compared with the Vogt values of granite, the contents of Zr, Rb, Nb, U, and Pb in the trace element content of the rock mass are relatively high, and the contents of the remaining elements are lower than or close to the Vogt values. After the rock is normalized by mid-ocean ridge granite ( Figure 3 (b)), the trace element ratios show strong depletion of K2O, Ba, and Hf, showing extreme depletion of Ba and no obvious negative anomalies of Nb and Hf, which may be related to strong in-situ crystallization fractionation.

[0075] Determination of the emplacement age of the rock mass and analysis of the tectonic environment

[0076] Analysis was carried out on zircon in rock mass samples, and common lead correction was performed on all measuring points. From the U-Pb age concordia diagram and weighted average age diagram of the rock ( Figure 4 ), it can be concluded that the age data basically fall on the concordia line. The 206Pb / 238U concordant age of the rock mass is (50.25±0.40) Ma (MSWD = 1.18), and the weighted average age is (50.29±0.44) Ma (MSWD = 1.14). The two are very consistent within the error range. It can be seen that the concordant age of the ore-forming rock mass is relatively consistent with the weighted average age, indicating that the magmatic crystallization age of the rock mass is (50.25±0.40) Ma, which is in the Eocene of the Paleogene. After the emplacement of the rock mass, through the complex crustal tectonic movements in the Tertiary and Quaternary, the rock mass has suffered strong tectonic actions and regional uplift-denudation actions.

[0077] Based on the determination of the petro-geochemical genetic type and combined with the accurate zircon U-Pb dating results, it can be known that the magma of the rock mass crystallized in the Eocene (48.0 - 50.8 Ma). This magmatic activity is mainly related to the post-collision environment, and at the same time, it is contaminated or inherited the characteristics of the early syn-collision environment. It is comprehensively judged that the rock mass was formed after the end of the main collision period, under the background of regional crustal stress relaxation and extensional tectonics.

[0078] Based on the field investigation results and various analysis and test data, the following is summarized: The biotite monzogranite in the Eocene of the Paleogene is the ore-forming parent rock of the ion-adsorption type rare earth deposit in this area. The humid and hot climate of the deposit is conducive to the weathering of granite, and the relatively flat middle mountain area is conducive to the preservation of the thick granite weathering layer. The biotite monzogranite is divided into humus soil layer, clay layer, completely weathered layer, semi-weathered layer and fresh bedrock from the surface to the bedrock according to the weathering degree, and the pH value of the weathering crust is between 5 and 7. Among them, the completely weathered layer is the main ore-bearing horizon. The elemental geochemical characteristics of the weathering crust show that rare earth elements are enriched and fractionated after weathering, and the rare earth mineralization is mainly dominated by light rare earth. In addition, the thickness of the ore body is significantly positively correlated with the ore grade, and both are strictly controlled by the terrain. Gentle mountain tops, gentle ridges and low gentle hills are conducive to the accumulation of the ore body, and the terrain slope is generally <40°.

[0079] Step 5: Conduct comprehensive research to construct the metallogenic model of a granite weathering crust type ion-adsorption type rare earth deposit in Yunnan.

[0080] Based on the above research results and data analysis, simulate and analyze the metallogenic process of a granite weathering crust type ion-adsorption type rare earth deposit in Yunnan, extract the key geological elements of ion-type rare earth mineralization, analyze the genesis of the deposit, establish ore prospecting indicators, conduct comprehensive research and construct the metallogenic model of granite weathering crust type rare earth deposit. Compiled the metallogenic model diagram of a granite weathering crust type ion-adsorption type rare earth deposit in Yunnan, as Figure 5 shown.

[0081] Genesis of the deposit:

[0082] The formation of the ion-adsorption rare earth deposit in the weathered crust of granite in a certain place in Yunnan is affected by various factors, including ore-bearing parent rocks, climate conditions, geomorphic features, supergene leaching, and the ion-adsorption enrichment process. The biotite monzonite granite in the Paleogene period is the main source of ore-forming materials. The content of rare earth elements in the parent rock has an important impact on the formation of the deposit. The higher the content, the more conducive it is to the formation of ion-adsorption deposits. In a humid and hot climate environment, the original rocks rich in rare earths are gradually weathered and decomposed. Among them, on the one hand, rock-forming minerals such as feldspar will secondarily change into clay minerals such as kaolinite, and these clay minerals act as the adsorption carriers of rare earths; on the other hand, the rare earth elements released during the decomposition of minerals such as feldspar provide the material basis for the adsorption of clay minerals. The upper layer of the weathered crust with lush surface vegetation and rich organic acid content provides good environmental conditions for the migration and enrichment of rare earth elements. Under the condition of weak acidity on the surface, rare earth elements can transform into solution form, and then migrate and penetrate with the flow of surface runoff and surface water.

[0083] Prospecting criteria:

[0084] With better weathering degree, a weathered crust rich in clayification and kaolinization is formed, which is convenient for the secondary enrichment of rare earth ions. The main prospecting criteria are as follows:

[0085] 1. Parent rock criterion: The lithology of the ore-forming parent rock is Paleogene biotite monzonite granite, which has a high background value of rare earths.

[0086] 2. Tectonic criterion: Both sides of the faults with multi-stage activities and the intersection parts of tectonic fracture zones play a certain role in the migration and enrichment of rare earths in the weathered crust, and are favorable areas for prospecting. The NE-trending tectonic fractures in the area make rare earth elements more enriched.

[0087] 3. Geomorphic criterion: The low-middle mountain geomorphic area (altitude 1000 - 2000m, relative elevation difference < 500m) is conducive to the formation of ion-adsorption rare earth deposits in the weathered crust of granite. In the area, the altitude is 1020 - 1680m, and the low-middle mountain geomorphic area with medium-shallow denudation is the most developed. The rare earth ores are best preserved in relatively flat areas, and the terrain slope is generally < 40°.

[0088] 4. Geochemical criterion: The geochemical anomalies of rare earth elements are distributed on the weathered crust of granite, and the anomaly element combination is La, Y, Nb, U, Th, and the La element anomaly is the main one.

[0089] 5. Weathered crust criterion: The weathered crust is widely distributed and has a high weathering degree. The weathered crust is divided into humus layer, clay layer, completely weathered layer, semi-weathered layer, and bedrock from top to bottom in the vertical section. The rare earth ore bodies are mainly hosted in the completely weathered layer of the weathered crust.

[0090] 6. Heavy placer anomaly indicator: The heavy placer anomaly of rare earth minerals composed of mineral assemblages such as monazite, xenotime, zircon, rutile, etc. is an ideal prospecting indicator.

[0091] Mineralization elements:

[0092] Systematically studied the mineralization characteristics and laws of a weathered crust type ion-adsorption rare earth deposit in granite in Yunnan, summarized its multiple composite mineralization elements (Table 1), analyzed the importance of each element, and carried out ranking, and established a multiple composite mineralization model for typical rare earth ore deposits.

[0093] Table 1 Mineralization elements of typical ore deposits

[0094]

[0095]

[0096] The mineralization model diagram ( Figure 5 ) was compiled based on the research in steps 1 - 4, identifying each mineralization element of the weathered crust type ion-adsorption rare earth deposit in granite. The general mineralization characteristics of a weathered crust type ion-adsorption rare earth deposit in granite in Yunnan are as follows: Secondary fault structures are developed in the working area, belonging to the superposition and compound area of linear and planar weathering. The joints arranged radially inside the entire granite rock mass and later microfractures are very developed. Under the combined action of many factors such as the weathering of the original rock by rainwater, groundwater, microorganisms, and topography and geomorphology, rare earth elements are dissociated from the lattice of rock-forming minerals under the action of acidic solutions, and at the same time, clay minerals such as kaolinite and illite are formed. The dissociated rare earth ions and clay minerals migrate downward with shallow surface water. At a certain depth, with the gradual aggregation of clay minerals and the gradual increase of the pH value, the rare earth ions are captured and adsorbed by the clay minerals with higher adsorption capacity in the medium of weak acidity, and the rare earth elements have a preliminary enrichment. During the weathering process, rare earth elements are continuously enriched. The greater the weathering intensity, the greater the depth of the weathered crust, and the more rare earth elements brought from the upper part. Finally, the enrichment in the completely weathered layer can be several times higher than that in the bedrock in terms of rare earth elements.

[0097] This mineralization model diagram comprehensively reflects the mineralization process of a weathered crust type ion-adsorption rare earth deposit in granite in Yunnan and has guiding significance for prospecting and prediction of this type of rare earth resources.

[0098] Step 5: Utilize the multiple composite mineralization model and the summarized prospecting indicators to carry out prediction of prospecting target areas and conduct verification of prospecting engineering.

[0099] In the field, prospecting signs such as the mother rock, structure, topography, geochemical anomalies, weathered crust stratification characteristics, and heavy sand anomalies are searched for. These prospecting signs are plotted on a geological map, and samples are collected on the surface for testing and analysis to determine whether the rare earth element content meets the ore standard. The areas where these prospecting signs are concentrated and the areas with mineralization shows on the surface are delineated as prospecting target areas.

[0100] Within the prospecting target areas, according to the requirements of the solid mineral exploration specifications, drilling projects are arranged at the specified exploration lines and engineering spacings to verify the ore-bearing property in the deep underground ( Figure 6 ). By constructing boreholes ZK4, ZK5, and ZK6, rare earth ore bodies were revealed, achieving a breakthrough in prospecting. One rare earth ore deposit was submitted, and the potential rare earth resource scale can reach large scale.

[0101] The present invention is applicable to the basic research of ionic resources in our country and can provide the most direct and accurate information for the development and utilization of ionic rare earth resources in our country.

[0102] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A prospecting method for ionic-adsorption type rare earth ore based on a multivariate composite metallogenic model, characterized in that: It includes the following steps: (1) Collection and collation of existing exploration and research data of granite weathering crust type rare earth deposits; (2) Analysis and determination of the basic elements of ore formation in known granite weathering crust ion-adsorption type rare earth deposits; (3) Field geological survey and sample collection of known granite weathering crust ion-adsorption type rare earth deposits; (4) Analyze and test the samples collected in step (3), and use the analysis and test data and field geological survey data to define the elements of each ore formation model; (5) Analyze the genesis of the deposit, establish prospecting criteria, and construct a multiple composite ore formation model for granite weathering crust type rare earth deposits; (6) Use the multiple composite ore formation model and related prospecting criteria to predict prospecting target areas; within the predicted prospecting target areas, construct manual percussion sampling drill projects for verification, so as to delineate ore fields; In step (1), the collected data includes: regional geological maps, mine geological maps, remote sensing maps, geophysical and geochemical maps, the tectonic setting, metallogenic belts, natural geographical environment, topographic and geomorphic features, geological background of the investigation area, tectonic evolution, and weathering crust evolution background.

2. The prospecting method for ion-adsorption type rare earth ore based on the multi-element composite metallogenic model according to claim 1, wherein: The basic elements of ore formation in known granite weathering crust ion-adsorption type rare earth deposits include: tectonic background, metallogenic belts, geological characteristics of the deposit, ore-forming environment, ore-forming age, regional ore-forming types and alteration, ore-controlling conditions, geochemical anomalies, and ore-forming material sources.

3. The prospecting method for ion-adsorption type rare earth ore based on the multiple composite metallogenic model according to claim 2, characterized in that: The tectonic background includes tectonic location, position of metallogenic belts, geophysical characteristics, tectonic evolution characteristics, and weathering crust evolution characteristics.

4. The prospecting method for ion-adsorption type rare earth ore based on the multivariate composite metallogenic model according to claim 1, wherein: The field geological survey includes: measuring geological profiles in the field, judging the contact relationship of rock intrusions, recording the main minerals and accessory minerals of granite for field identification, observing the structure and type of rocks for preliminary classification, tectonic occurrence, alteration types, and mineralization characteristics, investigating the weathering degree of granite, including the thickness of the weathered layer, stratification characteristics, and the impact of weathering on the physical and mechanical properties of rocks, and preliminarily judging the ore-controlling factors of rare earth ores in the weathering crust.

5. The prospecting method for ionic adsorption rare earth ore based on the multiple composite metallogenic model according to claim 1, wherein: In step (3), the collected samples include the collection of chemical analysis samples, petrographic identification samples, isotope analysis and age determination samples.

6. The prospecting method for ion-adsorption rare earth ore based on the multivariate composite metallogenic model according to claim 1, characterized in that: Step (4) specifically includes: summarizing the ore-forming geological background of granite weathering crust type rare earth deposits based on field investigation and research data and various analysis and test data; defining the ore-controlling factors of rare earth mineralization through detailed research on ore characteristics and mineralization alteration in the mining area; analyzing mineralization characteristics and associated element analysis based on the main and trace element analysis data of systematic samples on the basis of the study of weathering crust alteration zoning; determining prospecting criteria and studying the mineralization process of ion-adsorption type rare earth deposits based on the ores of the deposit.

7. The prospecting method for ion-adsorption type rare earth ore based on the multiple composite metallogenic model according to claim 1, wherein: The analysis and test data includes: petrographic identification results, main and trace element analysis data, isotope analysis data, composition data, and single mineral zircon dating.

8. The prospecting method for ionic-adsorption rare earth ore based on the multiple composite metallogenic model according to claim 1, wherein: Step (5) specifically includes: extracting the key ore-forming geological elements of granite weathering crust ion-adsorption type rare earth deposits, analyzing the genesis of the deposit, and compiling an ore formation model map of known granite weathering crust ion-adsorption type rare earth deposits according to the obtained geological analysis data and applying systematic ore formation theory.

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