Method for discriminating composite mineralization of magma hydrothermal system

Abstract

The invention relates to the technical field of ore deposit geological exploration, in particular to a method for judging the composite mineralization of a magma hydrothermal system, which comprises the following steps: 1) field geological survey and total factor sampling; 2) screening characteristic minerals and identifying lithofacies; (3) feature mineral mineralization generation division and cause preliminary exploration; 4) in-situ microcell geochemical analysis; (5) geochemically verifying the formation cause of the ore deposit; 6) analyzing an element zoning mode; and 7) reconstructing the composite mineralization process. According to the method, lithofacies discrimination, mineral geochemical analysis and mineral internal element spatial distribution (mapping / plane scanning) are organically combined, a multi-scale and multi-criterion synergistic composite mineralization recognition system is constructed, the magma hydrothermal system mineralization type can be effectively recognized, and then the composite mineralization process is reconstructed. The problem of lithofacies and geochemical splitting in traditional analysis is solved, and key technical support is provided for complex magma hydrothermal cause deposit analysis and deep prospecting prediction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ore deposit geological exploration, and particularly relates to a discrimination method of composite mineralization of a magmatic hydrothermal system. BACKGROUND

[0002] The magmatic hydrothermal type polymetallic deposit is one of the most important metal mineral resources in the world, and is the main supply type of global key metal resources such as copper, gold, lead and zinc. The metallogenic essence of the magmatic hydrothermal type polymetallic deposit is composite mineralization, that is, the spatiotemporal dynamic coupling of magmatic activity, tectonic activation, multi-stage fluid migration and water-rock reaction processes. The prospecting and exploration of the magmatic hydrothermal type polymetallic deposit involves multiple disciplines such as geology and geochemistry. Although the magmatic hydrothermal type polymetallic deposit is widely distributed in plate margins and intracontinental orogenic belts, the deep prospecting of the magmatic hydrothermal type polymetallic deposit always faces core scientific problems: the traditional exploration mode relies on petrographic-geochemical fragmented analysis, and it is difficult to finely dissect the multi-stage superimposed mineralization process. The prominent problems are: ① the spatial and temporal coupling of multi-stage mineralization events leads to the complication of mineral assemblages, and the mineralization stages are not clear; ② the geochemical data, especially the trace element discrimination, do not fully combine the characteristics of mineral microzones, resulting in the invalidation of trace element criteria; ③ the traditional petrographic (mineralogical) analysis method and modern geochemical testing means are not systematically integrated, resulting in scattered analysis methods. The above problems limit the research on the composite mineralization of the magmatic hydrothermal system to some extent, and seriously restrict the deep prospecting and resource increase of the magmatic hydrothermal type polymetallic deposit in China.

[0003] Therefore, an efficient discrimination method combining petrography and geochemistry is urgently needed to determine the key markers of the composite mineralization of the magmatic hydrothermal type deposit. SUMMARY

[0004] The purpose of the present application is to provide a discrimination method of the composite mineralization of the magmatic hydrothermal system, which determines the characteristic minerals of the magmatic hydrothermal deposit, comprehensively analyzes the petrographic, geochemical and element zoning characteristics of the characteristic minerals, reveals the genesis and multi-stage superimposed mineralization process of the magmatic hydrothermal type deposit, and determines the composite mineralization of the magmatic hydrothermal system.

[0005] In order to achieve the above technical purposes and achieve the above technical effects, the present application is realized by the following technical scheme:

[0006] A discrimination method of the composite mineralization of the magmatic hydrothermal system, comprising the following steps:

[0007] S1: Field geological survey and sample collection: Based on the regional geological map and research report of the target ore (bed), carry out field geological survey, find out the stratum, structure, magmatic rock and ore body information of magmatic hydrothermal deposit, including ore-bearing stratum, ore-hosting structure distribution, ore body shape and contact relationship with surrounding rock; record the location of mineralized outcrop and mark on the regional geological map, systematically collect ore body, wall rock, magmatic rock, sedimentary rock and metamorphic rock samples covering all geological units;

[0008] S2: Characteristic mineral screening and petrographic identification: Through the observation of macroscopic and microscopic composition of rocks (minerals), the characteristic minerals common to each geological unit are screened. The characteristic minerals need to meet the following conditions: widely distributed in the ore-forming geological body, can represent the ore-forming stage, and adapt to different ore-forming environments; make polished sections and thin sections of the screened characteristic minerals, identify their color, structure, structure and paragenetic association using optical microscope and electron microscope, and record the petrographic characteristics; if there are zoning characteristics, take backscattered electron images (BSE) for further analysis;

[0009] S3: Division of ore-forming generations and preliminary exploration of genesis: According to the macroscopic geological characteristics (mineral spatial distribution characteristics, mineral paragenetic association, relative content of minerals, contact and penetration relationship, color, structure) and microscopic petrographic characteristics (mineral color structure, zoning structure, paragenetic sequence) of characteristic minerals, the ore-forming generations are divided; combined with the stratum age, zircon U-Pb age and granite Lu-Hf isotope analysis data of the characteristic minerals, the ore-forming age is determined, and the genesis type of the deposit is preliminarily judged;

[0010] S4: In-situ micro-area geochemical analysis: Use electron probe to analyze the major elements (SiO2, Al2O3, FeO, Fe2O3, MgO, Na2O, TiO2) of the characteristic minerals, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to test trace and rare earth elements (As, Co, Ni, Se, Cd), and obtain the distribution images of Fe, Cu, Pb, Zn, Ag, Au elements in the minerals through area scanning technology;

[0011] S5: Verification of deposit genesis: Based on the content of major, trace and rare earth elements of characteristic minerals, use Geokit and Origin software to draw mineral geochemical discrimination diagrams to verify the ore-forming environment and genesis type;

[0012] S6: Analysis of element zoning pattern: According to the element distribution Mapping diagram obtained by area scanning, combined with the results of ore-forming generation division and genesis verification, analyze the element zoning pattern and microstructure characteristics in the minerals, and judge the superimposed type of ore-forming process and the mode of ore precipitation;

[0013] S7: Reconstructing the composite ore-forming process: Based on the regional magmatic activity and tectonic evolution history, the petrographic, geochemical and element zoning analysis results of the above steps are integrated to reconstruct the composite ore-forming process of the magmatic hydrothermal system.

[0014] Further, taking pyrite as an example, the ore-forming generation division in step S3 is based on: macroscopically, Py I is distributed in a layered / similar layered manner, and Py II penetrates the Py I ore body; microscopically, Py I has a raspberry structure, and Py II has a replacement residual structure.

[0015] The element zoning pattern analysis in step S6 is specifically: the Fe content of the core of Py I pyrite is > 99.35%, the edge is rich in Mn 0.5-1.2wt%, and Ca 0.3-0.8wt%, and presents a zonal rhythmic structure, indicating a sedimentary environment of exhalation;

[0016] Py II pyrite is rich in Cu and As in the fissure, indicating magmatic hydrothermal superimposition;

[0017] The ore-forming superimposition type is exhalative sedimentation-magmatic hydrothermal type, which is based on the fact that Py II penetrates Py I and the element anomaly area matches the petrographic generation.

[0018] The beneficial effects of the present application are:

[0019] The present application combines petrographic discrimination, mineral geochemical analysis and mineral internal element spatial distribution (mapping / surface scanning) to construct a multi-scale, multi-criterion collaborative composite ore-forming recognition system. First, based on field investigation and sample systematic collection, through petrographic observation and thin section microscopic analysis of different geological units and multiple types of minerals, the spatial distribution, macro-micro structure, paragenetic association and interpenetration relationship of characteristic minerals are determined, and the mineral generation and ore-forming stage are revealed from the macro and micro levels. Then, for the selected characteristic minerals, the in-situ micro-geochemical technology is used to obtain the major, trace and rare earth element contents, and the element surface scanning is combined to realize high-precision analysis of the element zoning characteristics in the mineral. The coupling and superimposition characteristics of multiple periods and different properties of mineralization events in the same ore body are effectively identified, which not only breaks through the limitation of traditional single criterion that is difficult to determine the type of composite ore-forming, but also systematically reveals the ore-forming nature of the multi-period superimposition of the magmatic hydrothermal system, providing a solid foundation for fine genetic discrimination and ore deposit process reconstruction.

[0020] The present application organically integrates mainstream in-situ micro-area testing technology and systematic petrographic analysis, takes mineral generation division as the main line, takes different generations and different structures of characteristic minerals as the objects of geochemical analysis, and significantly improves the identification ability of multi-period ore-forming markers. First, the morphology, structure and relationship between the characteristic minerals and the associated minerals are observed in detail by optical and electron microscopy, and the ore-forming generations are divided; then, the major and trace elements of characteristic minerals at different time and space and different ore-forming stages are obtained by using in-situ testing methods such as electron probe and laser ablation. The element zoning structure in the mineral and the enrichment / deficiency mode changing with generations can directly indicate the ore-forming fluid evolution path and the superimposition and replacement process of different ore-forming events. The aggregation of certain elements along a specific structure in the mineral can reflect the superimposition and modification of the late hydrothermal activity, and is a key physical and chemical marker of composite mineralization. Therefore, the present application provides a direct and reliable evidence source for the quantitative identification of multi-period ore-forming events and the division of deposit genetic types through the coupling of multi-layer information from macrostructure, microcomponent to element zoning.

[0021] The present application breaks through the limitation of simple static analysis and realizes the dynamic reconstruction of composite mineralization by highly fusing regional geological evolution history with ore body geology, mineralogy, geochemistry and element distribution evidence through the systematic design of seven-step progressive standard workflow (field investigation-mineral screening-generation division-in-situ testing-genetic verification-zoning analysis-process reconstruction). The present application organically connects the ore-forming process of fluids of different periods and different sources and the coupling and transformation process by detailed investigation of regional strata, structure and magmatic activity history, combined with geochemical discrimination of characteristic minerals of each ore-forming stage and element zoning mode analysis. The time and space relationship between the generations of characteristic minerals and regional tectonic-magmatic events is analyzed to realize the modeling of the time and space superposition mode of the ore-forming environment. The evolution path of complex ore deposit composite mineralization can be quantitatively restored, the role and contribution of different ore-forming events in the spatial distribution of ore bodies and the precipitation of ore are clarified, the scientificity and predictability of deep prospecting model are greatly improved, and theoretical and technical support is provided for subsequent resource increase and exploration deployment. The present application provides a technical paradigm that can be used for reference and promotion for the genetic analysis and deep prospecting prediction of similar ore-forming systems of multi-region and multi-type deposits.

[0022] Of course, it is not necessary for any product implementing the present application to achieve all the advantages mentioned above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed for the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0024] Figure 1 Figure 1 is a flowchart of a method for identifying composite ore-forming of a magmatic hydrothermal system according to the present application;

[0025] Figure 2 Figure 2 is a schematic diagram of a field sampling location according to an embodiment; 1 - Quaternary strata; 2 - Permian strata; 3 - Carboniferous strata; 4 - Early Devonian Posongchong Formation; 5 - Early Devonian Pogujie Formation; 6 - Early Devonian Bajiaqing Formation; 7 - Middle Devonian Gumu Formation; 8 - Middle Devonian Donggangling Formation; 9 - Early Devonian Gedang Formation; 10 - Middle Cambrian Longha Formation; 11 - Middle Cambrian Tianpeng Formation; 12 - Middle Cambrian Dajiakou Formation; 13 - Early Cambrian Dazhai Formation; 14 - Early Cambrian Chongzhuang Formation; 15 - diabase; 16 - granite body; 17 - fault, fracture; 18 - sampling location; 19 - geological boundary;

[0026] Figure 3 Figure 3 is a schematic diagram of petrographic classification of a hand specimen, polished section and thin section of characteristic mineral pyrite (Py I) according to an embodiment; a - sedimentary ore body; b - disseminated pyrite ore body, with a small amount of pyrrhotite, sphalerite and galena; c - massive lead-zinc ore body, with pyrite veinlets developed in the lead-zinc ore body; d - dark gray pyritized dolomitic siltstone, with cubic pyrite aggregates; e - layered ore body, with main metallic minerals being pyrite and pyrrhotite; f - pyrite filling tectonic fissures, with dolomitic breccias; g - grayish white siliceous siltstone, with pyrite veinlets developed in layers; h - pyrite ore body, with lamination; i - pyrite ore body, with euhedral grains, with a small part being cataclastic structure, with large grains; j - cubic euhedral pyrite grains, with sphalerite developed in the form of long columns in the pyrite; k - different generations of pyrite developed in the form of gel structure; l - pyrite euhedral grains, with most of the pyrite having crushing structure; m - eye-shaped pyrite, with different generations of Py Ia, Py Ib and Py Ic; n - pyrite euhedral grains, with sphalerite developed in the form of vermicular structure in the pyrite; o - galena and sphalerite developed in the form of emulsion-like solid solution separation structure in the pyrite; p - early generation of cubic euhedral pyrite grains, with crushing structure; q - pyrite and calcite veins; r - pyrite and sphalerite mineral grains, with pyrite wrapping sphalerite; Po - pyrrhotite; Py - pyrite; Qtz - quartz; Sp - sphalerite; Gn - galena; Dol - dolomite; Cal - calcite;

[0027] Figure 4Figures a to p are schematic diagrams of hand specimens, polished sections, and thin sections for the example characteristic minerals pyrite (Py II) and petrographic classification; a - late pyrite pyrrhotite vein cutting through the Tianpeng Formation, with a small amount of quartz development; b - massive sulfide ore, mainly containing galena, sphalerite, pyrrhotite, pyrite and other metal minerals, with strong alteration at the contact between the ore body and the surrounding rock; c - massive sulfide ore, with galena veins developing in lamellar form, pyrrhotite developing in clumps, and pyrite developing in disseminated form, with a small amount of pyrite euhedral crystals; d - grayish yellow pyritization and galena- ization argillaceous siltstone, with pyrrhotite developing in fine vein form, and pyrite, galena, and sphalerite developing along the pyrrhotite fine veins, with local pyrrhotite being wrapped in quartz veins; e - sedimentary pyrite and pyrrhotite ore, with pyrite and pyrrhotite mainly developing in stratiform form and locally developing in granular aggregate form; f - biotite monzogranite, with pyrrhotite and pyrite metal fine veins; g - massive iron-copper-lead-zinc ore, with the main metal minerals being galena, sphalerite, chalcopyrite, pyrite, and a small amount of pyrrhotite, with pyrite and chalcopyrite developing in disseminated form; h - massive copper-iron-tin ore, with arsenopyrite developing in euhedral or cubic form, with galena and pyrite developing in disseminated form, and a small amount of chalcopyrite; i - grayish white granite porphyry, with porphyritic structure and massive structure, and the main components in the rock being quartz, feldspar, biotite, and other minerals, with sphalerite, galena, pyrite, and chalcopyrite veins in the rock; j - late generation pyrite and pyrrhotite developing in leaf-shaped crushed structure in galena, with a small amount of pyrrhotite and galena forming vermicular structure; k - late generation pyrite being replaced by arsenopyrite and chalcopyrite; l - late generation pyrite replacing sphalerite, galena, and pyrrhotite, with pyrrhotite developing in solid solution separation structure in galena; m - late generation pyrite replacing sphalerite, galena; n - sphalerite replacing pyrrhotite and pyrite; o - pyrite replacing arsenopyrite and chalcopyrite, with chalcopyrite having cataclastic structure, and pyrrhotite replacing pyrite in plate-shaped crystal form; p - disseminated pyrite developed in granite porphyry, with late generation pyrite being replaced by sphalerite; q - pyrrhotite replacing sphalerite in harbor-like structure, with chalcopyrite and stannite developing in vermicular structure in sphalerite, and obvious reaction rim being visible between stannite, galena, and sphalerite; r - earthy yellow stannite and arsenopyrite forming a reaction rim, with late generation pyrite replacing arsenopyrite in harbor structure, with crushed structure; Bt - biotite; Qtz - quartz; Pl - plagioclase; Ccp - chalcopyrite; Gn - galena; Py - pyrite; Po - pyrrhotite; Apy - arsenopyrite; Cst - cassiterite; Ccp - chalcopyrite; Stn - stannite; Sp - sphalerite; Po - pyrrhotite;

[0028] Figure 5 Figure is a Co / Ni diagram for the example characteristic mineral pyrite; regions I and II: sedimentary and sedimentary reformation regions; regions III and IV: magmatic and hydrothermal regions;

[0029] Figure 6 This is the elemental surface scanning analysis mapping diagram of pyrite (PyⅠ), a characteristic mineral of the embodiment;

[0030] Figure 7 This is the elemental surface scanning analysis mapping diagram of pyrite (PyⅠ), a characteristic mineral of the embodiment;

[0031] Figure 8 Schematic diagram of the composite mineralization process of the ore deposit in the embodiment; a. Schematic diagram of the exhalative sedimentation in the late Caledonian movement; b. Schematic diagram of the magmatic-hydrothermal process in the late Yanshanian movement; 1-crystalline basement (migmatite); 2-deep-water sedimentary limestone; 3-sandstone, siltstone; 4-dolomitic siltstone; 5-dolomite; 6-Early Cambrian-Sinian flysch formation; 7-Middle Cambrian Dayakou Formation; 8-Middle Cambrian Tianpeng Formation; 9-Middle Cambrian Longha Formation; 10-Early Devonian Posongchong Formation; 11-Early Devonian Pojiao Formation; 12-fault; 13-flow direction of ore-bearing hydrothermal fluid; 14-plate movement direction; 15-skarn; 16-Yanshanian granite; 17-metallic ore body. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1

[0034] The present embodiment provides a method for identifying composite mineralization in a magmatic hydrothermal system, comprising the following steps:

[0035] S1: Field geological survey and sample collection: Based on the existing regional geological maps, research reports and other surveys of the target mineral deposits, carry out detailed field geological surveys to identify the geological characteristics and spatial distribution of magmatic hydrothermal deposits, determine the composition of the magmatic hydrothermal system, record typical geological phenomena and mineralized outcrops, and systematically collect rock and ore samples to ensure comprehensive sampling without omissions.

[0036] S2: Characteristic mineral screening and rock (ore) processing and identification: carry out macroscopic and microscopic structural observation of rocks (ores), screen characteristic minerals, select characteristic minerals from different geological units, different locations, and different types for processing, and record the petrographic characteristics of characteristic minerals in detail.

[0037] S3: Characteristic mineral ore-forming generation and mineralization stage division: Detailed observation of the geological unit rock (ore) sample and thin section where the characteristic mineral is located, stage division according to the petrographic characteristics of the characteristic mineral, combined with data, to determine the characteristic mineralization age and preliminarily determine the deposit genesis type.

[0038] S4: Geochemical analysis and testing: Based on the stage division structure and the microscopic petrographic characteristics, the main, trace and rare earth element contents of different types of characteristic minerals and the element distribution in the mineral are obtained by using in-situ micro-area analysis technology.

[0039] S5: Deposit genesis verification: Through the corresponding mineral template in the Geokit, Origin and other mapping software, based on the content of the characteristic mineral, trace and rare earth elements, and element anomaly value, the ore-forming environment and deposit genesis of different types of characteristic minerals are distinguished.

[0040] S6: Element zoning pattern analysis: According to the element distribution Mapping diagram of the characteristic mineral, the element zoning pattern in the mineral is determined, the superimposed type of magmatic hydrothermal deposit mineralization is distinguished, and the ore-forming environment and ore precipitation mode are indicated.

[0041] S6: Reconstruction of composite mineralization process: Based on the regional geological evolution history and combined with the analysis results of the above steps, the composite mineralization process of the magmatic hydrothermal system in the study area is analyzed.

[0042] In this embodiment, during the step S1 field geological survey, the target ore (field) bed stratum, structure, magmatic rock and ore body information need to be found out, including but not limited to the main ore-bearing stratum, the distribution of ore-hosting structure, the ore-hosting wall rock, the ore body shape and the contact relationship with the wall rock, etc.

[0043] In this embodiment, the samples collected and selected in step S1 should collect typical regional samples in the ore body, various rock bodies, lithological boundaries and fault fracture zones in the study area.

[0044] In this embodiment, when recording typical geological phenomena and mineralized outcrops and systematically collecting rock (ore) samples, the mineralized outcrop location and sampling location points need to be marked on the regional geological map. The sample collection should cover as many different lithology samples in all geological units in the target ore (field) bed as possible. The sample types include but are not limited to ore body, ore body wall rock, magmatic rock, sedimentary rock, metamorphic rock and other rocks in the layer where the ore body is located.

[0045] In the embodiment, the step S2 of screening characteristic minerals includes: being widely distributed in each geological unit of the study area, i.e. appearing in more than 80% of the geological unit bodies; the mineral characteristics are greatly different, the crystal morphological structures are different, and the minerals are in the forms of massive, granular, layered, etc., and the colors have distinguishability, such as the color difference of the same metal mineral; the mineral genetic conditions are simple, and the minerals can be formed under various mineralization, i.e. the temperature and pressure conditions of mineralization are low, and the minerals belong to medium-low temperature hydrothermal minerals in a magmatic hydrothermal system, such as low-temperature sulfide metals like pyrite and chalcopyrite, etc., and the minerals can be formed under conditions like sedimentation and metamorphism, etc.

[0046] In the embodiment, the step S2 of screening characteristic minerals needs to observe the rock and mineral information of all geological units in detail, especially the different lithological ore bodies and the contact zones of the ore bodies and the surrounding rocks, screen the minerals common to each geological unit, and select typical minerals representing the mineralization stages as the characteristic minerals.

[0047] In the embodiment, the step S2 of screening characteristic minerals should have the following characteristics: widely existing in the ore-forming geological body; being able to represent the mineralization stage of the local geological unit; and having low requirements on the mineralization environment and meeting the mineralization conditions under different origins.

[0048] In the embodiment, the step S2 of processing and handling the characteristic minerals needs to select rock (ore) samples of different geological units where the characteristic minerals are located, make optical slices and thin slices (probe slices and laser slices), and comprehensively identify the colors, structures, textures, and paragenetic combinations of the characteristic minerals at different positions and of different types by using optical microscopes and electron microscopes, and record the petrographic and mineralogical characteristics of the characteristic minerals in detail. If there are zoning characteristics, backscattered images (BSE) can be taken for further observation and description.

[0049] In the embodiment, the step S3 of dividing the types and stages of the characteristic minerals takes the macroscopic geological characteristics as the main distinguishing basis and takes the microscopic geological characteristics of the characteristic minerals under the microscope as the auxiliary distinguishing basis, distinguishes different types of characteristic minerals, and the macroscopic geological characteristics include but are not limited to the spatial distribution characteristics of the minerals, the paragenetic combination of the minerals, the contact and interpenetration relationship between the minerals, the color, the texture, etc.; and the microscopic characteristics include but are not limited to the mineral structure, the paragenetic combination, the mineral generation, etc.

[0050] In the embodiment, the step S3 of dividing the types and stages of the characteristic minerals needs to use the petrological and geochemical evidence related to the stratum age, the zircon U-Pb age, etc. that can represent the rock and mineralization age of the minerals, including but not limited to biological fossils, zircon U-Pb chronology analysis, granite Lu-Hf isotope analysis, and garnet U-Pb dating analysis, etc.

[0051] In the embodiment, the step S3 of judging the genetic type of the characteristic mineral needs to be based on the ore or rock structure and tectonic analysis to further determine the genetic type of the rock or ore.

[0052] In the embodiment, the step S4 of selecting the geochemical analysis test is: the in-situ micro-area major element test technology method is electron probe, the trace and rare earth element content test technology method is laser ablation, and the internal element distribution test technology method of the mineral is face scanning analysis.

[0053] In the embodiment, the step S4 of testing the content of the major elements includes but is not limited to: SiO2, Al2O3, FeO, Fe2O3, MgO, Na2O, TiO2, etc.; the trace and rare earth element content test includes but is not limited to: As, Co, Ni, Se, Cd, etc.; and the element distribution content of the face scanning analysis includes but is not limited to: Fe, Cu, Pb, Zn, Ag, Au, etc.

[0054] In the embodiment, the step S5 of verifying the deposit genesis needs to use the geochemical information of the characteristic mineral and the surrounding paragenetic minerals to analyze and verify by means of the existing mineral geochemical method after judging the genetic type of the characteristic mineral by the petrographic method.

[0055] In the embodiment, the step S6 of analyzing the superimposed mineralization is specifically operated as follows: according to the results of the step S3 of dividing the petrographic stage of the characteristic mineral and the step S5 of analyzing and verifying the deposit genesis, combining the face scanning image of the characteristic mineral and the internal element distribution characteristics of the mineral, determining the internal element zoning pattern of the mineral based on the mineral microstructure and the element distribution difference, and discriminating the mineral formation environment and analyzing the mineral matter precipitation mode.

[0056] In the embodiment, the step S6 of the internal element zoning pattern of the mineral needs to comply with the microstructure characteristics of the mineral, and the internal element distribution zoning pattern of the mineral is mainly based on the related elements for the genetic discrimination of the corresponding characteristic mineral in the step S5, and secondly based on the trace and rare earth elements related to the source of the crust and mantle material.

[0057] In the embodiment, the step S7 of the regional geological evolution history needs to collect data reports widely to determine the magmatic activity and tectonic evolution of the region where the magmatic hydrothermal system is located.

[0058] In the embodiment, the step S7 of the composite mineralization process of the magmatic hydrothermal system needs to comply with the ore-forming age and the ore-forming historical events, and the spatial distribution of the ore body needs to correspond to the composite mineralization.

[0059] Embodiment 2

[0060] This example is implemented in a magmatic hydrothermal type silver lead zinc tin polymetallic ore in the southeast of Yunnan province, with pyrite as a characteristic mineral, dividing into two types of pyrite, stratified, stratiform and lenticular and network vein, disseminated and lump, respectively indicating two stages of mineralization of sedimentation and magmatic hydrothermal, and inverting the geological history of mineralization process, which has achieved remarkable results, including the following steps:

[0061] S1: Detailed field geological survey for target deposit

[0062] The deposit is located in the northwest outer margin of the Bozhushan granite body in the southeast of Yunnan province, and is distributed around the Bainiuchang village with five ore blocks of Baiyang, Duimengshan, Awei, Chuanxindong and Miewei. Two exploration right areas of Mujibai and Lesichong are distributed on the east and west sides. The Cambrian (Chongzhuang formation, Dazhai formation, Dayakou formation, Tianpeng formation and Longha formation) and Devonian (Pomingsong formation, Poguzi formation and Bajiaqing formation) strata are exposed, and the Carboniferous, Permian and Quaternary strata are exposed around the periphery. The lithology is mainly biotite monzogranite, granite porphyry, skarn, dolomite, dolomitic limestone, siltstone and carbonate rock. The ore-bearing strata are mainly Cambrian Tianpeng formation and Longha formation, and the ore-bearing lithology is siltstone, argillaceous siltstone, dolomitic siltstone, dolomite and carbonate rock in the F3 fault fracture zone. A series of northwest-southeast trending folds, faults and interlayer fracture zones are developed in the area where the deposit is located. The main ore body occurs in the F3 fault and interlayer fracture zone, and penetrates through multiple ore blocks. The magmatic activity is developed, mainly with late Yanshanian acidic intrusive rocks, and there are also Hercynian basic intrusive rocks. The main metallic minerals are galena, marmatite, pyrite, pyrrhotite, arsenopyrite and chalcopyrite, and the main silver minerals are tetrahedrite, tetra-antimony silver, deep red silver and stibiconite.

[0063] The sampling positions are five ore blocks of Baiyang, Duimengshan, Awei, Chuanxindong and Miewei and two exploration right areas of Mujibai and Lesichong around the deposit (as shown in Figure 2 ), covering all ore blocks and adjacent research areas of the magmatic hydrothermal deposit; the sample types include main magmatic rocks (biotite monzogranite, granite porphyry), sedimentary rocks (dolomite, dolomitic limestone, carbonate rock, siltstone), metamorphic rocks (skarn) and ores, covering all sample types that can be collected at present.

[0064] S2: Screening of characteristic minerals and processing identification of rocks (ores)

[0065] The hand specimens from five ore sections (Baiyang, Duomen, Awei, Chuanxindong, and Miewei) and two exploration right areas (Mujibai and Lesichong) were observed. The main metallic minerals in the rock (ore) samples are pyrite, sphalerite, galena, arsenopyrite, and chalcopyrite. The non-metallic minerals related to the mineralization stage are apatite, quartz, and calcite. The metallic minerals commonly found in the rock samples and ore samples are pyrite, sphalerite, and galena. Pyrite is the most widely distributed mineral, and its formation process is throughout the entire mineralization history of the deposit. The types of pyrite developed in different periods, strata, and sections are significantly different. Pyrite has a low mineralization temperature and is suitable for most mineralization environments, which is representative of the genesis of different types of deposits and composite mineralization. Therefore, pyrite is used as the characteristic mineral in this case.

[0066] In the indoor study, the macroscopic and microscopic fabric analysis of the collected rock and ore samples were conducted. Macroscopically, the pyrite ore is divided into two types: one is the stratiform, stratiform-like, and lenticular synsedimentary structure ore (PyI) (as shown in Figure 3 ), and the other is the vein, disseminated, and massive replacement structure ore (PyII) (as shown in Figure 4 ). Through polarizing microscope observation, it is found that PyI pyrite is mostly euhedral-hedral cubic aggregate with lamellar structure, and it is associated with magnetite and sphalerite. PyII pyrite is anhedral granular with replacement residual structure, and it is associated with galena and chalcopyrite. Eleven typical samples containing pyrite were further selected, covering granite, skarn, and ore types. After cutting and polishing, the samples were made into thin sections and probe pieces, and the morphology of pyrite, associated mineral assemblage, and alteration characteristics were recorded in detail. For example, PyI pyrite shows raspberry structure and colloidal structure under the microscope, reflecting the sedimentary environment. PyII pyrite shows cataclastic structure and hydrothermal filling characteristics. These petrographic characteristics provide key evidence for subsequent division of mineralization stages.

[0067] S3: Characteristic mineralization generation and division of mineralization stages

[0068] Based on petrographic characteristics, the pyrite in this deposit is divided into two stages: the early stage (PyI) formed in the late Caledonian movement, which is synchronous with the deposition of Cambrian Tianpeng Formation, and shows laminated structure and synsedimentary brecciated structure; the late stage (PyII) formed in the late Yanshanian movement, which is controlled by magmatic hydrothermal activity and shows vein shape cutting through the early ore body. Combined with regional tectonic evolution, PyI corresponds to the sedimentary exhalative mineralization event, and PyII is related to the hydrothermal activity of the concealed granite (zircon U-Pb age of 87-91 Ma). In addition, through the analysis of mineral paragenetic sequence, it is found that PyII pyrite is often replaced by sphalerite and galena, and is accompanied by skarnization alteration, which further supports the conclusion of superimposed magmatic hydrothermal mineralization. This division clarifies the multi-stage superimposed characteristics of the deposit and lays a foundation for the determination of genetic type.

[0069] S4: Geochemical analysis test

[0070] LA-ICP-MS technology is used for in-situ micro-area analysis of 11 pyrite samples to obtain major, trace and rare earth element data. The results show that the PyI pyrite has stable FeS2 content (>99.35%), significantly enriched As (average 1003 ppm) and Sb (112 ppm), and Co / Ni ratio <1, which is consistent with the sedimentary genetic characteristics; PyII pyrite is rich in Cu (maximum 24615 ppm) and Ag (22 ppm), and Co / Ni ratio >1, indicating magmatic hydrothermal origin. The face scanning analysis (such as MJB23-9 sample) shows that the PyI pyrite has a rhythmic zonal structure with periodic distribution of Fe and Mn; the PyII pyrite (such as BNC22-5) has enriched Cu and As in the fissures, and Co and Ni are uniformly distributed. The rare earth element content is generally below the detection limit, reflecting that the ore-forming fluid is mainly deep source. These data provide geochemical evidence for the discrimination of ore-forming environment.

[0071] S5: Verification of deposit genesis

[0072] The trace elements of pyrite are analyzed by Geokit and Origin software. In the Co-Ni binary diagram (as shown in Figure 5 ), most of the PyI samples fall into the sedimentary area (Co / Ni <1), and the PyII samples are concentrated in the hydrothermal area (Co / Ni >1), and some transitional samples (such as BNC22-5) indicate sedimentary-hydrothermal superimposition and reconstruction. The As-Ag correlation analysis shows that Ag is positively correlated with As in PyII (R 2 =0.72), reflecting the co-precipitation of metals in hydrothermal fluid; the Ag distribution in PyI is discrete, indicating original sedimentary enrichment. Combined with the regional magmatic activity age (80-100 Ma) and the exhalative sedimentary age (Cambrian), the theory of superimposed magmatic hydrothermal complex genesis on the basis of exhalative sedimentation is verified.

[0073] S6: Element zoning pattern analysis

[0074] The mapping of pyrite surface scan reveals the element zoning difference of two stages of mineralization (as shown in Figure 6 , 7 ). The core of PyI pyrite (MJB23-9) is pure (mainly Fe and S), and the edge is rich in Mn, Ca and Sr, reflecting the periodic change of fluid composition during the process of exhalative sedimentation; Cu and As are enriched along the fissure in PyII pyrite (BNC22-5), and Sb and Pb are gathered at the boundary, indicating hydrothermal filling and metasomatism. In addition, the uniform distribution of Co and Ni in PyII is consistent with the isomorphism replacement in high temperature environment, while the local enrichment of PyI may be related to the superposition of late hydrothermal fluid. These zoning patterns clearly show the evolution path of the ore-forming fluid, that is, the spatio-temporal coupling of early sedimentary mineralization and late hydrothermal modification.

[0075] S7: Reconstruction of composite mineralization process

[0076] Based on the regional geological evolution history and combined with the analysis results of the above steps, the composite mineralization process of the deposit can be divided into two stages (as shown in Figure 8 ).

[0077] Late Caledonian exhalative sedimentation: Cambrian submarine hydrothermal fluid upwelled along the fault, forming layered pyrite, sphalerite and sulfide minerals in a reducing environment, forming the initial ore source layer.

[0078] Late Yanshanian magmatic hydrothermal superposition: Late Cretaceous granite intrusion triggered hydrothermal activity, activated early minerals and carried Sn, W, Ag and other elements, and migrated upward along F3 fault. With the decrease of temperature and pressure, skarn type Sn (W) ore bodies were formed in the deep part, Ag-Pb-Zn sulfide was precipitated in the middle and shallow part, and low temperature Sb mineralization was enriched in the shallow part.

[0079] This process embodies the characteristics of "different time, same place, multiple factors and superposition" of composite mineralization, and provides a theoretical basis for deep prospecting in southeast Yunnan.

[0080] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details, nor limit the present application to the specific embodiments described. Obviously, many modifications and variations can be made according to the contents of the present application. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for identifying composite mineralization in a magmatic hydrothermal system, characterized in that: The following steps are involved: S1: Field geological survey and full-element sampling: Conduct geological survey based on the target ore field regional geological map and research report, and systematically collect samples of ore bodies, surrounding rocks, igneous rocks, sedimentary rocks and metamorphic rocks; S2: Characteristic mineral screening and petrographic identification: Screening of characteristic minerals throughout the mineralization stage through field observation, hand specimen observation and microstructure analysis, preparation of optical sections and thin sections and microscopic identification; S3: Mineralization Generation Division: The mineralization stages are divided according to the contact and interpenetration relationship of characteristic minerals and the ring-zone structure characteristics. The mineralization age is determined by combining the zircon U-Pb geochronology analysis and testing method to preliminarily identify the genetic type of the deposit; S4: In situ geochemical analysis: electron microprobe analysis of major elements, LA-ICP-MS testing of trace rare earth elements, and surface scanning technology to obtain element distribution images; S5: Verification of ore genesis: Geokit data analysis and mapping software is used to perform geochemical mapping of characteristic minerals, and the mineralization environment is verified in combination with the paragenetic mineral combination; S6: Element zoning pattern analysis: Establish the spatial zoning pattern of major and trace elements of characteristic minerals based on the surface scanning mapping diagram; S7: Reconstruction of composite mineralization processes: integrating regional tectonic evolution history with multi-period mineralization evidence to construct a spatiotemporal coupling model.

2. The method according to claim 1, wherein In step S2: the characteristic mineral screening conditions include: being widely distributed in ore bodies, surrounding rocks and igneous rocks; having typical structures indicating the mineralization stage; the mineralization temperature ranges from low temperature to high temperature, covering the sedimentary, metamorphic and magmatic hydrothermal mineralization temperature range as much as possible; the petrographic identification method includes: petrographic observation of hand specimens, making light slices, probe slices and laser slices, observing the mineral paragenesis combination with an optical microscope, and using backscattered electron imaging to identify the ring structure.

3. The method according to claim 1, wherein In step S3: combining the petrographic characteristics of the characteristic minerals, the contact and interpenetration relationship between the characteristic minerals and the characteristic minerals and other minerals, the order of mineral formation is determined. If the characteristic minerals are sedimentary, including but not limited to layered / stratified, strawberry-shaped, and synsedimentary structures, the mineralization age is determined according to the age of the stratum where the ore body is located; if the characteristic minerals are magmatic hydrothermal, including but not limited to massive, stockwork, disseminated, and replacement structures, the mineralization age is obtained by U-Pb dating of zircons in the igneous rocks surrounding the ore body where the characteristic minerals are located; Divide the mineralization period and stage according to the characteristic mineralization type and mineralization age, and preliminarily determine the cause of formation; The division of mineralization periods must be consistent with the existing chronological analysis and test results of the target mineral field, including but not limited to biological fossils, zircon U-Pb chronological analysis, granite Lu-Hf isotope analysis, and garnet U-Pb dating analysis.

4. The method according to claim 1, wherein In step S4: the main element analysis is carried out using an electron probe to test SiO2, Al2O3, FeO, Fe2O3, MgO, Na2O, and TiO2 with an accuracy of 0.01wt%; Trace and rare earth element analysis was performed using laser ablation inductively coupled plasma mass spectrometry to test As, Co, Ni, Cu, and Ag with a detection limit of 0.1 ppm; Element surface scanning uses X-ray energy spectrum analysis technology / LA-ICP-MS mineral element surface scanning analysis with a spatial resolution of 5μm to analyze the distribution of Fe, S, Cu, Pb, Zn, and Ag.

5. The method according to claim 1, wherein The analysis of the element zoning pattern in step S6 is specifically as follows: based on the test results of the main and trace geochemical components of the characteristic minerals and the element distribution Mapping image of the surface scanning analysis, the element zoning is divided according to the difference in the content of different elements and the distribution range within the minerals; attention is paid to the abnormal element distribution in the tiny intervals of the minerals, including the abnormal element filling in the fine cracks inside the minerals and the abnormal element change in the ring structure at the edge of the minerals.

6. The method according to claim 1, wherein Step S7 includes: extensive data collection and reporting on the regional geological evolution history is required to determine the magmatic activity and tectonic evolution of the region where the magmatic hydrothermal system is located; in accordance with the mineralization era and historical events, the spatial distribution of ore body output must correspond to the composite mineralization.

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