Method for judging genesis and depositional environment of siliceous rocks by using multi-index comprehensive analysis

Abstract

The application provides a method for determining the genesis and sedimentary environment of siliceous rocks by using multi-index comprehensive analysis, relates to the technical field of geological exploration and geochemistry, and comprises the following steps: pretreating a siliceous rock sample to obtain a to-be-tested powder sample; testing the to-be-tested powder sample to obtain the content of corresponding elements; calculating and obtaining a genesis parameter for characterizing the genesis type of the siliceous rock, and then obtaining a genesis type determination result; calculating and obtaining an environment parameter for characterizing the sedimentary environment of the siliceous rock, and then obtaining a sedimentary environment determination result; and comprehensively analyzing and cross-verifying the determination results to form a final discrimination conclusion. The application can effectively distinguish hot water deposition, biological genesis and composite genesis siliceous rocks by comprehensively analyzing multiple indexes such as major elements, trace elements and rare earth elements, and combining multiple graphic cross-verifications, obviously reduces the multi-solution and subjectivity of traditional single-index discrimination, and accurately determines the sedimentary environment such as continental margin and ocean basin through element ratio and graphic analysis.

Description

Technical Field

[0001] This invention relates to the fields of geological exploration and geochemistry, and in particular to a method for determining the genesis and sedimentary environment of siliceous rocks using a comprehensive analysis of multiple indicators. Background Technology

[0002] Siliceous rocks are a type of chemical sedimentary rock dominated by SiO2. They are often closely related to deep-sea sedimentation, volcanic tectonic activity, and oceanic plate evolution, and are of great significance in recording paleogeographic patterns, paleooceanic environments, and tectonic evolution stages. In regional geological surveys and resource exploration, the determination of the genetic type and sedimentary environment of siliceous rocks is directly related to the correct interpretation of ocean basin opening and closing history, plate subduction location, and mineralization background.

[0003] Existing research has shown that organically combining multiple indicators such as major elements, trace elements, and rare earth elements, and supplementing them with cross-validation using various discriminant diagrams, can significantly improve the accuracy of genetic and environmental identification. However, a systematic and standardized technical process is currently lacking, encompassing sample collection, experimental testing, indicator calculation, comprehensive discrimination, and result output. Particularly in cases involving complex genetic siliceous rocks, transitional sedimentary environments, and complex tectonic settings, existing methods still lack unified quantitative criteria and visual standards, limiting their widespread application in the reconstruction of siliceous rocks from tectonic and paleoenvironmental contexts. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the genesis and sedimentary environment of siliceous rocks by using a comprehensive analysis of multiple indicators, so as to at least solve one of the technical problems existing in the prior art.

[0005] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a method for determining the genesis and sedimentary environment of siliceous rocks using a comprehensive analysis of multiple indicators, comprising: (a) Pre-treating the siliceous rock sample to obtain the powder sample to be tested; (b) The major elements, trace elements, rare earth elements and silicon isotopes of the powder sample to be tested are determined to obtain the corresponding element contents; (c) Based on the data obtained in step (b), calculate and obtain the genetic parameters that characterize the genetic type of siliceous rocks, and then output the genetic type determination result according to the preset genetic type discrimination system; (d) Based on the data obtained in step (b), calculate and obtain the environmental parameters characterizing the siliceous rock depositional environment, and then output the depositional environment determination results according to the preset depositional environment discrimination system; (e) Perform comprehensive analysis and cross-validation on the judgment results of steps (c) and (d) to form the final judgment conclusion.

[0006] Furthermore, the cause type discrimination system includes at least one classification rule based on a preset threshold range, and at least one verification method based on a diagram.

[0007] Furthermore, the genetic type includes one or more of hydrothermal, biological, and complex genetic origins.

[0008] Preferably, the genetic parameters include silicon content, aluminum content, titanium content, uranium content, thorium content, zirconium content, cerium content, europium content, europium anomaly, cerium anomaly, uranium-thorium ratio, the ratio of aluminum to the total aluminum-iron-manganese content, and silicon isotope δ¹⁴. 30 One or more of the Si values; Preferably, the parameters for determining the hydrothermal origin include: silicon content of 91.0~99.8 wt%, aluminum content ≤1.5 wt%, titanium content ≤0.06 wt%, uranium-thorium ratio ≥2.99, zirconium content ≤85 μg / g, total rare earth element content ≤51.04 μg / g, europium anomaly ≥1.04, cerium anomaly 0.66~0.72, and silicon isotope δ 30 The Si value is -0.29 to -0.25‰, and the ratio of aluminum to the total amount of aluminum, iron, and manganese is ≤0.40; Preferably, the parameters for determining the biogenicity include: silicon content of 85.0~95.0 wt%, aluminum content ≥3.0 wt%, titanium content ≥0.10 wt%, uranium-thorium ratio ≤0.25, zirconium content ≥100 μg / g, total rare earth element content ≥150 μg / g, europium anomaly value of 0.90~1.05, cerium anomaly value of 1.02~1.54, and silicon isotope δ 30 The Si value is 1.8~1.9‰, and the ratio of aluminum to the total amount of aluminum, iron and manganese is ≥0.60; Preferably, the parameters for determining the composite origin include: silicon content of 88.0~96.0 wt%, aluminum content of 1.5~3.0 wt%, titanium content of 0.06~0.10 wt%, uranium-thorium ratio of 0.25~2.99, zirconium content of 85~100 μg / g, total rare earth element content of 51.04~150 μg / g, europium anomaly of 0.95~1.10, cerium anomaly of 0.72~1.02, and silicon isotope δ 30 The Si value is -0.25 to 1.8‰, and the ratio of aluminum to the total amount of aluminum, iron, and manganese is 0.40 to 0.60.

[0009] Furthermore, the graph-based verification method in the genetic type discrimination system includes: projecting the calculated genetic parameters onto an Al-Fe-Mn triangular diagram, a rare earth element distribution pattern diagram, or an Eu-Ce anomaly relationship diagram, and outputting the corrected genetic type judgment result based on the region where the projected points are located.

[0010] Furthermore, the sedimentation environment discrimination system includes at least one classification rule based on a preset threshold range, and at least one verification method based on a diagram.

[0011] Furthermore, the environmental parameters include one or more of the following: the ratio of aluminum to total aluminum, iron, and manganese; cerium anomaly; yttrium-holmium ratio; manganese oxide to titanium dioxide mass ratio; principal element triangular diagram coordinate values; and rare earth element ternary diagram coordinate values. Preferably, the siliceous rock depositional environment includes one or more of the following: mid-ocean ridges, continental margins, ocean basins, and ocean islands; Preferably, the parameters for determining the mid-ocean ridge include a ratio of aluminum to total aluminum, iron, and manganese of approximately 0.00819, a cerium anomaly value of <0.55, a yttrium-holmium ratio of 50-60, and a manganese oxide to titanium dioxide mass ratio of 0.5-3.5. Preferably, the parameters for determining the continental margin include: a total aluminum and aluminum-iron-manganese content of approximately 0.319, a cerium anomaly value of <0.55, a yttrium-holmium ratio of 50-60, and a manganese oxide to titanium dioxide mass ratio of 0.5-3.5. Preferably, the parameters for determining the ocean basin and ocean islands include: the ratio of aluminum to the total amount of aluminum, iron and manganese is approximately 0.619, the cerium anomaly value is 0.9~1.3, the yttrium-holmium ratio is approximately 28, and the mass ratio of manganese oxide to titanium dioxide is <0.5.

[0012] Furthermore, the graph-based verification method in the sedimentary environment discrimination system includes: plotting the calculated environmental parameters onto a major element triangular diagram or a La-Th-Sc rare earth element ternary diagram, and outputting the corrected sedimentary environment judgment result based on the region where the plotted points are located.

[0013] Furthermore, when the genetic type determination result output by step (c) includes hydrothermal or complex genetic origin, it also includes: preparing thin sections of fluid inclusions in siliceous rocks, measuring the homogenization temperature and salinity of the fluid inclusions therein, and further confirming the hydrothermal origin and fluid properties based on the homogenization temperature and salinity range, and assessing the intensity or depth of hydrothermal activity.

[0014] Furthermore, the homogenization temperature is used to determine the intensity of hydrothermal activity and / or the depth of the hydrothermal source, including: When the homogenization temperature is 50-80℃, it indicates that the fluid was formed in a low-temperature diagenetic environment or a fluid with a temperature similar to that of seawater. When the homogenization temperature is 80-150℃, it indicates the presence of hydrothermal activity. The higher the homogenization temperature, the greater the intensity of the hydrothermal activity or the deeper its source. When the homogenization temperature is above 150°C, it indicates a medium- to high-temperature hydrothermal event, representing a connection to magmatic activity or deep circulating hot water.

[0015] Furthermore, the salinity is used to determine the source nature and / or evolution process of diagenetic fluids, including: When the salinity is close to that of modern seawater, the indicator fluid mainly originates from seawater or has been thoroughly mixed with seawater; When the salinity is significantly higher than that of modern seawater, it indicates that the fluid has undergone evaporation and concentration or mixed with high-salinity formation water; When the salinity is significantly lower than that of modern seawater, it indicates that the fluid is affected by atmospheric precipitation or freshwater.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for determining the genesis and sedimentary environment of siliceous rocks using a multi-index comprehensive analysis. Step (a) involves preparing the powder sample to be tested. Step (b) simultaneously acquires four types of geochemical parameters: major elements, trace elements, rare earth elements, and silicon isotopes, constructing a multi-dimensional data foundation. Then, relying on the genetic type and sedimentary environment discrimination criteria established in steps (c) and (d) respectively, accurate differentiation of genetic types and clear definition of the sedimentary environment of siliceous rocks are achieved. Finally, the cross-validation mechanism in step (e) resolves the ambiguity and logical fragmentation issues of single-index discrimination, making the genetic and environmental determination results repeatable, verifiable, and self-consistent. This significantly improves the accuracy and reliability of geological interpretation of siliceous rocks in paleocean reconstruction, plate tectonics analysis, and mineral exploration. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is an Al-Fe-Mn discriminant diagram for the genesis of siliceous rocks provided in an embodiment of the present invention; Figure 2 Diagram illustrating the major element discrimination of siliceous rock sedimentary environments; Figure 3 A diagram illustrating the La-Th-Sc elemental discrimination of siliceous rock sedimentary environments. Detailed Implementation

[0019] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides a method for determining the genesis and sedimentary environment of siliceous rocks using a multi-index comprehensive analysis, comprising: (a) Pre-treating the siliceous rock sample to obtain the powder sample to be tested; (b) The major elements, trace elements, rare earth elements and silicon isotopes of the powder sample to be tested are determined to obtain the corresponding element contents; (c) Based on the data obtained in step (b), calculate and obtain the genetic parameters that characterize the genetic type of siliceous rocks, and then output the genetic type determination result according to the preset genetic type discrimination system; (d) Based on the data obtained in step (b), calculate and obtain the environmental parameters characterizing the siliceous rock depositional environment, and then output the depositional environment determination results according to the preset depositional environment discrimination system; (e) Perform comprehensive analysis and cross-validation on the judgment results of steps (c) and (d) to form the final judgment conclusion.

[0022] This invention, through standardized sample collection and preprocessing procedures, systematically tests four core indicators: major elements, trace elements, rare earth elements, and isotopes. Combined with standardized discrimination charts and threshold systems, it constructs a three-tiered process of "indicator screening - graphical verification - comprehensive judgment," enabling precise differentiation of the hydrothermal sedimentary origins, biogenic origins, and composite origins of siliceous rocks, as well as the definition of sedimentary environments such as continental margins, ocean basins, and mid-ocean ridges. This invention solves the problems of traditional single-indicator discrimination being susceptible to diagenetic interference and fragmented logic, offering advantages such as visualized criteria, standardized operation, and high result reliability. It can be widely applied in regional tectonic evolution research, paleomarine environment reconstruction, and mineral resource exploration.

[0023] The following is a detailed explanation of this method.

[0024] In some preferred embodiments, the sampling specifications for siliceous rock samples are as follows: select fresh outcrops or cores of siliceous rock, avoiding weathering zones, fractured areas and mineralized alteration sections, and record the sampling location, lithology, color and occurrence state (layered, lenticular, etc.).

[0025] In some preferred embodiments, the pretreatment process of the siliceous rock sample includes: grinding and cleaning the selected siliceous rock sample, coarsely crushing and removing impurities, finely grinding to 200~400 mesh, and storing in a desiccator for ≤48h.

[0026] In some preferred embodiments, step (b) specifically includes: determining major elements using XRF, and determining trace elements and rare earth elements using ICP-MS; for samples suspected of being of composite origin, adding silicon isotopes (δ¹⁸O₂). 30 Tests were performed on Si or Ge / Si, etc. After the tests were completed, all derived indicators were calculated using the same set of formulas to ensure that the data were comparable between different samples.

[0027] In some preferred embodiments, the cause type discrimination system includes classification rules based on preset threshold intervals and a verification method based on diagrams.

[0028] The genetic types include one or more of hydrothermal, biological, and complex genetic types.

[0029] The genetic parameters include silicon content, aluminum content, titanium content, uranium (U) content, thorium (Th) content, zirconium (Zr) content, cerium (Ce) content, europium (Eu) content, europium anomaly (δEu), cerium anomaly (δCe), uranium-thorium ratio (U / Th), the ratio of aluminum to the total aluminum-iron-manganese content, and silicon isotope δ¹⁴. 30 One or more of the Si values.

[0030] The specific details of the genetic types and discrimination system of siliceous rocks are shown in Table 1.

[0031] Table 1. Index System for Determining the Genetic Type of Siliceous Rocks

[0032] Preferably, the graph-based verification method includes: projecting the calculated causal parameters onto an Al-Fe-Mn triangular diagram, a rare earth element distribution pattern diagram, or an Eu-Ce anomaly relationship diagram, and outputting a corrected causal type determination result based on the region where the projected points are located.

[0033] Specifically, step (c) is the causal determination, which includes: calculating the hydrothermal causal score and the biogenic causal score based on the calculation results of major, trace, and rare earth elements, and comparing them with the preset index combination and threshold range of this invention, to preliminarily determine the causal type. Then, the sample is projected onto the Al-Fe-Mn triangular diagram (…). Figure 1The results of the cause determination are verified graphically and corrected.

[0034] in, Figure 1 This is an Al-Fe-Mn triangulation diagram for the genesis of siliceous rocks. The contents of Al, Fe, and Mn obtained from sample testing and analysis are plotted on this diagram, and their origin can be determined based on the location of the plotted points. If the sample data falls into the "Biogenic Siliceous Rock" or "Hydrothermal Siliceous Rock" category, it indicates that the siliceous rock sample is of biogenic or hydrothermal origin. If it falls into other areas, it may be considered to have a combined origin, possibly formed by the combined action of biogenic and hydrothermal genesis.

[0035] In some preferred embodiments, the sedimentation environment discrimination system includes classification rules based on preset threshold ranges and a graph-based verification method.

[0036] The environmental parameters include one or more of the following: aluminum to aluminum-iron-manganese ratio, cerium anomaly value, yttrium-holmium ratio, manganese oxide to titanium dioxide mass ratio, principal element triangular diagram coordinate value, and rare earth element ternary diagram coordinate value.

[0037] Preferably, the siliceous rock depositional environment includes one or more of the following: mid-ocean ridges, continental margins, ocean basins, and ocean islands.

[0038] The formation of different types of siliceous rocks is often closely related to specific sedimentary environments (such as water depth, redox conditions, and tectonic setting), and has strong indicative significance for paleosedimentary facies, as shown in Tables 2-3.

[0039] Table 2. Determination of sedimentary facies and sedimentary environment

[0040] Table 3. Geochemical identification of sedimentary environments

[0041] Preferably, the graph-based verification method in the sedimentary environment discrimination system includes: plotting the calculated environmental parameters onto a major element triangular diagram (…). Figure 2 ) or La-Th-Sc rare earth element ternary diagram ( Figure 3 The system outputs the corrected sedimentary environment determination results based on the area where the sampling point is located.

[0042] Specifically, step (d) is the determination of the sedimentary environment, which includes: determining the corresponding facies zone based on the type of siliceous rock (such as radiolarian siliceous rock) and geochemical indicators, combined with diagrams such as Fe2O3 / TiO2-Al2O3 / (Al2O3+Fe2O3).

[0043] in, Figure 2This is a major element discrimination diagram for siliceous rock depositional environments. The contents of elements such as Al, Fe, Si, and Ti obtained from sample testing and analysis are calculated according to the formulas of the horizontal and vertical axes and then plotted on the diagram. The depositional environment represented by the plotted area is the formation environment of the siliceous rock. Figure 3 This is a La-Th-Sc element discrimination diagram for siliceous rock depositional environments. The contents of La, Th, and Sc obtained from sample testing and analysis are plotted on this discrimination diagram. The depositional environment represented by the plotted area is the formation environment of the siliceous rock.

[0044] Step (e) is result verification and output, which specifically includes: cross-validation indicators and graphical results, forming a report containing basic information, test data, discrimination process and final conclusion.

[0045] This invention firstly integrates four core indicators—major elements, trace elements, rare earth elements, and Si isotopes—through multi-indicator synergistic discrimination, effectively avoiding interference from diagenesis and terrigenous incorporation of single indicators, and solving the problem of multiple interpretations in traditional methods. This significantly improves the accuracy of distinguishing between three types of genesis and five types of sedimentary environments. Secondly, relying on standardized operating procedures, it clarifies sample collection, pretreatment, testing processes, and data calculation specifications, and unifies instrument precision requirements and particle size control standards (200-400 mesh ≥ 90%), thereby ensuring repeatable operations and strong comparability of results across different laboratories. Furthermore… For hydrothermal-biogenic composite siliceous rocks, this invention uses the relative magnitudes of hydrothermal and biogenic scores, supplemented by quantitative indicators such as silicon isotopes, to semi-quantitatively evaluate the contribution ratio of hydrothermal and biogenic silica. This provides a new technical means for the fine classification of such complex-genetic siliceous rocks. Finally, this invention takes into account both basic research and application needs. It considers the need for fine reconstruction of tectonic environments and paleooceanic conditions in scientific research, while also taking into account practical applications in geological prospecting and resource evaluation. It has both theoretical and applied value and is suitable for widespread use in geological research and exploration at different scales.

[0046] Furthermore, this invention, through comprehensive analysis of multiple indicators such as major, trace, and rare earth elements, combined with cross-validation using various diagrams, can effectively distinguish between hydrothermal sedimentary, biogenic, and hydrothermal-biogenic composite siliceous rocks, significantly reducing the ambiguity and subjectivity of traditional single-indicator discrimination. Based on this, through elemental ratio and graphical analysis, it can accurately determine sedimentary environments such as continental margins and ocean basins. Simultaneously, it standardizes sample collection, pretreatment, testing methods, and indicator calculations, eliminating the need for special or difficult-to-obtain instruments and equipment, facilitating implementation in different laboratories, thereby improving data comparability and operational efficiency. Moreover, this invention can not only be used for paleoenvironmental and paleotectonic reconstruction in basic geological research, but also provide reliable mineralization background judgment criteria for resource exploration of iron ore deposits and polymetallic sulfide deposits associated with siliceous rocks, demonstrating broad application prospects.

[0047] In the optional embodiments of the present invention, the preferred method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis is as follows: (1) Sampling: Select fresh outcrops / cores, avoid interference areas, collect 4 samples ≥100g and record basic information.

[0048] (2) Pretreatment: 1. Sample surface treatment: Use sandpaper to polish and remove the oxide layer and contaminants, use deionized water for ultrasonic cleaning to remove dust and salt adhering to the surface, place in an oven to dry, and cool to room temperature; 2. Coarse crushing and impurity removal: The sample is coarsely crushed to about 0.3 cm using a corundum jaw crusher. Visible carbonate veins, fine quartz veins and metallic mineral impurities are removed using a binocular microscope to ensure sample purity. 3. Fine grinding and particle size control: Take coarsely crushed samples and grind them to 300 mesh using an agate ball mill to avoid uneven particle size leading to test errors; 4. Preservation and protection: Dispense the ground sample into polyethylene sample bottles, label them, and store them in a desiccator containing blue silica gel for 48 hours to avoid moisture and contamination.

[0049] (3) Multi-dimensional indicator testing: Major element determination: 1. Weigh approximately 3g of sample and place it in a pretreated porcelain crucible (weigh the empty crucible mass m0). Bake at 100℃ in an oven for 2 hours. After removal, store in a desiccator with blue silica gel. After the sample has completely cooled, weigh the combined weight of the sample and crucible m1. 2. Remove the porcelain crucible containing the sample and place it in a muffle furnace. Heat to 950℃ and ignite for 2 hours. Remove, cool slightly, and place in a desiccator to cool for 2.5 hours. Weigh the combined weight of the sample and crucible m2. Pour the sample into a clean plastic bag (to be used as an XRF glass slide). 3. Weigh 0.57g of the ignited sample and mix it with 8 times the amount of Li2B4O7 flux (mass ratio 1:8). Add 10 drops of 10% LiBr release agent and place in a platinum crucible. Melt in a melting furnace at 1150℃ to form a glass slide for XRF determination of major elements in the sample.

[0050] Trace element test: 1. Accurately weigh (50 ± 1) mg of the dried powder sample and place it in a clean Teflon crucible; 2. Moisten the sample with 1-2 drops of high-purity water, then add 1 mL of HNO3 and 1 mL of HF in sequence, and gently shake the Teflon crucible to ensure that the sample is completely mixed with the acid; 3. Place the Teflon crucible in a steel sleeve, tighten it, and place it in an oven at (190 ± 5) ℃ for about 48 h; 4. Remove the sample from the oven, and after the Teflon crucible has cooled, open the lid and place it on a hot plate at 115 ℃ to evaporate to dryness. When the sample is evaporated to a wet salt state, add 1 mL of HNO3 and evaporate to dryness again; 5. Add 1 mL of H2O, 1 mL of HNO3, and 1 mL of 5% HNO3, then place the Teflon crucible in the steel sleeve again, tighten it, and place it in an oven at (190 ± 5) ℃ for about 12 h; 6. Transfer the solution to a polyethylene plastic bottle with φ = 2% HNO3 and add 1 A mixed internal standard of In and Ru, at a concentration of 1 mL and 1 μg / g, was diluted to approximately 100 g and stored in a sealed container for ICP-MS testing.

[0051] Rare earth element testing: Take the above trace element test solution and use ICP-MS to test the contents of La, Ce, Eu, Yb and Lu. Before the test, use PAAS standard material to adjust the instrument parameters to ensure the sensitivity of rare earth element detection.

[0052] Isotope testing: Weigh the ground sample, place it in a quartz tube, add HF solution, dissolve it in an 80℃ water bath, and separate the Si element using ion exchange resin; use an isotope ratio mass spectrometer to measure δ. 30 Si value.

[0053] After the test is completed, all derived indicators will be calculated using the same set of formulas.

[0054] The formula is as follows: δCe =Ce / Ce =2Ce N / (La N +Pr N ), where N is the chondrite-normalized value of an element, that is, the measured concentration of a certain element in the sample divided by the reference concentration of that element in the chondrite standard; δEu =Eu / Eu =2Eu N / (Sm N Gd N ), where N is the chondrite-normalized value of an element, that is, the measured concentration of a certain element in the sample divided by the reference concentration of that element in the chondrite standard; ΣREE: The total concentration of all rare earth elements in the sample; δ 30Si = [( 30 Si / 28 Si)sample / ( 30 Si / 28 Si)standard - 1] ×1000‰.

[0055] (4) Genetic identification: Based on the calculation results of major, trace, and rare earth elements, and in accordance with the preset index combination and threshold range of this invention (Table 1), the hydrothermal genesis score and biological genesis score are calculated to preliminarily determine the gene type. The sample is then plotted on the Al-Fe-Mn triangular diagram (…). Figure 1 The results of the cause determination are verified graphically and corrected.

[0056] (5) Determination of sedimentary environment: Based on the type of siliceous rock (radiolar siliceous rock, etc.) and geochemical indicators (Tables 2 and 3), combined with diagrams such as Fe2O3 / TiO2-Al2O3 / (Al2O3+Fe2O3) ( Figure 2 and Figure 3 ), determine the corresponding phase band.

[0057] (6) Results verification and output: cross-validation indicators and graphical results are used to form basic information, test data, discrimination process and final conclusion.

[0058] Based on the above embodiments, and more preferably, the present invention provides direct evidence for the genesis of siliceous rocks by directly measuring the physicochemical parameters of diagenetic and ore-forming fluids.

[0059] When the genetic type determination result output in step (c) includes hydrothermal or complex genetic origin, it also includes: preparing thin sections of fluid inclusions in siliceous rocks, measuring the homogenization temperature and salinity of the fluid inclusions therein, and further confirming the hydrothermal origin and fluid properties based on the homogenization temperature and salinity range, and assessing the intensity or depth of hydrothermal activity.

[0060] Specifically, the process is as follows: (1) Sample selection and preparation: Target samples for preparing thin sections of fluid inclusions in siliceous rocks: Prioritize siliceous rocks that may be associated with hydrothermal activity, such as those with special structures like brecciated, crust-like, vein-like, or pore-filled structures. These structures are often products of hydrothermal fluid activity.

[0061] Sample preparation: The selected sample is prepared into a double-polished fluid inclusion thin film (preferably 0.1-0.3 mm thick) for microthermometry observation.

[0062] (2) Microthermometer Experiment Measurement parameters: Freezing point temperature (Tm): The inclusion is cooled until ice crystals form inside the cavity, then slowly heated, and the temperature at which the last ice crystal completely melts is precisely recorded. This temperature is used to calculate salinity.

[0063] Homogenization temperature (Th): The inclusion is heated, and the changes in its gas and liquid phases are observed. The temperature at which the bubbles disappear and the contents of the inclusion are homogeneous into a single liquid phase (or gas phase) is recorded. This temperature represents the lowest formation temperature at which the fluid is trapped.

[0064] (3) Data calculation: Salinity calculation: Salinity is calculated using the standard formula corresponding to the NaCl-H2O system, based on the measured freezing point depression (Tm). The Bodnar (1993) formula is adopted: Salinity (wt% NaCl eq.) = 1.78Tm - 0.0442 × Tm 2 + 0.000557 × Tm 3 .

[0065] Homogenization temperature (Th): The measured value is used directly, and the unit is degrees Celsius (°C).

[0066] Regarding the discriminant indicators and geological interpretation: In some preferred embodiments, the homogenization temperature (Th) is used to determine the intensity of hydrothermal activity and / or the depth of the hydrothermal source, including: When the homogenization temperature is 50-80℃, it indicates a low-temperature diagenetic environment or a fluid with a temperature similar to that of normal seawater. This is often seen in burial diagenesis or non-hydrothermal formation. A homogenization temperature of 80-150℃ strongly indicates hydrothermal activity. Higher temperatures generally indicate greater intensity or deeper origin of hydrothermal activity. When the homogenization temperature is above 150℃, it represents a medium- to high-temperature hydrothermal event, which may be closely related to magmatic activity or deep circulating hot water.

[0067] In some preferred embodiments, the salinity (wt% NaCl eq.) is used to determine the source nature and / or evolution process of diagenetic fluids, including: When the salinity is close to that of modern seawater (~3.5%), it indicates that the fluid source is mainly seawater or has been thoroughly mixed with seawater. When the salinity is significantly higher than that of modern seawater, the indicator fluid has undergone intense evaporation and concentration or has been mixed with high-salinity formation water (brine); When salinity is significantly lower than that of modern seawater, it indicates the influence of atmospheric precipitation or freshwater.

[0068] In some preferred embodiments, the hydrothermal properties can be further determined by combining salinity with temperature. For example, medium-high temperature, medium-low salinity fluids may be magmatic hydrothermal fluids or metamorphic hydrothermal fluids; medium-low temperature, high salinity fluids may be building water or basin brine.

[0069] In this invention, fluid inclusion homogenization temperature and salinity analysis can provide direct temperature and compositional evidence of ore-forming fluids. The fluid inclusion results are then compared with Al / (Al+Fe+Mn) ratios, rare earth element patterns (especially the Eu anomaly), and silicon isotope (δ¹⁰) values. 30 Combined with other geochemical indicators such as Si, when inclusion data show medium-to-high temperature hydrothermal characteristics, and geochemical indicators simultaneously show hydrothermal signals (such as low Al / (Al+Fe+Mn), positive Eu anomaly, and low δ), the inclusions are considered auspicious. 30 When Si), it can be definitively determined that the siliceous rock is of hydrothermal origin, and its depositional environment can be reconstructed as a submarine hydrothermal vent system or a region strongly influenced by hydrothermal vents.

[0070] Furthermore, based on the determination of hydrothermal origin, the analysis of homogenization temperature and salinity of fluid inclusions in siliceous rocks can further assess the intensity or depth of hydrothermal activity (the higher the temperature, the greater the intensity or depth) or the fluid properties (seawater, high-salinity formation water, or freshwater) in the siliceous sedimentary environment.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis, characterized in that, include: (a) Pre-treating the siliceous rock sample to obtain the powder sample to be tested; (b) The major elements, trace elements, rare earth elements and silicon isotopes of the powder sample to be tested are tested to obtain the corresponding element contents; (c) Based on the data obtained in step (b), calculate and obtain the genetic parameters that characterize the genetic type of siliceous rocks, and then output the genetic type determination result according to the preset genetic type discrimination system; (d) Based on the data obtained in step (b), calculate and obtain the environmental parameters characterizing the siliceous rock depositional environment, and then output the depositional environment determination results according to the preset depositional environment discrimination system; (e) Perform comprehensive analysis and cross-validation on the judgment results of steps (c) and (d) to form the final judgment conclusion.

2. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 1, characterized in that, The cause type discrimination system includes at least one classification rule based on a preset threshold range and at least one verification method based on a diagram.

3. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 1, characterized in that, The genetic types include one or more of hydrothermal, biogenic, and complex genetic types; Preferably, the genetic parameters include silicon content, aluminum content, titanium content, uranium content, thorium content, zirconium content, cerium content, europium content, europium anomaly, cerium anomaly, uranium-thorium ratio, the ratio of aluminum to the total aluminum-iron-manganese content, and silicon isotope δ¹⁴. 30 One or more of the Si values; Preferably, the parameters for determining the hydrothermal origin include: silicon content of 91.0~99.8 wt%, aluminum content ≤1.5 wt%, titanium content ≤0.06 wt%, uranium-thorium ratio ≥2.99, zirconium content ≤85 μg / g, total rare earth element content ≤51.04 μg / g, europium anomaly ≥1.04, cerium anomaly 0.66~0.72, and silicon isotope δ 30 The Si value is -0.29 to -0.25‰, and the ratio of aluminum to the total amount of aluminum, iron, and manganese is ≤0.40; Preferably, the parameters for determining the biogenicity include: silicon content of 85.0~95.0 wt%, aluminum content ≥3.0 wt%, titanium content ≥0.10 wt%, uranium-thorium ratio ≤0.25, zirconium content ≥100 μg / g, total rare earth element content ≥150 μg / g, europium anomaly value of 0.90~1.05, cerium anomaly value of 1.02~1.54, and silicon isotope δ 30 The Si value is 1.8~1.9‰, and the ratio of aluminum to the total amount of aluminum, iron and manganese is ≥0.60; Preferably, the parameters for determining the composite origin include: silicon content of 88.0~96.0 wt%, aluminum content of 1.5~3.0 wt%, titanium content of 0.06~0.10 wt%, uranium-thorium ratio of 0.25~2.99, zirconium content of 85~100 μg / g, total rare earth element content of 51.04~150 μg / g, europium anomaly of 0.95~1.10, cerium anomaly of 0.72~1.02, and silicon isotope δ 30 The Si value is -0.25 to 1.8‰, and the ratio of aluminum to the total amount of aluminum, iron, and manganese is 0.40 to 0.

60.

4. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 1, characterized in that, The graph-based verification method in the genetic type discrimination system includes: projecting the calculated genetic parameters onto an Al-Fe-Mn triangular diagram, a rare earth element distribution pattern diagram, or an Eu-Ce anomaly relationship diagram, and outputting the corrected genetic type judgment result based on the region where the projected points are located.

5. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 1, characterized in that, The sedimentation environment discrimination system includes at least one classification rule based on a preset threshold range and at least one verification method based on a diagram.

6. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 1, characterized in that, The environmental parameters include one or more of the following: the ratio of aluminum to total aluminum, iron, and manganese; cerium anomaly; yttrium-holmium ratio; manganese oxide to titanium dioxide mass ratio; principal element triangular diagram coordinate values; and rare earth element ternary diagram coordinate values. Preferably, the siliceous rock depositional environment includes one or more of the following: mid-ocean ridges, continental margins, ocean basins, and ocean islands; Preferably, the parameters for determining the mid-ocean ridge include a ratio of aluminum to total aluminum, iron, and manganese of approximately 0.00819, a cerium anomaly value of <0.55, a yttrium-holmium ratio of 50-60, and a manganese oxide to titanium dioxide mass ratio of 0.5-3.

5. Preferably, the parameters for determining the continental margin include: the ratio of aluminum to the total amount of aluminum, iron, and manganese is approximately 0.319, the cerium anomaly value is <0.55, the yttrium-holmium ratio is 50-60, and the mass ratio of manganese oxide to titanium dioxide is 0.5-3.

5. Preferably, the parameters for determining the ocean basin and ocean islands include: the ratio of aluminum to the total amount of aluminum, iron and manganese is approximately 0.619, the cerium anomaly value is 0.9~1.3, the yttrium-holmium ratio is approximately 28, and the mass ratio of manganese oxide to titanium dioxide is <0.

5.

7. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 5, characterized in that, The graph-based verification method in the sedimentary environment discrimination system includes: plotting the calculated environmental parameters onto a major element triangular diagram or a La-Th-Sc rare earth element ternary diagram, and outputting the corrected sedimentary environment judgment result based on the region where the plotted points are located.

8. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 1, characterized in that, When the genetic type determination result output in step (c) includes hydrothermal or complex genetic origin, it also includes: preparing thin sections of fluid inclusions in siliceous rocks, measuring the homogenization temperature and salinity of the fluid inclusions therein, and further confirming the hydrothermal origin and fluid properties based on the homogenization temperature and salinity range, and assessing the intensity or depth of hydrothermal activity.

9. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 8, characterized in that, The homogenization temperature is used to determine the intensity of hydrothermal activity and / or the depth of the hydrothermal source, including: When the homogenization temperature is 50-80℃, it indicates that the fluid was formed in a low-temperature diagenetic environment or a fluid with a temperature similar to that of seawater. When the homogenization temperature is 80-150℃, it indicates the presence of hydrothermal activity. The higher the homogenization temperature, the greater the intensity of the hydrothermal activity or the deeper its source. When the homogenization temperature is above 150°C, it indicates a medium- to high-temperature hydrothermal event, representing a connection to magmatic activity or deep circulating hot water.

10. The method for determining the genesis and sedimentary environment of siliceous rocks using multi-index comprehensive analysis according to claim 8, characterized in that, The salinity is used to determine the source nature and / or evolution process of diagenetic fluids, including: When the salinity is close to that of modern seawater, the indicator fluid mainly originates from seawater or has been thoroughly mixed with seawater; When the salinity is significantly higher than that of modern seawater, it indicates that the fluid has undergone evaporation and concentration or mixed with high-salinity formation water; When the salinity is significantly lower than that of modern seawater, it indicates that the fluid is affected by atmospheric precipitation or freshwater.

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