Method for judging paleoenvironment based on coupling of carbonate cathodoluminescence and trace elements

Abstract

The application belongs to the technical field of geological exploration and geochemical analysis, and particularly relates to a paleoenvironment discrimination method based on coupling of carbonate rock cathodoluminescence and trace elements. The paleoenvironment discrimination method based on coupling of carbonate rock cathodoluminescence and trace elements is as follows: the content of trace elements in the same mineral micro-area of a carbonate rock sample to be measured is obtained, the carbonate rock sample to be measured is grouped according to a vanadium-chromium ratio V / Cr and a cerium abnormal value Ce / Ce*, and is divided into an oxidation group or a reduction group; the corresponding paleoenvironment discrimination index of each group is calculated according to the grouping result, compared with a preset determination threshold, and the paleoenvironment category to which the carbonate rock sample to be measured belongs is identified; and the application provides a more reliable and efficient quantitative discrimination tool for industrial applications such as sequence stratigraphic division and reservoir facies belt prediction.

Description

Technical Field

[0001] This invention belongs to the field of geological exploration and geochemical analysis technology, specifically relating to a paleoenvironmental discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks. Background Technology

[0002] In the field of geological exploration, reconstructing paleoenvironmental parameters (such as paleowater depth, paleosalinity, and redox conditions) using the geochemical characteristics of carbonate rocks has always been a research focus. Traditional methods often rely on isolated identification using a single or a few classic geochemical indicators (such as Sr / Ba and Mn / Fe ratios), supplemented by qualitative observations using cathodoluminescence. However, these methods face a series of technical bottlenecks in practical applications, severely limiting their accuracy and reliability. The core of the current technical predicament lies in the mixing of information sources, the qualitative limitations of technical means, and the interference of diagenetic superposition effects, resulting in insufficient fidelity in the extraction of paleoenvironmental signals.

[0003] The primary limitation of existing technologies stems from the lack of representativeness in geochemical data. Whole-rock powder analysis mixes and dissolves components of different origins and phases in carbonate rocks (such as primary sedimentary components, early cement, and late fracture infill), and the resulting trace element ratios (such as Sr / Ba) or rare earth element distribution patterns are essentially mixed signals from multiple geological processes. This mixing effect blurs the boundary between the original sedimentary environment and subsequent diagenetic alteration, leading to fundamental uncertainties in paleoenvironmental identification based on such data. Although in-situ micro-area analysis techniques such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) can achieve spatial positioning analysis to some extent, if they are not accurately correlated with the microscopic characteristics of specific mineral fabrics, it is still difficult to effectively extract paleoenvironmental information from complex diagenetic superposition sequences, and the analysis results may still represent the combined effects of multiple fluid phases.

[0004] Secondly, the application of cathodoluminescence technology is currently still in the qualitative descriptive stage, lacking quantitative standards, which greatly limits its potential for effective coupling with geochemical data. The cathodoluminescence intensity index and color are mainly controlled by the Mn²⁺ / Fe²⁺ ratio in the mineral lattice, serving as a direct indicator of the redox state of diagenetic fluids. However, current research generally relies on operator visual observation for grading (e.g., "strong luminescence," "weak luminescence"), a highly subjective process that fails to establish a mathematical relationship between luminescence characteristics and elemental content. This qualitative approach makes it difficult to integrate as a key variable into quantitative discrimination models, thus hindering its potential in distinguishing different geological environments (e.g., both extremely shallow water oxidative environments and deep water oxygen-deficient environments exhibit "no luminescence"). The barriers between these technologies lead to the isolated use of cathodoluminescence and geochemical data, lacking a systematic multidimensional information fusion model.

[0005] The combination of intense diagenetic alteration and the lack of fusion of multi-technology data results in insufficient accuracy of paleoenvironmental discrimination models. Carbonate rocks undergo multiple phases of fluid alteration during their burial history, which can severely obscure or distort the original sedimentary signals. For example, the influence of hydrothermal fluids in deep reservoirs can cause rare earth element distribution patterns to deviate from typical marine characteristics. When using a single indicator (such as Ce anomaly) for paleoenvironmental discrimination, this superposition effect introduces significant ambiguity. Existing models largely rely on empirical threshold judgments and lack the ability to correct for multiple phases of diagenesis, which is precisely the gap in current technology. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a quantitative method that couples cathodoluminescence microscopic features with in-situ trace element data. By establishing a comprehensive parameter model to eliminate ambiguity, it enables the discrimination of paleoenvironmental parameters such as paleowater depth. This method proposes a paleoenvironmental discrimination method based on the coupling of cathodoluminescence and trace element data in carbonate rocks.

[0007] The technical solution of this invention is as follows: A paleoenvironmental discrimination method based on the coupling of cathodoluminescence and trace element analysis of carbonate rocks is as follows: The trace element content of the carbonate rock sample to be tested in the same mineral micro-region is obtained. Based on the vanadium-chromium ratio (V / Cr) and the cerium anomaly (Ce / Ce*), the paleoenvironmental background of the carbonate rock sample to be tested is grouped into oxidation group or reduction group. The paleoenvironmental discrimination index corresponding to each group is calculated based on the grouping results and compared with the preset judgment threshold to identify the paleoenvironmental category to which the carbonate rock sample to be tested belongs. The specific calculation process for the paleoenvironment discrimination index is as follows: Oxidation group discriminant index PDI Oxic =A1·Y / Ho·(1+α·ICL)+A2·Ga / Al·(1-β·ICL)+C1; Reduced group discriminant index (PDI) Redox =B1·(La / Yb) N ·1 / (1+γ·ICL)+B2·V / Cr·(1+δ·(1-ICL))+C2; In the formula: ICL is the cathodic luminescence intensity index; A1, A2, B1, B2, C1, C2, α, β, γ, and δ are all preset model parameters; Y / Ho is the yttrium / holmium ratio, Ga / Al is the gallium / aluminum ratio, and (La / Yb) N The lanthanum-ytterbium ratio is normalized for chondrites; the cerium anomaly Ce / Ce* is the ratio of the actual cerium content Ce to the theoretical cerium content Ce*.

[0008] The specific identification process of the paleoenvironmental category to which the carbonate rock sample to be measured belongs is as follows: If the oxidation group discrimination index PDI Oxic < TH1, it is identified as a tidal flat environment; TH1 ≤ oxidation group discrimination index PDI Oxic < TH2, it is identified as a restricted shallow sea environment; if the oxidation group discrimination index PDI Oxic ≥ TH2, it is identified as an open shallow sea environment; If the reduction group discrimination index PDI Redox < TH3, it is identified as a restricted shelf environment; PDI Redox ≥ TH3, it is identified as a deep sea shelf environment; Among them, TH1, TH2, and TH3 are preset determination thresholds, TH1 = 0.20 - 0.30, TH2 = 0.60 - 0.70, TH3 = 0.35 - 0.45. Preferably, TH1 = 0.25, TH2 = 0.65, TH3 = 0.40.

[0009] The method for obtaining the cathodoluminescence intensity index ICL is as follows: Obtain the cathodoluminescence digital image of the carbonate rock sample to be measured, and measure the average gray value Gray of the target area to be measured in the cathodoluminescence digital image sample , the average gray value Gray of the background area dark and the average gray value Gray of the standard sample under the same test conditions standard ; The cathodoluminescence intensity index ICL is calculated by the formula ICL = (Gray sample - Gray dark ) / (Gray standard - Gray dark ).

[0010] The specific process of grouping the carbonate rock sample to be measured according to the paleoenvironmental background is as follows: If the vanadium-chromium ratio V / Cr < T1 and the cerium anomaly value Ce / Ce* < 0.95, the carbonate rock sample to be measured is an oxidation group; otherwise, it is a reduction group; where T1 is the preset first redox threshold. Preferably, the value range of the preset first redox threshold T1 is 1.8 - 2.2.

[0011] The specific range of the preset model parameters is: A1=0.30~0.40, A2=0.20~0.30, B1=0.25~0.35, B2=0.15~0.25, C1=-0.20~0.20, C2=-0.30~0.30, α=0.5~0.7, β=0.7~0.9, γ=0.3~0.5, δ=0.6~0.8. Preferably, A1=0.35, A2=0.25, B1=0.30, B2=0.20, C1=-0.15, C2=-0.10, α=0.6, β=0.8, γ=0.4, δ=0.7.

[0012] The trace elements include: vanadium (V), chromium (Cr), cerium (Ce), yttrium (Y), holmium (Ho), gallium (Ga), aluminum (Al), lanthanum (La), and ytterbium (Yb). The trace element content is obtained by in-situ trace element analysis of the same region where the cathodoluminescence of the carbonate rock sample is observed, using laser ablation inductively coupled plasma mass spectrometry (LAMS).

[0013] The technical advantages of this invention are as follows: This invention effectively overcomes the problems of multiple solutions, poor anti-interference ability, and overly simplistic models in traditional methods when identifying paleoenvironments of complex carbonate rocks by coupling quantitative cathodoluminescence characteristics with multiple indicators such as vanadium-chromium ratio (V / Cr), cerium anomaly (Ce / Ce*), and yttrium-holmium ratio (Y / Ho), and innovatively constructs a two-stage model of "redox background grouping - intra-group nonlinear discrimination". This invention achieves deep nonlinear fusion of geochemical and mineralogical information by designing the cathodoluminescence intensity index (ICL) as a dynamically adjustable coefficient, thereby enhancing the robustness of the model. The two-stage model successfully achieves quantitative and precise differentiation of five environmental types: tidal flats, restricted shallow seas, open shallow seas, restricted continental shelves, and deep-sea continental shelves. This provides a more reliable and efficient quantitative discrimination tool for industrial applications such as sequence stratigraphy and reservoir facies prediction. Attached Figure Description

[0014] Figure 1 The sampling locations of 30 carbonate rock samples on the cross section are shown in the embodiments of the present invention.

[0015] Figure 2 These are cathodoluminescence images and test locations for five types of paleoenvironments in embodiments of the present invention. Detailed Implementation

[0016] Example 1 – A paleoenvironmental discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks, the method is as follows: Step 1: Acquire cathodoluminescence digital images of the carbonate rock sample to be tested to calculate its cathodoluminescence intensity index (ICL); Step 2: Obtain the trace element contents of the same mineral micro-region where the carbonate rock sample to be tested is located, and calculate: vanadium-chromium ratio V / Cr, cerium anomaly Ce / Ce*, yttrium-holmium ratio Y / Ho, gallium-aluminum ratio Ga / Al, and chondrite-normalized lanthanum-ytterbium ratio (La / Yb) N ; Step 3: Grouping of paleoenvironmental backgrounds: If the vanadium-chromium ratio V / Cr < T1 and the cerium anomaly Ce / Ce* < 0.95, the carbonate rock sample to be tested belongs to the oxidation group; otherwise, it belongs to the reduction group; Step 4: Calculate the paleoenvironmental discrimination index and identify the paleoenvironmental category to which the carbonate rock sample to be tested belongs: If the carbonate rock sample to be tested belongs to the oxidation group, then the oxidation group discrimination index PDI Oxic = A1·Y / Ho·(1 + α·ICL) + A2·Ga / Al·(1 - β·ICL) + C1; If the oxidation group discrimination index PDI Oxic < TH1, it is identified as a tidal flat environment; TH1 ≤ oxidation group discrimination index PDI Oxic < TH2, it is identified as a restricted shallow sea environment; If the oxidation group discrimination index PDI Oxic ≥ TH2, it is identified as an open shallow sea environment; If the carbonate rock sample to be tested belongs to the reduction group, then the reduction group discrimination index PDI Redox = B1·(La / Yb) N ·1 / (1 + γ·ICL) + B2·V / Cr·(1 + δ·(1 - ICL)) + C2; If the reduction group discrimination index PDI Redox < TH3, it is identified as a restricted shelf environment; PDI Redox ≥ TH3, it is identified as a deep sea shelf environment.

[0017] Example 2 - A paleoenvironmental discrimination method based on the coupling of cathodoluminescence and trace elements of carbonate rocks, the method is as follows: Step 1: Obtain the cathodoluminescence digital image of the carbonate rock sample to be tested to calculate its cathodoluminescence intensity index ICL; ICL = (Gray sample - Gray dark ) / (Gray standard - Gray dark ); Step 2: Obtain the trace element contents of the same mineral micro-region where the carbonate rock sample to be tested is located, and calculate: vanadium-chromium ratio V / Cr, cerium anomaly Ce / Ce*, yttrium-holmium ratio Y / Ho, gallium-aluminum ratio Ga / Al, and chondrite-normalized lanthanum-ytterbium ratio (La / Yb) N ; Step 3: Paleoenvironmental background grouping: If the vanadium-chromium ratio V / Cr < 2.0 and the cerium anomaly value Ce / Ce* < 0.95, the carbonate rock sample to be tested belongs to the oxidation group; otherwise, it belongs to the reduction group; Step 4: Calculate the paleoenvironmental discrimination index and identify the paleoenvironmental category to which the carbonate rock sample to be tested belongs: If the carbonate rock sample to be tested belongs to the oxidation group, then the oxidation group discrimination index PDI Oxic = A1·Y / Ho·(1 + α·ICL) + A2·Ga / Al·(1 - β·ICL) + C1; If the oxidation group discrimination index PDI Oxic < TH1, it is identified as a tidal flat environment; TH1 ≤ oxidation group discrimination index PDI Oxic < TH2, it is identified as a restricted shallow sea environment; If the oxidation group discrimination index PDI Oxic ≥ TH2, it is identified as an open shallow sea environment; Among them, A1 = 0.30 - 0.40, A2 = 0.20 - 0.30, C1 = -0.20 - 0.20, α = 0.5 - 0.7, β = 0.7 - 0.9; Preferably, PDI Oxic = 0.35·Y / Ho·(1 + 0.6·ICL) + 0.25·Ga / Al·(1 - 0.8·ICL) - 0.15; Among them, TH1 = 0.20 - 0.30, TH2 = 0.60 - 0.70; Preferably, TH1 = 0.25, TH2 = 0.65, TH3 = 0.40; Furthermore, if the oxidation group discrimination index PDI Oxic < 0.25, it is identified as a tidal flat environment; 0.25 ≤ oxidation group discrimination index PDI Oxic < 0.65, it is identified as a restricted shallow sea environment; If the oxidation group discrimination index PDI Oxic ≥ 0.65, it is identified as an open shallow sea environment; If the carbonate rock sample to be tested belongs to the reduction group, then the reduction group discrimination index PDI Redox = B1·(La / Yb) N ·1 / (1 + γ·ICL) + B2·V / Cr·(1 + δ·(1 - ICL)) + C2; If the reduction group discrimination index PDI Redox < TH3, it is identified as a restricted continental shelf environment; PDI Redox ≥ TH3, it is identified as a deep sea continental shelf environment; Among them, B1 = 0.25 - 0.35, B2 = 0.15 - 0.25, C2 = -0.30 - 0.30, γ = 0.3 - 0.5, δ = 0.6 - 0.8; Preferably, PDI Redox = 0.30·(La / Yb)N ·1 / (1+0.4·ICL)+0.20·V / Cr·(1+0.7·(1-ICL))-0.10; Wherein, TH3 = 0.35~0.45; preferably, TH3 = 0.40; Furthermore, if the discriminant index PDI of the reduced group is... Redox <0.40, identified as a restricted shelf environment; PDI Redox ≥0.40 indicates a deep-sea shelf environment.

[0018] Example 3 – Based on Example 2, it also includes: The method for obtaining the cathodoluminescence intensity index (ICL) is as follows: acquire a cathodoluminescence digital image of the carbonate rock sample to be tested, and measure the average gray value (Gray) of the target area in the cathodoluminescence digital image. sample Average grayscale value of the background area (Gray) dark and the average gray value of the standard sample under the same test conditions (Gray) standard ; through the formula ICL=(Gray sample -Gray dark ) / (Gray standard -Gray dark The cathodic luminescence intensity index ICL was calculated.

[0019] Example 4 – Based on Example 3, it also includes: In-situ trace element analysis was performed on the same area where the cathodoluminescence of the carbonate rock sample was observed. The contents of vanadium (V), chromium (Cr), cerium (Ce), yttrium (Y), holmium (Ho), gallium (Ga), aluminum (Al), lanthanum (La), and ytterbium (Yb) were obtained by laser ablation inductively coupled plasma mass spectrometry.

[0020] A specific experimental case—In oil and gas exploration in the Ordos Basin, paleoenvironmental reconstruction of the Majiagou Formation (Mawu Member) carbonate reservoir has always been a key challenge restricting the accuracy of reservoir prediction. Traditional methods mainly rely on qualitative descriptions of sedimentary structures or single geochemical indicators (such as the strontium / barium ratio) for identification, which has significant limitations: First, whole-rock geochemical analysis mixes signals from different diagenetic stages, making it impossible to distinguish the influence of the original sedimentary environment and the superimposed alteration by later diagenetic fluids; second, cathodoluminescence observations are mostly qualitative descriptions, lacking quantitative correlation with geochemical parameters; third, both deep-water oxygen-depleted environments and extremely shallow-water exposed environments may exhibit "non-luminescence," and traditional methods struggle to effectively distinguish this ambiguity. These shortcomings lead to significant uncertainty in paleoenvironmental identification results, directly affecting the accurate prediction of the distribution patterns of high-quality reservoirs.

[0021] This invention effectively solves the aforementioned technical bottlenecks by coupling quantitative cathodoluminescence characteristics with multi-dimensional geochemical indicators and innovatively constructing a two-stage model of "redox background grouping - intra-group nonlinear discrimination". The method first uses the vanadium-chromium ratio (V / Cr) and the cerium anomaly (Ce / Ce*) to collaboratively determine the redox background, initially classifying the environment into oxidizing and reducing groups. Then, for different backgrounds, discriminant formulas are constructed with the cathodoluminescence intensity index (ICL) as a dynamically adjusted coefficient, achieving quantitative and precise discrimination of five environmental types: tidal flats, restricted shallow seas, open shallow seas, restricted continental shelves, and deep-sea continental shelves. This innovation achieves three major breakthroughs: first, through multi-indicator cross-validation and segmented modeling driven by geological logic, the ambiguity of the discrimination is significantly reduced; second, the cathodoluminescence intensity index (ICL) is deeply integrated as a coefficient function into the discriminant model, achieving quantitative coupling between mineralogical response and geochemical signals; and third, the model possesses stronger resistance to diagenetic interference and high-resolution identification capabilities for complex environmental sequences.

[0022] Specifically, the Majiagou Formation in the Yan'an area of ​​the Ordos Basin will be used as an example for further explanation.

[0023] S1: Thirty fresh carbonate rock samples (numbered MY-01 to MY-30) were systematically collected from a typical outcrop section of the Majiagou Formation, Member 5. These samples were cut, ground, and polished to prepare standard thin sections (approximately 30 μm thick) for subsequent analysis. Each standard thin section was observed using a cathodoluminescence analyzer. The instrument operating conditions were set as follows: accelerating voltage 10 kV, beam current 200 μA. High-resolution cathodoluminescence digital images were acquired for subsequent image analysis. To ensure spatial consistency of the data, in-situ trace element content determination was performed in the same mineral micro-region (e.g., dolomite or calcite crystal) analyzed by cathodoluminescence (FLAR) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The laser beam diameter was set to 50 μm and calibrated using NIST 612 standard glass. The vanadium-chromium ratio (V / Cr), cerium anomaly (Ce / Ce*), yttrium-holmium ratio (Y / Ho), gallium-aluminum ratio (Ga / Al), and chondrite-normalized lanthanum-ytterbium ratio (La / Yb) were calculated. N Values ​​(Table 1); Table 1. Elemental analysis results of 30 carbonate rock samples from the Majiagou Formation in Yan'an area. .

[0024] S2: Calculate the cathodoluminescence intensity index (ICL) and the oxide group discrimination index (PDI). Oxic and the discriminant index PDI of the reduction group Redox ; S2-1: Use image processing software to analyze the grayscale value of the digital image of the cathode emission, and measure the average grayscale value of the area under test (Gray).sample The average gray value (Gray) of the background area of ​​the epoxy resin bonded material was measured. dark (15 in this example). The average gray value of the standard garnet sample measured under the same instrument conditions (Gray) is used. standard (In this embodiment, 200) is used as the baseline. The ICL value of each sample is calculated; the results are shown in Table 1; S2-2: If the vanadium-chromium ratio V / Cr < 2.0 and the cerium anomaly Ce / Ce* < 0.95, then the carbonate rock sample to be tested belongs to the oxidizing group; otherwise, it belongs to the reducing group. For the oxidized group samples, Calculate the oxidation group discriminant index (PDI) Oxic =0.35·Y / Ho·(1+0.6·ICL)+0.25·Ga / Al·(1-0.8·ICL)-0.15; For the reduced group samples, Calculate the reduction group discriminant index (PDI) Redox =0.30·(La / Yb) N ·1 / (1+0.4·ICL)+0.20·V / Cr·(1+0.7·(1-ICL))-0.10.

[0025] S3: Calculate the PDI for each carbonate rock sample. Oxic Value or PDI Redox The value is compared with a preset judgment threshold to identify the paleoenvironment category to which the carbonate rock sample to be tested belongs. For oxidized samples, if the oxidized group discriminant index (PDI) is... Oxic <0.25 indicates a tidal flat environment; 0.25 ≤ PDI (Potential Discriminant Index) indicates an oxidation group environment. Oxic <0.65 indicates a limited shallow marine environment; if the oxidation group discriminant index (PDI) is less than 0.65, it is considered a limited shallow marine environment; Oxic ≥0.65 indicates an open, shallow sea environment; For the reduced group samples, if the discriminant index (PDI) of the reduced group is... Redox <0.40, identified as a restricted shelf environment; PDI Redox ≥0.40 indicates a deep-sea shelf environment. The paleoenvironmental discrimination results are shown in Table 2 below: Table 2 PDI Oxic Value and PDI Redox Value calculation results and recognition results ; In this embodiment, the actual paleoenvironments of 30 carbonate rock samples from the Majiagou Formation in the Yan'an area are shown in Table 2. The prediction results obtained using conventional cathodoluminescence immunoassay, geochemical methods, and the method provided in this invention are shown in Table 3. Based on the comparison with the actual paleoenvironments, the overall accuracy of this method is 96.7%, significantly better than traditional methods (73.3% for conventional cathodoluminescence immunoassay and 83.3% for geochemical methods). Table 3 Comparison of recognition accuracy between conventional methods and this method .

[0026] This method, through multi-source information fusion and quantitative modeling, comprehensively surpasses traditional single-technology approaches, significantly improving the overall accuracy and reliability of paleoenvironment identification, especially solving the identification challenges of complex cases such as tidal flats and open shallow seas. Practical verification shows a >90% agreement rate with drilling data, providing reliable technical support for fine characterization of sedimentary facies and prediction of favorable reservoirs, and achieving good results in frontline production applications.

Claims

1. A paleoenvironmental discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks, characterized in that, The method is as follows: Obtain the trace element contents of the same mineral microzone where the carbonate rock sample to be tested is located. Based on the vanadium-chromium ratio V / Cr and the cerium anomaly value Ce / Ce*, group the carbonate rock samples to be tested for the paleoenvironmental background, and divide them into an oxidation group or a reduction group; calculate the corresponding paleoenvironmental discrimination index for each group according to the grouping results, and compare it with the preset determination threshold to identify the paleoenvironmental category to which the carbonate rock sample to be tested belongs; Among them, the specific calculation process of the paleoenvironmental discrimination index is as follows: Oxidation group discriminant index PDI Oxic =A1·Y / Ho·(1+α·ICL)+A2·Ga / Al·(1-β·ICL)+C1; Reduced group discriminant index (PDI) Redox =B1·(La / Yb) N ·1 / (1+γ·ICL)+B2·V / Cr·(1+δ·(1-ICL))+C2; In the formula: ICL is the cathodoluminescence intensity index; A1, A2, B1, B2, C1, C2, α, β, γ and δ are all preset model parameters; Y / Ho is the yttrium / holmium ratio, Ga / Al is the gallium / aluminum ratio, and (La / Yb) N The lanthanum-ytterbium ratio is normalized for chondrites; the cerium anomaly Ce / Ce* is the ratio of the actual cerium content Ce to the theoretical cerium content Ce*.

2. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 1, characterized in that, The specific identification process of the paleoenvironmental category to which the carbonate rock sample to be tested belongs is as follows: If the oxidation group discrimination index PDI Oxic <TH1, it is identified as a tidal flat environment; TH1 ≤ oxidation group discrimination index PDI Oxic <TH2, it is identified as a restricted shallow sea environment; if the oxidation group discrimination index PDI Oxic ≥TH2, it is identified as an open shallow sea environment; If the reduction group discrimination index PDI Redox <TH3, it is identified as a restricted shelf environment; PDI Redox ≥TH3, it is identified as a bathyal shelf environment; Among them, TH1, TH2, and TH3 are preset determination thresholds, and the values are TH1 = 0.20 - 0.30, TH2 = 0.60 - 0.70, TH3 = 0.35 - 0.

45.

3. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 2, characterized in that, The specific preset determination thresholds are: TH1 = 0.25, TH2 = 0.65, TH3 = 0.

40.

4. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 1, characterized in that, The method for obtaining the cathodoluminescence intensity index (ICL) is as follows: acquire a cathodoluminescence digital image of the carbonate rock sample to be tested, and measure the average gray value (Gray) of the target area in the cathodoluminescence digital image. sample Average grayscale value of the background area (Gray) dark and the average gray value of the standard sample under the same test conditions (Gray). standard ; through the formula ICL=(Gray sample -Gray dark ) / (Gray standard -Gray dark The cathodic luminescence intensity index ICL was calculated.

5. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 1, characterized in that, The specific process of grouping the carbonate rock samples to be tested for the paleoenvironmental background is as follows: If the vanadium-chromium ratio V / Cr < T1 and the cerium anomaly value Ce / Ce* < 0.95, then the carbonate rock sample to be tested is in the oxidation group; otherwise it is in the reduction group; where T1 is the preset first redox threshold.

6. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 5, characterized in that, The value range of the preset first redox threshold T1 is 1.8 - 2.

2.

7. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 1, characterized in that, The specific ranges of the preset model parameters are: A1 = 0.30 - 0.40, A2 = 0.20 - 0.30, B1 = 0.25 - 0.35, B2 = 0.15 - 0.25, C1 = -0.20 - 0.20, C2 = -0.30 - 0.30, α = 0.5 - 0.7, β = 0.7 - 0.9, γ = 0.3 - 0.5, δ = 0.6 - 0.

8.

8. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 7, characterized in that, The specific preset model parameters are: A1 = 0.35, A2 = 0.25, B1 = 0.30, B2 = 0.20, C1 = -0.15, C2 = -0.10, α = 0.6, β = 0.8, γ = 0.4, δ = 0.

7.

9. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 1, characterized in that, The trace elements include: vanadium V, chromium Cr, cerium Ce, yttrium Y, holmium Ho, gallium Ga, aluminum Al, lanthanum La and ytterbium Yb.

10. The paleoenvironment discrimination method based on the coupling of cathodoluminescence and trace elements in carbonate rocks according to claim 9, characterized in that, The method for obtaining the trace element contents is to perform in-situ trace element analysis on the same area where the cathodoluminescence of the measured carbonate rock sample is located, and obtain it by laser ablation inductively coupled plasma mass spectrometry.

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