A method for identifying time scales of ecological environment recovery at different scales after volcanic activity

Abstract

The present invention belongs to the technical field of resource data collection and assessment, and in particular relates to a method for identifying the time scales of ecological environment recovery at different scales after volcanic activity. Based on a variety of analytical test data methods such as major elements and trace elements, the method analyzes changes in the shale sedimentary environment and environmental disturbances caused by sudden events, and establishes a method for identifying the time scales of ecological environment recovery at the centimeter-level and micrometer-level scales of cores and thin sections. This method provides a new approach to calculating the time scale of environmental impacts after volcanic activity. Based on the analysis of changes in the shale sedimentary environment and environmental disturbances caused by sudden environmental events, the method calculates the time scale of shale sedimentary sections during the ecological environment recovery period under the influence of volcanic activity, establishes a comparative scale from ecological environment chaos to stability, clarifies the time depth of the specific environmental impact of volcanic activity, improves the distribution and positioning accuracy of high-organic matter shale, and provides guidance for the exploration of high-quality organic-rich shale layers.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource data collection and evaluation, and relates to a method for identifying time scales of ecological environment recovery at different scales after volcanic activity. Background Art

[0002] Volcanic activity brings material from deep Earth to the surface, causing changes in environmental factors such as climate, ocean water properties (salinity, nutrients, redox properties, etc.), and terrigenous material inputs, disrupting ecosystem stability. Volcanic ash produced by volcanic activity, when deposited into layers, forms bentonite. The mineral content at the lower boundary changes more rapidly than at the upper boundary of the bentonite, indicating that volcanic activity is a rapid environmental event. The initial phase of volcanic activity, characterized by the rapid deposition of large amounts of ash over a short period of time, results in rapid changes in the mineral composition and content of the lower boundary of the bentonite. However, at the end of the volcanic activity, the intensity of the eruption gradually weakens, and the supply of detrital material in the sedimentary environment is restored, resulting in rock layers containing mixed volcanic and terrigenous materials. The mineral composition changes at this stage are relatively slow compared to the lower boundary of the bentonite layer. The thickness of the bentonite layer can be used as a proxy for the intensity of the volcanic activity. The lower boundary of the bentonite is always thinner than the upper boundary, indicating that the timeframe for repairing a damaged ecological environment is much longer than the timeframe for destruction. The greater the intensity of the volcanic activity, the longer it affects the sedimentary environment, and the longer the recovery period required for the ecosystem after the volcanic activity. Over long time scales, the huge amount of igneous rocks formed by large-scale volcanic activities can continue to weather for millions of years. The high primary productivity environment formed produces a large amount of organic matter that falls into the deep, closed and quiet seabed and is deposited together with fine-grained debris to form widely distributed marine organic-rich shales.

[0003] Volcanic activity plays a key role in the evolution of Earth's ecological environment. As a regulatory mechanism of the Earth system, it induces changes in the atmosphere, oceans, and land surface environments. This study precisely pinpoints the timescale of volcanic activity's impact on the ecological environment and clarifies the temporal depth of its subsequent impact. Based on a variety of analytical and testing data, including major and trace element content, carbon and oxygen isotope composition, total organic carbon content, and total sulfur content, a method for identifying ecological recovery timescales at the centimeter-scale in cores and micrometer-scale in thin sections has been established. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a method for identifying the time scales of ecological environment recovery at different scales after volcanic activity.

[0005] The specific technical solutions are as follows:

[0006] S1. Sample the shale interval containing bentonite. Mark the top and bottom of the sample on the side with a white marker. Use an arrow as a marker, with the arrow pointing to the top of the sample.

[0007] S2. Slice and sample the obtained bentonite-containing shale section sample with a sampling interval of 1-5 mm. Then crush the obtained block sample into 200-mesh rock powder. Carefully clean the machine between two sample crushing operations to avoid mixing the two sample powders.

[0008] Preferably, during the sampling process, in order to obtain the required sample more accurately, a micro drill (HANDY-ECO 1000) can be used under a microscope to prepare samples parallel to the laminae, shortening the sampling interval and reducing sample loss. It is important to ensure that when the sampling interval is too small, adjacent samples are not contaminated by powder remaining from the previous sampling point.

[0009] S3. Test the major and trace element contents of the obtained rock powder samples, verify the validity of the obtained element content data, and then select appropriate sedimentary environment geochemical indicators (Table 1) to create sedimentary environment indicator change diagrams based on sample depth, changes in individual element content, and element content combinations;

[0010]

[0011] Preferably, during the test process, the total organic carbon content and total sulfur content tests, carbon isotope and oxygen isotope composition tests can be added to increase the amount of data, which is conducive to improving the accuracy of the obtained bentonite-shale transition zone width data;

[0012] S4. Compare the obtained geochemical indicator data of the shale depositional environment above the bentonite layer to determine the depth of the first data point where the depositional environment indicators above the bentonite layer return to the average level of the environmental indicators during normal shale deposition, and subtract the depth value of the top of the bentonite layer from the depth value to obtain the width of the bentonite-shale transition zone;

[0013] S5. Determine the sedimentation rate values at different spatial locations of the bentonite interval and take the average value as the average sedimentation rate of the entire shale formation;

[0014] Preferably, zircon dating data and shale thickness data of shale deposited stably above the bentonite layer are used to calculate the deposition rate of the shale layer after the volcanic activity sediments were deposited to form the bentonite. The deposition rate value at this time has a unique correspondence with the volcanic activity and has the highest accuracy.

[0015] S6. When the bentonite-shale transition zone was deposited, volcanic material input and terrigenous material input existed simultaneously. 斑脱岩-页岩 / 2 is used as the thickness of the effective sedimentary rock layer during the transition period, and the time scale of ecological environment recovery is calculated using the following formula: ;

[0016] Where, T 生态环境 ——Time scale of ecological environment restoration, Kyr;

[0017] H 斑脱岩-页岩 ——Thickness of the rock layer in the transition area between bentonite layer and shale, cm;

[0018] V 页岩 ——shale sedimentation rate, cm / kyr;

[0019] S7. At a finer scale, samples of the bentonite layer and its upper shale were ground into rock slices with a thickness of 0.03 mm. These slices were tested perpendicular to the laminae using a high-performance micro-area X-ray fluorescence spectrometer (Bruker M4 TORNADO). After data processing, elemental variations in the bentonite layer and its upper shale were observed. Comprehensive judgments were made using multiple elements, such as U, Th, V, Cr, Hg, Ca, Si, Mg, Mo, Ni, Al, Zr, and Hf. The more elements observed, the more accurate the resulting bentonite-shale transition zone width and ecological environment recovery timescale data.

[0020] Preferably, samples of the bentonite layer and its upper shale are ground into rock slices (rock thickness is 0.03 mm) or made into polished block samples, and the sample surface is polished and coated with a platinum film using a precision etching wide-beam argon ion polishing and coating system (Gatan 685). The focused ion beam-electron beam dual-beam system (Focused Ion Beam-Scanning Electron Microscope) of a Zeiss Crossbeam 550 is used to perform an automatic mineral identification and characterization system analysis. Based on the mineral quantitative results, mineral content data is continuously extracted at a data extraction interval of less than 150 μm, and a mineral content distribution map is drawn to determine more precise bentonite-shale transition zone width data, thereby calculating more accurate ecological environment restoration time scale data results.

[0021] The present invention has the following beneficial effects:

[0022] First, the proposed method for identifying the timescale for ecological and environmental recovery after volcanic activity provides a reference for calculating the timescale for recovery from environmental impacts caused by volcanic activity in modern and geological history. Based on a variety of analytical and test data methods, including major and trace elements, total organic carbon content, total sulfur content, carbon isotope composition, and mineral content, the present invention establishes a set of centimeter- to micrometer-scale methods for ecological and environmental recovery after volcanic activity, filling a gap in the relevant art.

[0023] Second, this invention provides a new approach for calculating the timescale of environmental impacts following volcanic activity. By analyzing changes in the shale deposition environment and the environmental disturbances caused by sudden environmental events, the present invention calculates the timescale of shale deposition during the ecological recovery period under the influence of volcanic activity. This establishes a comparative scale from ecological chaos to stability, clarifying the timescale of the specific environmental impacts of volcanic activity.

[0024] Third, volcanic activity, which enriches the ecological environment with nutrients, produces more organic matter. This organic matter settles to the seafloor, where it is deposited alongside fine-grained sediments such as silicate and carbonate mineral particles, forming organic-rich shales. The distribution of bentonite layers, as evidenced by the rock, is strongly correlated with that of organic-rich shale layers. This invention improves the accuracy of locating high-organic-matter-content shales and provides guidance for the exploration of high-quality organic-rich shale intervals. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a method provided by an embodiment of the present invention;

[0026] Figure 2 This is the distribution map of two layers of bentonite in the W well sample;

[0027] Figure 3 This is the evolution diagram of geochemical indicators of W well samples;

[0028] Figure 4 The upper and lower boundary characteristics of bentonite in the sample from Well W;

[0029] Figure 5 This is a graph showing changes in mineral content of samples from Well W. DETAILED DESCRIPTION

[0030] 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 creative efforts are within the scope of protection of the present invention.

[0031] like Figure 1As shown, this implementation method is aimed at the Late Ordovician-Early Silurian Wufeng Formation-Longmaxi Formation bentonite-bearing layers and the shale layers formed thereafter in Well W in the Sichuan Basin to identify the time scale of ecological environment recovery after volcanic activity. The specific implementation steps are as follows:

[0032] S1. Select an organic-rich shale core sample from the Late Ordovician-Early Silurian Wufeng-Longmaxi Formation in the Sichuan Basin, containing bentonite. Use a white marker to mark arrows from bottom to top, with the arrows pointing to the top.

[0033] S2. Cut the core sample perpendicular to the laminae into two equal halves. One half is used to prepare the sample, and the other is kept for future use. Under a microscope, use a micro drill (HANDY-ECO 1000) to prepare the sample powder parallel to the laminae. The sampling interval is 1-5 mm ( Figure 2 After taking a sample, record the corresponding depth of the sample and clean up the remaining powder before preparing the next sample to avoid sample contamination;

[0034] S3. The obtained powder samples were tested for trace element content, total organic carbon content (TOC) and carbon isotope content. Hf content, Zr content and Zr / Cr were used to indicate volcanic activity, Sr / Ba was used to indicate ancient water salinity, and total organic carbon content (TOC), δ 13 C composition, Mo content and Cu content indicate the primary productivity of ancient water bodies, Sr content and Sr / Cu are used to indicate the ancient climate, U / Th, V / Cr, V / (V+Ni) and V / Ni are used to indicate the redox property of ancient water bodies, and a change map of the geochemical indicators of the sedimentary environment is drawn ( Figure 3 );

[0035] S4. Comparing the values of the sedimentary environment geochemical indicators of the bentonite layer with those of the shale, and determining the width of the bentonite-shale transition zone in combination with a variation diagram of the sedimentary environment geochemical indicators of the sample;

[0036] S5. Search the literature for sedimentation rate data of organic-rich shales in the Wufeng-Longmaxi Formation interval corresponding to the sample, and take the average of all sedimentation rate data to determine the sedimentation rate value;

[0037] S6. Take H in the calculation of ecological environment restoration time scale 斑脱岩-页岩 / 2 is used as the thickness of the transition zone rock layer that was effectively deposited during the transition period, and the following formula is used to calculate the time scale of ecological environment recovery after volcanic activity: ;

[0038] Where, T 生态环境 ——Time scale of ecological environment restoration, Kyr;

[0039] H 斑脱岩-页岩 —The thickness of the rock layer in the transition area between the bentonite layer and the shale determined in step S4, in cm;

[0040] V 页岩 ——the sedimentation rate of the shale determined in step S5, cm / kyr;

[0041] Table 2 shows the time scale data results of ecological environment recovery after volcanic activity at the centimeter scale of the core obtained by substituting the data obtained by the embodiment method into the formula;

[0042]

[0043] S7. At a finer micron scale, the obtained bentonite layer and its upper shale samples were ground into rock slices with a thickness of 0.03 mm ( Figure 4 The sample surface was polished and coated with platinum using a precision etching broad-beam argon ion polishing and coating system (Gatan 685). The mineral characteristics were automatically quantitatively analyzed using a focused ion beam-electron beam dual-beam system of a Zeiss Crossbeam 550 scanning electron microscope. The mineral content data were continuously extracted at a data extraction interval of less than 150 μm from the mineral quantitative results to produce a mineral content distribution map ( Figure 5 ), determine more detailed bentonite-shale transition zone width data, and then calculate more accurate ecological environment recovery time scale data results. Table 3 shows the time scale data results of ecological environment recovery after volcanic activity on the thin slice micron scale after substituting the data obtained by the embodiment method into the formula.

[0044]

[0045] Those skilled in the art will understand that the discussion of the above embodiments is merely illustrative and is not intended to limit the scope of the present invention to these examples. Within the spirit of the present invention, the technical features of the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and many other variations exist for the various aspects of the present invention described above, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for identifying the time scales of ecological environment recovery at different scales after volcanic activity, characterized in that: The following steps are involved: S1. Sample a shale interval containing bentonite and mark the top and bottom of the sample on the side of the sample; S2. Slice and sample the obtained bentonite-containing shale section sample at a sampling interval of 1-5 mm, and then crush the obtained block sample into 200-mesh rock powder; S3. Testing the obtained rock powder samples for major and trace element content, verifying the validity of the obtained element content data, and using sedimentary environment geochemical indicators to create sedimentary environment indicator change maps of sample depth, individual element content changes, and element content combinations; S4. Compare the obtained geochemical indicator data of the shale depositional environment above the bentonite layer to determine the depth of the first data point where the depositional environment indicators above the bentonite layer return to the average level of the environmental indicators during normal shale deposition, and subtract the depth value of the top of the bentonite layer from the depth value to obtain the width of the bentonite-shale transition zone; S5. determining the sedimentation rate values of shales at different spatial locations in the bentonite interval, and taking the average value as the average sedimentation rate of the entire shale formation; S6, when deposited in the bentonite-shale transition zone, take H 斑脱岩-页岩 / 2 is used as the thickness of the effective sedimentary rock layer during the transition period, and the time scale of ecological environment recovery is calculated using the following formula: ; Where, T 生态环境 ——Time scale of ecological environment restoration, Kyr; H 斑脱岩-页岩 ——Thickness of the rock layer in the transition area between bentonite layer and shale, cm; V 页岩 ——shale sedimentation rate, cm / kyr; S7. Samples of the bentonite layer and its upper shale were ground into rock slices with a thickness of 0.03 mm. The slices were tested perpendicular to the lamination direction using a high-performance Bruker M4 TORNADO micro-area X-ray fluorescence spectrometer. After data processing, elemental variations in the bentonite layer and its upper shale were observed. A comprehensive analysis using multiple elements was used to determine the width of the bentonite-shale transition zone and the timescale for ecological and environmental recovery.

2. The method for identifying time scales of ecological environment recovery at different scales after volcanic activity according to claim 1, characterized in that: During the slicing sampling process in step S2, a micro drill bit HANDY-ECO 1000 was used under a microscope to prepare samples parallel to the laminae, shortening the sampling interval and reducing sample loss. When continuously sampling adjacent samples, the samples were prevented from being contaminated by the powder remaining at the previous sampling point.

3. The method for identifying time scales of ecological environment recovery at different scales after volcanic activity according to claim 1, characterized in that: In step S3, in addition to the major element and trace element content tests, the total organic carbon content and total sulfur content tests, and the carbon isotope and oxygen isotope composition tests are used to increase the data volume.

4. The method for identifying time scales of ecological environment recovery at different scales after volcanic activity according to claim 1, characterized in that: Step S7 is replaced by: grinding the bentonite layer and its upper shale samples into 0.03 mm thick rock slices or polishing block samples; polishing the sample surfaces using a Gatan 685 wide-beam argon ion polishing and coating system and coating them with a platinum film; performing automatic quantitative analysis of mineral characteristics using a Zeiss Crossbeam 550 scanning electron microscope with a focused ion beam and electron beam dual-beam system; continuously extracting mineral content data from the mineral quantitative results at a data extraction interval of less than 150 μm, creating a mineral content distribution map, determining the width of the bentonite-shale transition zone, and then calculating the ecological environment recovery timescale data results.

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