A provenance analysis method based on measuring Dpar value

Abstract

The present invention provides a provenance analysis method based on measuring Dpar value. By measuring the Dpar value of the fission track of the sedimentary area and the source area sample; then using the multidimensional scaling analysis method to group the obtained Dpar value, obtain grouped data, use the Dpar value as a parameter, match the sedimentary area and the source area with the same Dpar value characteristics of the grouped data to construct a sedimentary area-source area coupling model, it is possible to accurately delineate the source area and its rock type, determine the source of the sediment, and make the provenance analysis more accurate and reliable. Moreover, the provenance analysis method of the present invention only needs to measure the Dpar value of the sample to accurately obtain the provenance analysis result, and there is no need to perform thermal neutron irradiation on the sample during the measurement of the Dpar value, and it takes a short time to obtain the Dpar value, which effectively solves the defects of sending the analysis sample to a nuclear reactor for thermal neutron irradiation or irradiation for a long time and radioactivity in the process of traditional determination of fission track age for provenance analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of material provenance analysis, and in particular to a material provenance analysis method based on measuring a Dpar value. Background Art

[0002] At present, there are provenance analysis techniques such as sedimentology, petrology and mineralogical methods, elemental geochemistry, geochronology, clay mineralogy, fission track method, fossil and biomarker compound method and geophysics method. These methods have some limitations and affect the accuracy of provenance analysis. For example, the statistical workload of sedimentology is large and the results of provenance judgment are vague, and it is impossible to determine the specific location of the provenance area, the properties of the parent rock and other specific information; the judgment of provenance by petrology is affected by experience and many random factors; the mineralogy method is greatly affected by hydrodynamics and diagenesis; the elemental geochemistry method and geophysics method have multiple solutions, etc. The fission track method analyzes the provenance area by using the radiation damage generated in the crystal lattice when the trace uranium contained in apatite and zircon fissions. After a series of chemical treatments, tracks are formed. By observing the distribution of the density, length and other characteristics of the tracks and conducting statistical analysis on them, information related to the age and tectonic evolution of the provenance area can be extracted. The fission track method requires that the samples be subjected to thermal neutron irradiation to promote nuclear reactions. Domestic thermal neutron irradiation conditions are relatively inadequate and time-consuming. Sending samples for irradiation abroad is subject to many restrictions by foreign institutions. In addition, the irradiated samples need to be placed for a long time until the radioactivity of the radiation is weakened and harmless to the human body before the next step can be carried out. The experimental cycle is long and the time cost is high. Summary of the invention

[0003] The object of the present invention is to provide a material provenance analysis method based on measuring the Dpar value in view of the above-mentioned deficiencies in the prior art.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] The present invention provides a provenance analysis method based on measuring the Dpar value, comprising the following steps:

[0006] S1. Collect samples from the sedimentation area and source area;

[0007] S2, measuring the Dpar value of the sample obtained in step S1;

[0008] S3. Implement data analysis

[0009] The Dpar values ​​obtained in step S2 are grouped by multidimensional scaling analysis to obtain grouped data, and the grouped data with the same Dpar value characteristics in the sedimentary area and the source area are matched with the Dpar value as a parameter to construct a sedimentary area-source area coupling model to obtain the provenance analysis results;

[0010] Further, in step S1, the sample includes apatite minerals selected from sediments;

[0011] Furthermore, in step S2, the process of measuring the Dpar value of the apatite sample includes: performing target making, polishing, and etching operations on the apatite sample, and measuring the Dpar length under reflected light, and the arithmetic mean of all the Dpar lengths is the Dpar value.

[0012] Furthermore, the Dpar length is the maximum diameter of the fission track etch pit parallel to the C-axis of the apatite crystal and intersecting the polishing surface.

[0013] Further, in step S1, the process of measuring the Dpar value of the sample includes the following steps:

[0014] Step S11, target preparation: using a solution containing epoxy resin to prepare glue, evenly spreading apatite particles on the bottom of the mold, and solidifying at room temperature;

[0015] Step S12, polishing: polishing using 800#, 1200#, 2400# sandpaper and corundum of different particle sizes in sequence;

[0016] Step S13, nitric acid etching: prepare 5.5±0.1 mol / L nitric acid etching solution, control the temperature of the nitric acid etching solution to 21±1° C., immerse the apatite sample obtained in step S12 in the nitric acid etching solution for 20±1 s, then take it out and wash it; use a ZEISSAxio Imager microscope to observe and count the fission track etching pit patterns of a single apatite particle;

[0017] Step S14, Dpar length measurement: using a ZEISS Axio Imager microscope to observe the etched sample obtained in step S13, counting the fission track etch pit patterns of a single apatite particle, and measuring the maximum diameter of the fission track etch pit, i.e., the Dpar length;

[0018] Step S15, Dpar value calculation: take the arithmetic average of all Dpar length data obtained in step S14 to obtain the Dpar value.

[0019] Furthermore, in step S13, the number of fission track etch pit patterns of the fission track of a single particle is counted to be no less than 60.

[0020] Furthermore, in step S3, the software used for data analysis includes isoplotR software.

[0021] The beneficial effects brought by the technical solution provided by the present invention are:

[0022] (1) The present invention provides a provenance analysis method based on measuring Dpar values. By measuring the Dpar values ​​of sedimentary area and source area samples, using multidimensional scaling (MDS) and building a sedimentary area-source area coupling model, the precise location of the provenance area can be determined and a source-sink system can be established. The concept of the present invention is based on the fact that the Dpar value of the fission track of apatite samples is positively correlated with the Cl element content value and negatively correlated with the F element content value. During the process of source area erosion, transportation, sedimentation, diagenesis and later transformation, the F and Cl element content values ​​of the samples do not change significantly. Sedimentary samples from different provenance areas have different Cl and F element content values, and these differences are expressed by Dpar values. Therefore, the results of provenance analysis by measuring Dpar values ​​are less affected by random factors such as hydrodynamics and diagenesis. Using multidimensional scaling (MDS) and building a sedimentary area-source area coupling model, the sediment source and provenance area can be accurately delineated, and a detailed source-sink system can be established, making the provenance analysis more accurate and reliable;

[0023] (2) The method of the present invention can accurately obtain the result of material provenance analysis by only measuring the Dpar value of the fission track sample. In addition, it is not necessary to irradiate the fission track sample with thermal neutrons during the measurement of the Dpar value. The time consumption for obtaining the Dpar value is short, which effectively solves the defects of the traditional method of measuring the fission track age for material provenance analysis, that is, the analysis sample needs to be sent to a nuclear reactor for thermal neutron irradiation, the irradiation takes a long time, and there is radioactive damage.

[0024] (3) The method of the present invention does not damage the apatite sample, and subsequent fission track experimental analysis, such as age and length measurement, thermal history simulation of the sedimentary area, etc., can be continued, which greatly reduces the research cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of target preparation during the process of measuring the Dpar value of apatite samples;

[0026] Figure 2 Schematic diagram of polishing during the process of measuring the Dpar value of apatite sample;

[0027] Figure 3 Schematic diagram of nitric acid etching during the measurement of the Dpar value of apatite samples;

[0028] Figure 4 The fission track etching pattern during the measurement of the Dpar value of the apatite sample;

[0029] Figure 5 This is the relationship between the Dpar value and the Cl content value of the apatite sample;

[0030] Figure 6 It is the relationship diagram between Dpar value and F content value of apatite sample;

[0031] Figure 7 This is a multidimensional scaling analysis result diagram of Example 1;

[0032] Figure 8 A diagram of the deposition area-source area coupling model constructed in Example 1;

[0033] Fig. 9 This is the fission track age distribution diagram of single apatite grain in comparative example 1. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with specific embodiments and drawings.

[0035] like Figure 1 The figure shows a schematic diagram of target preparation in the process of measuring the Dpar value of apatite samples. The apatite particles in the deposition area and the source area are evenly placed at the bottom of the mold, and the prepared epoxy resin mixture is extracted into the mold through a vacuum static instrument. The epoxy resin mixture can be a resin curing agent with a ratio of epoxy resin: curing agent = 25:3.

[0036] like Figure 2 The figure shows the polishing diagram of the process of measuring the Dpar value of the apatite sample. When grinding with 800# and 1200# sandpaper, the target sample is manually ground. When grinding with 2400# sandpaper and diamond abrasive mixture, the target sample is placed on the polishing machine, and the spring pressure is 1N.

[0037] like Figure 3 The figure shows the nitric acid etching process for measuring the Dpar value of apatite samples. During etching, the constant temperature water tank is used to maintain the etching temperature at 21±1°C, the concentration of the nitric acid etching solution is 5.5±0.1mol / L, each target sample is etched in the etching solution for 20±1s, and the etched target sample is cleaned with ionized water for testing.

[0038] like Figure 4 Shown is the fission track etching pit pattern during the measurement of the Dpar value of the apatite sample.

[0039] like Figure 5 The figure shows the relationship between the Dpar value and the Cl content of the apatite sample. The Dpar value and the Cl content of different apatite samples are positively correlated. The Dpar value and the Cl content of different apatite samples are analyzed by the least squares method, and the relationship function between the two is fitted as follows:

[0040] Formula 1: Cl=0.36-1.178*Dpar+0.35732*Dpar^2, R 2 =0.90.

[0041] like Figure 6 The figure shows the relationship between the Dpar value and the F content of the apatite sample. The Dpar value and the F content of different apatite samples are negatively correlated. The Dpar value and the F content of different apatite samples are analyzed by the least squares method, and the relationship function between the two is fitted as follows:

[0042] Formula 2: F=4.67-1.31*Dpar+0.04176*Dpar^2, R 2 =0.91.

[0043] Example 1

[0044] Analysis of Hanjiang River sand and its surrounding source-sink system

[0045] Step S1, collecting samples from the deposition area and source area

[0046] The river sand samples HJ02, HJ04, HJ05, HJ06, HJ07, HJ08 and HJ09 were collected from the Hanjiang River in Zhongxiang City, Hubei Province. These samples are sandy sediments located on the riverside of the Hanjiang River. The sampling location information is shown in Table 1. During the sample collection process, each sampling point first delineated a sampling range of about half a meter in diameter, removed the surface covering layer, and then collected about 0.4 kg of samples at 5 different locations at the same sampling point to ensure sample uniformity. The total mass of each sample was about 2 kg.

[0047] Table 1 Sampling location information table

[0048] Sample No. longitude latitude Elevation Lithology HJ02 112.6665°E 30.8371°N 41.79m river sand HJ04 112.5741°E 30.8764°N 44.79m river sand HJ05 112.5654°E 30.9373°N 40.79m river sand HJ06 112.5568°E 31.1376°N 38.79m river sand HJ07 112.3987°E 31.6474°N 45.69m river sand HJ08 112.2269°E 31.7481°N 53.69m river sand HJ09 112.4403°E 31.2896°N 43.69m river sand

[0049] About 2 kg of fresh igneous rock samples were collected from the two potential source areas of the Qinling orogenic belt and the Dabie orogenic belt. To prevent high temperature from affecting mineral annealing, sampling in places prone to fire was avoided as much as possible. During the sample collection process, weathering residues, soil and weathering crust on the rock surface should be removed, and the samples should be knocked out in situ.

[0050] Sample pretreatment: The apatite samples collected from the Hanjiang River sand and the Qinling orogenic belt and the Dabie orogenic belt were subjected to coarse crushing, fine crushing, washing, electromagnetic separation, heavy liquid separation and other steps in sequence to separate apatite and heavy minerals such as zircon, tourmaline, rutile, titanite, epidote, garnet, pyroxene, amphibole and other magnetic minerals such as magnetite. Finally, single apatite particles with intact crystal form and no obvious cracks were selected under binoculars.

[0051] Step S2, measuring the Dpar value of apatite samples in the sedimentary area and potential source area

[0052] Target making: Hanjiang River sand and apatite sample particles from Qinling orogenic belt and Dabie orogenic belt are evenly placed at the bottom of the mold, and the prepared epoxy resin mixture of Epoxy:Hardener=25:3 is extracted into the mold through a vacuum station;

[0053] Polishing: Use 800# and 1200# sandpaper to manually grind the prepared target sample, and then use 2400# sandpaper and diamond abrasive mixture to polish on a polishing machine, and adjust the polishing pressure spring to 1N until the maximum inner surface of the apatite particles is revealed;

[0054] Nitric acid etching: The etching temperature was maintained at 21.0°C in a constant temperature water tank, and each target sample was etched for 20 seconds using a 5.5 mol / L nitric acid etching solution;

[0055] Statistical calculation: The samples obtained in step S13 were observed using a ZEISS Axio Imager microscope, the number of fission track etching patterns was counted, and the arithmetic mean maximum diameter of all the fission track etching patterns counted was calculated to obtain the Dpar values ​​of the Hanjiang River sand and the apatite samples in the Qinling orogenic belt and the Dabie orogenic belt.

[0056] Using a ZEISS Axio Imager microscope, the Dpar value of apatite particles with the crystallographic c-axis parallel to the slide plane was measured near the center of the field of view under the optical microscope (the maximum diameter of the fission track etching pit parallel to the C-axis of the apatite crystal and intersecting the polished surface): open the AxioVision software, find the area to be measured under a low-power microscope, and focus preliminarily; after focusing, use the "white balance" and "measure exposure" functions to correct the chromatic aberration and brightness of the preview image in the software; continuously increase the magnification of the microscope objective lens, and adjust and focus on the area to be measured until it is focused on the sample surface at the highest magnification to form a clear preview image under the microscope; open the FissionTrack plug-in in the main interface of the software, click "StartMeasuremen", and click "New" to automatically generate an Excel table for recording data; click the first and last endpoints of the long axis direction of the etching pit once with the left mouse button to calculate the C-axis direction of the measured particle; right-click one endpoint of the long axis of the etching pit, and right-click the other endpoint again, and the software will automatically form a white line segment and calculate the Dpar length. Sixty fission track etching patterns were measured for each apatite under reflected light to obtain the average Dpar value of a single particle.

[0057] Step S3, using multidimensional scaling analysis to group the Dpar values ​​obtained in step S2 to obtain grouped data, using the Dpar value as a parameter, matching the grouped data with the same Dpar value characteristics in the sedimentary area and the source area to construct a sedimentary area-source area coupling model, and obtaining the provenance analysis results.

[0058] The Dpar value data of the samples of Qinling orogenic belt, Dabie orogenic belt and Hanjiang river sand (HJ02, HJ04, HI05, HJ06, HJ07, HJ08 and HJ09) were jointly input into the Isoplot software based on R language programming by Vermeesch et al. Each sample data occupies a separate column, and the sample name is in the first row, forming a "difference" matrix of the Dpar value distribution of each sample. Set the software mode to detritals-MDS mode, check "Sample name in the first row" and "Add neighbor line" in the parameter setting column, and the other parameters are default, and draw a multidimensional scaling analysis diagram of the similarity between samples. The multidimensional scaling analysis diagram uses the coordinates of 9 samples as output. The horizontal coordinate of dimension 1 and the vertical coordinate of dimension 2 have no specific meaning. The geometric distance between the coordinates of the 9 samples reflects the difference of the input Dpar value matrix, in which similar samples are closely clustered together, while samples with large differences are far apart. At the same time, the samples in the multidimensional scaling analysis diagram are connected by solid lines to indicate that they are closest to each other, and the dashed lines represent that the samples are only related. The samples can be clustered by the distance between samples and the connection between dashed and solid lines shown in the multidimensional scaling analysis diagram, and the categories can be divided by elliptical dashed lines.

[0059] The results are as follows Figure 7 As shown in the figure, the solid line connected to the two samples with the closest intimacy, that is, the cluster correlation is high; the dotted line represents the correlation between the samples. The Hanjiang River sand samples (HJ02, HJ05, HJ06, HJ07, HJ08 and HJ09) are closely clustered with the Qinling orogenic belt samples, with close intimacy, and belong to the same category; among them, HJ02 has a weak correlation with the Dabie orogenic belt. Only the Hanjiang River sand sample HJ04 is closely clustered with the Dabie orogenic belt samples, with close intimacy, and belongs to the same category. This result confirms that the Qinling orogenic belt is the main provenance area of ​​the Hanjiang River sand, and the Dabie orogenic belt is the secondary provenance area.

[0060] like Figure 8 As shown in the figure, it is a diagram of the constructed sedimentary area-source area coupling model. The results of the material source analysis are the source-sink coupling models of the Hanjiang-Dabie orogenic belt and the Hanjiang-Qinling orogenic belt. The debris produced by the erosion of the Qinling orogenic belt converges to the main stream of the Hanjiang River through the intermountain tributaries, and is transported to the unloading area with lower terrain by the strong hydrogeological action in the upper reaches of the Hanjiang River, and is deposited in the Hanjiang River. However, there are few rivers in the Dabie Mountains and the altitude is low, so only a small amount of debris formed by erosion is transported to the sedimentary area.

[0061] Comparative Example 1

[0062] The Hanjiang River sand and Qinling orogenic belt and Dabie orogenic belt sample particles are evenly placed at the bottom of the mold, and the prepared epoxy resin mixture is extracted into the mold through a vacuum static instrument. The cooled target sample is manually ground with 800# and 1200# sandpaper, and then polished with 2400# sandpaper and diamond abrasive mixture on a polishing machine, and the spring for adjusting the polishing pressure is 1N. The etching temperature is maintained at 21.0℃ in a constant temperature water tank, and each target sample is etched for 20s using a nitric acid etching solution with a concentration of 5.5mol / L. The etched sample is superimposed on the uranium-free mica sheet and fixed with tape, and placed in an irradiation tube together with a standard sample (Durango, FCT) and a standard glass (IRMM 540) for irradiation. For apatite, the irradiation flux is generally selected to be 3.5×10 15 cm -2 s -1 ,The samples that have been irradiated need to be placed for a long time until the radiation is weakened to be harmless to the human body. Then separate the sample target and the mica sheet, place the mica sheet in a 40% HF solution, and etch it for 40 minutes at room temperature (20-21°C). After the sample target and the mica sheet are matched one by one, the number of spontaneous and induced tracks, the average length of the single particle Dpar value, and the track length are counted under an optical microscope using AxioVision software. The chi-square test is performed on the sample age. The combined age is calculated for those that pass the chi-square test, and the central age is calculated and grouped for those that fail.

[0063] like Fig. 9 As shown in the figure, the single-grain apatite fission track age distribution diagram reveals the provenance information of the Hanjiang River sandstone. Most samples have multi-peak characteristics, indicating that they come from multiple sources. The peaks of most samples are roughly consistent with the peak distribution of the Qinling Orogenic Belt, among which the ages of 80Ma to 110Ma are distributed in all samples, indicating that one of the main sources of the samples is the Qinling Orogenic Belt. In addition, HJ04 shows a single peak characteristic with a peak age of 40 to 60Ma, which is similar to the age distribution of the Dabie Orogenic Belt. The Qinling Orogenic Belt is the main provenance area of ​​the Hanjiang River sandstone, and the Dabie Orogenic Belt is the secondary provenance area.

[0064] Compared with the traditional method of measuring apatite fission track age for provenance analysis (Comparative Example 1), the results of the provenance analysis by measuring the Dpar value of apatite sample particles in Hanjiang River sand, Qinling orogenic belt, and Dabie orogenic belt in Example 1 are consistent with the results of the provenance analysis by measuring the apatite fission track age in Comparative Example 1, both of which show that the Qinling orogenic belt is the main provenance area of ​​Hanjiang River sandstone, and the Dabie orogenic belt is the secondary provenance area. Compared with Comparative Example 1, the method of conducting provenance analysis by measuring the Dpar value of apatite sample particles in Example 1 does not require thermal neutron irradiation of fission track samples, and it takes a short time to obtain the Dpar value, which effectively solves the defects of sending the analyzed samples to a nuclear reactor for thermal neutron irradiation and the long irradiation time and nuclear reactor irradiation radioactive damage in the traditional process of measuring fission track age for provenance analysis. At the same time, this method does not damage the apatite sample, and subsequent fission track experimental analysis can be continued, such as age and length measurement, thermal history simulation research, etc.

[0065] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A provenance analysis method based on measuring Dpar value, characterized in that: The following steps are involved: S1. Collecting samples from the sedimentary area and the source area, wherein the samples include apatite minerals selected from the sediments; S2, measuring the Dpar value of the sample obtained in step S1; S3. Conduct data analysis; The Dpar values ​​obtained in step S2 are grouped by multidimensional scaling analysis to obtain grouped data, and the grouped data with the same Dpar value characteristics in the sedimentary area and the source area are matched with the Dpar value as a parameter to construct a sedimentary area-source area coupling model to obtain the provenance analysis results; The specific process of measuring the Dpar value of an apatite sample includes the following steps: S11, target preparation: using a solution containing epoxy resin to prepare glue, evenly spreading apatite particles on the bottom of the mold, and solidifying at room temperature; S12, polishing: use 800#, 1200#, 2400# sandpaper and diamond sand of different particle sizes for polishing; S13, nitric acid etching: prepare 5.5±0.1 mol / L nitric acid etching solution, control the temperature of the nitric acid etching solution to 21±1°C, immerse the apatite sample obtained in step S12 in the nitric acid etching solution for 20±1s, then take it out and wash it; use a ZEISS AxioImager microscope to observe and count the fission track etching pit patterns of a single apatite particle; S14, Dpar length measurement: using a ZEISS Axio Imager microscope to observe the etching sample obtained in step S13, counting the fission track etching pit patterns of the fission tracks of a single apatite particle, and measuring the maximum diameter of the fission track etching pit, i.e., the Dpar length; the Dpar length is the maximum diameter of the fission track etching pit parallel to the C-axis of the apatite crystal and intersecting the polishing surface; S15. Calculation: Take the arithmetic average of all Dpar length data obtained in step S14 to obtain the Dpar value.

2. A provenance analysis method based on measuring Dpar value according to claim 1, characterized in that: In step S2, the process of measuring the Dpar value of the apatite sample includes: performing target making, polishing, and etching operations on the apatite sample, and measuring the Dpar length under reflected light, and the arithmetic mean of all the Dpar length values ​​is the Dpar value.

3. A provenance analysis method based on measuring Dpar value according to claim 1, characterized in that: In step S13, the number of fission track etch pit patterns of the fission track of a single particle is counted to be no less than 60.

4. A provenance analysis method based on measuring Dpar value according to claim 1, characterized in that: In step S12, the grain sizes of the corundum are 6 μm, 3 μm, 1 μm and 0.04 μm.

5. A provenance analysis method based on measuring Dpar value according to claim 1, characterized in that: In step S3, the software used for data analysis includes isoplotR software.

Images