CN114813728A - Source analysis method based on Dpar value measurement - Google Patents

Abstract

The invention provides a method for analyzing a source based on measurement of a Dpar value. By measuring fission track Dpar values for the deposition and source zone samples; and then grouping the obtained Dpar values by adopting a multidimensional scale analysis method to obtain grouped data, and matching the grouped data with the same Dpar value characteristics of the deposition area and the source area by taking the Dpar values as parameters to construct a deposition area-source area coupling model, so that the source area and the rock type of the source area can be accurately defined, the source of the sediment can be determined, and the source analysis is more accurate and reliable. The method for analyzing the source can accurately obtain the source analysis result only by measuring the Dpar value of the sample, does not need to perform thermal neutron irradiation on the sample in the process of measuring the Dpar value, is short in time consumption for obtaining the Dpar value, and effectively overcomes the defects that the analysis sample needs to be sent to an atomic nuclear reactor for thermal neutron irradiation or long in irradiation time consumption and radioactivity in the traditional process of measuring the fission track age for analyzing the source.

Description

Object source analysis method based on Dpar value measurement

Technical Field

The invention relates to the technical field of source analysis, in particular to a source analysis method based on Dpar value measurement.

Background

There are currently source analysis techniques such as sedimentology, petrology and mineralogy, elemental geochemistry, chronology, clay mineralogy, fission track, fossil and biochemical methods, and geophysical methods. The methods have some limitations and influence the accuracy of source analysis, for example, the sedimentology method has large statistical workload and fuzzy source judgment results, and specific information such as specific positions of source regions and parent rock properties cannot be determined; the judgment of the petrology method on the source is influenced by experience and more random factors; mineralogy is greatly influenced by hydrodynamic force and diagenesis; the elementary geochemical method and the geophysical method have multi-solution property and the like. The fission track method for analyzing the source region of the object utilizes the radiation damage generated in crystal lattice when trace uranium contained in apatite and zircon is fissured, and after a series of chemical treatments, the track is formed, and by observing the distribution of the density, the length and the like of the track and carrying out statistical analysis on the distribution, the information related to the age and the structural evolution of the source region is extracted from the track. The fission track method needs to send a sample to atomic nucleus reaction for thermal neutron irradiation, the domestic thermal neutron irradiation condition is relatively deficient and the time consumption is very long, the sending to foreign irradiation is limited by foreign institutions, the irradiated sample needs to be placed for a long time until the radioactivity of the irradiation is weakened, the next operation can be carried out after the sample is harmless to human bodies, the experiment period is long, and the time cost is high.

Disclosure of Invention

The present invention aims to provide a method for analyzing a source based on measurement of Dpar value, which overcomes the above-mentioned disadvantages of the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for analyzing a source based on measurement of a Dpar value, which comprises the following steps:

s1, collecting samples of the deposition area and the source area;

s2, measuring the Dpar value of the sample obtained in the step S1;

s3, data analysis

Grouping the Dpar values obtained in the step S2 by adopting a multidimensional scale analysis method to obtain grouped data, and matching the grouped data with the same Dpar value characteristics of the deposition area and the source area by taking the Dpar values as parameters to construct a deposition area-source area coupling model to obtain a source analysis result;

further, in step S1, the sample includes apatite minerals selected from the sediment;

further, in step S2, the process of measuring the Dpar value of the apatite sample includes: the Dpar length measurements in reflected light were performed by targeting, polishing, and etching the apatite samples, the arithmetic mean of all the Dpar lengths being the Dpar value.

Further, the Dpar length is a maximum diameter of the fission track etching pit intersecting the polished surface in parallel with the apatite crystal C-axis.

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

step S11, target production: mixing with solution containing epoxy resin, uniformly spreading apatite particles at the bottom of the mold, and solidifying at room temperature;

step S12, polishing: sequentially using 800#, 1200#, 2400# sandpaper and carborundum with different grain diameters for polishing;

step S13, nitric acid etching: preparing 5.5 +/-0.1 mol/L nitric acid etching solution, controlling the temperature of the nitric acid etching solution to be 21 +/-1 ℃, immersing the apatite sample obtained in the step S12 in the nitric acid etching solution for 20 +/-1S, and then taking out and cleaning the apatite sample; observing and counting a fission track etching pit pattern of a single apatite particle by using a ZEISS Axio Imager microscope;

step S14, Dpar length measurement: observing the etching sample obtained in the step S13 by using a ZEISS Axio Imager microscope, counting the fission track etching pit pattern of a single apatite particle, and measuring the maximum diameter of the fission track etching pit, namely the Dpar length;

step S15, Dpar value calculation: arithmetic averaging is performed on all the Dpar length data obtained in step S14 to obtain the Dpar value.

Further, in step S13, the number of fission track etching pit patterns of the fission track of a single grain is counted to be not less than 60.

Further, in step S3, the software used for performing data analysis includes isoplotR software.

The technical scheme provided by the invention has the beneficial effects that:

(1) according to the invention, the exact position of the source region can be determined and a source-sink system can be established by measuring the Dpar values of the deposition region and source region samples and applying a multidimensional scaling analysis (MDS) and constructing a deposition region-source region coupling model. The concept of the invention is based on that the apatite sample fission track Dpar value has a positive correlation with the Cl element content value and has a negative correlation with the F element content value. During the process that the sample undergoes source region denudation, carrying, deposition, diagenesis and later-stage transformation, the content values of F and Cl elements do not change significantly, and the content values of Cl and F elements of the deposition sample from different source regions have differences, and the differences are expressed by a Dpar value. Therefore, the result of the object source analysis by measuring the Dpar value is less influenced by random factors such as hydrodynamic force, diagenesis and the like, a sediment source and an object source region can be accurately defined by applying a multidimensional scaling analysis (MDS) and constructing a deposition region-source region coupling model, and a detailed source convergence system is established, so that the object source analysis is more accurate and reliable;

(2) the method can accurately obtain the source analysis result only by measuring the Dpar value of the fission track sample, does not need to perform thermal neutron irradiation on the fission track sample in the process of measuring the Dpar value, has short consumed time for obtaining the Dpar value, and effectively solves the defects that the analysis sample needs to be sent to an atomic nuclear reactor for thermal neutron irradiation and long consumed time for irradiation and radioactive damage in the traditional process of measuring the fission track age and performing the source analysis;

(3) the method of the invention does not damage the apatite sample, and can continue the subsequent fission track experimental analysis, such as age and length measurement, sedimentation area thermal history simulation and the like, thereby greatly reducing the research cost.

Drawings

FIG. 1 is a schematic diagram showing the targeting in the process of measuring the Dpar value of an apatite sample;

FIG. 2 is a schematic diagram of polishing in the process of measuring the Dpar value of an apatite sample;

FIG. 3 is a schematic diagram of nitric acid etching during measurement of the Dpar value of an apatite sample;

FIG. 4 is a graph of fission track etching during measurement of the Dpar value for an apatite sample;

FIG. 5 is a graph of the Dpar value versus Cl content value for apatite samples;

FIG. 6 is a graph of the Dpar value versus the F content value for apatite samples;

FIG. 7 is a graph showing the results of the multidimensional scaling analysis of example 1;

FIG. 8 is a diagram of a deposition area-source area coupling model constructed in example 1;

FIG. 9 is an age distribution plot of a single particle apatite fission track of comparative example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below with reference to specific examples and accompanying drawings.

As shown in FIG. 1, a schematic diagram of targeting in the process of measuring the Dpar value of an apatite sample is shown. Uniformly placing the apatite particles in the deposition area and the source area at the bottom of the mold, and pumping the prepared epoxy resin mixed solution into the mold through a vacuum standing instrument, wherein the epoxy resin mixed solution can be epoxy resin and curing agent which is 25: 3.

FIG. 2 is a schematic diagram showing polishing in the course of measuring the Dpar value of an apatite sample. The sample was manually ground using 800# and 1200# sandpaper, and the target sample was set on a polishing machine with a spring pressure of 1N when ground using 2400# sandpaper and emery mixed solution.

FIG. 3 is a schematic diagram showing nitric acid etching in the measurement of the Dpar value of an apatite sample. And during etching, the constant-temperature water tank is used for keeping the etching temperature at 21 +/-1 ℃, the concentration of the nitric acid etching solution at 5.5 +/-0.1 mol/L, each target sample is etched in the etching solution for 20 +/-1 s, and the etched target samples are cleaned by ionized water and are to be tested.

As shown in fig. 4, a pit pattern was etched for the fission tracks in measuring the Dpar value of the apatite sample.

As shown in FIG. 5, the relation between the Dpar value and the Cl content value of the apatite sample is shown. The Dpar values and the Cl content values of different apatite samples are in positive correlation, the Dpar values and the Cl content values of the different apatite samples are analyzed by a least square method, and a relation function of the Dpar values and the Cl content values is fitted to be

Equation 1: cl 0.36-1.178 Dpar +0.35732 Dpar 2, R ² ＝0.90。

As shown in FIG. 6, the relation between the Dpar value and the F content value of the apatite sample is shown. The Dpar values and the F content values of different apatite samples are in a negative correlation relationship, the Dpar values and the F content values of the different apatite samples are analyzed by a least square method, and a relation function of the Dpar values and the F content values is fitted to be

Equation 2: f ═ 4.67-1.31 ^ Dpar +0.04176 ^ Dpar 2, R ² ＝0.91。

Example 1

Hanjiang river sand and peripheral source-sink system analysis

Step S1, collecting samples of the deposition area and the source area

River sand samples HJ02, HJ04, HI05, HJ06, HJ07, HJ08 and HJ09 of hanjiang river are collected while hanjiang river dry flow in Zhongxiang city, Hubei province, and the samples are sandy sediments located on the side of hanjiang river dry flow, and the sampling position information is shown in table 1. In the sample collection process, a sampling range with the diameter of about half meter is defined at each sampling point, a covering layer on a surface layer is removed, about 0.4kg of samples are respectively taken at 5 different positions of the same sampling point to ensure the uniformity of the samples, and the total mass of each sample is about 2 kg.

TABLE 1 sampling location information Table

Sample number	Longitude (G)	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

About 2kg of fresh magma samples were collected in each of two potential source areas, the Qinling mountain making zone and the Dabie mountain making zone. In order to prevent mineral annealing from being influenced by high temperature and avoid sampling in places easy to catch fire as much as possible, weathering residues, soil and weathering crust on the surface of rock are removed in the sample collection process, and the samples are guaranteed to be knocked out in situ.

Sample pretreatment: sequentially carrying out coarse crushing, fine crushing, elutriation, electromagnetic separation, heavy liquid separation and the like on collected apatite samples of Hanjiang river sand, Qinling mountain-making zone and Dabie mountain-making zone, separating to obtain apatite, zircon, tourmaline, rutile, sphene, green cord stone, garnet, pyroxene, glauberite and other heavy minerals and magnetite and other magnetic minerals, and finally selecting apatite single particles with complete crystal forms and no obvious cracks under binoculars.

Step S2, measuring the Dpar value of apatite samples of the deposition area and the potential source area

Target making: uniformly placing apatite sample particles of Hanjiang river sand, Qinling mountaineering belts and Dabie mountaineering belts at the bottom of a mold, and extracting a prepared Epoxy resin mixed solution of Epoxy, Hardener and 25:3 into the mold through a vacuum standing instrument;

polishing: manually grinding the prepared target sample by using 800# and 1200# abrasive paper, then polishing the target sample by using 2400# abrasive paper and carborundum mixed solution on a polishing machine, and adjusting a spring of a polishing pressure to be 1N until the largest inner surface of apatite particles is revealed;

etching by nitric acid: etching each target sample for 20s by using nitric acid etching solution with the concentration of 5.5mol/L while keeping the etching temperature at 21.0 ℃ in a constant-temperature water tank;

and (3) statistical calculation: and observing the sample obtained in the step S13 by using a ZEISS Axio Imager microscope, counting the number of fission track etching patterns, and calculating the arithmetic mean maximum diameter of all the counted fission track etching patterns to obtain the Dpar value of the apatite samples of Hanjiang river sand, Qinling mountain making zone and Dabie mountain making zone.

Apatite particles with crystallographic C-axis parallel to the slide plane were measured for Dpar values (maximum diameter of the fission track etch pits parallel to the apatite crystal C-axis intersecting the polishing surface) using a ZEISS Axio Imager microscope near the center of the field of view under an optical microscope: opening AxioVision software, finding a region to be detected under a low-power lens, and carrying out primary focusing; after focusing is finished, correcting the color difference and brightness of a preview image in software by using the functions of white balance and measurement exposure; continuously increasing the multiple of the microscope objective lens, and adjusting and focusing the microscope objective lens to the area to be measured until the microscope objective lens is focused on the surface of the sample under the highest multiple to form a clear preview image under the microscope; opening a FissionTrack plug-in on a software main interface, clicking 'Start Measuremen' and clicking 'New' to automatically generate an Excel table for recording data; clicking the head and tail end points in the long axis direction of the etching pit once by the left mouse button, and calculating the C axis direction of the measured particles; and clicking one end point of the long axis of the etching pit by a right button of the mouse, and clicking the other end point position by the right button again, so that the software can automatically form a white line segment and calculate the Dpar length. The average Dpar value for a single particle was obtained by measuring 60 fission track etch patterns per apatite under reflected light.

And S3, grouping the Dpar values obtained in the step S2 by adopting a multidimensional scale analysis method to obtain grouped data, and matching the grouped data with the same Dpar value characteristics of the deposition area and the source area by taking the Dpar values as parameters to construct a deposition area-source area coupling model so as to obtain a source analysis result.

The method comprises the steps of inputting sample Dpar value data of Qinling mountain belts, Dabie mountain belts and Hanjiang river sands (HJ02, HJ04, HI05, HJ06, HJ07, HJ08 and HJ09) into Isoplot software programmed by Vermeesch and the like based on R language together, wherein each sample occupies a single column, and the sample name is positioned at the first row to form a 'difference' matrix of the distribution of the sample Dpar value. Setting a software mode as a detritals-MDS mode, checking the sample name in the first row and adding a near line in the parameter setting column, and drawing a multi-dimensional scale analysis graph of the similarity between samples, wherein the rest parameters are defaults. The multidimensional scale analysis graph takes coordinates of 9 samples as output, the abscissa taken as dimension 1 and the ordinate taken as 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, similar samples are closely gathered together, the samples with larger difference are far away, meanwhile, the samples in the multidimensional scale analysis graph are connected by a solid line to show that the intimacy is closest to each other, and the dashed line is connected to show that the samples only have correlation. The samples can be clustered through the distance between the samples and the connection condition of the virtual line and the real line displayed in the multi-dimensional scale analysis chart, and the samples are classified by the oval dotted line.

The result is shown in fig. 7, in which the solid line is connected to represent that two samples with the closest affinity, i.e. the cluster correlation is high; the dotted lines represent the correlation between samples. The Hanjiang river sand samples (HJ02, HJ05, HJ06, HJ07, HJ08 and HJ09) are in the same category as the Qinling mountainous zone samples with close aggregation and intimacy; wherein HJ02 has weak correlation with Dabie mountain belt. Only the Hanjiang river sand sample HJ04 is tightly gathered with the Dabie mountain-making belt sample, and the affinity is close, and the samples are in the same category. The result proves that the Qinling mountain making zone is a main material source zone of the Hanjiang river sand, and the Dabie mountain making zone is a secondary material source zone.

FIG. 8 shows a deposition area-source area coupling model. The source analysis result is a source-sink coupling model of Hanjiang-Dabie mountain making zone and Hanjiang-Qinling mountain making zone. Debris substances generated by denudation of mountainous mountaineering zones in Qinling mountains are gathered to Hanjiang dry flow through inter-mountain branches, are carried to unloading areas with lower topography by strong hydrogeological action at the upper reaches of Hanjiang and are deposited in Hanjiang. And the large mountain area has less rivers and low altitude, and only a small amount of debris substances formed by denudation are conveyed to the deposition area.

Comparative example 1

And uniformly placing sample particles of the Hanjiang river sand, the Qinling mountaineering zone and the Dabie mountaineering zone at the bottom of the mold, and extracting the prepared epoxy resin mixed solution into the mold through a vacuum standing instrument. The cooled target sample was manually ground with 800# and 1200# sandpaper, and then polished with 2400# sandpaper and emery mixed solution on a polishing machine, with a polishing pressure of 1N adjusted by a spring. Each target sample was etched for 20 seconds in a nitric acid etching solution having a concentration of 5.5mol/L while keeping the etching temperature at 21.0 ℃ in a constant temperature water tank. The etched sample was laminated with a 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. The irradiation flux is generally chosen to be 3.5X 10 for apatite ¹⁵ cm ^-2 s ^-1 After the sample subjected to irradiation needs to be placed for a long time and the radiation is weakened to be harmless to a human body, separating the sample target and the mica sheet, placing the mica sheet into a 40% HF solution, and etching for 40min at room temperature (20-21 ℃). And (3) making the sample targets and the mica sheets in a one-to-one correspondence mode, and performing spontaneous and induced track quantity, single-particle Dpar value average length and track length statistics by using AxioVision software under an optical microscope. The age of the samples was checked on the chi-square scale, the age was pooled by calculation of the chi-square scale, the age at the center was not calculated and grouped.

As shown in fig. 9, the information of the sand source of hanjiang river is revealed by the age distribution map of the single-particle apatite fission track, and most samples have the characteristic of multiple peaks, which indicates that the samples come from multiple sources. Most of the peaks of the samples are approximately matched with the peak distribution of the Qinling mountain making zone, wherein the ages of 80Ma to 110Ma are distributed in each sample, and one of the main sources of the samples is the Qinling mountain making zone. In addition, HJ04 shows a unimodal characteristic with a peak age of 40-60 Ma, and is similar to the age distribution of a Dabie mountain making belt. The Qinling mountain making zone is a main material source zone of the sandstone of the Hanjiang river, and the Dabie mountain making zone is a secondary material source zone.

Compared with the conventional method (comparative example 1) for performing the source analysis by measuring the age of the apatite fission track, the result of performing the source analysis by measuring the Dpar value of the apatite sample particles in the Hanjiang river sand, the Qinling mountain making zone and the Dabie mountain making zone in example 1 is consistent with the result of performing the source analysis by measuring the age of the apatite fission track in comparative example 1, and both the Qinling mountain making zone is the main source area of the sandstone of the Hanjiang river and the Dabie mountain making zone is the secondary source area. Compared with the comparative example 1, the method for performing the source analysis by measuring the particle Dpar value of the apatite sample in the example 1 does not need to perform thermal neutron irradiation on the fission track sample, the time consumption for obtaining the Dpar value is short, the defects that the analysis sample needs to be sent to an atomic nuclear reactor for thermal neutron irradiation and irradiation time consumption is long and irradiation radioactive damage occurs to the atomic nuclear reactor in the traditional process of determining the age of the fission track and performing the source analysis are effectively overcome, meanwhile, the method does not damage the apatite sample, and the follow-up experimental analysis of the fission track, such as age and length measurement, thermal history simulation research and the like, can be continued.

The features of the embodiments and embodiments described herein above may be combined with each other without conflict.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (8)

1. A method for analyzing a source based on measurement of a Dpar value is characterized by comprising the following steps: the method comprises the following steps:

s1, collecting samples of the deposition area and the source area;

s2, measuring the Dpar value of the sample obtained in the step S1;

s3, data analysis

And grouping the Dpar values obtained in the step S2 by adopting a multi-dimensional scale analysis method to obtain grouped data, and matching the grouped data with the same characteristics of the Dpar values in the deposition area and the source area by taking the Dpar values as parameters to construct a deposition area-source area coupling model so as to obtain an object source analysis result.

2. The method of claim 1, wherein the method comprises the following steps: in step S1, the sample includes apatite minerals selected from the sediment.

3. A method of source analysis based on the measurement of Dpar values according to claim 2, characterized in that: in step S2, the process of measuring the Dpar value of the apatite sample comprises: the Dpar length measurements in reflected light were performed by targeting, polishing, and etching the apatite samples, and the arithmetic mean of all the Dpar length values was the Dpar value.

4. A method of source analysis based on the measurement of Dpar values according to claim 3, characterized in that: the Dpar length is a maximum diameter of the fission track etch pit parallel to the apatite crystal C-axis that intersects the polished face.

5. The method of claim 4, wherein the method comprises the following steps: the specific procedure for measuring the Dpar value of apatite samples comprises the following steps:

s11, target preparation: mixing with solution containing epoxy resin, uniformly spreading apatite particles at the bottom of the mold, and solidifying at room temperature;

s12, polishing: sequentially using 800#, 1200#, 2400# sandpaper and carborundum with different grain diameters for polishing;

s13, nitric acid etching: preparing 5.5 +/-0.1 mol/L nitric acid etching solution, controlling the temperature of the nitric acid etching solution to be 21 +/-1 ℃, immersing the apatite sample obtained in the step S12 in the nitric acid etching solution for 20 +/-1S, and then taking out and cleaning the apatite sample; observing and counting a fission track etching pit pattern of a single apatite particle by using a ZEISS Axio Imager microscope;

s14, Dpar length measurement: observing the etching sample obtained in the step S13 by using a ZEISS Axio Imager microscope, counting a fission track etching pit pattern of a fission track of a single apatite particle, and measuring the maximum diameter of the fission track etching pit, namely the Dpar length;

s15, calculating: arithmetic averaging is performed on all the Dpar length data obtained in step S14 to obtain the Dpar value.

6. The method of claim 5, wherein the method comprises the following steps: in step S13, the number of fission track etching pit patterns of the fission track of a single grain is counted to be not less than 60.

7. The method of claim 5, wherein the method comprises the following steps: in step S12, the corundum has a particle size of 6 μm, 3 μm, 1 μm or 0.04 μm.

8. The method of claim 1, wherein the method comprises the following steps: in step S3, the software used to perform the data analysis includes isoplotR software.

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