Safe and efficient method for heavy mineral separation and identification

Abstract

The present invention belongs to the field of geological technology, especially a safe and efficient heavy mineral sorting and identification method, comprising the following steps: S1: the samples collected in the field are first roughly washed with clean water to wash away most of the mud attached to the sample surface, and the washed samples are dried at a temperature not exceeding 60°C; S2: 2g of Biao Le epoxy resin is weighed and poured into a mold, and 0.5-0.7g of the dried sample is poured into the Biao Le epoxy resin, and stirred while pouring. The present invention uses water and alcohol to replace the toxic tribromoform heavy liquid, avoids the use of carcinogens, increases the safety in the heavy mineral analysis process, is convenient for large-scale experimental promotion, and TIMA is an instrument that automatically scans and identifies minerals, mainly based on the brightness of the energy spectrum line and the backscattering diagram, and can accurately determine the type of mineral by comparing with the standard sample data under the same test conditions, completely excludes human factors interference during data acquisition, and the data quality is guaranteed, and a large amount of heavy mineral geological information can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of geology, and in particular to a safe and efficient heavy mineral separation and identification method. Background Art

[0002] In geology, heavy minerals refer to detrital minerals with a relative density greater than 2.86 g / m3. They are highly stable and can maintain their original physical and chemical properties during rock erosion, transportation and deposition. Therefore, their types and combinations can better reflect the properties of the source rock. However, since the content of heavy minerals in rocks is generally less than 1%, "pre-enrichment" is usually required before heavy mineral identification. The result indicators of heavy mineral identification include: type of heavy minerals, number of particles, particle size, etc.

[0003] Conventional heavy mineral separation and identification methods are as follows:

[0004] (1) The samples collected in the field were first washed with clean water to remove most of the mud attached to the surface of the samples. The washed samples were then dried and weighed at a temperature not exceeding 60°C.

[0005] (2) Wash the separatory bottle, pour the dried sample into the funnel and pour in about half the volume of the funnel with heavy liquid, gently shake the separatory bottle, and stir with a clean glass rod to settle. After standing for 15 minutes, when the minerals in the funnel are relatively still and no longer float and flow in a large range, loosen the clamp to let the heavy liquid flow down, and use filter paper to catch the heavy liquid and heavy minerals that come down first. At this time, special attention should be paid to prevent the light mineral particles from flowing out with the heavy liquid, and then the remaining heavy liquid and minerals should be caught with another piece of filter paper.

[0006] (3) Finally, rinse the heavy minerals with alcohol, dry them, write the sample number on them and pack them. Wash the heavy mineral particles on the filter paper with alcohol and place them in an evaporating dish, dry them, weigh them and record them. Wash the separatory bottle with alcohol and turn off the fume hood.

[0007] (4) Identify heavy minerals using binoculars and polarizing microscopes based on the color, luster, shape, size, roundness, twinning, dissociation, fracture, degree of weathering, degree of oxidation and special surface features of the mineral particles.

[0008] The problems and shortcomings of the heavy mineral separation and identification methods of the prior art are as follows:

[0009] (1) Before the experiment, it is necessary to prepare bromoform heavy liquid with a density of 2.86 g / m3 in advance. Bromoform is a carcinogenic organic compound. Long-term exposure to it poses health risks. Therefore, the entire process of heavy mineral sorting needs to be completed in a well-ventilated laboratory, and the bromoform heavy liquid sorting must be completed in a fume hood, which is difficult to promote widely. In addition, the density of the heavy liquid (2.86 g / m3) is similar to the average density of heavy minerals (2.86 g / m3). There may be a risk of mineral loss during the sorting process.

[0010] (2) The manual identification of heavy minerals is tedious and subjective. The total number of heavy mineral identification particles is insufficient, usually less than 500, and the statistical significance is limited. In addition, the quality of heavy mineral identification depends entirely on the experience of the test personnel. Identification under binoculars and polarizing microscopes only relies on the appearance characteristics of the minerals, which can easily confuse minerals with similar characteristics.

[0011] (3) There is insufficient geological information on heavy minerals. Manual identification can only obtain a small amount of information on mineral species, and it is difficult to obtain specific species information on complex minerals such as garnet, amphibole, and pyroxene. Mineral categories can be distinguished based on mineral morphological characteristics, but different species of the same category of minerals only differ in elemental composition and are difficult to distinguish manually. Conventional manual identification can only distinguish between major mineral categories, and information on minor mineral categories containing rich geological information cannot be obtained. Summary of the invention

[0012] Based on the technical problems raised in the background technology, the present invention proposes a safe and efficient heavy mineral separation and identification method.

[0013] The safe and efficient heavy mineral separation and identification method proposed by the present invention comprises the following steps:

[0014] S1: The samples collected in the field were first washed with clean water to remove most of the mud attached to the surface of the samples, and then dried at a temperature not exceeding 60°C;

[0015] S2: Weigh 2g of Buehler epoxy resin and pour it into the mold, take 0.5-0.7g of the dried sample and pour it into the Buehler epoxy resin, stirring while pouring;

[0016] S3: Evacuate the mold for about 1 hour to ensure there are no bubbles, put it in the oven, and wait for the resin to solidify;

[0017] S4: Polishing and grinding. After the resin solidifies, the resin target is polished and ground with sandpaper, suspension and polishing machine until the inside of the sample particles is exposed;

[0018] S5: Tested using the TIMA instrument, first taking a low-precision backscatter photo of the entire resin target, selecting the area to be scanned, and dividing the scan area into several small squares of 1000×1000μm;

[0019] S6: First, take a high-precision backscatter image inside a single small square, then obtain energy spectrum data point by point, evenly mark points inside the mineral particles, and increase the number of points at the mineral boundaries to obtain the best results;

[0020] S7: After the test is completed, the software automatically splices the backscattering data and energy spectrum data obtained from the test. The automatic mineral analysis software will compare the energy spectrum lines of the unknown mineral and the standard mineral to determine the specific type of the mineral;

[0021] S8: Offline data acquisition: the mass percentage, volume percentage, and particle number of one or more minerals in the sample can be exported offline in the test data. Through the filter, minerals of a certain particle size can be selected for statistics;

[0022] S9: Remove the light mineral components in the obtained data, recalculate the percentage content of the heavy mineral components of each sample, and obtain the percentage content of the heavy mineral components of each sample.

[0023] As a preferred embodiment of the present invention, in S5, S6 and S7, the resin target to be analyzed is carbon-sprayed before the experiment.

[0024] As a preferred embodiment of the present invention, in S5, S6 and S7, the automatic mineral analysis software (TIMA) instrument is mainly composed of a field emission scanning electron microscope, four energy spectrum probes and automatic analysis software.

[0025] As a preferred embodiment of the present invention, in S5, S6 and S7, the acceleration voltage is 25 kV, the current is 9 nA, the working distance is 15 mm, the current and BSE signal intensity are calibrated using the platinum Faraday cup automatic program, and the EDS signal is calibrated using the Mn standard sample.

[0026] As a preferred embodiment of the present invention, in S5, S6 and S7, the dissociation mode is used in the test, and the X-ray count at each point is 1000.

[0027] As a preferred implementation manner of the present invention, in S5, S6 and S7, the pixel size is 3 μm and the energy spectrum step length is 9 μm.

[0028] As a preferred embodiment of the present invention, in S5, S6 and S7, the data acquisition process is a fully automatic operation and does not require human intervention.

[0029] The beneficial effects of the present invention are:

[0030] 1. In the present invention, water and alcohol are used to replace the toxic bromoform heavy liquid, which avoids the use of carcinogens, increases the safety of the heavy mineral analysis process, facilitates the large-scale promotion of the experiment, and uses water (1 g / m3) and alcohol (0.8 g / m3) for washing, which can reduce mineral loss.

[0031] 2. In the present invention, the total number of heavy mineral identification particles is guaranteed. Under normal circumstances, for a 3 cm diameter resin target, the total number of mineral identification particles is not less than 100,000, and 10,000 valid data can be obtained (about 200 times the number of particles identified manually), and a large amount of data can be obtained in a short time.

[0032] 3. In the present invention, the interference of human factors on the identification of heavy minerals is eliminated, the data quality is guaranteed, and a large amount of heavy mineral geological information can be obtained. TIMA is an instrument that automatically scans and identifies minerals, mainly based on the brightness of the energy spectrum line and the backscatter diagram. By comparing with the standard sample data under the same test conditions, the type of mineral can be accurately determined. The interference of human factors is completely eliminated in the data acquisition process. TIMA can provide the energy spectrum information of all heavy mineral particles, can determine the specific species information of the mineral particles, and can more accurately reflect the characteristics of the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram comparing the conventional process and the optimized process of the safe and efficient heavy mineral separation and identification method proposed in the present invention. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0035] Reference Figure 1 , a safe and efficient method for the separation and identification of heavy minerals, comprising the following steps:

[0036] S1: The samples collected in the field are first washed with clean water to remove most of the mud attached to the surface of the samples. The washed samples are then dried at a temperature not exceeding 60°C; this avoids the use of carcinogens, increases the safety of heavy mineral analysis, and facilitates large-scale promotion of experiments. In addition, the use of water (1 g / m3) and alcohol (0.8 g / m3) for washing can reduce mineral loss.

[0037] S2: Weigh 2g of Buehler epoxy resin and pour it into the mold, take 0.5-0.7g of the dried sample and pour it into the Buehler epoxy resin, stirring while pouring;

[0038] S3: Evacuate the mold for about 1 hour to ensure there are no bubbles, put it in the oven, and wait for the resin to solidify;

[0039] S4: Polishing and grinding. After the resin solidifies, the resin target is polished and ground with sandpaper, suspension and polishing machine until the inside of the sample particles is exposed;

[0040] S5: Use the automatic mineral analysis software (TIMA) instrument to test. First, take a low-precision backscatter photo of the entire resin target, select the area to be scanned, and divide the scanning area into several small squares of 1000×1000μm. TIMA automatically scans and identifies minerals for the instrument, mainly based on the brightness of the energy spectrum line and the backscattering diagram. By comparing with the standard sample data under the same test conditions, the type of mineral can be accurately determined. The interference of human factors is completely eliminated during the data acquisition process. TIMA can provide the energy spectrum information of all heavy mineral particles, can determine the specific species information of mineral particles, and can more accurately reflect the characteristics of the sample;

[0041] S6: First, take a high-precision backscatter image inside a single small square, then obtain energy spectrum data point by point, evenly dot the inside of the mineral particles, and encrypt the dots at the mineral boundaries to obtain the best results; under normal circumstances, a 3 cm diameter resin target, the total number of mineral identification is not less than 100,000 particles, and 10,000 valid data can be obtained (about 200 times the number of particles identified manually), which can obtain a large amount of data in a short time;

[0042] S7: After the test is completed, the software automatically splices the backscattering data and energy spectrum data obtained from the test. The automatic mineral analysis software will compare the energy spectrum lines of the unknown mineral and the standard mineral to determine the specific type of the mineral;

[0043] S8: Offline data acquisition: the mass percentage, volume percentage, and particle number of one or more minerals in the sample can be exported offline in the test data. Through the filter, minerals of a certain particle size can be selected for statistics;

[0044] S9: Remove the light mineral components in the obtained data, recalculate the percentage content of the heavy mineral components of each sample, and obtain the percentage content of the heavy mineral components of each sample.

[0045] In a specific implementation manner, the data acquisition process of the automatic mineral analysis software (TIMA) test is a fully automatic operation, which does not require human intervention, and the resin target to be analyzed is carbon-sprayed before the experiment; the automatic mineral analysis software (TIMA) instrument is mainly composed of a field emission scanning electron microscope, four energy spectrum probes and automatic analysis software; in the experiment, the acceleration voltage is 25kV, the current is 9nA, the working distance is 15mm, the current and BSE signal intensity are calibrated using the platinum Faraday cup automatic program, and the EDS signal is calibrated using the Mn standard sample; the dissociation mode is used in the test, and the X-ray count at each point is 1000; the pixel size is 3μm, and the energy spectrum step is 9μm.

[0046] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A safe and efficient method for sorting and identifying heavy minerals, characterized in that: The following steps are involved: S1: The samples collected in the field were first washed with water and alcohol to remove most of the mud attached to the surface of the samples. The washed samples were then dried at a temperature not exceeding 60°C. S2: Weigh 2g of Buehler epoxy resin and pour it into the mold, take 0.5-0.7g of the dried sample and pour it into the Buehler epoxy resin, stirring while pouring; S3: Evacuate the mold for 1 hour to ensure there are no bubbles, put it in the oven, and wait for the resin to solidify; S4: Polishing and grinding. After the resin solidifies, the resin target is polished and ground with sandpaper, suspension and polishing machine until the inside of the sample particles is exposed; S5: Use the automatic mineral analysis software instrument to test. First, take a low-precision backscatter photo of the entire resin target, select the area to be scanned, and divide the scanning area into several small squares of 1000×1000μm; S6: First, take a high-precision backscatter image inside a single small square, then obtain energy spectrum data point by point, evenly mark points inside the mineral particles, and increase the number of points at the mineral boundaries to obtain the best results; S7: After the test is completed, the software automatically splices the backscattering data and energy spectrum data obtained from the test. The automatic mineral analysis software will compare the energy spectrum lines of the unknown mineral and the standard mineral to determine the specific type of the mineral; S8: Offline data acquisition, offline export of mass percentage, volume percentage, and particle number of one or more minerals in the sample in the test data, and through the filter, select minerals of a certain particle size for statistics; S9: Remove the light mineral components in the obtained data, recalculate the percentage content of the heavy mineral components of each sample, and obtain the percentage content of the heavy mineral components of each sample.

2. The safe and efficient heavy mineral separation and identification method according to claim 1, characterized in that: In S5, S6 and S7, the resin target to be analyzed is carbon-sprayed before the experiment.

3. The safe and efficient heavy mineral separation and identification method according to claim 1, characterized in that: In S5, S6 and S7, the automatic mineral analysis software instrument is mainly composed of a field emission scanning electron microscope, four energy spectrum probes and automatic analysis software.

4. The safe and efficient heavy mineral separation and identification method according to claim 1, characterized in that: In the experiments of S5, S6 and S7, the accelerating voltage was 25 kV, the current was 9 nA, the working distance was 15 mm, the current and BSE signal intensity were calibrated using the automatic procedure of the platinum Faraday cup, and the EDS signal was calibrated using the Mn standard sample.

5. The safe and efficient heavy mineral separation and identification method according to claim 1, characterized in that: In S5, S6 and S7, the dissociation mode was used in the test, and the X-ray counts for each point were 1000.

6. The safe and efficient heavy mineral separation and identification method according to claim 1, characterized in that: In S5, S6 and S7, the pixel size is 3 μm and the energy spectrum step size is 9 μm.

7. The safe and efficient heavy mineral separation and identification method according to claim 1, characterized in that: In S5, S6 and S7, the data acquisition process is a fully automatic operation and does not require human intervention.

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