RU2226282C2 - Geochemical method exposing inhomogeneities (variants) - Google Patents

Abstract

FIELD: geochemical examination methods utilized to reveal deposits of mineral wealth, to detect tectonic, anthropogenic and other structural-material inhomogeneities of geosphere. SUBSTANCE: mobile particles contained in atmospheric layer above surface, coming from area of inhomogeneity, migrating towards day surface and arriving in air, which presence is coupled to this inhomogeneity or caused by its existence are collected by pumping of free air through sampler. Particles with size under 0.05 mcm are sampled for analysis. Ii is most convenient to collect particles on graphite dish that can be placed into electrothermic spray gun of atomic-absorption spectrophotometer. Contents of elements accompanying sought-for inhomogeneity are found and change in contents of elements is utilized to establish presence, nature and parameters of inhomogeneity. According to second variant not contents but ratios of contents of determined elements are established. Elements-indicators are selected in each particular case in correspondence with specified task. EFFECT: development of simple and economic method to expose inhomogeneities of earth's crust of various natures. 6 cl, 6 dwg

Description

The method relates to geochemical research methods and can be used to identify mineral deposits, as well as tectonic, anthropogenic and other structural-material heterogeneities of the geosphere.

It is known that from the depths of deposits of solid and liquid minerals to the day surface there is a flow of moving particles that carry information about the object. For example, in US patent No. 4587847 and an article by Malmquist et al. "Geogas prospecting - an ideal industrial application of PIXE" (Nuclear Instruments and Methods, B, 150 (1999), p. 444-490), this stream is called geogas, in article by Wang et al. "Nanoscale metals in Earthgas and mobile forms of metals in overburden ..." (Journal of Geochemical Exploration, 58 (1997), pp. 63-72) - by terrestrial gas, in RF patent No. 2097796 - by jet vertical migration of chemical elements, in US patent No. 4573354 refers to the flow of volatile compounds emanating from an underground source. There are methods of geochemical studies using this phenomenon.

There is a known geochemical method for searching for hydrocarbons according to the patent of the Russian Federation No. 2097796 (IPC G 01 V 9/00, prior. 04/03/96), in which samples are taken from different soil horizons on the studied area at each observation point and indicator elements are extracted from them hydrocarbons associated with organic compounds of the soil, select elements in electromobile forms of finding, determine the concentration of pre-installed indicator elements in each of the extracts and by the coincidence of zones with abnormal concentrations of indicator elements and elements Comrade in electrically mobile forms of location establish the boundaries of oil and gas provinces, regions, fields or individual deposits. This method is time-consuming, since it requires sampling from various depths, installing special electrodes for sampling elements in electromotive forms and conducting a large number of chemical analyzes.

A known method of searching for ore mineral deposits by and.with. USSR No. 1322846 (IPC G 01 V 9/00, prior. 12.07.85). in which ore components are accumulated on the electrode discretely moving along the studied profile, the measurements being made in the surface air layer, purging the electrodes with equal volumes of air during each measurement, the concentrations of the accumulated components are determined and the presence of deposits is judged by their values. This method is quite simple and productive, but is intended only for the search for ore deposits.

There is also a known method of geophysical exploration according to the USSR patent No. 1764436 (IPC G 01 V 9/00, prior. September 7, 899), in which air samples are taken from the surface layer of the atmosphere, aerosol particles are filtered over 0.2 μm, and the particles that are sampled are ionized. particles with an energy effect of not more than 14 eV, less than the minimum ionization potential of a mixture of atmospheric gases, measure the total number of ionized particles, which is taken as the physicochemical characteristic of the medium. The disadvantage of this method is that many factors influence the magnitude of the ionization current, for example, humidity and the presence of gas components having the same ionization potential as gaseous ore components. This can lead to unreliable results. In addition, the impossibility of the accumulation of the mass of moving particles necessary for the operation of the analytical instrument above the detection limit, can lead to the omission of detected discontinuous violations. The main disadvantage is the fundamental impossibility to determine the nature of the detected heterogeneity.

The closest to the intended purpose is a method for detecting hidden deposits according to US patent No. 4587847 (IPC G 01 N 33/24, prior. PCT application No. 83/01309 from 09/30/82). In this method, to detect hidden deposits, a stream of particles ascending from the depths (ions, atoms or aggregates of atoms) of interest for the study is collected on a sampler isolated from the atmosphere below or above the surface level. Particles collected for a long time on the membrane are analyzed on a proton accelerator and the presence of hidden deposits is determined by the obtained contents of indicator elements. The disadvantages of the method are the duration of the accumulation of material for analysis, the ability to collect material only at fixed points, expensive analysis. This method, like the previous ones, is offered only for the search for mineral deposits.

The task is to create a simple and economical way to identify heterogeneities of the earth's crust of various nature.

The problem can be solved in two ways.

In the first embodiment, in a method for detecting inhomogeneities, including the accumulation of particles, the appearance of which is associated with these inhomogeneities, elemental analysis of the accumulated material and determining the presence, nature and parameters of heterogeneity from the detected change in the contents of the elements being determined in the accumulated material, the particles are collected by pumping free air from the surface layer atmosphere through the sampler as it moves along the selected profile within the sampling area, and for analysis ayut particle size of not more than 0.05 microns, which collect in the graphite cuvette.

In the second embodiment, in the method for detecting inhomogeneities, including the accumulation of moving particles, the appearance of which is associated with these inhomogeneities, and the analysis of the composition of the accumulated material, the ratios of the contents of the elements being determined in the accumulated material are determined, and the presence, nature and parameters of the heterogeneity are determined by the detected change in the ratios of the contents of the elements, moreover, the particles are collected by pumping free air from the surface layer of the atmosphere through the sampler when it moves in crystals sampling area, wherein the particles are selected for analysis, not larger than 0.05 microns, which collect in the graphite cuvette.

It is most convenient for elemental analysis to place a graphite cuvette with the material accumulated on it in the electrothermal atomizer of a multi-element atomic absorption spectrophotometer. This avoids wet chemical operations. In this case, the graphite cell will be a container of moving particles, since they can be stored in it for a long time.

Elemental analysis can be carried out by other methods (for example, atomic emission or X-ray spectral). For this, the material accumulated on the cuvette must be transformed into a form suitable for these types of analysis.

Particle selection from the surface layer of air is known from A.S. USSR No. 1322846, however, there it was used only for the search for ore deposits.

For this, it was only necessary to isolate the components of the corresponding ores on the electrode and determine their concentration at each measurement point. However, not only the components of the corresponding ore, but also other elements can indicate the presence of a deposit of a certain ore. So, for example, arsenic, selenium or tellurium may indicate the presence of a gold ore deposit. In this case, as well as in the case of non-metallic deposits, the presence of elements indicating the presence of these deposits was not known in the surface layer of air. To establish this fact, as well as the composition of these elements, additional studies were required.

The advantage in relation to the method according to the USSR patent No. 1764436 is the accumulation of particles, which makes it possible to work confidently above the detection limit of the analytical instrument, and the determination of their chemical composition, which allows you to establish the nature of the detected heterogeneity.

All of the above analogues are designed to search for mineral deposits. However, studies of the authors of the proposed solution showed that, in the case of other types of structural-material heterogeneities, the flow of moving particles of a certain composition also rises to the day surface from the heterogeneity region, which made it possible to use the determination of element contents in the surface layer to search for structural, geodynamic, and anthropogenic inhomogeneities of the earth's crust.

A very important sign regarding the size of the most informative moving particles. It was experimentally established that the use of particles smaller than 0.05 microns in size to maximally separate particles of technogenic origin and gives more contrasting anomalies. Thus, the restriction of particle size allows you to detect anomalies without repeated measurements, which is difficult when taking measurements according to the USSR patent No. 1764436.

Figure 1 presents a diagram of a sampler for collecting particles. 1 - graphite cell, 2 - electrode, 3 - discriminator, 4 - air micropump, 5 - timer, 6 - high voltage source.

Figure 2 shows the hydrocarbon reservoir (1) and its geochemical manifestation in soil gases (2), in soils (3) and in above-ground air (4).

Figure 3 - distribution of the total contents of potassium, calcium and zinc in the soil above the air over the tectonic fault. (1) - the content of elements in samples, including particles no larger than 0.05 microns in size. (2) - the content of elements in samples, including particles of all sizes.

Figure 4 - the manifestation of anthropogenic anomalies in the above-ground air on the example of cadmium-containing waste. (1) - the content of elements in samples, including particles no larger than 0.05 microns in size. (2) - the content of elements in samples, including particles of all sizes.

Figure 5 - the manifestation of the gold ore deposits in the above-ground air according to the absolute contents of gold and silver (1) and the ratio of the contents of gold and silver (2).

Figure 6 - relations of the contents of elements in air samples over faults of various tectonic nature.

To implement the method, it is necessary to perform the following operations.

In the first version:

1. Free air is pumped through the sampler from the surface layer of the atmosphere. At the same time, it contains accumulated in this layer heterogeneities coming from the region, migrating in the direction of the day surface, and moving particles entering the air, the presence of which is associated with this heterogeneity or due to its existence. The sampler is moved along the selected profile or area with the selected step or continuously at the same height. In this case, the result will be averaged over the section of the profile or area. For analysis, particles no larger than 0.05 microns are selected. As a particle discriminator, you can use a filter, impactor, etc. It is most convenient to collect particles on a graphite cuvette, which can be placed in the electrothermal atomizer of a multi-element atomic absorption spectrophotometer.

It is possible to determine the contents of elements also by atomic emission analysis or X-ray spectral analysis. In this case, it is also convenient to use a graphite cell for the accumulation of moving particles from the air. This allows you to unify sampling for various analysis methods. The accumulated material must be converted into a form convenient for analysis (for example, rinse to transfer to a liquid form).

In all cases, it is necessary to accumulate such a mass of particles that ensures the operation of the analytical instrument above the detection limit.

2. The absolute contents of the elements are normalized to the volume of air pumped through the sampler in a given section of the profile or area.

3. The contents of the elements associated with the desired heterogeneity are determined, and the presence, nature and parameters of the heterogeneity are determined by the detected change in the contents of the elements.

In the second embodiment, it is not content that is determined, but the content ratio of the elements being determined. In this case, there is no need to consider the volume of air pumped through the sampler.

The composition of particles in the surface air layer is associated with the nature of the detected heterogeneity, and the choice of indicator elements in each case is determined by the geological task. For example, it is known that a specific set of elements is concentrated in the fault zones (I. Buldakov, Tectonochemical mechanism of the formation of magmatogenic ore deposits. - L .: Leningrad State University, 1979, 203 pp.). It is also known which metals accompany hydrocarbon deposits (Nadirov N.K. et al. Metals in oils. - Alma-Ata: Nauka, 1984, 256 pp.). In the case of anthropogenic inhomogeneities, the composition of particles in the near-surface air layer is determined by the composition of the inhomogeneity.

The sampler device, which allows determining the content of elements in the surface air layer (Fig. 1), contains a graphite cuvette 1, a corona electrode 2, a particle discriminator 3, an air micropump 4, a high voltage source 5 and a timer 6. The micropump 4 pumps air through the soil through graphite cell 1. An electrode 2 is coaxially located in the cell, to which a high voltage is supplied from source 5. At the end of the electrode 2, a corona discharge arises, charging the flying particles, and they are deposited on the inner surface of the graphite cell 1. Choose the optimal pumping speed at which the particles are deposited on the walls of the cell. At the selected speed, timer 6 allows you to select the amount of air needed to solve the problem.

As an example, figure 2 shows the results of the study of above-ground air over a hydrocarbon reservoir (4). The same figure shows the distribution of electromotive forms of elements in soils, determined by the method described in RF patent No. 2097796 (3).

It is known that there is an extended vertical zone above the hydrocarbon deposit, where a whole complex of physical, chemical, microbiological, and geochemical processes appear in the overlying deposits, which form redox barriers and a specific association of newly formed mineral and organomineral complexes. It is believed that these phenomena are associated with the processes of subvertical fluid migration from a hydrocarbon reservoir. Ultimately, this process finds its manifestation in the rocks in the form of more or less contrasting geophysical, geochemical and mineralogical heterogeneities. We found that hydrocarbon deposits and related heterogeneities are also manifested in the elemental composition of the above-ground air.

The data shown in figure 2 indicate that over the flank and central part of the deposits in soils and in the above-ground air, elevated concentrations of zinc, lead and copper are manifested. In this case, the oil – water (HB) and oil – gas (NG) boundaries are distinguished for the deposits. The phenomenon of increasing mineralization and the formation of a geochemical anomaly in the HB border zone is known from geological exploration practice and is explained in terms of processes occurring at the boundary of two media (Gottikh R.P. Radioactive elements in oil and gas geology. - M .: Nedra, 1980).

We draw attention to the fact that the indicated geochemical regularity is more clearly manifested in the subsoil air than in the soil: for HB and NG soils, contacts are shown only at 1-2 sampling points, while for the suprasoil air, these sections of the sampling profile are more reliable and confirmed in 5-7 points.

One of the varieties of the heterogeneity of the earth's crust is geotectonic faults. According to geochemical studies, it is known that a specific set of moving elements is concentrated in fault zones. From this set, those that produce the most contrasting anomalies can be selected.

Figure 3 shows an example implementation of a method for detecting tectonic heterogeneity. An abnormal content of potassium, calcium, and zinc was found in the study of the composition of the surface soil air over the profile in some of the analyzed air samples. Studies have revealed the existence of an active tectonic fault in this zone. An anomaly was detected for particles no larger than 0.05 μm in size (1). In air samples containing particles of all sizes, the anomaly over the tectonic zone manifested itself in much less contrast (2).

It is convenient to use the proposed method for identifying anthropogenic heterogeneities. Figure 4 shows the results of the study of above-ground air within the territory of storage of industrial waste. It was known that materials with high cadmium contents accumulated over long periods in certain areas of the territory. In this case, traditional geochemical and ecological-chemical methods are ineffective for identifying ecologically dangerous zones - the extreme heterogeneity of the spatial distribution of pollution and the analytical problems caused by this circumstance interfere (for representativeness it is necessary to choose a very small sampling step and take a large amount of material for the sample).

The implementation of the proposed method allows us to solve these problems. As can be seen from the data shown in figure 4, over the site with waste in the air observed anomalies of cadmium. It is noteworthy that contrasting anomalies appeared in the surface air even above the pond. Moreover, the anomalous zone above the cadmium-containing wastes was detected in air samples containing particles of not more than 0.05 μm (curve 2). When analyzing air containing a spectrum of particles of all sizes, the local pollution zones turn out to be “smeared” (curve 1).

Figure 5 presents the results of determining the ratio of the contents of gold and silver in the above-ground air above the zonal gold ore deposit. It is seen that when using the ratio of the elements, the anomaly is manifested in more contrast.

Figure 6 presents the results of a study of two fault systems that differ in their geodynamic parameters. They differ in the ratio of sodium to potassium in the above-ground air over the zones of these faults. The fault system, representing the oceanic paleogeodynamic setting, is characterized by sodium specialization (the ratio of sodium to potassium is 3.0). At the same time, air above faults of the continental-type crust of the earth is characterized by relatively high potassium contents (the ratio of sodium to potassium is 2.1).

The above examples confirm that conducting elemental analysis or determining the relationships of elements of the surface air layer allows traditional methods of analysis to effectively identify mineral deposits, as well as tectonic, geodynamic and anthropogenic and other structural-material inhomogeneities.

Claims (5)

1. A geochemical method for detecting inhomogeneities, including the accumulation of moving particles associated with a detectable heterogeneity, elemental analysis of the accumulated material and establishing the presence, nature and parameters of heterogeneity from the detected change in the contents of the elements being determined in the accumulated material, characterized in that the particles are collected by pumping free air from the surface layer of the atmosphere through the sampler when it is moving within the sampling area, and for analysis, selected particles with a size of not more than 0.05 μm, which are collected on a graphite cuvette. 2. A geochemical method for detecting inhomogeneities, including the accumulation of moving particles associated with the detected heterogeneity, and analysis of the composition of the accumulated material, characterized in that they determine the ratios of the contents of the elements being determined in the accumulated material, and the presence, nature and parameters of the heterogeneity are determined by the detected change in the ratios of the contents of the elements moreover, the particles are collected by pumping free air from the surface layer of the atmosphere through the sampler when it moves into thinning area sampling, and assay are selected particle size not greater than 0.05 microns, which collect in the graphite cuvette. 3. The method according to claims 1 and 2, characterized in that the material accumulated on the cuvette is analyzed by atomic absorption method. 4. The method according to claims 1 and 2, characterized in that the material accumulated on the cuvette is analyzed by the atomic emission method, having previously been converted into a form convenient for this. 5. The method according to claims 1 and 2, characterized in that the material accumulated on the cuvette is analyzed by the X-ray spectral method, having previously been converted to a convenient form for this.

Images