The Application Of Airborne Gamma-ray Spectrometric Survey In Classification Of Geological Mapping Element In Shallow Overburden Area

Airborne gamma-ray spectrometric survey is a geophysical prospecting method. An airplane with airborne gamma-ray spectrometric instrument, according to advance surveying line and altitude, surveys gamma-ray spectrometric field on the air of some area to gain the content of uranium, thorium, potassium and the rate of total count of rock on the ground and U/Th, U/K, Th/K seven parameters, and then makes date processing and plots many parameter section chart, plane section chart, plane contour chart, solid chart, ratio chart, colorized correlation chart, colorized compose chart, gray scale chart ,shadow chart and so on, then makes qualitative and quantitative all-around explain about surveyed results according to the difference of physical character of rock or mine and geological, physical exploring, chemic exploring and telemetric data, to research geological construct character, primary stratum and territorial lithological partition in the area, and to provide important gist for forecasting mine perspective region and accurately reasonably disposing geological deposit researching work.Airborne gamma-ray spectrometric survey which is a relatively mature geological mapping measure plays an important part in geological mapping. But, there are several problems about making geological mapping using airborne gamma-ray spectrometric survey:Firstly, in our country, about forty percent area is overburdened. There are not only many "blind areas" using traditional measure in overburdened area, but also poor quality and efficiency.Secondly, in overburdened area, due to thick mantle of floating soil and vegetation, a small quantity of outcrop, it makes compartmentalizing geological unit difficult. At the same time, overlay layer affects gamma ray and it must be eliminated.Thirdly, at present, making geological mapping in overburdened area using airborne gamma-ray spectrometric survey is a fat lot.Fourthly, a few of measures of airborne gamma-ray spectrometric data processing, which of them are not mature and effective, need to be researched.So, the research on geological mapping in overburdened area using airborne gamma-ray spectrometric survey is very significative, which can solve some problems in the geological mapping.According to my specialty, in allusion to problem that compartmentalizing geological mapping unit is difficulty, poor veracity, inefficient, combining teacher's surveying item, this paper chooses that the application of airborne gamma-ray spectrometric survey in classification of geological mapping unit in shallow overburden as my master paper theme. In the paper, systematically expatiates how to use airborne gamma-ray spectrometric date to compartmentalize geological mapping unit in shallow overburden area, to provide some gist for field geological missionary compartmentalizing geological mapping unit.In overburdened area, dangerous condition of landform and terminal change, and affects field geological mapping work. Even if some areas can be compartmentalized, but it is hard to assure the efficiency and quality of mapping. Therefore, to solve the problem, I make use of airborne gamma-ray spectrometric survey date compartmentalizing geological mapping unit. It has the excellence that it can span any earth and can gain large superficial, precision homogeneous gamma-ray spectrometric date in a shot time. It is a high-speed, high efficient, much-information, and more efficient and lower cost method of geological survey and search mine in many case.The paper firstly looks back the development of airborne gamma-ray spectrometric survey in geological mapping in recent ten years. It mainly include several following aspect. Firstly, the history of airborne gamma-ray spectrometric survey in geological mapping, secondly, in recent ten years, the development of airborne gamma-ray spectrometric date processing method on abroad and home, thirdly, in recent ten years, the development of airborne gamma-ray spectrometric survey instrument and applied field of airborne gamma-ray spectrometric survey.The paper's principal part is mainly divided to four following part:Firstly, it mainly introduces geochemistry gist of airborne gamma-ray spectrometric survey in geological mapping in shallow overburden area. According to the character of airborne gamma-ray spectrometric survey, airborne gamma-ray spectrometric survey only can reflect the content of radioelement on the earth's surface (15-45cm). Therefore, when we uses the airborne gamma-ray spectrometric survey data, we don't only consider the extent of the mantle, but also must find out whether material component on the earth's surface can represent basal rock. Videlicet, if airborne gamma-ray spectrometric survey results in this area can't reflect radioactive character of basal rock under the earth's surface, the thought of making airborne gamma-ray spectrometric geological mapping in this area will be infeasible. Via to sum up former data and combine practical date data on this area, I approve that airborne gamma-ray spectrometric date up the overburden layer can reflect the content of basal rock's radioelement, and can distinguish the difference of basal rock. So we can use airborne gamma-ray spectrometric survey date to make geological mapping in overburden area, to compartmentalize different lithological geological element.Secondly, since it is already proved that geological mapping unit can be compartmentalized using airborne gamma-ray spectrometric survey results in this area, so we must understand the difference between in shallow overburden area and in lithological outcrop area using airborne gamma-ray spectrometric survey date. Videlicet, what influence is shallow overburden layer on airborne gamma-ray spectrometric survey results? Therefore, in the next chapter of the paper, the influence of shallow overburden layer on airborne gamma-ray spectrometric is introduced in detail, finally there are three primary aspects on the influence of shallow overburden layer on airborne gamma-ray spectrometric survey results: First, vegetation. Second, local interferer. Third, statistical fluctuate of radioactivity. These vegetation, local interfere and statistical fluctuate of radioactivity can be corrected to eliminate the influence of shallow overburden layer on airborne gamma-ray spectrometric survey.Thirdly, as far as the factors of the influence of shallow overburden layer on airborne gamma-ray spectrometric survey results mentioned above, it is detailedly expatiated that how to dispel these factors in the fourth chapter in the paper. By use of statistical analytical method to contrast the content of radioelement under the vegetation with in the exploratory trench , influencing coefficient that vegetation is corrected is gained .To dispel local interferer and statistical fluctuate of radioactivity, we adopt the method of slip average and the method of entropy average, contrastively deal with the airborne gamma-ray spectrometric survey data, and approve that the method of entropy average is better on suppressing the emergent data pinnacle when local interferer is dispelled. But for the wider abnormal apex of data, abnormity can be factually reflected, not to suppress abnormity lowly, at the same time, it is better to close to actual curve than the method of slip average for background value. Besides, in this chapter other aspects of the data are disposed to prepare for making classification of airborne gamma-ray spectrometric mapping unitFourthly, in the fifth chapter, how to compartmentalize geological mapping unit using airborne gamma-ray spectrometric survey data is mainly introduced. Primary method followed: First, compartmentalize geological unit using isoline map of uranium, thorium, potassium content and isoline map of rate of total count. Second, compartmentalize geological unit using isoline map of potassium variation coefficient. Thirdly, compartmentalize geological unit using isoline map of factor analysis score. Fourth, compartmentalize geological unit using the method of k-means dynamic cluster. Fifth, compartmentalize geological unit using the method of thorium-normalized. Finally, on the basic of those isoline maps, make a map of classification of radioelement content geological mapping unit closer to actual geological map, and make a statistics of radioelement data's character using much variable statistical method for every geological mapping unit, gain the average of the content of radioelement of every geological unit, to reach the quantitative purpose for the classification of geological mapping unit.The whole paper comparatively systematically analyses how to use airborne gamma-ray spectrometric survey to make a partition of geological mapping unit in the shallow overburden area, to provide a gist for field geological personnel to do the next work in this area, with definite direction significance for practice.