Estimation of uranium from multichannel spectra in airborne gamma ray spectrometry using 1.12 MeV and 1.76 MeV photopeaks of 214Bi — An application to Cuddapah Basin

Present study examines the utility of gamma rays of energies 1.12 MeV and 1.76 MeV of uranium in estimation of uranium in airborne gamma ray spectrometric survey (AGRS) in comparison to the conventional 1.76 MeV alone used world wide. As a case study, the AGRS data of northern part of Cuddapah Basin is considered. Multi-channel processing is applied on this dataset to reduce the spectral noise and use of combined 1.12 MeV and 1.76 MeV has reduced the Poisson’s related statistical error. Uranium is estimated using above two energies individually and in combination, using multi-channel processing followed by standard corrections procedure. Result indicates that a combination of both energies has given best estimation due to a reduction in overall noise which helped in demarcating geological entities and litho-contacts. This indicates the efficacy of this technique which improved the radio-geochemistry of study area in understanding the radio-elemental variation.     

NURE航空计划回顾与新时代航空γ能谱勘查启示

国家铀资源评价(NURE)计划实现了覆盖美国本土和阿拉斯加的1∶250000 NTMS图幅航空γ能谱测量和航磁测量,通过简要回顾该计划历程,重点针对NURE中航空地球物理勘查(航空γ能谱和航磁测量),讨论了航空地球物理勘查中测量技术、数据处理及解释方法等。NURE航空测量在铀矿勘查和辐射环境评价、洲际航空地球物理编图等领域发挥了巨大作用,产生了意义深远的影响。在总结NURE航空测量经验和做法的基础上,针对我国航空γ能谱测量勘查现状,建议从国家层面进行顶层设计,尽快实施我国陆域范围内的航空γ能谱和航磁框架性测量,实现对我国陆域航空γ能谱测量全覆盖,建设具有中国特色的航空γ能谱测量与监测体系。     

中国建成标定航空γ能谱仪的校正模型

我国第一个标定航空γ能谱仪的校正模型于1986年10月建成试用,1987年8月通过部级技术鉴定正式启用。本文较为详细地介绍了建造校正模型的依据,模型的设计及制作,模型的主要技术参数和基本特点,并对标定结果进行了评价。     

GR320γ能谱仪人工核素面源刻度

介绍了GR320γ能谱仪人工核素面源刻度原理和方法、刻度实验过程以及对刻度结果的应用。通过人工核素小面源模拟大面源的刻度,得到人工核素137 Cs和60 Co面源的效率因子,使GR320γ能谱仪在进行环境放射性γ辐射水平调查中能够定量给出人工核素137 Cs和60 Co的面活度。对新疆某地航测异常的地面验证测量结果表明,该航测异常地表确实存在人工核素137 Cs,且GR320γ能谱仪测量的面活度结果与该异常就地HPGe谱仪的测量结果基本相符。此法可推广到其它型号的便携式γ能谱仪的刻度,也可扩展到其它人工核素面源的刻度。     

Airborne γ-ray spectrometric characteristics of lithological units and environmental issues in the Bahariya Oases area in the northern part of western desert, Egypt

Two significant airborne gamma ray spectrometic (AGRS) statistical parameters, i.e., the arithmetic mean and the standard deviation, were computed for all lithologic units and formations of the Bahariya Oases area, Northern Western Desert, Egypt. The results ascertain that the maximum AGRS values are associated with sabkha sediments, Bahariya Formation, basalt flows and sand dunes. The intermediate values are correlated with El-Heiz, El-Hefhuf, Qazzun and Naqb formations. The minimum values are connected with Khoman Chalk and El-Hamra formations. The AGRS records were found to vary from one type of rock to another and to some extent between units of the same rock type too. On the aerial total-count (TC) radiometric maps, the records change from 6.2 to 69.36 μR/h. On the potassium map, the values range from 0.05% to 4.35%. On the equivalent uranium (eU) and equivalent thorium (eTh) maps, the records oscillate from 0.12 to 7.4 ppm and from 0.28 to 8.4 ppm, respectively. Concerning the Bahariya Oases area, the calculated arithmetic mean natural dose rate values originating from the terrestrial gamma radiation were found to range from 0.14 to 0.26 mSv/year and where the maximum value attains 0.62 mSv/year. These values remain on the safe side and within the maximum permissible safe radiation dose without harm to individuals, with continuous external irradiation of the whole body.     

Airborne gamma-ray and magnetic anomaly signatures of serpentinite in relation to soil geochemistry, northern California

Serpentinized ultramafic rocks and associated soils in northern California are characterized by high concentrations of Cr and Ni, low levels of radioelements (K, Th, and U) and high amounts of ferrimagnetic minerals (primarily magnetite). Geophysical attributes over ultramafic rocks, which include airborne gamma-ray and magnetic anomaly data, are quantified and provide indirect measurements on the relative abundance of radioelements and magnetic minerals, respectively. Attributes are defined through a statistical modeling approach and the results are portrayed as probabilities in chart and map form. Two predictive models are presented, including one derived from the aeromagnetic anomaly data and one from a combination of the airborne K, Th and U gamma-ray data. Both models distinguish preferential values within the aerogeophysical data that coincide with mapped and potentially unmapped ultramafic rocks. The magnetic predictive model shows positive probabilities associated with magnetic anomaly highs and, to a lesser degree, anomaly lows, which accurately locate many known ultramafic outcrops, but more interestingly, locate potentially unmapped ultramafic rocks, possible extensions of ultramafic bodies that dip into the shallow subsurface, as well as prospective buried ultramafic rocks. The airborne radiometric model shows positive probabilities in association with anomalously low gamma radiation measurements over ultramafic rock, which is similar to that produced by gabbro, metavolcanic rock, and water bodies. All of these features share the characteristic of being depleted in K, Th and U. Gabbro is the only rock type in the study area that shares similar magnetic properties with the ultramafic rock. The aerogeophysical model results are compared to the distribution of ultramafic outcrops and to Cr, Ni, K, Th and U concentrations and magnetic susceptibility measurements from soil samples. Analysis of the soil data indicates high positive correlation between magnetic susceptibilities and concentration of Cr and Ni. Although the study focused on characterizing the geophysical properties of ultramafic rocks and associated soils, it has also yielded information on other rock types in addition to ultramafic rocks, which can also locally host naturally-occurring asbestos; specifically, gabbro and metavolcanic rocks.     

Radioelement Mapping and Environmental Monitoring of Surface Deposits using Ground Gamma Ray Spectrometry of the Area Adjacent to El‐Ramlah Village,Southwestern Sinai,Egypt

A ground‐based gamma‐ray survey has been performed in the area close to El‐Ramlah village, southwestern Sinai, Egypt, using a GS‐512 spectrometer. The main objective of this survey was to delineate radioactive anomalies within the surface of the study area and to identify the environmental effects of natural radioelements on the new inhabitants, Bedouins, who live in the recently built village in this region of the Sinai Peninsula. The results show that the maximum radioactivity of the total count component (T.C.) was about 15.7Ur at the northern part of the study area. The average radioelements concentration were 0.4% for potassium, 1.6 ppm for equivalent uranium and 4.5 ppm for equivalent thorium. To identify and map the environmental effects of the concentration of these radioelements on El‐Ramlah village, measurements of potassium (K%), equivalent uranium (eU) and equivalent thorium (eTh) were converted into an equivalent dose rate. The results illustrate that, the levels of effective dose rate of the natural radioactivity of the area of study remains in the safe range without any harm to living organisms, and it stays within the maximum permissible radiation dose rate (1.0 mSv y^?1) recommended by the International Commission of Radiological Protection.     

Impact of the pre-processings on the fractal properties of the airborne gamma ray measurements: a case study from Hoggar (Algeria)

The analysis of gamma ray measurements provides valuable information about the basement’s lithospherical model and the radioactive elements contained in the subsurface. To be exploited, the raw data need pre-processing operations which consist of corrections of the Compton effect, altimetry and the aircraft background, and 2D interpolations. These transformations may modify the data’s stochastic component which reflects heterogeneities of the investigated medium. In this study, a fractal analysis is carried out on airborne gamma ray data measured in the Hoggar’s area (Algeria). First, it is shown that the analyzed data exhibit fractal properties. Due to the dependence of the latter on the spatial location of the measures, the data can be considered as paths of multifractional Brownian motions. Another result worth noting is that the fractal nature of the raw data is not modified by the pre-processing operations. The fractal analysis can be then performed on the raw spectrometric measurements without submitting them to any pre-processing; thus, the stochastic component of the measurements is kept intact.     

Aerospectrometric and aeromagnetic characteristics associated Nb–Ta–Sn mineralization, G. Nuweibi albite granite Central Eastern Desert, Egypt

A geophysical signature associated with Nb–Ta–Sn mineralization of G. (G. : abbreviation to word Gebel which means mountain in Arabic) Nuweibi area, located the Central Eastern Desert of Egypt is presented. This signature was established by an integration of airborne gamma ray spectrometric and magnetic data. Variations seen in the gamma ray spectrometric data are used as a base to study the three granitic suites: younger-, albite-, and older granites in G. Nuweibi area. Graphical techniques such as frequency histograms and box-plots are used to visualize the shape of the distribution and determine the anomaly thresholds of the three radioelements eU, eTh, and K% data in these granitic suites. The box-plot graphical representations and calculations made on data sets indicate that no samples have eU values above the thresholds, i.e., no outliers representing values of the box-plots. Nuweibi albite granite is associated with a gamma ray response that includes the strongest eU, eTh, K%, and eTh/K ratio anomalies in the study area. K–eTh plot shows that the albite granite has a higher eTh concentration than the older and younger granites. The increase in K concentration and raise in Th/K ratio of Nuweibi albite granite points to unusual geological processes leading to mineralization and reflects the highly fractionated nature of the magma which results in thorium enrichment. This also reflects that K alteration associated with Nb–Ta–Sn mineralization is both poorly focused spatially and very much weaker than observed in any other mineralizing districts. The distribution of magnetic sources and their locations and depths in the study region are determined by Euler deconvolution and analytical signal techniques. Good clustering of Euler solutions were obtained using SI?=?0.5 and SI?=?1.0 for most of the features in the area under consideration. The solutions obtained have shown magnetic sources which can be related to the impact structure whose depths varies between ground surface to 1.66 km. The analytical signal revealed that the metamorphosed basic rocks (mainly olivine metagabbro), serpentinite and dyke bodies are the main sources of high magnetic anomalies, particularly within the area east G. Nuweibi region.     

航空伽马能谱测量方法技术现状与展望

简要地介绍了国内外航空伽马能谱测量方法技术的发展现状,尤其是近年来航空伽马能谱测量在仪器研制、数据处理与资料解释方法技术及应用领域等方面取得的最新进展,并结合我国当前地质找矿工作的需求,提出今后一段时期我国航空伽马能谱量测工作的重点应着眼于加强区域性航空伽马能谱测量工作,重视资料的二次开发利用及拓展新应用领域;要作好仪器国产化之后的实用化开发,及加强航空伽马能谱测量新方法技术研究。     

Data Analysis of Chang’E-1 Gamma-Ray Spectrometer and Global Distribution of U, K, and Th Elemental Abundances

Gamma-ray spectrometer (GRS) is one of the main payloads on the Chang’E-1 (CE-1) lunar probe, mainly aimed to detect the elemental abundances and distributions on the lunar surface. At 03:58 on 28 November 2007, it performed the first observation of the lunar gamma rays. As of 24 October 2008, 2105?h of effective gamma rays spectra had been acquired by CE-1 GRS, which covers the whole surface of the moon. This paper mainly describes the data processing procedures and methods of deriving the elemental abundances by using the CE-1 GRS time series corrected spectra: first, to bin data into pixels for mapping; then, to perform a background deduction of the cumulative spectra and obtain a peak area of the elements; and finally, to use the elemental abundances inversion model to produce the elemental abundances. Based on these processing methods, the global abundance maps of U, K, and Th at a 5°×5° equal-area pixel are acquired by CE-1 GRS data. The paper gives a preliminary analysis of the uncertainties of the elemental abundances     

Characterization and disequilibrium cases of radioelements in some Syrian hot waters

The radioactive and physical characteristics of Syrian hot waters were studied. The concentration of uranium, its daughters and the ²³⁴U/²³⁸U-activity ratios in the hot waters were measured by gamma and alpha ray spectroscopy. The ²³⁴U/²³⁸U-activity ratios showed that uranium in Syrian hot waters are in an equilibrium state. Some anomalous observations of these ratios were explained by former leaching of the uranium from Cretaceous phosphates by underground water. Also, the results showed that the temperature of the studied hot waters was independent of the contained radioelements. The temperature of hot waters is explained by the passing of these waters near the hot spot or by the relationship between the geological deposit of the aquifer rocks and the waters rather than the contents of the radioelements.     

宁安盆地航空伽马能谱特征及铀成矿远景预测

利用最新的航空伽马能谱数据,分析了宁安盆地以及501铀矿床的航空伽马能谱特征。并利用铀转换参数(初始铀、活性铀、铀迁移系数)分析了本区的铀源条件,结合盆地基底、构造、岩相岩性、水文地质等成矿条件进行了铀成矿分析和远景预测。最终预测了3处铀成矿远景区段,对本区进一步找矿具有指导意义。     

Enrichment characteristics of radioelements in various types of rock from Sambalpur district,Orissa, India

Over the years a large number of rock samples were collected by the explorationists of Atomic Minerals Directorate for Exploration and Research (AMD), Department of Atomic Energy from Sambalpur district, Orissa, India. The variation of uranium enrichment with various types of rock in these samples was studied with an aim to help quick reviewing of toposheets in case of newly taken up areas, for uranium exploration. The radioelements U, Th and K determined for these samples are plotted in ternary diagrams for classifying them as being uraniferous or thoriferous with respect to various type of rocks, keeping the total natural content of radioelements (expressed by eUP₃O₈) as a parameter. In this study it is seen that samples of quartzofeldspathic breccia type are enriched in uranium irrespective of their further sub classification and eU₃O₈ content. Granites are enriched in thorium when eU₃O₈ < 100 ppm and are enriched in uranium when eU₃O₈ > 100 ppm. A database prepared for this purpose may be useful for reviewing toposheets in future     

山东黄河口地区环境放射性辐射水平及评价

依据山东黄河口地区航空物探综合测量结果,阐述了航空伽马能谱资料在评价环境放射性辐射水平、圈定放射性污染范围等方面的应用方法及效果,指出该区虽天然本底辐射水平较低,但区内多处发现的放射性异常,则是引以关注的环保问题。     

Background deduction of the Chang’E-1 gamma-ray spectrometer data

Gamma-ray spectrometer(GRS) is used to detect the elemental abundances and distributions on the lunar surface.To derive the elemental abundances,it is vital to acquire background gamma rays except lunar gamma rays.So GRS would observe background spectra in the course of earth-moon transfer on schedule.But in fact,GRS was not switched on in the course of flying toward the moon.After the CE-1 probe finished one-year mission,GRS car-ried out a test on background data on November 21?22,2008.The authors did conduct research on the methods of background deduction using 2105 hours of usable gamma-ray spectra acquired at the 200-km orbital height by the GRS and more than 5 hours of gamma-ray spectra acquired in the GRS background test.The final research results showed that the method of deducting the background using the minimum counts in the CE-1 GRS pixels is optimal for the elements,U,K and Th.The method applies to such a case that the elemental abundances in the pixel with the minimum counting rate are 0 μg/g and the continuum background counts are constant over the Moon.Based on the method of background deduction,the full energy peak counts of U,K,and Th are calculated.     

A STUDY OF AIRBORNE RADIOACTIVE SURVEYING

Airborne radioactivity surveys by the Geological Survey of Japan have already [1960] covered an area of about 90, 000 sq. km . On the basis of a semi-empirical theory on attenuation of gamma rays, with reference to the effect of scattering, the intensity distribution of gamma rays in the atmosphere was calculated by assuming several ideal forms of sources. 3 The fundamental constants in the theory are determined so as to conform to the relationship between the altitude and the experimental values of gamma ray intensity. From the results of calculations, the relationship between the altitude and the intensity of atmospheric gamma rays originating in a uniformly widespread source are discussed, and altitude correction is examined. It is concluded that the altitude correction is affected by the topographic variations, the existence of a thin surface layer, and by the variation of quantities of atmospheric radioactive materials. Anomalous gamma ray intensity, as observed in the airborne survey, and the determination of flight line intervals are briefly mentioned. Additional mention is made on the airborne survey over the rugged mountainous districts of Akita and Niigata prefectures, and on the test flight of a large size aircraft for the purpose of precise surveying. --Auth.     

Determination of uranium, thorium and potassium contents in rock and soil samples using low-energy gamma ray spectrometry

A low-energy gamma ray spectrometric set-up for determination of uranium, thorium and potassium in rock and soil samples is described. The procedure described exploits the fact that a large proportion of gamma quanta produced in the Th and U decay series have energies of less than 1 MeV. The instrumental parameters such as sensitivity and detection limits for the low-energy region have been studied. The measuring conditions were optimized by suitably minimizing the background and by increasing the overall sensitivity with the help of proper geometry of measurement and sample parameters. High sensitivity and low detection limits for U and Th can be achieved using low-energy gamma ray spectrometry. The method provides a rapid analysis with a counting time of the order of a few minutes for each sample.     

航空物探在珠海-深圳地区浅层水资源环境评价中的应用

珠海-深圳地区位于广东省南部,由于多种原因,浅层水资源遭受严重污染,淡水资源不足,致使当地人民生活用水和工农业用水比较紧张,制约着该区的经济发展.为了了解该区水资源状况,近年来应用航空综合物探(航磁、航空电磁和放射性伽马能谱)测量技术,快速有效地查明了该区海侵范围和浅层地下水的水质和淡水区的划分与分布,并对地下热水资源进行了预测,为全面了解该区水资源状况提供了可靠的基础资料,对科学地评价浅层水资源环境具有重要作用.     

柴达木盆地自然伽玛曲线在古气候及沉积环境研究中的应用

应用自然伽玛测井（GR）曲线反演古气候和古环境的方法在国际上逐渐得到重视并取得了进展，柴达木盆地第四纪应用其反演2.85Ma B.P来的古气候变化也取得了成功。本文以柴达木盆地侏罗系冷科1井和雨33井自然伽玛曲线并结合孢粉等地质资料进行了古气候与沉积环境分析，证明GR曲线是有价值的古气候研究参数。GR值的大小及古气候的干湿变化和沉积水体的深浅变化均有内在联系，GR曲线振幅与频率的变化快慢反映出沉积环境动荡与稳定的相对特征，据此对两口井的沉积环境演变作了具体分析。结合古气候与沉积环境综合分析，GR曲线的异常波动还具有特殊的指相意义。GR值增大-古气候加湿-沉积水体加深的同步表现特征是一般性规律，构造-古地理背景的变动可改变这一对应关系，因而提供了研究古地理演变的信息，进一步丰富了GR曲线研究的地质涵义。说明在侏罗纪古气候和古环境研究上，GR曲线是一有价值的参考指标。