Ground Gamma-ray Spectrometry Research Articles

Comparison of two gamma-ray datasets measured with different methods and assessment of their performance to predict soil properties

ABSTRACT Terrain mobility is directly dependent on soil properties, i.e. stoniness, soil particle size and peat depth. Gamma-ray spectrometry has been widely used in soil mapping as gamma-rays can penetrate up to 50 cm of soil. The method has proven to be effective in gathering information on various soil properties, such as clay and silt content, organic carbon content, soil pH, and soil stoniness. The intensity of gamma radiation decreases with increasing soil moisture content, which is important when assessing the load-bearing capacity of forest terrain, which affects the quality and planning of mechanized wood harvesting. In this study, we compared two gamma-ray datasets that were acquired from the same plots but measured with different methods: airborne gamma-ray spectrometry and a handheld gamma-ray spectrometer. Regression analyses were used to examine whether the gamma-ray datasets have significant similarities. Linear discriminant analysis was then used to study the performance of the two gamma-ray datasets when predicting different soil properties (stoniness index classes (SIC), soil depth, and peat depth). Our correlation analysis produced R2 values of 0.18–0.29 and root mean square error (RMSE%) values of 0.48–0.55. Prediction of SIC was 67.1% accurate with ground gamma and 45.9% accurate with air gamma. For soil depth predictions, the accuracies were 64.7–70.0% for ground gamma and 61.7–63.5% for air gamma. Our findings showed that ground gamma-ray spectrometry is better at predicting soil properties than air gamma-ray spectrometry.

Estimation of population exposure to terrestrial gamma rays in Canada

Based on ground gamma ray spectrometry surveys conducted from 2007 to 2010 in populated areas across Canada (i.e. in southern Canada, excluding the northern territories), and with consideration of the exposure outdoors and indoors in various types of buildings as well as exposure to radionuclides in building materials (assuming most building materials are of local origin), the population-weighted annual effective dose from exposure to terrestrial gamma rays was estimated to be 167 ± 43 μSv. Under Canadian-specific average occupancy times, indoor exposures at home contribute 69% of the total annual effective dose, followed by 19% from indoor exposures other than at home, 6.2% from outdoor exposures and 5.8% from exposures inside vehicles. This assessment with measurements in a total of 1057 sites in populated areas across Canada is in general agreement with earlier assessments based on airborne gamma surveys mostly over unpopulated areas of Canada and truck-borne radiometric surveys along paved urban roads in four cities.

Gamma-ray spectrometry of the Araguainha impact structure, Brazil: Additional insights into element mobilization due to hydrothermal alteration.

We present the analysis of airborne and ground gamma-ray spectrometry signatures of the Araguainha impact structure, located in central Brazil, the largest impact structure in South America with ~ 40 km diameter. The airborne data are total gamma-ray counts per second collected along flight lines spaced 1 km apart. The ground gamma-ray data are concentrations of potassium, uranium, and thorium isotopes calculated from radiations measured in three individual channels. The objectives are to distinguish lithologies within the structure, which have naturally distinctive radiogenic signatures, and identify potential post-impact hydrothermal alteration zones, as indicated by high K concentrations. Based on results obtained by numerical modeling of the crater formation, we infer the locations of potential occurrences of target rocks that may have undergone hydrothermal alteration as a result of the impact. The deviations from the background potassium concentration show significant anomalous K values at the center and in the northwestern crater rim, where high concentrations of U are also observed. The numerical model shows that ideal temperature conditions for hydrothermal fluid circulation were attained right after pos-impact gravitational stabilization.

Radioactivity, radiogenic heat production and environmental radiation risk of the Basement Complex rocks of Akungba-Akoko, southwestern Nigeria: insights from in situ gamma-ray spectrometry

The Basement Complex rocks of Akungba-Akoko, southwestern Nigeria, typically migmatites (M), biotite gneisses (BGN), granite gneisses (GGN), charnockites (Ch), biotite granites (BG) and pegmatites (P), were assessed using ground gamma-ray spectrometry (GRS). This study aimed at determining rocks’ radionuclides concentration, alterations, radionuclides mobilization, radiogenic heat production (RHP) rate (first report for the area) and environmental radiation risk to humans. The results of this study were integrated with previous data on the petrography and geochemistry of these rocks, for detailed interpretation. The results of average elemental and activity concentrations for Akungba-Akoko rocks, were 2.66%, 3.16 ppm and 13.98 ppm, and 831.35, 39.01 and 56.77 $$Bq{kg}^{-1}$$ for 40K, 238U and 232Th, respectively; with increasing rock order of Ch < M < GGN < BGN < P < BG. High radionuclides concentration in the rocks, with exception of charnockites, were determined by high amount of K-feldspar, plagioclase, biotite and accessory minerals—zircon and monazites. On the other hand, the low radionuclides concentration in the rocks, especially in Ch and M, were aided by the variability of the naturally occurring radioactive elements (NORMs) caused by alterations and mobilization during metamorphism and crystallization processes as suggested by radioelements composite, K/eTh ratio and F-parameter of Efimov analyses. RHP average of 2.03 $$\mu W{m}^{-3}$$ above the crustal average range of 0.8–1.2 $$\mu W{m}^{-3}$$ may have significantly contributed to the heat flux in the studied area; however, the RHP of charnockites are lower than the crustal range. The absorbed dose rate average of 87.98 $$nGy{ h}^{-1}$$ was within the permissible range, and other estimated radiological parameters, namely annual effective doses, hazard indices, gamma activity and activity utilization index, were all far below the permissible limit of 1 $$mSv {y}^{-1}$$ for these rocks. However, the annual gonad dose equivalent (618.874 $$\mu Sv{ y}^{-1}$$ ) and excess life cancer risk (1.511 × 10− 3) were above their permissible limits. Due to the high gamma radiations from the pegmatitic and biotite-rich rocks in the studied area, their high usage should be reduced. Hence, periodic monitoring of the study area is advised.

Gamma-ray spectrometric survey for mineral exploration at Baljurashi area, Saudi Arabia

ABSTRACT Mineral resources exploration in the Kingdom of Saudi Arabia became an important target for the Saudi government. Nowadays, the economic vision of the country is to move away from oil-based country to multisource energy-based country. In Baljurashi area there were ancient mines for Copper, Cobalt, Magnesium, Zircon, and some other minerals. In the current study, we aim to evaluate the Baljurashi area in terms of mineral resources using the advanced technique. Consequently, we carried out ground gamma ray spectrometry survey in an area of about 50 km2, elevation variation ranges from 380 m to 2280 m above the sea level. We used the RS-700 system to collect the gamma ray spectrometry data. In addition, we used the existing geochemical analysis results for this area and integrated the results to map the most important minerals. The integration work indicates that the area of Baljurashi is rich in mineral resources. The mineralization zones are located in the eastern part of the area where elevation is high (e.g., east of the escarpment). We also found that these mineralization zones are structurally controlled. Important mineral maps were produced (e.g. Cu, Cr, Mn, and Zr). We highly recommend more geophysical studies to evaluate the Baljurashi area for mineral identifications and quantifications.

Geophysical-geological model of the Pedra Branca massif in the Goiás Tin Province, Brazil

The Pedra Branca massif is located in central Brazil, northeast Goiás, near the city of Nova Roma, occupying an area of approximately 80 km2. It is part of the Goiás Tin Province (GTP), located within the oldest tin subprovince, Rio Paranã, which, together with the Rio Tocantins Subprovince, are the most economically important provinces of the GTP. The massif is part of the Pedra Branca suite and is defined as an A-type granite from the Paleoproterozoic (1.6–1.77 Ga), rich in several ores such as tin, fluorine and rare-earth elements (REE) with anomalous concentration of indium, niobium, uranium, and thorium. Its magmatic evolution is closely related to the continental evolution and bimodal volcanism of the Araí rift. The mineralization zones are pre-tectonic, hosted in greisens with the presence of cassiterite; the main mineralization zones are named Zona da Bacia and Faixa Placha. This area is characterized by metallogenic importance. However, only a few geophysical studies have focused on the granite area. The lack of geophysical information makes it difficult to establish the signature of the Pedra Branca massif. The main goal of this study is to increase geophysical information by determining the magnetic and gamma-ray spectrometric signatures of the granite massif, and to generate a geophysical-geological model representative of the surface and subsurface geological features. These signatures are investigated and related to the geological structures and tin mineralized zones (cassiterite) present in the massif. Based on the analysis of airborne and ground gamma-ray spectrometry data and geochemical data, it was possible to characterize the anomalous zones of uranium (U) and thorium (Th) of the granitic massif. From the magnetometric Total Gradient Amplitude (TGA) and Tilt Derivative (TDR) products, it was possible to define important magnetic signatures, as well as to delimit the intrusion and its contact with enclosing and surrounding rocks. These products, in conjunction with products generated by Matched Filtering and Euler Solutions, provide subsurface magnetic signature information and their depth estimates. The forward modeling and the inversion of the magnetic data generated from the Induced Magnetization Vector (MVI), were correlated in order to generate a 2D geophysical-geological model that presents main sources of shallow magnetic susceptibility (ca. 800 m) corresponding to the Faixa Placha (0.029SI) and sources of high susceptibility (0.012SI - MVI), located in greater depth (ca. 2 km) inside and outside the massif. Within the massif, the source of high susceptibility was interpreted as mafic pluton due to the bimodal magmatism of the Araí rift. On the surface, this mafic magmatism emerges as diabase dikes. The other magnetic source in the southeast edge is interpreted like a mafic magmatism body from the bimodal volcanism of Araí Group or Quartz Diorite Nova Roma. The interpretation of geophysical data is consistent with the underplating process, commonly accepted as responsible for the generation of type A magmas, based on the partial melting of the continental crust, caused by the rise of mafic magma.

Structure of the Carboniferous Altenberg-Teplice Caldera (Eastern part of the Krušné hory/Erzgebirge Mts.) revealed by combined airborne and ground gamma-ray spectrometry

Structure of the Carboniferous Altenberg-Teplice Caldera (Eastern part of the Krušné hory/Erzgebirge Mts.) revealed by combined airborne and ground gamma-ray spectrometry

Processing of Landsat 8 Imagery and Ground Gamma-Ray Spectrometry for Geologic Mapping and Dose-Rate Assessment, Wadi Diit along the Red Sea Coast, Egypt

Maximum Likelihood (MLH) supervised classification of atmospherically corrected Landsat 8 imagery was applied successfully for delineating main geologic units with a good accuracy (about 90%) according to reliable ground truth areas, which reflected the ability of remote sensing data in mapping poorly-accessed and remote regions such as playa (Sabkha) environs, subdued topography and sand dunes. Ground gamma-ray spectrometric survey was to delineate radioactive anomalies within Quaternary sediments at Wadi Diit. The mean absorbed dose rate (D), annual effective dose equivalent (AEDE) and external hazard index (Hex) were found to be within the average worldwide ranges. Therefore, Wadi Diit environment is said to be radiological hazard safe except at the black-sand lens whose absorbed dose rate of 100.77 nGy/h exceeds the world average. So, the inhabitants will receive a relatively high radioactive dose generated mainly by monazite and zircon minerals from black-sand lens.

Analysis of Geological and Geophysical Datasets for Radioelement Exploration in Kab Amiri Area, Central Eastern Desert, Egypt

Detailed geological mapping description of the different granitic types of Kab Amiri pluton were integrated with geophysical (ground gamma ray spectrometry and aeromagnetic) data to identify and map the distribution of radioelement concentrations as well as delineate structural trends that control the mineralized zones in the study area. The geologic studies revealed the existence of four granite varieties namely; biotite granite, garnet two mica granite, muscovite granite, and episyenite. The structural interpretation of geological and geophysical data revealed two intersecting sets of NW and NE-trending faults. The NW-trending set of faults is younger than the NE-trending set where the latter is dissected and displaced by the former. Interpretations of radiometric data revealed the presence of radioactive anomalies southwards that indicate an original increase in uranium contents in the same direction. It could be related to the prevailing NE and ENE fault trends. The southern anomalous zone is related to a very high episyenitization and uranium mobilization. It exhibits a sharp increase in the eU concentrations reaching 370 ppm resulting in a high eU/eTh ratio, approaching 4.5 and, characterized by oval shape trending in the NE direction. Some areas along the peripheral part of Kab Amiri pluton are episyenitized and show a remobilization of uranium. These areas are mostly controlled by faults mainly trending ENE. In the case of the episyenite zone, strong mobilization of uranium is expected to host epigenetic uranium occurrences because more uranium is available. It is obvious that the episyenite rocks of high permeability have higher levels of uranium and their ratios. Thus, these rocks act as an important reservoir for U- mineralization bearing solutions.

Investigation of a relation between radiogenic heat production and kinetic surface temperature from multispectral ASTER-TIR data: a case study on Elmissikat-Eleridiya granites, Central Eastern Desert, Egypt

In this paper, an attempt was tried to study the relation between radiogenic heat production rate (RHPR) that derived from gamma-ray spectrometric data and the kinetic surface temperature KST, which was calculated from the thermal emission and reflection radiometer-thermal infrared (ASTER-TIR) imagery applied on Elmissikat-Eleridiya district. This area is considered one of the most important uranium localities in the Central Eastern Desert of Egypt. The gamma-ray spectrometric data including both airborne data and in situ measurements concurrent with the collection of 20 rock samples were used to determine the rock density. The ground gamma-ray spectrometry has been conducted using GS-256 spectrometer at the same locations of rock samples. The gamma-ray spectrometric data (airborne and ground) beside rock density data were used for calculating RHPR. Alongside, pairs of daytime and nighttime ASTER-TIR images were collected and surface kinetic temperature for both day (daytime kinetic surface temperature (DKST)) and night (nighttime kinetic surface temperature (NKST)) were derived by using reference channel emissivity technique. The study showed a relative higher RHPR within syenogranite (4.2 up to 6 μW/m3) than other rock units. Besides, the KST of syenogranite ranged from 33 to 48 °C in daytime and between 7 and 17 °C at night. Comparing all results, no clear relation between RHPR and KST is evident. This is due to the very weak RHPR that is not sufficient to affect the surface heat temperature, which can be remotely sensed by ASTER satellite TIR data. This factor in addition to other factors such as: structural elements, topography, geographic locations, shading and scattering, rock moisture and density, can strongly affect the surface temperature. In conclusion, these results could be improved in areas of very high radioelement concentrations, especially 235U and through the use of the enhanced spatial resolution of future satellite TIR imaging instruments.

Contribution of gamma ground spectrometry to the textural characterization and mapping of floodplain sediments

The possible contribution of ground gamma-ray spectrometry (GRS) to the study of topsoils was tested in the Rieti floodplain (Central Italy), an area characterized by a complex sedimentary evolution and a long lasting interference between human activities and hydrological setting.A significant inverse correlation between total γ count and sand content (R=−0.901; p<0.01), with the latter acting as a diluent for the radioisotopes concentration in the topsoils, suggested to integrate the textural data of 289 topsoil samples by using a ground gamma ray survey. An extensive survey (1906 total γ emission measurements at a density of 21.1measurements/km2) was carried out with a portable NaI(Tl) scintillometer by combining hand-held and car-borne techniques.The total γ emission compared to the spatial distribution of measured soil textures and to the relatively small altimetrical variations of the topographic surface along selected transects, allowed to have a better insight of the Holocene sedimentary evolution.The total γ counts were also used in conjunction with a series of geographic variables uniquely linked to the geographic and physiographic setting of the floodplain, such as the distance from rivers and floodplain edges, the topographic curvature and the geographic position of sampled points (X, Y, Z), to carry out a discriminant analysis that allowed to correctly assign soils to their USDA texture groups in 59.2% of the cases. The same analysis carried out on a subgroup of 101 soil samples, where some common pedological parameters were also included (pH, total organic carbon, total carbonates and field capacity), allowed to increase the discriminant score to 76.2% showing how the statistical contribution of total γ counts remains always relevant independently from the suite of variables that is chosen. The gamma survey allowed to improve the understanding of the spatial distribution of the topsoil textures which is also the basis for a more efficient management of agricultural land in the study area. Total γ emission recorded near the edge of the floodplain, in the distal sectors of some alluvial fans, resulted significantly affected by the presence of calcareous rock fragments in the topsoil and was therefore reliably used to measure their abundance.The results of this study encourage the extensive use of ground GRS in the field of applied sedimentology and topsoil mapping of floodplains as a fast and low cost technique capable to usefully integrate the traditional surveys based on the execution of laboratory analyses. In fact this survey technique can be potentially addressed to different surface sedimentary environments by using expert knowledge to interpret the recorded doses in the light of the local lithological setting.

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

AbstractA 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.

Correlação gamaespectrométrica de afloramentos e poços: estudo de caso na Formação Ponta Grossa (Bacia do Paraná, Brasil)

No contexto de modelos analogos, dados gamaespectrometricos de superficie da Formacao Ponta Grossa (FPG), Devoniano da Bacia do Parana, constituida pelos membros Jaguariaiva, Tibagi e Sao Domingos, permitiram melhor entender a distribuicao de seus litotipos e estabelecer correlacoes com os dados de radiacao gama derivados de perfis de pocos profundos. As medidas de superficie, espacadas de 50 cm nos arenitos e 100 cm nos folhelhos, foram adquiridas em quatro secoes: Arapoti, Tibagi, Jaguariaiva e Ponta Grossa, com extensoes respectivas de 30, 250, 12 e 16 metros. Os resultados mostraram que a tendencia de incremento gradativo da fracao argila na secao Arapoti (camadas de transicao das formacoes Furnas e Ponta Grossa) foi bem refletida nos perfis de raios gama em superficie e subsuperficie. No perfil Tibagi (Membro Jaguariaiva), os teores de carbono orgânico total (COT) guardaram relacao direta com o aumento da radiacao gama em superficie e em profundidade. Ainda neste perfil se constatou relacoes consistentes dos dados gamaespectrometricos de afloramentos e pocos com a secao granulometrica de 250 metros de exposicao da FPG. Na secao Jaguariaiva foi possivel notar com clareza a diminuicao das contagens nas camadas arenosas e a queda abrupta dos valores a partir do contato dos arenitos basais do Grupo Itarare. O Membro Tibagi, claramente mais arenoso, explicitou no perfil Ponta Grossa assinatura dos raios gama compativel a um padrao granocrescente ascendente, tambem verificada nos perfis de pocos. O Membro Sao Domingos, representativo de possante intervalo pelitico da FPG, foi tambem bem caracterizado atraves de altas contagens nos dois niveis de investigacao. O emprego de gamaespectrometria de superficie, em correspondencia a descricao pormenorizada de afloramentos e a dados de pocos profundos, apontou para o estabelecimento de modelos analogos da FPG na Bacia do Parana.

Analysis of petrophysical properties of some granitoids in Sweden

Variations seen in the airborne magnetic, airborne spectrometry and ground gravity data are used as a base to study some granitoids with various outcrop distributions in two areas in Sweden. The ground gamma-ray spectrometry data as well as density and magnetic susceptibility of rock samples are then used to study the details of changes in the petrophysical properties of the granitoid suites. The variation of petrophysical properties is even studied within an individual suite. We have observed that in a given suite of granitoid, various rock types, namely mafic and felsic, can be discriminated using airborne and ground geophysical data. Airborne spectrometry and ground gravity data show that a more granitic composition has a higher concentration of K, U and Th and also a lower Bouguer anomaly signature. The measured concentrations on the outcrops and the densities of the rock samples support these results very well. The lower densities of the more felsic rocks with higher K concentrations are very well correlated. The geophysical data cover large areas and thus are also cost-effective to use.

Effects of Hydrothermal Alteration on Geochemical Characteristics of the El Sukkari Granite, Central Eastern Desert, Egypt

The El Sukkari granite is predominantly peraluminous and classified as intrusive in a syn-collisional setting. Geochemical evidence suggests that this granite was generated by partial melting of metagraywackes at ˜800°C as deduced from zircon saturation temperatures. The El Sukkari granite underwent multistage hydrothermal processes accompanying gold mineralization. Intensive hydrothermal alteration of the granite occurred along brittle structures that are mostly filled by dikes and quartz veins. Sodic and potassic metasomatism are the major alteration effects. Hydrothermal alteration is indicated by depletion of both light and heavy REE and Eu-enrichment. Eu-enrichment is due largely to chemical contribution from hydrothermal fluids. Other major and trace elements were enriched or depleted during one of the main alteration stages. Rb, Zn, Nb, Zr, T, Y, and Ga show depletion. Ba and Sr display enrichments, whereas Co, Li, and Cr underwent insignificant changes. Ground gamma-ray spectrometry measurements indicate that radioactive element concentrations are generally low in the altered granite. Correlations between eU, eTh, and eU/eTh of the altered granite and the plot of chemically measured U against corresponding Th values for both fresh and altered granites reflect the geochemical coherence of uranium and thorium during magma crystallization. Both elements are mainly hosted in accessory phases and were not disturbed by the hydrothermal alteration.

Geological, geophysical and geochemical studies around the Allan Lake carbonatite, Algonquin Park, Ontario

The Allan Lake carbonatite, found in 1977 by an airborne gamma-ray spectrometric survey, is a small (about 0.4 km 2), unexposed, ankeritic-sideritic, REE-enriched carbonatite. Minor phases include biotite silico-carbonatite, orthoclase-dolomite carbonatite, apatite-rich carbonatite and narrow zones of intense chloritization. A poorly exposed fenitized aureole dominated by abundant hematitic veining and minor acmite-bearing veins grades into a brecciated border zone surrounding the carbonatite. Radial, breccia, lamprophyre and hematite-rich dykes are present within the fenitic aureole. Glacial erosion has produced a dispersal train of lithologically distinctive till which covers an area of approximately 10 km 2 and is characterized by anomalous (10–20 times background), concentrations of Ba, Nb, Th, Ce, La, Zn, Mn and Fe; and elevated (5–10 times background) concentrations of Y, P, Cu, Pb, Mo, Co and U. This dispersal train is detectable by airborne and ground gamma-ray spectrometry, till geochemistry, boulder mapping and biogeochemistry.