Radioactive Granites Research Articles

Exploratory Mapping of the Geothermal Anomalies in the Neoproterozoic Arabian Shield, Saudi Arabia, Using Magnetic Data

In this paper, certain areas of the Kingdom of Saudi Arabia (KSA) are assessed in order to map potential geothermal energy zones. To evaluate high-resolution aerial magnetic data, spectral depth analysis using a modified centroid approach was used. The calculated geothermal parameters were gridded in order to delineate the regions characterised by a shallow Curie point depth (CPD) and a high geothermal gradient (GG) as well as a high heat flow (HF). The CPD, GG and HF calculated from the analysed data varied in the ranges of 6.0–15.0 km, 40.0–100.0 °C/km and 90.0–270.0 mW/m2, respectively. The obtained results show the concurrence of the positions of shallow CPD (<8.0 km), high GG (>83.5 °C/km) and high HF (>211.0 mW/m2). The geothermal systems that are oriented in the E–W direction are related to the Red Sea tectonics, the tectonic opening of the Red Sea/Gulf of the Suez Rift, hot subterranean anomalies and high enthalpy from radioactive granites. Likewise, the geologic structures (fractures and faults) related to the Red Sea tectonics serve as channels for the movement of hydrothermal fluids and the deposition of associated minerals. All in all, another geophysical study involving deep boreholes, and seismic, magnetotelluric, electromagnetic and geochemical data should be conducted to evaluate and estimate precisely the economic reserves of geothermal resources.

Audio Magnetotelluric and Gravity Investigation of the High-Heat-Generating Granites of Midyan Terrane, Northwest Saudi Arabia

The Midyan Terrane (northwest Saudi Arabia) is characterized by the presence of a massive belt of radioactive granitic rocks and thick sedimentary cover near the coastal areas. The area is greatly influenced by the tectonic activities of the Red Sea and Gulf of Aqaba, implying its high potentiality of geothermal energy. In the present work, geophysical surveys, including audio magnetotelluric and gravity methods, were integrated to investigate the subsurface structural pattern of the study area, which identified regional deep and shallow fault systems and detected the subsurface geometry/extension of the granitic rocks as well as detecting the thickness of the sedimentary basins near the coastal area. A total number of 80 audio magnetotelluric and 246 gravity stations were recorded, analyzed, and interpreted. Two high-potential geothermal targets were indicated: high-heat-generating granites and thick anomalous sedimentary basins near the coastal areas. High-heat-generating granites are significant in terms of enhanced geothermal systems (EGSs) whereas sedimentary basins play a crucial role in the formation of conventional geothermal systems. Both areas require more exploration plans to evaluate the energy potential of geothermal reservoirs. The results also contribute to the identification of the subsurface orientation and geometry of radioactive granites, providing the necessary parameters to enhance a volumetric estimation for geothermal reserves.

Study of Radioactivity in Bajaur Norite Exposed in the Himalayan Tectonic Zone of Northern Pakistan

Radioactivity in Granites of Pakistan systematically increases from south to north. The Ambella Granite found at the northern edge of Pakistan is highly radioactive. Radioactivity measurements made on, so called, Bajaur Granite, located in northern Pakistan, have been found to be lowest among all the granitic rock of the area. In order to find out the exact nature of Bajaur rocks, mineralogical studies were carried on rock chips and powdered samples. The Bajaur Norite contains plagioclase feldspar more than 45% as the chief constituent. Orthopyroxene and clinopyroxene are 27% and 18%. Quartz, biotite, and some opaque minerals are also found in accessory amounts. Bajaur Granite is in fact not a granite but Norite, which is rich in Na-Ca plagioclase series of feldspars. The plagioclase feldspar rich in Na-Ca are low in radioactivity. Moreover, the average gamma activities of 226Ra, 232Th, and 40K (4.98 ± 0.13 Bqkg −1, 4.03 ± 0.31 Bqkg −1, 204.40 ± 4.72 Bqkg −1 and a total of all three radionuclides are 214.00 ± 5.39 Bqkg −1) for Bajaur Norites are found too be much less than the average of the world’s Granites. Indoor and outdoor hazard indices of Bajaur Norite are much below building materials used throughout the world and largely beneath their criterion restrictions. As per radiations’ hazards are concerned, the Bajaur Norite as a building stone may be considered as the safest material available in the area that does not pose any radiological hazard.

A geochemical comparison between volcanic and non-volcanic hot springs from East Malaysia: Implications for their origin and geothermometry

• Non-volcanic hot springs are K-Na-bicarbonate rich waters with low SO 4 contents. • Volcanic hot springs are neutral chloride waters with high SO 4 contents. • Radioactivity of granites is the main heat source for non-volcanic hot springs. • Volcanic activity is the main heat source for volcanic hot springs. • Hot springs show intermediate to high enthalpy with potential energy generation. Sources of volcanic and non-volcanic thermal sources have been studied in East Malaysia to differentiate their geothermal reservoir temperatures and first-ever reports on its geochemical processes that affect the evolution of the constituents of thermal groundwater subsurface circulation. The study of geothermal potentials includes indices of geochemistry, geothermometry, and mineral saturation. The surface temperatures of thermal springs range from 27 to 56 °C, and the pH values range from 5.6 to 9.0. The geochemical characteristic distinguishes non-volcanic thermal sources as K-Na-HCO 3 , while volcanic thermal sources present the Cl-HCO 3 -SO 4 -Na type. The quartz geothermometer showed that the reservoir temperatures of non-volcanic hot springs range between 61 and 135 °C. In comparison, the volcanic thermal sources range from 55 to 185 °C requiring 257 to 565 kJ/kg and energy from 231 to 786 respectively to heat water. Subsequently, it is defined as intermediate to slightly high enthalpy for most thermal springs, especially volcanic springs. The mixing of hot water with sources close to the surface can be seen by the disagreement between the silica and cation geothermometers and the disequilibrium with their associated host rocks as indicated from the plot of studied hot springs in the Na-K-Mg ternary diagram and saturation indices calculations. Radiogenic granitic host rock represents the main heat source for non-volcanic hot springs govern by meteoric water generated in deep-seated fault systems. Meanwhile, in volcanic areas with high secondary permeability caused by faults, fractures and fractures, meteorological waters can descend to a considerable depth and heat up. In a favourable situation, thermal waters return to the surface by faults and fracture zones.

Practical analysis of aflatoxin M1 reduction in pasteurized Milk using low dose gamma irradiation.

Milk and dairy products can be exposed to potential dangers such as aflatoxin M1 (AFM1). Various factors affect the formation of aflatoxin, which can be due to environmental changes and the lack of suitable substrate for healthy livestock feeding. The goal of this study is to reduce the toxin in pasteurized milk to a level below the European Codex Alimentarius Commission standard. For this purpose, the proper structure of the radioactive granite stone was first designed as a low level gamma irradiation (LLGI) without contact with pasteurized milk, and and the pasteurized milk containing AFM1 that placed in this structure is measured and compared with the control sample values using Association of Official Analytical Chemists (AOAC) method. Then, the reduction of the resulting aflatoxin in the milk and the LLGI dose rate are obtained. The LLGI dose rate is calculated using the Monte Carlo N-Particle Transport Code (MCNP). For simulation, in addition to the spectrum of gamma radiation emitted by radioactive granites, weight percent of each composition of the pasteurized milk and its component elements are also calculated. The results showed a 51.5% reduction of aflatoxin in pasteurized milk after 4days and 99% reduction after 8days compared to the control sample. The LLGI dose rate in milk is 0.39mGy per day. According to the international atomic energy agency (IAEA) report and pervious results, this dose rate level does not significantly affect chemical and sensory quality of milk, but can extend the shelf-life and provide a safer milk. Therefore, the structure constructed using radioactive granite in this study can be considered as one of the suitable methods for reducing aflatoxin.

Assessment of radiation risk and radon exhalation rate for granite used in the construction industry

The results of the gamma spectrometry analysis of the 40 samples of highly radioactive granites used in the construction industry in Serbia are presented. Based on the measured activity concentrations of 226Ra, 232Th and 40K, radiological hazard indices, annual effective doses, as well as indoor radon concentration were determined. Calculated indoor radon concentration caused by investigated granite samples in 25% of cases exceeds the upper limit of 300 Bq m−3 recommended by the World Health Organization.

Zirconolite, Baddeleyite, Zircon, and Thorite of Island-Arc Quartz Gabbronorite-Dolerites of the Ayu-Dag Intrusive, Crimean Mountains

The Early Bajocian island-arc quartz gabbronorite-dolerites of the Ayu-Dag intrusive contain syngenetic zirconolite and baddeleyite. Zirconolite includes Ca-dominant and atypical Y-dominant (Y, Ca, Th, REE)2FeZr2Ti3O14 varieties. Two genetic types of zircon and thorite occur. The dominant xenogenic zircon-I with thorite inclusions and numerous melting traces (lacunes) is enriched in Hf, Th, Y, and P (up to 6 wt % HfO2, 5 wt % ThO2, 6 wt % Y2O3, 3 wt % P2O5). Thorite contains 7–9 wt % UO2. Zircon-I and thorite-I of similar compositions are typical minerals of highly radioactive granites. The isotope age of xenogenic zircon is more than 2 Ga. Rare syngenetic zircon-II is extremely depleted in Th, U, Y, and Hf. Thus, the Ayu-Dag basic magma was contaminated by Early Precambrian highly radioactive granites, whose bodies probably occur in the basement of Crimean Mountains.

Zirconolite, baddeleite, zircon and thorite of island arc quartz gabbro-norite-dolerites of Ayu-Dag intrusion (Mountain Crimea)

Early Bajocian island arc quartz gabbro-norite-dolerites of Ayu-Dag contain syngenetic zirconolite and baddeleite. Zirconolite presents as Ca-dominant and uncommon Y-dominant (Y, Ca, Th, REE)2FeZr2Ti3O14. Two genetic types of zircon and thorite are developed. Predominant xenogenic zircon-I with thorite inclusions and a mass of lacunes — traces of reflow, is enriched with Hf, Th, Y, P (up to 6 wt.% HfO2, 5% ThO2, 6% Y2O3, 3% Р2О5). Thorite contains 7–9% UO2. Zircon and thorite of such composition are typical minerals of highly radioactive granites. Isotope age of zircon (xenogenic) is >2 billion years. Rare syngenetic zircon-II is sharply poor of Th, U, Y and Hf. So, basic magma of Ayu-Dag was contaminated with substance of Early Precambrian highly radioactive granites, which bodies are probabely located in the Mountain Crimea substructure.

Natural radioactivity in granites and gneisses of the Opava Mountains (Poland): a comparison between laboratory and in situ measurements

The natural radioactivities of five characteristic igneous rocks of the eastern foreland of the Opava Mountains (Eastern Sudetes, Poland), obtained in the laboratory and under in situ conditions, are presented. The activity concentrations of 232Th, 238U, and 40K were measured using an HPGe gamma-ray spectrometry system. The ranges of the activity concentrations of 232Th were 7–71 Bq kg−1 in the laboratory and 6–68 Bq kg−1 for the in situ measurements. For 238U, the ranges of the activity concentrations were 5–52 Bq kg−1 in the laboratory and 9–48 Bq kg−1 for the in situ measurements, and for 40K, the ranges were 520–1560 Bq kg−1 in the laboratory and 537–1700 Bq kg−1 for the in situ measurements. These determined activity concentrations were compared with the average activity concentrations of the radionuclides in similar types of rocks and with data from the Sudetes available in the literature. No significant differences were found between the in situ and laboratory measurements.

The formation of a geothermal anomaly and extensional structures in Guangdong, China: Evidence from gravity analyses

Southeast Asia contains significant natural geothermal resources. The structure of the geothermal anomalies, which have been affected by extension, are characterized by northeast trending normal faults surrounded by Mesozoic magmatic intrusions. In order to study the relationship between tectonic movements and geothermal resources, Bouguer gravity data of Guangdong province is inverted to determine the crustal structure. Density sources from different depths are separated with multi-scale wavelet decomposition. Concealed granites are inferred from low gravity anomalies and these high radioactive granites correlate with the location of natural thermal springs. The locations of basins are delineated by high gravity anomalies. The granites and rift basins, which formed during the Mesozoic in an extensional regime associated with thermal and magmatic activity, resulted in the current geophysical and geothermal anomaly.

High Heat Producing Radioactive Granites of Malani Igneous Suite at Northeast of Jodhpur, Northwestern India

ABSTRACT The Malani igneous suite, a terrain showing crustal formation as late as in Neoproterozoic, shows some pink and grey granites in the northeast of the desert city of Jodhpur, in northwestern, India. The average heat generation value of 15.925 HGU for these granites that is much higher than the average known value (3.8 HGU) for the continental crust has been reported here. The concentration of uranium determined is four times higher than the average continental crust. Thorium is still higher than U and K. The radioelement concentration (Ur) varies from 15.58 to 73.48 in the granites with an average of 45.671, clearly indicates a ‘hot crust’. Hence it is favourable for the formation of mineralization of HFS elements like, Nb, Ce, REE and U and Th, which need to be explored in the terrain as an economic deposit.

Natural Radioactivity in Granites Used as Countertops in the New Buildings of King Abdulaziz University

Natural Radioactivity in Granites Used as Countertops in the New Buildings of King Abdulaziz University

Measurement of natural radioactivity in granites and its quartz-bearing gold at El-Fawakhir area (Central Eastern Desert), Egypt

The distribution of natural radionuclides (226Ra, 232Th and 40K) in Granites and its quartz-bearing gold at El-Fawakhir area (Central Eastern Desert, Egypt) were measured by using γ-ray spectroscopy [NaI (Tl) 3″ × 3″]. X-Ray Fluorescence technique was used for chemical analyses of the studied samples. The specific activity of 226Ra, 232Th and 40K values are in range (3 ± 0.5 to 43 ± 2 Bqkg−1), (5 ± 0.7 to 41 ± 2 Bqkg−1) and (128 ± 6 to 682 ± 35 Bqkg−1) respectively. The absorbed dose rates ranged from 13.8 to 58.4 nGy h−1, where the total effective dose rates were determined to be between 16.7 and 70.9 μSvy−1. The maximum external hazard index (Hex) is 0.3 nGyh−1. The calculated values of the excess lifetime cancer risks (ELCR) and annual effective dose rate values are in between (8.48 × 10−5 and 2.63 × 10−4) and (24.2 and 72.9 μSvy−1) respectively. Geochemically, the studied granites consist of major oxides, they are characterized by SiO2, K2O, Na2O, Al2O3, and depleted in CaO, MgO, TiO2, and P2O5. The average absorbed dose rate (Do) in air is 37.8 nGyh−1 for the whole studied samples, this value is about 3.78% of the 1.0 mSvy−1 recommended by (ICRP-60,1991) to the public, so there is no radiological risk for the workers in that area.

Seismic mapping and geomechanical analyses of faults within deep hot granites, a workflow for enhanced geothermal system projects

Areas with deep seated radioactive granites are considered targets for enhanced geothermal system (EGS) projects. These areas normally exhibit high heat flow and temperature anomalies related to granitic bodies. High concentrations of uranium within the granites are the most likely cause of the anomalous temperatures. Elevated temperatures are also resulted to high heat flow and thick sedimentary rock cover that includes insulating materials such as coals and gas reservoirs.In this study we investigated the use of 3D seismic amplitudes and attributes to map deep granitic bodies and faults in the Cooper Basin of South Central Australia. We established a workflow for possible geomechanical fluid flow susceptibility analyses for faults that intersect granites. The far field stress tensor must be interpreted through analyses of image logs and formation tests. Our geomechanical analyses models show how this stress tensor affects basement faults interpreted from 3D seismic surveys. Normal stresses, shear stresses, slip tendency, and distance to failure should be modelled for the faults that cut the granites. The optimal orientation of faults that can be possible conduits are then located. We suggest that the optimal injection and production wells should be located at tips of shallow faults that penetrate the granites. We anticipate that short horizontal faults that are located far from other faults will form a more secure fluid conduit. Finally, this study can be a workflow to evaluate the relative merit of future enhanced geothermal system projects.

Petrochemical and Mineralogical Constraints on the Source and Processes of Uranium Mineralisation in the Granitoids of Zing-Monkin Area, Adamawa Massif, NE Nigeria

Zing-Monkin area, located in the northern part of Adamawa Massif, is underlain by extensive exposures of moderately radioactive granodiorites, anatectic migmatites, equigranular granites, porphyritic granites and highly radioactive fine-grained granites with minor pegmatites. Selected major and trace element petrochemical investigations of the rocks show that a progression from granodiorite through migmatite to granites is characterised by depletion of MgO, CaO, Fe2O3, Sr, Ba, and Zr, and enrichment of SiO2 and Rb. This trend is associated with uranium enrichment and shows a chemical gradation from the more primitive granodiorite to the more evolved granites. Electron microprobe analysis shows that the uranium is content in uranothorite and in accessories, such as monazite, titanite, apatite, epidote and zircon. Based on petrochemical and mineralogical data, the more differentiated granitoids (e.g., fine-grained granite) bordering the Benue Trough are the immediate source of the uranium prospect in Bima Sandstone within the Trough. Uranium was derived from the granitoids by weathering and erosion. Transportation and subsequent interaction with organic matter within the Bima Sandstone led to precipitation of insoluble secondary uranium minerals in the Benue Trough.

Hot rocks in Australia - National overview

Hot Rocks have potential to fuel competitive, emission free and renewable electricity for centuries to come. This potential is stimulating Enhanced (Engineered) Geothermal Systems projects worldwide, calling upon integrated expertise from the petroleum, minerals and power industries. Converting just 1% of Australia?s estimated Hot Rock crustal energy to electricity, from temperatures above 150°C and depths below 5 km (190 million PJ) would supply 26,000 years of Australia?s primary power use, and that neither takes into account the renewable characteristics of hot rocks, nor resources below 5,000m. Factors that distinguish Australian Hot Rock resources are: (1) Very radioactive granites are abundant, as in South Australia where the mean heat flow is 92 µWm-2 compared to a global continental average of 51µWm-2 ; and (2) Australia is converging with Indonesia on a plate scale - giving rise to common, naturally occurring sub-horizontally fractured basement rocks that are susceptible to hydraulic fracture stimulation. Australia?s geothermal projects are focused on both Hot Rocks to develop Enhanced (Engineered) Geothermal Systems and associated Hot Sedimentary Aquifer plays to fuel binary power plants. In addition to meeting demand for base load power, mining, desalinisation and drying processes are also markets for geothermal energy.In the term January 2000 through December 2008, companies have applied for 385 licence areas (covering 359,723 km2) to progress proof-of-concept amagmatic Hot Rock and Hot Sedimentary Aquifer projects in Australia. In the term 2002 through 2008, more than Aus$325 million (US$228 million) has been spent on studies, geophysical surveys, drilling, reservoir stimulation and flow tests that comprise the work programs required to sustain tenure in geothermal licences areas. In the term 2002-2013, investment for Australian proof-of-concept geothermal projects is expected to exceed Aus$1,523 million (US$1,066 million). This rapidly rising level of investment is driving sector-wide cooperation to support high priority and complementary research that can speed the pace and lower the cost of commercialising Australia?s vast Hot Rock (HR) and Hot Sedimentary Aquifer (HSA) geothermal plays. That cooperation is underpinned with more than Aus$110 million (US$77 million) in Australian Federal and State government grants to meet up to half of the cost of the private sector?s field efforts. This includes Aus$60 million (US$42 million) available to support new deep drilling for the proof-of-concept HR and HSA projects, but excludes Aus$507 million (US$355 million) for all forms of meritorious, commercial-scale demonstration of renewable energy technologies, including geothermal projects. This paper summarises: (1) proof-of-concept amagmatic HR and HSA geothermal projects co-funded by investors and governments in Australia; (2) policies, programs and alliances put in place to support the development of geothermal plays; (3) research priorities and studies undertaken in support of geothermal projects and (4) emerging protocols to build trust with stakeholders, including a reporting code for geothermal resource and reserve estimates and best practice procedures for the management of potential risks associated with induced seismicity.

Study of radioactivity levels in granite of Gable Gattar II in the north eastern desert of Egypt

The present work deals with the radioactivity of granites in Gable Gattar II, which is located in the north eastern desert of Egypt. Fifty samples from the area of Gable Gattar II were investigated. The radionuclides of the samples, in Bq/kg, have been measured using a hyper-pure germanium spectrometer. The dose obtained for 238U and 232Th ranged from 165±5 to 27851±836 and 71±2 to 274±8 Bq/kg, respectively. The dose of 40K only changes slightly. To assess the radiological hazard of the natural radioactivity in the samples, the radium equivalent activity, the absorbed dose rate and the external hazard index were calculated. This study provides a baseline map of radioactivity background levels in the Egyptian environment and will be used as reference information to assess any changes in the radioactive background level due to geological processes. The Gable Gattar granite, from uranium mineralization, has high economic potential.

The mineralogy and geochemistry of uranium, thorium, and rare-earth elements in two radioactive granites of the Vosges, France

AbstractTwo contrasting types of Hercynian U-rich granites can be distinguished by their accessory minerals: (1) subalkaline potassic granites (amphibole-biotite±pyroxene) characterized by apatite-zircon-thorite-sphene-allanite and rare ThO2-rich uraninite, in order of appearance in the magma, and (2) leucocratic granites (biotite and muscovite) which contain monazite-zircon-apatite-xenotime-ThO2-poor uraninite and Ti oxides. Intermediate accessory mineral associations may also exist.The mineralogy, crystallization history, and geochemistry of two high K-U-Th granites from the Vosges, France, is described. Their assemblage of U- and Th-bearing accessory minerals is listed, in order of appearance in the magma, in Group 1 (above). Trace elements (U, Th, Zr, Hf) and preliminary data on REE are discussed. In a layered sequence of the Crêtes granite, thorite, with up to 15% UO2, is shown to be important during differentiation. There is a decrease of the Th/U ratio corresponding to a slight decrease of the Th content whereas there is an increase of the U content at the end of differentiation. The Crêtes and Ballons granites have REE patterns characterized by LREE enrichment with a La/Yb ratio of about 28 (Crêtes granite) and a slight negative Eu anomaly. These relationships are typical of subalkaline potassic granites of the Hercynian. The trace element associations are similar to those of the shoshonite association with high U, Th, LREE and Ba, Rb, and Sr contents. A hypothetical model for uranium mineralization associated with such granites is discussed in the light of these data.

Uranium and thorium in rocks of the Soviet Northeast

Radioactivity of noncontemporaneous magmatic, metamorphic, and ore formations was determined over a wide area of the Soviet Northeast from 1500 analyses of uranium and 800 analyses of thorium (x-ray spectral and luminescence analyses). Leucocratic and alaskitic potassium granites of the culminating phases of late Mesozoic granitoid assemblages have heightened radioactivity and these granites are close to highly radioactive granites of the trace-metal type as defined by L.V. Komlev and A.A. Smyslov. Detailed characteristics of the salient petrologic and petrologic-chemical features of granitoid assemblages differing in the nature of radioactivity are given, as are data on uranium and thorium concentrations in the principal rock-forming minerals.

Distribution of radioactivity in the rocks of South India

The study on the distribution of radioactivity in granites and associated rocks, with relevant geological and chemical data confirm that: The study on the distribution of radioactivity in rocks will be of great use in suggesting the petrogenetic history of the rocks.