Radioactive Heat Production Research Articles

Risk assessment due to natural radioactivity of stone dust and crushed stone Commercialized in construction stores in the state of Rio de Janeiro

A systematic study of the distribution of the Naturally Occurring Radioactivity in stone dust and crushed stone, has been carried out with an objective of establishing reliable baseline data on the radiation level and hence to evaluate hazard indices approach and the production of radioactive heat (RHP) due to radiation exposure to the workers and to the inhabitants of the studied area. Twenty-six samples have been collected from different locations in the State of Rio de Janeiro (Brazil). To calculate the specific activity, gamma ray spectrometry and a detector of High Purity Germanium (HPGe; Canberra, 30% relative efficiency) was used. The activity concentration of 238U, 226Ra 232Th and 40K ranged from 29.3 ± 18.6 to 206.8 ± 21.5 Bq kg−1, 30.3 ± 1.0 to 134.3 ± 1.8, 27.9 ± 0.7 to 86.2 ± 0.9 Bq kg−1, and 734.9 ± 35.1 to 1204.8 ± 53.5 Bq kg−1, respectively. The mean values of the Iex, Iin, Iγ, Iα, AUI, IRP112Rn, IPA, IPI and IYu indices were 0.68 ± 0.09, 0.92 ± 0.12, 0.93 ± 0.12, 0.43 ± 0.07, 0.88 ± 0.20, 1.25 ± 0.21, 0.34 ± 0.05, 0.75 ± 0.10, 0.63 ± 0.08 and 34. ± 6.31, respectively. The average radioactive heat production (RHP) of 2.01 ± 0.28 μ Wm−3 was above the values found in the literature, which may contribute to the heat flow in the study area because the raw materials that make up the samples showed a high value of environmental radioactivity. The Brazilian Hazard Index to assess the radiological risk of crushed stone and stone dust was created and the average value was 0.74 ± 0.10, a value below 1, which means only moderate control over the use of these materials, with no indication of restriction to the its use.

Thermophysical properties and geochemical characteristics of granites in the Tengchong area: indications for resource potential of hot dry rocks

Ascertaining regional radiogeochemical characteristics and lithospheric thermal structure characteristics is paramount for identifying the resource potential of hot dry rocks. This study conducted thermal conductivity testing and whole-rock analyses of outcrop granites of different formation epochs from the Tengchong area. Moreover, combined with the previously published whole-rock data and the data related to radioactive heat production rates, this study conducted geological, geophysical and geothermal analyses. Key findings are: (1) Granites in the Tengchong area exhibit an average radioactive heat generation rate of 5.54 μ W m −3 . Among them, the Late Cretaceous granites have an average radioactive heat generation rate of 8.08 μ W m −3 , suggesting high heat production granites. (2) Granites in the Tengchong area present an average thermal conductivity of 3.135 W.m −1 K −1 , relatively akin to the average values of granitic rocks worldwide. Compared to granites of other epochs, the Late Cretaceous granites manifest significantly higher thermal conductivities, with an average of 3.28 W.m −1 K −1 . (3) There is a negative correlation between the mica content and the thermal conductivity of the granites in the Tengchong area. (4) The Tengchong area holds potential for hot dry rocks exploitation and is inferred to have a lithospheric structure characterized by hot mantle and cold crust.

A Multi-Method Approach to Geophysical Imaging of a Composite Pluton in North Portugal

Potassium (K), thorium (Th), and uranium (U) are good markers of magmatic or alteration processes and the surface concentrations of these radioelements can be mapped at the regional or local scale through radiometric (gamma) surveys. In this study, a radiometric survey was performed in a post-orogenic pluton located in North Portugal, namely the Lamas de Olo Pluton, composed by three granitic facies. This pluton has already been intensively studied, including magnetic susceptibility, gravimetric, geochemical, and petrographic studies. The main objective of this work is to evaluate the radiometric data and combine them with other characteristics, such as magnetic susceptibility, and gravimetry, as well as to elucidate structures such as faults and fractures, outline geological boundaries, and identify alteration zones within various granites of the pluton. The radiometric approach reveals the spatial distribution of radioelements, offering a more distinct portrayal of the geology in the studied area. The radioactive heat production rate was calculated for the studied pluton, showing that the mean value is 4.09 µW m−3, surpassing the known mean values for granites. Our study highlights that radiometric measurements unveil compositional variations within granitic pluton and aid in identifying feeder zones. Furthermore, these measurements can be correlated with each type of granites, demonstrating associations with surface concentrations of K-Th-U. Our findings indicate a spatial alignment between the NE feeder root and a U-rich granite (Barragem granite), as evidenced by its elevated concentration of this radioelement. Conversely, the other root displays a notable relative concentration of Th, consistent with the Th-rich characteristics observed of the two other granites (Lamas de Olo and Alto dos Cabeços granites).

3D gravity and magnetic inversion reveal geothermal structure dominated by radioactive heat production of granites in the Weihe basin

The Weihe basin possesses abundant in medium-low temperature geothermal resources. However, the primary source of heat in the basin, whether it stems from the mantle or crust, remains a subject of debate. In this study, we employ three-dimensional inversion of gravity and magnetic anomalies to ascertain the basement depth, Moho depth, Curie point depth, and spatial distribution of magnetic bodies within the Weihe basin. Our findings reveal that there is no correlation between heat flow and mantle uplift and the uplift area of the Moho does not coincide with the depocenter of the basin. These results suggest that the mantle heat brought by lithosphere thinning and stretching is not the predominant heat source in the Weihe basin. Furthermore, we observe a significant discrepancy in Curie point depth between the northern and southern sides of the Weihe fault within this region, indicating its role as a suture zone connecting two structural units throughout geological history. Through three-dimensional susceptibility inversion analysis, we identify a widespread distribution of magnetic bodies (primarily Yanshanian granites) beneath sediments within the Weihe basin which are connected to the granites located in the North Qinling area. This suggests that the granites formation within the Weihe basin may have occurred concurrently with the magmatic activity in the North Qinling area. Since Cenozoic timescale, northeastward compression exerted by the Tibet Plateau has resulted in passive strong fault depression within the Weihe basin while burying the previously intruded granites under thick sedimentary layers on a massive scale. These buried granites release heat through radioactive decay processes making them an essential heat source for the medium-low temperature geothermal fields.

The role of continental lithospheric thermal structure in the evolution of orogenic systems: application to the Himalayan–Tibetan collision zone

Abstract. Continental collision is a crucial process in plate tectonics. However, in terms of the evolution and the controlling parameters of its lateral heterogeneity, our understanding of the tectonic complexities at such a convergent plate boundary remains largely unclear. In this study, we conducted a series of two-dimensional numerical experiments to investigate how continental lithospheric thermal structure influences the development of lateral heterogeneity along the continental collision zone. The following two end-members were achieved. First, continuous subduction mode, which prevails when the model has a cold procontinental Moho temperature (≤450 ∘C). In this case, a narrow collision orogen develops, and the subducting angle steepens with the increasing retrocontinental Moho temperature. Second, continental subduction with a slab break-off, which generates a relative wide collision orogen and dominates when the model has a relatively hot procontinental Moho temperature (≥500 ∘C), especially when the Moho temperature ≥ 550 ∘C. Radioactive heat production is the second-order controlling parameter in varying the continental collision mode, while it prefers to enhance strain localization in the upper part of the continental lithosphere and promote the growth of shear zones there. By comparing the model results with geological observations, we suggest that the discrepant evolutionary paths from the continuous subduction underlying the Hindu Kush to the continental subduction after slab break-off beneath eastern Tibet may originate from the inherited lateral inhomogeneity of the Indian lithospheric thermal structure. Besides, the high content of crustal radioactive elements may be one of the most important factors that controls the formation of large thrust fault zones in the Himalayas.

Radioactive heat production variations in the Faroe–Shetland Basin: key new heat production, geological and geochronological data for regional and local basin modelling

This study presents the results of a joint Chemostrat–APT study that aimed to produce a suite of radioactive heat production data for basement rocks in the Faroe Shetland Basin to enable more accurate basin modelling to be undertaken. To enable regional studies to be undertaken, the basement has been split into four zones based on similarities. Zone A is formed of high grade metamorphic basement from the Rockall trough (quads 154 & 164) SW of the Laxfordian front. Zone B comprises granodioritic, tonalitic and dioritic Neoarchean aged (2700–2830 Ma) high grade metamorphic basement from the SW of the Rona Ridge and Basin (wells 202/08-1, 204/15-2, 205/161, 205/21-1A, 206/7a-2, 206/08-2, 206/09-2 and 206/12-1) and NE of the Laxfordian front. Zone C contains Neoarchean aged high grade metamorphic basement of a predominantly granitic and quartz rich granitoid composition from the NE of the Rona Ridge (wells 207/01-3, 207/02-1, 208/23-1 and 208/26-1). Zone D differs from the rest of the material in this study in that it is Caledonian ( c. 460 Ma) granitic plutonic basement from Quads 209 (Ereland volcanic centre). Radioactive heat production values were derived from potassium, thorium and uranium data produced from the analysis of eighty-four basement samples by ICP-OES and ICP-MS analysis. Each mapped basement zone was then assigned a mean radioactive heat production value for use in future basin modelling studies; Zone A = 0.21 µWm 3 , Zone B, 0.64 µWm 3 , zone C = 0.88 µWm 3 and zone D = 2.1 µWm 3 . Supplementary material: Tables containing full mineralogical (SI 1) and U-Pb geochronological analytical (SI 2) data at https://doi.org/10.6084/m9.figshare.c.6771540 Thematic collection: This article is part of the New learning from exploration and development in the UKCS Atlantic Margin collection available at: https://www.lyellcollection.org/topic/collections/new-learning-from-exploration-and-development-in-the-ukcs-atlantic-margin

Terrestrial heat flow measurement and numerical simulation of lithospheric thermal structure in western Sichuan, China

The western Sichuan in the eastern Qinghai-Tibet plateau has significant geothermal potential. Heat flow is one of the most important parameters in geothermic, its measurement can help obtain a better understanding of the regional lithospheric thermal structure. In this study, we reported 4 heat flow data based on the continuous steady-state temperature logging and rock thermal conductivity test, including two class-A and two class-D data. Furthermore, we calculated the lithospheric thermal structure by a 2D steady-state thermal conduction equation in COMSOL, analyzing the lateral differences of lithospheric thermal structure in the eastern Qinghai-Tibet plateau. Our study has determined that the heat flow values in the western Sichuan range from 94.7 to 116.2 mW/m2, with a corresponding geothermal gradient of 32.1–37.3 °C/km. Moreover, numerical simulation results indicate significant differences in lithospheric thermal structure between western Sichuan and Sichuan Basin, where the Longmen Shan fault zone is a crucial regional tectonic boundary and a significant temperature gradient zone. Specifically, the Moho temperature in the western Sichuan region ranges from 1000 to 1200 °C with an average temperature of 1060 °C, while the Sichuan Basin ranges from 600 to 700 °C. Besides, the thermal lithosphere thickness in the western Sichuan and the Sichuan Basin is 88–97 km and 105–110 km, respectively. These observations suggest that the western Sichuan region is characterized by high thermal anomaly and provide theoretical evidence for the geodynamic and geothermal development in this area. Finally, we suggest that the high thermal anomaly in western Sichuan is the result of a combination of factors, such as thickened crust, high radioactive heat production, and shear frictional heating from deep fault and so on.

Estimating the Radioactive Heat Production of a Granitic Rock in the University of A Coruña (Galicia, Northwest Spain) by Gamma-ray Spectrometry

Geothermal energy is a form of renewable energy with a long tradition in European countries, although it is scarcely used in Spain. One of the reasons for this is the poorly studied geothermal potential of the Spanish territory. In recent years, data published on terrestrial gamma radiation and the geochemistry of radioisotopes in rocks have suggested that the radiogenic heat production (RHP) in some areas of Spain is high. In this work, we assessed the RHP by analysing the U, Th, and K contents of the rocks underlying the most important campus of the University of A Coruña (northwest Spain), using in situ handheld gamma-ray spectrometry (GRS) and X-ray fluorescence spectrometry (XRF). Our results provide a good fit of the radioisotope contents and unexpectedly high RHP, compared with average data observed in similar rocks (granodiorite). These results reveal that GRS is a very reliable tool for studying the RHP of rock surfaces, and that geothermal energy can be used in the area (i.e., the studied campus, but also most of the city of A Coruña, as it is built on the same underlying rock) for central heating in buildings using ground-source heat pumps (GSHPs).

The formation mechanism of the typical hot dry rocks in Hunan Province, China

Abstract Calculated by using the pipeline model, the burial depths of the 150 and 180°C hot dry rocks (HDRs) are 3.20–3.56 and 3.92–4.36 km in the Reshuiwei geothermal field, respectively, while those in the Huitang geothermal field are 3.13–3.50 and 3.84–4.28 km, respectively. Based on the analysis of the geophysical and terrestrial heat flow data, rock thermal generation rates, and the hydrochemical thermometric scale data, we summarized the formation mechanisms of the HDRs in Hunan Province: (i) the boundary deep faults in the welding area have made the intersection part of the deep faults an open tectonic environment, which is beneficial to the upwelling of deep-mantle-sourced thermal matter. (ii) The southeastern Hunan Province is the front region of the West Pacific subduction and retreat. Lithospheric thinning in this area is significant since the Mesozoic era, especially in the Dongting Lake basin, which was formed during extension and depression. This kind of regional lithospheric thinning is favorable for the lateral and upward migration and the intrusion of the deep-mantle-sourced hot substances. (iii) Rocks with high radioactive heat production rates are important crustal thermal sources for the formation of HDRs. Besides that, plutons with similar geological conditions are favorable for the formation of HDR resources. These plutons include the Baimashan pluton and its surrounding areas, and the eastern Dongting Lake plain. Moreover, the intermediate and acid granites distributed in the Chenzhou-Linwu deep fault are also part of the plutons, and the area where the Chenzhou-Linwu deep fault convergent with the Changde-Anren deep fault.

Evidence for a very thick Kaapvaal craton root: Implications for equilibrium fossil geotherms in the early continental lithosphere

The presence of diamonds of Archaean age within the cratonic lithosphere is surprising because their formation implies a cool early mantle lithosphere despite the early Earth's hotter state. There remains a widely (albeit not exclusively) held concept that the prevailing geothermal gradient within Archaean cratons was not much different from today. This ‘Archaean paradox’ is supported by pressure and/or temperature (PT) estimates of potentially ancient diamond inclusion (DI) falling close to modern cratonic geotherms. Solutions to the paradox include more effective Archaean heat loss mechanisms (e.g. heat pipes), deeper lithospheric mantle roots or the early lithosphere forming in a disequilibrium state.Here we demonstrate the effects of a thermally evolving Earth on equilibrium geotherms within the Kaapvaal craton of South Africa. We modelled geotherms from the present-day conditions backward in time to 3.0 Ga at thermal equilibrium in the lithosphere by adjusting three dominant variables: (i) time-corrected crustal heat production; (ii) a secularly cooling mantle potential temperature (Tp) in the underlying convecting mantle; and, for illustrative purposes, (iii) variable depth of the lithosphere-asthenosphere boundary (LAB) or variable heat flow at the LAB. Computed model geotherms were compared to DI PT data from the Kaapvaal craton, as well as PT conditions recorded in mantle xenoliths of variable age. It is demonstrated that equilibrium geotherms in the lithosphere cannot be reconciled with PT conditions recorded in Kaapvaal craton DI nor with those recorded in Proterozoic xenoliths if either the lithosphere has remained of constant thickness or held a constant basal heat flux since 3.0 Ga. Rather, provided that PT conditions recorded by DI from the Kaapvaal craton reflect equilibration along fossil ancient equilibrium geotherms, it is required that the early lithosphere was substantially thicker than what is preserved today. The inferred former thickness of Kaapvaal craton could have reached up to ∼350 km if the prevailing mantle Tp at the time of diamond encapsulation was high and they are of Archaean age. If, however, the Archaean asthenosphere Tp was more modest or if the diamonds formed later than the Archaean the inferred LAB depths are shallower (∼250-275 km), but still substantially deeper than at the present day.Although only the Kaapvaal craton has the necessary DI PT constraints for this exercise, the fundamental nature of radioactive heat production rate and mantle cooling mean that our findings could imply that Earth's continental lithosphere in general attained its maximal vertical extent early in the Archaean and that cratons have been variably eroded and weakened since that time.

The Heat Source Origin of Geothermal Resources in Xiong’an New Area, North China, in View of the Influence of Igneous Rocks

The Xiong’an new area has abundant geothermal resources, and heat source research plays an important role in the geothermal system. Using the logging curve, we calculated the radioactive heat production of sedimentary layers and igneous rocks in non-sample wells; analyzed the influence of igneous rock distribution, residual heat, and its thermal increment on crust; and clarified the heat source origin of hydrothermal geothermal resources in Xiong’an new area. Sedimentary layers data (5,504) of 20 wells were converted to determine the applicable GR-A empirical relationship, and the radioactive heat production of igneous rocks with different lithologies was estimated. Finite element simulations show that igneous rock intrusions in the study area reach thermal equilibrium with the surrounding rock after 0.5 Ma at most. Upon cooling, the difference in thermal physical properties to the surrounding rock only leads to a higher heat flow of about 3.55 mW/m2 in the partial of the Niutuozhen salient. It is known that the development of igneous facies impacts the heat source. Under the geothermal background of “cold crust-hot mantle,” the mantel heat was the primary source, which the Yanshanian intrusions injected into the central salient, increasing the crustal heat by about 12% and the heat source by about 6%. The measured heat flow becomes higher in the salient (raised about 12.04 mW/m2–29.25 mW/m2) where the deep faults developed due to the groundwater convection. Heat conduction from crust-mantle heat flow and heat convection caused by deep faults are responsible for the current geothermal state in Xiong’an new area.

Role of uranium redistribution in radioactive heat production of granitic rocks, Northern Eastern Desert, Egypt

Granitoid intrusions traditionally form a focus for geothermal heat exploration, as granite is a major host for Heat-Producing Elements (HPE; U, Th & K). Airborne spectral gamma-ray data for the study area highlight variations in HPE abundances in granitic rock units, indicating variation in the Radioactive Heat Production (RHP) values of these rocks. The computed arithmetic means of RHP for granitic rocks range from 0.96 µWm−3 for tonalite-quartz diorite to 1.10 µWm−3 for granodiorite, followed by a gradual increase to 1.52 µWm−3 for monzogranite and 2.51 µWm−3 for alkali-feldspar granite. The major control on the distribution of U and Th elements in the granitoid rocks appears to have been primarily of magmatic differentiation and is reflected in the linear correlation between these elements. Besides, subsequent post-magmatic hydrothermal fluids play their important roles in remobilization of profitable secondary U-mineralizations to be trapped and enrichment in the alkali-feldspar granitic rocks.

Radiogenic heat production from natural radionuclides in sediments of the Tigris river in Mosul City, Iraq

In this paper, the concentration of the activity of natural radionuclides is represented by 238U, 232Th and 40K. This concentration was measured by gamma spectroscopy, which was used to determine and calculate radioactive heat production for all radionuclides and their distribution pattern in the sediment samples from the Tigris River in Iraq. The results showed that the activity concentration of these radionuclides was within the allowed limits by the UNSCEAR. Field observations show that the sediments occurred due to the weathering of pre-existing sedimentary rocks that make up the area's geology. The estimated average radiogenic heat production rate was 0.3634 µW/m³. It ranged from 0.2430 to 0.6453 µW/m³, and within the internationally permissible limits, the radiogenic heat production rate in Tigris River sediments was low. It is recommended to conduct a comprehensive radiometric survey to cover all the areas through which the Tigris River passes in Iraq. It will help characterise the radiogenic heat produced for each geological area.

Radioactive heat production characterization of Ar-Rassafeh Badyieh area (area-2), Syria by using aerial gamma ray spectrometric and fractal modeling techniques

Aerial gamma-ray spectrometric technique is used herein to evaluate the radioactive heat production (HP) of Ar-Rassafeh Badyieh Area (Area-2), Syria. The nine already established lithological scored units of Area-2 have been separately characterized for the heat production HP parameter. The Concentration-number (C-N) model and the log-log plots associated with fractal technique are proposed and applied as a new approach to map the measured equivalent uranium (eU), the equivalent thorium (eTh), and potassium (K%) and the computed heat production (HP) of Area-2. The HP of Area-2 varies between a minimum of 0.06 and a maximum of 4.28 ?w/m3 with an average of 0.548 ?w/m3 and a standard deviation of 0.27?w/m3. The highest observed HP values are related to the phosphatic environments represented by two lithological scored units A and B.

Heat Flow Correction for the High-Permeability Formation: A Case Study for Xiong’an New Area

Abstract The Xiong’an New Area is located at the western Bohai Bay Basin, 150 km south of Beijing, China. The area has tremendous high heat flow value within the sedimentary layer, and the average value can reach 90 mW·m-2 within the Niutuozhen Uplift. However, combining the basal heat flow at the top of the metamorphic layer with the heat flow value which was contributed by the radiogenic heat production from the overlying formation, the surface heat flow value was only 65.1 mW·m-2 in this area. Thus, the heat flow value within the sedimentary layer was greatly influenced by other factors. In this study, based on the continuous temperature measurements data from 4 boreholes, thermos-physical parameters (conductivity, radioactive heat production, density, and heat capacity) from 90 rock sample measurements, and the regional stratigraphic development, a two-dimensional thermal-hydraulic modelling was carried out to study the influence of the heat refraction and groundwater convection on the heat flow value. According to calculation results, the heat flow disturbance caused by heat refraction was 10 mW·m-2, and the disturbance value was 20 mW·m-2 for the groundwater convection. Furthermore, when the high-permeability layer thickness was a certain value, with the increasing high-permeability layer buried depth, the influence of the groundwater convection on the temperature field which was used for the heat flow calculation became weak. While when the high-permeability layer buried depth was set up, the influence of the groundwater convection on the above temperature field became stronger with the increasing high-permeability layer thickness.

Phase equilibria modeling of anatexis during ultra-high temperature metamorphism of the crust

Ultra-high temperature (UHT) granulite-facies metamorphism is commonly identified in Mg–Al-rich rocks. Many such lithologies are thought to be metasedimentary rocks based on the presence of detrital zircon. However, whether a metasedimentary protolith is required to form diagnostic mineral assemblages and how much melt is lost during burial and heating to reach UHT conditions varies significantly according to the prograde pressure–temperature path. In this study, integrated thermodynamic modeling, accessory mineral modeling, and trace element modeling has been conducted on an average metapelite composition and average mid-ocean ridge basalt (MORB) composition under open-system conditions. The results show at least three and two melt loss events occur before reaching UHT conditions in initially water-saturated pelitic and basaltic rocks, respectively. Around 22–27 vol% S-type granite and 12–17 vol% I-type granite would be produced during these evolutions, respectively. Melt extraction leads to an increase of Al and Mg in metapelite residua. Mineral assemblage sapphirine + quartz is then allowed to form at higher grades; however, metabasalt does not form these UHT diagnostic assemblages, regardless of the amount of melt lost. During equilibrium melting, crustal differentiation induced by UHT metamorphism would significantly reduce the amount of heat-producing elements (HPEs) in the melt-depleted residuum, which progressively decreases a rock's heat production capacity. In reality, however, new monazite grains likely form during peak metamorphism and some monazite grains would be shielded by porphyroblasts, resulting in an increase of Th in the residua during heating. Even so, we suggest the efficiency of heat production would still decrease, given the heat production rate of Th is much lower than U. Considering some granitic rocks with relatively high heat production are emplaced into the granulite terrane, we suggest that radioactive heat production may be a contributing driving force for UHT metamorphism; however, it is not sufficient. Most heat required to generate UHT granulites must come from hybrid sources, such as advected heat from the mantle, conducted heat from nearby magmatic intrusions, radioactive heat production, and ductile shear deformation.

Petrogenesis of a late-stage calc-alkaline granite in a giant S-type batholith: geochronology and Sr\u2013Nd\u2013Pb isotopes from the Nomatsaus granite (Donkerhoek batholith), Namibia

The late-tectonic 511.4 ± 0.6 Ma-old Nomatsaus intrusion (Donkerhoek batholith, Damara orogen, Namibia) consists of moderately peraluminous, magnesian, calc-alkalic to calcic granites similar to I-type granites worldwide. Major and trace-element variations and LREE and HREE concentrations in evolved rocks imply that the fractionated mineral assemblage includes biotite, Fe–Ti oxides, zircon, plagioclase and monazite. Increasing K2O abundance with increasing SiO2 suggests accumulation of K-feldspar; compatible with a small positive Eu anomaly in the most evolved rocks. In comparison with experimental data, the Nomatsaus granite was likely generated from meta-igneous sources of possibly dacitic composition that melted under water-undersaturated conditions (X H2O: 0.25–0.50) and at temperatures between 800 and 850 °C, compatible with the zircon and monazite saturation temperatures of 812 and 852 °C, respectively. The Nomatsaus granite has moderately radiogenic initial 87Sr/86Sr ratios (0.7067–0.7082), relatively radiogenic initial εNd values (− 2.9 to − 4.8) and moderately evolved Pb isotope ratios. Although initial Sr and Nd isotopic compositions of the granite do not vary with SiO2 or MgO contents, fSm/Nd and initial εNd values are negatively correlated indicating limited assimilation of crustal components during monazite-dominated fractional crystallization. The preferred petrogenetic model for the generation of the Nomatsaus granite involves a continent–continent collisional setting with stacking of crustal slices that in combination with high radioactive heat production rates heated the thickened crust, leading to the medium-P/high-T environment characteristic of the southern Central Zone of the Damara orogen. Such a setting promoted partial melting of metasedimentary sources during the initial stages of crustal heating, followed by the partial melting of meta-igneous rocks at mid-crustal levels at higher P–T conditions and relatively late in the orogenic evolution.

Identification of Possible Heat Sources for the Thermal Output of Enceladus

Abstract We have calculated the amount of radioactive heat production (RHP) that could possibly prevent the postulated underground ocean of Enceladus from freezing. An internal heat source is necessary to justify the observed heat output from Enceladus and to allow the tidal dissipation heating models to work. Also based on the terrestrial evidence, we have assumed that the most common radiogenic element that can produce such internal heat is 238U. Our results show that a minimum amount in the range 38.10–76.59 ppm of 238U, averaged over the whole mass of Enceladus, is necessary to obtain the required RHP. The range of values increases to 63.60–127.70 ppm if we consider only the mass of the rocky portion and 2890–5775 ppm if we consider the mass of the rock + ice portion of Enceladus just below the southern polar area. Even in the latter case, the concentration of uranium is still well below the amount found in high-grade ore on Earth.

Investigation and correlation of radioactive hazards with magnetic parameters and heavy metals of dwelling sand from two major rivers in south India – A comparative study

Cauvery and Palar, two major rivers in Tamilnadu, India, have importance for irrigation, drinking, electricity and river sand is used as a major material of building construction in India. The natural radionuclides such as uranium, thorium and potassium (238U, 232Th, 40K) isotopes are investigated through gamma ray spectrometer with NaI(Tl) detector. The average values of radionuclides and in-situ dose are measured. Related parameters like absorbed dose (ADin & ADout), Annual Effective Doe Equivalent (Ein & Eout), and also hazard indices to assess radiation exposure to human such as average radium equivalent (Raeq), external (Hex)and internal (Hin) hazard indices, Radioactive heat production (RHP), internal and external Excess Lifetime Cancer Risk (ELCRin and ELCRout), Alpha (Iα), Gamma Index (Ig) and Annual Gonadal dose (AGDE) are computed and correlated. This study exhibits that almost all the radioactive parameters are in control by comparing to the world average. Nevertheless, the Cauvery River except site no.20 does not produce a radiological hazard. But, the palar river does slightly produce a radiological risk especially site no.6 shows three times of the world average.

From hot rock to useful energy: A global estimate of enhanced geothermal systems potential

This study demonstrates the theoretical, technical, optimal economic and sustainable potential of enhanced geothermal systems (EGS) globally. A global estimate of EGS is presented in a 1°×1° spatial resolution. Constructed temperature at depth maps are computed for every 1 km thick layer, from 1 to 10 km. Multiple factors such as surface heat flow, thermal conductivity, radioactive heat production, and surface temperature are involved, and obtained from various sources and assumptions. The global EGS theoretical potential is assessed. Available heat content is then estimated using technical constraints for the temperature equal to or higher than 150 °C for any 1 km depth, and presented as thermal energy and electrical power capacity. The EGS optimal economic potential is derived from the optimum depth and the corresponding minimum levelised cost of electricity. The global optimal economic potential in terms of power capacity is found to be about 6 and 108 TWe for the cost years of 2030 and 2050, respectively. If economic and water stress constraints are excluded, the global EGS potential can be as much as 200 TWe. Further, an industrial cost curve is developed for the levelised cost of electricity as a function of EGS technical power capacity. The findings indicate that around 4600 GWe of EGS capacity can be built at a cost of 50 €/MWh or lower. A method is applied to measure the sustainable geothermal resource base. The obtained sustainable potential is found to be 256 GWe in 2050. Results are presented on a country basis and globally.