Natural radioactivity in rocks of the Modane-Aussois region (SE France)

The activity concentrations of 40K, 232Th, and 238U in the characteristic rocks of the Modane-Aussois region (Western Alps, France) were determined using an HPGe gamma-ray spectrometry system. The activity concentrations of 40K varied from 18 Bqkg-1 (limestone dolomite) to 392 Bqkg-1 (calcschist), while those of 232Th varied from 0.7 Bqkg-1 (limestone dolomite) to 18 Bqkg-1 (calcschist). The activities associated with 238U ranged from 9 (quartzite) to 29 Bqkg-1 (dolomite). In the investigated rock samples, concentrations of 238U (ppm) and 40K (%) had a strong negative correlation

57Fe Mossbauer spectroscopy of radiation damaged allanites

Metamict minerals contain radioactive elements that degrade the crystal structure of the minerals. The degradation occurs primarily through progressive overlapping recoil nuclei collision cascades from ®-decays of 238U, 232Th, 235U and their daughter products. We report the results of 57Fe Mossbauer spectroscopy, gamma-ray spectrometry and microprobe analysis of three partially metamict allanites, (Ca,Ce,REE)2(Fe2+; Fe3+)(Al; Fe3+)2O[Si2O7][SiO4](OH) where REE stands for rare earth elements. The samples were collected in pegmatites from Reno, Nevada (USA), Franklin, New Jersey (USA) and Nya Bast- nas Field (Sweden). The absorbed ®-dose for these minerals was found to range from 5:8 £ 1014 ®-decay/mg for the allanite from Reno to 1:9 £ 1015 ®-decay/mg for the allanite from Franklin. The Mossbauer spectra show a decrease in the Fe2+ doublet intensity with increasing absorber ®-dose. We also observe an increase in the line widths of the Fe2+ and Fe3+ doublets with increasing absorbed ®-dose

Preliminary results of 57Fe Mössbauer spectroscopy of metamict samarskite after one-hour high temperature annealing in argon

This work was supported by National Science Centre, Poland, through grant no. PW-0415-003.The preliminary results of 57Fe Mössbauer spectroscopy and X-ray diffraction (XRD) of fully metamict samarskite dated at ~1500 Ma, which absorbed α-dose of 6.5 × 1017 α-decay mg-1, are reported after one-hour annealing at 673, 873, 1173 and 1373 K in argon atmosphere. Metamict minerals contain radioactive elements that degrade their crystal structures over geological time. All the Mössbauer spectra obtained can be fitted to two quadrupole doublets assigned to Fe2+ and Fe3+ in octahedral positions. The relative contribution of Fe2+ (Fe2+/Fe) reaches a minimum of 0.10 at 1173 K.NC

222Rn and 220Rn concentrations in soil gas of the Izera Massif (Sudetes, Poland) as a function of sampling depth

This research presents soil gas 222Rn and 220Rn concentrations measured at 17 locations in the Izera Massif of southwest Poland. The average 222Rn concentrations at sampling depths of 10, 40 and 80 cm were 8, 78 and 224 kBq m–3, respectively. The average 220Rn concentrations for the same depths (10, 40 and 80 cm) were 6, 10 and 13 kBq m–3, respectively. Profiles of the concentrations versus depth can be fitted by exponential, linear and polynomial functions for soils developed on fault zones, above uranium mineral deposits, and above faulted uranium deposits, respectively. Soils developed on bedrock without fault zones or uranium mineralisation exhibit concentrations that follow a power function with an exponent of p <1

57Fe Mossbauer spectroscopy of annealed metamict davidite

This paper reports preliminary results of 57Fe Mössbauer spectroscopy and X-ray diffraction (XRD) studies of metamict davidite samples (La,Ce,Ca,Th)(Y,U,Fe)(Ti,Fe,Mn)20(O,OH)38 after high temperature annealing in an argon atmosphere. The Mössbauer spectra show a gradual decrease of quadrupole splitting and line width values of an Fe3+ doublet with increasing annealing temperature. Rather unexpected feature of these spectra for an Fe2+ doublet is a considerable increase of the line width with progressive crystallinity and a simultaneous decrease of both quadrupole splitting and isomer shift values. Changes of the hyperfine parameters as a function of the annealing temperature appeared as sensitive indicators of the thermal recrystallization process of metamict davidite similar to metamict silicates

Gamma background measurements in the Gran Sasso National Laboratory

In situ gamma-ray measurements were taken at eight locations in the Gran Sasso National Laboratory (Italy). Count rates for gamma radiation within the energy range of 7–2,734 keV varied from 8 to 60 c s-1. The arithmetic mean was 49 c s-1 for measurements taken without a collimator. The average gamma flux inside the Lab was 0.25 c cm-2 s-1. The sedimentary rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium, equal to 1.7 and 1.4 Bq kg-1, respectively

Gamma background measurements in the Laboratoire Souterrain de Modane

In situ gamma-ray measurements were taken at six locations in the Modane Underground Laboratory. Count rates for gamma radiation within the energy range of 7–2734 keV varied from 15 to 108 cs-1. The arithmetic mean was 79 cs-1 for measurements taken without a collimator. The metamorphic rocks surrounding the Lab are characterized by low activity concentrations of uranium and thorium equal to 12 and 10 Bq kg-1, respectively

222Rn and 220Rn concentrations in selected soils developed on the igneous rocks of the Kaczawa Mountains (Sudetes, Poland)

This study presents the preliminary results of 222Rn (radon) and 220Rn (thoron) concentrations that were measured in the soils developed on igneous rocks including mafic (pillow lavas, basalts and melaphyre) and acid (keratophyre, rhyolite and rhyolitic tuff) rocks at ten locations in the Kaczawa Mountains (SW Poland). The measurements were carried out at sampling depths of 10, 40 and 80 cm using a RAD7 portable radon system. The highest concentrations of radon (222Rn) were mainly observed in the soils overlaying acid igneous rocks. The highest value of 11 kBq m-3 was obtained at a depth of 10 cm for soils overlaying melaphyre. At depths of 40 and 80 cm, the averages of 222Rn concentrations showed the same values of 3.6 kBq m-3 for all of the soils investigated. The highest concentrations of thoron (220Rn) were observed in soils overlaying acid igneous rocks, i.e. the value of 49 kBq m-3 at a depth of 40 cm for soils overlaying rhyolitic tuff. In the soils developed on basalts, the average concentrations of 222Rn increased with the sampling depth, whereas the average concentrations of thoron (220Rn) decreased with increasing sampling depth. Positive correlations were found between 232Th activity in the parent rocks and soil gas 220Rn concentrations at all of the sampling depths, whereas a positive correlation between soil gas 222Rn and the 238U activity concentration in the parent rocks was only found at a depth of 40 cm

57Fe Mossbauer study of stilpnomelane and associated chlorite from polish granite pegmatites

This paper reports the results of 57Fe Mössbauer study of stilpnomelane K0.6Fe6(Si8Al)(O,OH)27 .2H2O from Żółkiewka (Lower Silesia, Poland). Stilpnomelane in paragenesis with chlorite, tourmaline, claevelandite and zeolites has been found in granite pegmatites in quarries at Żółkiewka. The samples of naturally weathered stilpnomelane and chlorite from the same fragment of rock were also studied. The Mössbauer spectrum of an untreated sample could be fitted to two Fe2+ doublets and two Fe3+ doublets. The Fe2+ doublets have similar isomer shifts, but they distinctly differ in values of quadrupole splittings. Ferric iron, octahedrally coordinated occurs in three different environments represented by two doublets. The first of them, assigned to combined M1 + M2 positions and the second one assigned to M3 site with parameters IS = 0.36 mm/s and QS = 2.07 mm/s is visible in the spectra up to 880°C. This doublet is characteristic of stilpnomelane and can be regarded as a “fingerprint” of this mineral. After heating at 200°C, the relative content of Fe2+, ΣFe2+/ΣFe, decreases to 0.22 what means a 50% decrease in comparison to the initial value observed in the untreated sample. At about 1000°C, complete breakdown of the stilpnomelane structure takes place and the Mössbauer spectrum consists of two sextets and two ferric doublets. Abnormally high content of Fe2+ in naturally weathered stilpnomelane (0.70) comparing to the untreated sample of stilpnomelane (0.45) indicates that the sample had to be subjected to hydrothermal processes operating locally. Almost the same contents of divalent iron and hyperfine parameters of Fe2+ and Fe3+ doublets in weathered stilpnomelane and associated chlorite suggest that the process of chlorite transformation into stilpnomelane seems to be very probable

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