Věra Vaňková

Radioactivity and heat production data from several boreholes in the Bohemian Massif

SummaryThe radiogenic heat production of rock samples from boreholes in the Bohemian Massif has been calculated from gamma-radiometric determinations of Th, U and K contents. The results, in general, fit the heat flow distribution on the territory of Czechoslovakia[1]. The values of heat production are in the range from 1.1µW m−3 in the eastern part to 4.4µW m−3 in the north-western part of the Bohemian Massif.

A method of reducing the disturbing effects in gamma — Spectrometric measurements of rock radioactivity

SummaryThe long-termed stability of the NTA 1024 Gamma spectrometer was investigated. In order to reduce the influence of the instability of the linear amplifier, a method of mathematical transformation of the spectrum was introduced.

Gamma-ray absorption and chemical composition of neovolcanic rocks

SummaryGamma-ray absorption coefficients μCs137 for a set of 49 neovolcanic rocks from the Bohemian Massif were measured; their values varied in the range from 0.2092 cm−1 to 0.2464 cm−1 with an average of 0.2313 cm−1. The dependence of μCs137 on the density ϱ could be expressed by the relation μ=0.0656 ϱ+0.0348. The absorption coefficient was correlated with the content of several oxides determined by chemical analysis. In accordance with the results in [1], the values of the absorption coefficient were found to increase with the increasing content of oxides bound to dark minerals (FeO, Fe2O3, MgO, CaO), and to decrease with the increasing content of oxides bound to light minerals (Si2O, Al2O3).

Cs137 gamma-ray absorption and density of rocks

РезюмеРабота посвящена исследованию зависимости коэффициента поглощения μCs137 горных пород от их плотности. Показывается, что эта зависимость не строго линейна, и что она точнее характеризуется напр, при помощи кривой (4). Из-qzа очень малого искривления этой кривой, в коротких участках возможно заменить её прямыми. Устанавливая такие частные зависимости, следует учитывать химический состав горных пород и, вследствие того, создавать группы по родственности типов горных пород. Небольшие средние квадратические ошибки исследований (см. табл. 4) для всех групп показывают, что при определении плотности горных пород ϱ при помощи коэффициента поглощения μ достигается точность около 1% и лучше.

Heat production data from airborne and laboratory measurements of gamma-ray activity of rocks

SummaryThe paper discusses the obvious experimental relation between the laboratory determinations of total gamma-ray activity, expressed in equilibrium uranium concentration, and heat production due to radioactive decay. The heat production data were calculated by means of the concentrations of uranium, thorium and potassium determined spectrometrically, together with the conversion factors into the rate of heat generation. The obtained relation may help define the typical heat production for characteristic surface rocks and estimate their contribution in heat flow study. Between the gamma-ray activity recorded during aeroradiometric mapping and the laboratory radiometric measurements of surface rock samples, there is also an experimental relation, which can be used further in estimating the value of surface heat production at a chosen locality.

Distribution of radioactive elements in three progressively metamorphosed pelite series of the Bohemian Massif

SummaryThe variations of the content of radioactive elements in pelitic rocks in dependence on the grade of metamorphism were studied in three regions of the Bohemian Massif with a different character and age of metamorphism. The concentrations of Th, U and K were determined by gammaspectrometric method, the major elements Si, Ti, Al, Fe, Mn, Ca, K, P by the X-ray fluorescence method. An increasing mobility of radioactive elements was found with the help of variation diagrams in the higher stages of metamorphism, the migration being apparent especially for Th and usually starting in the garnet or biotite zone. A significant negative correlation of both Th and U content with the content of SiO2 was determined. It was found that the behaviour of Th and U during the metamorphic processes reflect a different character of metamorphism. In agreement with[1] the decreasing tendency of Th and U during progressive metamorphism was confirmed in the metamorphic sequences of the Barrovian type, whereas an opposite trend in sequence of periplutonic character was found.

Gamma-ray absorption coefficients and chemical composition of tertiary volcanic rocks

SummaryGamma-ray absorption coefficients

Gamma-ray absorption in granodiorite

\mu _{Cs^{137} }