• U Aswathanarayana

      Articles written in Proceedings – Section A

    • Studies on south Indian radioactive minerals - Part I. Samarskite from Nellore

      U Aswathanarayana

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      Samarskite, a radioactive niobotantalate occurring in the Nellore pegmatites, has been studied in detail. The investigations comprise the determination of physical and optical characters, chemical composition, autoradiographic studies, distribution pattern, calculation and interpretation of age. The available data on Nellore Samarskite has been critically examined and it has been shown that the controversy raised by Holmes concerning the age of the Eastern Ghats can be solved, if the samarskite specimen analysed by Sarkar and Sen Sarma is understood to belong to the Gaya group of minerals, as has been later suggested. A tentative Archæan succession table has also been suggested.

    • Studies on South Indian radioactive minerals - II. Allanite from Madura

      U Aswathanarayana

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      Allanite, a cerium-bearing epidote occurring in the pegmatites of Kavarkattumalai, Madura District, has been studied in detail. The investigations comprise the determination of physical and optical characters, chemical composition, mineral formula, and autoradiographic studies. Attempts have been made from a study of the data on metamict and non-metamict allanites to formulate the changes that allanite undergoes when it becomes metamict. Evidence has been collected to show that the allanite from Madura had become metamict and is hence of dubious value as an age index.

    • Studies on diffusion - Part I. Diffusion of radioactive matter through plates

      U Aswathanarayana S Ramamurthy

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      As a part of an attempt to develop new methods of measurement of diffusion constant of metals and non-metals into minerals using radioactivity techniques, expressions are derived to relate the processes of diffusion and the emission of alpha-particles under three sets of possible experimental conditions. The first case pertaisn to a plate whose thickness is equal to the characteristic range of the alpha-rays of the radio-nuclide used. Under the second case is considered a plate thicker than the characteristic range fo the alpha-rays in the plate. The third deals with cases wherein the radioactive matter used emits alpha-rays with different ranges less than the thickness of the plate.

    • Geochemical studies in the uranium prospect at Umra, Rajasthan - I. Geochemistry of waters

      V V S S Tilak U Aswathanarayana

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      With the objective of investigating the geochemistry of the natural waters of the uranium prospect at Umra, Rajasthan, the concentrations of uranium, nickel, cobalt, copper, vanadium, etc., in the natural waters have been determined and their distribution patterns have been interpreted in the light of the geology of the area, the climatic and hydrological conditions prevalent there and the geochemical behaviour of the elements concerned. It is found that there is a marked contrast in the uranium content of winze and well-waters. The presence of copper in waters despite their high pH is ascribed to the tendency of copper to form colloidal suspension of basic carbonates. The observation, that vanadium is present in the secondary uranium-vanadium minerals but is absent in the waters, could be explained in the light of the geochemical behaviour of the element. The concentration of cobalt in most of the water samples and its absence in some is traceable to the controlling effect of pH on the mobility of cobalt. Nickel in waters might have been ‘scavenged’ and absorbed on hydrated iron oxides, which explains the absence of nickel in waters. Mention is made of the health hazard involved in drinking water from one of the wells with high content of uranium.

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