Crystallochemical studies on davidite from Bichun, Jaipur District, Rajasthan, India

NASA Astrophysics Data System (ADS)

Singh, Yamuna; Saxena, Anubhooti; Bhatt, A. K.; Viswanathan, R.; Shaji, T. S.; Nanda, L. K.

2018-02-01

Crystallochemical data on metamict davidite from albitites and albitised rocks from the Bichun area (Jaipur district, Rajasthan, India) of Banded Gneissic Complex (BGC) are provided. Davidite occurs as euhedral, subhedral to anhedral crystals in the form of disseminated grains and also as fracture filled veins. The crystals of davidite are up to 8 cm in length and 6 cm in width. The powder X-ray diffraction (XRD) pattern of the heat-treated davidite (at 900{°}C) reveals well-defined reflections of crystallographic planes. The calculated unit-cell parameters of the heat treated davidite are: a0 = b0 = 10.3556 Å and c0 = 20.9067 Å, with unit-cell volume (V) = 1941.6385 Å3; and α=β= 90° and γ= 120°, which are in agreement with the values of davidite standard. Geochemical data reveals that the investigated davidite contains 51.5-52.6% TiO2, 14.8-15.1% Fe2 O3, 9.8-10.2% FeO, 6.97-7.12% U3 O8, 6.72-6.92% RE2 O3, 3.85-3.61% K2O, 0.9-1.4% Al2 O3, and 0.8-1.2% SiO2. The calculated structural formulae of the two davidite crystals are: D-1: K_{0.0044/0.004} Ba_{0.0044/0.005} Ca_{0.20/0.20} Na_{0.012/0.012} Mn_{0.053/0.053} Mg_{0.14/0.14} Pb_{0.0076/0.008} Fe_{2.675/2.675} Fe_{1.59/1.59} Y_{0.1175/0.118} P_{0.053/0.053} Nb_{0.008/0.008} Sn_{0.001/0.001} Zr_{0.033/0.033} U_{0.468/0.468} Th_{0.009/0.009} REE_{0.6829/0.683})_{6.05/6.05} (Ti_{12.15/12.15} Fe_{1.9022/1.903} Si_{0.372/0.372} Al_{0.517/0.517} Cr_{0.018/0.018} Co_{0.009/0.009} Ni_{0.027/0.027})_{15/15} O_{36/36} (OH_{0.319/0.319[]1.681/1.681})_{2/2} and D-2: (K_{0.004/0.004} Ba_{0.005/0.005} Ca_{0.20/0.20} Na_{0.012/0.012} Mn_{0.05/0.05} Mg_{0.094/0.094} Pb_{0.007/0.007} Fe_{2.58/2.58} Fe_{1.71/1.71} Y_{0.112/0.112} P_{0.106/0.106} Nb_{0.006/0.006} Sn_{0.001/0.001} Zr_{0.03/0.03} U_{0.48/0.48} Th_{0.009/0.009} REE_{0.665/0.665})_{6.088/6.088} (Ti_{12.48/12.48} Fe_{1.87/1.87} Si_{0.249/0.249} Al_{0.334/0.334} Cr_{0.019/0.019} Co_{0.008/0.008} Ni_{0.04/0.04})_{15/15} O_{36/36} (OH_{0.098/0.098[]1.90/1.90})_{2/2}. The calculated structural formulae are not fully stoichiometric, which could be due to metamict nature of davidite. The characteristic feature of distribution pattern of REE in davidite is unusually high concentration of LREE and HREE and substantially low content of MREE. It may be due to the occupation of REEs in two distinct crystallographic sites in davidite structure, i.e., M(1) and M(O) sites. Chondrite-normalised plot of davidite reveals a pronounced negative Eu-anomaly (Eu/Eu^{*} = 0.30{-}0.39), which suggests extremely fractionated nature of the metasomatising fluids from which davidite had crystallized. Metamict davidite-bearing U ores not only from Rajasthan, but also from other parts of India are likely to yield very high U leachability, thereby making them attractive sources of U, which otherwise are ignored by mineral engineers as uneconomic U ores.

Ages of Some Uranium and Thorium Minerals from East and Central Africa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darnley, A. G.

1961-01-01

method were accepted for minerals from a number of localities: uraninite, Nkana, Northern Rhodesia, 522 plus or minus 15 million years (m.y.); brannerite, Kansanshi, Northern Rhodesia, 503 plus or minus 15 m.y.; uraninite, Shinkolobwe, Katanga, 642 plus or minus 20 m.y.; davidite, Mavuzi, Mozambique, 578 plus or minus 15 m.y.;, monazite, Monkey Bay, Nyasaland, 597 plus or minus 25 m.y.; and samarskite, north-west Kenya, 635 plus or minus 25 m.y. The significance of the results is considered.

Materials. Section 1 of Symposium on the peaceful uses of atomic energy in Australia, 1958, held in Sydney, in June 1958

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The environments of the known uranium occurences in South Australia arc described, and the relation of uranium mineralization with sodic granitic rocks is emphasized. The problems in designing equipment for radiometric prospecting are reviewed. The fabrication and properties of BeO, UO/sub 2/, ThO/sub 2/, and mixed oxides are discussed. The use of pulsing in a uranium extraction pilot plant ion exchange column is described. The wetting of metals by liquid metals is reviewed with emphasis on liquid sodium. The geological nature, extent, and future prospects of minerals with atomic energy applications, occurring in New South Wales are outlined. The developmentmore » of a process for uranium recovery from Mary Kathleen ores is described. Techniques and processes involved in locating, mining, and concentrating davidite-type ores at Radium Hill, South Australia are described. The uranium deposits of the Northern Territory, Australia, are classified and described. The flotation behavior of the simple oxide minerals, uraninite and the colloform variety is discussed. The Port Pirie Treatment Plant for uranium recovery from refractory Radium Hill concentrates is described. The plant utilizes the sulfuric acid-ion exchange process. The uranium deposits of Queensland are described. the details of the production of uranium ore concentrates at Rum jungle near Darwin, Australia, are given. A brief account of the use of neutron diffraction analysis in crystallography is given, and the neutron spectrometers installed on the High Flux Australian Research Reactor are described. (T.R.H.)« less