Results 1 - 10 of 404
Results 1 - 10 of 404. Search took: 0.023 seconds
|Sort by: date | relevance|
[en] Isotopic ages from metamorphic and plutonic rocks of the Atlantic area of North Patagonian basement indicate that the main crustal tectonic events occurred during the late Proterozoic to early Paleozoic times. Rb/Sr and U/Pb data in the 550-470 Ma interval suggest an old tecto-thermal activity during the upper Brazilian Cycle (Rio Doce Orogeny). At regional scale, the comparable Neo proterozoic basement of Ventania and sedimentary for eland cover of Tandilia continues to the Northeast, in the Dom Feliciano Belt. A possible correlation of the North Patagonian basement with igneous-metamorphic relics of Central Argentina (Pampean Ranges of San Luis-Cordoba and at La Pampa province) is also indicated. (author)
[en] Geologically, Madagascar is divided in two parts. The larger, eastern region comprises Precambrian crystalline basement which can be divided into six domains; from north to south these are the Bemarivo, Antongil-Masora, Antananarivo, Ikalamavony, Androyen-Anosyen and Vohibory, respectively. The western region is covered by three important basins: Diego Basin, Mahajanga Basin and Morondava Basin. A small basin on the eastern coast is also present. Additionally, there exists the Lake Basin in the central part of the country. Uranium occurrences have been found within two domains in crystalline bedrock, the Antananarivo and Anosyen Domains, and these are believed to have potential. There are also two deposits in the Morondava Basin and in the Lake Basin. Two types of uranium deposit occur in crystalline basement and two other types in sedimentary cover. The present work delineates the occurrences already known and assesses the uranium potential of Madagascar, including details of a new potential uranium deposit.
[en] The Gogi uranium deposit occurs at the southern margin of the Bhima Basin in Karnataka. Mineralization is hosted by both basement granites and overlying Shahabad limestones. This study characterizes Gogi mine sample to provide relevant information on mineral constituents and liberation characteristics for effective processing. An integrated approach consisting of petrography, sizing, density fractionation of the sized ore followed by quantitative mineral estimation by microscopic grain counting has been carried out. The sample is constituted by 1) radioactive ore minerals (0.886%) represented by coffinite, pitchblende, urano-organic complex, labile uranium, 2) non-radioactive ore minerals (6.58%) composed of pyrite, marcasite, chalcopyrite, galena and 3) gangue minerals (92.539%) constituted by calcite (61.57%), quartz+chert (13.10%), feldspar (1.59%), biotite + chlorite + clay (5.89%) and dolomite, hornblende, epidote, zircon and barite. Uranium is mainly associated with Methylene Iodide heavies (∼ 60-70%), followed by Methylene Iodide lights (∼ 30%) and Bromo lights (∼ 5%) with higher values in the coarser fractions (+100). (author)