Granites, uranium deposits

Exploration for economic uranium deposits has expanded to many geologic environments that have been generally overlooked in the past. Most notable among these are (1) granitic uranium deposits, (2) alkalic igneous-hydrothermal uranium deposits, (3) altered acidic or alkalic volcanic ash, ash flow or volcaniclastic uranium deposits, (4) unconformity-related uranium deposits and (5) calcrete uranium deposits in desert groundwater environments. 

Meta.soina.tlte Deposits. Included in the metasomatite deposit grouping are uranium deposits in alkah metasomatites, eg, albitites, aegirinites, and alkah—amphibole rocks, commonly intmded by microcline granite. Examples are the deposits in Espinharasin, Brazil, and Ross Adams, Alaska, as well as the Zheltye Vody deposit in Krivoy Rog area in Ukraine (16). 

Mineralogical, geochemical, and geochronological constraints in the Double S Zone uranium deposit, Lac Turgeon Granite, north shore of the St. Lawrence Seaway, Quebec, Canada... 

Raisanen E. (1986) Uraniferous granitic veins in the Sveco-fennian schist belt in Nummi Pusula, Southern Finland. International Atomic Energy Agency (IAEA), Technical Committee Meeting (TC-571) on Uranium Deposits in Magmatic and Metamorphic Rocks, Salamanca, 12p. 

The tables in this section present thermodynamic data for uranium, americium, technecium, neptunium, plutonium, and auxiliary species. Also presented are chemical analyses of some groundwaters from uranium deposits and granites. 

Chemical analyses and related information for some well waters from uranium deposits and two unmineralized granites (Aspo and Stripa,... 

McLennan, S.M., and S.R. Taylor, 1980, Rare Earth Elements in Sedimentary Rocks, Granites and Uranium Deposits of the Pine Creek Geosynclinc, in Uranium in the Pine Creek Geosyneline, eds J. Ferguson and A.B. Goleby (IAEA, Vienna) pp. 175-190. 

Itoigawa [3], Yusa et al. [4], Shikazono and Utada [5] and Sasao et al. [6] described the regional geology of the Tono District, which includes the Tono Uranium Deposit. Basement granitic rocks overlain by essentially flat-lying sedimentary formations are distinguishing features of the region (Fig. 1). 

Uranium in epigenetic sandstone deposits is believed to have come from such varied sources as weathering of granitic rocks, siliceous tuffs or other uraniferous rocks in the source area for the sandstone devitrification of tuffaceous sediment in or interbedded with the sandstone hydrothermal solutions from nearby magmas and recycling and redistribution of earlier-formed uranium deposits. 

An example of veins with complex mineralogy is the mined-out uranium deposit at Shinkolobwe, Zaire, at the northwest end of the African Copperbelt. It occurs in a faulted transported fold in metamorphosed dolomitic shales of the middle Proterozoic Mine Series of the Roan Group.Uraninite and uranophane mineralization (about 620m.y. ago) was followed by several later mineralizations in which pyrite, molybdenite, monazite, selenium, Co-Ni sulphides and selenides and copper minerals were formed. It is believed that this orebody was formed by redistribution of metals originally deposited in marine sedimentary rocks." The uranium, originally weathered from granites and deposited in the marine sediments, was in low... 

Uranium deposits in this unit are of numerous geological types, but three are typical of the Hercynian orogen (1) intra-granitic deposits related to leucogranites, (2) deposits bound to the contact-metamorphic haloes of granite intrusives in Lower Palaeozoic shales (the so-called Iberian type ) and (3) deposits bound to Permian cover rocks or Permian acid volcanics. Other types are veins in less differentiated granites, veins in metamorphic environments, sandstone-type deposits in Mesozoic or Caenozoic cover rocks in basin structures of the Hercynian space included in or adjacent to the Moldanubian zone (or its Iberian equivalent). 

The Jachymov district (Fig. 1) is less typical as the country rock had already undergone a general metamorphism. Uranium deposits again occur within the exocontact zone, developed in the metasediments, around an autometamorphic late Carboniferous or early Permian granite (probably submitted to an intense deuteric process). The orebodies are typically vein-like. The northeast veins contain the Ni-Co-Bi-Ag-U association. The northeast fractures present clay and quartz breccia fillings and at the intersections with the north-south fractures the five-metal association, plus Zn, again appears. 

Besides the resources estimated at 130/kg there exist other uranium sources, generally with a lower content and at a higher extraction cost. These are either an extension of conventional uranium deposits cultivated at 130/kg or conventional deposits the extraction cost of which exceeds 130/kg because of their limited size, deep location or presence in remote areas. Examples of these additional uranium sources are the vast high-cost resources associated with the Elliot Lake deposits in Canada, the 5000-10000 ton of uranium at costs of more than 130/kg in Italy, the 12000 ton contained in granitic rocks at a cost of 130- 260/kg in Namibia, the 141000 ton contained in the conglomerates and the 46000 ton in the surface sediments in South Africa at a cost of 130- 260/kg and the vast quantities of uranium contained in the sandstones of Colorado, Wyoming and New Mexico. 

Intrusive Deposits. Deposits included in the intmsive deposit type are those associated with intmsive or anatectic rocks of different chemical composition, eg, alaskite, granite, monzonite, peralkaline syenite, carbonatite, and pegmatite. Examples include the uranium occurrences in the porphyry copper deposits such as Bingham Canyon and Twin Butte in the United States, the Rossing Deposit in Namibia, and Ilimaussaq deposit in Greenland, Palabora in South Africa, and the deposits in the Bancroft area, Canada (15). 

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