Uranium secondary minerals

The Koongarra U deposit in the Northern Territory of Australia has been studied to evaluate the processes and mechanisms involved in the geochemical alteration of the primary ore zone, and to model the formation of the secondary U ore zone and dispersion fan (Duerden 1991 Duerden Airey 1994). Studies of the distribution of the U in the dispersion fan (Murakami et al. 1991) have provided data on the fixation of U leached from the primary ore deposit. Their work has shown that, for this system, fractures are not only preferential pathways for ground-water movement but also contain secondary minerals with high sorption capacity for elements such as U. Even in the monsoonal climate, in which this deposit is located, a significant proportion of the uranium has not been released from the vicinity of the primary ore body. 

TORBERN1TE. An ore of uranium with the composition, CudJO h (PO4)2 8 — I2H2O, green, radioactive, tetragonal, and lsomoiplious with autunite. Occurring in tabular crystals or in foliated form, the mineral is commonly a secondary mineral. 

TYUYANUN1TE. An ore of uranium with the composition. Ca(U02)2 (V04)2 5 — 8H2O, which occurs in yellow incrustations as a secondary mineral. The mineral is orthorhombic, It occurs as a secondary mineral as incrustations on limestones, and as disseminated impregnations in sandstones. Found abundantly 111 the Western United Stales, at Grants, New Mexico, and in Wyoming, Utah, Colorado. Nevada, Arizona and Texas. Also at Tyuya Muyan in Turkestan, the former U.S.S.R. 

That the atomic weight of uranium lead is extremely variable has already been shown. In order to interpret this variability its sources must be studied both geologically and mineralogically. On the geologic side of the question the uranium ore can be divided in to three principal classes, which are sharply distinct. The definitely crystallized varieties of uraninite occur in coarse pegmatites, associated with feldspar, quartz, mica, beryl, and other minor accessories. The massive pitchblende is found in metalliferous veins, together with sulphide ores of copper, lead, iron, zinc, and so forth. As for camotite, that is a secondary mineral, found commonly as an incrustation on sandstone, and often, also upon fossil wood. There may be other modes of occurrence, but these are the most distinctive. 

Unconformity-related deposits are found near principal unconformities. Examples include the ore bodies at Quff Lake, Key Lake, and Rabbit Lake in northern Saskatchewan, Canada, and in the Alligator Rivers area in northern Australia. Sandstone deposits are contained in rocks that were deposited under fluvial or marginal marine conditions. The host rocks nearly always contain pyrite and organic plant matter. The sediments are commonly associated with tuffs. Unoxidized deposits of this type consist of pitchblende and coffinite in arkasoic and quartzitic sandstones. Upon weathering, secondary minerals such as camotite, tuyamunite, and uranophane are formed. More information on these and other uranium deposit types is available (1). 

DaH Aglio, M., Gragnani, R. and Locardi, E., 1974. Geochemical factors controlling the formation of the secondary minerals of uranium. In Formation of Uranium Ore Deposits. International Atomic Energy Agency, Vienna, pp. 33—48. 

Dali. Agi.io, M, R. Gragnani, and E. Ixktardi. 1974. Geochemical factors controlling the formation of secondary minerals of uranium. Formation of uranium deposits. Froc. symp. Inti. Atomic Energy Agency, pp. 33-47, Vienna. 

Some secondary materials, which have been produced geologically as a result of natural chemical action on the primary minerals, have their uranium already in the hexavalent state and are fairly readily leached by dilute sulphuric or hydrochloric acid without an oxidant these include carnotite, autunite, and torbernite. Other secondary minerals such as davidite and pyrochlore are more refractory and are not amenable to dilute acid leaching. 

Astrocyanite-(Ce) is a new mineral described by Deliens and Piret (1990). It occurs as bright blue millimeter-sized rosettes in a uraninite matrix in the Cu-Co deposit of East Kamoto, southern Shaba, Zaire, associated with other uranium and rare earth secondary minerals such as kamotoite-(Y), shabaite-(Nd) and fran oisite-fNd). 

Most uranium minerals occur in all of the several types of ore deposits. A given deposit usually has no more than two reduced minerals. The oxidized minerals that occur in the deposit depend on the Eh-pH conditions and the availability of reactive anions. In the absence of reactive anions, hydrated oxides and uranates form. The uranyl ion is, however, fairly soluble and groundwater can effectively disperse it a considerable distance from the reduced source. The uranyl minerals that are then deposited are complex compounds that employ available oxyanions. The rate of formation of these secondary minerals can be very rapid, as is evidenced by mineral formation on the walls of mine drifts in a matter of months after the drifts have been opened. In all deposits there is usually a zonation of mineralogy in which a reduced mineral... 

Non-refractory primary uranium minerals are rare, but uranothorianite has been reported from Palabora" and uraninite from Lake Nipissing, Ontario, Canada. Most car-bonatite uranium-bearing minerals me refractory phases. Uranium occurs as a minor or trace element in zircon, apatite, baddeleyite, perovskite, monazite, pyrochlore minerals, goyazite, bastnaesite, allanite, anatase, rutile, etc. The secondary mineral autunite occurs in soil covering the Araxa carbonatite. " ... 

Milton, G. M. Brown, R. M. 1986. Adsorption of uranium groundwater by common fracture secondary minerals, Canadian Journal of Earth Sciences, 24, 1321-1328. 

Ames, L. L., McGarrah, S. E. Walker, B. A. 1983. Sorption of trace constituents from aqueous solutions onto secondary minerals. I. Uranium. Clays and Clay Minerals, 31(5), 321-334. 

Spinels. There are limited experimental data on uranium and thorium partitioning between magnetite and melt (Nielsen et al. 1994 Blundy and Brooker 2003). Both studies find U and Th to be moderately incompatible. Blundy and Brooker s results for a hydrous dacitic melt at 1 GPa and 1025°C give Du and D h. of approximately 0.004. The accuracy of these values is compromised by the very low concentrations in the crystals and the lack of suitable SIMS secondary standards for these elements in oxide minerals. Nonetheless, these values are within the range of Djh of magnetites at atmospheric pressure 0.003-0.025 (Nielsen et al. 1994). It is difficult to place these values within the context of the lattice strain model, firstly because there are so few systematic experimental studies of trace element partitioning into oxides and secondly because of the compositional diversity of the spinels and their complex intersite cation ordering. 

Asphaltic Sandstone from Lodeve-Mas Alary, Herault, France. This rock of Permian age contains, together with uraninite, secondary uranium minerals, sulfides, molybdates, etc. (12, 15) (Figure 3). 

Dr. Gluskoter. What is the evidence for a syngenetic origin for the uranium minerals in the Swiss anthracite Why could this not be secondary deposition along planes of weakness (bedding) ... 

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