HI ' I t \ HIIIWIIHIW ‘ L I B R A R Y Michigan Sta” University W— This is to certify that the thesis entitled URANIUM-SERIES DISEQUILIBRIUM INVESTIGATIONS OF THREE SURFICIAL URANIUM DEPOSITS presented by Richard Lively ed M M has been accepted towards fulfillment of the requirements for Masters degree in Geology 6 \\ R; .M ‘ Major professor Date ') 7 0-7639 URANIUM-SERIES DISEQUILIBRIUM INVESTIGATIONS OF THREE SURFICIAL URANIUM DEPOSITS By Richard S. Lively A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology 1978 ABSTRACT URANIUM-SERIES DISEQUILIBRIUM INVESTIGATIONS OF THREE SURFICIAL URANIUM DEPOSITS by Richard S. Lively 230 234 Th and U relations from three near-surface uranium deposits indicate that significant uranium accumulations have occurred during the Pleistocene. h 238 226m. have allowed Data from these isotopes in conjunction wit U and calculations of mineralization ages and have furnished positive evidence of significant uranium migration in ground water, under near-surface conditions. Analytical results from samples collected from deposit "K" in southern Africa indicates uranium mineralization took place approximately l+0,000 years B.P. The results also indicates at least one and possibly more period(s) of post- depositional migration of uranium and radium. Samples collected from the uranium deposit at Yeelirrie, Australia resulted in inconclusive ages. Due to isotope movement within the system only two apparent: 230'l'h/ZM U ages could be calculated. A maxium age of 261,000 yr B.P. was established, but due to the extent of the deposit and the open system, this age does not represent the deposit as a whole. Results from sample collected from Kelowna, British Columbia, (Lassie Lake), indicate a maxium mineralization age of 224,000 yr B.P. Other areas at 230 [230 Kelowna show evidence of significant uranium migration resulting in Th U ratios greater than unity, thus making age calculations impossible. TABLE OF CONTENTS ListOfTables ....... OOOOOOOOOOOOOOOO .......... O OOOOOOOOOOOOO 0...... III IntrOduction ........ 00...... ...... 00...... ........ O ..... O .......... 6 Geochemistry and Isotope Fractionation of Uranium . . . . . . . . . . . . . . . . . . . . . . 7 Geochronology.................................. ...... ..... .....12 Method ....... . ................... ............. . ..... .......15 ResultsandInterpretation...... ......... ...... . ........ .17 1. Southern Africa, Deposit "K" . ....................................... l7 2. Yeelirrie, Western Australia. ........................................ 22 3.1(elowna,BritishColumbia.......................................... 35 Conclusions............ ...... ....... ...39 AppendixA ........................................... ”#2 List of References . . . . . .......... . ....... . . . . ............. . ........ . . 48 II LIST OF TABLES Uranium Concentrations, Isotope Activity Ratios, and Calculated Ages for Dems‘it "K" I. I O O 0.... O O O O O O O O I I O 00...... ........ 0.0.00.00000000021 226 Comparison of Equivalent Uranium from Ra and Determined Uranium . . . . 22 Uranium Concentrations, IsotOpe Activity Ratios, and Calculates Ages for Yeelirrie...OOOOOOOOOOOOOOO0.0.0.0.000... 0.0.00.00000000000000033 Uranium Concentrations, Isotope Activity Ratios, and Calculated Ages for KelownaOOOOOOOOOOOOOOOO.0.O...O.O0......IOOOOOOOOOOIOOOOOOOOO.38 III LIST OF FIGURES Stratigraphic Correlation - Deposit "K" Sample Location and Isotope Activity Ratios ................... . . . . . . . . . . Relative Activity Ratios in Relation to the Age of Uranium Accumulation . . . Sample Location and Outline of the Ore Deposit Based on Diamond Drilling . Outline of Yeelirrie from Radiometric Survey . . . ........ . . . . ...... . . . . . . . Geomorphological Profile of the Yeelirrie Drainage Basin . . . . . ...... . . . . Idealized Section-Showing the Setting of Basal Type Uranium Deposits at KelownaOOOOOOOOOOOO00.... IV/ . 19 20 29 32 36 INTRODUCTION Presently there is an intense interest in uranium ore deposits because of their great economic value, In 1971 the average price per pound of U308 was $6.20; in 1977 $42.40 and the projected price for delivery in 1980 is $51.05/lb. (U.S. Bureau of Mines). This represents an increase of 82396 in less than ten years. Because of the rapid rate of appreciation, areas of low yield uranium which were previously uneconomical can now be profitably mined. Aside from these economic aspects, uranium deposits present many interesting and important geochemical problems, some of which can be investi- gated by means of isotopic disequilibrium studies. While uranium and thorium isotopic disequilibrium is not in itself a direct exploration tool, results from such studies can be useful in terms of understanding exploration anomaly patterns and identifying the presence of chemical changes in the enviroment through changes in the isotope ratios. It is also possible under certain circumstances to derive an age of uranium mineralization as well as discern recent movements of uranium in the surficial environment. Of specific interest in this study are three near surface uranium deposits from southern Africa, Western Australia and western Canada. The objective of the study is to analyize the isotopic disequilibrium within the deposits and where possible, establish an age of mineralization. Samples from these three areas were kindly provided by Professor A.A. Levinson of the University of Calgary. Previous application of U-series disequilibrium studies to uranium deposits include Rosholt (1961), and Rosholt et al., (1961) who investigated uranium 231 Pa and 230 Th relationships with both parent accumulations through the use of and daughter isotopes. He concluded that the accumulations were recent and could be related to ground water movements. Rosholt et al., (1964, 1965) and Dooley et al., (1964), investigated isotope disequilibrium and fractionation in roll- front uranium deposits from sandstones in Wyoming and Colorado. They found that disequilibrium was related to changes in the water table and oxidation potential. Ostrihansky (1976), used U-series isotope relationships to classify periods of uranium accumulation in uranium ore deposits from the Elliot Lake 234U region of Ontario, Canada. Cherdyntsev (1971) in his extensive review of noted extensive variations in isotope ratios derived from uranium minerals, uranium ore bodies and ground waters circulating through ores and crystalline rocks. GEOCHEMISTRY AND ISOTOPE FRACTIONATION OF URANIUM 4+ 6+ Uranium exists in nature in two stable valence states, U and U Primary uranium, that found in crystalline rocks and the elastic sediments derived from them, usually is in the 4+ state and as such is insoluble under near surface conditions. U6+ on the other hand, is soluble and is widely distributed throughout the surficial environment where oxidizing conditions exist. Removal of uranium from crystalline rocks depends upon a number of parameters, including the geochemical nature of the weathering environment, the degree of weathering, and the amount of uranium present. Granites and pegmatites for instance, have much higher uranium concentrations (3-50 ppm), than do basalts or other basic rocks (1-3 ppm or less) resulting in higher uranium 8 concentrations for ground waters circulating through the former (Szalay and Samsoni, 1969; Handbook of Geochemistry, 1969). The oxidation state of the uranium and therefore the oxidation potential of the weathering environment is probably the most important feature in the removal and transportation of uranium in the near surface environment. Beyond that however, the composition of the waters will influence both the amount of uranium in solution and its subsequent transportation. The bicarbonate (HCOB) content of the waters has a large affect both on leaching and transportation because uranium 6+ forms very stable uranyl carbonate complexes of the type (UOZ(CO3) 2 (H20) )2 2' and (U02(C03)3) 4', which can exist over a wide pH range from about 3.5 to 8.0 (Hostetler and Carrels, 1962). These carbonate complex are the predominant form of uranium transport in the surficial environment (Grunner, 1956; Lisitsin, I962; Hostetler and Garrels, 1962; Serebryakova, I964; Kyuregyan and Kocharyan, 1969). Waters low in bicarbonate will then be less able to leach uranium from crystalline rocks and will also be less important in the subsequent removal of uranium from uranium minerals (Szalay and Samsoni, 1969; Grandstaff, 1976). Since most ground waters are within the pH range 4.5 to 8, (see Bass-Becking, et al. 1962), leaching and transportation of uranium should occur under oxidizing conditions. Other types of complexes are also stable under near-surface conditions. These include uranyl and uraneous sulfates, chlorides, silicates and phosphates. Sulfide and chloride complexes form in a pH range below 3.5 and are unstable at higher pH values (Hostetler and Carrels, I962). Uranyl silicate complexes are less stable than either the sulfate or chloride complexes and are found in waters of neutral to alkaline pH. They will rapidly decompose if a large decrease in pH is 9 encountered or the waters become concentrated in carbonate or sulfate ions where the uranium will form the more stable complexes (Yermolayev et al., 1965). Phosphates, when present in solution will also form very stable complexes with uranium (Langmuir and Applin, 1977). If no complexing ions are present in solution, uranium will occur as U0;+ or UOZOH+, depending upon the pH of the waters (Hostetler and Garrels, 1962). Fractionation of uranium isotopes and separation from their daughter nuclides is also related to the geochemistry of the ground waters. The excess is 234U which is found in most ground waters (Cowart and Osmond, 1977) is thought 234 to relate to a preferential oxidation of U to the 6+ valence state, thus making it more easily removed into solution by circulating surface and ground waters. Thorium is very insoluble under near-surface conditions and thus not transporated in aqueous solution (Dement'yev et al., 1965). It can, however, be transported adsorped on clastic material. A number of mechanisms have been proposed to account for the preferential 234 oxidation of U, most of which are related to radioactive decay. When an alpha particle is ejected from the nucleous of a 238 U atom, the resultant decay product undergoes a recoil, called the Sziliard-Chalmers reaction (Friedlander, et al. 1955). Chemical bonds holding the atom in its lattice position are ruptured by the energy of the recoil, resulting in a dislocation of the atom, in this case 234% which rapidly decays to 23“Pa and 23“ U. As the atom is no longer firmly bound, it can then be more readily removed into solution or migrate through the lattice until stopped by micro-cracks and fractures where it is easily available for oxidation and removal by ground waters (Cherdyntsev, 1971). Others argue that alpha decay is energetic enough to strip electrons from the atom during the recoil 10 234 process, producing U which is already in the oxidized state (Rosholt et al., 1963, 1966). Cowart and Osmond (1977) feel that the resultant decay product will take on the oxidation state of the environment wherein it is located regardless of decay related phenomenon. Whatever the case, it is necessary for the environment to remain oxidizing to prevent the reduction of U6+ back to U“ if significant uranium mobilization and transportation is to occur. 234 _238 Another method of U U fractionation resulting from alpha decay relates to recoil of 23“Th across a solid-liquid phase boundary. Alpha decay of 0 238U 200-500 A from such a boundary results in a recoil sufficiently strong to propel the 23(‘Th atom across the boundary, which then decays to 23“ 234 U producing an excess of U in the waters (Kigoshi, 1971; Cowart and Osmond, 1977). Residence time of the waters within a formation is of importance here, because the amount of 23" 238 Th produced in the waters will be related to the decay rate of 234 U. Fast moving waters will therefore not collect as much Th as will slower 234 [238 moving or confined waters and which may have U U ratios as high as 15 (Cowart and Osmond, 1977). Residence time and the degree of weathering will also affect the fractionation of uranium during the normal weathering and leaching processes. Syromyatnikov and Tolmachev (1962) reported a direct correlation between the uranium activity ratio and an increase in uranium from disseminated uranium in various rocks. This is to be expected, because, as weathering increases, more decay produced uranium will come into contact with the water. Continued removal of 2340 will leave the weathered material depleted in 23(“U producing a 234 238 U/ U ratio less than unity. Such a case has been found in the weathered zone of the Conway granite in New Hampshire (Cowart and Osmond, 1977). 11 Uranium may be removed from solution by a number of means and under a variety of conditions. Changes in solubility correlated with changes in Pco2 (see trends reported by Hostetler and Carrels, 1962), changes in salinity of the waters, or changes 'in Eh-pH related parameters can all cause direct precipitation of uranium bearing phases. Evaporation leading to an supersaturation of uranium in solution can also result in a direct precipitation of uranium, a process especially applicable to arid environments (Dall'Aglio, 1974). Uranium can also be removed from solution through dissociation of the U-bearing complexes under acid-reducing conditions, and resultant cation exchange onto clay materials, through absorbtion onto organic materials (Szalay, 1964), and through co-precipitation with other mineral phases (Hostetler and Carrels, 1962). Uranium precipitated from solution will have the same uranium isotopic ratio as the 'parent' water. Due to the extremely small mass difference between 234 238 U and U, fractionation is not temperature dependent as it is for the light stable isotopes, such as carbon or oxygen. Thus, differences which occur between the isotope ratios of U waters and a deposit must be the result of other processes. For preexisting deposits, changes in the isotope ratios will result if the system is Open to isotope migration. This usually occurs through a removal of 234 234 238 U and results in a decrease of the U/ U ratio uranium enriched in concomitant with an increase the U ratio. This results in 'apparent' 230 ages which are older than the true age of the deposit or an excess of Th such that it is impossible to calculate an age of deposition. If uranium enriched in 234U is brought into a deposit, the opposite effect will be produced, resulting in 234 238 230 234 higher U/ U ratios, lower Th/ U ratios, and younger 'apparent' ages. Analysis of a suite of samples from one area of a deposit often can establish the 12 presence of isotope migration, usually by identifying unsupported daughter products. Ages calculated from areas subject to isotope migration, should however, be viewed with extreme caution. The initial uranium ratios will also change through the decay of excess 234U toward equilibrium, resulting in a lowerZBQU/238U ratio. Changes resulting from isotope migration will be superimposed on the ratios resulting from the decay of excess 234U. Identification of uranium isotope migration only on the basis of uranium and thorium isotope ratios is difficult because not all migrations result in distinct anomalies. It is useful, therefore, to employ when possible, a third isotope, 226 226 230 Ra, in identifying migration patterns. Ra is the daughter product of Th 226 and has a half-life of 1622 years. Chemically, Ra behaves differently than 226 either thorium or uranium, although because of it's low abundance in water, Ra will remain dissolved (mobile) in natural waters of almost any composition. 226 (Levinson and Coetzee, 1977). Due to its short half-life, Ra should be in equilibrium with 230 Th within 10,000 to 12,000 years of deposition. Deviations from the equilibrium value for a deposit older than 10,000 years B.P. point to either a movement of radium or uranium. GEOCHRONOLOGY The 230Th/234 U disequilibrium dating technique is based upon the radio- active decay law governing the formation of a 'daughter' from a 'parent' radionuclide. The assumption is made that, over a given period of time, a fixed amount of one nuclide will be formed by the radioactive decay of another and thus must be formed at a constant rate according to the expression: 13 P N : N e (l) where N: is the number of atoms present at time (t) and N: represents the number of atoms initially present. The decay constant, Aexpresses the probability of a decay occurring within a given period of time. If, however, the daughter nuclide is itself unstable and undergoing radioactive decay, the general expression describing the parent-daughter relationship at some elasped time (t) will be of the form: p t t _ t d >~ N: (e- )\d _e->.p) ”I: 8 Ad (2) where the subscripts 'p' and 'd' represent respective amounts of parent and daughter nuclides. The first group of terms represents the growth of the daughter nuclide from the parent and the decay of the daughter atoms; the last term gives the contribution at any time from the daughter initially present (Friedlander et al., 1955). 238 In the U series, the half-lives of the three major nuclides of interest to 238U, 234U’ and 230 238 a Pleistocene geochronology, Th are 4.51 x 109 years for 234 U: 2.47 x 105 years for U and 7.8 x 10 years for 230Th (USAEC Chart of the Nuclides, I970). Measurment of all three nuclides is necessary to calculate an age as disequilibrium within the series is common in near-surface environments. In this case the decay equation is of the form: 9.230t A230 - t [2323‘ t = fl-e )+ ( ) (1 e—(A 230 A234) ) (3) 234 U t A230 7(234 238 U 14 When dealing with radioactive nuclides in geological samples, it is seldom possible to actually measure the number of atoms of a particular isotope of interest because of the low absolute abundances of the daughter nuclides. Instead, activity, i.e. decay per unit time, is measured. Ratios of the activities are then used in the decay equation to calculate an age. Equation 3 is based on 230 234U and 234 238 measurment of Th/ U/ was no 230Th initially present. This equation also takes into account any 234 238 230 U activity ratios and assumes that there disequilibrium between U and U, which will affect the amount of Th present (Broecker, 1963). Ages calculated from equation 3, in order to be considered valid, must meet certain criteria. These are: (1) There must be sufficient uranium and thorium present in the samples to provide accurate measurments of activities. This is not generally a problem for uranium ores, as alpha spectrometric techniques are capable of accurately measuring amounts of uranium as small as .05 ppm (Gascoyne, 1977). However, because of the extremely small amounts of thorium present in most samples, measurement of 230 Th activity can present difficulties in samples which are younger than 10,000 years unless uranium concentrations are high. Thus samples with very low activities may have large uncertainties in age. (2) Ages are calculated assuming there is no thorium initially present in the system. Although thorium is insoluble under near—surface conditions and thus not present with uranium co-precepitated from a carbonate or sulfate solution or formed as a uranium mineral, contamination may result if 15 the deposit was formed containing a large amount of detrital material. Thorium readily adsorbs onto the surface of clay materials and is primarily 230 [232 transported as a clastic component. Measurment of the Th Th activity ratio will however give an indication of the amount, if any, of a detrital component present, because detrital 230 232 230 Th will always be acco- /232 mpanied by 'common' thorium, Th. Th Th ratios greater than about 20 indicate the absense of detrital thorium. Low 230Th/232Th ratios indicate the possibility of detrital thorium, therefore any calculated age will be a maximum age. (3) Also inherent to age calculations is the assumption that the system has been closed to isotope migration, either into or out of the system, since the time of deposition. Young samples will naturally show some disequilibrium, but in a closed system, isotope ratios for a group of samples should all be close to the same value. If isotope migration is known to have occured, calculated ages are only 'apparent' ages. (4) Depostition of the uranium must have occured within a relatively short period of time in relation to the half-lives of the isotopes, otherwise, the system must be considered 'open'. METHOD Isotope separation and chemical purification of the radioelements was accomplished using techniques developed by Thompson (1973) and modified for the present study. Below is a brief outline of the detailed procedure found in Appendix A. 16 Uranium-bearing sediments were dissolved first in HF followed by HNO 228Th/232 3 U spike, until all material was digested. Following addition of one ml of the radioelements uranium and thorium were co-precipitated with Fe in the form Fe(OH)3. The precipitate was dissolved in 9N HCL and the iron removed by extraction into iSOpropyl ether. U and Th are quantitively separated by passing the solution through anion exchange resin conditioned in chloride form (CL'). Thorium is separated from interfering cations by anion exchange onto resin conditioned with a 10:1 mixture of methanol and nitric acid. Separately, U and Th are further purified by formation of TTA complexes and extraction into benzine. The organic phase containing the radioisotope is then evaporated onto a stainless steel planchet just prior to counting. Activities of 238u, 234g, 23011,, and 232 Th were measured using an Ortec 6240A multichannel analyizer and silicon depleted surface-barrier dector system. The total number of counts (one count = one alpha decay event) under each peak were summed and divided by the count time, resulting in count rates for each isotope. The count rates were corrected for background activity and processed using a computer program developed by Thompson (1973), which calculated isotOpe 230Th/234U age. activities, activity ratios, uranium concentrations and a Uncertainties in the age determinations are assigned based upon one standard deviation of the counting statistics. (For a review of the data processing and precision associated with this program, see Gascoyne, 1977). 226 Ra analyses reported in the following section were performed at the University of Calgary by Professor A.A. Levinson. 17 RESULTS AND INTERPRETATION 1. SOUTHERN AFRICA DEPOSIT "K" The eight samples from "Deposit "K" are from an extremely arid area of southern Africa which has a mean annual rainfall of approximately 55 mm per year. Uranium mineralization is associated with a 1.5 meter thickness of diatomaceous earths, carbonaceous sands, silts and clays. These lacustrine sediments were deposited in an impeded drainage channel about 600 meters wide and some 5 km long, which is itself cut into a broad sand-filled vailey several kilometers wide, draining an area of about 15,000 sq. km. The unconsolidated uranium-bearing sediments have the grey-green and yellow colors indicative of a reducing environment and stand in marked contrast to the red aeolian sands of the host valley. Overlying the sediments and the uranium deposit is a thin discontinuous layer of calcrete which in turn is partially concealed by recent windblown sand. X-ray diffraction and microscope examination has identified the uranium minerals camotite (K2(UOZ)2V208.H20), boltwoodite, (K(H30)UOZ(SiOa).nH20), and zippeite, (2UOBSOB.4HZO). As these minerals account for only a small portion of the total uranium present, it appears that a majority is adsorbed as uranium cations onto the surface of clay particles, carbonaceous material and organic matter present in the deposit. The source of the uranium is uncertain, but it is thought to have been initially derived from abundant granites and pegmatites surrounding the area, where values up to 50 ppm have been found. 18 From stratigraphic correlation of the cross-sections of the four pits in Figure 1, it is observed that the uranium mineralization cross-cuts the major lithologies rather than being confined to particular horizon. Areal distributions of the pits as well as the locations of the samples within the stratigraphic units are shown in Figure 2. Isotopic activity ratios, uranium concentrations, and calculated ages are presented in Tables 1 and 2. An inspection of the data in the tables reveals several important points: 230 232 1 Th/ Th ratios are sufficiently high, with the exception of sample 579, to indicate that relatively minor amounts of detrital thorium are present in association with the uranium. 234 [238 2. Initial U U ratios exhibit only slight variations, having a standard deviation of .048, possibly indicating that the suite of samples are genetically related, i.e. derived from a common parent. If multiple source areas were involved, a greater variation in the 234 238 intial ratios might be expected. The U/ U ratios indicate slight enrichment of the waters in 23 4 234 U , with no large scale post- depositional migration of U having taken place. 3. Ages calculated on the basis of the isotOpe ratios are maximum ages and indicate that the deposit is geologically young, not more than about 50,000 years old. 226 4. Results of the Ra analysis indicate some degree of isotope 226 migration in three of the four sample pits. Ra data also helps 19 358 W 528 " II I II I I z I IIII II I III III II' 3 IIIII IIII'IIIIIIII II' IIIIIIIII'I IIIIIIIIII III . .1,IIIIII.I.IIII.I I'm. II. 419m asl 387W I‘IIIIIII| I .IiIIIIIIIIII I IIIIIII I:II X X I X X Figure 1 Stratigraphic Correlation - Deposit "K" 20 83mm >:>_.Ho< 330m— ccm c0380.— oEEmm ozu¢u-m>_oo mm“ azm¢u I at a: a: .........u.. Hm“ oz<4u maomum¢u-zzoam In «x Vega: o.n\_n.\on._ I up. .. 2a: 2.: :3 2x2. RSI >mmo-u>_4o aaaazcns. ozu¢u > 98: 88 m 80.2 a 8. m n: 8. m 84 so. m an. ah 8n + 80.: an S. + N: S. + 24 so. + 62. 320?? 3a 82 m 25$ 2 S. m 84 S. m £4 NS. m RN. S“ 83 + 98.x: 8 3. + 24 8. + 24 ”8. + no. 2033?: ”R as M So.» an s. m 2; S. m :4 3c. M :0. 325m 3n oooo + con.zn om_ No. + uz.z do. + s_.z sac. + «an. nun 83 m 80.9. § 8. m a: 8. M £4 one. m 6:. 33m Sn coma + ooo.an mnz _o. + uz.z so. + nz.z moo. + Non. awn Ed 38: .53 :3. H 2mm . PR .2 A .: .~ 2 c A a c TflIIc .02 83328 RN am am RN 0353. mm0< QMH.:>E.U< map—.8— .mZO_._.50m m0 ZOw~m( 225m ) 238U 234U 238U (234 2. URANIUM ACCUMULATION OF INTERMEDIATE AGE (10,000 - 400,000 years) 234U 230 226 U) > (——-— “I ————)g I—E‘L) 238U 234U 238U ( 3. URANIUM ACCUMULATION OF OLD AGE (>400,000 years) 234 230 226 ( U )g (——I-I‘-—) ; I—B-Li 238U 234U 238U FIGURE 3 Relative Activity Ratios in relation to the age of Uranium accumulation 25 uranium from the diatomaceous earth into the sand horizon, thus resetting the 'clock' and producing an observed age of 8,000 years B.P. This is supported by the 230 234 Th/ U ratio of .38 in sample 585 which indicates a uranium loss, relative to the undisturbed samples of pit 358W, i.e. higher than .31. As the uranium ratios are very close, fractionation of uranium during the migration was mininal. The small amount of thorium produced by decay over this short period has also 230 232 resulted in a lower Th/ 226 a /238 Th ratio relative to sample 585. The equivalent R U ratios observed in both horizons and which are lower than those in pit 226 358W suggest that either Ra was present in both horizons when the uranium migrated downward, then left the system at some later time, or alternatively, 226Ra may have moved downward from the area of sample 585 after uranium 226 238 mineralization. This latter effect would decrease the Ra/ 226 a [238 U ratio of sample 585, while at the same time, increasing the R U ratio in sample 581 above the equilibrium value it should have in a system 8,000 years old. Thus the latter alternative appears to be the most likely for the situation under consideration. In pit 525, a more complex isotope migration pattern is observed (Figure 2). The stratigraphically lower unit, sample 579, is a clear example of uranium 230Th/234 removal resulting in a U ratio of .51, a value significantly greater than the undistrubed value of .31 (pit 358W). The low 230 232 230 Th/ Th ratio in this sample indicates the possibility of some detrital Th contributing to the observed 230 /234 226 a [238 Th U ratio. The high R 226 U ratio can be attributed both to the loss of uranium, plus the addition of Ra, although not necessarily at the same time. 230 234 Stratigraphically above sample 579, is sample 582 with a Th/ U ratio of .13. This low ratio indicates a post-depositional migration of uranium, possibly either from the lower horizon or the result of lateral movements of ground water. The 226 a /238 R U ratio of .29 is then greater than an equilibrium value of .13 and 26 226 226 indicates an addition of Ra, in agreement with the Ra addition noted in sample 579. The difference in the uranium ratios of the two horizons may be related to fractionation early in the deposits history, but more likely it is due to 230 234 the remobilization which resulted in the observed Th/ U ratios. Approximately 500 meters north from the other three pits, is pit 470N. This pit is difficult to correlate with the others (Figure l), as it is composed of layers of clay, sandwiched between two thin sand units and contains no diatomaceous earth horizon. Samples 578 (upper) and 580 (lower) show isotopic 230 234 Th/ U ratio of .64 234 variations similar to those in pits 387W and 525. The high U) from the 238 for sample 578 indicates a loss of uranium (possibly enriched in 226 immediate area. This interpretation is supported by the high Ra/ U ratio for that sample, also indicating a loss of uranium as well as a possible addition of 226 234 Ra. Sample 580, with a 230Th/ U ratio of .26 indicates that within this pit, also there has been a remobilization and deposition of uranium some time after 226 a [238 the originial deposition thus producing the younger age. The R U ratio of .79 is consistant with the addition of 226 Ra observed in sample 578 of this pit. The similarity in the uranium isotope ratios for both samples could be either the result of chance or due to the fact that uranium isot0pe fractionation did not occur during the remobilization. Based upon the available geological evidence and results of the isotopic analysis, a tentative history of Deposit "K" can be formulated. During a pluvial period about 40,000 years ago the organic-rich lacustrine sediments were mineralized as 23" U-enriched uranium was stripped from ground waters moving laterally through the carbonaceous sediments; both by changes in the oxidation potential and ion exchange onto the clays. Shortly after deposition and before the 27 accumulation of significant daughter products, a small amount of isotopic fractionation and uranium migration may have taken place, resulting in different uranium isotope ratios between samples. These early migrations may have been associated with a lowering of the water table near the end of the pluvial period. Further ground water movements during a more recent pluvial period approx- imately 8,000 years ago resulted in localized movements of uranium and radium with the exception of pit 358W, which notably is capped by a layer of calcrete. 230Th/234 Different U ratios in all of the pits indicate that other local uranium migrations may have occurred at later intervals but without further sampling no firm conclusions can be reached. 2. YEELIRRIE, WESTERN AUSTRALIA Located in a semi-arid region of Western Australia, the Yeelirrie uranium deposit is found in an impeded drainage channel which has been incised into a Cretacous plateau during Miocene or Pliocene time. Following the onset of arid conditions, the drainage channel became choked with sediments, finally resulting in a series of clay pans and salt lakes which now characterize that part of the state. Except for a narrow strip of Archaean greenstone along the western edge of the basin, the catchment area for the system is solely within the granitic terrain to the northeast. Based upon close-grid diamond drilling and airborne radiometric surveys, a general outline of the area of mineralization has been identified (Figures 4 and 5). Mineralization occurs over an area 6 kilometers in length and .5 kilometers in width and to an average depth of 8 meters. Three distinct, but gradational stratigraphic layers have also been identified from the drilling: (l) the over- burden, composed of loam and carbonated loam, (2) the calcrete and transition 28 chtQ 95:55 :0 comma :moaoo 9.0 of Ho 053.30 can 5380.. 295% a 9:3”— / / x a as. o / Ron.“ ‘ _ Oman—NO , o 0 «gen hog-ON .— / .4 .\ i a \ _ . z I _ I, . xx _ I I II II I I—I I I] l I III ‘1 I’ll II I, IIIIIIII / I l. IIIIIIIIIIIIIIIIII I II’] x I z A. “ mm 29 >o>5w otSEEcmm E0: oft—om; «o @5330 n ocawE / 091/ 66 a .xbmoz INHIHI n o 000 .nm. ”— 23m r. a o c. 33.? 52:00 mm 30 calcrete, and (3) the clay-quartz unit, composed of clay-quartz and carbonated clay-quartz. Gypsum and celestite also occur in the overburden, along with calcite, but are not restricted to it. The calcrete layer contains both calcite and dolomite as dominant forms of carbonate, with calcite being more abundant in the upper transition zone and dolomite being more abundant in the calcrete proper. Silica and montmorillonite are also found in the calcrete, resulting in a large degree of variability, ranging from a white, hard, porcellaneous carbonate to a soft friable form. The clay-quartz unit is composed predominantly of quartz and kaolinite. Uranium mineralization occurs primarily in the calcrete unit, both as coatings on cavity walls in the porcellaneous calcrete and as uranium dispersed throughout the earthy calcrete. It also occurs as grain coatings and dissemina- tions in much of the clay-quartz as well as linings on fractures and small faults in all lithologies. Only minor amounts of clay and silica within the calcrete are demonstratably later than the uranium mineralization, indicating that the uranium is secondary and not associated with elastic deposition of the sediments. X-ray diffraction has identified carnotite as the only uranium mineral present. Both ground radiometric surveys and laboratory analysis indicate that no thorium is present in the deposit. The quantity of ore in the deposit is estimated to be over 30 million tons with an average grade of .1596, resulting in over 46,000 toms of U308 (Western Mining Corp., 1975). Yeelirrie and surrounding areas receive an average of 20 cm of rainfall per year, usually in the form of high intensity storms, while at the same time having an evaporation rate of approximately 250 cm per year. Ground water flow begins at the granite breakaways, flows through the peidmont and alluvial plain, and into 31 the calcrete blocked drainage channel (Figure 6). Present estimates indicate the water table in the calcrete is at a depth of 5-6 meters (Western Mining Corp., 1975). Tests from one excavation in the channel indicate an average transmibility of 55,000 imperial gal./day/ft., producing a yield of approximately one million imperial gal./day. Preliminary surveys of water salinity indicate less than 750 ppm TDS in the channel near the breakaways, increasing to 5000 ppm on the edge of the calcrete, and rising to over 20,000 ppm in the ore zone (Western Mining Corp., 1975). While tests of uranium concentrations in the water are limited, early figures from boreholes find values greater than 50 ppb and as high as 450 ppb. Analysis for potassium and vanadium are not available. The eight Australian samples analyized were collected from an area near the center of the ore body (Figure 4). An inspection of the data presented in Table 3 indicates some of the trends associated with the isotOpe ratios: 230 /232 1 Th Th ratios are high in all of the samples, with the exception of 212970, which has a lower but still acceptable ratio. Combined with data from the company surveys, these ratios confirm that only thorium produced from radioactive decay is present in the ore body. 230 [234 2 Th U ratios in all but two of the samples are greater than unity indicating a post-depositional loss of uranium. The range of ratios observed 234 may indicate differing amounts of U loss, different ages for each sample, or both. Emmm omemcC 2:22; 9:. no 2205 .mboBfiEEooU IHIHI to> conun— IIIIHIHI 600.00— .— 3.3.0: w 2sz Zoom. 0.5 I :c__omv.fllIII_ 3:55 E 532:2! ocoN o_ 30.6.3 2 oficmcu comoaeoooa a comic—mum + + + + + + + + + + + + + .+ I TI] 1.. + . + + +\.,\_,.,.,,..Yf + + . + + + +. + + + .+ t\u.%;~r.hfl.lkx,d. +. + + + + + + + + .\cw\,uI\I:. i/./W%.ll+ + + + + + + xoOLcom cococumozE: + + + + +++ x09. com comoaeoooo I I) (I + + . .+ I /.\ \\/\U\ \Ilyu? o__m0c¢ ou_coum4 wimp/Zn. o>:_mcouc_ oco ocms_uoa c_m_a _m_>:__< .mccmgu .r c. .r ._. DE.U< map—.09 fiZOCkMHZmUZOU SAD—243:.— n 033. 34 23‘} 238 3. U/ U ratios of the samples are all greater than unity. The implications are that (1) initial uranium ratios were very high and a 23‘! 234 238 U/ U ratios to 231! preferential loss of U was insufficient to reduce the values below unity, or (2) there was little or nor preferential loss of 234 238 U, instead a non-fractionated loss of both U and 230 [234U ratios and 23’4U/238 U occurred resulting in Th U ratios both being greater than unity. 230 4. Assuming that no Th migration has taken place, the two ages calculated can be considered maximum ages, thus allowing for any loss of 234U. Although two ages were calculated, it is not possible to actually determine 230Th/234 the time of mineralization of the deposit as a whole, as the U ratios are larger than unity for six of the eight samples and indicate that open system conditions have prevailed and thus a "true" age of deposition cannot be calculated. While loss of uranium from most of the samples is indicated by the 230Th/ZBI‘U ratios, there is a possibility that uranium may have been added to 230Th/234 some of the samples, (212970, 205002), thus lowering the U ratios and producing 'apparent' rather than true ages. The formation of the uranium deposit at Yeelirrie appears to be related to the strong evaporitic conditions, resulting in supersaturation and precipitation from solution of uranium, potassium and vanadium (Dall'Aglio, 1974). The original source area from which 23“ U-enriched uranium, vanadium and potassium, were leached is evidently the surrounding granitic rocks and greenstones. The present deposit may have formed through a multi—stage accumulation process from previous uranium deposits, (Grunner 1956, Rosholt, 1961), or it could be the result 35 of a single-stage accumulation from the granitic source area. The mobility of uranium and the evidence of recent uranium migrations within the present ore body tend to support a multi-stage accumulation process. The presence of a fluctuating water table plus the high evaporation rate and oxidizing conditions readily lend themselves to uranium migration within and out of the deposit. Post- depositional migrations of uranium apparently have not resulted in significant 234 230Th/23ll fractionation of U ratios and all of the 234‘ /238 U as the majority of the U U ratios are greater than unity. This could result from the fact that in carnotite both uranium isotOpes are already in the 6+ oxidation state, thus Preventing preferential oxidation and removal of 234 23‘} 238 U. While alpha recoil can significantly change the U/ U ratio in the liquid phase (Cowart and Osmond, 1977), the ratio in the solid phase will be relatively unchanged, especially in area of higher concentration. It is hoped that when the 226 Ra data becomes available, more definate statements can be made about the extent of recent uranium migrations. 3. KELOWNA, BRITISH COLUMBIA The third group of uranium samples analyized are from the Kelowna area of south-central British Columbia, which presently, has a temperate, humid environ- ment. Uranium mineralization in the area is associated with organic-rich sediments near the contact zone between the unconsolidated sediments and underlying granitic rock. In some areas, the deposit is presently overlain by a basalt caprock. An idealized section of this uranium deposit is shown in Figure 7. The flood basalts which overlie the sediments are thought to act as a relatively impermeable caprock, protecting the mineralized sediments from downward percolating waters. 36 2323. Ho mtmoaoo 62:95 on»... 6me yo wESom 05 wEBocméotoom poi—moc— m oSwE xuomoum fizmzamm 8:338:82: @ ® 55% 352: ® :52: 53.: no O O O zo;.:>:.U< map—.09 .mZOEkaZm—Uzoo SSE/5&3 a 2an 39 ZBQU-enriched U/238U ratios basalt cover, it is not suprising that there has been removal of 230 234 231} uranium resulting in the relatively high Th/ U and low observed. The single sample from Okanagan Falls Road was taken from a conglomerate also exposed in a roadcut not covered by the basalt cap. The very high 230Th/ZMU 234 231} 238 U/ I233 ratio indicates a substantial loss of U, while the high U ratio 23“ U ratio. indicates either a bulk removal of uranium, or a very high initial U Without more samples and data, little can be said to explain the low uranium ratios observed in five of the six samples, from Kelowna, other than that they 234 could be the result of low uranium ratios in the water, leaching of U, or a combination of both. CONCLUSIONS The results represent samples from Africa, North America and Australia each reflecting a different geologic and chemical environment. Deposit "K" in southern Africa, consists of a uranium deposit formed by ground water migrating downdip through carbonaceous sands, clays and organic trash pockets (diatomaceous earth). The deposit formed as a result of changes in the oxidation potential resulting in precipitation of uranium from solution and cation exchange of uranium onto favorable material. Isot0pic analysis of eight samples show that the deposit was formed about 40,000 years ago. Post- depositional migration of uranium most likely in response to water table #0 fluctuations, was shown to have occurred as recently as 8,000 years B.P. and a possibility exists that other migrations may have occurred previous to that. The second uranium deposit, Yeelirrie, in Western Australia, consists of uranium mineralization in association with oxidized calcrete channel sediments. The deposit is thought to have formed through evaporation of groundwater, resulting in a concentration of uranium, potassium and vanadium and other salts in solution leading to the precipitation of carnotite. Isotopic analysis of eight samples from this deposit indicate significant uranium isotope migration. Six out 230Th/234 of eight U ratios are greater than unity, allowing only two possible ages to be calculated. Evidence of uranium loss in the system indicate that the ages 261,000 and 137,000 years are maximum ages and represent areas of local uranium mineralization equal to or younger than those ages. Due to the extent of uranium migration noted these calculated ages cannot be considered reliable and do not reflect the age of the deposit as a whole. Fluctuations in the water table, presently at a depth of 5-6 meters is thought to be responsible for post- depositional uranium migration. Kelowna, British Columbia, the site of the third deposit, has a humid climate, in contrast to the extremely arid climates of the two previous deposits. The uranium was deposited from solution under chemically favorable conditions associated with organic-rich sediments which in some instances are covered by flood basalts and which overly granitic basement rocks. IsotOpic analysis of three samples from Lassie Lake indicate a maximum age of mineralization locally of 230 23l‘U ratio indicates that a 224,000 years B.P. About 110,000 years ago the Th/ remobilization of uranium took place resulting in a minimum age for the deposit. Single samples from Hydraulic Lake and Okanagan Falls Rd. and two from Fuki, 41 230 [234 all show varying degrees of isotope migration resulting in Th U ratios greater than unity, and require additional sampling before more definate conclusions can be reached about the age of each deposit. The conclusions reached based on this preliminary study are that surficial uranium deposits of Late Pleistocene age have formed economic concentrations under both oxidizing and reducing conditions in climates ranging from humid to extremely arid. Once formed, environmental and chemical changes can lead to removal and relocation of uranium into, through, and out of a deposit. It has been shown that uranium accumulations and migrations have occurred during Pleisto- cene and Recent times and that unless the deposit is sealed from further interactions with ground water it will function as an open system resulting in anomalous isotope ratios, unsupported decay products and uranium removal or redeposition. It is felt that if preliminary study indicates an open system, as at Yeelirrie, much more isotope analysis is needed to establish an understanding of the systematics of uranium movement. While uranium migration occurred in Deposit"l<", use of 226 Ra data not available for the other areas clearly established that one pit had undergone no post-depositional migration and thus presented a valid age for the deposit as a whole. The broad conclusions reached regarding U-series disequilibrium and surficial uranium deposits are that under favorable conditions, it is possible to calculate an age, or range of ages of uranium mineralization. When conditions are not favorable for an age calculation, isotope disequilibrium can result in interpretation of uranium migrations and indicate periods of uranium movement. APPENDIX #2 APPENDIX A ANALYTICAL PROCEDURE A. DISSOLUTION AND PRIMARY PRECIPITATION STEPS l. 2. Crush the sample to a fine powder; approximately 300-400 mesh. The amount of sample used depends upon the concentration of uranium in the ore. For most ores, one gram is sufficient. Samples which have a known concentration require an amount sufficient to provide 80-100 mgr. of seperated uranium. The dissolution technique is dependent upon the composition of the ore. Originally, samples were dissolved in a mixture of HF + H250“, but this was later abandoned in favor of hot HF, followed by treatment with concentrated HNOB. Fifty mililiters of HF were used for every 0.5 gram of ore material. The samples are placed in teflon beakers with teflon covers and heated to just below boiling, for an 8—12 hour period. Samples which were dissolved after this period were evaporated to complete dryness to drive off flourine. Fifty mls of concentrated HNO3 was added, the beaker covered and heated until the residue was completely dissolved. Occasionally, a small amount of HF was added, which necessatated evaporation to dryness again, followed by another treatment with HNOB. Samples which did not initially dissolve in HF were fumed again for an additional 0-6 hours and then evaporated to dryness, treated with concentrated HNO3 and fumed for 2 hours. These were evaporated to dryness and redissolved in concentrated HNO3 if any residue 7 remained at this point, the above steps were repeated. #0 7. B. 43 The nitric acid is then evaporated to a volume of 50 ml and placed in a graduated cylinder. The beaker is rinsed with a small amount of HNO3 which is added to the solution raising the volume to 65 mls. Place the solution in a large beaker and dilute to 500 mls with distilled water, forming a 2N nitric acid solution. The high uranium activity of uranium ore samples requires that one mililiter of spike (25.5 ug/l) be added to the solution, along with one ml of iron chloride solution (FeClB). Samples were then stirred for a short time either with a glass rod or magnetic stirrer then allowed to equilibrate for an 18-24 hour period. While stirring the solution, concentrated ammonium hydroxide is slowly added to the solution, until a reddish-brown precipitate forms, usually at a pH between 6 and 7. After floculation and settling of the precipitate, it is separated from the solution by filtering with Whatman #1 filter paper and rinsing with distilled water . IRON CARRIER REMOVAL BY ISOPROPYL ETHER EXTRACTION Place the funnel containing the filter paper over a vycor beaker, and dissolve the filtrate using about 50 mls of 9N HCL. Rinse the filter paper with 9N HCL to ensure complete dissolution of all of the precipitate. About 10 mls of concentrated HCL is added to the solution to return the solution to 9N. Removal of iron is effected by adding an equal volume of isopropyl ether to the solution in a seperatory funnel. This is shaken vigorously, for about a minute, stopping periodically to release the vapor pressure. After allowing the phases to separate, drain the bottom layer containing the uranium and 44 thorium into the vycor beaker. The yellow ether layer containing the iron is discarded. Repeat the extraction until the yellow color disappears and the ether becomes colorless, usually about three extractions. 10. Gently heat the acid-ether solution to boil off dissolved ether; until cloudiness dissappears and the acid phase is clear. C. SEPERATION OF URANIUM AND THORIUM ISOTOPES BY ION EXCHANGE ll. 12. 13. ll}. RESIN When the solution has cooled, it is placed on an anion-exchange resin column, which has been preconditioned with 50 mls of 9N HCL. Rinse the beaker with 9N HCL, also adding this to the column. Adjust the column to allow a drip rate of about 50 ml/hour. Once the solution has passed through, the column is rinsed with 100 mls of 9N HCL, and collected in the same vycor beaker. This beaker now contains the thorium, while the uranium has been adsorbed onto the resin. Uranium is eluted into another vycor beaker by rinsing the column with 100 mls of 0.1N HCL. Evaporate both solutions to complete dryness, on low heat. The uranium is now ready for plating and counting, while the thorium must be purified further. In order to separate thorium, prepare another column of anion-exchange resin, by conditioning the resin with 50 mls of a 9096 methanol-acid solution (45 mls of methanol and 5 mls of 5N HNO3) (Tera et. al., 1961). Convert the thorium residue to nitrate salts by dissolving it in 10 mls of 8N HNOB, followed by evaporation to dryness. Redissolve the residue in 10 mls of 5N HNO3 and dilute to 100 mls with 90 mls of methanol. When conditioning of 15. 45 the resin is complete, add the solution containing the thorium and allow to flow through the column at the rate of 50 mls/hour. Following this, rinse the column with 50 mls of the 90% solution. The rinse may be discarded, as the thorium is adsorbed onto the column. Thorium is eluted from the column by adding 100 mls of 1N I-INO3 and allowing the solution to drip into a vycor beaker. Once the elution is completed, slowly evaporate to dryness, removing the beaker from the stove just as it reaches dryness. If the thorium is allowed to heat beyond this stage, it tends to become insoluble, thereby interfering with the following procedures. D. FINAL PURIFICATION BY SOLVENT EXTRACTION. URANIUM EXTRACTION 16. 17. Examine the residue in the uranium beaker, if it has a yellow-brown or dark brown color, substantial amounts of iron, are present which will interfere with the solvent extraction. To remove the iron, dissolve the residue in 34 mls of 9N HCL, place the solution in a test tube and add an equal volume of isopropyl ether. Mix the phases thoroughly and allow to separate, removing and discarding the ether phase. Repeat until the ether is colorless. Remove the acid into the beaker and evaporate to dryness. Dissolve the residue in 5-7 mls of O.1N HNOB, heating gently until all of the residue is in solution. Adjust the pH of the acid to 1.2 and place it into a test tube. To this, add one ml of 0.2 TTA (25 grams of 2- Thenoyltrifluoroacetone dissolved in 500 mls of benzine) and mix for one minute. 18. 19. 20. 21. 22. 23. #6 Centrifuge to completely separate the phases, then remove the layer of TTA and discard it. This step removes any thorium or protactinium which may have been present. Transfer the acid phase to a clean test tube and raise the pH to 3.5 by dropwise addition of 0.3N NH OH. Add 2 mls of the TTA solution and mix 4 for one minute. Centrifuge to separate the phases, and remove the TTA layer, containing the uranium, placing it into a 10 ml micro-beaker. Repeat the extraction with one ml of TTA and add it to the micro-beaker. A dark red color in the TTA indicates the presence of iron, a light red color the presence of much less iron, usually not enough to interfere with the spectrum. A bright yellow color to the TTA indicates a large concentration of uranium, the brighter the color the higher the concentration. In this case, only a portion of the TTA is used, to avoid a thick source which will produce large tails on the spectrum. Slowly evaporate the TTA solution, reducing it to a volume of approxi- mately 0.25 ml. Further evaporation will cause crystalization, which can be remedied by adding more TTA and heating. Remove the TTA from the beaker with a disposable pipette. Slowly drip the solution onto the center of a hot stainless steel planchet and allow it to evaporate in concentric rings. Flame the planchet to red heat for about 10 seconds, thereby removing any 210 volatile Po which could interfere with the uranium spectrum. Count the disc on an alpha spectrometer immediately. 47 THORIUM EXTRACTION 2“. 25. 26. 27. Dissolve the thorium residue in 5-7 mls of O.1N HNO3 and heat gently to dissolve all of the residue. If the residue was on the stove for a long period after dryness, this may first necessitate a dissolution with a few mls of 8N HNO3, followed by evaporation just to the point of dryness, then followed by the O.lN HNOB. Adjust the pH of the acid to 1.2, with the addition of small amounts of O.3N NHl‘OH. To the acid, add 2 mls to TTA and mix for one minute. Centrifuge to separate the phases and transfer the TTA phase, with the thorium, to a 10 m1 micro-beaker. Repeat the extraction using on ml of TTA and add to the micro-beaker. Evaporate the TTA solution to a volume of approximately 0.25 mls and plate onto a planchet as directed above. Flame the disc for a few seconds and then count immediately on an alpha spectrometer. NOTES: 1. During the purification and extraction process, rinse all glassware with distilled water or the appropriate acid and combine with the solution to ensure the highest possible yields. Wash all glassware in hot water, using a phosphate-free soap, followed by a wash with 8N HNO3, another wash with soap and water, then a rinse with hot water followed by a rinse with 8N HNO3 and completed by a rinse with distilled water. Vycor beakers are soaked in a 1:1 solution of nitric acid and then washed as in step 2. LIST OF REFERENCES LIST OF REFERENCES Becking Bass, L.G.M., Kaplan, I.R., Moore, D., 1960, Limits of the natural enviromment in terms of pH and oxidation - reduction potentials. J. of Geology 68: 243-284. Broecker, W.S., 1963, A preliminary evaluation of uranium series inequilibrium as a tool for absolute age measurement on marine carbonates. J. Geophys. Res. 68: 2817-34. Cherdyntsev, V.V., 1971, Uranium - 234. Jerusalem: Israel Program for Scientific Translation, 234 pp. Dall' Aglio, M., 1974, Geochemical exploration for uranium. Uranium Exploration MethOdS, IOAOEOAO Panel PFOC. sero 189-2080 Dement'yev, V.S., Syronyatnikov, N.G. 1965, The mode of occurrance of thorum isotopes in ground water. Geochem. Int. 2: 141-147. Dooley, J.R., Tatsumoto, M., Rosholt, J.N., 1964, Radioactive disequilibrium studies of roll features, Shirley, Basin, Wyoming. Econ. Geolgy.59: 586595. Friedlander, G., Kennedy, J.W., Miller, J.M., 1966, Nuclear and Radiochemistry New York: John Wiley 6: Sons, Inc. 585 pp. Gascoyne, M., 1977, Uranium series dating of speleothems: An investigation of technique, data processing and precision. Tech-Memo: 77-4 Dept. of Geology McMaster University 80 pp. Grandstaff, D.E., 1976, A kinetic study of the dissolution of uraninite. Econ. Geology 71: 1493-1506. Gruner, J.W., 1956, Concentration of uranium in sediments by multiple migration accretion. Econ. Geology 51: 495-520. Hostetler, P.B., Garrels, R.M., 1962, Transportation and precipitation of uranium and vanadium at low temperatures, with special reference to sandstone-type uranium deposits. Econ. Geology 57: 137-167. Kigoshi, K., 1971, Alpha-recoil thoruim - 234: dissolution into water and the uranium - 234/uranium - 238 disequilibrium in nature. Science 173: 47-48. Kyuregyan, T.N., Kocharyan, A.G., 1969, Migration forms of uranium in carbonate waters of a Caucasian district. lnt. Geology Rev. 11: 1087-89. 48 49 Langmuir, D., Applin, K., 1977, Refinement of the thermodynamic prOperties of uranium minerals and dissolved species with application to the chemistry of groundwaters in sandstone-type uranium deposits. C-753; Short papers of the U.S. Geological uranium - thorium symposium, J.A. Campbell (ed.) 75 pp. Levinson, A.A., Coetzee, G.L., 1977, Implications of disequilibrium in exploration for uranium ores in the surficial environment using radiometric techniques - A review. Minerals Sci. Eng. (in press). Lisitsin, A.I(., 1962, Form of occurance of uranium in ground waters and conditions of its precipitation as UOZ' Geochemistry 9: 876-884. Osmond, J.K., Corwart, J.B., 1976, The theory and uses of natural uranium isotopic variations in hydrology. Atomic Energy Rev. 144: 621-678. Ostrihansky, L., 1976, Radioactive disequilibrium investigations, Elliot Lake area, Ontario. Geol. Surv. Canada, Paper 75: part 2, 38 pp. Robinson, C.S., Rosholt, J.N., 1961, Uranium migration and geochemistry of uranium deposits in sandstone above, at and below the water table. Part 11: Relationship of uranium migration dates, geology and chemistry of the uranium deposits. Econ. Geology 56: 1404-1420. Rosholt, J.N., 1961a., Late Pleistocene and Recent accumulations of uranium in ground water saturated sandstone deposits. Econ. Geology 56: 423-430. l961b., Uranium migration and geochemstry of uranium deposits in sandstone above, at and below the water table. Part 1: Calculation of apparent dates of uranium migration in deposits above and at the water table. Econ. Geology 56: 1392-1403. Shields, W.R., Garner, E.H., 1963, Isotopic fractionation of uranium in sandstone. Science 139: 224-26. Harshman, E.M., Shields, W.R., Garner, E.L., 1964, Isotopic fractionation of uranium related to roll features in sandstone, Shirley Basin, Wyoming. Econ. Geology 59: 570-585. Butler, A.P., Garner, E.L., Shields, W.R., 1965, Isotopic fractiona- tion of uranium in sandstone, Powder River Basin, Wyoming and Slick Rock District, Colorado. Econ. Geology 60: 199-213. Tatsumoto, M., Dooley, J.R., 1965, Radioactive disequilibrium studies in sandstone, Powder River Basin, Wyoming, and Slick Rock District, Colorado. Econ. Geology 60: 477-487. Doe, B.R., Tatsumoto, M., 1966, Evolution of the isotopic composition of uranium and thorium in soil profiles. Geol. Soc. Am. Bull. 77: 987-1003. 50 Serebryakova, M.B., 1964, Application of physiochemical methods to the deter- mination of the mode of occurance of uranium in ground waters. Geochemis- try 898-907. Syromyatnikov, N.G., Tolmachev, 1.1., 1962, Study of the isotopic ratio 23l‘U/238U in aqueous extracts from uranium - phosphate - zirconium ores with consideration of their formation. Soviet At. Energy 13: 1333. Szalay, A., 1964, Cation exchange properties ofzhunic acids and their importance in the geochemical enrichment of U02 and other cations. Geochim. Cosmochim. Acta 28: 1605-14. Samsoni, Z., 1969, Investigation of the leaching of uranium from crushed magmatic rock. Geochim. Int. 6: 613-623. Tera, F., Korkisch, J., Hecht, F., 1961, The distribution of thorium between alcohol-nitric acid solution and the strongly basic anion exchanger Dowex - l. Seperation of thorium from uranium. J. Inorg. Nucl. Chem. 16: 345-349. Thompson, P., 1973, Spelechronology and late Pleistocene climates inferred from O,C, H, U and Th isotopic abundances in speleothems. Ph.D. thesis; McMaster Univ., Hamiltion Ontario, 340 pp. Wedepohl, K.H., (ed), 1969, Handbook of Geochemistry Berlin, Springer-Verlag. Western Mining Corporation Limited, 1975, A general account of the Yeelirrie uranium deposit, prepared by the staff of Western Mining Corporation (Exploration Division), 29 pp. Yermolayev, N.P., Zhidikova, A.P., Zarinskiy, V.A., 1965, Transport of uranium in aqueous solution in the form of complex silicate ions. Geochim. Int. 2: 629- 641. IGAN "7111leHiljfilllllIIIIHEIIIEIIEILIIIIIIIIE5 93 0314