A Review of Spanish Uranium Resources and Recent Developments in the Province of Salamanca
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XA9745125 A REVIEW OF SPANISH URANIUM RESOURCES AND RECENT DEVELOPMENTS IN THE PROVINCE OF SALAMANCA J.A. GONZALEZ GRANDA, J. RUIZ SANCHEZ-PORRO, J. ARNAIZ DE GUEZALA FE Mining Centre, Salamanca, Spain Abstract Uranium exploration activities in Spain carried out during the 1950-1992 period, led to the discovery of a number of deposits in different geological environments. Presently there is only activity at the FE area in Salamanca province, where the only remaining mining centre is located. A new dynamic leaching processing plant with a capacity of up to 950 t U3Og t/year began operation in 1993, at FE mine. The development and planning of the mining in the open pits of ENUSA (province of Salamanca, Spain) under the present low market prices, has led to the implementation of a working scheme, based on the following concepts: Detailed knowledge of the distribution and quality of the mineralization by sufficiently close spaced drilling, with 3D positioning and grade estimation by deviation and gamma ray probing. Use of either geostatistical or arithmetical grade interpolation techniques, properly validated with production, adapted to the density of the information available. Economic optimization of the open pit, by means of the 3D Lerchs-Grossmann technique, as a guide for the final pit design. Calculation of the optimal pit shapes and recoverable resources under different price conditions. These techniques implemented by means of computerized data acquisition and processing systems, are used to face with versatility, the present economic conditions. A full review of the uranium deposits in the province of Salamanca is being carried out with these means. 1. URANIUM DEPOSITS AND EXPLORATION IN SPAIN 1.1. Historical exploration in Spain Uranium exploration in Spain was carried out, from 1950 to 1981 by the Junta de Energia Nuclear (J.E.N.), a public organism that depends on the Industry Ministry. The Empresa National del Uranio S.A.( ENUSA) created in 1972, is a company owned by the J.E.N. and the National Industry Institute (I.N.I.) (Fig. 1). ENUSA has carried out uranium exploration in Spain and overseas, directly, since 1974 until 1992, when all exploration activities were stopped and all the investigation effort was concentrated on the development and feasibility studies of the FE area deposits. From 1989 to 1994 a Joint Venture, ENUSA/CISA (COGEMA), has done some exploration in the province of Caceres (precambrian/cambrian schists and hercynian granites), without outstanding results. 1.2. Uranium deposits During this time, most of the favourable geological units of Spain have been covered with airborne and ground exploration methods (Fig. 2). 61 INCORPORATED IN 1972 ACTIVITIES -PROCUREMENT OF ENRICHED URANIUM •PRODUCTION & EXPLORATION OF URANIUM CONCENTRATES -DESIGN & FABRICATION OF FUEL BUNDLES PRODUCTS -ENRICHED UF6 FOR SPANISH REACTORS -DESIGN & FABRICATION OF FUEL BUNDLES FOR SPANISH AND EUROPEAN REACTORS SHARE CAPITAL: 10.000 MILLION PTAS SHAREHOLDERS TENEO: 60% CIEMAT: 40% TOTAL WORK FORCE : 703 EMPLOYEES CORPORATION'S INTEREST IN EURODIF (11,11 %) CORPORATION'S INTEREST IN COMINAK (10 %) FIG. 1. ENUSA. 62 AIRBORNE ;£v£Xj GROUND FIG. 2. Areas covered with airborne and ground exploration methods. 63 0 DON BENITO (Bada|oz) AREA TYPE IN SITU RESOURCES PRESENT SITUATION (tU3O8) CIUDAD RODRIGO VEIN 36i391 MINING / DEVELOPMENT (Salamanca Province) (IBERIAN TYPE) VEIN UNDEVELOPED CACERES PROVINCE (IBERIAN TYPE) 1.082 NOT FEASIBLE PRESENTLY DON BENITO VEIN UNDEVELOPED (Bada|oz Province) (IBERIAN TYPE) 3.225 NOT FEASIBLE PRESENTLY MAZARETE UNDEVELOPED (Guadala)ara Province) SANDSTONE 5.666 NOT FEASIBLE PRESENTLY TOTAL 46.364 FIG. 3. Uranium in situ resources in Spain. 64 GEOLOGY Tertiary basins. Mesozoic. Paleozoic rocks at green schists and lower metamorphic grade ^| Calc-alkalic rocks a)gabbro and diorite , ultramatic (Betic range) y} Two mica granites. 1 BETIC RANGE.S.Sir. 2 OSSA- MORENA ZONE. 3 SOUTHPORTUGUESE ZONE 4 CENTRALIBERIAN ZONE 5 MAFIC AND ULTRAMAFIC MASSIFS. 6 CATALANIDES 200 280 Km. ON FIG. 4. Geological setting of uranium deposits in Spain. Geological setting and in situ resources are given in Figs 3 and 4. Among the great number of occurrences studied, a number of deposits were evaluated, some of them (vein type in granites of Caceres and Jaen) mined out by J.E.N.. Of remaining deposits the most important are in Salamanca where they are being mined, whereas the rest is not mineable under the present economic conditions. The main deposits outside the province of Salamanca can be summarized as follows: PROVINCE NAME OF DEPOSIT GEOLOGICAL TYPE IN SITU SETTING RESOURCES (t U3O,) Fluvial sandstone GUADALAJARA MAZARETE braided channels SANDSTONE 5 660 Triassic (Buntsandstein) Silurian BADAJOZ DON BENITO AREA carbonaceous VEIN (Iberian) 3 225 schists, in TYPE contact with granites ACEHUCHE- Precambrian CACERES CECLAVIN Cambrian VEIN (Iberian) 1 082 schists, in TYPE contact with granites Most of the in situ resources (78%) and all the presently mineable resources of Spain, are located in the province of Salamanca. RAR resources amount to 9148 t U, and EAR-I to 10 688 at the < $80/kg U cost range. Average grades range from 0.6 to 2 kg/t, depending on the cut-off grades (from 0.2 to 1.0 kg/t). The main deposits in Salamanca are of the vein-Iberian type, with mineralization placed in fractured precambrian- Cambrian and occasionally Silurian schists (map in Fig. 5). The deposits are of a low temperature hydrothermal origin. The main metallogenetic characteristics are summarized in Fig. 6. The mineralization controls at regional and ore body scale are: 1) Regional fracture zones NE-SW; 2) Ore deposited in associated (Riedel type) fractures, following complex patterns; 3) Ore in a band parallel to the pre-tertiary erosion surface, 5-20 m below and deposited in the reduction zone and lower part of the oxidization zone. 4) Occasional lithological control, when carbonaceous schists and contrasts of competence (hardness) are present. A block diagram is given in Fig. 7, and a map of mineralized fractures at FE in Fig. 8. 1.3. Historical uranium production The evolution of the production in Spain, is summarized in Fig. 9. Production sites at different state of activity are shown in Fig. 10. 66 A A A A A A A A A A A A A A A A A AAAAAAAJ A A A A A A/"" \i A A A A A A A A A A A A A A A A A GEOLOCY SIZE OF DEPOSIT PRESENT STATE 0 - MC t,]0> o GEOLOGICAL EVALUATION O 500 - JOOC I UW COUPLETH) EVALUATION 3.000 - 5 ooc t JJOS UN0CVO.0PED PRCCAMBRUN - CAMBRIAN o SCHISTS O OEVELOPMEHT / MININ0 0 1000 2000 MOO 4000 5000 Mts. SCALE D • URANIUM OCCURRENCE Rcf.: CCOINGCR.DWC FIG. 5. Geological map with the main uranium deposits in FE area (Salamanca). 67 1 •- High geochemicai U Content in the carbonaceous schists. 2.- Nature of the alteration processes: Chloritization and hematitization (intensive but not penetratives). 3.- Low temperature, hydrothermal, paragenesis. 4.- Banded, geopetal andvarved structures; Subsurficial environments and intermittent character of the mineralization. 5.- Radiometric age of the pitchblende (37 - 57 m.a., lower tertiary). 6.- Temperature (70 - 230°C) and salinity (0 - 25% NaCI) deducted from fluid inclusion studies. 7.- Primary ore placed in fractures and breccias. 8.- Surficial character of the tectonic processes. FIG. 6. Metallogenetic characterization of FE type uranium deposits. 68 Tertiary arkoses Precambrian • Cambrian Schists Mineralized Zone (in fractures) Oxidized Zone Uranium mineralization Radioactive anomaly In surface FIG. 7. Uranium ore controls at FE area (diagram). 69 FIG. 8. Mineralized fractures at Fe mine. 70 t U3O8 350 301 300 - 270 263 260 254 254 250 237 225 230 219 216 207 200 - 183 165 150 140 127 132 128 132 100 86 50 - 0 - i r 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 0 ELEFANTE E3i-A HABA • QUERCUS FIG. 9. Historical evolution of uranium production in Spain. FR ANC1 A LEGEND IH MILL UNDER OPERATION jf| NOT OPERATING MILL SITE % UNDERGROUND MINE O OPEN-PIT M3NE ^ HEAP LEACHING + TAILINGS STORAGE B : DECOMMISSIONED C : ON DECOMMISSION STILL IN OPERATION OR PROJECT D : UNDER OPERATION; DECOMMISSIONING FIG. 10. Uranium facilities in Spain. 2. PRESENT ACTIVITIES 2.1. Exploration/development 2.1.1. General Presently, all investigation related activities are concentrated in FE area, province of Salamanca, where development drilling at 10 x 10 m spacing, is being carried out at a rate of 100 000 m of percussion boreholes per year. In Fig. 11 all exploration and development drilling in recent years is shown compared with in situ resources. Great effort is being made to complete the investigation of the D and M-SAGERAS deposits close to FE (Fig. 5), from which all medium to short term production will be obtained, together with FE. 2.1.2. Implementation of new integrated data acquisition and processing techniques to investigation by close spaced drilling, open pit design and mine planning In the present situation of low market prices for the concentrates, it becomes very important to reduce production costs. The first step is to have the best possible knowledge of the deposits, so to be able to plan accurately the mining operations. This affects the following aspects: grade and tonnages forecast, localization of ore, localization of barren areas in or nearby the deposit, to place waste dumps, in order to reduce transport distances, design of haulage roads, determine types of ore that need different processing parameters. The acquisition/processing system at FE is shown in Fig. 12. To achieve this, ENUSA has upgraded the following phases of the process: 2.1.2.1. Grade estimation by simultaneous gamma ray and deviation logging In the FE type deposits, due to the foliated and fractured nature of the schists, borehole deviation can be of importance at the 10 x 10 m grid scale (Fig.