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ASSESSMENT OF ALLUVIAL DEPOSITS RELATED TO STRATABOUND EUROPIUM RICH MONAZITE MINERALISATION - A MAJOR FUTURE SOURCE FOR SPECIFIC RARE EARTHS USED IN NEW TECHNOLOGY

Objective

The objective is to improve the exploration methodology as well as the knowledge of stratabound europium rich monazite deposits and their related alluvials. Improvements in these domains can lead to the discovery of exploitable alluvial deposits inside and outside the European Commission and contribute to the acquisition of an EC know how for exploration and reserve estimation for this type of deposit.

Areas selected for carrying out the research activities presented below are:
Rwanda, where a high potential for europium rich monazite deposits does exist;
central southern Spain (Montes de Toledo area), where monazite deposits are known;
southern France (Pyrenees), where monazite has recently been discovered, and Brittany, where gray monazite occurrences were first discovered in the EC;
Belgium (Ardenne massif), where gray monazite has also been described;
and several localities in north west Iberian Peninsula, where gray monazite also occurs.

The work programme will consist of the following methodologies.
Firstly, genetic studies of europium rich monazite. Such studies in the field and in the laboratory will include:
detailed comparative paleogeographical, stratigraphical, petrological and mineralogical investigations to characterize the europium rich monazite horizons and associated minerals (areas investigated: Spain, Pyrenees, Rwanda, Belgium);
lithogeochemical investigations of the mineralized shale formations, including major, minor and trace elements and rare earths distribution, and a comparison with barren shales of the same formations (areas investigated: Spain, France, Rwanda, Belgium);
search of indicator elements for possible source and origin of the europium rich monazite shales by statistical geochemical approach (areas investigated: Spain, France, Rwanda);
role of phosphate and organic compounds in the formation of europium rich monazite stratabound deposits;
study of the stability of europium rich monazite in contact metamorphism zones and possible change in the rare earth element (REE) distribution pattern; (areas investigated: Spain and Belgium);
comparative study of the rare earths geochemical distribution pattern of europium rich monazite in the same formation and in geological formations of different ages from Precambrian (Rwanda) to Paleozoic (Europe) to detect possible change in the rare earths distribution within a single deposit and along the geological time scale.

These investigations should permit more precise characterization of the geological environments favourable for europium rich monazite formations in the EC and in Rwanda.

The second part of the work programme is aimed at developing an exploration methodology for a better selection of the most favourable europium rich monazite alluvial deposits, at present the only exploitable source of europium rich monazite. This will include:
mineralogical examination of heavy minerals concentrates for europium rich monazite and other possible valuable minerals (gold, tin, niobium, etc) in the selected areas;
development of advanced geostatistical methods, such as the classification and regression tree (CART) technique, for geochemical analyses of stream sediments and heavy minerals concentrates used in large scale exploration for a quicker delineation of possible placer deposits containing europium rich monazite (area: Spain);
development of a rapid method for determining the approximate content of europium rich monazite and other valuable minerals in alluvial, particularly in their heavy fractions;
impact study of the geomorphology on the drainage system in the formation of monazite rich placers using field observations and satellite imagery (areas: Spain, France, Rwanda);
and use of remote sensing and data integration techniques to select the most favourable zones, in specific geological environments, with a multivariate approach which can be applied at a large scale and extrapolated to postpaleozoic formations (area: Spain).

The third part of the work programme is reserve evaluation studies. In order to overcome the difficulties in the accurate assessment of reserve calculations encountered in this type of deposit, the following methodologies will be developed.
Establishment, by statistical correlations, of the relationships between REE contents and other elements easily detected by multielemental analysis. Knowledge of these relationships can allow estimation of rare earth contents by standard analytical methods.
Use of georadar methods and comparison of results with those obtained by conventional (electric and magnetic) methods. The georadar technique allows acquisition of information about the underground distribution of rocks and sediments in a fast and cost effective way. It allows the detection of paleochannels where monazite can be trapped in sediments by transport energy loss (areas: Spain and Rwanda).
Cross checking of the results obtained by the above methodologies with those given by trenching, sampling, ore concentration and analysis (areas: Spain, France and Rwanda).

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Minas de Almadén y Arrayanes SA
Address
S/n,cerco De San Teodoro
13400 Almadén (Ciudad Real)
Spain

Participants (3)

Bureau de Recherches Géologiques et Minières (BRGM)
France
Address
Avenue De Concyr
45060 Orléans
Idrogeo Srl
Italy
Address
Via Mercato Vecchio 1
34124 Trieste
Universite Libre de Bruxelles
Belgium
Address
Avenue Franklin Roosevelt 50
Bruxelles