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FACTORS GOVERNING CONCENTRATIONS OF PLATINIUM GROUP ELEMENTS (PGE) IN LAYERED COMPLEXES

Objective

THIS PROJECT MUST PROVIDE NEW TOOLS FOR THE EXPLORATION OF PGE IN BASIC-ULTRABASIC COMPLEXES AND MAY FACILITATE THE DETECTION OF PGE-BEARING RICH HORIZONS.
50 complexes associated with platinum group elements (PGE) have been explored and 5 complexes have been geologically mapped. This research was coupled with extensive laboratory studies of petrology, geochemistry and mineralogy and included thedevelopment of major scientific concepts. This has resulted in a comprehensive understanding of the synthesis of factors leading to PGE mineralization across a broad spectrum of complexes in many different settings. Thus a highly effective platform has been created on which to develop critical cost effective exploration strategies.

The aim of the research was the development of modern and reliable methodology of prospection for platinoids (platinum group elements (PGE)) allowing:
recognition of complexes mineralized in PGE;
characterization within these complexes of restricted zones with high metallogenic potential;
lowering prospection costs;
elaboration of genetic models based on field and laboratory experiments.

A multidisciplinary approach was engaged in the area of Andriamena, Madagascar.
With respect to the first objective, complexes mineralized in PGE with the PGE concentration (platinum plus palladium) of up to 8.4 g/t were discovered in the West Andriamena zone.

The second objective concerning the structural, petrological and geochemical characterization of zones with high metallogenic potential in the Andriamena complexes was less successful because of their complexity of the zones and their variation between each other. However, there was success in finding the PGE enrichments despite the absence of petrological and structural markers in the field.

As far as the prospection cost is concerned, the collaboration between the prospection team and the scientific team allowed the establishment of an efficient prospecting approach in areas with lateritic cover. However, the method has still to be tested to become an effective prospection tool.

To better understand the genesis of the PGE mineralization in the West Andriamena zone, it must be chemically modelled. The model should involve the separation of a fluid phase enriched in PGE from a magma at an early stage of differentation. This requires a better knowledge of the evolution of magma chamber and the permeability of freshly formed cumulates and must take into account the role of fluids in the concentration of PGE. It must also consider the role of chromite and sulphide deposits and other effects of fluid interaction with surrounding rocks. This may constitute a new prospection tool for this type of deposits which cann ot be detected by existing geophysical methods.
THE RD ACTIVITIES WILL BE CONCENTRATED IN THE REGION OF ANDRIAMENA WHERE PGE ARE FOUND IN THE ALLUVIALS AND IN BASIC-ULTRABASIC ROCKS CUTTING THE BASEMENT.

THE RESEARCH INCLUDES :

- STUDY OF THE PGE DISTRIBUTION IN PARTICULAR PT AND PD, IN THE DIFFERENT TYPES OF BASIC-ULTRABASIC ROCKS.
- STUDY OF CRYPTIC VARIATION OF CUMULATIVE PHASES.
- MINERALOGY OF PGE AND ASSOCIATED PHASE IN PYROXENITES AND CHROMITITES.
- DISTRIBUTION OF VOLATILE (CL, F) WITHIN THE PGE ENRICHED SEQUENCE.
- CHARACTERIZATION OF FLUID PHASES, DISCRIMINATION OF METAMORPHIC AND MAGMATIC FLUID (RAMAN SPECTROMETRY).

THESE STUDY SHOULD YIELD NEW DATA WHICH WILL ENABLE BETTER UNDERSTANDING ABOUT PT AND PD CONCENTRATION PROCESSES AND WILL PROVIDE GUIDELINES FOR THE EXPLORATION OF PGE.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Bureau de Recherches Géologiques et Minières (BRGM)
Address
39-43 Quai André Citroën
75739 Paris
France

Participants (1)

KOEBENHAVNS UNIVERSITET
Denmark
Address

Koebenhavn