Ziel
1) TO ESTABLISH A RELIABLE AND SYSTEMATIC METHOD FOR LOCATING PGM IN POLISHED THIN SECTION. 2) TO UNDERTAKE A SYSTEMATIC SURVEY OF SAMPLES TO FIND AND ANALYSE PGM IN THIN SECTION. 3) TO DETERMINE THE PROCESSES CONCENTRATING PGM IN ULTRAMAFIC AND MAFIC COMPLEXEX AND THEREFORE IDENTIFY AREAS OF LIKELY PGM CONCENTRATIONS.
A. AUTORADIOGRAPHY
THE TECHNIQUE INVOLVES THE IRRADIATION WITH NEUTRONS OF A POLISHED THIN SECTION MOUNTED ON QUARTZ GLASS. IN THE CASE OF CHROMITES, ONLY WITH A LONG DELAY AFTER IRRADIATION WILL THE MAJOR ELEMENTS BE DETECTED, AND IRIDIUM OR COBALT, WITH SHORTER HALF LIVES, ARE THE PRINCIPAL ISOTOPES LIKELY TO BE DETECTED.
A DEVELOPMENT OF THIS TECHNIQUE IN WHICH EMULSIONS ARE EXPOSED WITHIN ONE WEEK OF IRRADIATIONS SHOULD ALLOW THE IDENTIFICATION OF THE PRESENCE OF RU, PT, OS BEARING MINERALS THOUGH AT LOWER SENSITIVITY THAN IRIDIUM.
B. LABORATORY ANALYSIS
THIS INCLUDES:
1. PRODUCTION OF POLISHED THIN SECTIONS
2. LOCATION OF PGM WITHIN THESE SECTIONS USING AUTORADIOGRAPHY
3. ONCE DETECTED, THE MINERALS CAN BE EXAMINED USING AN OPTICAL MICROSCOPE AND AT A HIGHER SCALE USING A SCANNING ELECTRON MICROSCOPE. THE MINERALS CAN THEN BE ANALYSED USING AN ELECTRON MICROPROBE WHICH HAS ALREADY BEEN CALIBRATED FOR THE ANALYSIS OF PLATINUM GROUP MINERALS.
C. PROCESSES CONCENTRATING PLATINOIDS
THE ANALYTICAL DATA WILL BE USED TO EVALUATE THE ABUNDANCE OF PGM IN SAMPLES AND HENCE THEIR SPATIAL DISTRIBUTION AND THE CONCENTRATION INTO VARIOUS TYPES OF HOST MAFIC AND ULTRAMAFIC ROCK. ELECTRON MICROPROBE ANALYSIS WILL ALLOW THE COMPOSITIONS OF THE PGM TO BE OBTAINED AND HENCE THE CHANGES IN GEOCHEMISTRY OF THE PGM WITH DEPTH AND LATERALLY IN COMPLEXES WILL BE ASSESSED. FROM THIS IT IS HOPED TO EVALUATE THE RELATIVE IMPORTANCE OF PRIMARY IGNEOUS PROCESSES, REEQUILIBRATION, METASOMATIC AND HYDROTHERMAL ALTERATION AND WEATHERING PROCESSES IN CONTROLLING THE DISTRIBUTION OF THE PGMS.
THE SAMPLES (PGM BEARING CHROMITES) WILL COME FROM THE SHETLANDS, SAUDI ARABIA, THE BUSHVELD COMPLEX, NEW CALEDONIA. ALSO AVAILABLE FOR STUDY WILL BE SYNTHETIC STANDARDIZED SAMPLES PREPARED IN DENMARK.
OTHER PARTICIPANTS OF THIS COORDINATED PLATINUM RESEARCH: BRGM, ORLEANS (CONTRACT MSM 023) AND UNIV.COPENHAGEN
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MK7 6AA Milton Keynes
Vereinigtes Königreich