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  • Development of techniques for the determination of the platinum-group elements in ultramafic rock complexes of potential economic significance: mineralogical studies

Abstract

Traditionally it is thought that the platinum-group elements (PGE) in ophiolite complexes are dominantly Ru, Os and Ir and are rarely present at concentrations greater than 1-2 ppm. In the Shetland ophiolite complex all six PGE and Au are present as discrete mineral phases. Unusually enriched values of up to 80 ppm total PGE have been recorded. The PGE-rich rocks are chromite-rich samples and adjacent dunites. The platinum-group minerals (PGM) occur in chromite-rich samples from all levels within the ultramafic part of the complex, but are concentrated in two lenses enclosed by envelopes of dunite within mantle harzburgite. At Cliff Pt, Pd and Rh dominate giving positive slope chondrite normalized patterns typical of stratiform complexes whereas at Harold's Grave Ru, Os and Ir dominate giving negative slope chondrite normalized patterns which are generally thought to be characteristic of ophiolite complexes. In chromite-rich samples Ru-, Os- and Ir- bearing PGM are located both within chromite grains, often associated with silicate inclusions, and in the silicates between chromite grains. Pt-, Pd- and Rh-bearing minerals are restricted to the silicate matrix between chromite grains and in this study none have been found enclosed by chromite grains. These discoveries were obtained using beta-autoradiography.

Additional information

Authors: PRICHARD H M, Department of Earth Sciences, The Open University, Buckinghamshire (GB)
Bibliographic Reference: EUR 11631 EN (1988) FS, 163 pp., ECU 13.75
Availability: (2)
ISBN: ISBN 92-825-9245-6;CD-NA-
Record Number: 198910361 / Last updated on: 1994-12-01
Category: PUBLICATION
Original language: en
Available languages: en