A primary platinum occurrence in the Freetown Layered Intrusion, Sierra Leone |
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Authors: | J F W Bowles |
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Institution: | (1) Mineral Science Ltd, 109 Asheridge Road, Cesham, Buckinghamshire, HP5 2PZ, UK, GB |
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Abstract: | The primary source of the alluvial platinum-group minerals (PGM) of the Freetown Layered Intrusion, Sierra Leone, has been
unknown since their discovery 70 years ago. This is a report on work in progress to establish a primary occurrence related
to the igneous layering. New whole-rock major and minor element analyses and precious metal assays show that at key horizons
there is a significant change in the silicate mineral compositions and in Cu, Cr and Ni, as well as in Pt and Pd, comparable
to those encountered in other PGM-bearing layered intrusions. Anomalous (0.1 to 0.4 g/t) Pt levels occur in pyroxene troctolites,
which maintain these levels along strike.
Received: 30 July 1999 / Accepted: 2 December 1999 |
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