Platinum Metals Rev., 2003, 47, (2), 59
Geology of Platinum Group Elements
CIM special volume 54: the geology, geochemistry, mineralogy and mineral beneficiation of platinum-group elements Edited by L. J. Cabri, Canadian Institute of Mining, Metallurgy and Petroleum, Montréal, 2002, 852 pages, ISBN 1-894475-27-5, Non-Members: CDN$220.00, U.S.$150; CD-ROM: CDN$25.00, U.S.$18.00
This CIM Special Volume 54 (publication) edited by Louis J. Cabri is the successor to the CIM Special Volume 23 first printed in 1981 and reprinted in 1989. It is an ambitious undertakingaimed at presenting a series of review papers onthe platinum group elements (PGEs) rather than attempting to deliver results of the very latestresearch in the field. Of the 26 papers included,one is devoted to analytical methods, five to phasegeochemistry and three to mineral processing and extractive metallurgy. The other contributions are review papers coveting the full range of geological settings in which the PGEs occur.
Papers include reviews of the main PGE deposits comprising those associated with Sudbury(Canada), the Bushveld Complex (South Africa),the Stillwater Complex (U.S.A.), the Great Dyke(Zimbabwe) and Noril’sk (Russia). These papershave been prepared by workers with enormous experience of the deposits covered and incorpo-rate the results of the key relevant contributions tothe literature. As such they can be read in the con-fidence that they reflect the consensus that hasemerged about the origin of the deposits and theprimary controls of the mineralisation. This will beof particular benefit to professionals not expert in the field but who may need a balanced and author-itative description of these key primary magmaticdeposits which currently provide virtually all the newly mined supplies of the PGEs.
Deposits associated with layered intrusions that are currently the focus of exploration in northern Finland and the Kola Peninsula in Russia are also covered, and a convenient description of their geo-logical setting, characteristics and potential as major sources of PGE is provided by T. T. Alapietiand J. J. Lahtinen. The association of the PGEs with komatiitic-hosted nickel sulfide mineralisationis also recognised in a separate paper devoted to this topic, by C. M. Lesher and R. R Keays. There are also papers describing PGE mineralisationassociated with minor magmatic deposits in theKola Peninsula, by A. V. Dedeev and colleagues.
More exotic settings associated with hydrother-mal fluids, contact mineralisation and placer mineralisation are the focus of several detailed reviews. The conclusion that can be drawn is that there remain many unanswered questions on the chemical and physical controls on these styles ofmineralisation. The Platreef of the Bushveld Complex has demonstrated the importance of seeking an understanding of the underlying genesis of contact mineralisation. A robust model for thecontrol of PGE mineralisation is needed to predict continuity of the ore zone as this underpins the integrity of resource estimation and grade control procedures during mining.
The paper on sample preparation and analytical methods by E. L. Hoffman and B. Dunn, should be compulsory reading for anyone embarking on PGE exploration — all too often projects considered to have high potential for hosting PGEs prove to be geochemically depleted in these metals when subject to geologically-controlled sampling and analysis by experienced laboratories. The paper provides insights into the importance of selecting the correct analytical procedures when determining PGE concentrations in geological material and matching these to the mineralogical characteristics of the host samples and also into the precision and accuracy required.
The commercial sensitivity and proprietary nature of downstream processing of PGE mineralisation is well known and the paper on the beneficiation of South African PGE ores, by R. K.W. Merkle and A. D. McKenzie, is a very useful review. While probably of limited value to a min-eral process engineer for design purposes, it does demonstrate why new PGE projects are often est-ablished as joint ventures with existing producers who have the necessary expertise in the field. The key role of process mineralogy is recognised in the publication and demonstrated in a paper on the mineralogy and behaviour of the platinum group metals during processing of the Noril’sk ores by M.Z. Komarova and colleagues.
The text runs to 844 pages and, surprisingly, it has no subject index. Furthermore none of the papers has an abstract which means that retrieval of information is not going to be easy for the casual reader. However, the CIM offers a CD-ROM containing the papers in PDF format and this allows a word search in the usual way. However, this is no substitute for a professionally compiled index. While clearly it must have been a formidable task securing all the contributions, arranging reviews and coordinating final versions, the editor would have produced a more useful volume if he had been more proactive in the final production stage. It would, for example, have been helpful ifin the Preface Cabri had explained how his own contribution on the platinum group minerals related to the role of process mineralogy where this was described in papers on beneficiation.
Nevertheless for geologists, chemists and mineral process engineers seeking a convenient format for obtaining background information on PGE projects the effort of working through the primary material would be well worthwhile.
Dennis Buchanan is the Emeritus Professor of Mining Geology and a Senior Research Fellow at the Department of Earth Science and Engineering, Royal School of Mines, Imperial College, London. Hehas worked as a mining geologist in both the gold and platinummines in South Africa and has published widely on the origin,exploration, evaluation and production of pges.