Application of probability graphs in mineral exploration

586 scope and rigour of any individual chapter, he can almost certainly gain valuable insights from other sections. The b o o k will be found useful as a sourcebook and as a reference for graduate or undergraduate courses in disciplines concerned with mineral resource management. In spite of successful efforts to publish a non-technical exposition, the direct contribution of World Mineral Supplies to the exhaustibility debate among general readers will be constrained by its price and size. The appearance of this b o o k may influence some economists and social ' scientists to reconsider their assumptions and to work more closely with scientists and engineers. If so, this will no d o u b t benefit both groups. The editors and other contributors strongly recommend government research subsidies and other forms of intervention which could lead to accelerated discovery and exploitation rates, thus stimulating the supply of minerals in order to satisfy increasing world demands. Adjustment mechanisms which would operate in the case of a real or foreseen supply shortfall are largely ignored. Many policy analysts would n o t agree that artificial stimulation is desirable, and it is to be hoped that future commentators will evaluate policy alternatives and their implications more fully. In summary, the present b o o k should not necessarily be taken as a guide to the question of whether the supply of minerals should be stimulated. It is, however, an important source of collected information on the current supply situation and the ways in which mineral supply will be maintained and augmented in the future. C.G. MILLER (Kingston, Ont.)

Application of Probability Graphs in Mineral Exploration by A.J. Sinclair. Association of Exploration Geochemists Special Volume No. 4. The Association of Exploration Geochemists, P.O. Box 523, Rexdale (Metropolitan Toronto), Ont., 1976. C. $ 8.00 non-A.E.G, members, C. $ 6.00 A.E.G. members and students. The manual completely describes the use of normal and log-normal probability graph paper in geochemical exploration. The manual begins with a general review of exploration data, histograms, and cumulative distributions (Chapter 1). Cumulative probability paper is then introduced (Chapter 2) and single populations are illustrated (Chapter 3) with several field examples. Next, there is a detailed discussion of mixed populations and h o w to partition these into single populations (Chapter 4). Various aspects of the procedure are shown with field examples (Chapter 5) and for combinations of three or more populations (Chapter 6). The manual concludes with a discussion of the problems of geochemical thresholds (Chapter 7) and some additional topics like confidence limits (Chapter 8).

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The easy to understand text requires no special knowledge of statistics and the only equipment needed is probability paper and a slide rule. The text shows many field examples, has good illustrations and gives appropriate cautions as to "pitfalls" that might be encountered. Because of the simple way in which the basic concepts of background, anomaly and threshold can be visualized using probability paper, it is hoped that this book will serve as a guide to future discussion and understanding of these concepts. The manual, however, does have some weak points. The discussion of the use of probability graphs for purposes of contouring or map coding is incomplete (hidden in section 5.2) and has no examples. The minimum number of samples needed to obtain a useful graph is discussed (section 8.1), b u t then nothing is said as to the maximum number. Experience shows that as the number of samples increases greatly, the combination of multiple overlapping populations tends to produce an apparent single population. As the dominant aspect of probability graphs is their slope, comments on the contribution of sampling and analytical error to the slope and confidence limits would have been desirable. We feel the manual is an excellent h a n d b o o k for the field geologist and student who needs a simple graphical display of data to aid in the interpretation of results. We anticipate the use of these methods will increase greatly in the future. BJORN B~LVIKEN and W.E. SHARP (Trondheim, Norway)

Conceptual Models in Exploration Geochemistry - - N o r d e n 1975 edited by L.K. Kauranne. Journal of Geochemical Exploration, Special Issue, Volume 5, No. 3, pp. 173~-420 (Elsevier, Amsterdam, 1976). The first series of geochemical case histories, Conceptual Models in Exploration Geochemistry -- The Canadian Cordillera and Canadian Shield, edited by P.M.D. Bradshaw, was published in 1975. This special issue is the second in the series and, following the format established in the first volume, presents geochemical case histories from the Scandinavian countries and East Greenland. The volume, in addition to describing sampling, analytical and interpretational techniques tried in the Fennoscandian countries, also contains a number of small-scale investigations which would normally go unpublished or appear in condensed form as part of extensive studies. Considering that the Scandinavians were, of necessity, pioneers in the fields of drift prospecting and surficial geochemical mineral exploration, this volume provides a timely summary of their experiences and conceptual approaches to problems of geochemical prospecting in glaciated terrain which will be of considerable interest to all applied geochemists. The volume is divided into four sections: (1) Introduction (2) Geochemical Migration (3) Case Histories, and (4) Meth-