Page 63 - Introduction to Mineral Exploration

46 A.M. EVANS & C.J. MOON

and the Environment (1994) provides a good geologist must be able to identify, or have iden-
introduction and a link with economics. tified for him or her, every mineral in a possible
Sawkins’ Metal Deposits in Relation to Plate orebody (see Chapter 2). This will help them to
Tectonics (second edition 1990, Springer assess the full economic potential of any mate-
Verlag) gives an overview of the major struc- rial to be mined from it and prevent them over-
tural controls on deposits. looking the presence of additional valuable
constituents or deleterious substances that
may render the deposit unworkable. There are
3.5 SUMMARY OF CHAPTERS 1, 2, AND 3 many techniques now available for compre-
hensive mineralogical examination of mineral
The general nature of ore, industrial minerals, samples and these are discussed in section 2.2.
and orebodies are discussed in sections 1.1 and However, such investigations must be quant-
1.2 and it is emphasized that these deposits itative as well as qualitative; grain size and
must contain valuable constituents that can be shape, relative mineral amounts, and the man-
economically recovered using suitable treat- ner of interlocking must be determined.
ment. (Chapter 11 is largely devoted to a de- The nature and morphology of mineral de-
tailed coverage of this principle.) In the past too posits are very varied and only a restricted cov-
much interest in many mining circles has been erage of these subjects can be given in this book
placed on the more glamorous metallic de- (see section 3.1). The tyro is therefore strongly
posits and the general importance of industrial recommended to acquire a broad knowledge of
minerals neglected (see section 1.2.2). The these subjects from extended reading so that
value of both is governed by demand and when he or she detects signs of mineralisation
supply (see section 1.2.3) and many factors in- they may soon develop a working hypothesis of
cluding government action, recycling, and sub- the nature of the particular beast they have
stitution play a part in determining their come upon.
market prices. In section 1.3 the principal steps Having recognized the tectonic setting of
involved in the exploration for, and develop- an exploration region, models of the deposits
ment of, a mineral deposit are summarized likely to be present, and particularly of those
and these are the subjects that are covered in being sought, should be set up. Both empirical
more detail in the rest of this book. A sound and genetic models are used, often in combina-
knowledge of these is necessary in choosing tion, to show how the materials sought relate
exploration areas (see section 1.5.) leading to to geological factors including geophysics and
the development of a rationale of mineral ex- geochemistry. To understand how models are
ploration (see section 1.6). constructed and used, unconformity-related
Economic mineral deposits are extremely uranium deposits are discussed in some detail
variable in their mineralogy and grade and the (see section 3.2.3).

3.6 APPENDIX: MINERAL DEPOSIT MODEL CLASSIFICATION OF COX AND SINGER (1986). ONLINE
LINKS CAN BE FOUND AT USGS (2004).

Mafic and ultramafic intrusions

A. Tectonically stable area; stratiform complexes
Stratiform deposits
Basal zone
Stillwater Ni-Cu 1
Intermediate zone
Bushveld chromitite 2a
Merensky Reef PGE 2b
Upper zone
Bushveld Fe-Ti-V 3