Marjoribanks R. Geological Methods in Mineral Exploration and Mining

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Geological Methods in Mineral Exploration

and Mining

Roger Marjoribanks

Geological Methods

in Mineral Exploration

and Mining

Second Edition

123

Roger Marjoribanks

27A Axford Street

Perth WA 6152

Australia

marjex@ozemail.com.au

ISBN 978-3-540-74370-5 e-ISBN 978-3-540-74375-0

DOI 10.1007/978-3-540-74375-0

Springer Heidelberg Dordrecht London New York

Library of Congress Control Number: 2010926490

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Preface

This book is written as a practical ﬁeld manual to be used by geologists engaged

in mineral exploration. It is also hoped that it will serve as a text and reference

for students in Applied Geology courses of universities and colleges. The book

aims to outline some of the practical skills that turn the graduate geologist into

an explorationist. It is intended as a practical “how to” book, rather than as a text on

geological or ore deposit theory.

An explorationist

is a professional, usually a geologist, who searches for ore

bodies in a scientiﬁc and structured way. Mineral exploration professionals include

a range of people: business people involved in ﬁnancial and entrepreneurial activ-

ities in the mining industry, board members and company management no longer

involved in day to day exploration but often with past hands-on experience, tech-

nical assistants, tenement managers, environmental and safety personnel, drillers,

surveyors, IT specialists, geophysicists and geochemists, ore reserve specialists, var-

ious types of consultants, and the exploration geologists. Typically the exploration

geologists are the jacks-of-all-trades with an overview of the team and the project.

Although explorationist is a somewhat awkward and artiﬁcial term, this is the only

available word to describe the totality of the skills that are needed to locate and

deﬁne economic mineralization. Even the mine geologist, attempting to deﬁne ore

blocks ahead of the mining crews, is an explorationist. The most fundamental and

cost-effective skills of the explorationist relate to the acquisition, recording and pre-

sentation of geological knowledge so that it can be used to predict the presence of

ore – these are the skills that are the subject of this book.

Practical ﬁeld techniques taught at undergraduate level are often forgotten and

sometimes, although taught, are not reinforced by subsequent practice; some skills

that the explorationist needs may never be adequately taught in the academic envi-

ronment of universities. Special techniques and skills – or example, identifying

prospective ground for acquisition, detailed prospect mapping or logging drill core

Throughout the book, the rules of English grammar compel me, from time to time, to ascribe a sex

to my protagonist. In the ﬁrst edition I got around this by using the expression “he or she”; but this

now seems to me an awkward circumlocution. In this edition I simply ascribe gender alternately.

vi Preface

or cuttings – seldom ﬁgure in basic training courses. Although no book can substi-

tute for hands-on experience and demonstration, this manual aims to address some

of these deﬁciencies.

The book does not offer a set of standard rules that must be invariably followed. It

describes practical skills and techniques that, through the experience of many geol-

ogists, have been found to be effective. However, it is not the author’s intention to be

prescriptive; each geologist has to develop their own techniques and will ultimately

be judged on results, not the process by which these results were reached. In mineral

exploration, the only “right” way of doing anything is the way that locates ore in the

quickest and most cost-effective manner. It is preferable, however, for an individual

to develop their own method of operation after having tried, and become aware of,

those procedures that experience has shown to work well and which are generally

accepted in industry as good exploration practice.

New ideas and techniques are constantly emerging and no book such as this can

be regarded as being a ﬁnal statement. To make this a useful document and to keep

it up to date and relevant, geologists should use it critically.

The chapters of the book approximately follow the steps that a typical explo-

ration programme would go through. In Chap. 1, the generation of new projects

and prospects and the nature of the exploration process are described. In Chaps. 2

and 3 are descriptions of the various techniques employed in making geological

maps from remote sensed reﬂectance imagery, surface outcrop and mine openings.

Chapter 4 covers techniques employed by the explorationist to create new rock expo-

sure – trenching, pitting, stripping and underground development. Chapters 5, 6 and

7 (supported by several Appendices) cover all aspects of drilling. These chapters

constitute a major part of this book, reﬂecting the supreme importance of drilling to

the explorationist. In Chap. 8 is a detailed description of the remote sensed images

provided by Land observation satellites – a modern day boon to explorationists.

Although this book is primarily concerned with geological methods, in Chap. 9 a

brief overview is given of the more commonly used techniques of exploration geo-

physics and geochemistry. Finally, Chap. 10 discusses digital exploration data bases

and outlines the use of geographical information systems (GIS) and exploration

software for the storage, manipulation and presentation of digital exploration and

mining data.

This second edition has been greatly expanded from the original 1997 edition

to reﬂect changes that have taken place in exploration methods over last 10 years.

Basic geological ﬁeld techniques still constitute the core skill for the explorationist

and are the subject of a signiﬁcant part of the book. However new technological

advances have expanded the range of tools available to her. In diamond drilling,

faster and more reliable systems for orienting core have made this procedure almost

routine and have led to an increased awareness on the value to be got from quan-

titative structural logging. Satellite navigation systems have become much more

accurate thus expanding the role that GPS can play in providing survey controls

for detailed geological mapping, and the collection of geochemical and geophysical

data. New, very high resolution, commercial land observation satellites increasingly

offer imagery that rival the best of air photography both in resolution and price.

Preface vii

The desk top and laptop computers of today offer an almost exponential increase in

processing power, memory capacity and graphics ability which, combined with new

powerful software packages and sophisticated instrumentation, have revolutionised

traditional geophysical and geochemical techniques.

New software programs available today allow vast amounts of data to be pro-

cessed and analysed, and this leads to a tendency for the present day explorationist

to spend more time in front of a monitor than in the ﬁeld. Digital data, massaged and

presented as multi colour 3-D surfaces can acquire a life of its own, quite divorced

from the reality it is supposed to represent. There is an increasing danger that by

focussing on data handling the explorationist loses sight of the need for quality data

acquisition. The underlying philosophy behind much of this book is that, if geolog-

ical data is to be of value in ﬁnding ore bodies, ideas and insights must be used in a

structured way to control all stages of data handling from ﬁeld collection through to

ﬁnal presentation. In these days of electronic storage and processing of mass data,

it is worth remembering the well-known quote

Data is not information

Information is not knowledge

Knowledge is not understanding

Understanding is not wisdom

The book outlines some geological techniques for acquiring knowledge. The rest

is up to the reader.

Anonymous, but almost certainly adapted from: “Where is the wisdom we have lost in

knowledge? Where is the knowledge we have lost in information” (T.S. Eliot)

Acknowledgments

I am indebted to the many skilled ﬁeld geologists with whom I have been privileged

to work over the years and from whom I have acquired many of the exploration and

geological ideas, techniques and procedures that are described here. Among these

are: Ray Crawford, Neville George, Don Bowes, Frank Hughes, Dave McKenzie,

Don Berkman, Mike Rickard, Ilmars Gemuts, Doug Dunnet, John Thoms, Dick

Sillitoe and Gary Arnold.

The Australian Institute of Geoscientists kindly gave their permission to

reproduce a number of diagrams that previously appeared in AIG Handbook

5 – Structural logging of drill core – that I authored in 2001 (2nd Edition 2007).

The diagrams in question are 6.1, 6.6, 6.9, 6.10, 6.14, B.5, B.7, B.13, C.1, C.2 and

C.3. The permission of Ivanhoe Mining Limited and Newcrest Limited is acknowl-

edged to publish the descriptions of some of their exploration projects that appear

at the end of Chap. 4.

Geological maps and sections appearing in the book are based on actual projects

that the author has worked on. They have been re-drafted, modiﬁed and re-named

to make them suitable for this publication and to preserve their anonymity.

Gary Arnold kindly undertook to read a draft of the text and the book has ben-

eﬁted greatly from his many constructive comments. His input particularly into

Sect. 9.2 (magnetic surveys) and Sect. 10.3 (GIS and digital databases) is gratefully

acknowledged.

Needless to say, I accept full responsibility for all biases and errors that might

still remain in this work.