Dunn Colin E. Biogeochemistry in Mineral Exploration

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Tin (Sn) . ...................................... 314

Titanium (Ti) . .................................. 316

Tungsten (W) . .................................. 316

Uranium (U) . .................................. 317

Vanadium (V). .................................. 320

Ytterbium (Yb) .................................. 321

Yttrium (Y) . . .................................. 321

Zinc (Zn) ...................................... 322

Zirconium (Zr) .................................. 324

Chapter 10. Data Handling and Analysis. .......................... 327

First estimation of the data . .......................... 327

Computer software tools . . . .......................... 330

Data analysis . . . .................................. 331

Univariate statistics . .............................. 332

Bivariate statistics . . .............................. 335

Multivariate analysis .............................. 335

Map plots of data distributions . . ...................... 338

Unusual concentrations of selected elements . .............. 339

Analytical artefacts . .............................. 339

Sampling and sample preparation artefacts .............. 340

Contamination of the natural environm ent .............. 340

Species-speciﬁc enrichments . . . ...................... 341

Chapter 11. Case Histories . . .................................. 343

Gold . .......................................... 344

Canada: La Ronge and Glennie Domains, Northern

Saskatchewan . . . .............................. 344

Rod Zone – Jolu Mine – La Ronge

Domain . . .................................. 344

Geology and mineralization . . .................. 344

Biogeochemical survey . . ...................... 345

Post survey exploration . ...................... 345

Jasper pond . . . .............................. 345

Geology and mineralization . . .................. 345

Biogeochemical surveys . ...................... 346

Post survey development ...................... 347

Seabee Mine, Laonil Lake . ...................... 347

Geology and mineralization . . .................. 347

Biogeochemical survey . . ...................... 348

Post survey developments . . . .................. 348

Canada: Temperate forest of British Columbia

QR (Quesnel River) deposit...................... 349

Geology and mineralization . . .................. 349

Contents

Environment. .............................. 349

Scope of survey and analysis . .................. 349

Results . .................................. 349

South America: Peru–Ecuador Bor der . . .............. 350

Cordillera del Co

ndor

Geology and mineralization . . .................. 350

Environment. .............................. 351

Scope of survey and analysis . .................. 351

South America: Bolivia

and Argentina . . . .............................. 356

Geology and mineralization . . .................. 356

Environment. .............................. 356

Biogeochemical surveys . ...................... 356

Summary of results from the orientation surveys . . . . . 360

Platinum group metals/nickel /copper . . .................. 361

Canada: Rottenstone Lake, northern Saskatchewan . . . . . . 361

Geology and mineralization...................... 361

Environment . . .............................. 362

Exploration history. . .......................... 362

Biogeochemical surveys . . . ...................... 363

Post survey exploration . . . ...................... 366

Summary notes .............................. 366

Nickel . . ...................................... 366

Canada: Thompson Nickel Belt, Northern Manitoba . . . . . 366

Geology and mineralization...................... 366

Environment . . .............................. 366

Biogeochemical survey . . . ...................... 367

Post survey exploration . . . ...................... 372

Uranium ...................................... 373

Canada: Athabasca Basin, Northern Saskatchewan. . . . . . . 373

Geology and mineralization...................... 373

Exploration history. . .......................... 373

Environment . . .............................. 374

Biogeochemical surveys . . . ...................... 374

Subsequent discoveries . . . ...................... 380

Summary notes .............................. 381

Kimberlites. . . .................................. 381

Canada: Ekati Trend, Lac de Gras, Northwest Territories. . 381

Geology. . .................................. 381

Environment . . .............................. 382

Biogeochemical survey . . . ...................... 382

South Africa: Kimberley.......................... 384

Geology. . .................................. 384

Contents

Environment . . .............................. 386

Biogeochemical surveys . . . ...................... 386

Expanded surveys – summary observations . .......... 387

Canada: Buffalo Head Hills, North-Central Alberta . . . . . . 388

Geology. . .................................. 388

Exploration history. . .......................... 389

Environment . . .............................. 390

Biogeochemical survey . . . ...................... 390

Kimberlites – summary .......................... 391

Chapter 12. Exploration Geomicrobiology – The New Frontier . .......... 393

Introduction...................................... 393

Signiﬁcance of micro-organisms as biogeochemical agents . . . . . 394

Methods for identifying micro-organisms and microbial

processes . . ...................................... 397

Culture-dependent techniques. . ...................... 397

Culture-independent methods . . ...................... 399

Molecular procedures . .............................. 399

Extraction and puriﬁcation of nucleic acids from soils . . . . . . 399

Ampliﬁcation of target genes from extra cted DNA or RNA. . . . 400

Assessing genetic diversity .......................... 402

Genetic ﬁngerprinting . . . .......................... 402

Case studies ...................................... 403

Case Study 1 – The geomicrobiological cycling of gold. . . . . . 403

Case Study 2 – Microbial diversity in soils and sediments

contaminated with Zn and Cu . ...................... 409

Case Study 3 – Bacterial biosensors as alternatives for

measuring heavy metals in soil extracts . . . .............. 410

Future technologies for bio-prospecting .................. 410

Conclusions ...................................... 413

Chapter 13. A Look to the Future . .............................. 415

Introduction...................................... 415

Hyperspectral imagery in relation to biogeochemistry . . . . . . . . 415

Exploration geomicrobiology.......................... 417

Forensic biogeochemistry . . .......................... 417

Plant mineralogy .................................. 418

Chemical analysis .................................. 418

Concluding remarks . . .............................. 419

References . . .............................................. 421

Botanical Index . . .......................................... 451

Subject Index .............................................. 455

Contents of CD . . .......................................... 461

XII

Contents

EDITOR’S FOREWO RD

The publication of this volume marks a milestone for the series. As part of the

preamble to the ﬁrst volume, published just over 25 years ago, my predecessor and

founding editor of the series, Gerry Govett, listed the titles of the volumes he en-

visaged in the series. These would build a comprehensive set of handbooks coveri ng

the various operational techniques used in exploration geochemistry (drainage,

regolith, etc.), the methods used in geochemical analysis and the statistics used for

extracting exploration information. The realization of this latest volume, dealing

with the use of biogeochemistry in mineral exploration, completes his vision.

This volume reveals that the trace element content of plant tissues offers a val-

uable and probably underused tool in the armoury of the exploration manager.

A successful survey, however, rests on bringing together a wide spectrum of mul-

tidisciplinary knowledge and a careful adherence to operational protocols. Different

species concentrate different trace elements to different degrees in different tissues.

Species selection in climatic and geographic zones ranging from boreal forests to

humid tropics to deserts is considered. Sampling and sample preparation call for

meticulous contamination-avoidance precautions due to the very low concentrations

of trace elements found in plant tissues. On the other hand, recent advances in

analytical instrumentation now make the determination of these low concentrations

relatively straightforward and routine. The same advances are opening possibilities

to determine an even wider range of elements in plant tissues. A fascinating source of

biogeochemical data is the plants of the climate-controlled bio-domes of the Eden

project in southwest England. The biogeochemical behaviour of most elements of the

periodic table is catalogued in this volume and a unique bibliography of biogeo-

chemistry in mineral exp loration is included. Case histories describing biogeochem-

ical surveys in exploration for gold, platinum group elements, nickel, uranium and

kimberlites illustrate the practical application of biogeochemistry. Going beyond this

thorough review of the current state-of-the-art, a well-founded glimpse into future

developments includes the potential of both biogeochemistry and geomicrobiology in

mineral exploration.

The content fully reﬂects the fact that the author, Colin Dunn, is supremely

qualiﬁed to contribute an expert volume on biogeochemistry in mineral exploration.

One of the features of this volume that I ﬁnd – and I hope other readers ﬁnd – most

striking and exciting is the way in which it is imbued with his personal experience.

Furthermore, Colin Dunn has not only devoted much of his career to the application

of biogeochemistry to mineral exploration, but also, in the course of his career, met

and worke d with almost all of the other scientists who made notable contributions to

biogeochemistry during the second half of the 20th century. Not surprising then, that

the incisive knowledge and distilled wisdom to be found in this volume are unsur-

passable.

Martin Hale, The Netherlands

January 2007

xiv

Editor’s foreword

PREFACE

To a large extent, this book is a personal odyssey through almost 30 years of

biogeochemical research, involving many tens of thousands of samples and millions

of analytical determinations. It aims at emphasizing the practical aspects of ﬁeld

operations and the precautions that need to be taken, with details of sample prep-

aration, choice of analytical method and data interpretation. The pitfalls that may be

encountered along the way are indicated, with the intention of making this a ref-

erence book and a true handbook of the how, why, when, what and where to proceed

with a mineral exploration survey using plant tissues. ‘Case History’ accounts from

around the world provide follow-up results of a number of surveys directed towards

precious metals, base metals, uranium and diamondiferous kimberlites.

This book has a different bias from the comprehensive texts dealing with similar

subject matter by Brooks (1983), Kovalevsky (1987), Kabata-Pendias and Pendias

(1992), Brooks et al. (1995) and Kabata-Pendias (2001). Its coverage is significantly

different from the ‘classic’ biogeochemical studies involving mostly the fundamental

building blocks of biogeochemistry (C, H, N, O) that are comprehensively dealt with

in ‘Biogeochemistry’ edited by William Schlesinger (2005) as Volume 8 of the parallel

series of books by Elsevier entitled Treatise on Geochemistry. These valuable texts

should be used for further details on the composition of a wide range of plants,

foodstuffs and soils. There is no discussion of foodstuffs in the present text, because

the intention is to focus upon those common, naturally occurring plant species that are

widespread throughout a survey area, and can therefore be systematically collected

and analysed to determine the spatial relationships of elements to a mineralized target.

This book is aimed at the geologist. When working in the ﬁeld with some bot-

anists I have received looks of incredulity when I have asked the name of a plant that

I continually see and which appears to be, therefore, of potential value for mineral

exploration. To many botanists it is only the unusual plants that are of particular

interest, and so to them my question seems frivolous and redundant, yet these

common plants represent the key species of value in the biogeochemical exploration

for mineral deposits.

As geologists we have our own vocabulary of c omplex terms and in general we

seek to simplify the other sciences that impinge upon our geological knowledge. With

this in mind a number of terms are expressed here in a language that is more com-

patible with the geologist than the chemist; in the tables, elements are listed in

alphabetical order of their chemical symbols, rather than grouped together in some

other chemically coherent format; and in Chapter 9, the descriptions of the element

characteristics of plants are arranged in alphabetical order of their element name.

Concentrations are expressed as parts per million (ppm) and parts per billion (ppb),

rather than what are to most geologists the more complex chemical units of mgg

–1

mgkg

–1

or ng g

–1

More than 20 years ago, after some significant relationships between plant

chemistry and mineralization had been revealed, I asked an exploration manager if

he was considering using the biogeochemical method to assist in his exploration

programme. His response was ‘No – quite frankly it scares the heck out of me,

because I don’t understand it’. By which he meant that the numbers tend to be

different from soil s, and there are other considerations to be taken into account when

interpreting the data. Subsequently, many studies and present ations have been de-

signed to try and simplify the complex world of plant chemistry as it relates to

minerals concealed in the ground. To this end, the ﬁrst biogeochemical exploration

short course that was sponsored by the former Association of Exploration Geo-

chemists (now the Association of Applied Geochemists) was entitled ‘Biogeochemical

Exploration – Simpliﬁed’. In this the expertise of a ‘botanist–biogeochemist’ (Jim

Erdman), a ‘chemist-geochemist’ (Gwendy Hall) and two ‘geologist–biogeochemists’

(Shea Clark Smith and myself) was brought together at a conference in Phoenix to

present our combined knowledge, with the emphasis on exploration in arid terrains.

Subsequently, I have had the good fortune to work with several of the world’s ‘old

school’ of biogeochemists (Harry Warren, Robert Brooks, Alexander Kovalevsky) of

whom none are with us today, and to meet and discuss details with many other

fundamental contributors to bioge ochemistry in mineral exploration including Nils

Brundin, Hans Sha cklette, Helen Cannon, Jim Erdman, Don Hornbrook, John

Fortescue and more recently Shea Clark Smith, Mark Fedikow, David Cohen and

Ken Lovstrom. Peter Rogers (Chavin Consulting), a long-time colleague with whom

I have collaborated on many projects, was instrumental in helping to launch a

number of large biogeochemical surveys in Nova Scotia and elsewhere, and has

provided valuable input to the content and structure of several chapters.

Two friends and colleagues deserve special mention for their immense contribu-

tions to my understanding of the non-geological aspects of biogeochemistry. For

much of the detailed chemistry outlined in Chapters 6 and 7, I have lent heavily on

the comprehensive knowledge of Gwendy Hall at the Geological Survey of Canada

(GSC) with whom I have had the good fortune to work on many projects over the

past 20 years. With her kind permission, I have quoted from many of her publi-

cations and my text has beneﬁted from her critical reviews of those two chapters.

Similarly, for botanical aspects of Chapter 2, I have based much of my text on

publications and discussions with Rob Scagel (Paciﬁc Phytometric Consultants,

Surrey, BC). Thanks to many ﬁeld sessions with Rob, I have learnt almost everything

I now know about botany and forestry. The three of us have collaborated on pro-

ducing a number of workshops and publications (e.g., Dunn et al., 1993a).

Over the years, the generous support and encouragement of managers at the

Saskatchewan Geological Survey and the Geological Survey of Canada have greatly

assisted in facilitating ﬁeld programmes and providing the resources to acq uire large

xvi

Preface

amounts of analytical data. Subsequently, while consulting for a number of com-

panies and organizations I have accumulated vastly more data, and these companies

have recently granted permission for me to release a considerable amount of the

information contained within this book. I thank, in particular the exploration man-

agers, past and present, with Angl o American, AngloGold-Ashanti, BHP Billiton,

Falconbridge, Noranda, Merit Mining, Placer Dome, Uravan Minerals and the

companies that have granted this permission.

It was late in 1992 that Dr. Gerry Govett, as editor of the series ‘Geochemistry in

Mineral Exploration’, sent me a letter enquiring as to whether I might be interested

in compiling a book on biogeochemistry in mineral exp loration. Although my in-

terest was high, other commitments precluded for many years any concrete action to

produce this book, but the seeds of thought were sown and it encouraged me to

steadily accumulate the various pieces of information required for ultimately achiev-

ing this goal. After an early retirement from the GSC in 1998, I was able to further

develop my ideas, but it was not until the end of 2003 after a decade of gentle

persuasion from Gerry that a contract with Elsevier was ﬁnally signed. In the interim,

Dr. Martin Hale took over the reins as Series Editor and my sincere gratitude goes to

Martin for his enormous help in keeping me on track throughout the writing process.

To all of the above, and to the many more individuals with whom I have worked

and discussed problems over the years, I extend my sincere gratitude.

For those seeking more information than that provided in these pages, there is a

CD in the back pocket that contains data listings, a complete study on halogens in

plants and soils (courtesy of Geoscience BC), and abstracts of all papers (about 130)

published in the Journal of Geochemical Exploration (JGE – 1972–2007) on biogeo-

chemical and geobotanical studies directed towards mineral exploration. The JGE is

a primary source of such information, and the digital abstracts each have a hyperlink

to Elsevier’s website and access to the full papers.

The compilations of data selected to illustrate various topics are drawn primarily

from large personal databases, and although there are many pages of references,

discussion revolves mainly around projects with which I have had personal involve-

ment. I have not been able to give full credit to the many individuals involved in

developing this science, but references are provided to all those that I have been able

to track down. This assemblage of words, ﬁgures, tables, digital listings and refer-

ences is designed for ‘one-stop shopping’ with respect to information on biogeo-

chemistry in mineral exploration. Inevitably, it is a ‘work in progress’. The intention

is to provide a ﬁeld manual and a source of reference. It is hoped that the infor-

mation contained within these pages will help to spark new ideas, and provide a

stepping-stone towards further development of the intriguing and ever-surprising

interactions among the sciences of geology, botany and chemistry.

Colin E. Dunn, Sidney, BC, Canada

3 January 2007

xvii

Preface

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Chapter 1

INTRODUCTION

SETTING THE SCENE

Vascular land plants have been evolving for over 425 million years. During that

long period they have adapted to survive a remarkably wide range of both physical

and chemical conditions. Mechanisms have evolved to absorb and scavenge chemical

elements and translocate them through roots into stems, twigs, bark, foliage, ﬂowers,

cones and seeds. Some species have developed defences that screen and exclude at the

soil/root interface, or at barriers within a plant, those elements that are either not

required for metabolic function or are harmful to development. Other species

accumulate selected elements and use them to ward off insects and/or diseases. For

example, the Douglas-ﬁr has a propensity to accumulate arsenic. Since there is no

known metabolic function for this usually toxic element it can be assumed that, until

shown otherwise, it is using the arsenic as a defence against either predatory creatures

or diseases. Thus , the enrichment of arsenic in Douglas-ﬁr is a facet of knowledge

that can be used to advantage by the mineral explorationist, since arsenic is so

commonly associated with many metal deposits, especially gold.

The plant can be viewed as a sophisticated geochemical sampling device, as yet

not fully understood. An extraordinary wealth of information on plant chemistry is

scattered throughout the literature of botanists, plant chemists and geochemists. In

spite of this, although past its infancy, the application of biogeochemical methods to

mineral exploration must be considered to be only in the early stages of maturity.

There is much that we have yet to establish. As research progresses on conditions

that control the accumulation of elements by plants, and as ﬁeld studies continue to

augment the databases on plant ch emistry, the role of the plant in mineral explo-

ration programmes becomes increasingly important.

BIOGEOCHEMISTRY AND GEOBOTANY

General considerations and distinctions

As the name implies, ‘biogeochemistry’ involves the integration of the three sci-

ences – biology, geology and chemistry. With minor exceptions, the ‘biology’ com-

ponent involves the plant kingdom, i.e., botany, and not the animal kingdom, i.e.,

zoology. Consequently, the term ‘phytogeochemistry’ (from the Greek word for