Table Of ContentIGNEOUS
PETROGENESIS
IGNEOUS
PETROGENESIS
Marjorie Wilson
Department of Earch Sciences, University of Leeds
~ Springer
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ISBN 978-0-412-75080-9 ISBN 978-94-010-9388-0 (eBook)
DOI 10.1007/978-94-010-9388-0
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This work is dedicated to my mother)
Blanche Pearce) for a lifetime of love
and understanding) and
to
Mary and Andrew
PREFACE
My main objective in writing this book has been to courses more petrogenesis-orientated are im
review the processes involved in present-day mag mediately confronted with a basic problem; the
ma generation and their relationship to global average student does not have a strong enough
tectonic processes. Clearly, these are fundamental background in geochemistry to understand the
to our understanding of the petrogenesis of ancient finer points of most of the relevant publications in
volcanic and plutonic sequences, the original tec scientific journals. It is virtually impossible to fmd
tonic setting of which may have been obscured by suitable reading material for such students, as most
subsequent deformation and metamorphism. authors of igneous petrology textbooks have de
Until fairly recently, undergraduate courses in liberately steered clear of potentially controversial
igneous petrology tended to follow rather classical petrogenetic models. Even the most recent texts
lines, based on the classification of igneous rocks, place very little emphasis on the geochemistry of
descriptive petrography, volcanic landforms, types magmas erupted in different tectonic settings,
of igneous intrusions and regional petrology . despite extensive discussions of the processes re
However, the geologist of the late 1980s requires, in sponsible for the chemical diversity of magmas.
addition, an insight into the fundamental processes Perhaps even more surprisingly, few texts have
which operate within the Earth, and are responsible attempted to relate igneous activity to global
for the diversity of igneous rocks presently ex tectonic processes, except at the most elementary
posed. Unfortunately, attempts to make petrology levels.
Vlll PREFACE
This book has arisen out of ten years of teaching much space to the discussion oftopics such as phase
igneous petrology to undergraduate and graduate diagrams and the fluid properties of magmas, as
students in the Department of Earth Sciences, these have been extensively covered in several
University of Leeds, UK, and the resultant frustra recent texts.
tion at having no appropriate text which discusses I would like to thank the following for their help
the geochemical characteristics of magmas in rela and encouragement throughout the completion of
tionship to their tectonic setting. It should appeal to this project: K. G. Cox for his much valued
the more advanced undergraduate and beginning comments on the original manuscript; P.J. Wyllie
postgraduate students, and their teachers, who and J.B. Gill for useful discussion of the format of
already have a basic foundation in petrological the book and the early chapters; my colleagues in
principles, including elementary geochemistry, the Department of Earth Sciences, G.R. Davies,
phase diagrams, mineralogy, regional geology and P.H. Nixon, E.H. Francis and R.A. Cliff, for their
global tectonics. The text has been deliberately put enthusiastic approach to all aspects of igneous
together in such a way that certain sections can be petrology which has led to many fruitful discus
omitted at first reading if the background of the sions; S. Caunt for word processing the large
student is not appropriate. Thus, for example, a number of references, and for much needed moral
beginning student could omit the more detailed support during the final stages.
sections on the trace element and isotope geo I have been fortunate to have had a particularly
chemistry of magmas generated in a particular lively group of research students over the past ten
tectonic setting. As far as possible, continuity in the years, including I. Luff, Z. Palacz, H. Downes,
presentation of data for individual provinces has J.P. Davidson, I. Wilson, D. Chaffey, S. Amini
been maintained for ease of inter-province com pari and S. Caunt, who have kept me on my toes. Many
sions. Thus, in each chapter, sections will be found people, including the above, have contributed to
covering, for example, major element, trace ele my ideas on igneous petrogenesis over the years, in
ment and radiogenic isotope geochemistry. particular R. Powell, J.D. Bell, S.W. Richardson,
Clearly, a text of this length cannot hope to cover K.G. Cox, M.J. O'Hara, P.E. Baker, C.J. Hawkes
all examples of a particular type of igneous activity. worth, M.J. Norry, the late P.J. Betton, I.S.E.
Consequently, I have tended to focus on volcanic Carmichael, A. Ewart, W. Hildreth, B.D. Marsh,
rocks from those recently active provinces for C. Bacon, H. Helgeson, G.M. Brown and C.H.
which we have the most comprehensive geochemi Emeleus.
cal data sets. Obviously, new data are appearing all Thanks must go finally to my family and friends
the time and therefore the shape of many of the for putting up with my reclusive habits over the
fields depicted in the geochemical variation dia past few months, especially to my mother, my sister
grams may change with time. Nevertheless, I Mary and her husband Andrew, my step-children
believe that we have reached a stage in our Jane and Gary (and step son-in-law David), the
understanding of the petrogenesis of igneous rocks latest addition to the family, my step-grandson
at which most of the fundamental principles are Anthony, and to Anne and Brian Frost. Thanks
well established. Consequently, the time is right for also to Roger Jones of Unwin Hyman for being
a text ofthis nature. I have deliberately not devoted such an understanding editor.
Marjorie Wilson
Leeds
ACKNOWLEDGEMENTS
We are grateful to the following individuals and (5.18); J. -G. Schilling and by pernusslOn from
organizations who have kindly given permission for Nature 313, Copyright © 1985 McMillan Maga
the reproduction of copyright material (figure zines Ltd (5.19,5.49); J.M. Edmond and Copy
numbers in parentheses): right © 1983 Scientific American, Inc. (5.23);
K. G. Cox (1.2, 3.23, 4.8, 4.9); G. Faure and by Figure 5.25 adapted by permission from Ito et al.,
permission of John Wiley & Sons (2.13); J. H. Acta 47, Copyright © 1983 Pergamon Journals Ltd;
Pearce and Elsevier (2.14); Elsevier (2.15, 2.16, J. R. Cann and Elsevier (5.27); E. G. Nisbet and
3.12, 5.26, 6.19, 8.7, 12.5); D.A. Wood and Royal Astronomical Society (5.28); J. F. G. Wilkin
Elsevier (2.17); P. J. Wyllie (3.5, 3.14, 3.19, 6.10); son (5.33); H. Staudigel and Elsevier (5.43, 5.44,
A. A. Finnerty and by permission of John Wiley & 5.45); A. Zindler and Elsevier (5.47); ]. C. Allegre
Sons Ltd (3.9); B. Harte (3.10); Lunar and Planet and Elsevier (5.48); P. J. Wyllie and by permission
ary Institute (3.13,5.31,6.15,9.10); A. Zindler and from Geological Society of America Bulletin 93 (6.3,
by permission from Nature 298, Copyright © 1982 6.11); J.B. Gill (6.4, 6.5, 6.9, 6.12, 7.6); H.K.
McMillan Magazines Ltd (3.16,3.17); G. C. Brown Acharya (6.6); R. N. Anderson and The Journal of
(3.18, 5.1, 5.3, 5.4, 5.8); H. S. Yoder Jr and Geology 88, Copyright © 1980, by permission of the
National Academy of Sciences (3.22); D. S. Barker University of Chicago Press (6.7, 6.8); V. Renard
(3.20); D. Green and by permission of the Director, and Elsevier (6.11); A. Ewart and by permission of
Bureau of Mineral Resources, Geology and Geo John Wiley & Sons Ltd (6.28, 6.30, 6.31); C. J.
physics, Canberra; Springer-Verlag (3.26, 3.27, Hughes and Elsevier (6.39); R. J. Arculus (6.40);
3.29); Figure 3.28 Copyright Mineralogical Society C. J. Allegre and by permission from Nature 299,
of America; R. N. Thompson and Carnegie Institu Copyright © 1982 McMillan Magazines Ltd (6.46);
tion of Washington (4.2); Z. A. Palacz and Elsevier Figures 6.47 and 6.48 reproduced with permission
(4.4,4.6); Figures 5.5 and 5.13 adapted from Earth from Annual Review of Earth and Planetary Sciences
(F. Press and R. Siever) by permission of W. H. 9, © 1981 Annual Reviews Inc; R. H. Pilger and by
Freeman and Company, © 1974, 1978, 1982 W. H. permission from Geological Society of America
Freeman and Company; M. G. Best (5.7, 5.24); Bulletin 93 (7.3); C. Condie and Copyright © 1982
R. D. Ballard and Elsevier (5.9,5.12); R. Hekinian Pergamon Books Ltd (7.8); P. J. Wyllie and The
and Elsevier (5.10,5.21,5.30); R. S. White and by Royal Society (7.9, 7.10, 7.11); W. S. Pitcher and
permission of the Geological Society (5.14); J. M. Blackie & Son (7.12); R. D. Beckinsale and Blackie
Sinton and Elsevier (5.16); S. Le Douaran and & Son (7.13); W. S. Pitcher (7.14); R. S. Harmon
Elsevier (5.17, 5.46); P. Thy and Springer-Verlag and by permission of the Geological Society (7.19,
x ACKNOWLEDGEMENTS
7.31); J. A. Pearce (7.25, 7.26); R. J. Stern and by and National Academy Press (10.6); F. Barberi
permission from Geological Society of America (11.2); C. E. Keen (11.4); J. D. Fairhead and
Bulletin 93 (8.1); A. J. Crawford and Elsevier (8.2); Elsevier (11.5); R. E. Long (11.7a); R. W. Girdler
Figure 8.11 adapted with permission from and Elsevier (11. 7b); Y. A. Sinno (11. 8); W.
Woodhead and Fraser, Acta 49 Copyright © 1985 Bosworth and by permission from Nature 316,
Pergamon Journals Ltd; K. C. Burke (9.1, 9.2, 9.4); Copyright © 1985 McMillan Magazines Ltd
E. M. Parmentier (9.6); A. B. Watts and by per (11.11); Figure 11.33 adapted with permission
mission from Nature 315, Copyright © 1985 from McDonough et ai., Acta 49, Copyright ©
McMillan Magazines Ltd (9.7); M. P. Ryan (9.8); Pergamon Journals Ltd; Plenum Press (12.3); C. B.
Figure 9.19 adapted with permission from Smith and the Geological Society of South Africa
Humphris et ai, Acta 49, Copyright © 1985 Per (12.14); S. C. Bergman and by permission of the
gamon Journals Ltd; S. R. Hart and by permission Geological Society (12.15); R. N. Thompson and
from Nature 309, Copyright © 1984 McMillan Springer-Verlag (12.18); A. LeRoex and by per
Magazines Ltd (9.27); Figure 9.31 adapted with mission from Nature 324, Copyright © 1986
permission from Kurz et al. , Nature 297, Copyright McMillan Magazines Ltd (12.19, 12.22); Figure
© 1982 McMillan Magazines Ltd; K. G. Cox and 12.21 adapted with permission from Nelson et aI.,
by permission from Nature 272, Copyright © 1978 Acta SO, Copyright © Pergamon Journals Ltd;
McMillan Magazines Ltd (10.1); M. A. Menzies G. Ferrara and Springer-Verlag (12.27); D. K.
and The Royal Society (10.3); K. G. Cox and Bailey and the Geological Society of South Mrica
Oxford University Press (10.4, 10.13); R. B. Smith (12.28, 12.29).
CONTENTS
PREFACE vu 2.3 Chemical variation diagrams 14
2.4 Geochemical characteristics of primary
ACKNOWLEDGEMENTS tx magmas 21
2.5 Isotopes as petrogenetic indicators 22
LIST OF TABLES xv 2.6 Geochemical criteria for the
identification of the palaeotectonic
SOME COMMON ABBREVIATIONS USED IN setting of ancient volcanic sequences 32
THE TEXT Xtx Further reading 34
CHAPTER THREE
PART ONE
Partial melting processes in the Earth's
Magmatism and global tectonic processes 1 upper mantle 37
3.1 Introduction 37
3.2 The physical state of the upper mantle 38
3.3 Chemical composition and mineralogy
CHAPTER ONE
of the upper mantle 44
Relation ofp resent-day magmatism to global 3.4 Partial melting processes in the upper
tectonic processes 3 mantle 58
3.5 The basaltic magma spectrum in relation
1.1 Introduction 3 to partial melting processes 67
1.2 Characteristic magma series associated 3.6 Segregation and ascent of magma 70
with specific tectonic settings 7 Further reading 72
Further reading 11
CHAPTER TWO CHAPTER FOUR
Geochemical characteristics of igneous rocks as Processes which modify the composition of
petrogenetic indicators 13 primary magmas 73
4.1 Introduction 73
2.1 Introduction 13 4.2 Convection and mixing in magma
2.2 Chemical analysis of igneous rocks 14 chambers 78
