BOOK REVIEW
IGNEOUS ROCKS AND PROCESSES:
A PRACTICAL GUIDE 1
Igneous Rocks and Processes is a large (22 × 28 cm), weighty (1.5 kg),
and thorough (428 pages) text/treatise on igneous petrology. The book
is divided into nine chapters and ancillary material. The aim of the
book “is to help students to develop appropriate descriptive and interpretative techniques … [with] a different order of priorities to those
that one would embrace in writing a book on petrogenesis” (p. vii). In
this reviewer’s opinion, Igneous Rocks and Processes contains more than
enough material to cover both aims at the intermediate level sought
by the author, Robin Gill.
The nine chapters are arranged in a logical order and constitute a veritable promenade down petrogeny’s lane, from the least to the most fractionated rocks. This structure is, however, interrupted by two chapters
(3 and 7) on processes. The fi rst chapter, at 19 pages, is the shortest. It
lays the groundwork for much of what is to follow: magmas and their
compositions, the classification and nomenclature of igneous rocks, and
the role of volatiles. The second chapter deals with basalts and related
rocks (but not gabbros). Treated are defi nitions, morphologies, alterations, and occurrences. These are interrupted by seven boxes that cover
minerals common in basalts, grain size, and norms. In chapter 3, the
author diverges from petrogeny’s lane and digs into binary and ternary
phase diagrams in considerable detail to elucidate magmatic differentiation. Again, boxes are used, with the fourth and fi nal one explaining
the basics of isotopes. The author returns to the rocks in chapter 4, now
treating the gabbros. He discusses layering, the significance of textures,
where gabbroic intrusions occur, and fi nally, the knotty anorthosite
problem. A half-dozen boxes deal with optical data and procedures.
Chapter 5 covers ultramafic and ultrabasic rocks, with a detailed treatment of komatiites, picrites and others particularly rich in magnesium.
Spinels, garnets, ophiolites, and greenstone belts are dealt with in four
of the six boxes in the chapter. Andesite, dacite, and rhyolite, the characteristic rocks of supra-subduction volcanism (but not exclusively so),
are the subjects of chapter 6. These three rocks are contrasted in Table
6.1. Varieties also discussed include basaltic andesite, boninite, and adakite. The range of interpretations surrounding subduction, including
flat-slab zones, are varied and complex. Six boxes break up the chapter.
In chapter 7, the author turns to processes and products, chiefly pyroclastics. This chapter opens with a useful comparison of the five styles
of eruption (Table 7.1) and carries on through extensive and interesting
descriptions. Although the mechanics of volcanic eruptions were fi rst
discussed by Pliny the Younger nearly two millenia ago, much remains
to be explained adequately. Chapter 8 (with five boxes) deals with the
most abundant intrusive rocks in the Earth’s crust: the granitoids.
A long (pages 248–256) and detailed discussion of batholiths—their
aspects, “granitization”, their forms at depth—is nicely depicted in
Figure 8.9. This is followed by summaries of structures, textures, and
late-stage processes in granitoids. Extensive coverage of the chemical
and isotopic characteristics of granitoids as well as the distinctions
between I-, S-, and A-types (Table 8.3.l) conclude the chapter. Curiously,
the least common igneous rocks take up the longest chapter of the book.
The ninth chapter (pages 291–346, 16% of the text) is devoted to the
alkali rocks, which make up <1% of exposed igneous rocks (page 291).
Many of the early pages of the chapter are taken up by the complex
and confusing nomenclature of the alkali rocks. Your reviewer, however, would be loathe to include quartz monzonite with the alkali rocks
(Table 9.3). The bulk of the chapter, dealing with the varied occurrences
of alkali rocks and backed up with appropriate phase diagrams, shows
the enormous petrologic complexity of this group and substantiates
the length of the chapter, which alone could easily make up a semester-
length course. Nine boxes
in the chapter deal with
mineralogical, petrologic,
and chemical topics.
Three appendices follow
chapter nine: A. Mineral
identification using a
polarizing microscope
(pages 347–357, an entry
“intended merely as
a reminder, not as an
introductory course.”), B.
Petrographic calculations
(7 pages), and C. Symbols,
units, and constants used
(2 pages). The book closes
with a 15-page glossary (~450 terms on 15 pages), answers to the questions posed at the close of each chapter, an extensive bibliography (~500
entries on 19 pages), and a 14-page general index.
Although relatively free of errors, some must not pass unnoticed.
Particularly annoying is the cavalier use of the slash, such as “SiO2 /
mass %” (Fig. 1.2), “Temperature/oC”, “Pressure/Gpa” and even “height/
km”, “depth/km”, and “gravity anomaly/mgal” (Fig. 8.7). The use of
“coarse-grained” is incorrect. Gabbro is “a coarse-grained igneous
rock” (p. 93), granite is “a coarse-grained … rock” (p. 242) and so on
throughout the text. Certainly your reviewer has mapped multitudinous
medium- and fi ne-grained gabbros, granites, and many other intrusive rocks. The sizes of granitoid intrusions (Table 8.3) are confusing.
What do 12 × 12 km2, 800 × 25 km 2, and 1600 × 65 km 2 mean? Many
of the large-scale maps lack north arrows; a reader in Uruguay might
have a different view than a Canadian. The low totals of the two analyses in Table 9.4 are perplexing. Why the author chose RRM (“relative
molecular mass”, p. 38) and a.m.u. (“atomic mass unit”, p. 92) rather
than the familiar atomic weight is evident to him alone. Finally, differences in numeration of figures, figures in boxes, and plates (i.e. Fig.
5.1, Fig. 5.1.1, and 5.1) lead to confusion.
A personal peeve is the absence of a discussion of the consequences of
subglacial eruptions of “gentle,” effusive basaltic magma. The eruption
in Iceland of Eyjafjallajökull under its icy cover in April, 2010, shut
down air travel over Europe for more than a week. Eyjafjallajökull’s
larger neighbors to the northeast, Mýrdalsjökull and Vatnajökull, offer
catastrophic potential. Then we have (p. 94): ‘In older literature magnesian orthopyroxenes were divided into enstatite (En90-100 ), bronzite
(En70-90 ), and hypersthene (En50-70 ). Current usage includes all of these
in the term “enstatite” (En50-100 ).’ This change may please chemists,
but certainly not geologists. At least time-honoured “sphene” has survived (page 351).
On the plus side, Igneous Rocks and Processes is clearly written, the
Michel-Lévy chart of interference colours is superb, and the splitting of
photomicrographs into halves, one in plane-polarized light, the other
under crossed nicols, is highly effective. Some specific data are supported by cited websites.
Would I use this text were I again to teach undergraduate igneous
petrology? Yes, but with caveats. Igneous Rocks and Processes is thorough and complete. Nevertheless, a careful choice of topics (“weeding”)
would be necessary to keep an undergraduate course within realistic
limits. Such would add an extra burden on the teacher. Finally, to use
a text as rigorous as this one, the student must have a solid semester
of optical mineralogy, theory and labs under his belt.
Tomas Feininger, Université Laval, Québec, Canada
1 Gill R (2010) Igneous Rocks and Processes: A Practical Guide. Wiley-Blackwell,
Chichester, UK, 440 pp, ISBN 978-06320-6377-2, $144 (hardcover), $90
(softcover)
E LEMENTS
140
A PR IL 2011
BOOK REVIEW
DIFFUSION IN MINERALS AND MELTS 2
Diffusion in Minerals and Melts is volume 72 in the popular Reviews
in Mineralogy & Geochemistry series of the Mineralogical Society of
America and the Geochemical Society. It continues the series’ successful tradition of collecting review articles on topics with a common
theme written by top experts in the field. Like most other books in the
series, Diffusion in Minerals and Melts is rooted in a short course, this
one organized by the book’s two editors, Youxue Zhang and Daniele
Cherniak, and held just prior to the 2010 Fall Meeting of the American
Geophysical Union.
The goal of this volume is an ambitious one. As they state in their
introductory chapter, the editors sought to “compile, compare, evaluate
and assess diffusion data … for all elements in minerals and natural
melts (and glasses)” with the aim of helping readers “to understand
the basics of diffusion and applications to geological problems.” An
explosion of interest in the kinetics of geological systems over the last
decade or two has stimulated great demand for high-quality diffusion
data, leading to a wealth of new experimental results. Along with those
results have come important advances in theoretical approaches to the
treatment of diffusion data, and increasingly diverse and widespread
geological applications. The attempt made in this volume to corral and
evaluate the abundant new data and novel concepts that have emerged
in recent years is therefore challenging, but timely.
With 23 chapters and 26 authors, and with hundreds of figures and
thousands of references, the 1038 pages in this book allow an extensive treatment of the subject matter. In fact, the potential exists for
a reader to be overwhelmed by the sheer breadth of topics and their
complexity, but the volume is obviously intended more as an occasional
reference than as a treatise to be read cover to cover. Most persons
drawn to the book will likely have immediate interests focused on only
a subset of the wide-ranging menu of choices, and the overall organization of the volume and its careful internal subdivision of individual
chapters should make it possible for such readers to zero in quickly on
relevant topics.
The volume opens with three introductory chapters of general interest
on theory, new experimental methods, and analytical techniques. These
are followed by five lengthy chapters on diffusion in melts and glasses
and ten mostly shorter chapters on diffusion in minerals. Four additional chapters cover trends in diffusion data for minerals, diffusion
in polycrystalline materials, computational approaches, and geological
applications.
The discussion of diffusion theory that opens the book is concise
yet wide-ranging. It mirrors treatments of fundamental ideas available elsewhere but connects strongly to geological examples. The following chapter on experimental methods highlights “non-traditional
and emerging” techniques and eschews description of older classical
approaches, although those are covered to some degree in later chapters. The section on analytical techniques might have been improved
by de-emphasizing discussion of the instrumental and analytical details
(information that is easily available elsewhere in more complete and
useful forms) and accentuating instead the specific utility of each technique in the determination of diffusivities. In some instances, examples
from the literature are indeed provided to illustrate the application of
these techniques to diffusion studies; if that had been done in all cases,
it would have added further value to the chapter.
The treatment of diffusion in silicate melts encompasses three extensive data compilations: one for H, C, and O components; one for noble
gases; and one of extraordinary breadth for essentially all other major,
2 Zhang Y, Cherniak DJ (eds) (2010) Diffusion in Minerals and Melts. Reviews in
Mineralogy & Geochemistry 72, Mineralogical Society of America, Chantilly, VA,
1038 pp, ISBN 978-0-939950-86-7, $50 (25% discount for MSA. GS, and CMS
members)
E LEMENTS
minor, and trace elements for
which data exist on diffusion in
silicate melts. These compilations
are complemented by an exposition of the theory of multicomponent diffusion in melts, with
illustrative experimental results
and geological applications, and
by a largely theoretical analysis of
models for self-diffusion in silicate melts. This segment of the
book does not shy away from
addressing the essential complexity of diffusion in melts,
and it defi nes clearly the current
boundaries of our understanding.
The daunting task of creating a comprehensive compilation of diffusion data for minerals is tackled in a set of chapters that fi rst address
diffusion of hydrogen, oxygen, and noble gases across a wide suite of
minerals, and then consider diffusion of cations (and a few other species) in a large number of mineral groups, each taken in turn. These
chapters assemble most or all of the available diffusion data for the elements and minerals covered. The assessment and evaluation of those
data, however, are uneven: whereas some chapters carefully compare,
contrast, and appraise the assembled results, others simply compile
them and offer little in the way of detailed examination of their value.
The concluding chapters include (1) an original and thought-provoking
overview that seeks to uncover general trends in diffusion data for
minerals, (2) a synoptic analysis of grain-boundary diffusion in polycrystalline materials, (3) an enlightening survey of methods and results
obtained from computational approaches, and (4) a brief and thus
highly selective summary of common applications of diffusion data
to geologic problems.
The shortcomings of this volume are few. More attention could have
been given to linking experimentally measured rates and trends to
nanoscale processes and mechanisms, in order to illuminate the underlying causes of observed variations in diffusivities; this is done to some
degree in the chapters on computational models of diffusion and on
self-diffusion in melts, and it is touched on in a few other instances, but
an overall lack is felt elsewhere. One modest topical omission is a treatment of intergranular diffusion in fluid-mediated systems: the chapter
on grain-boundary diffusion in polycrystalline materials focuses almost
exclusively on anhydrous systems, leaving unaddressed the important
process of intergranular diffusive transport in common metamorphic
environments. Finally, review volumes such as this present rare opportunities to assess the current state of the art and to point the way forward, directing new research in the most fruitful directions. Although
a few individual chapters address this issue effectively, more commonly,
the opportunity was missed.
Overall, this volume is a substantive addition to the reference literature, in keeping with past successes in the series. The editors largely
achieved their goal of gathering together the voluminous but widely
dispersed data on diffusion in geological materials, and they have also
made progress toward assessing those data critically and placing them
in the context of their geological applications. These achievements,
when combined with the low price of the volume—especially considering the discount available to members of the Mineralogical Society
of America, the Geochemical Society, and allied groups—should earn
it a place on the bookshelf of any student or researcher enthused by
diffusion in geological materials.
William D. Carlson, University of Texas at Austin, USA
141
A PR IL 2011