Download When the Continental Crust Melts - Elements

August 2011
Volume 7, Number 4
ISSN 1811-5209
When the Continental
Crust Melts
EDWARD W. SAWYER, BERNARDO CESARE, and MICHAEL BROWN, Guest Editors
How the Crust Gets Really Hot
Melting Experiments and
Thermodynamic Calculations
Interpreting Microstructures
Crustal Melting and the Flow
of Mountains
Melt Flow through
the Crust
www.elementsmagazine.org
www.elements.
geoscienceworld.org
When the Continental Crust Melts
Guest Editors: Edward W. Sawyer, Bernardo Cesare, and Michael Brown
229
235
When the Continental Crust Melts
Edward W. Sawyer, Bernardo Cesare,
and Michael Brown
How Does the Continental Crust
Get Really Hot?
ABOUT THE COVER:
Spider Wall on the south face
of Nuptse (the summit ridge
is at ~7650 m, and the wall is
~1700 m in height), showing a
network of leucogranite dykes
in metasedimentary rocks of
the Everest Series (centre)
above the Nuptse leucogranite,
visible at the bottom left and
right. Leucogranites emplaced
in the shallow crust are the end
product of melting of the deep
crust in orogenic belts. The
view is from Pokalde Peak in
the Khumbu Himalaya, Nepal.
IMAGE COURTESY OF MICAH JESSUP,
UNIVERSITY OF TENNESSEE, USA
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Chris Clark, Ian C. W. Fitzsimons, David
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Elements is published six times a year. Individuals
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All rights reserved. Reproduction in any form,
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Printed in USA
ISSN 1811-5209 (print)
ISSN 1811-5217 (online)
Volume 7, Number 4 • August 2011
grt bt kfs pl
Elements is published jointly by the Mineralogical
Society of America, the Mineralogical Society
of Great Britain and Ireland, the Mineralogical
Association of Canada, the Geochemical Society,
The Clay Minerals Society, the European
Association of Geochemistry, the International
Association of GeoChemistry, the Société
Française de Minéralogie et de Cristallographie,
the Association of Applied Geochemists,
the Deutsche Mineralogische Gesellschaft,
the Società Italiana di Mineralogia e Petrologia,
the International Association of Geoanalysts,
the Polskie Towarzystwo Mineralogiczne
(Mineralogical Society of Poland), the Sociedad
Española de Mineralogía, the Swiss Society of
Mineralogy and Petrology, and the Meteoritical
Society. It is provided as a benefit to members of
these societies.
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247
Is the Crucible Reproducible?
Reconciling Melting Experiments
with Thermodynamic Calculations
Richard W. White, Gary Stevens, and Timothy E. Johnson
Melted Rocks under the Microscope:
Microstructures and Their Interpretation
Marian B. Holness, Bernardo Cesare, and Edward W. Sawyer
253
Crustal Melting and the Flow of Mountains
261
Organizing Melt Flow through the Crust
Rebecca A. Jamieson, Martyn J. Unsworth, Nigel B. W. Harris,
Claudio L. Rosenberg, and Karel Schulmann
Michael Brown, Fawna J. Korhonen, and Christine S. Siddoway
D E PA R T M E N T S
Editorial – Is Science a Contact Sport? . . . . . . . . . . . . . . . . 219
From the Editors – John Valley, Principal Editor 2012–2014. . 220
The Elements Toolkit – Smashing Up Stones . . . . . . . . . . . 221
People in the News – Williams-Jones, Ferry, Stolper. . . . . . . 222
Meet the Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
Society News
Swiss Society of Mineralogy and Petrology . . . . . . . . . . . . . . 267
Association of Applied Geochemists . . . . . . . . . . . . . . . . . . .268
Mineralogical Society of Great Britain and Ireland . . . . . . . 269
International Association of GeoChemistry . . . . . . . . . . . . . .270
European Association of Geochemistry . . . . . . . . . . . . . . . .271
The Clay Minerals Society . . . . . . . . . . . . . . . . . . . . . . . . . . .272
The Meteoritical Society . . . . . . . . . . . . . . . . . . . . . . . . . . . .273
Mineralogical Society of America . . . . . . . . . . . . . . . . . . . . 274
International Association of Geoanalysts . . . . . . . . . . . . . . . . 276
Société Française de Minéralogie et de Cristallographie . . .277
Geochemical Society . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278
Mineralogical Association of Canada . . . . . . . . . . . . . . . . . 280
Book Review – Timescales of Magmatic Processes . . . . . . . . . . 282
Meeting Report – Making Science Matter . . . . . . . . . . . . . 284
Calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
Advertisers in This Issue . . . . . . . . . . . . . . . . . . . . . . . . . 286
Parting Shots – Standing Stones . . . . . . . . . . . . . . . . . . . . 288
217
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218
A UGUS T 2011
EDITORIAL
IS SCIENCE A CONTACT SPORT?
PRINCIPAL EDITORS
HARRY Y. (Hap) McSWEEN, University of
Tennessee, USA ([email protected])
JAMES I. DREVER, University of Wyoming, USA
([email protected])
GEORGES CALAS, IMPMC, France
([email protected])
ADVISORY BOARD 2011
JOHN BRODHOLT, University College London, UK
NORBERT CLAUER, CNRS/UdS, Université de
Strasbourg, France
WILL P. GATES, SmecTech Research
Consulting, Australia
GEORGE E. HARLOW, American Museum
of Natural History, USA
JANUSZ JANECZEK, University of Silesia, Poland
HANS KEPPLER, Bayerisches Geoinstitut,
Germany
DAVID R. LENTZ, University of New Brunswick,
Canada
ANHUAI LU, Peking University, China
ROBERT W. LUTH, University of Alberta, Canada
DAVID W. MOGK, Montana State University, USA
TAKASHI MURAKAMI, University of Tokyo, Japan
ROBERTA OBERTI, CNR Istituto di Geoscienze
e Georisorse, Pavia, Italy
TERRY PLANK, Lamont-Doherty Earth
Observatory, USA
XAVIER QUEROL, Spanish Research Council, Spain
MAURO ROSI, University of Pisa, Italy
BARBARA SHERWOOD LOLLAR, University of
Toronto, Canada
TORSTEN VENNEMANN, Université de
Lausanne, Switzerland
OLIVIER VIDAL, Université J. Fourier, France
MEENAKSHI WADHWA, Arizona State
University, USA
BERNARD WOOD, University of Oxford, UK
JON WOODHEAD, University of Melbourne,
Australia
EXECUTIVE COMMITTEE
CARLOS AYORA IBÁÑEZ, Sociedad Española
di Mineralogía
LIANE G. BENNING, European Association
of Geochemistry
THOMAS D. BULLEN, International Association
of GeoChemistry
PETER C. BURNS, Mineralogical Association
of Canada
GIUSEPPE CRUCIANI, Società Italiana di
Mineralogia e Petrologia
BARBARA L. DUTROW, Mineralogical
Society of America, Chair
W. CRAWFORD ELLIOTT, The Clay Minerals Society
MONICA M. GRADY, The Meteoritical Society
BERNARD GROBÉTY, Swiss Society of
Mineralogy and Petrology
GUY LIBOUREL, Société Française
de Minéralogie et de Cristallographie
MAREK MICHALIK, Mineralogical Society
of Poland
EDWIN A. SCHAUBLE, Geochemical Society
CLIFFORD R. STANLEY, Association
of Applied Geochemists
PETER TRELOAR, Mineralogical Society
of Great Britain and Ireland
FRIEDHELM VON BLANCKENBURG,
Deutsche Mineralogische Gesellschaft
MICHAEL WIEDENBECK, International
Association of Geoanalysts
MANAGING EDITOR
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and DOLORES DURANT
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The publishers assume no responsibility for
any statement of fact or opinion expressed
in the published material. The appearance of
advertising in this magazine does not constitute
endorsement or approval of the quality or value
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www.elementsmagazine.org
E LEMENTS
new offerings, panel members who fairly decide
which research proposals are most deserving of
funding, members of advisory boards that thoughtfully set science priorities when everything can’t
be supported. Our referees ensure that we play by
the rules, which for science means that truth and
accuracy should ultimately win.
For the most part, being a referee is a difficult
and thankless job, an uncompensated duty that
we assume for the betterment of our shared scientific community. In science, virtually all of us,
sooner or later, get to be referees. Few of us are
actually trained for these responsibilities, though,
and that is probably unfortunate. Those of us who
teach need to share with our students the rules
and techniques by which we referee, and instill
in them an appreciation for the trust we place in
referees and a sense of respect for its paramount
importance to science.
Hap McSween
My university plays (American) football—these
are big-time contests, held in a stadium that seats
more than a hundred thousand spectators and
televised more often than not. Watching a game
not long ago, I was taken aback by the crowd’s
vociferous reaction to a referee’s ruling against
the home team. Based on an instant
It is human nature to be loyal to the
replay projected onto a gigantic
The loyal crowd just
home team, to our colleagues and
screen at the top of the stadium,
the ruling seemed fair to me. The wanted their team to friends, and even to our scientific
referee was close to the action and win, and any rulings passions. Loyalty colors the way we
respond to our pastimes, our poliobviously had some experience in
by the guy in the
tics, and our professions. It seems
such matters. But the crowd around
me, none of whom I assume actu- striped shirt that did to me that in the past few decades,
ally had any experience refereeing, not further that cause various factions of society have
learned to express their loyalty in
was furious at the call and roared
were roundly booed. some angry and less-than-producits displeasure. Later in the game,
tive ways, such as rudely booing the
a similar ruling against the opponent resulted in the crowd’s jubilation. I doubt opposing team and polarizing our political discusthat this was their vocal affirmation of excellence sions. I don’t sense that this societal hardening
and accuracy in officiating. A good call was, by has spilled over into science yet. But we should
definition, one that favored the home team. The guard against it. My hope, and my expectation, is
loyal crowd just wanted their team to win, and that the community of scientists will continue to
any rulings by the guy in the striped shirt that did conduct their sparring contests with respect, and
not further that cause were roundly booed. This to value our referees and spare them the jeers that
is American football, but the same fan behavior greet the guys in the zebra shirts on game day.
(or worse) is a part of the other “football” played
around the world.
Hap McSween, University of Tennessee
[email protected]
We all understand this, of course. Sports are all
about winning, for the players and for the spectators, and it is easy to get caught up in the game
and lose track of the ideal of sportsmanship. The
reason I bring this up is that science is sometimes described as a contact sport. In science,
competing ideas often collide. We are obligated
to champion our hypotheses, at least until they
are proven wrong, and to marshal evidence against
hypotheses with which we disagree. This is the
way science works. Our contests are based on ideas
rather than brawn, but sometimes they can get
confrontational or even nasty.
Science, too, thankfully has its referees: reviewers
who provide insightful criticisms of manuscripts,
editors who adjudicate when reviewers don’t agree,
book reviewers who provide valuable insights into
219
Football referee signaling a touchdown. PHOTO YOBRO10 |
DREAMSTIME.COM
A UGUS T 2011
FROM THE EDITORS
THIS ISSUE
What started as a proposal on the traditional aspects of migmatites
evolved into “When the Continental Crust Melts” after the proposers
were challenged by the editors to think big and show the relevance of
their work to other disciplines. The focus became the impact of partial
melting on processes ranging from grain scale to crustal scale. As for
all issues, the guest editors worked hard with their international cast of
authors to bring you six stimulating papers.
JOHN VALLEY, PRINCIPAL EDITOR 2012–2014
John Valley has accepted our invitation to join the editorial team,
starting officially in January 2012. He will replace Hap McSween, whose
term ends at the end of 2011. We will welcome John formally in the
first issue of 2012. In the meantime, he is being integrated into the team
and participates in all discussions.
IMPACT FACTOR 2010
Elements’ 2010 impact factor was 3.105. Interestingly, Elements’ five-year
impact factor is 3.561. This probably reflects the fact that articles are
cited over several years.
The most cited articles from the time of publication to July 2011 are:
• Geisler T, Schaltegger U, Tomaschek F (2007) Re-equilibration of
zircon in aqueous fluids and melts. Elements 3: 43-50 (70 citations)
• Harley SL, Kelly NM, Moller A (2007) Zircon behaviour and the
thermal histories of mountain chains. Elements 3: 25-30 (64)
• Charlet L, Polya DA (2006) Arsenic in shallow, reducing groundwaters in southern Asia: An environmental health disaster.
Elements 2: 91-96 (59)
• Cartigny P (2005) Stable isotopes and the origin of diamond.
Elements 1: 79-84 (51)
E LEMENTS
• Morin G, Calas G (2006) Arsenic in soils, mine tailings, and former
industrial sites. Elements 2: 97-101 (42)
• Ohtani E (2005) Water in the mantle. Elements 1: 25-30 (36)
• Self S, Thordarson T, Widdowson M (2005) Gas fluxes from flood
basalt eruptions. Elements 1: 283-287 (32)
• Lumpkin GR (2006) Ceramic waste forms for actinides. Elements 2:
365-372 (32)
• O’Day PA (2006) Chemistry and mineralogy of arsenic. Elements 2:
77-83 (31)
• Rubatto D, Hermann J (2007) Zircon behaviour in deeply subducted
rocks. Elements 3: 31-36 (30)
• Bruno J, Ewing RC (2006) Spent nuclear fuel. Elements 2: 343-349 (30)
“NUCLEAR FUEL CYCLE” ISSUE
I mentioned in the April issue that, after the Fukushima nuclear accident, we made the “Nuclear Fuel Cycle” issue freely available on our
GeoScienceWorld site (www.elements.geoscienceworld.org) and on
Elements’ website at www.elementsmagazine.org. This was advertised
as widely as possible across our network, thanks to the efforts of Barb
Dutrow and the members of the Executive Committee. Did it work?
Yes, there was a spike of at least one order of magnitude in downloads
from GeoScienceWorld for all articles in that issue. The article “Spent
Nuclear Fuel” was downloaded 35 times more than in previous months.
FACEBOOK
At the time of writing, we had gained 182 followers on Facebook in less
than two months. If you have a Facebook account, do “like” us. We will
keep you posted on when issues are taken to press and mailed, and we
will share timely news. Go to www.facebook.com/elementsmagazine.
Pierrette Tremblay, Managing Editor
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SMASHING UP STONES
A critical, but often neglected, aspect of the entire geoanalytical process involves how one actually gets one’s sample from the field and
back to the laboratory for analysis. Clearly collecting material that is
representative of the process being studied is the fi rst critical step. But
what does one do once the specimen arrives back home? I can well
remember the many hours I spent as a graduate student some decades
ago in the crushing lab reducing kilograms of sample down to grams
of “representative” powder; this powder would be the starting material for my assigned tasks as a budding geochemist. Jaw mill to reduce
to centimetre-size – puck and ring mill to reduce to coarse powder –
agate ball mill to reduce to fi ne powder – hours of processing – keep
everything clean – don’t contaminate, don’t fractionate… Tedious, to
say the least.
So what technological progress has this aspect of mineralogy/geochemistry seen of late? Over roughly the past decade interest has grown in
the use of electrodynamic disaggregation. In this procedure, a highvoltage electrical impulse creates a shockwave either within the material
itself or within the fluid medium – typically water – that surrounds
it. This method of using “lightning strikes” to reduce walnut-size rock
chips down to individual mineral grains fi rst came to my attention
at the Goldschmidt 2009 meeting in Davos, Switzerland, where hardware from the Swiss company Selfrag AG (www.selfrag.com) was on
display. Subsequently a paper by Giese et al. (2010) described in detail
the physical process involved in the various forms of electrodynamic
disaggregation and also demonstrated that the high temperatures
that briefly affect the sample do not
bias apatite fission-track ages.
Model of the
Aerodynamic Impact
Reactor (patent pending). The reactor’s
height is approximately 2 metres.
FIGURE 1
Here I would like to describe briefly
an alternative technology which
I learned about a year or so ago.
It is being developed by Zybek
Advanced Products (www.zapmaterials.com), a small company located
in Boulder, Colorado, USA. Zybek’s
Aerody namic Impact Reactor
(FIG. 1) employs a high-pressure air
stream created by a series of impellers. Within the reactor chamber,
the airflow is directed into a vortex
geometry with a high-speed pneu-
FIGURE 3
An example of a phosphate starting material and end product from the
Aerodynamic Impact Reactor
matic flow established along the margin of the vessel. Within seconds
centimetre-size rock chips introduced into this environment undergo
a grain-size reduction through collisions within the reactor. The processed material is ultimately ejected through a port in the base of the
reaction chamber (FIG. 2). The device has been integrated with multiple
cyclone separators, which allow the processed material to be binned
by grain size and which also remove particulates down to roughly
1 µm grain size from the exhaust air. A number of parameters can be
adjusted on this apparatus, but it is commonly set to produce grain
size fractions smaller than 100 or even 50 microns. By reprocessing
the coarser-grained materials separated by the cyclone, it is possible to
produce ultimately a very fi ne-grained end product (FIG. 3).
So what are the advantages of this new approach to sample processing?
Though I have yet to see any concrete data, the method is supposed
to be relatively contamination free. High processing rates of up to several metric tons per hour could be of interest to the mining industry.
Compared to some of the other competing methods, the Aerodynamic
Impact Reactor is energy efficient, meaning lower operating costs. It is
flexible in terms of the grain-size distribution it can produce and the
nature of the feed stock. In fact, the method has been applied to the
processing of coal and even switch grass (FIG. 4). It tends to liberate
material along grain boundaries, but it also has been found to favour
high surface-to-volume ratios for the end product – a benefit if subsequent chemical treatment is planned.
FIGURE 4
Scanning electron microscope images of two of the more unusual
material types on which the device has been used
What is the future of this technology in either the mining industry or
basic research? This is hard to say as the technology has not yet been
widely disseminated. Time will tell.
Michael Wiedenbeck, ([email protected])
Helmholtz-Zentrum Potsdam
REFERENCE
FIGURE 2
Diagram of the individual components within the Aerodynamic Impact
Reactor processor integrated with cyclone separators
E LEMENTS
Giese J, Seward D, Finlay MS, Wüthrich E, Gnos E, Kurz D, Eggenberger U,
Schreurs G (2010) Electrodynamic disaggregation: Does it affect apatite
fission-track and (U-Th)/He analyses? Geostandards and Geoanalytical
Research 34: 39-48
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PEOPLE IN THE NEWS
MGPV-sponsored session entitled “Turning Up the Heat: Metamorphic
Perspectives on Mineral Equilibria, Heat Transport, Tectonics, and
Thermochronology” (T35).
ANTHONY E. WILLIAMSJONES, LOGAN MEDALIST
During last May’s joint annual
meeting of the Geological Association
of Canada and the Mineralogical
Association of Canada in Ottawa,
Anthony E. “Willy” WilliamsJones of McGill University received
the Logan Medal, the Geological
Association of Canada’s highest award
and presented to an individual for
sustained distinguished achievement
in Canadian Earth science. We reproduce excerpts of the citation below.
For thirty years, Willy’s influence on Canadian economic geology, and
Earth science in general, has been profound. Willy is an extremely creative and innovative researcher. The scope and breadth of his research
into the genesis of mineral deposits is unparalleled, not only in the array
of types of mineral deposits that he and his group have tackled but also
in the methodologies applied and the approaches taken. His studies of
mineralizing systems have included sediment-hosted base metal mineralization, uranium, porphyry Cu–Mo, granitoid-related W–Sn–Mo,
pegmatite and hydrothermal rare-element mineralization, epithermal
precious metals, asbestos, fluorite, Archean gold, and modern geothermal
systems. He and his group made a major research breakthrough recently
by showing that both petroleum and high-temperature vapor have the
ability to transport important quantities of ore-forming metals.
Although Willy’s contributions to economic geology are remarkable
indeed, they are even more so when considered in the context of his fundamental contributions to other fields, including environmental geology,
biomineralization, igneous petrology, and volcanology. In many varied
ways, Willy is a truly exceptional teacher and mentor. He has produced
legions of outstanding graduate and undergraduate students, inspiring
them to follow careers in Earth science.
JOHN FERRY, 2011
DISTINGUISHED GEOLOGIC
CAREER AWARDEE
John M. Ferry, Johns Hopkins
University, is the 2011 Distinguished
Geologic Career Awardee of the
Mineralogy, Geochemisty, Petrology,
and Volcanology (MGPV) Division
of the Geological Society of America.
The award will be presented during
the 2011 GSA Annual Meeting,
Minneapolis, Minnesota, USA. The
presentation will take place at the MGPV Reception (held jointly with
the Mineralogical Society of America and the Geochemical Society).
Dr. Ferry will give the Distinguished Geologic Career Award Lecture,
“When the Heat Is Turned Up, Look Out for the Hot Water,” at the
E LEMENTS
Dr. Ferry is cited for his contributions to the theory of fluid–rock interactions. His science is fundamentally field-based and his tools predominantly chemical and petrological, but the insights gained have significant physical implications. His systematic evaluation of the role of fluid
migration during regional metamorphism in many field areas worldwide
forms the basis for understanding the long-term permeability of the
middle to lower crust. He conducts careful, systematic field studies to test
his and others’ models. These studies have demonstrated that different
models best explain observations from individual field sites: nature is
not as simple as any single model. On Earth, crustal devolatilization
during metamorphism influences the mechanical strength and thermal
structure of the continents and contributes to element cycling between
the Earth, the atmosphere, and the oceans. Until the pioneering field
studies of John Ferry and his students and colleagues, these impacts
could not be realistically quantified.
ED STOLPER ELECTED
FOREIGN MEMBER OF
THE ROYAL SOCIETY
Edward Stolper is the William E.
Leonhard Professor of Geology and
Provost, Division of Geological and
Planetary Sciences at Caltech. He was
recently elected as a Foreign Member
of the Royal Society. Each year 44
Fellows, 8 Foreign Members and up
to 1 Honorary Fellow are elected from a group of over 700 candidates
who are proposed by the existing Fellowship.
Ed Stolper is renowned for his experimental and theoretical work on
melting and igneous processes on the Earth, Mars and asteroids. He
was the first to propose that the SNC meteorites came from Mars. He
developed the “sandwich” method of multiple saturation, which enabled
quantification of melting in the mantles of Earth and other planets. He
developed the first quantitative model of water speciation in glasses
and silicate melts and showed that water dissolves both as OH and as
molecular H2O. He was the first to show that silicate crystals float in
their melts at very high pressures, with implications for the differentiation of large silicate planets. He was the first to demonstrate a linear
relationship between the extent of melting and source water contents
in the back-arc environment.
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A UGUS T 2011
www.wiley.com
Michael Brown held academic appointments in
the UK until 1990 when he moved to the University
of Maryland as Professor of Geology and Chair. His
research interests are in high-temperature metamorphic petrology, crustal melting, and tectonic
geology. His work on migmatites and associated
granites has furthered our understanding of how
heat and mass are transferred within continents,
and in particular the relationships between sources and sinks of melt
and the importance of melt in the tectonic evolution of orogenic belts.
With time his research has broadened into ultrahigh-temperature and
high-pressure metamorphism, the origin of paired metamorphic belts,
and secular change.
Bernardo Cesare is a professor of petrology at the
University of Padova (Italy), where he earned a PhD
in geology in 1992 studying the Vedrette di Ries
contact aureole. His research interests include lowpressure metamorphism and anatexis of pelitic
rocks, fluid–melt–rock interactions in graphitic systems, fluid and melt inclusions, and the crystal
chemistry of high-temperature minerals. His
approach to crustal melting involves primarily the multidisciplinary
study of anatectic enclaves from SE Spain and of “nanogranite” inclusions in migmatites and granulites. During the last decade he was deeply
involved in coordinating the international training of early-stage
researchers in metamorphic petrology.
Chris Clark is a senior research fellow in metamorphic geology and geochronology at Curtin
University in Western Australia. His principal
research interests are in the linking of geochronology, specifically the U–Pb method using zircon
and monazite, with the development of metamorphic assemblages in order to constrain the durations of mountain-building events in high-grade
metamorphic terranes.
Ian C. W. Fitzsimons is a professor of metamorphic
geology at Curtin University in Perth, Western
Australia. After an undergraduate degree at the
University of Cambridge, he completed a PhD on
granulite facies metamorphism at the University of
Edinburgh, followed by research positions at Royal
Holloway University of London, the University of
Edinburgh, and Monash University. He moved to
Perth in 1998, where he focuses his research on the field geology, mineralogy, petrology, and geochronology of metamorphic rocks, particularly the Precambrian granulites of Antarctica, India, and Madagascar.
Simon L. Harley is Professor of Lower Crustal
Processes at the University of Edinburgh, Scotland.
He has over 30 years experience in metamorphic
and experimental geology and geochemistry, which
he has applied to understanding the high-temperature processes that take place during the evolution
of continents. His approach emphasizes their chemical, isotopic, and petrographic records as preserved
in minerals and mineral assemblages. He is internationally recognized
as a leading authority on ultrahigh-temperature metamorphism and
granulites and their implications for continental evolution.
Nigel B. W. Harris, a graduate of the University of
Cambridge, is a petrologist and geochemist who
has studied the causes and consequences of melt
production in tectonically thickened crust since his
first Tibetan field campaign in 1985. He was
appointed Professor of Tectonics at the Open
University (UK) in 2001. In recent years his work
has focused on chemical proxies for global weathering fluxes and the linkage between tectonics, orography, and climate
in the Himalaya.
David Healy is Lecturer in Geomechanics at the
University of Aberdeen. He has research interests
in structural geology, rock mechanics, tectonics,
and metamorphic geology. He has a keen interest
in the theory of natural rock deformation and uses
quantitative models to explore the consequences
of theoretical predictions in terms of field and laboratory observations.
Marian B. Holness studied for both her degrees at
the University of Cambridge. After periods at the
University of Chicago and the University of
Edinburgh, she returned to Cambridge in 1997 to
take up a teaching post. Her interests are primarily
in decoding the record of rock history left behind
in grain-scale fabrics. She has progressed from
working on volatile fluids in metamorphic rocks,
through the partial melting of high-grade metamorphic rocks, and is
now investigating the complex problem of solidification, in particular
of gabbros.
Rebecca A. Jamieson is a graduate of Memorial
University of Newfoundland (PhD 1979) and is currently Carnegie Professor and Chair of Earth
Sciences at Dalhousie University in Halifax, Canada.
She studies interactions between metamorphic and
tectonic processes at all scales using a variety of
approaches, including field work, petrology, geochronology, and geodynamic modeling. She has
worked on parts of the Appalachian–Caledonian, Grenvillian, and
Himalayan–Tibetan orogenic belts. Her recent work has focused on the
causes and consequences of melting and ductile flow in orogens and on
the exhumation of ultrahigh-pressure metamorphic rocks.
Timothy E. Johnson is a postdoctoral research scientist at the University of Mainz. He received his
BSc (1992) and PhD (1999) from the University of
Derby and held postdoctoral positions at the universities of Graz and Maryland before moving to
Germany. His expertise is in metamorphic geology
and mineral equilibria modeling of subsolidus and
suprasolidus rocks of varying compositions and
from a variety of tectonothermal environments. He has a particular
interest in the generation and segregation of melt and its consequences
for the compositional, thermal, and rheological evolution of the crust.
Cont’d on page 227
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Cont’d from page 226
Fawna J. Korhonen is a research fellow at Curtin
University of Technology, Australia. She moved to
this position in 2009 after a three-year postdoctoral
appointment at the University of Maryland. Fawna
received her BA from Carleton College and her PhD
from the University of Minnesota. Her research
interests include the study of polyphase high-grade
metamorphism and anatexis, and the processes of
mass transfer within the crust that lead to intracrustal differentiation
during orogenesis. She is particularly interested in the chemical and
physical effects of melting and melt loss during protracted crustal evolution, and the genetic link between residual granulites, migmatites, and
granites.
Claudio L. Rosenberg graduated from the State
University of Milano (Italy) in 1989, where he completed an MSc thesis on the growth of K-feldspar
megacrysts in granites. After a PhD in Basel
(Switzerland) on the emplacement and solid-state
flow of the Bergell pluton (Central Alps), he moved
to Giessen (Germany) where he studied the fabrics
of synkinematic, partially melted rock using experimental analogues. Based on these experiments and studies of natural
migmatitic fabrics, he described the modes of localization and melt
segregation and the rheological changes during deformation of melting
crust. He is now at the Freie Universität Berlin (Germany), where he
works on the syncollisional exhumation of the Alpine chain.
Edward W. Sawyer received his first degree from
the University of Southampton. He then worked
for the Geological Survey of South Africa in Namibia
for six years and obtained a master’s degree from
the University of Cape Town. He then moved to
Canada and received a PhD from the University of
Toronto, followed by postdoctoral research at the
Geological Survey of Norway. He returned to
Canada in 1986 to take a post at the Université du Québec à Chicoutimi,
where he is now a professor. His principal research interest is in migmatites and the segregation and migration of anatectic melt in the continental crust.
Gary Stevens graduated with BSc and MSc degrees
from Rand Afrikaans University in Johannesburg
and received his PhD degree from the University
of Manchester in 1995. Following this, he spent 5
years at the University of the Witwatersrand, where
the Economic Geology Research Unit kindly
indulged his research interests in petrology. For the
past 10 years he has been employed at Stellenbosch
University, where he holds the position of South African Research Chair
in Experimental Petrology. His main research interests are the origins
of the continental crust, partial melting of the crust, and the processes
that shape granite chemistry.
Martyn J. Unsworth has been a professor of geophysics at the University of Alberta in Edmonton,
Canada, since 2000. He holds a BA in natural sciences (1986) and a PhD in marine geophysics
(1991), both from the University of Cambridge. His
research focuses on the use of electromagnetic geophysics to study continental dynamics. His recent
studies have been in the Tibetan Plateau, eastern
Anatolia, Taiwan, and the Canadian Cordillera. He makes use of the
magnetotelluric method to study the composition of the crust and
mantle in regions undergoing deformation. He has also worked on the
use of these geophysical techniques in environmental and geothermal
applications.
Richard W. White is a professor of metamorphic
geology at the University of Mainz, Germany. He
received his BSc and MSc from the University of
Sydney and his PhD from Macquarie University
(Sydney) in 1998. He spent nine years at the
University of Melbourne in several postdoctoral
positions, undertaking mineral equilibria modeling
studies, focusing on partial melting. He then moved
to Germany, where his main interests center on high-temperature metamorphic processes, the development of mineral and melt activity–composition models, and their application to natural examples. He is currently an editor of the Journal of Metamorphic Geology.
Karel Schulmann started his career in 1987 at the
Czech Geological Survey in Prague. From 1991 to
2004 he was chair of the Department of Structural
Geology and Petrology of Charles University in
Prague. Since 2004 he has held the position of professor of geology and tectonics at the University of
Strasbourg. His research interests include the structural geology and tectonics of orogenic collisional
systems, metamorphic petrology, metamorphic microstructures and textures, rock fabrics, orogenic processes such as the exhumation of orogenic
lower crust, the mechanisms of lower crustal flow, and the accretion of
juvenile crust in the Central Asian Orogenic Belt.
Christine S. Siddoway received her BA from
Carleton College and MSc from the University of
Arizona. Following her PhD from the University of
California, Santa Barbara, she completed a Fulbright
postdoctoral research fellowship at the University
of Siena (Italy). She has been an investigator in the
U.S. Antarctic research program since 1990, during
which time she has examined the history of breakup
between West Antarctica and New Zealand, the evolution of the active
margin of East Gondwana, and the deformation and metamorphism of
mid-crustal rocks in transcurrent settings. She is on the faculty of the
Geology Department at Colorado College and served as chair during
2007–2010.
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