Structure and Emplacement of High-Level Magmatic Systems - Special Publication no 302 (Geological Society)

234 Pages·2008·6.66 MB·English

by  K. Thomson

There are continual rounds of annual conferences, special sessions and other symposia that provide ample
opportunity for researchers to convene and discuss igneous processes. However, the origins of laccoliths
and sills continue to inspire and confound geologists.
In one sense, this is surprising. After all, don’t we know all we need to know about these rocks by now? As
testified by the diverse range of topics covered in this volume, the answer is clearly ‘no’.
This book contains contributions on physical geology, igneous petrology, volcanology, structural geology,
crustal mechanics and geophysics that cover the entire gambit of geological processes associated with the
shallow emplacement of magma. High-level intrusions in sedimentary basins can also act as hydrocarbon
reservoirs and as sources for thermal maturation.
In drawing together a diversity of perspectives on the emplacement of sills, laccoliths and dykes we hope to
advance further our understanding of their behaviour.
Structure and Emplacement of High-Level
Magmatic Systems
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Itisrecommendedthatreferencetoallorpartofthisbookshouldbemadeinoneofthefollowingways:
THOMSON K.&PETFORD N.(eds)2008.StructureandEmplacementofHigh-LevelMagmaticSystems.
GeologicalSociety,London,SpecialPublications,302.
ABLAY,G.J.,CLEMENS,J.D.&PETFORD,N.Large-scalemechanicsoffracture-mediatedfelsicmagma
intrusion driven by hydraulic inflation and buoyancy pumping. In: THOMSON K. & PETFORD N. (eds)
Structure and Emplacement of High-Level Magmatic Systems. Geological Society, London, Special
Publications,302,3–29.
GEOLOGICAL SOCIETY SPECIAL PUBLICATION NO.302
Structure and Emplacement of High-Level
Magmatic Systems
EDITED BY
K. THOMSON
University of Birmingham, UK
and
N. PETFORD
Bournemouth University, UK
2008
Published by
The Geological Society
London
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Preface
LASI II (Laccoliths, Sills and Dykes) washeld on at the interface between geophysics and physical
the Island of Skye, Scotland, on 1–3 April 2006. geology, as applied to the nature and geometry of
Building on the success of LASI I held in 2002 sillsandotherintrusions.Hisworkwasinterdisci-
at TU BergakademieFreiberg, Germany,40 parti- plinary, thought-provoking and colourful, often
cipants from around the world descended on bestenjoyedthroughpaper-framedspectacleswith
Portree for a combined workshop and field trip to green and red plastic lenses! Ken provided a
examine the classic Paleocene sill complexes, led conduit linking two subject areas distinguished
by Donny Hutton, Ken Thomson and students largely by their historical lack of cross-over,
from Birmingham University. Papers from the namely reflection seismology and volcanology. In
LASI I meeting in Freiberg, Germany were pub- pioneering the transfer of knowledge between the
lishedbytheGeologicalSocietyin2004(Geologi- two, Ken was at the forefront of a research area
calSociety,London,SpecialPublication234edited set to become increasingly relevant as the need to
byC.Breitkreuz&N.Petford). understand better the role of high-level intrusions
LASI II provided an opportunity to discover in thermal maturation, storage and trapping of
how the study of high-level magmatic systems hydrocarbonsgrows.
had developed over the 4 years since Freiberg. Tragically,KenThomsondiedon18April2007,
With contributions on physical geology, igneous justasthefirstrevisionsfromauthorswerearriving
petrology, volcanology, structural geology, crustal atBirmingham.Ken’shandrunsdeepthroughthis
mechanics and geophysics, the 43 presentations volume and I know he was proud of the work put
attheSkyeworkshopcoveredtheentiregambitof intotheassembledpapersbyauthorsandreviewers
geological processes associated with the shallow alike, and grateful of support from the Geological
emplacement of magma. Arrangements for Society, the Volcanic and Magmatic Studies
LASI III, to be hosted by Italian colleagues on Group, and the IAVCEI commissions on granites
Elba island, are already well underway (http:// and volcanogenic sediments. This Special Publi-
www.dst.unipi.it/dst/rocchi/LASI3/Home.html). cationisdedicatedtohim.
LASIII(thedifficultsecondmeeting)wouldnot Ken is sadly no longer with us. But LASI
havehappenedwithouttheorganizationaldriveand liveson.
hardworkofKenThomson.Ken’sspecialismwas NICK PETFORD

Obituary: Dr Ken Thomson 1966–2007
It was a huge shock to us all when Ken Thomson His enthusiasm for geology was abundant and
died suddenly while at work in April 2007. Ken hisresearcheclectic.Hewasbestknowninvolca-
wasafamiliarfaceinvolcanologycircles,andco- nology and igneous circles for using oil industry
organizedthehighlysuccessfulLASIIIconference offshore three-dimensional (3D) seismic data to
(theinspirationforthisSpecialPublication).Itisa pioneer the development of sophisticated high-
greatshamethatthegeologicalcommunityhaslost resolution3Dimagesofburiedvolcanicfieldsand
suchafreethinker. sillcomplexes.Herealizedthatthiskindofvisual-
izationwouldgiveunprecedentedaccesstothegeo-
metryandarchitectureofunexposedsillcomplexes,
and help us in understand their emplacement and
associated magma flow. This led to a number of
key breakthroughs including a paper published in
2004 looking at the emplacement of saucer-
shaped sills from the NW Atlantic Margin, which
showed that sills emplaced as a series of lobes
similar to those seen in lava flows. His work was
clearly beginning to provide significant insights
and was tackling some long-standing issues in
emplacement of sill complexes. The final major
paper before his death gave very convincing evi-
dence for an interconnected plumbing system of
sills and dykes feeding past fissure eruptions in
the now submerged approximately 60Ma flood
basaltsoftheNWAtlanticMargin.
The innovations of Ken’s research were not
restrictedtoigneousintrusions.Usingthevisualiza-
tiontechniqueshedevelopedforigneousbodiesand
making use of the otherwise unexploited top few
tensofmetresofseismicdata,hewasabletohelp
the Institute of Archaeology and Antiquity at the
University of Birmingham to reconstruct a vast
submergedlandscapeinthesouthernNorthSea.It
is a particular tragedy that Ken’s death came just
a week before the work he pioneered was the
subjectofa‘TimeTeamSpecial’onChannel4.
KenbeganhiscareerasamedicatManchester, KenwasproudofhisDoncasterroots.Hehasbeen
but realized his true calling and transferred described,andwillberemembered,asanarchetypal
toGeology,graduatingin1990.Hethenmovedto Yorkshireman and a traditionalist. His mild-
Edinburgh, where his PhD thesis concentrated on manneredunassumingpersonaanduniquesenseof
basindynamicsoftheMorayFirth.Aftercomplet- humourendearedhimtoagreatnumberofpeople.
inghisPhDhetookupapositionattheUniversity Heisgreatlymissed,asbothagoodfriendand
of Oxford as the BP Exploration Junior Research colleague.
Fellow in Geophysics, before moving on to a NICK SCHOFIELD,
lectureship in petroleum geology at Durham in CARL STEVENSON
1995,andthenfinallytoBirminghamin1999. &DONNY HUTTON