Arc-Continent Collision

509 Pages·2011·25.13 MB·English

by  Dennis Brown

Frontiers in Earth Sciences
SeriesEditors:J.P.Brun,O.Oncken,H.Weissert,W.-C.Dullo
.
Dennis Brown (cid:129) Paul D. Ryan
Editors
Arc-Continent Collision
Editors
Dr.DennisBrown Dr.PaulD.Ryan
InstitutodeCienciasdelaTierra NationalUniversityofIreland,Galway
“JaumeAlmera”,CSIC Dept.Earth&OceanSciences(EOS)
C/LluisSoleiSabariss/n UniversityRoad
08028Barcelona Galway
Spain Ireland
[email protected] [email protected]
Thispublicationwasgrant-aidedbytheNationalUniversityofIreland,Galway
ISBN978-3-540-88557-3 e-ISBN978-3-540-88558-0
DOI10.1007/978-3-540-88558-0
SpringerHeidelbergDordrechtLondonNewYork
LibraryofCongressControlNumber:2011931205
# Springer-VerlagBerlinHeidelberg2011
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Preface
One of the key areas of research in the Earth Sciences are processes that occur
along the boundaries of the tectonic plates that make up Earth’s lithosphere. Of
particular importance are the processes of tectonic accretion and erosion along
convergentplateboundaries.Oneoftheprincipalmechanismsofaccretionoccurs
whenintra-oceanicvolcanicarcscollidewiththemarginofacontinentinwhatis
calledarc–continentcollision.Arc–continentcollisionhasbeenoneoftheimpor-
tant tectonic processes in the formation of mountain belts throughout geological
timeandcontinuestodayalongtectonicallyactiveplateboundariessuchasthosein
the SW Pacific or the Caribbean. Well-constrained fossil arc–continent collision
orogens supply thethird and fourthdimension(depth andtime)thataregenerally
missing from currently active examples where tectonic processes such as sub-
duction, uplift and erosion, and the formation of topography can be observed.
Arc–continent collision is also thought to have been one of the most important
processesinvolvedinthegrowthofthecontinentalcrustovergeologicaltime,and
mayalsoplayanimportantroleinitsrecyclingbackintothemantleviasubduction.
The integration of research between active and fossil arc–continent orogens pro-
videkeydatafortheunderstandingofhowplatetectonicsworkstoday,andhowit
might have worked in the past. Understanding the geological processes that take
placeduringarc–continentcollisionisthereforeofimportanceforourunderstand-
ing of how collisional orogens evolve and how the continental crust grows or is
destroyed.Furthermore,zonesofarc–continentcollisionareproducersofmuchof
theworldsprimaryeconomicwealthintheformofminerals,sounderstandingthe
processesthattakeplaceduringthesetectoniceventsisofimportanceinmodeling
howthismineralwealthisformedandpreserved.
Arc–continent collision orogeny is generally short-lived, lasting from c. 5 to
20 My, although much longer-lived regional events do occur. The duration of an
arc–continent collision orogeny depends on a number of factors, among which the
obliquityofthe collision,thesubductionvelocity, andthestructuralarchitectureof
thearcandthecontinentalmargininvolvedareofprimaryimportance.Inthisbook
wedefinetheonsetofarc–continentcollisionasthearrivaloftheleadingedgeofthe
continental margin (continental crust to oceanic crust transition) at the subduction
zone, something that is often difficult to identify in the geology of an orogen.
Thinned, extended continental margins often reach 150–400 km in width and are
highly structured. There is now widespread evidence that this thinned crust can be
deeply subducted (>200 km) before being returned to the surface as high- and
ultrahigh-pressure rocks. Dating these high-pressure rocks can provide important
constraintsonthetimingofarrivalofthecontinentalmarginatthesubductionzone.
v
vi Preface
Afurtherconstraintcanbesuppliedbythearcvolcanics,whosegeochemistrymay
record the entrance of continentally derived sediments, or the thinned continental
crust itself, into the subduction zone. In currently active systems, imaging the
subducted continental lithosphere with techniques such as seismic tomography
can also providekey data for determining the timingof on-setof collision and the
rates at which the continental crust is being subducted. With the arrival of thicker
continentalcrust(c.20–30kmthick)atthesubductionzonethedevelopingorogen
is generally uplifted to above sea level where it begins to erode and provide
sediment to a foreland basin and across the arc–continent suture zone and the
forearc. As convergence continues, the active volcanic front generally shuts down
shortlyaftertheentryofthecontinentalcrustintothesubductionzone,andvolcanic
activity can move away from the subduction zone to continue outboard of it for
sometimebeforestoppingcompletely.Duringthefinalstageofcollision,achange
inthelocationofthesubductionzonecantakeplace,furthermarkingtheendofthe
arc–continentcollision.Thefinalresultofthearc–continentcollisionisasignificant
change in the structural architecture, composition, and rheology of the continental
margin.
Theaimofthisbookistobringtogetheraseriesofpapersthatarededicatedtothe
investigationofthetectonicprocessesthattakeplaceduringarc–continentcollision.
A further aim is to investigate how tectonic processes influence the large-scale
geological characteristics of these accretionary orogens and their mineral wealth.
Finally, specific examples of arc–continent collisions are investigated. These range
in age from the Neoproterozoic to those that are currently active, covering a large
portion ofgeological time.To advance these aims, aseries ofpointsare developed
whichweattempttoaddresswherepossibleineachpaper.Thesepointsare:
(cid:129) Thelarge-scalecrustandmantlestructure.
(cid:129) Thenatureandroleofthelithosphereandasthenosphericmantleinthedynamics
andchemistryofthesubductionandcollisionprocesses.
(cid:129) Processesthattakeplacedeepwithinthesubductionchannelinpureintraoceanic
subductionandduringthesubductionofthecontinentalcrust.
(cid:129) The geochemical and petrological evolution of the arc both before and during
collision.
(cid:129) Thenatureofthecontinentalmarginanditsresponsetothecollision.
(cid:129) Theformationoftopographyandtheerosionofthedevelopingmountainbeltto
formaforelandandasutureforearcbasin.
(cid:129) Fore-arcsubductionoraccretion.
(cid:129) Theemplacementofophiolitesandultramaficmassifs.
(cid:129) Metamorphismwithinthedevelopingorogen.
(cid:129) Thepossibilityofchangesinthelocationofthepost-collisionsubductionzone.
(cid:129) Placeconstraintsonthedurationofarc–continentcollisionorogeny.
(cid:129) Recycling,orgrowthanddestructionofthecontinentalcrust.
The book is organised in four sections. In the first section, numerical modeling
and natural examples are used to look at the three main players involved in arc–
continent collision; the continental margin, the volcanic arc, and the subduction
zone. In the second section, natural examples of arc–continent collisions are
described.Inthethirdsection,modelingofvariousaspectsofarc–continentcollision
are presented. In the fourthsection, we bring together the materialpresented in the
previoussectionsaddressingtheseriesofpointsoutlinedaboveand,wherepossible,
attempttoprovideanswerstothem.
Preface vii
Finally,thispublicationwasgrant-aidedbythePublicationsFundoftheNational
UniversityofIreland,Galway.Also,wewouldliketoextendourthankstothosewho
kindlyprovidedreviewsofthepapers.ThisisanIGCP524publication.
Barcelona,Spain DennisBrown
Galway,Ireland PaulD.Ryan
.
Contents
PartI TheMainPlayers
1 RiftedMargins:BuildingBlocksofLaterCollision ..................... 3
T.RestonandG.Manatschal
2 Intra-oceanicSubductionZones ......................................... 23
T.V.Gerya
3 TheSubductabilityofContinentalLithosphere:
TheBeforeandAfterStory .............................................. 53
J.C.AfonsoandS.Zlotnik
4 TheSeismicStructureofIslandArcCrust ............................. 87
A.J.Calvert
5 VerticalStratificationofComposition,Density,andInferred
MagmaticProcessesinExposedArcCrustalSections ................ 121
S.M.DeBariandA.R.Greene
6 TheGenerationandPreservationofMineralDeposits
inArc–ContinentCollisionEnvironments ............................. 145
R.J.HerringtonandD.Brown
PartII SpecificExamplesofArc-ContinentCollision
7 TheNatureoftheBandaArc–ContinentCollision
intheTimorRegion ..................................................... 163
R.Harris
8 TheArc–ContinentCollisioninTaiwan ............................... 213
T.Byrne,Y.-C.Chan,R.-J.Rau,C.-Y.Lu,
Y.-H.Lee,andY.-J.Wang
9 EarlyEoceneArc–ContinentCollisioninKamchatka,Russia:
StructuralEvolutionandGeodynamicModel ......................... 247
E.Konstantinovskaya
10 TheAsia–Kohistan–IndiaCollision:ReviewandDiscussion ......... 279
J.-P.Burg
11 ProcessesofArc–ContinentCollisionintheUralides ................. 311
D.Brown,R.J.Herrington,andJ.Alvarez-Marron
ix