结构特征与石油地质条件研究中国塔里木盆地南部褶皱冲断带原文.docx

结构特征与石油地质条件研究中国塔里木盆地南部褶皱冲断带原文.docx

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结构特征与石油地质条件研究中国塔里木盆地南部褶皱冲断带原文

.AbstractThewestKunlunfold-thrustbelt（WKFTB）andtheAltunfold-thrustbelt（AFTB）arerespectivelylocatedinthesouthernmarginoftheTarimbasin,NWChina.Theanalysesoftypicalstructuresandregionaldynamicsofthefold-thrustbeltsrevealtheirdifferentstructuralandpe-troleumfeaturesandmechanisms.WKFTBdiffersfromAFTBbyabundantfault一relatedfoldsandtriangleszones,andwasformedbynorthwardextrusionofthewestKunlunorogen.AFTBwasaffectedsynchronouslybynorthwardextrusionoftheAltunorogenandthesinistralstrike-slippingoftheAltunFault,soitischaracterizedbytheminorscaleandthemonotonousstructuralstyles.TheAqikeanticlineandtheAqikefault,ofwhichthestrikesareorthogonaltothestrikeofthefold-thrustbelts,areregardedastheadjustivestructuresbetweenbothofthefold-thrustbelts.

TheTarimbasin,NWChina,neighborsrespec-

livelyonthewestKunlunorogenandtheAltunorogen

insouth.TheAltunareawasregardedformerlyasa

partoftheTarimbasinandnamed"AltunFault-Up-

lift".NowtheAltunareaisregardedasanEarlyPa-

leozoicorogenbecauseofdiscoveriesoftheophiolite,

eclogueandhigh-ultrahighpressuremetamorphic

rockswithintheAltunarea's一9].TheYechenand

Hetiansagsarelocatedinthenorthernpiedmontofthe

westKunlunorogen,andtheMinfengandRuoqiang

sagsarelocatedinthenorthernpiedmontoftheAltun

orogen（fig.1）.

BothofthewestKunlunfold-thrustbelt

（WKFTB）andtheAltunfold-thrustbelt（AFTB）are

locatedinthesouthernedgeoftheTarimbasin,but

WKFTBismoreattractivethanAFTBbecauseoftheir

differentstructuralfeaturesandpetroleumpotentials,

somanyofresearchershavepaidtheirattentionsto

WKFTB}}}}6}.AFTBhasrarelybeenresearched.

Onthebasisofthecomparisonofthetypical

structuralsectionsofboththefold-thrustbelts,the

papertriestorevealtheirdifferentstructuralfeatures,

transitionrelationshipbetweenthem,dynamics

mechanismsandpetroleumgeology

Theoil-gaspoolsofWKFTBdevelopmainlyinthefaulted-relatedanticlinetraps,buttheoil-gas

poolsofAFTBdevelopmainlyinthelowfault-blockandanticlinestrapsrelatedwiththe}-

leo一uplifts.Therearedifferentexplorationcountermeasuresforbothofthefold-thrustbelts.

Keywords:

Tarim,westKunlunorogen,Altunorogen,fold-thrustbelt,structuralfeatures,petroleumgeology.

D01:

10.1360/04zd0025

1Structuralfeatureofthefold-thrustbelts

Bothofthefold-thrustbeltshavedifferent

turalscopes（fig.1）andstyles（fig.2）.

truc-

StructuralfeaturesofWKFTB

WKFTBischaracterizedbythefollowingfive

structuralfeatures:

（1）Imbricatethrusts.Suchthrusts

developinthesouthofFusha,wheretheFroterozoic

metamorphicrocksthrustnorthwards（Fig.2（a））.

（2）

Fault-propagationfolds.IntheFushaandKekeyaof

theYechensag,asaresultoftheaccommodationof

thedisplacementontheunderlyingthrusts,the

fault-propagationfoldswereformedintheoverlying

strata（fig.2（a））.（3）Back-thrustsandtrianglezones.

TheSangzhutrianglezoneisclearlyreflectedinthe

seismiclines,andthesuperpositionofthePermian

stratahasbeenprovedbythewells（fig.2（b））.（4）

Fault-bendfolds.ThefoldinthesouthofHetianisa

typicalfault-bendfold（fig.2（c））.（5）Buriedthrusts.In

thenorthoftherevealableTiebeifault口infig.1）,

thethrustareburied,andtheHetianfault（⑧infig.1）isoneofthelargestburiedthrusts,ofwhichthevan-

guardisabout40kmawayfromtheTiebeifault.The

buriedthrustsarerelatedtothefourseriesofregional

detachmentlevels,i.e.gypsum-argillaceousrocksin

thebaseofCambrian,base（75-206minthickness）

andtop（400-670minthickness）argillaceousrocks

ofLowerPermianPusigeFormation（P,p）andthe

gypsum（0-136minthickness）ofPaleoceneAer-

tashiFormation（E,a）.Thevariabledepthofthede-

tachmentlevelsalongthestrikeofthefold-thrustbelt

isoneofthemainreasonsforthedifferentstructural

styles}}}}.

Theabove-mentionedstructuralstylesdivided

WKFTBalongitsstrike（almostE-W）intoKekeya,

Sangzhu-DuwaandHetiannansegments}}0'}}'}4},and

theobliquethrust（strike-slip）faultsbetweenvarious

arcuatesegmentsarethespecialintraplatedeformation

productoftheSouthwestTarimforelandbasin}}0}.

WKFTBtakesitsshapeduringthelarge-scale

thrustingsinceEocene}}0'}}}.InKekeya,fromsouthtonormexposerusna,neKeyaanaHumananncmesm

turn.Fromsouthtonorth,theageofthefoldedstrata

becomesyoungergradually,andthescaleofthefolds

minishesgradually.ThefactthatMiocenestratadie

outintheFushaandSangzhuanticlinessuggeststhat

bothoftheanticlineshavetheirrudimentaryshapesin

theendofOligocene.PlioceneAtushiFormation（NZa）

inthenorthernlimboftheKekeyaanticlinediesout

southwards,sotheKekeyaanticlinewasformedinthe

endofMiocene.AseriesofstrataoverlyingPliocene

oftheGumananticlinedieout,indicatethattheGi-

mananticlinewasformedafterPliocene}}b}.Inthe

westernbankoftheRiverSangzhu,theUpperCar-boniferouslimestoneoccursasnappeoutlieronthe

PlioceneAtushiFormation（NZa）.Thesouthernedge

faultofWKFTB（Tiebeifault）transectstheupper

Pleistocene（Q3）conglomerateintheDuwaarea.The

middlePleistocene（Q2）overliesontheXiyuForma-

lionwithclearunconformityintheforelandofthe

westKunlunorogen.Alloftheabove-mentionedgeo-

logicalfactsshowthatthelarge-scalethrustingof

WKFTBtookplaceduringMioceneandPleistocene.

WKFTBisprobablyactivenowbecause

（1）

HolocenestratainKekeyaarefolded}}0};

（2）insome

seismiclines,thetriangleshapeofthegrowthstratainPleistocenehasnotcompleted.Sothevanguardfault

ofWKFTB（Hetianfault）isactive.

1.2StructuralfeaturesofAFTB

AFTBislessdevelopedthanWKFTBbecauseof

tworeasons:

（1）thrustsanditsdisplacementare

minor;and

（2）fault-relatedfoldsandtrianglezonedo

notexist（fig.2（d）,（e））.

ThewidthofAFTBisobviouslylessthanthatof

WKFTB（fig.1）,suchalsoisreflectedbythelandform

intheforelandoftheAltunorogen.Strongcontrastof

thelandformbetweentheAltunorogenandMin-

feng-Ruoqiangsagoccursalongthemainfaultofthe

Altunfaultsystem.ThehighertopographyoftheAl-

tunMountaimcontrastswithflattertopographyofthe

sags.BetweentheAltunMountainandsagsthereisa

narrowrampdippingnorthwards,whichismadeupof

theAFTB.IntheJianggesayiarea,Froterozoicfelsic

gneissthrustoverJurassiccoal-bearingstrata（fig.

2（e））.Jurassicandoverlyingstrataconsistofagentle

rampabout3kminwidth.

Figures2（d）and（e）makeclearthatinthenorth-

ernforelandoftheAltunorogenexistnotonlythe

strike-slipfaults,butalsothefold-thrustbelt.Because

ofthelimitedwidthalongthethrustingdirection,the

fault-relatedfoldsandtrianglezonegenerallycannot

bedeveloped.

MinfengandRuoqiangsagsoccurredasa

fault-subsidencebasinduringJurassic,andJurassic

conglomerateoverlappedsouthwardsontheFrotero-

zoic.Thelarge-scaleriseoftheeastKunlunMts.and

AltunMts.inCenozoicresultsinthrustingnorthwards

intheirnorthernforeland,andtheunconformitybe-

tweenJurassicandProterozoicisover-turned,and

Jurassic-Pliocenestratadipnorthwardssteeply.The

approximatehorizontalunconformitybetweenPleis-

toceneanditsunderlyingstrata（fig.2（e））indicates

thatthrustingtookmainlyplaceinthemiddle-later

Pliocene.

SimilartoWKFTB,AFTBisalsoactivenow.In

theaerialandsatelliticimage,theaccordantleft-de-

flexionoftheriversfromtheAltunMts.alongthe

mainAltunfaultindicatestheactivestrike-slippinginthefault.Asthefaultistranspression,itshouldthrust

northwardswhileleftstrike-slipping.

LAq1KetranSltlOnstructurebetweenWlirlii

andAFTB

FeaturesandmechanismoftheAqikestructure

TheAqikestructureisaspecialunitinthesouth-

edgeoftheTarimbasin,andconsistsofAqike

Jln

2.er

faultedanticlineandAqikefault（fig.1）.Aqikefaulted

anticlineistransectedbythenorthernedgefaultof

Tiekelike,anditsaxisapproximatetosouth-north

strikeplungesnorthwards.TheSilurian（?

）low-graded

metamorphicrocksexposeinitscore,andareoverlain

bytheconglomerate,sandstone-bearinggravelofthe

upperDevonianQizilafuFormation（D3q）.Thewest-

ernlimbconsistsofUpperCarboniferous,Permian,

LowerCretaceousandPaleogeneiswellexposed.The

easternlimbistransectedbyAqikefault,andCarbon-

iferous,PermianandPaleogeneexposediscontinu-

ouslyalongthefault.Thestrataofthewesternlimb

dip400-600,butthestrataoftheeasternlimbdip

steeplyoroverturnedly.Theaxialplanedipping

westwardsreflectstheextrusionfromwesttoeast.

BecausethattheWuqiaGroup（（E3-N,）wq）isinvolved

inthefold,theanticlinewasformedinPlio-

Gene-Pleistocene.Aqikefaultlocatedintheeastern

limbnearthecoreoftheAqikeanticlinedipswest-

wardswith650-700,andbelongstoastrike-slip

thrustwithapproximateS-Nstrike.Accordingtothe

seismicdata,theAqikefaultalsoliesconcealed

northwardsabout40km（fig.1）.Theparticularityof

theAqikestructureconsistsinitsstrikeorthogonalto

thefold-thrustbeltsratherthanparallelingtothe

fold-thrustbelt.

TheAqikestructureresultsfromtheinteraction

ofthedifferentdynamicmechanismsofWKFTBand

AFTB.Thestructureisformedintwostages:

（1）

Pliocene-Pleistocene,WKFTBinthewesternsideof

theAqikestructurethruststowardNNE,whilethesin-

istralstrike-slippingoftheAltunfaultsysteminthe