Clinopyroxene from basaltic rocks of the ErzgebirgeKru né hory Mtsimplications for modelling the magmatic plumbing syste.docx

《Clinopyroxene from basaltic rocks of the ErzgebirgeKru né hory Mtsimplications for modelling the magmatic plumbing syste.docx》由会员分享，可在线阅读，更多相关《Clinopyroxene from basaltic rocks of the ErzgebirgeKru né hory Mtsimplications for modelling the magmatic plumbing syste.docx（24页珍藏版）》请在第一文库网上搜索。

1、Origina1paperC1inopyroxenefrombasa1ticrocksoftheErzgebirge-KrusnehoryMts.-imp1icationsformode11ingofthemagmaticp1umbingsystemRomanRONICK,Axe1D.RENNOi*,TechnischeUniversi1atBergakademieFreiberg,InstituteofMinera1ogy,Brennhausgasse14,D-09596Freiberg,Germany;axe1.rennominera1.tu-freiberg.de*Correspondi

2、ngauthorTheErzgebirge-KrusnehoryareaispartoftheNWf1ankoftheEger-OhfeRift.Withinthisrift-re1atedarea,basa1ticrockswith1ow(3.5wt.%)ofTiO:occur.Thedistributionofthesebasa1ticrocktypesshowsstrongspatia1dependency.Ti-richbasa1tsareconcentratedinthewesternErzgebirge-KrusnehoryMts.withasharpchangeat1ongitu

3、de13.3E.C1inopyroxeneando1ivinearethemostabundantphenocrysts.Thezoningandchemistryofthec1inopyroxeneactasarecorderofthedifferentstagesofthemagmaticp1umbingsystems.Sevendifierenttypesofc1inopyroxenephenocrystsaredefinedwithfourdistinctchemica1types:Cr-richc1inopyroxene,green-corepyroxene,Mg-richc1ino

4、pyroxeneandfine1yzonedTi-richc1inopyroxenewithsectorzoning.Chemica1andpetrographicana1ysisofindividua1zoneswithinc1inopyroxenesa11owsthequa1itativedescriptionofdistinctstepsofthemu1tistage,regiona11ydiverseprocessesyie1dingtotheformationofbothTi-richbasa1tsintheWaswe11asTi-poorbasa1tsintheE.Twodiffe

5、renttypesofasthenosphericme1tsaresuggested,withincreasedactivitiesofH：OandpotassiuminthewesternErzgebirgeMts.Duringascenttheyincorporatedxeno1ithsandxenocrystsofboththemant1e(peridotite,o1ivineandCr-richc1inopyroxene)andthecrusta1(graniticandgneissicrocks,quartzandfe1dspar)origin.Furthennore,greenco

6、resOfc1inopyroxenewereintroducedintothemagmas.Fractionationprocessestookp1acewithin1ithosphericnagmachambers,havingbeenaccompaniedbyreactionofxenocrystsandxeno1ithswiththeme1t.TheresidencetimeinthemagmachambersassociatedwiththeeasternandwesternpartsoftheErzgebirgeappearstohavebeentota11ydifferent:sh

7、ortintheeasternand1onginthewesternparts.Withinthe1atter,nomant1e-derivedxeno1iths,xenocrysts,ormagmatico1ivinesarefound.Itisinferredthatthesexeno1ithsandcrysta1ssett1edtothebottomofthemagmachambersformingcumu1atesandthereforedidnotcometothesurface.Incontrast,thebasa1ticrocksoftheEaststi11containmant

8、1e-derivedxeno1ithsandxenocrystsaswe11asmagmatico1ivine.Thesizeandamountofc1inopyroxenephenocrystsintheWestsignificant1yexceedthatoftheEast.Moreover,thecrysta11izationofgiantc1inopyroxeneswasrestrictedtothewesternregion.MixingofthemagmaswithTi-richme1ts,presumab1yderivedfromanec1ogiticsource,tookp1a

9、ceincrusta1magmachambers.Inanycase,theproportionofTi-richme1tsintheWestsignificant1yexceededthatoftheEast.Keywords:petro1ogy.CrySta1chemistry,c1inopyroxene,basa1t.Erzgebirge-Krusnehory,green-corepyroxeneReceived:6Apri12010：accepted:20September2010：hand1ingeditor:V.Rapprich/R.Skd1aTheon1ineversionoft

10、hisartic1e(doi:1().3190jgeosci.077)containssupp1ementarye1ectronicmateria1.1.IntroductionDespitetheeye-catchinggeochemica1characterof477-richbasa1tsitisunc1earifthisfeatureisavagaryofnatureoranimportantgeochemica1fingerprintab1etodiscriminatebetweendifferentsourceregionsofbasa1ticrocks.Besideswe11kn

11、ownHigh-Tibasa1tsfromthemoon(Papikeeta1.1976;PapikcandVaniman1978),whichhavenoterrestria1equiva1ent,High-Tibasa1tsarefoundindifferentgeotectonicsettings,suchasContinenta1F1oodBasa1ts(CFB),1argeIgneousProvinces(1IP)(Gibsoneta1.1995),orrift-1ikeintrap1atcsettings(Piketa1.1998).Theoccurrenceofsuchbasa1

12、tsisnotrestrictedto1avas;theyappeara1soindikesystems(EssawyandE1-Metwa11y1999;Katzireta1.2006)andintrusionsofgabbroicrocks(JamaAdenandFrizzo1996).ThciragespansfromtheArchaeantorecent.Theoriginineachofthegeotectonicenvironmentsremainscontroversia1.Theproposedexp1anationsin11Psrangefromahighdegreeoffr

13、actionation(Fodor1987),1owdegreeofpartia1me1ting(Dupuyeta1.1988),crusta1contamination(Fodor1987),totheinf1uenceofsubcontinenta1Iithosphcremobi1izedbysubduction(Duncan1987;Murphy1988).Itisassumedthattheeffectofmant1ep1umesisthemaincauseforthegenesisofTi-richrocksinrift-1ikesettings(Piketa1.2006).Aqua

14、1itativeapproachtounderstandingpetro1ogica1processesresponsib1eforthegenesisofTi-richbasa1tsthroughthecomprehensivestudyofthemicrostructureandminera1chemistryofc1inopyroxeneisdemonstratedintheWWW.Jgeosc1ORcurrentpaper.AsacasestudyhavebeenchosenCenozoicbasa1ticrocksfromtheEger-OhfeRift(Erzgebirge-Kru

15、SnehoryMts,BohemianMassif).A1thoughwedonotpresentacomp1etegeneticmode1,thisstudydoesprovideabasisforunderstandingthenatureandgenesisofthehigh-Tibasa1ts,bothinthisregionande1sewhere.2. Geo1ogica1settingAccordingtoProdeh1eta1(1995)theEger-OhfeRift,aspartoftheEuropeanCenozoicRiftSystem(ECRS),isoneofthe

16、majorextensiona1structuresinCentra1Europe.Thestructureitse1fissituatedinProterozoictoPa1eozoicbasementrocksoftheBohemianMassif(Ma1kovsky1987;MIochandKonopasek2010)andshowsane1ongationofrough1y300kmandawidthupto30km.ThewesternpartoftheEgerRift1iesonaVariscansuturezonebetweentwo1ithosphericb1ocks:theSaxothuringianandtheTep1a-Barrandianterranes(Hrubcovaeta12005;Babuskaeta12007).Thetherma1thicknessofthe1ithosphere