沉積巖第4章變質(zhì)作用研究

1、第四章、第四章、變質(zhì)作用研變質(zhì)反應(yīng)與成巖格變質(zhì)變質(zhì)相系和雙變質(zhì)變質(zhì)巖原巖恢一、變質(zhì)反應(yīng)與成巖格一、變質(zhì)反應(yīng)與成巖格1、相律和相相律在一個封閉體系中，當變質(zhì)反應(yīng)達到平衡(StableMineraletamorphicEquilibriumMineralAtequilibrium,themineralogy(andthecom mineral) is determined by T, P, and Xitionof“Mineralparagenesis”referstosuchanequilibriumThePhasephaserule,asF=CThePhasephaserule,asF=C-+

2、dtosystemsatisthenumberofhesystem(相數(shù)Cisthenumberofcomponents:theminimumnumber of chemical constituents required to specify everyhesystem（獨立組分數(shù)Fisthenumberofdegreesoffreedom:thenumberindependently variable (suchastemperature,preensiveparametersofere,theitioneachphase,度ThePhaseetamorphicConsiderThePha

3、seetamorphicConsiderthefollowingthreeC=onlyatspecificP-Tconditions of the invariant po(0.37GPaandTheP-Tphasediagramforthesystem Al2SiO5 calculatedusingtheprogram TWQ(Berman,1988,1990,1991).WidtphaseidtphaseF=C- f +2fThisisidtsmineralogicalphaseorsimplythemineralogicalphasea) =etamorphicTherockprobab

4、lyrepresentsanequilibriummineralThePhaseetamorphic Common with mineral texhibitsolid存在流體相，或存在固溶ThePhaseAerestingsituation,eastoneAerestingsituation,eastoneofsituationsmustberesponsible（有三種狀態(tài)F Theleiscollectedfromalocationrightonunivariantreactioncurve(isogradorinvariantpo EquilibriumhasnotbeenThepha

5、serulesonlytosystemsatandtherecouldbeanynumberofmineralsifequilibriumisWedidntchoosethe#ofcomponents獨立組分數(shù)限定錯了相圖相圖(Phase2、變質(zhì)反2、變質(zhì)反基2、變質(zhì)反2、變質(zhì)反單成分相轉(zhuǎn)變(Isochemicalphasetransformations如SiO2 or Al2SiO5 graphite- diamondorcalcite-aragonite(Thetransformationsdependontemperatureandopx+pl=grt+cpx+qz;re葉臘石=and+

6、qz+H2O上述所上述所有反應(yīng)是一種理想化學(xué)反應(yīng)，說明反應(yīng)物與生成物之間的關(guān)系0.4GPa,0.4GPa,Kf+sill組合?qz具有具有固溶體礦物不連續(xù)反不連續(xù)反近乎一種突變變線（平衡）連續(xù)反3(Mg,Fe)2Al4Si5O18連續(xù)反3(Mg,Fe)2Al4Si5O18=堇青石榴子矽線石 石(Mg,Fe)5AlAlSi3O10(OH)+KAl2AlSiO10(OH)2 綠泥白云石黑云石連續(xù)反連續(xù)反在此反應(yīng)堇青石的形成，綠泥石和黑云母不完全連續(xù)反定義：在連續(xù)反定義：在涉及固溶體的反應(yīng)中，生成物的形成內(nèi)連續(xù)反應(yīng)或滑動反應(yīng)D+G+F+H；D+G+F+H；A+C+E+F；。Continuousocc

7、urwhenF1,ContinuousoccurwhenF1,andreactantsandproductscoexistoveratemperatureSchematicisobaricrepresenting the metamorphicreaction Chl + Qtz Grt +equalibriuminafield with F=2.不同不同型反定（對反應(yīng)的影。定（對反應(yīng)的影。P-T-3、3、成巖格子和地質(zhì)溫壓Petrogeneticgridand定義：由多個反應(yīng)曲線或相圖組合而成的P-T間的反應(yīng)曲線網(wǎng)格圖解成巖格3、3、成巖格子和地質(zhì)溫壓3、3、成巖格子和地質(zhì)溫壓成巖格子成巖格

8、子地質(zhì)溫壓變質(zhì)作用溫壓的確定方法Ky- grt- sill- kf-pl-bt- 矽線石片麻(1成巖格成巖格子確定平衡溫壓的優(yōu)缺點優(yōu)點：簡單，快缺點：不夠精確(結(jié)果是一個很大的范圍(2)、地質(zhì)(2)、地質(zhì)溫壓原理：熱力學(xué)平衡，平衡礦物為固溶體，反應(yīng)物與G=0G0G=0G0 +RTG0 =-RTForreaction:2A+3B=C+K=(C.D )/(A .B A=XA. K=KD . K G=H dG= VdP- lnK=lnKD +lnK=-H0/RT+S0/RGarnet-BiotiteFeGarnet-BiotiteFe3Al2Si3O12+KMg3Si3AlO10(OH)2 =+ l

9、nK=K=KD = =Ferry & Spear lnKD =-H0/R.(1/T)+Ferry&SpearTheGarnetBiotitegeothermometer（實驗標定Experimental results of Ferry and Spear (1978) on a Garnet-Biotite GeothermometerTKFerry&SpearTheGarnetBiotitegeothermometer（實驗標定Experimental results of Ferry and Spear (1978) on a Garnet-Biotite GeothermometerT

10、KTGarnet-Garnet-lnKD =-2108/T(K)+GP,T =0=GP,T =0=0.1,298 -TS0.1,+PV+3ToC 52,0902.494PMPa 19.50612.943lnKDln HPV 1 TTheTheGarnet-BiotiteTheGASPP-T phase diagram showing the experimental results of Koziol and Newton(1988),TheGASPP-T phase diagram showing the experimental results of Koziol and Newton(1

11、988),andtheequilibrium curve for reaction. Open triangles indicate runs in which An grew, closed triangles indicate runs in which Grs + Ky + Qtz grew, and half-filled triangles indicate no significant reaction. The univariant equilibrium curve is a best-fitofthedatabrackets.line at 650oC is Koziol a

12、nd Newtons estimate of the reaction location based on reactions involvingzoisite.Theshadedareaistheyenvelope.KoziolandNewton(1988)Amer. Mineral., 73, 216-233TheGASPTheGASPP-T diagram contoured for equilibrium curves of various values of K for the GASPgeobarometerreaction:3An=Grs+2Ky+Qtz.FromSpear(19

13、93)不不同溫度計和壓力計的組不不同溫度計和壓力計的組bt-Ferrybt-Ferry&Spear(1978);Hodges&Spear(1982);Ganguly&(1984);Perchuketal.(1983);Indaresetal.cpx-opx,Wood&Banno(1973);Wells(1977);Bertrand&Mercier(1985); Brey & Kohler (1990)cpx-gt,Ellis&Green(1979);Harley(1984);kf-pl,StomerJr.(1975);Priceetal.gt-opx,Wood(1974);Nickel&Gre

14、en(1985);Harleygt-cpx-pl-qz,Newton&Perkinsgt-pl-AS-qz,Ghentetal(1976,gt-pl-bt-ms,Ghentetal(1981);Ashworth(1985);Hoisch必須必須存在這樣的礦物組合；如gt-cpx-pl-礦物成分和巖石組合的限制，如Perchuk et 0.22XMgBt 0.83,gt:0.05XMgGt 0.77；如Brey&Kohler(1990)的二輝石溫計只適用于橄欖巖體系，即具ol+opx+ cpx+gt (or sp)組合。計算步驟計算步驟礦物的成分分析(如電子探針分子結(jié)構(gòu)式的計算，分配系數(shù)的確定優(yōu)

15、點: 精確，誤差小(50100; 缺點: 局限（要求嚴格），繁瑣，花大4、P-T-t軌4、P-T-t軌ConsiderthecompletesetofT-Ptamay experience during a metamorphic cycle from burialtometamorphism(andorogeny)toupliftand，Suchacycleiscalleda-timepath,orP-T-tP-T-t軌跡P-T-t軌P-T-t軌跡的確礦物間的包含關(guān)系，交代特征，判斷哪些利用具成分環(huán)帶的礦物的核部到邊緣的I.I.等溫降等溫降ChemicalChemicalzoningprof

16、ilesacrossagarnetfromtheTauernWindow.AfterSpearConventionalP-TdiagramConventionalP-Tdiagramreincreasesupward)showingthreeed “clockwise”T-tpathscomputedfromtheprofilesusingthemethodofSelverstoneetal.re-temperature-timere-temperature-timepathsbasedonheat-flows.Al2SiO5phasediagramandtwohypotheticaldehy

17、drationcurvesarePathis considered aPathis considered atypicalP-T-t path for an orogenic belt with crustal 在增厚的階段，P迅速增加，而T升高緩慢P，T同時下降，由于隆升和剝蝕整個過程地溫梯度發(fā)生很大變化這種模式被稱為順時針(clockwiseP-T-t軌SchematicP-T-tpathsforaSchematicP-T-tpathsforashallowmagmatismPathflow.Due to shallowThismaybean appropriate P- T-t path

18、 for PathP-T-t path見于高PathP-T-t path見于高級片麻P-T同時增加侵入活動結(jié)束變降溫發(fā)生等P-T-tpathsbasedonaheat-flowfortypesofgranulitefacies溫壓并不一定同步升高或降低質(zhì)作用中有很大變化；Pmax andTmax溫壓并不一定同步升高或降低質(zhì)作用中有很大變化；Pmax andTmax 并不同時達到heusualcaseof“clockwise”P-T-tpaths,Pmax occursnTmax shouldrepresentumgradeatwhichequilibriumis“frozenin”andthe

19、metamorphicmineral assemblage is developed;“Metamorphicgrade”shouldrefertothetemperatureandpre at Tmax, because the grade is determined via reference to the equilibrium mineral assemblage;3.順時針P-T軌跡的隆升-ThekyanitesillimanitetransitionThekyanitesillimanitetransitionisgenerallyconsideredaprogradecrosse

20、sthekyanitesillimanitetransition(asin1),but2temperatureisdecreasing.Thismayresultinonlyminorreplacementofkyanitesillimaniteduringsucharetrogrades二、變質(zhì)帶(metamorphiceBarrow(1893,二、變質(zhì)帶(metamorphiceBarrow(1893,在研究SEHighlandsScotland的加里東造山帶Caledonianorogeny500 Ma)的Regional Metamorphism時建立的。Barrowstudiedth

21、epelitichisAndfoundtheareacouldbeoaseriesmetamorphiczones,eachbasedontheappearance of a new mineral as metamorphic grade increasedTheyarechlorite,biotite,garnet,staurolite,kyanite and sillimanite zones.map of the map of the showing the zones oftdevelop with grade. From Gillen(1982)ThesequenceofThese

22、quenceofzonesnowrecognized,andtypicalmineralassemblageineach,Chloritezone.Peliticrocksareslatesorphyllitesandtypically contain chlorite, muscovite, quartz and albiteBiotitezone. Slatesgivewaytophyllitesandschists,with biotite, chlorite, muscovite, quartz, and albiteGarnetzone.Schistswithconspicuousr

23、edalmandinegarnet, usually with biotite, chlorite, muscovite, quartz, and albite or Staurolitezone.Schistswithstaurolite,biotite,muscovite, quartz, garnet, and plagioclase. Some chlorite may persistKyanitezone.Schistswithkyanite,biotite,muscovite,quartz, plagioclase, and usually garnet and staurolit

24、e.Sillimanitezone.Schistsandgneisseswithsillimanite,biotite, muscovite, quartz, plagioclase, garnet, and perhaps staurolite. Some kyanite may also be present (although kyanite and sillimanite are both polymorphs of Al2SiO5)=Barrovianzones系）（The P-T conditions referred toasBarrovian-type 等變線(Isograd)

25、tthe zones (a line in the field of constant metamorphicgrade)To一個To一個等變線代表一個特征變質(zhì)礦物的第一次出現(xiàn)Anisogradhisclassicalsense)representsappearanceofaparticularmetamorphicindex通過這個等變線，意味著進入了這個變質(zhì)帶(Whenonecrossesanisograd,suchasthebiotiteisograd, one enters the biotite zone）相同原巖的每個變質(zhì)帶形成于相同條件（等物等變線是以一個特征礦物出現(xiàn)為標志，并不

26、涉及消AtypicalBarrovian-typeAtypicalBarrovian-typemetamorphicfieldgradientandaseriesmetamorphicP-T-tpathsforrocksfoundtheAb-Ab-ab+chl+epqzcc,ab+act+ep+chlqz陽起石出現(xiàn)=黑云母出Ab-ab+hb(藍綠色陽起石普通角閃石主要是2Al=Si+(Mg, Fe)置Pl-Two-Hb+alm+5qz7opx+pl+H2OAvariationheareaAvariationheareajusttothenorthhendBuchanHerethepelitic

27、itionsarebutthesequenceofisogradsThestabilityfieldThestabilityfieldofandalusiteoccursatresn0.37GPa(10km),whilekyaniteisogradisabovethisContact Metamorphism and FormationContact Metamorphism and FormationatCrestmore,CA,Anidealizedcross-sectionthroughtheIdealizedN-S cross section (not to scale) throug

28、h the and the aureole at CA. From 三、變質(zhì)相(Metamorphic三、變質(zhì)相(MetamorphicEskola(1915)developedtheconceptof metamorphic facies:Definition:變質(zhì)相就是一個特定的變質(zhì)溫壓條三、變質(zhì)相(Metamorphic變質(zhì)三、變質(zhì)相(Metamorphic變質(zhì)相概念的兩個基本特征是相似于沉積相的概念，即不同的沉積環(huán)境等同于不同的變質(zhì)環(huán)境三、變質(zhì)相(MetamorphicEskola(1920)ed5original三、變質(zhì)相(MetamorphicEskola(1920)ed5orig

29、inalhibolite角閃巖Hornfels角透長巖e 榴輝巖EclogiteMetamorphicInhisfinalaccount,EskolaMetamorphicInhisfinalaccount,Eskola(1939)麻粒巖相Granulite hibolite綠簾角閃巖藍片巖相Glaucophane-Hornfelsfacieschangedtothepyroxenehornfels EacheasilydefinedonthebasisoftaficHisfacies,andhisestimateoftheirrerelationshipsareshownMetamorphi

30、cThemetamorphicfaciesMetamorphicThemetamorphicfaciesedbyEskolaandtheirtemperature-rerelationships.AfterEskolaFormation of ZeolitesSchistMetamorphic從那以后，sMetamorphic從那以后，s在研究New Zealan的埋深變質(zhì)時增加了沸石相(Zeolite)和葡萄石石；Fyfe et al(1958)也提出（增加）了鈉長-綠簾角巖相dote hornfels)和角閃石角(Hornblende hornfels)現(xiàn)在被普遍接受的變質(zhì)相有11個，包括

31、4個觸變質(zhì)作用中的和7個區(qū)域變質(zhì)作用中的MetamorphicMetamorphicT-P diagram showing the acceptedlimits of the various Boundaries are approximate and gradational. The “typical” or geothermisfrom Brown and Mussett (1993).MetamorphicThedefinitivemineralassemblages facies (for mafic rocks).tcharacterizeTable25-1.DefinitiveMi

32、neralAssemblagesofMetamorphicDefinitiveMineralaficPrehnite-prehnite+pumpellyite(+chlorite+chlorite+albitedote(orMetamorphicThedefinitivemineralassemblages facies (for mafic rocks).tcharacterizeTable25-1.DefinitiveMineralAssemblagesofMetamorphicDefinitiveMineralaficPrehnite-prehnite+pumpellyite(+chlo

33、rite+chlorite+albitedote(orzoisite)+quartz?hornblende+plagioclase(oligoclase-andesine)?orthopyroxene(+clinopyrixene+plagioclase?glaucophane+lawsonitedote(+albite?pyropegarnet+omphaciticpyroxene(?Mineral afic rocks of the facies of contact Contactmorphism do not differ substantially t of the regional

34、 facies at After Spear 可以把變質(zhì)相分成4組高可以把變質(zhì)相分成4組高壓相（FaciesofhighTheblueschistandeclogiteBlueschistfacieslower-temperatureandlowT/P gradients subduction zones.因為eclogite可以穩(wěn)定于正常的地溫條件下，（Becauseeclogitesarestableundernormalconditions,theymaydevelopwherevermafichedeepcrustormantle(crustalchambersdikes,sub-cr

35、ustalmagmaticlates,subductedtisotheFaciesofmediumre中壓相ranuliteFaciesofmediumre中壓相ranuliteFaciesoflowre低壓相Thedotehornfels,hornblendehornfels,pyroxene hornfels facies: contact metamorphic terranes and regional terranes with very high geothermalgradients.Thesanidinitefaciesisrare and limited to xenolit

36、hs in basic magmasFaciesoflowgrades低級相Thezeoliteandprehnite-pumpellyitefaciesarethus notalwaysrepresented,andthegreenschistfaciesisthelowestgradeanyregional變質(zhì)亞變質(zhì)亞巴羅變質(zhì)帶Chlzone=巴羅變質(zhì)帶Chlzone=lowgreenschistBiGtStKy =lowgreenschist=highgreenschist=hibolitehibolite facies hiboliteSillzone=基性變質(zhì)帶：Ab-chllowgreenschistAb-act=highgreenschistAb-=hibolitePl-=hibolite2-pyroxene=granulite四、變質(zhì)相系(facies四、變質(zhì)相系(facies(Miyashiro1963FigureFigure21-1.Metamorphicfieldgradients(estimatedP-Tconditionsalongsurfacetraversesdirectlyupmetamorphicgrade) for