2015-INAEYN-UCAS-1-GlobalTectonics

我们继续吧！牛耀龄(YaolingNiu)EarthSciences英国杜伦大学（DurhamUniversity）地球科学系Theme:GlobalTectonicsandGeodynamics–APetrologicalandGeochemicalApproachTopics:0-Selfintroduction&magmatism1-Geologicalunderstandingofglobaltectonics:Basicconcepts,illustrations,examplesandnewperspectives2-Globalmid-oceanridgedynamics-apetrologicalperspective3-Debateonthesourcesofoceanislandbasalts(OIB)4-Lid-effectonthecompositionofoceanislandbasalts(OIB)5-Apetrologicalperspectiveonmantleconvection6-Whatdrivesplume-ridgeinteractions?7-Thenatureofthelithosphere-asthenosphereboundary(LAB)8-Tectonicsettingandmechanismofcontinentalcrustaccretion9-Testingmantleplumehypothesis1-Geologicalunderstandingofglobaltectonics:Basicconcepts,illustrations,examplesandnewperspectivesEffectsofwesternPacificsubductiononthegeologyofeasternChinasincetheMesozoic–地幔柱大辩论ChineseScienceBulletin(YaolingNiu,1537-1540,2005)Acaseformantleplumes(GeoffreyDavies,CSB,1541-1554)Mantleplumes:Whythecurrentscepticism?(GillianFoulger,CSB,1555-1560)Foulgeretal.,GSASpecialPapers,2005PlateTectonics:ProvenTheory(Platemotion,plateboundaryzoneprocessesetc.)Mantleplumes:GoodHypothesis(Intra-plateprocesses,LIPsetc.)totestwithchallenges!PlateTectonicsTheory&MantlePlumeHypothesis(ExplainmuchofthewholepictureofEarthprocesses)CoreDavies,G.F.,Richards,M.A.,1992.Mantleconvection.JournalofGeology100,151-206.PlateTectonics(oranges)(ridges,trenches)drivenbythetopcoldTBLandcoolsthemantleMantlePlumes(apples)drivenbythebasalhotTBLattheCMBandcoolsthecorePlateTectonics&MantlePlumeshaveNogeneticconnection!!But,whenmantleplumesrisetoreachthelithosphericplates,interactionbetweenthetwotakesplace!!Thelithosphereisthethinnestatridges,suchinteractionisbestexpressedasplume-ridgeinteractions!!俯冲带与全球构造俯冲带形成、后撤和板块构造动力学的一些基本概念和全新解释—全球意义、西太平洋弧后盆地的成因与演化及对中国东部的地质影响源于UNAVCO：板块运动的驱动力是什么？NorthAmericaPacificNazcaEurasiaSouthAmericaCocosCaribbeanAfricaArabiaIndo-AustraliaAntarcticPhilippineForsyth,D.W.&S.Uyeda,1975.Ontherelativeimportanceofthedrivingforcesofplatemotion,GeophysicalJ.R.Astr.Soc.,43,163-200.01020304050020406080100板块周长俯冲带部分（%）板块运动速度（mm/年）0120240360480600020406080100板块周长（102km）板块运动速度（mm/年）024487296120020406080100板块面积（106km2）板块运动速度（mm/年）050100150200250020406080100洋中脊长度（102km）板块运动速度（mm/年）SlabPull410km660km800100012001400温度（K）25201510压力（GPa）olivinewadsleyiteringwooditeperovskiteolivinewadsleyiteringwooditeperovskite俯冲板块等温线高密度相下拉低密度相上浮（源于UNAVCO：）所以，没有俯冲带就没有板块构造！显然，slabpull容易解释太平洋型海底扩张，周边有俯冲带，但不能解释大西洋海底扩张，更不能解释大陆漂移！但牛耀龄认为（2014）：俯冲过程“决定一切”！俯冲带是何时、何地、如何形成的？Niu等(2003)指出没有俯冲带就没有板块构造。俯冲带成因的研究从未中断(如McKenzie,1977;Karig,1982;Kemp&Stevenson,1996;Toth&Gurnis,1998),但实际收获甚微(Stern，2004；Gurnisetal.,2004;Stern等,2012;Shervais&Choi,2012；Marquesetal.,2014)。因为这些模型无法验证！“岩石圈内横向物质组成密度差是俯冲带形成的必要条件”（Niu等，2003）这是有关俯冲带成因模型中唯一可检验的假说！TongaMarianaFisher&Engel,GSABull.,80,1373-1378,1969.Hawkins,Fisher&Engel,GSA,4,167-168,1972.Bloomer&Fisher,J.Geol.,95,469-495,1987.Bloomer&Hawkins,AGUMonogr.,27,294-317,1983.Bloomer&Hawkins,CMP,97,361-377,1987.NOAAGeophysicalDataCenterConvergentplateboundaryArcVolcanicFrontForearcBackarcTrenchForearcPeridotiteexposedandsampled•Subductionzone•Trench,forearc,volcanicfrontandbackarcsystemMg/[Mg+Fe2+]-Spinel12345678910MarianaTongaSlowridge:1.AtlantisII2.Vulcan3.IslasOrcadas4.BullardHotspot-affectedslowridge:5.Bouvet6.14ºN7.Azores0.30.40.50.60.70.80.9Cr/[Cr+Al]-Spinel0.10.20.30.40.50.60.70.80.01.02.03.04.05.06.0Al2O3(wt%)-OpxCr/[Cr+Al]-Spinel12345678910MarianaTongaFastridge(EastPacificRise):8.Terevaka9.Garrett10.HessDeep0.10.20.30.40.50.60.70.8[AfterNiu&Hékinian,Nature,1997]比较:ARCMORMariana&TongaMid-oceanRidge前弧橄榄岩深海橄榄岩Cr#-Spinel0.584±0.0840.307±0.134Mg#-Olivine0.915±0.0060.898±0.082Mg#-Opx0.917±0.0060.908±0.006Mg#-Cpx0.929±0.0220.917±0.011Al2O3-Opx1.809±0.6474.103±1.161Extentofmelting~25%~20%Bulkdensity(g/cc;±2s)3.308±0.0083.330±0.007Dr(g/cc)by0.7%前弧橄榄岩深海橄榄岩EquivalenttoDT220°C洋脊地幔流•被动上升•减压熔融•中度部分熔融洋脊下和岛弧下地幔楔地漫流和源区构成明显对照俯冲带地幔楔对流•俯冲板块诱导的拐角流•加水熔融•高度部分熔融所以，这些科学家Bloomer,S.H.&J.W.Hawkind,AGUMonography,27,274-317,1983.Dick,H.B.&T.Bullen,CMP,86,54-76,1984.Bloomer,S.H.&R.LFisher,J.Geol.,95,469-495,1987.Bonatti,E.&P.J.Michael,EPSL,91,297-311,1989.Parkinson,I.J.&J.A.Pearce,39,1557-1618,1998.认为，前弧橄榄岩=地幔楔加水高程度部分熔融，所以亏损；深海橄榄岩=洋脊地幔减压熔融，所以不太亏损但是，这一解释从未证实。相反，我认为这一解释在关键问题上是错误的！I.地幔楔熔融残余上升到前弧海沟，太困难几乎不可能ArcVolcanicFrontForearcBackarcTrenchFP~75to150km-toodeep;Slab-inducedmantleflow-wrongwaySerpentinitediapirism-shallowfeature~75Km~150KmII.前弧橄榄岩是早期亏损熔融残余，与现代岛弧岩浆作用无关ArcVolcanicFrontForearcBackarcTrenchFPAnOs-isotopemodelageofMarianaFP-Proterozopic(820-1230Ma)[Parkinsonetal.,1998]TonganFP/lithospheremustbeoldertooalthoughitsdepletionageisyetunclear~75Km~150KmIII.汤加（Tongan）前弧玄武岩类组合式“干”岩浆，而非“湿”岩浆堆晶组合ArcVolcanicFrontForearcBackarcTrenchDry:Ol+Sp(dunite)Ol+Plag(Troctolite)Ol+Plag+Cpx…(Gabbroic)Wet:Ol+Sp(dunite)Ol+Cpx(Wehrlite)Ol+Cpx