subduction factory: its role in the evolution of the solid earth y.tatsumi (ifree, jamstec) ・...

Subduction Factory:Subduction Factory:Its Role in the Evolution of the Solid EarthIts Role in the Evolution of the Solid Earth

Y.Tatsumi (IFREE, JAMSTEC)Y.Tatsumi (IFREE, JAMSTEC)

・ Outline of subduction factory・ General characteristics of magmatism and basalt genesis・ Andesite genesis and continental crust formation・ Fate of waste materials and mantle evolution

Institute for Frontier Research on Earth EvolutionInstitute for Frontier Research on Earth Evolution

Yoshiyuki TatsumiYoshiyuki Tatsumi

The Subduction FactoryThe Subduction Factory

Raw materials■Oceanic material■Mantle material

Products■Magma/Volcanoes■Volatiles■Continental crust

Residues■Chemically modified slab■Delaminated lower crust



General CharacteristicsGeneral Characteristicsof Arc Magmatismof Arc Magmatism

・ Dual volcanic chains

・ Inverse correlation between arc width and subduction angle

・ High-T mantle wedge and hot fingers

・ Selective enrichment of LIL elements



Volcano Distribution Volcano Distribution in NE Japan Arcin NE Japan Arc



Distance from Volcanic FrontDistance from Volcanic Front vs.vs. Number of Volcanoes Number of Volcanoes



General Characteristics General Characteristics of Arc Magmatismof Arc Magmatism







Subduction Angle Subduction Angle vs.vs. Arc Width Arc Width



Constant Depth to Slab SurfaceConstant Depth to Slab Surface



Hydrous Phases Stability:Hydrous Phases Stability:BasaltBasalt



Migration of FluidsMigration of Fluids



Hydrous Phases Stability:Hydrous Phases Stability:PeridotitePeridotite



Formation of Hydrous CurtainsFormation of Hydrous Curtains







General Characteristics General Characteristics of Arc Magmatismof Arc Magmatism



Generation of Arc Basalt MagmasGeneration of Arc Basalt Magmas

Tatsumi et al. (1983)



Seismic Tomography ImageSeismic Tomography Imagebeneath NE Japanbeneath NE Japan

Zhao et al. (1992)



Numerical Simulation ExperimentsNumerical Simulation Experiments

Furukawa (1993)



Heterogeneous Volcano DistributionHeterogeneous Volcano Distributionin NE Japan Arcin NE Japan Arc



Heterogeneous Distribution Heterogeneous Distribution of High-T Mantle Wedgeof High-T Mantle Wedge



Heterogeneous DistributionHeterogeneous Distributionof High-T Mantle Wedgeof High-T Mantle Wedge



Hot Fingers in the Mantle WedgeHot Fingers in the Mantle Wedge



General CharacteristicsGeneral Characteristicsof Arc Magmatismof Arc Magmatism







Trace Element CharacteristicsTrace Element Characteristics

Subduction zone basalt



Starting MaterialsStarting Materials■Plate-forming hydrous materials such as sediments/amphibolites■Being set in a perforated platinum capsule

High-P/T Dehydration ExperimentsHigh-P/T Dehydration Experiments■Decomposition of starting materials■Releasing H2O that dissolves elements■Leaving anhydrous residue■Chemistry: starting materials vs. residue

Element Transport during DehydrationElement Transport during Dehydration



Element Transport Element Transport via.via. Dehydration Dehydration



Inferred Arc Magma CompositionsInferred Arc Magma Compositions



Origin of Andesites and Origin of Andesites and Continental CrustsContinental Crusts

・ Calc-alkalic vs. tholeitic andeistes

・ Bulk continental crust: 　 andesitic, not basaltic compositions



Arc Magmas Arc Magmas vs.vs. Continental CrustContinental Crust

THCA



Characteristics of Calc-Alkalic AndesitesCharacteristics of Calc-Alkalic Andesites

Rather straight differentiation trend Disequilibrium phenocryst assemblages (e.g., ol+qz) Presence of reversely-zoned phenocryst

Bimodal distribution of phenocryst-core compositions

A Plausible Mechanism:--mixing of basaltic and felsic magmas

Origin of End-member Magmas •Basalt magma:mantle-derived•Felsic magma:external or internal origin?



Crustal Origin for Felsic MagmasCrustal Origin for Felsic Magmas



Ancient Ancient MORBMORB

Ridge Ridge AlterationAlteration

ElementElementTransportTransport

Slub Slub FluidFluid

Ancient Altered Ancient Altered MORBMORB

Ancient Magma SourceAncient Magma Source

AncientAncientOriginal Mantle WedgeOriginal Mantle Wedge(Primitive Mantle)(Primitive Mantle)

ancient Primary Basaltancient Primary BasaltInitial Arc CrustInitial Arc Crust

Remolten Felsic Remolten Felsic Magma Magma

ContinentContinental crustal crust

Mix

ing

Mix

ing

Andesitic Continental Crust FormationAndesitic Continental Crust Formation

Primary BasaltPrimary Basalt

Magma SourceMagma SourceOriginal Original Mantle WedgeMantle Wedge(N-MORB Source)(N-MORB Source)

ElementElementTransportTransport

Slub Slub FluidFluid

Altered MORBAltered MORB Fresh MORBFresh MORB

Ridge AlterationRidge Alteration



Inferred AndesitesInferred Andesitesproduced by Magma mixingproduced by Magma mixing



Delamination

Andesite

Restite

Bas

alti

c C

om

p.

DelaminationDelamination

Initial Arc Crust

Dacite

Restite

Anatexis/Mixing

Basalt

Mix

ing

Mix

ing

Delamination Process Delamination Process RequiredRequired



Fate of Waste MaterialsFate of Waste Materials

・ Oceanic crust (dehydrated and fresh)

・ Sediments

・ Delaminated anti-continental crust



Isotopic characteristicsIsotopic characteristicsof Oceanic Magmasof Oceanic Magmas



Chemical ModificationChemical Modificationof Altered Oceanic Crustof Altered Oceanic Crust

Element Transport via. Dehydration



Isotopic Evolution of Sinking CrustsIsotopic Evolution of Sinking Crusts



Chemical ModificationChemical Modificationof Subducting Sedimentsof Subducting Sediments

Element Transport via. Dehydration



Isotopic Evolution of Sinking SedimentsIsotopic Evolution of Sinking Sediments



Isotopic EvolutionIsotopic Evolutionof Delaminated Arc Crustof Delaminated Arc Crust



Material Recycling in the Earth Interior



The Subduction FactoryThe Subduction Factory

Raw materials■Oceanic material■Mantle material

Products■Volcanoes■Volatiles■Continental crust

Residues■Chemically modified slab■Delaminated lower crust



I F R E EI F R E EInstitute for Frontier Research on Earth EvolutionInstitute for Frontier Research on Earth Evolution

subduction factory: its role in the evolution of the solid earth y.tatsumi (ifree, jamstec) ・...

Documents

frontier research

mantle evolution slide

basalt slide

arc width slide

tatsumi ifree

peridotite slide

surface slide

t mantle wedge slide