Subduction Factory:
Its Role in the Evolution of the Solid Earth
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
The Subduction Factory
Raw materials
■Oceanic material
■Mantle material
Products
■Magma/Volcanoes
■Volatiles
■Continental crust
Residues
■Chemically modified slab
■Delaminated lower crust
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
General Characteristics
of 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
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Volcano Distribution
in NE Japan Arc
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Distance from Volcanic Front
vs. Number of Volcanoes
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
General Characteristics
of 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
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Subduction Angle
vs. Arc Width
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Constant Depth to Slab Surface
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Hydrous Phases Stability:
Basalt
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Migration of Fluids
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Hydrous Phases Stability:
Peridotite
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Formation of Hydrous Curtains
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
General Characteristics
of 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
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Generation of Arc Basalt Magmas
Tatsumi et al. (1983)
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Seismic Tomography Image
beneath NE Japan
Zhao et al. (1992)
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Numerical Simulation Experiments
Furukawa (1993)
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Heterogeneous Volcano Distribution
in NE Japan Arc
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Heterogeneous Distribution
of High-T Mantle Wedge
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Heterogeneous Distribution
of High-T Mantle Wedge
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Hot Fingers in the Mantle Wedge
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
General Characteristics
of 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
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Trace Element Characteristics
Subduction zone
basalt
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Element Transport during Dehydration
Starting Materials
■Plate-forming hydrous materials such as
sediments/amphibolites
■Being set in a perforated platinum capsule
High-P/T Dehydration Experiments
■Decomposition of starting materials
■Releasing H2O that dissolves elements
■Leaving anhydrous residue
■Chemistry: starting materials vs. residue
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Element Transport
via. Dehydration
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Inferred Arc Magma Compositions
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Origin of Andesites and
Continental Crusts
・Calc-alkalic vs. tholeitic andeistes
・Bulk continental crust:
andesitic, not basaltic compositions
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Arc Magmas vs.
Continental Crust
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Characteristics 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


Origin of End-member Magmas
A Plausible
Mechanism:
•Basalt
magma:mantle-derived
--mixing
of
basaltic
and
felsic
magmas
•Felsic magma:external or internal origin?
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Crustal Origin for Felsic Magmas
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Andesitic Continental Crust Formation
Ancient
MORB
Primary Basalt
Element
Transport
Magma Source
Slub
Element Fluid
Transport
Ridge
Alteration
Ancient Altered
Original
MORB
Mantle Wedge
(N-MORB Source)
Ancient
Original Mantle Wedge
(Primitive Mantle)
Slub Fluid
Ancient Magma Source
Altered MORB
ancient Primary Basalt
Initial Arc Crust
Ridge Alteration
Remolten Felsic
Magma
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Fresh MORB
Continent
al crust
Inferred Andesites
produced by Magma mixing
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Delamination Process Required
Anatexis/Mixing
Dacite
Restite
Delamination
Andesite
Restite
Basalt
Delamination
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Basaltic Comp.
Initial Arc Crust
Fate of Waste Materials
・Oceanic crust (dehydrated and fresh)
・Sediments
・Delaminated anti-continental crust
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Isotopic characteristics
of Oceanic Magmas
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Chemical Modification
of Altered Oceanic Crust
Element Transport via. Dehydration
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Isotopic Evolution of Sinking Crusts
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Chemical Modification
of Subducting Sediments
Element Transport via. Dehydration
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Isotopic Evolution of Sinking Sediments
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Isotopic Evolution
of Delaminated Arc Crust
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
Material Recycling in the Earth Interior
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
The Subduction Factory
Raw materials
■Oceanic material
■Mantle material
Products
■Volcanoes
■Volatiles
■Continental crust
Residues
■Chemically modified slab
■Delaminated lower crust
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution
IFREE
Institute for Frontier Research on Earth Evolution
Yoshiyuki Tatsumi
Institute for Frontier Research on Earth Evolution