when did plate tectonics begin on planet earth• the onset of plate tectonics is not an event, but...
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WHEN DID PLATETECTONICS BEGIN ON
PLANET EARTH ?
Kent C. CondieDepartment of Earth and Environmental Science
New Mexico TechSocorro, NM 87801 USA
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3000
2800
2600
2400
220001.02.03.04.0
Time (Ga)
1018
1017
1016
1015Temperature
Viscosity
MANTLE EVOLUTION
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POSSIBLE PLATE TECTONIC RETURNS
1. Asymmetric Subduction 2. Symmetric Subduction
3. Plate Sinking
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Distance (km)
Figure Courtesy of Steve Holbrook
New Continental Crust is formed in arcs
such as the Aleutian Arc
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Pillow basalts
Andesites
Breccia
Felsic volcanics
Graywackes
Boninites
Melange
ISLAND
ARCS
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Pillow basalts
Andesites
Breccia
Felsic volcanics
Graywackes
Boninites
Melange
ISLAND
ARCS
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Pillow basalts
Andesites
Breccia
Felsic volcanics
Graywackes
Boninites
Melange
ISLAND
ARCS
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Pillow basalts
Andesites
Breccia
Felsic volcanics
Graywackes
Boninites
Melange
ISLAND
ARCS
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Pillow basalts
Andesites
Breccia
Felsic volcanics
Graywackes
Boninites
Melange
ISLAND
ARCS
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Pillow basalts
Andesites
Breccia
Felsic volcanics
Graywackes
Boninites
Melange
ISLAND
ARCS
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Pillow basalts
Andesites
Breccia
Felsic volcanics
Graywackes
Boninites
Melange
ISLAND
ARCS
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3.4
2.7Foreland Basins
Passive Margins
3.1Arcs
2.7
Continental Rifts3.0
1.0 2.0 03.0Ga
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Accretionary Prisms
3.0 Ga 1.0 2.0 0
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3.0 Ga 1.0 2.0 0
2.7Foreland Basins
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DEVELOPMENT OF PASSIVE MARGINS
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3.0 Ga 1.0 2.0 0
Passive Margins2.7
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3.0 Ga 1.0 2.0 0
Continental Rifts3.0
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3.0 Ga 1.0 2.0 0
3.4Metallic Mineral Deposits
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Accretionary Prisms3.1
Arcs
2.7Foreland Basins
Passive Margins2.7
Continental Rifts3.0
3.0 Ga 1.0 2.0 0
3.4Metallic Mineral Deposits
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3.3
Paired Metamorphic Belts
3.0 Ga 1.0 2.0 0
Subduction zones are coldSubduction zones are cold
Backarcs are hotBackarcs are hot
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3.0 Ga 1.0 2.0 0
Large Transcurrent Faults
3.2
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3.0 Ga 1.0 2.0 0
Accretionary Orogens
3.7
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3.0 Ga 1.0 2.0 0
Collisional Orogens
2.2
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PALEOMAGNETISM ALLOWS THE
RECONSTRUCTION OF SUPERCONTINENTS
SUCH AS GONDWANA SOME 600 Million years
ago
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3.0 Ga 1.0 2.0 0
Paleomagnetism3.0
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10
100
0 10 20 30
Zr/Nb
Nb/Th
DEP
NMORB
DM
EN
ARC
UC
EM2
HIMU
EM1
OIB
REC
PM
3.0 Ga 1.0 2.0 0
3.1Igneous Geochemistry
Arc type
> 3 Ga 1.0 Ga2.5 Ga
Non-Arc
type
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SEISMIC REFLECTION PROFILE EASTERN CANADA
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Magnetotelluric data illustrate Magnetotelluric data illustrate
lithospheric mantle structure: frozen slabs?lithospheric mantle structure: frozen slabs?
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2.7 Deep Seated Geophysics
3.0 Ga 1.0 2.0 0
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3.3
Paired Metamorphic Belts
Collisional Orogens
2.2
3.0 Ga 1.0 2.0 0
3.1Igneous Geochemistry
Large Transcurrent Faults
3.2Accretionary Orogens
3.7
Paleomagnetism3.0
2.7 Deep Seated Geophysics
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• Pi; Pillow Basalts from
the Troodos
Ophiolite , CyprusText
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Blueschist with garnet from the Alps
courtesy of Jane Selverstone
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Ultra-high pressure eclogite (garnet, omphacite, coesite)
courtesy of Mike Brown
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38
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3939
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40
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SUMMARY OF PLATE TECTONIC INDICATORS
3.4 -3.1 Ga
First
Appearances
2.7-2.0 Ga
Widespread
Distribution
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Symmetric Subduction
Steep Subduction
Plate Stacking
Delamination
> 4.5 Ga ?
3.0 - 2.0 Ga
4.5 - 3.0 Ga
eclogite
sinkers
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43
Stagnant
Lid
Episodic
Subduction
Modern
Subduction
I II III
After O’Neill et al 2007
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SUMMARY
• The onset of plate tectonics is not an
event, but an evolving process that
began locally by about 3 Ga.
• Plate tectonics, in some form, probably
existed on planet Earth from the
magma ocean stage onwards.
• Modern subduction became
widespread beginning about 2.7 Ga.
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AND HIGHER LIFE FORMS REQUIRE
CONTINENTS
and
CONTINENTS REQUIRE PLATE
TECTONICS
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IS THERE A RELATIONSHIP
BETWEEN LIFE AND PLATE
TECTONICS?
Life requires water and nutrients
But water and nutrients are
available on planets without plate
tectonics
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The Oldest Fossils occur
In the Marble Bar Chert in
Western Australia at 3.45 Ga
Modern hydrothermal vent
on the seafloor
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HOW CONTINENTS GROW
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JUVENILE
CONTINENTAL
CRUST
2.5 Ga Southern
India
2.7 Ga Zimbabwe
4.0 Ga
Yellowknife
Canada
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