Structure and Thermochronology of the Verkhoyansk Fold

Apatite Fission-Track
Thermochronology of the Southern
Verkhoyansk Fold and Thrust Belt,
Russia
J. Toro (WVU)
Text associated
with each slide is
in this
presentation was
inserted as
comments
A. Prokopiev (RAS)
J. Colgan (Stanford)
T. Dumitru (Stanford)
E. L. Miller (Stanford)
J. Hourigan (Yale)
Sponsored by Exxon-Mobil
Objectives
• Structural Style
– Along strike variations
• Timing of Deformation
• Thermal History
• Denudation History
• Tectonic History
Data Collected
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Structural and stratigraphic data
Apatite Fission Track Data
Vitrinite Reflectance
Conodont Alteration Indices
40Ar/39Ar data
U-Pb data of granites and gneisses
Tectonic Evolution for the South
Verkhoyansk
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Late Proterozoic rifting
Early Paleozoic passive margin
Late Devonian rifting
Mississippian to Early Jurassic passive
margin
• Late Jurassic (?) collision with Okhotsk
block
• Cretaceous fold-and-thrust-belt
• Tertiary strike-slip (?) faulting
The Verkhoyansk
Fold and Thrust
Belt
After Parfenov et al, 1994
South
Verkhoyansk
South Verkhoyansk CrossSection
South Verkhoyansk Stratigraphy
Frontal thrusts from the foreland
Third thrust sheet
Second thrust
First thrust
Spaced cleavage in Cambrian
platform carbonates- Frontal zone
West-vergent folds in frontal
thrust sheets
W
E
Permo-Carboniferous Slates
Tarbagganakh Batholith
120 Ma Granodiorite
Andrei Prokopiev
Boudinaged Granite Dike
40Ar/39Ar
constrains on
deformation in the Allakh Yun’
zone
Weighted Mean =151 ± 0.7 Ma
South Verkhoyansk
Thermal Data
Apatite
Fission Track
Ages
Apatite Fission Track Ages
Cooling Histories
Burkhala
Fault
Where are the sediments denuded from the South
Verkhoyansk?
Conclusions 1
• Over all structure:
– Inverted Paleozoic-E. Mesozoic passive
margin sedimentary wedge
– Moderate shortening
– Penetrative deformation in hinterland
– No foreland basin
• Allakh-Yun’ metamorphic belt:
– Low greenschist grade
– Back-thrusted fan
– Higher grade areas linked to 120 Ma plutons
Conclusions 2
• Timing
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Collision starting as early as 150 Ma
Intrusion of granites at 120 Ma
Ongoing ductile deformation in Allakh-Yun
Late Cretaceous denudation
A hint of an Eocene pulse of denudation
End