Origin of the Main Granitoid Belt of Northeastern Russia: New U-Pb Geochronology and GeochemistryJ. Toro, West Virginia University, USAA.V. Prokopiev, RAS, Yakutsk, RussiaE.L. Miller, Stanford University, USAV.A. Trunilina, RAS, Yakutsk, RussiaA.G. Bakharev, RAS, Yakutsk, Russia

Cretaceous(?) Granites of NE Russia

Yakutsk

Magadan

Arctic Ocean

Okhotsk Sea

Northern Belt

Main Belt

Tas-KystabytBelt

Verkhoyansk Thrust beltNorth Asia Craton(Siberia)

Kolyma-Omolonsuperterrane

Okhotsk- Chukotsk

Volcanic

Belt

PacificOcean

Terrain Map after Nokleberg et al. 2001

Aeromagnetics and Granites

Verkhoyansk

South Anyui Suture

Scotese, Nokleberg et al. 2001

Scotese, Nokleberg et al. 2001

130-123 Ma

143-138 Ma

Tectonic Evolution

Parfenov, 1991

Siberia Kolyma Omolon Microcontinent

Oimyakon OceanLate Jurassic (Oxf.-Kimm.)

Late Jurassic (Tithonian)

Early Cretaceous

161-151 Ma

151-145 Ma

145-100 Ma

Cross section across Verkhoyansk - Kolyma orogen

(after Prokopiev, 1998)

Trace Element CharacteristicsYakutian and Andean Granitoids

1.00

10.00

100.00

1000.00

1.00 10.00 100.00 1000.00

Y+Nb (ppm)

Rb

(ppm

)

Main Belt Northern Belt Tas-Kystabyt Andean Granitoids

CollisionWithin Plate

OrogenicVolcanic Arc

Granitoid tectonic discrimination diagram (Pearce et al. 1984)

U-Pb Zircon Geochronology• 10 Main Belt Plutons• 4 Northern Belt Plutons• 5 Tas Kystabyt Granites and Sub-volcanics• 2 Uyandina-Yasachnida Volcanics

• USGS/STANFORD SHRIMP-RG• At least 10 zircons per sample• Rims and cores

Chersky Range Granites

Yakutsk

Magadan

Arctic Ocean

Okhotsk Sea

Main Belt Granites-Chersky Range

100 km

Chibagalakh

Porozhnotsepinsky

Pravo-Tuostakh

Nelkan

ChugulukUst Nera

Khayargastakh

Chimalga

Pravo Kharaulakh

Ar/Ar=131-143

Ar/Ar=143

Ar/Ar=144

Main Belt- Chibagalakh 238U/206Pb Ages

200 microns

147±1.6155±1.8

151±1.4154±1.7

238

Main Belt Granites-Chersky Range

100 km

Chibagalakh

Porozhnotsepinsky

Pravo-Tuostakh

Nelkan

ChugulukUst Nera

Khayargastakh

Chimalga

Pravo Kharaulakh

145-155 Ma

148-154 Ma

151 Ma

147-156 Ma

154±1.2 Ma

155±1.4 Ma

148±1 Ma, 2 Ga cores

84±1 Ma

Tas-Kystabyt Belt-Trud Granite

155-138 Ma

Conclusions

• Magmatism in the Main Belt 155-145 Ma• Main Belt Granitoids are coeval with

Uyandina-Yasachnida Arc• Main Belt is probably subduction related, not

collisional• Subduction under Verkhoyansk Margin during

Late Jurassic(?)→ Tas-Kystabyt• Northern Belt is 126-136 Ma

Geological map of the Verkhoyansk-Kolyma orogen