Transcript Origin of the Main Granitoid Belt of Northeastern Russia

Origin of the Main Granitoid Belt
of Northeastern Russia: New UPb Geochronology and
Geochemistry
J. Toro, West Virginia University, USA
A.V. Prokopiev, RAS, Yakutsk, Russia
E.L. Miller, Stanford University, USA
V.A. Trunilina, RAS, Yakutsk, Russia
A.G. Bakharev, RAS, Yakutsk, Russia
Cretaceous(?) Granites of NE Russia
Arctic Ocean
Northern Belt
Main Belt
Yakutsk
Tas-Kystabyt
Belt
Magadan
Okhotsk Sea
Kolyma-Omolon
superterrane
North Asia
Craton
(Siberia)
Okhotsk-
Pacific
Ocean
Terrain Map after Nokleberg et al. 2001
Aeromagnetics and Granites
Scotese, Nokleberg et al. 2001
143-138 Ma
130-123 Ma
Scotese, Nokleberg et al. 2001
Tectonic Evolution
161-151 Ma
Siberia
151-145 Ma
Oimyakon Ocean
Late Jurassic (Oxf.-Kimm.)
Kolyma Omolon Microcontinent
Late Jurassic (Tithonian)
Early Cretaceous
145-100 Ma
Parfenov, 1991
Cross section across Verkhoyansk - Kolyma orogen
(after Prokopiev, 1998)
Trace Element Characteristics
Yakutian and Andean Granitoids
1000.00
Collision
Within
Plate
Rb (ppm)
100.00
10.00
Volcanic
Arc
1.00
1.00
Orogenic
100.00
10.00
1000.00
Y+Nb (ppm)
Main Belt
Northern Belt
Tas-Kystabyt
Andean Granitoids
Granitoid tectonic discrimination
diagram (Pearce et al. 1984)
U-Pb Zircon Geochronology
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•
•
•
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
Arctic Ocean
Yakutsk
Magadan
Okhotsk Sea
Main Belt Granites-Chersky Range
Pravo-Tuostakh
Chibagalakh
Chimalga
Ar/Ar=131-143
Porozhnotsepinsky
Ar/Ar=143
Khayargastakh
Pravo Kharaulakh
Chuguluk
Ust Nera
Nelkan
Ar/Ar=144
100 km
Main Belt- Chibagalakh
238U/206Pb Ages
151±1.4
154±1.7
147±1.6
155±1.8
200 microns
238
Main Belt Granites-Chersky Range
Pravo-Tuostakh
148-154 Ma
Chibagalakh
Chimalga
145-155 Ma
Porozhnotsepinsky
155±1.4 Ma
Khayargastakh
147-156 Ma
Pravo Kharaulakh
154±1.2 Ma
Chuguluk
Ust Nera
151 Ma
84±1 Ma
Nelkan
148±1 Ma, 2 Ga cores
100 km
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