Paleomagnetic timing of Mesozoic Paleomagnetic timing of Mesozoic Mongol-Okhotsk Ocean closureMongol-Okhotsk Ocean closure

by

J.P. Cogné1, D. Gapais2, Y. Daoudene2 and V.A. Kravchinsky3

1Université Paris Diderot, IPGP, UMR CNRS 7154, 75238 Paris Cedex 05, France2Université de Rennes 1, Géosciences Rennes, UMR CNRS 6118, 35042 Rennes Cedex, France3University of Alberta, Edmonton, AB, T6G2J1, Canada

EGU General Assembly 2012 – Vienna, Austria, April 22-27, 2012

Geological background:

- Occurrence of hyperbasites, ophiolites, intrusions of gabbro-tonalites and plagiogranites comparable with island-arc granitoïds...

remains of a Paleozoic ocean separating Siberia in the north fromAmuria (or Mongolia) in the south.

- Younging ages of felsic intrusives all along the suture, from late Carboniferous in the west, to early Cretaceous in the east..

suggests a progressive, scissor-like, closure of this ocean...

Mongol-Okhotsk

foldbelt

Zonenshain et al. (1976, 1990), Kuzmin & Filipova (1979), Parfenov (1984), Sorokin (1992)....

8 Permo-Carboniferous (C2-P2) poles9 Jurassic (J2-3) poles

13 Early Cretaceous (K1) poles

1. Late Paleozoic(data)

1. Late Paleozoic1. Late Paleozoic(data)

1. Late Paleozoic(palaeolatitudes)

1. Late Paleozoic(data)

1. Late Paleozoic1. Late Paleozoic(data)

1. Late Paleozoic(palaeolatitudes)

1. Late Paleozoic(palaeolatitudes)

1. Late Paleozoic(palaeolatitudes)

1. Late Paleozoic(rotations - 1)

1. Late Paleozoic(rotations - 1)

1. Late Paleozoic(rotations - 1)

local tectonic rotations due to early Cretaceous MO closure and/or Cenozoic India collision..?

1. Late Paleozoic(rotations - 2)

2. Middle-Late Jurassic(data)

2. Middle-Late Jurassic(data)

2. Middle-Late Jurassic(average Siberian poles)

allowing some poles to rotate about their site location

2. Middle-Late Jurassic(data)

2. Middle-Late Jurassic(average Mongolian poles)

allowing some poles to rotate about their site location

2. Middle-Late Jurassic(Palaeolatitudes)

2. Middle-Late Jurassic(Palaeolatitudes)

2. Middle-Late Jurassic(rotations)

2. Middle-Late Jurassic(rotations)

3. Early Cretaceous(data)

3. Early Cretaceous(data)

3. Early Cretaceous(palaeolatitudes)

3. Early Cretaceous(data)

3. Early Cretaceous(palaeolatitudes)

3. Early Cretaceous(palaeolatitudes)

3. Early Cretaceous(mean paleopoles)

allowing some poles to rotate about their site location

3. Early Cretaceous(mean paleopoles)

allowing some poles to rotate about their site location

3. Early Cretaceous(mean paleopoles)

4. Age of MO ocean closure: Latitude evolution of a reference point currently located on the Mongol-Okhotsk suture

after paleopoles from:

North of the suture – (Siberia)

South of the suture – (Amuria)

4. Age of MO ocean closure: Latitude evolution of a reference point currently located on the Mongol-Okhotsk suture at {51°N, 112°E}

4. Age of MO ocean closure: Latitude evolution of a reference point currently located on the Mongol-Okhotsk suture at {51°N, 112°E}

after paleopoles from:

North of the suture – (Siberia)

South of the suture – (Amuria)

and APWP's for:

Eurasia (Besse & Courtillot, 2002)

NCB (Gilder & Courtillot, 1997)

Not before 150 Ma...

??

4. Age of MO ocean closure: Latitude evolution of a reference point currently located on the Mongol-Okhotsk suture at {51°N, 112°E}

after paleopoles from:

North of the suture – (Siberia)

South of the suture – (Amuria)

and APWP's for:

Eurasia (Besse & Courtillot, 2002)

NCB (Gilder & Courtillot, 1997)

... rather at ~130 Ma... at ~130 Ma or somewhat later ?...

Permo-Carboniferous

Middle-Late Jurassic

Early Cretaceous

5. Evaluation of closure velocity

5. Evaluation of closure velocity: Latitude evolution of a reference point currently located on the Mongol-Okhotsk suture at {51°N, 112°E}

based on actual paleomagnetic datafrom both sides of the suture...

5. Evaluation of closure velocity: Latitude evolution of a reference point currently located on the Mongol-Okhotsk suture at {51°N, 112°E}

40 to 75 myrs

33° to 48°

a 33° to 48° latitudinal convergence in 40 to 75 myrs

implies a relative velocity of:

4.9 to 13.3 cm/yr

or

= 9.1 ± 4.2 cm/yr

EGU General Assembly 2012 – Vienna, Austria, April 22-27, 2012

Conclusions:

1. A wide ocean separated Siberia craton from Asian terranes in the Mesozoic.

2. This ocean was as large as more than 5000 km in latitude in the late Permian, and more than 3000 km in the middle-late Jurassic, at a present-day longitude of ~110° E.

3. Closure of this ocean took place in a scissor-like manner, beginning at the permo-triassic boundary, and was achieved no later (but not earlier, as well..!) than 130 to 110 Ma, by the beginning of the Cretaceous.

4. This history indeed casts some questions about its relationships to ~N/S crustal extension in Mongolia and North China, which begins as early as ~130 Ma.... (see next talks..!).

Paleomagnetic timing of Mesozoic Mongol-Okhotsk Ocean closurePaleomagnetic timing of Mesozoic Mongol-Okhotsk Ocean closure ..J.P. Cogné, D. Gapais, Y. Daoudene and V.A. Kravchinsky.J.P. Cogné, D. Gapais, Y. Daoudene and V.A. Kravchinsky.

Paleomagnetic poles obtained from both sides of the Mongol-Okhotsk geosuture unambiguously reveal that: