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Paleomagnetic timing of Mesozoic Mongol-Okhotsk Ocean closure by J.P. Cogné 1, D. Gapais 2, Y. Daoudene 2 and V.A. Kravchinsky 3 1 Université Paris Diderot,

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Presentation on theme: "Paleomagnetic timing of Mesozoic Mongol-Okhotsk Ocean closure by J.P. Cogné 1, D. Gapais 2, Y. Daoudene 2 and V.A. Kravchinsky 3 1 Université Paris Diderot,"— Presentation transcript:

1 Paleomagnetic timing of Mesozoic Mongol-Okhotsk Ocean closure by J.P. Cogné 1, D. Gapais 2, Y. Daoudene 2 and V.A. Kravchinsky 3 1 Université Paris Diderot, IPGP, UMR CNRS 7154, Paris Cedex 05, France 2 Université de Rennes 1, Géosciences Rennes, UMR CNRS 6118, Rennes Cedex, France 3 University of Alberta, Edmonton, AB, T6G2J1, Canada EGU General Assembly 2012 – Vienna, Austria, April 22-27, 2012

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3 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 from Amuria (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)....

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5 8 Permo-Carboniferous (C 2 -P 2 ) poles 9 Jurassic (J 2-3 ) poles 13 Early Cretaceous (K 1 ) poles

6 1. Late Paleozoic (data)

7 1. Late Paleozoic (data)

8 1. Late Paleozoic (palaeolatitudes)

9 1. Late Paleozoic (data)

10 1. Late Paleozoic (data)

11 1. Late Paleozoic (palaeolatitudes)

12 1. Late Paleozoic (palaeolatitudes)

13 1. Late Paleozoic (palaeolatitudes)

14 1. Late Paleozoic (rotations - 1)

15 1. Late Paleozoic (rotations - 1)

16 1. Late Paleozoic (rotations - 1)

17 local tectonic rotations due to early Cretaceous MO closure and/or Cenozoic India collision..? 1. Late Paleozoic (rotations - 2)

18 2. Middle-Late Jurassic (data)

19 2. Middle-Late Jurassic (data)

20 2. Middle-Late Jurassic (average Siberian poles) allowing some poles to rotate about their site location

21 2. Middle-Late Jurassic (data)

22 2. Middle-Late Jurassic (average Mongolian poles) allowing some poles to rotate about their site location

23 2. Middle-Late Jurassic (Palaeolatitudes)

24 2. Middle-Late Jurassic (Palaeolatitudes)

25 2. Middle-Late Jurassic (rotations)

26 2. Middle-Late Jurassic (rotations)

27 3. Early Cretaceous (data)

28 3. Early Cretaceous (data)

29 3. Early Cretaceous (palaeolatitudes)

30 3. Early Cretaceous (data)

31 3. Early Cretaceous (palaeolatitudes)

32 3. Early Cretaceous (palaeolatitudes)

33 3. Early Cretaceous (mean paleopoles) allowing some poles to rotate about their site location

34 3. Early Cretaceous (mean paleopoles) allowing some poles to rotate about their site location

35 3. Early Cretaceous (mean paleopoles)

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

37 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}

38 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...

39 ? ? 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 ?...

40 Permo-Carboniferous Middle-Late Jurassic Early Cretaceous 5. Evaluation of closure velocity

41 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 data from both sides of the suture...

42 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

43 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 closure. 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:

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