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Lecture 3. Beyond the Plate Tectonics: Plumes, Large Ign. Provinces and Mass Extinctions

Lecture 3. Beyond the Plate Tectonics: Plumes, Large Ign. Provinces and Mass Extinctions. Plumes and LIPs general features Siberian Traps Major open questions Model Relation to mass extinction. Outline. Plates. Hot Spots. Hot Spot Track. Willson, 1963; Morgan, 1971.

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Lecture 3. Beyond the Plate Tectonics: Plumes, Large Ign. Provinces and Mass Extinctions

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  1. Lecture 3. Beyond the Plate Tectonics: Plumes, Large Ign. Provinces and Mass Extinctions

  2. Plumes and LIPs general features • Siberian Traps • Major open questions • Model • Relation to mass extinction Outline

  3. Plates

  4. Hot Spots

  5. Hot Spot Track Willson, 1963; Morgan, 1971

  6. Hot Spot= Mantle Plume- Classical feature beyond plate tectonics Currently, existence of plumes is under debate: anti-plume site– www.mantleplumes.org Main anti-plume argument—no predicted uplift before eruption of Large Igneous Province

  7. Large Igneous Provinces (LIPs) After Saunders et al. (1992)

  8. Large Igneous Provinces (LIPs) After Saunders et al. (1992)

  9. Large Magma Volume • Siberian Flood Basalts- over 4 mln. km3 • Deccan Traps- 2 mln. km3 • North Atlantic Province- over 2-4mln.km3 • Columbia River Province- 0.3 mln. km3 • Plato Onthong-Java-over 40mln. km3

  10. Short Time Scales of Major Magmatic Phases • The most precise dating gives age ranges for the main magmatic phase within method accuracy ±1 mln.y. • The full range of magmatic activity may exceed 10 mln.y.

  11. Ar-Ar age of Siberian Flood Basalts 250±1.1 Ma Reichow et al, 2009

  12. LIPs often predate continental break-up

  13. Continental break-up

  14. Continental break-up

  15. Continental break-up

  16. Continental break-up

  17. LIPS are related to hot spotsDeccan Traps—Reunion HS

  18. Parana-Etendeka—Tristan HS

  19. LIPs source has high temperature Herzberg & Gazel, 2009

  20. LIPs sources are in the Lower Mantle ? Torsvik et al., 2007, 2008

  21. Plumehead model of LIPs Campbell & Griffiths, 1990 Plume An experimental starting plume (in glucose syrup)

  22. Plume head model of LIPs White and McKenzie, 1989; Richards et al.,1989, Campbell and Griffiths, 1990 Uplift of >1 km must be common for LIPs but it is not! Surface uplift = 0.7-1.0 km/100°, i.e. 1.4-3 km for DT= 200-300°

  23. LIPs correlate with mass extinction events Ridgwell, 2005 White and Saunders (2005)

  24. Ocean acidification as a kill mechanism Payne et al, PNAS, 2010

  25. No correlation with LIPs volume Ganino & Arndt, 2009, Svensen et al., 2009

  26. Elegant explanation Ganino & Arndt, 2009, Svensen et al., 2009

  27. Siberian LIP • Over 4 mln. km3 of magmas produced in less than 1 ma • The age of province is about 252ma and coincides with P-T mass extinction • No uplift before magmatism

  28. Reichow et al, 2009 Siberian Traps

  29. Siberian Traps

  30. Questions • Why no pre-magmatic uplift? • Why enormous volume of magmas erupted at thick cratonic lithosphere without extreme extension? • How lithosphere was thinned by >50 km during only few 100 thousand years? • What was the source of large volumes of CO2 and other gases that triggered P-T mass extinction? Heating of coal?

  31. Sobolev et al, Science, 2007

  32. Sobolev et al, Science, 2007

  33. Crustal recycling Hofmann and White, 1980-1982 Kellogg et al., 1999

  34. Eclogite: clinopyroxene ≥garnet ± SiO2 phase 1 см Photo and sample of I. Aschepkov

  35. T C Pyroxenite -Sobolev et al, 2007; peridotite- Walter, 1998 Sobolev, et al, 2005

  36. Pyroxenite-derived melt compared with peridotite-derived melt • High Ni and Si and low Mn/Fe, Ca and Mg: because pyroxene and garnet buffers Ni, Si, Mn, Fe, Ca and Mg instead of olivine (Kelemen et al 1998, Humayun et al, 2004, Sobolev et al, 2005, Herzberg, 2006, Sobolev et al, 2007);

  37. Thermomechanical model of Siberian LIP constrained by petrological data based on 2011 paper

  38. Petrological constraints • Plume potential temperature Tp=1600°C • Eclogite content in plume 10-20wt% (15wt%) • Initial lithospheric thickness >130 km

  39. Melt sources composition

  40. Improvements of tne thermomechanical modeling technique Melting of peridotite (Katz et al, 2003), of eclogite and pyroxenite (based on experiments of Yaxley, and Hirschmann group, Sobolev et al, 2007 Melt transport procedure (fast compaction porous-flow-like in the melting region and intrusion in the lithosphere)

  41. Model setup

  42. Thermal plume(Tp=1650°C)no melting 0 Myr

  43. Thermal plume no melting 0.25 Myr

  44. Thermal plume no melting 0.5 Myr

  45. Thermo-chemical plume(Tp=1650°C,18% eclogite) no melting 0 Myr

  46. Thermo-chemical plume no melting 0.5 Myr

  47. Thermo-chemical plume no melting 1.5 Myr

  48. Thermal plume 0.5 Myr Thermo-chemicalplume

  49. Elevation

  50. Temperature

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