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Geol 2312 Igneous and Metamorphic Petrology

Geol 2312 Igneous and Metamorphic Petrology. Lecture 14 Continental Flood Basalts with special emphasis on the Midcontinent Rift. February 25, 2009. Large Igneous Provinces Impact sites of Starting Mantle Plumes. http://www.largeigneousprovinces.org.

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Geol 2312 Igneous and Metamorphic Petrology

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  1. Geol 2312 Igneous and Metamorphic Petrology Lecture 14 Continental Flood Basalts with special emphasis on the Midcontinent Rift February 25, 2009

  2. Large Igneous ProvincesImpact sites of Starting Mantle Plumes http://www.largeigneousprovinces.org

  3. Continental Flood BasaltsLarge Igneous Provinces in Continental Settings Winter (2001) Figure 15-1. Columbia River Basalts at Hat Point, Snake River area. Cover of Geol. Soc. Amer Special Paper 239. Photo courtesy Steve Reidel.

  4. Mafic Dike SwarmsVestiges of Ancient Continental Flood Basalts

  5. The Break-up of GondwanalandParana/Karoo/Ferrar/Deccan Ferrar

  6. Columbia River Basalts, Snake River Plain Basalts and the Yellowstone Plume

  7. The Midcontinent Rift An Aborted, Mantle Plume-influenced, Intracontinental Rift (1110-1086 Ma)

  8. Rifting and Plume-influenced Magmatism Main Evolutionary Stages of the Midcontinent Rift 1,115-1,086 Ma Subsidence and Sedimentation 1,090-1,080Ma Compression and Rift Inversion 1,080-1,040 Ma

  9. Evidence for a Starting Mantle Plume • Large Volume of Volcanic Fill (>1,500,000 km3; Cannon, 1992) • Extensive Intrusive Underplating (gravity modelling) • Potential Temperature of Source ~250oC > Normal Mantle (Hutchinson et al., 1990) • Isotope Geochemistry Indicative of Enriched Mantle Source (Nicholson & Shirey, 1997) • Evidence of Thermal Doming (subaerial basalts, early volcanic-less intrusions) • Rapid Rates of Effusion (avg. ~0.15 km3/y; Cannon, 1992, Davis and Paces, 1990) • Radial Orientation of Dike Swarms in the Lake Superior Region (Green et al., 1987) • Migration of Magmatism from East to West (eastward plate drift over fixed plume?) Inconsistencies with a Mantle Plume • Prolonged magmatism (>23 Ma) • Peak of volcanic activity at midpoint of magmatic interval? Lutgens and Tarbuck, 2003

  10. Role of the Grenville Rivers, 2008 (Fig. 3) Midcontinent Rift Inversion ~1080-1040 Ma* Midcontinent Rift Magmatism 1115-1086 Ma Rivers, 2008 (Fig. 1) *Cannon, 1994

  11. Exposed Geology of the Midcontinent Rift in the Lake Superior Region R

  12. Geochronology of the Midcontinent Rift Late ? Magmatic Stages Miller and Vervoort (1996), Nicholson et al. (1997) Main - ? Latent Early Uplift? Compilation by Green (2005)

  13. Chemostratigraphic data mostly from Green (1986), Klewin & Berg (1991), Lightfoot et al. (1991), Shirey et al. (1994), Nicholson et al.(1997), Vervoort & Green (1997).

  14. Evidence for Crustal Underplating Halls (1982)

  15. GLIMPCE Line A Modified from Thomas & Teskey (1994), Fig. 14; Includes interpretations of Trehu et al., (1991)

  16. Origin of Felsic Magmas Partial Melting of the Lower Crust

  17. Origin of Anorthositic Rocks Plagioclase Flotation in the Lower Crust Based on Kushiro (1980)

  18. From Miller & Vervoort (1996)

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