1 / 25

What is a plume? By Julian Winter

What is a plume? By Julian Winter. Alexandra Witze (2003). Introduction. Aims Primarily to confuse you; see conclusion Briefly look at modeling Understand their characteristics & evolution Conclusion; confused?. Birth of Plumes - Morgan 1971.

ahmed-haney
Download Presentation

What is a plume? By Julian Winter

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. What is a plume?By Julian Winter Alexandra Witze (2003)

  2. Introduction Aims • Primarily to confuse you; see conclusion • Briefly look at modeling • Understand their characteristics & evolution • Conclusion; confused?

  3. Birth of Plumes -Morgan 1971 • Intra plate volcanism – failure of plate tectonics • Fixedupward rise of hot, buoyant mantle • Comes from the deep mantle • Downward flow dispersed uniformly • Column shape inferred from swell

  4. Radiating Dykes • Centrally located source • Outward injection of magma • Plume provides point source • Found on Venus – no tectonics here • But not all intraplate volcanism has such dykes! Richard E. Ernst 2004

  5. Plume Modelling- Whitehead & Luther 1975 • Liquids heated from below - TBL • TBL less dense & less viscous • Head and tail structure & entrainment Griffiths & Campbell 1990

  6. Plumes Refined: Flood basalts -Campbell & Griffiths 1990 • A plumes head can:- • Produce 500m-1000m uplift but later subsidence • Spread > 2000-2500km • Melt – Flood basalts • Evolution to plume tail melts • But wait, flood basalts not found at all hotspots e.g. Hawaii!!!

  7. Geochemistry • Typically have enrichment in incompatible elements • Higher concentrations of He3 (high RA) • Typically HIMU, EM-1 & 2 & FOZO • Isotopic ratio distinguished from DM

  8. Angelo Peccerillo

  9. Subduction derived plumes 1. • Suducted slabs drive convection • Slabs reheated in lower mantle; bouyant • Accounts for geochemistry

  10. Subduction derived plumes 2. • Slab sinks to a 1600km deep TBL • Slab creates high spot  Plume • Interface of TBL irregular • Depth of plume can therefore be irregular thus plume can be both deep & shallow?

  11. Subduction derived plumes 2. Kellogg et al 1999

  12. Supersrwells e.g. Polynesia • Anomalously shallow seafloor several 1000km in extent • Unusually dense concentrations of hotspots • SUPERPLUMES • Doming of Superplume  Plumes

  13. Davaille (1999) Superswells

  14. Plumes: a summary • Plumes from CMB • Shallower origins & subduction driven • Superswells & Superplumes • ‘Top down’ models & shallow plumes • Function of plate related stresses • Shallow mantle upwelling

  15. Conclusion Jules’ criteria for plume recognition: • LIP but no worries if not. • Monotic age progression; if it suits you. • A DEEP source but a shallow source will do. • A superswell e.g. Polynesia & Africa- they’re just showing off. • Low seismic velocity? not if you don’t want. • Dare I say ‘radial dykes’?

  16. Morgan 1971 Griffiths & Campbell 1990 Kellogg 1999 Ivanov 2004 Daville (1999) Anderson, Foulger 2004 So a plume is…….?

  17. Questions?

  18. Condie 2003

  19. The plate tectonic paradigm • Intra plate volcanism – failure of plate tectonics • Hotspots • Linear tracks • age progression • Fixed position • Why a hot mantle? Unrealistic!

More Related