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An overview of smectite clays

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  1. 1. Smectites Heather Jordan GEOSC 440 03/17/2005
  2. 2. What are smectites? <ul><li>Single octahedral sheet between 2 tetrahedral sheets </li></ul><ul><ul><li>2:1 Phyllosilicates: </li></ul></ul><ul><ul><ul><li>Smectite </li></ul></ul></ul><ul><ul><ul><li>Vermiculite </li></ul></ul></ul><ul><ul><ul><li>Illite </li></ul></ul></ul>
  3. 3. What are smectites? <ul><li>Layer charge from substitutions: </li></ul><ul><ul><li>Octahedral: Mg 2+ , Fe 2+ , Mn 2+ or Al 3+ </li></ul></ul><ul><ul><li>Tetrahedral: Al 3+ or Fe 3+ for Si 4+ </li></ul></ul><ul><li>Interlayer expands (up to 30% by volume); “swelling clays” </li></ul><ul><ul><li>Separation depends on interlayer cations present & ionic strength of solution </li></ul></ul>
  4. 4. What are smectites? <ul><li>Platelet Dimensions </li></ul><ul><ul><li>200-500 nm in diameter </li></ul></ul><ul><ul><li>0.93 nm thick </li></ul></ul><ul><li>General Formula: </li></ul><ul><ul><li>A 0.3 D 2-3 [T 4 O 10 ]Z 2 •nH 2 O </li></ul></ul><ul><li>2:1  1:1 </li></ul><ul><ul><li>Ratio of tetrahedral: octahedral sheets </li></ul></ul><ul><ul><li>Weathering </li></ul></ul>
  5. 5. Smectite Group Members <ul><li>Allettite: Ca 0.2 Mg 6 (Si,Al) 8 O 20 (OH) 4 • 4H 2 O </li></ul><ul><li>Beldellite: (Na,Ca 0.5 ) 0.3 Al 2 (Si,Al) 4 O 10 (OH) 2 •nH 2 O </li></ul><ul><li>Hectorite: Na 0.3 (Mg,Li) 3 Si 4 O 10 (F,OH) 2 </li></ul><ul><li>Montmorillonite: (Na,Ca) 0.33 (Al,Mg) 2 Si 4 O 10 (OH) 2 •nH 2 O </li></ul><ul><li>Nontronite: Na 0.3 Fe 2 (Si,Al) 4 O 10 (OH) 2 •nH 2 O </li></ul><ul><li>Saponite: Ca 0.25 (Mg,Fe) 3 (Si,Al) 4 O 10 (OH) 2 •nH 2 O </li></ul><ul><li>Sauconite: Na 0.3 Zn 3 (Si,Al) 4 O 10 (OH) 2 •4H 2 O </li></ul><ul><li>Stevensite: (Ca,Na) x Mg 3 Si 4 O 10 (OH) 2 </li></ul><ul><li>Swinefordite: Li(Al,Li,Mg) 4 (Si,Al) 8 O 20 ,(OH,F)4 •xH 2 O </li></ul><ul><li>Volkonskoite: Ca 0.3 (Cr,Mg,Fe) 2 (Si,Al) 4 O 10 (OH) 2 •4H 2 O </li></ul><ul><li>Yakhontovite: (Ca,Na) 0.5 (Cu,Fe,Mg) 2 Si 4 O 10 (OH) 2 •3H 2 O </li></ul><ul><li>Zincsilite: </li></ul><ul><li>Zn 3 Si 4 O 10 (OH) 2 •4H 2 O </li></ul>
  6. 6. Thixotrophy <ul><li>Ability to form stiff gels at low concentrations that change viscosity as shear application changes </li></ul><ul><ul><li>No Shear: Double layers repelled & + surface attracted to - edge  “house of cards” configuration </li></ul></ul><ul><ul><li>Shear: Aligns clay particles & ↓ viscosity </li></ul></ul>
  7. 7. Smectite-Illite (S-I) Transition <ul><li>Temperature, Pressure & Time </li></ul><ul><li>Abiotic Reaction: </li></ul><ul><ul><li>300-450 o C </li></ul></ul><ul><ul><li>100 MPa </li></ul></ul><ul><ul><li>4-5 Months </li></ul></ul><ul><li>Biological Reaction: </li></ul><ul><ul><li>Metal-Reducing Bacteria </li></ul></ul><ul><ul><li>Room Temperature </li></ul></ul><ul><ul><li>1 atm </li></ul></ul><ul><ul><li>2 weeks </li></ul></ul>
  8. 8. Structural Comparison: Smectite to Illite
  9. 9. On the mechanical role of smectite in subduction zones Peter Vrolijk Department of Geological Sciences, University of Michigan
  10. 10. What is a decollement? <ul><li>“ A shallow dipping to subhorizontal fault or shear zone” </li></ul><ul><li>French: “Ungluing” </li></ul><ul><li>The detachment of the upper cover from its substratum </li></ul><ul><li>Also known as: </li></ul><ul><ul><li>- Detachment fault </li></ul></ul><ul><ul><li>- Decollement Fault </li></ul></ul><ul><ul><li>- Sole Fault </li></ul></ul>(Image modified from Demian’s lecture sketch)
  11. 11. Objective of the Study <ul><li>Find out if subduction zone decollements occur in smectite-rich horizons </li></ul><ul><li>Review previous research : </li></ul><ul><ul><li>Rock Deformation </li></ul></ul><ul><ul><li>Physical Properties of Sediments </li></ul></ul><ul><ul><li>Smectite-Illite (S-I) Transition </li></ul></ul><ul><li>How these effect seismicity in subduction zones </li></ul>
  12. 12. Why is this research relevant? <ul><li>The characteristics of sediments at subduction zones could tell us where decollements form </li></ul><ul><li>By understanding what happens at decollements we learn more about the S-I transition </li></ul><ul><li>Aspects of the S-I transition process at decollements tells us something about seismicity </li></ul>
  13. 13. Previous Research: Subduction Zones <ul><li>Sediment-Rich: </li></ul><ul><ul><li>Long decollements </li></ul></ul><ul><ul><li>Smectite-rich sediments </li></ul></ul><ul><li>Decollements: </li></ul><ul><ul><li>Formation is associated with prism structure </li></ul></ul><ul><ul><li>↑ Fluid pressure  ↓ friction  ↓ tapering </li></ul></ul><ul><ul><li>↑ ploughing up of prism  ↓stress & zones of ↑ porosity </li></ul></ul>(Image modified from Demian’s lecture sketch)
  14. 14. Previous Research: Subduction Zones <ul><li>Pelagic Sediments: subducted </li></ul><ul><li>Terrigenous Deposits: accrete at prism base </li></ul><ul><li>Changes in mechanical properties result in peeling of terrigenous from pelagic </li></ul><ul><li>Decollement is just beneath area of partition at base of smectite-rich zone </li></ul>(Image modified from Demian’s lecture sketch)
  15. 15. Methods: Data Collection <ul><li>Sediments from an active decollement have only been collected once </li></ul><ul><li>Seismic reflection data  mineralogical composition of sediments </li></ul><ul><li>Decollement geometry from drill cores </li></ul>(Image taken from Demian’s Lecture Presentation)
  16. 20. Results <ul><li>Not enough data </li></ul><ul><ul><li>Smectites & decollement formation </li></ul></ul><ul><ul><li>More drilling needed </li></ul></ul><ul><li>2 Regions with the most data: </li></ul><ul><ul><li>Decollements occur in smectite-rich zones </li></ul></ul>(Image taken from Demian’s Lecture Presentation)
  17. 21. Implications: For Decollement Generation <ul><li>Mineralogical Reasons why smectite is weakest sediment in subduction zones </li></ul><ul><ul><li>Recall smectite structure </li></ul></ul><ul><ul><li>Water = weakness (H-bonds) </li></ul></ul><ul><ul><li>Relative Deformation Stresses </li></ul></ul><ul><ul><li>Water tightly adsorbed to smectite </li></ul></ul><ul><ul><ul><li>Remains during deformation (↑ porosity) </li></ul></ul></ul>
  18. 22. What dictates smectite distribution in ocean sediments? <ul><li>Transformation from volcanic ash </li></ul><ul><ul><li>Abundant ash </li></ul></ul><ul><ul><li>Sufficient time & pressure </li></ul></ul><ul><ul><li>Between pelagic & hemipelagic sediments (due to dilution & age) </li></ul></ul><ul><li>Detrital clay influx </li></ul>
  19. 23. Sediment Minerology Evolution: S-I Transition <ul><li>Metamorphic transitions on subducting plate </li></ul><ul><li>80% complete 100-110 o C </li></ul><ul><li>↑ Rate of subduction; ↓ S-I transition rate </li></ul><ul><li>Subduction Observations: </li></ul><ul><ul><li>Japan Trench (fast) </li></ul></ul><ul><ul><li>Barbados (slow) </li></ul></ul>
  20. 24. Implications: For Subduction Zones <ul><li>S-I: Sediment Strengthening </li></ul><ul><li>How it relates to seismicity </li></ul>
  21. 25. Does this lead to development of the seismic front? <ul><li>During S-I, ↓ smectite (as it is converted to illite) </li></ul><ul><li>Decollement strengthened </li></ul><ul><li>Friction ↑ </li></ul><ul><li>Deformation & strain on overriding plate </li></ul><ul><li>Seismicity results </li></ul>
  22. 26. Conclusions <ul><li>Decollements form in smectite-rich sediments </li></ul><ul><li>More drilling needed at prisms </li></ul><ul><li>Columb Wedge Theory: coefficient of basal sliding friction may need modification </li></ul><ul><li>Seismicity related to strengthening (due to S-I) </li></ul>
  23. 27. Comments & Criticisms: Where to Begin? <ul><li>Overgeneralization from too small a sample size </li></ul><ul><li>Too little is known about the lithology to draw conclusions about the relationship of smectite to decollement formation </li></ul><ul><li>Keeping physical models in mind (structure, hydration, the effect of shear, S-I, etc.), Is the model logical? </li></ul><ul><ul><li>Shear reduces viscosity (house of cards to plates) </li></ul></ul><ul><ul><li>S-I (squeezes out water; no more H-bonds to break) </li></ul></ul><ul><ul><li>Leads to strengthening  Seismicity </li></ul></ul><ul><li>Would I have published this? NO!!! </li></ul>
  24. 28. ??QuESTIONS??
  25. 29. For more thoroughly exhilarating reading on smectites: <ul><li>Alba, M.D, et al. (2001) Hydrothermal reactivity of Lu-saturated smectites: Part I. A long-range order study. American Minerologist . 86: 115-123. </li></ul><ul><li>Alba, M.D., et al. (2001) Hydrothermal reactivity of Lu-saturated smectites: Part II. A short-range order study. American Minerologist . 86: 124-131 </li></ul><ul><li>Blum, A.E., Eberl. D.D. & Rutherford, D.W. Quatitative Determination of Smectite Surface Areas by the sorption of polyvinylpyrrolidone. Ninth Annual V.M. Goldschmidt Conference . 7567.pdf </li></ul><ul><li>Cervini-Silva, J., et al. (2001) Transformation of Chlorinated Aliphatic Compounds by Ferruginous Smectite. Environmental Science and Technology. 35: 805-809. </li></ul><ul><li>Ghosh, A & McSween Jr., H.Y. Normative Minerology and Possible Origin of Mars Pathfinder Soils. Online. </li></ul><ul><li>Guangyao, H.L., et al. (2003) Sorption and Desorption of Pesticides by Clay Minerals and Humic Acid- Clay Complexes. Soil Science Society Americal Journal. 67: 122-131. </li></ul><ul><li>Johnston, C.T. et al. Spectroscopic Study of Nitroaromatic—Smectite Sorption Mechanisms. Environmental Science & Technology . American Chemical Society. </li></ul><ul><li>Kasama, T., et al. (2001) Experimental mixtures of smectite and rectorite: Re-investigation of “fundamental particles” and “interparticle diffraction”. American Minerologist. 86: 105-114. </li></ul><ul><li>Parry, W.T., Jasumback, M. & Wilson, P.M. (2002) Clay Minerology of Phyllic and Intermediate Agrillic Alteration at Bingham, Utah. Economic Geology . 97: 221-239. </li></ul><ul><li>Stixrude, L & Peacor, D.R. (2002) First-principles study of illite-smectite and implications for clay-mineral systems. Nature. 420: 165-168. </li></ul><ul><li>Trentstesaux, A., et al. (2003) Data Report: Pleistocene Paleoclimatic Cyclivity of Southern China: Clay Mineral Evidence Recorded in the South China Sea (ODP Site 1146). Proceedings of the Ocean Drilling Program, Scientific Results. 184: 1-10. </li></ul><ul><li>Vrolijk, P. & van der Pluijm, B.A. (1999) Clay Gouge. Journal of Structural Geology . 21: 1039-1048. </li></ul>
  26. 30. For more thoroughly exhilarating reading on smectites: <ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul>