Smectites

Heather JordanGEOSC 44003/17/2005

What are smectites?Single octahedral sheet between 2 tetrahedral sheets2:1 Phyllosilicates:SmectiteVermiculiteIllite

What are smectites?Layer charge from substitutions:Octahedral: Mg2+, Fe2+, Mn2+or Al3+Tetrahedral: Al3+ or Fe3+ for Si4+Interlayer expands (up to 30% by volume); swelling claysSeparation depends on interlayer cations present & ionic strength of solution

What are smectites?Platelet Dimensions200-500 nm in diameter0.93 nm thick

General Formula: A0.3D2-3[T4O10]Z2 nH2O

2:1 1:1Ratio of tetrahedral: octahedral sheetsWeathering

Smectite Group MembersAllettite: Ca0.2Mg6(Si,Al)8O20(OH)4 4H2O

Beldellite: (Na,Ca0.5)0.3Al2(Si,Al)4O10(OH)2 nH2O

Hectorite: Na0.3(Mg,Li)3Si4O10(F,OH)2

Montmorillonite: (Na,Ca)0.33(Al,Mg)2Si4O10(OH)2nH2O

Nontronite: Na0.3Fe2(Si,Al)4O10(OH)2 nH2O

Saponite: Ca0.25(Mg,Fe)3(Si,Al)4O10(OH)2 nH2OSauconite: Na0.3Zn3(Si,Al)4O10(OH)2 4H2O

Stevensite: (Ca,Na)xMg3Si4O10(OH)2

Swinefordite: Li(Al,Li,Mg)4(Si,Al)8O20,(OH,F)4 xH2O

Volkonskoite: Ca0.3(Cr,Mg,Fe)2(Si,Al)4O10(OH)2 4H2O

Yakhontovite: (Ca,Na)0.5(Cu,Fe,Mg)2Si4O10(OH)2 3H2O

Zincsilite: Zn3Si4O10(OH)2 4H2O

ThixotrophyAbility to form stiff gels at low concentrations that change viscosity as shear application changes

No Shear: Double layers repelled & + surface attracted to - edge house of cards configuration

Shear: Aligns clay particles & viscosity

Smectite-Illite (S-I) TransitionTemperature, Pressure & Time

Abiotic Reaction:

300-450oC100 MPa4-5 Months

Biological Reaction:

Metal-Reducing BacteriaRoom Temperature1 atm2 weekshttp://www.sciencemag.org/cgi/reprint/303/5659/830.pdf

Structural Comparison: Smectite to Illite

On the mechanical role of smectite in subduction zonesPeter VrolijkDepartment of Geological Sciences,University of Michigan

What is a decollement?A shallow dipping to subhorizontal fault or shear zoneFrench: UngluingThe detachment of the upper cover from its substratum Also known as:- Detachment fault- Decollement Fault- Sole Fault

(Image modified from Demians lecture sketch)

Objective of the StudyFind out if subduction zone decollements occur in smectite-rich horizons

Review previous research:Rock DeformationPhysical Properties of SedimentsSmectite-Illite (S-I) Transition

How these effect seismicity in subduction zones

Why is this research relevant?The characteristics of sediments at subduction zones could tell us where decollements form

By understanding what happens at decollements we learn more about the S-I transition

Aspects of the S-I transition process at decollements tells us something about seismicity

Previous Research: Subduction ZonesSediment-Rich:Long decollementsSmectite-rich sedimentsDecollements:Formation is associated with prism structure Fluid pressure friction tapering ploughing up of prism stress & zones of porosity(Image modified from Demians lecture sketch)

Previous Research: Subduction ZonesPelagic Sediments: subducted

Terrigenous Deposits: accrete at prism base

Changes in mechanical properties result in peeling of terrigenous from pelagic

Decollement is just beneath area of partition at base of smectite-rich zone(Image modified from Demians lecture sketch)

Methods: Data CollectionSediments from an active decollement have only been collected once

Seismic reflection data mineralogical composition of sediments

Decollement geometry from drill cores

(Image taken from Demians Lecture Presentation)

ResultsNot enough data

Smectites & decollement formation

More drilling needed

2 Regions with the most data:

Decollements occur in smectite-rich zones(Image taken from Demians Lecture Presentation)

Implications: For Decollement GenerationMineralogical Reasons why smectite is weakest sediment in subduction zones

Recall smectite structure

Water = weakness (H-bonds)

Relative Deformation Stresses

Water tightly adsorbed to smectite

Remains during deformation ( porosity)

What dictates smectite distribution in ocean sediments?Transformation from volcanic ash

Abundant ash

Sufficient time & pressure

Between pelagic & hemipelagic sediments (due to dilution & age)

Detrital clay influx

Sediment Minerology Evolution: S-I TransitionMetamorphic transitions on subducting plate

80% complete 100-110oC

Rate of subduction; S-I transition rate

Subduction Observations:

Japan Trench (fast)

Barbados (slow)

Implications: For Subduction ZonesS-I: Sediment StrengtheningHow it relates to seismicity

Does this lead to development of the seismic front?During S-I, smectite (as it is converted to illite)Decollement strengthenedFriction Deformation & strain on overriding plateSeismicity results

ConclusionsDecollements form in smectite-rich sediments

More drilling needed at prisms

Columb Wedge Theory: coefficient of basal sliding friction may need modification

Seismicity related to strengthening (due to S-I)

Comments & Criticisms: Where to Begin?Overgeneralization from too small a sample size

Too little is known about the lithology to draw conclusions about the relationship of smectite to decollement formation

Keeping physical models in mind (structure, hydration, the effect of shear, S-I, etc.), Is the model logical?Shear reduces viscosity (house of cards to plates)S-I (squeezes out water; no more H-bonds to break)Leads to strengtheningSeismicity

Would I have published this? NO!!!

??QuESTIONS??

For more thoroughly exhilarating reading on smectites:Alba, M.D, et al. (2001) Hydrothermal reactivity of Lu-saturated smectites: Part I. A long-range order study. American Minerologist. 86: 115-123.Alba, M.D., et al. (2001) Hydrothermal reactivity of Lu-saturated smectites: Part II. A short-range order study. American Minerologist. 86: 124-131Blum, 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.pdfCervini-Silva, J., et al. (2001) Transformation of Chlorinated Aliphatic Compounds by Ferruginous Smectite. Environmental Science and Technology. 35: 805-809.Ghosh, A & McSween Jr., H.Y. Normative Minerology and Possible Origin of Mars Pathfinder Soils. Online. 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.Johnston, C.T. et al. Spectroscopic Study of NitroaromaticSmectite Sorption Mechanisms. Environmental Science & Technology. American Chemical Society.Kasama, T., et al. (2001) Experimental mixtures of smectite and rectorite: Re-investigation of fundamental particles and interparticle diffraction. American Minerologist. 86: 105-114. 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. Stixrude, L & Peacor, D.R. (2002) First-principles study of illite-smectite and implications for clay-mineral systems. Nature. 420: 165-168.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.Vrolijk, P. & van der Pluijm, B.A. (1999) Clay Gouge. Journal of Structural Geology. 21: 1039-1048.

For more thoroughly exhilarating reading on smectites:http://www.smm.org/general_info/bhop/Smectiteandbentoniteclay.htmlhttp://www.mindat.org/min-11119.htmlhttp://www.renneckerltd.com/rltd_aboutsmectite.htmhttp://www.rtvanderbilt.com/veegum.pdfhttp://www.claytone.net/clay/cchem.htmlhttp://www7430.nrlssc.navy.mil/biogeochemistry/smectiteillite.htmhttp://chemical.kowa.com/coop_chemical.htmlhttp://www.cnr.berkeley.edu/~rsutton/cmsabstract.htmlhttp://www.rtvanderbilt.com/veegumdd_a.htmhttp://www.oilvel.com/Dutta_quotes2.htmlhttp://www.workpage.com/e/58/177e.htmhttp://www.renneckerltd.com/Products/rltd_magnabrite01.htmhttp://www-odp.tamu.edu/publications/184_SR/VOLUME/CHAPTERS/210.PDFhttp://cips.berkeley.edu/research/cervini-silva_transformation.pdfhttp://www.cnr.berkeley.edu/~rsutton/modelclay.htmlhttp://www.cnr.berkeley.edu/~rsutton/clays.htmlhttp://www.glossary.oilfield.slb.com/Display.cfm?Term=smectite+clayhttp://www.permont.com/11/1112/tsld002.htmhttp://www.geo.wvu.edu/%7Ekite/Geol321Lect04Weathering2002/http://members.segweb.org/PDF97-2/221_Prry.pdfhttp://www.quanterra.org/Patissier.htmhttp://www-odp.tamu.edu/publications/178_SR/chap_08/chap_08.htmhttp://www.osti.gov/energycitations/product.biblio.jsp?osti_id=343765http://www.claytone.net/pain/pain.htmlhttp://www.eytonsearth.org/claychemistry.htmlhttp://www.seismo.berkeley.edu/~jill/silweath.htmlhttp://www.gly.uga.edu/schroeder/geol3010/smectite.gifhttp://www.petrotech-assoc.com/prod01.htmhttp://www.glossary.oilfield.slb.com/DisplayImage.cfm?ID=183http://energy.usgs.gov/factsheets/Petroleum/SEM.htmlhttp://homepages.uc.edu:8000/~maynarjb/603/GeochemWater/ClayImages.htmhttp://www.kimb.or.kr/im_data/picture/mineral/img/montmorillonite.jpg