Sheet silicates JD Price Silicate Structure Silicate Structure - - PowerPoint PPT Presentation

Sheet silicates

JD Price

Silicate Structure

Silicate Structure

(SiO2)

Phyllosilicates

Micas

Muscovite KAl2(AlSi3O10)(OH,F)2 Biotite Phlogopite KMg3(AlSi3O10)(OH,F)2 Annite KFe3(AlSi3O10)(OH,F)2

Image from mineral.galleries.com

Image from Blackburn and Dennen, 1988

New experiments New experiments Two biotites from the Two biotites from the Seridó Seridó fold belt

• ld belt

PPPL PPPL schist 2.5 wt % chist 2.5 wt %

• St. Andre schist
• St. Andre schist 0.3

.3 wt.% wt.% 750 ºC, 0.4 GPa 750 ºC, 0.4 GPa AFSQ Buffered AFSQ Buffered

F-OH exchange

Curve fit to Ci / C0 = 1 - erf [x(4Dt)-1/2] D = 2.71 E-15 m2/s (c - perpendicular)

Diffusion

A,B,C: F-OH-Cl Ap (Brenan, 1983) D: F-OH Trm (Brabander et al, 1995) E,F,G: O Amp (Farver and Giletti, 1985) H,I,J: O Mica (Fortier and Giletti,1991) K, L O: Ttn (Zhang et al, 2004) M, N, O: H Amp (Graham et al., 1984) P: H in Msc (Graham, 1981)

The new value is elevated relative to the diffusivities

• f other

relevant components in micas and

• ther F-

bearing minerals

Diffusivities

Serpentine Group Lizardite, orthochrysotile, clinochrysotile (Mg,Fe)3SiO5(OH)4

Image from mineral.galleries.com

Miscellaneous Sheet Silicates

･Amesite (Mg, Fe)4Al4Si2O10(OH)8 ･Baileychlore (Zn, Fe+2, Al, Mg)6(Al, Si)4O10(O, OH)8 ･Chamosite (Fe, Mg)3Fe3AlSi3O10(OH)8

Chlinochlore (Fe, Mg)3Fe3AlSi3O10(OH)8

･Cookeite LiAl5Si3O10(OH)8 ･Corundophilite (Mg, Fe, Al)6(Al, Si)4O10(OH)8 ･Daphnite (Fe, Mg)3(Fe, Al)3(Al, Si)4O10(OH)8 ･Delessite (Mg, Fe+2, Fe+3, Al)6(Al, Si)4O10(O, OH)8 ･Gonyerite (Mn, Mg)5(Fe+3)2Si3O10(OH)8 ･Nimite (Ni, Mg, Fe, Al)6AlSi3O10(OH)8 ･Odinite (Al, Fe+2, Fe+3, Mg)5(Al, Si)4O10(O, OH)8 ･Orthochamosite (Fe+2, Mg, Fe+3)5Al2Si3O10(O, OH)8 ･Penninite (Mg, Fe, Al)6(Al, Si)4O10(OH)8 ･Pannantite (Mn, Al)6(Al, Si)4O10(OH)8 ･Rhipidolite (prochlore) (Mg, Fe, Al)6(Al, Si)4O10(OH)8 ･Sudoite (Mg, Fe, Al)4 - 5(Al, Si)4O10(OH)8 ･Thuringite (Fe+2, Fe+3, Mg)6(Al, Si)4O10(O, OH)8

Chlorite group

Perkins, UND

Asbestos (Part II)

Chrysotile serpentine from the RPI collection

Sheet silicates can form asbestos

• habits. Chrysotile is the most

abundant - mined in Canada for use in high-temperature machinable, pressform, and unconsolidated fiber applications. Fire resistance High-temperature insulation Strengthening material

Lac d'Amiante, QC Ophiolite (obducted

• ceanic crust) rich

in serpentine. Asbestos has been mined since ancient time - long revered as a miracle material for its inflammability.

Image from Klein and Hurlbut, 1985

Chrysotile’s tubes

Image from Blackburn and Dennen, 1988

The main cause of concern - mesothelioma (cancer of the pleural cells). This rare type of cancer seems only relatable to high fiber occupational exposure - Mossman et al.

Left - Malignant mesothelioma from Chainian & Pass, 1997

Asbestosis - another

• ccupational disease where fibers

have scarred the lungs

Asbestos and health

So far, there is insufficient evidence for an effect due to casual exposure. Is asbestos worth the attention? Cancer remains enigmatic - cause and effect relationship

Asbestos and health

Crocidolite (amphibole) - 25mL per min per mouse produces significant and early increase in mutations. Rhin et al., 2000 Chrysotile (tube) ~20 mg per rat show correlation between fiber concentration and chance of mesothelioma Jurand et al. In general, crocidolite has a much more pronounced effect. Is it just crocidolite (riebeckite) or is it an amphibole problem?

Particles that may be

• bioactive. Mucus membranes

can remove large particles, macrophages small equant

• nes. Macrophages may

struggle with elongate particle less than 100 microns. Electron optics are necessary to resolve airborne asbestos

• particles. Diffractometry is

needed to characterize mineral. SE image of fibers

Dust

In general - dusts are not healthy. Prolonged exposure to any mineral dust may be hazardous to health

Silicosis - long-term exposure to crystalline silica. Phage resistant, small particles remain intact after phagiocytosis. Pneumonoultramicroscopicsilicovolcanoconiosis* is silicosis specifically brought on by long-term exposure to volcanic ash.

Boys** in Yakama, WA wear dust masks in the days after the May 18, 1980 eruption of Mt. Saint

• Helens. Yakama, in

central Washington, was darkened by ash on May 18. Dust in the environment is difficult to remediate

*Longest word in OED and Websters, also mentioned on The Simpsons 2F07 **Prof owned same sporty orange vest in 1980, however his bike was 30% less cool (darn fenders!).

Clays

Kaolinite Ralph L. Kugler, Milwaukee Public Museum

Kaolinite Al2Si2O5(OH)4 Polymorphs (kaolinite group) halloysite, dickite and nacrite Silicate sheets (Si2O5) bonded to gibbsite layers (Al2(OH)4). The silicate and gibbsite layers are tightly bonded together with only weak bonding existing between the s-g paired layers.

Clays

Smectite-Montmorillionite Group smectite, pyrophyllite, talc, vermiculite, sauconite, saponite, nontronite and montmorillonite (Ca, Na, H)(Al, Mg, Fe, Zn)2(Si, Al)4O10(OH)2 - xH2O Gibbsite layer is partly replaced by Brucite-like layer. Variable amounts of water molecules lie between the s-[g or b]-s sandwiches.

Image from mineral.galleries.com

Illite Group Hydrobioitite, illite, brammalite Hydrated muscovite (K, H)Al2(Si, Al)4O10(OH)2 - xH2O These are the minerals most commonly found in

• shales. More variable water between s-g-s

configurations

TEM images of hydrothermal alteration from smectite to illite (scale = 0.5 m)

Clays

Clay grains are very small - reflecting the domains of mineral alteration. Resolution requires atomic-scale electron techniques

• r XRD

Many clays are able to incorporate variable amounts of water within their structure. This has a pronounced effect on their volume at the atomic scale. Diagram shows shift of (001) peak with increasing water. Na smectite can swell 20x from dry to saturated.

Swell

Red - mostly high swelling Blue - less 50% high swelling Orange - mostly moderate swelling Green - less than 50% moderate swelling Brown - little to no swelling Yellow - no data US Soils - USGS K Taylor Marl (Ca-clays)

Igneous

ultramafic

Igneous

mafic

Metamorphic

High P, T

Sedimentary

biogenic

Sedimentary

Fine clastic

Igneous

intermediate

Subduction

Stilbite NaCa2Al5Si13O36 14H2O Natrolite Na2Al2Si3O10 2H2O Heulandite (Ca, Na)2-3 Al3(Al, Si)2 Si13O36 12H2O

Zeolite - wet tectosilicates

Diagram from E.B Watson

Conditions: moderate P & T Minerals: Lizardite, crysodolite Origin: mafic (basalt, gabbro) - alteration of olivines and pyroxenes.

Serpentinite

• 1. Precipitants and water-lain

fragments, low T and P, Sedimentary.

• 2. Re-equilibrated materials, wide

range of T and P, Metamorphic.

• 3. Melted materials, high T,

Igneous.

Mechanical Chemical

Assembling minerals

Surface (map or plan view) - cover much of the earth. Depth (cross section) - thin veneer. Easy to observe, and contain economic materials (including fossil fuels).

Abundance

New York Bedrock

Extensive Paleozoic sediments

Map modified by T. Wayne Furr, after Branson and Johnson; WWW version by Jim Anderson.)

Thick sediments

Fragments of pre-existing rocks. The fragments are produced by weathering and erosion. Weathering - mechanical and chemical breakdown

• f rocks and minerals.

Erosion - fragments are moved away from source (downhill). May operate together or separately.

Clastic

Physical: hardness, fracture, cleavage Chemical: Resistance of bonds to chemical attack Si-O bonds very strong. Increased polymerization means more resistant. Tectosilicates are among the more resistant

• components. Solubility of silica in water at STP

aids stability.

Weathering

Corner areas

Elephant rocks, Saint François Mountains, MO. Tor type weathering of widely-spaced jointed granites.

Variable resistance

Resistant sandstone remnant on shale, Green River, WY.

Press and Sevier, 1986

Weathering

34.7 m 23.3 m 2 7 . 5 m 2 . 5 m

Mount Scott Granite Oxides

Diffusive alteration

Pristine igneous rock oxides become more

• xidized near

exposed surface. Note alteration at 27.5m along fractures in grains.

If a mineral is abundant in the crust and resistant to chemical attack, it is likely to be a major constituent of clastic sedimentary rock.

Good clastic materials

Small and less dense Phyllosilicates (cleavage) These can be transported with lower amounts of energy Fast versus slow moving streams Wind (loess) Clay minerals

Chemical and mechanical breakdown of rocks results in particles of increasingly smaller size. Earth scientists have formal names for size ranges Cobble > 10 mm Gravel 1 mm – 10 mm

Size matters

0.001 0.01 0.1 1 10 100 1000 10000 Boulder Cobble Pebble Granule

• V. coarse sand

Coarse sand Medium sand Fine sand

• V. fine sand

Coarse silt Medium silt Fine silt

• V. fine silt

Clay

Grain size (mm)

Press and Sevier, 1986

Gravity driven

Clastic particles transported by water movement

Stream deposits

Unconsolidated sediments reveal the clastic processes at work in cut bank adjacent to a small

• stream. Channel

movement layers conglomertic sediments on top of bank sands. Sands at top reworked by wind. Big Bend NP, TX.

Peter Mozley, NM Tech Website

Wind and water

Large particles of eroded rock, typically embedded in finer particles (typically silicate) Origin: High energy fluid transport

James Madison Univ. Sedimentology

Conglomerate

Sand sized particles (typically quartz, feldspar, or rock fragments – typically silicate) from eroded rock Origin: Moderate energy fluid transport

Sandstone

Silt sized particles (typically quartz and feldspar framework silicate) from eroded rock Origin: Low energy fluid transport

James Madison Univ. Sedimentology

Siltstone

Silt sized particles (typically clay – sheet silicate) from eroded and highly weathered rock Origin: Low energy fluid transport

James Madison Univ. Sedimentology

Q: What is the difference between siltstone and shale?

Shale

Press and Sevier, 1986

(Compaction, Limited re-equilibration, and Cementation) Continuing deposition, sediments buried (increase in P < 5 kbar and T < 100 oC). Sediments are frequently porous (grainsize dependent), lots

• f fluids.

Sedimentary minerals grow Minerals grow between grains

Diagenesis

10% GROWTH Pores

Preservation

Modern desiccation cracks in mud 300 Ma desiccation cracks in shale