Sheet silicates JD Price
Silicate Structure
Silicate Structure
(SiO2)
Phyllosilicates Micas Muscovite KAl 2 (AlSi 3 O 10 )(OH,F) 2 Biotite Phlogopite KMg 3 (AlSi 3 O 10 )(OH,F) 2 Annite KFe 3 (AlSi 3 O 10 )(OH,F) 2 Image from mineral.galleries.com
Image from Blackburn and Dennen, 1988
F-OH exchange New experiments New experiments Two biotites from the Two biotites from the Seridó Seridó fold belt old belt PPPL PPPL schist 2.5 wt % chist 2.5 wt % St. Andre schist 0.3 St. Andre schist .3 wt.% wt.% 750 ºC, 0.4 GPa 750 ºC, 0.4 GPa AFSQ Buffered AFSQ Buffered
Diffusion Curve fit to C i / C 0 = 1 - erf [ x (4 Dt ) -1/2 ] D = 2.71 E-15 m 2 /s (c - perpendicular)
Diffusivities The new value is elevated relative to the diffusivities of other relevant components in micas and other F- bearing minerals K, L O: Ttn (Zhang et al, 2004) A,B,C: F-OH-Cl Ap (Brenan, 1983) M, N, O: H Amp (Graham et al., 1984) D: F-OH Trm (Brabander et al, 1995) P: H in Msc (Graham, 1981) E,F,G: O Amp (Farver and Giletti, 1985) H,I,J: O Mica (Fortier and Giletti,1991)
Miscellaneous Sheet Silicates Serpentine Group Lizardite, orthochrysotile, clinochrysotile (Mg,Fe) 3 SiO 5 (OH) 4 Image from mineral.galleries.com
Chlorite group ･ Amesite (Mg, Fe) 4 Al 4 Si 2 O 10 (OH) 8 ･ Baileychlore (Zn, Fe +2 , Al, Mg) 6 (Al, Si) 4 O 10 (O, OH) 8 ･ Chamosite (Fe, Mg) 3 Fe 3 AlSi 3 O 10 (OH) 8 Chlinochlore (Fe, Mg) 3 Fe 3 AlSi 3 O 10 (OH) 8 ･ Cookeite LiAl 5 Si 3 O 10 (OH) 8 ･ Corundophilite (Mg, Fe, Al) 6 (Al, Si) 4 O 10 (OH) 8 ･ Daphnite (Fe, Mg) 3 (Fe, Al) 3 (Al, Si) 4 O 10 (OH) 8 ･ Delessite (Mg, Fe +2 , Fe +3 , Al) 6 (Al, Si) 4 O 10 (O, OH) 8 ･ Gonyerite (Mn, Mg) 5 (Fe +3 ) 2 Si 3 O 10 (OH) 8 ･ Nimite (Ni, Mg, Fe, Al) 6 AlSi 3 O 10 (OH) 8 ･ Odinite (Al, Fe +2 , Fe +3 , Mg) 5 (Al, Si) 4 O 10 (O, OH) 8 ･ Orthochamosite (Fe +2 , Mg, Fe +3 ) 5 Al 2 Si 3 O 10 (O, OH) 8 ･ Penninite (Mg, Fe, Al) 6 (Al, Si) 4 O 10 (OH) 8 ･ Pannantite (Mn, Al) 6 (Al, Si) 4 O 10 (OH) 8 ･ Rhipidolite (prochlore) (Mg, Fe, Al) 6 (Al, Si) 4 O 10 (OH) 8 Perkins, UND ･ Sudoite (Mg, Fe, Al) 4 - 5 (Al, Si) 4 O 10 (OH) 8 ･ Thuringite (Fe +2 , Fe +3 , Mg) 6 (Al, Si) 4 O 10 (O, OH) 8
Asbestos (Part II) 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 Chrysotile serpentine from the RPI collection
Lac d'Amiante, QC Ophiolite (obducted oceanic crust) rich in serpentine. Asbestos has been mined since ancient time - long revered as a miracle material for its inflammability.
Chrysotile’s tubes Image from Klein and Hurlbut, 1985
Image from Blackburn and Dennen, 1988
Asbestos and health 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 occupational disease where fibers have scarred the lungs 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?
Dust Particles that may be bioactive. Mucus membranes can remove large particles, macrophages small equant ones. Macrophages may struggle with elongate particle less than 100 microns. Electron optics are necessary to resolve airborne asbestos particles. Diffractometry is needed to characterize SE image of fibers mineral. 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 Al 2 Si 2 O 5 (OH) 4 Polymorphs (kaolinite group) halloysite, dickite and nacrite Silicate sheets (Si 2 O 5 ) bonded to gibbsite layers (Al 2 (OH) 4 ). The s ilicate and g ibbsite layers are tightly bonded together with only weak bonding existing between the s-g paired layers. Kaolinite Ralph L. Kugler, Milwaukee Public Museum
Clays Smectite-Montmorillionite Group smectite, pyrophyllite, talc, vermiculite, sauconite, saponite, nontronite and montmorillonite (Ca, Na, H)(Al, Mg, Fe, Zn) 2 (Si, Al) 4 O 10 (OH) 2 - xH 2 O 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)Al 2 (Si, Al) 4 O 10 (OH) 2 - xH 2 O These are the minerals most commonly found in shales. More variable water between s-g-s configurations
Clays Clay grains are very small - reflecting the domains of mineral alteration. Resolution requires atomic-scale electron techniques or XRD TEM images of hydrothermal alteration from smectite to illite (scale = 0.5 � m)
Swell 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.
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)
Subduction Sedimentary Fine clastic Sedimentary biogenic Igneous intermediate Igneous mafic Metamorphic Igneous High P, T ultramafic
Zeolite - wet tectosilicates Stilbite NaCa 2 Al 5 Si 13 O 36 14H 2 O Natrolite Na 2 Al 2 Si 3 O 10 2H 2 O Heulandite (Ca, Na) 2-3 Al 3 (Al, Si) 2 Si 13 O 36 12H 2 O
Diagram from E.B Watson
Serpentinite Conditions: moderate P & T Minerals: Lizardite, crysodolite Origin: mafic (basalt, gabbro) - alteration of olivines and pyroxenes.
Assembling minerals Chemical 1. Precipitants and water-lain fragments, low T and P, Sedimentary. Mechanical 2. Re-equilibrated materials, wide range of T and P, Metamorphic. 3. Melted materials, high T, Igneous.
Abundance 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).
New York Bedrock
Extensive Paleozoic sediments
Thick sediments Map modified by T. Wayne Furr, after Branson and Johnson; WWW version by Jim Anderson.)
Clastic Fragments of pre-existing rocks. The fragments are produced by weathering and erosion. Weathering - mechanical and chemical breakdown of rocks and minerals. Erosion - fragments are moved away from source (downhill). May operate together or separately.
Weathering 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.
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.
Weathering Press and Sevier, 1986
Diffusive alteration Pristine igneous 2 34.7 m 7 . rock oxides 5 m become more oxidized near exposed surface. 23.3 m Note alteration at 2 0 . 27.5m along 5 m fractures in grains. Mount Scott Granite Oxides
Good clastic materials 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.
Clay minerals Small and less dense Phyllosilicates (cleavage) These can be transported with lower amounts of energy Fast versus slow moving streams Wind (loess)
Size matters 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
Grain size (mm) 10000 0.001 1000 Boulder 0.01 100 0.1 10 1 Cobble Pebble V. coarse sand Granule Coarse sand Medium sand Fine sand V. fine sand Coarse silt Medium silt Fine silt V. fine silt Clay
Recommend
More recommend
