Clays and Clay Minerals III

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Aubrey Barrett
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1 Clays and Clay Minerals III Headline of the weekend 1

volcanism K-Bentonite begin as smectite rich layers; then

2 Headline of the weekend Volcanic activity Ordovician K- Bentonites K-Bentonites represent episodes of explosive volcanism K-Bentonite begin as smectite rich layers; then convert to illit- smectite rich beds over time Reduces value for industrial applications 2

Ordovician K- Bentonites but have values as stratigraphic marker horizons Remnants of large caldera-forming events Ordovician K- Bentonites Prominent ash beds in the USA and Northern Europe Deicke

3 Ordovician K- Bentonites but have values as stratigraphic marker horizons Remnants of large caldera-forming events Ordovician K- Bentonites Prominent ash beds in the USA and Northern Europe Deicke and Millbrig K-Bentonits were correlated with geophysical logs and chemical fingerprints throughout the eastern midcontinent of the USA the Millbrig bed covers an area of at least 2.2 x 10 6 km 2 Kinnekulle bed covers an area of at least 6.9 x 10 5 km 2 Calcultated volumes of silisic magma to produce these beds: Millbrig: 1509 km 3 Kinnekulle: 972 km 3 3

Ordovician K- Bentonites Results of supervolcano eruption The Deicke-, Millbrig- and Kinnekulle-beds are among the largest ash falls recorded They are the

the eruption of Krakatau, Indonesia (1883) Last supervolcano eruption Toga ca.

4 Ordovician K- Bentonites Results of supervolcano eruption The Deicke-, Millbrig- and Kinnekulle-beds are among the largest ash falls recorded They are the result of supervolcano events A supervolcano is a volcano that eject more than 10 9 tons of ash Explosion of a supervolcano is about 30 times stronger than the eruption of Krakatau, Indonesia (1883) Last supervolcano eruption Toga ca years ago Bentonite Definition: Bentonites are clay rocks Mainly formed from alteration of pyroclastic/ volcanoclastic rocks Bentonites consist predominantly of smectite Bentonite deposit formed from pyroclastic flow (Milos) 4

The clay cycle Formation bentonites Diagenetic alteration of volcanic glass Hydrothermal alteration of volcanic glass Formation of smectite- rich sediments in salt lakes and sabkha

facts of soap for bathing (described by Aristophanes 405 BC) Bentonite from the same deposit is still mined today for use in detergents.

5 The clay cycle Formation bentonites Diagenetic alteration of volcanic glass Hydrothermal alteration of volcanic glass Formation of smectite- rich sediments in salt lakes and sabkha environment (dissolution of detrital smectites) Use of bentonite Prior to 400 BC: Bentonite from Kimolos was used in the Mediterranean to clean wool and as a component Some historical facts of soap for bathing (described by Aristophanes 405 BC) Bentonite from the same deposit is still mined today for use in detergents. Native Americans used bentonite to clean hides American settlers used bentonite to clean clothing and as axle grease for wagons Until the end of 19th century, bentonite was used in small quantities only: for cleansing and for medical purposes 5

6 Bentonite Bentonite in modern life USA 2006: Bentonite production statistics by end use What makes smectites unique? Small grain size (compared to other clay mineral) large surface area top: smectite bottom: chlorite 6

7 More unique properties of smetites (from economical point of view) Large surface area (up to 800 m 2 /g) Negative layer charge (120 meq/g) Exchangeable surface cations Hydration energy of exchangable cations make a strong affinity for water Each type has his own unique applications Results in strong interparticle forces significant for bulk physical properties including: Swelling Sealing Adhesive characteristics Two primary types of smectites (from economical point of view) Na-bentonite: Absorb large amount of waters Form viscous, thixotropic suspensions Each type has his own unique applications Ca-bentonite: Swelling capabilities Does not stay suspended Low water absorption 7

8 Pet litters Prior to 1980s most pet litter products were composed of sand or non-clumping clays In the late 1980s Nasmectite was discovered to be ideal for making clumping cat litter Drilling Fluid Mud flow in borehole Pumped down the drill string Raises in the annulus Cooling of the drill bit Carries the cuttings to the surface Prevents from blocking the string (thixotropy) 8

9 Drilling Fluid Thixotropy Fluid forms gelled structure when not subject to shearing and liquefys when agitated Necessary for fast drilling (cooling) Efficient lifting of cuttings Support cuttings when mud flow stoppes Thixotropy Adding bentonite to paint prevents the pigments from settling Increases workability Prevents from smearing 9

Metal Casting Cast-iron products are made in

bentonite as bonding agent (mixed with sand, coal

recycled Na- and Cabentonites are used Iron Ore

ore for steel making Ore is finely ground to

ore creates problems during shipping and handling

10 Metal Casting Cast-iron products are made in foundry moulds Green sand moulding contains bentonite as bonding agent (mixed with sand, coal and small amount of water) Mould material is recycled Na- and Cabentonites are used Iron Ore Pelletizing Allows use of abundant low grade iron ore for steel making Ore is finely ground to liberate the iron oxide Fineness of powdered iron ore creates problems during shipping and handling Use of natural Nabentonite as a binding agent for making pellets and briquettes 10

decolorize and clarify animal, vegetable and

used as a fining agent for wine; absorption of

flocculation Civil Engineering Na-bentonite is

water level: bentonite slurry is used for

11 Bleaching and Clarifying Ca-smectite (especially after acid treatment) is used to decolorize and clarify animal, vegetable and mineral oil from impurities Na-smectite is used as a fining agent for wine; absorption of positively charged proteins; removal though flocculation Civil Engineering Na-bentonite is used for low-permeability insitu barriers; slurry walls, slurry trenches Tunnel excavation in unconsolidated soil below ground water level: bentonite slurry is used for stabilizing the excavation face, to lubricate and to seal the tail of the TBM 11

Applied Geology A real situation for a consulting geologist: multiple

single borehole and installation of a multiple-screen piezometer Municipal

Barriere weist im Ablagerungsbereich der Deponie eine maximale Gebiets- bzw.

12 Applied Geology A real situation for a consulting geologist: multiple aquifers have to be monitored Drilling of cluster boreholes or Drilling of a single borehole and installation of a multiple-screen piezometer Municipal landfill Excerpt from the Swiss regulation on disposal sites Die geologische Barriere weist im Ablagerungsbereich der Deponie eine maximale Gebiets- bzw. Gebirgsdurchlässigkeit von 1.0 x 10-7 m/s und eine minimale Mächtigkeit von 7 m auf 12

13 Disposal site Koelliken Former clay pit Disposal of waste from the chemical industries Several attempts to encapsulate the waste Finally decision was taken to remove the waste and incinerate it in a special kiln Disposal site Koelliken Slurry wall to prevent from seepage 13

14 Disposal site Koelliken A roof prevents from release of toxic gases Low pressure atmosphere inside the enclosed area Disposal site Koelliken Disposed waste is recovered and separated 14

Bentonite based barrier systems Construction of new disposal sites with compacted clay liners (CCL) or geosythetic clay liners (low permeable composite material with 10-mm layer

Canisters are placed in boreholes or galleries in geologically stable formations Canisters are enbedded in bentonite Bentonite = tertiary engineered buffer - limit entry of water

15 Bentonite based barrier systems Construction of new disposal sites with compacted clay liners (CCL) or geosythetic clay liners (low permeable composite material with 10-mm layer of Na-bentonite) Nuclear waste entombement Bentonite is part of a multi-barrier system Barriers: Spent fuel is solidified and encased in corrosion resistant in canisters Canisters are placed in boreholes or galleries in geologically stable formations Canisters are enbedded in bentonite Bentonite = tertiary engineered buffer - limit entry of water into the waste - contribute to retension of radionuclides - assist in dissipation of heat from radioactive decay - provide cushoning of canisters against mechanical shock and compression 15

16 Nuclear waste entombment Lifetime of bentonite as engineered barrier/buffer 3 phases: 1. phase: (0 to ca. 100 years): hydration, swelling and compression of barrier; subject to strong radiation and physico-chemical processes at temperatures up to 220 C 2. phase: ( ca. 100 to 1000 years): exposure to continued but moderating thermal gradient while barrier continues to consolidate 3. phase: (1000 to years): thermal gradients are no concern but unknown geological, hydrological and climatic changes FEBEX Grimsel Test Site Excavation of a tunnel drift (diameter 2.3 m) Host rock : Grimsel Granodiorite 16

17 FEBEX Grimsel Test Site Hydraulic characterization of water conducting zones intersecting the tunnel FEBEX Grimsel Test Site Filling the tunnel with bentonite blocks (around a central steel liner to facilitate installation and recovery of the canister ) 17

18 FEBEX Grimsel Test Site 2 heaters with the dimension and weight of waste canisters were installed FEBEX Grimsel Test Site Heater inside the bentonite barrier 18

19 FEBEX Grimsel Test Site Dismantling of the bentonite liner after 5 years of heating To be noted: the gaps between the bentonite blocks are closed as a result of swelling SELFRAC Mont Terri URL Simulation of swelling pressure and it s effect on the EDZ 19

20 SELFRAC Mont Terri URL A plate loading apparatus is used to apply a load onto the tunnel wall SELFRAC Mont Terri URL Schematic overview of the equipped tunnel wall Instruments: packer systems for hydraulic testing and borehole extensometers t for measurement of displacement 20

$SELFRAC Mont Terri URL Displacement represents a closer of fractures$ in decreasing hydraulic conductivity Decrease of a factor 60 between zero

in decreasing hydraulic conductivity Decrease of a factor 60 between zero

8 MPa (m 2 /s) Transmissivity 10-8 6 Test 10 Test 11 4 Test 16 2 Test 12

m 2 /s Test 18 10-10 Right scale: Load in MPa (red line) 3 Bottom: Time

$Selfhealing Experiment 4 Test 11 to 18 = Selfrac Experiment) 4 2 01.05.$

21 SELFRAC Mont Terri URL Displacement represents a closer of fractures around the tunnel (EDZ) SELFRAC Mont Terri URL Increasing load resulted in decreasing hydraulic conductivity Decrease of a factor 60 between zero load and the maximum load of 4.8 MPa (m 2 /s) Transmissivity Test 10 Test 11 4 Test 16 2 Test 12 Test Test Left scale: Calculated transmissivity in m 2 /s Test Right scale: Load in MPa (red line) 3 Bottom: Time axes date and days after first saturation of boreholes 6 (Test 10 = Selfhealing Experiment 4 Test 11 to 18 = Selfrac Experiment) Δt (d): time since 1. saturation Load Pressure (M MPa) 21

Clays and Clay Minerals

Clays and Clay Minerals Fields of interest for clays Various definitions Acients: Earths in the earth-air-fire-water system Definition of clay depends on discipline: Geologist grain size