Weathering L. Hinnov February 17, 2012 Reading list:

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Presentation transcript:

Weathering L. Hinnov February 17, 2012 Reading list: Brantley, S., and 26 others, 2011, 12 testable hypotheses on the geobiology of weathering, Geobiology, 9, 140-165. Hamblin, W.K. and Dr. Eric H. Christiansen, E.H., 2004, Chapter 10 - Weathering, Earth's Dynamic Systems, Tenth Edition, Prentice Hall. Kump, L., Brantley, S., and Arthur, M., 2000, Chemical weathering, atmospheric CO2 and climate, Annual Reviews of Earth and Planetary Science, v. 28, pp. 611-667. Liu, Z., Dreybrodt, W., and Liu, H., 2011, Atmospheric CO2 sink: silicate weathering or carbonate weathering? Applied Geochemistry, v. 26, pp. S292-S294. Riebe, C., Kirchner, J.W., and Finkel, R.C., 2004, Erosional and climatic effects on long-term chemical weathering rates in granitic landscapes spanning diverse climate regimes, Earth and Planetary Science Letters, v. 224, pp. 547-562. L. Hinnov February 17, 2012

PHYSICAL CHEMICAL feedbacks Major products of weathering: Physical weathering is the mechanical fragmentation of rocks from stress acting on them from Earth surface processes. Chemical weathering involves chemical reactions between Earth surface chemistry (water) and minerals that progressively decompose solid rock. PHYSICAL CHEMICAL feedbacks Famous experiment: Griggs, 1936 heated and cooled cubes of granite 140ºC to 30ºC for the equivalent of 240 years of daily fluctuations, but nothing happened. That was dry, but with wetting, in ~2.5 years they fell apart. Major products of weathering: (1) fractured rock (2) regolith (3) ions in solution Earth's Dynamic Systems, Tenth Edition, Prentice Hall, 2004 By Dr. W. Kenneth Hamblin and Dr. Eric H. Christiansen Chapter 10 - Weathering Notes from: http://www.public.asu.edu/~arrows/geomorph/GLG362--weathering.html

Hamblin & Christiansen (2004) Earth's Dynamic Systems, Tenth Edition, Prentice Hall, 2004 By Dr. W. Kenneth Hamblin and Dr. Eric H. Christiansen Chapter 10 - Weathering Brantley et al., 2011, 12 testable hypotheses on the geobiology of weathering, Geobiology, 9, 140-165. Brantley et al. (2011) Hamblin & Christiansen (2004)

CONDITIONS ASSOCIATED WITH CHEMICAL V. PHYSICAL WEATHERING Earth's Dynamic Systems, Tenth Edition, Prentice Hall, 2004 By Dr. W. Kenneth Hamblin and Dr. Eric H. Christiansen Chapter 10 - Weathering

COMMON MINERALS IN ROCKS Common rock-forming minerals Crustal abundance of minerals Pie Chart from Ronov and Yaroshevsky, 1969 (from General Geology (5th ed.), by Foster, Merrill Publishing Co., 1988). Llist from: http://www.stockton.edu/~epsteinc/cheweath.htm Ronov & Yaroshevsky, 1969

COMMON MINERALS IN ROCKS The higher the Si:O ratio, the more resistant a mineral is to chemical weathering: http://www.stockton.edu/~epsteinc/cheweath.htm

Goldich Stability Series “Reverse Bowen Reaction Series” Earth's Dynamic Systems, Tenth Edition, Prentice Hall, 2004 By Dr. W. Kenneth Hamblin and Dr. Eric H. Christiansen Chapter 10 - Weathering Goldich, S.S., 1983, A study in rockweathering, Journal of Geology, v. 46, pp. 17-58. High temp. minerals weather first….

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CHEMICAL WEATHERING OF ROCKS AND CO2 DRAWDOWN: 1) Congruent-minerals totally dissolve 2) Incongruent-mineral is transformed into another mineral COMMON WEATHERING REACTIONS: carbonation (breakdown by weakly acidic rainwater) hydrolysis (breakdown by water) hydration (breakdown by the absorption of water) oxidation (breakdown by the oxygen in air and water) CARBONATION (DISSOLUTION): Calcite: HYDROLYSIS: Plagioclase (albite): Crustal abundance of minerals Pie Chart from Ronov and Yaroshevsky, 1969 (from General Geology (5th ed.), by Foster, Merrill Publishing Co., 1988). Potassium Feldspar: 2KAlSi3O8 + 9H2O + 2CO2 ⇌ Al2Si2O5(OH)4 (kaolinite) + 2HCO3- + 4H4SiO4 + 2K+ 3KAlSi3O8 + 14H2O + 2CO2 ⇌ KAl3Si3O10(OH)2(illite) + 2HCO3- + 6H4SiO4 + 2K+ Depending on K+ content of the solution.

CHEMICAL WEATHERING OF ROCKS AND CO2 DRAWDOWN: Olivine: Wollastonite: (a pyroxene) Notes: http://www.public.asu.edu/~arrows/geomorph/GLG362--weathering.html

DISSOLUTION RATE OF PLAGIOCLASE Brantley et al., 2011, 12 testable hypotheses on the geobiology of weathering, Geobiology, 9, 140-165. Brantley et al. (2011) Laboratory rates are order of magnitude faster than natural rates Note: BET analysis = Brunauer-Emmett-Teller (BET) Surface Area Analysis

Earth's Dynamic Systems, Tenth Edition, Prentice Hall, 2004 By Dr. W. Kenneth Hamblin and Dr. Eric H. Christiansen Chapter 10 - Weathering

Earth's Dynamic Systems, Tenth Edition, Prentice Hall, 2004 By Dr. W. Kenneth Hamblin and Dr. Eric H. Christiansen Chapter 10 - Weathering