1. Weathering L. Hinnov February 17, 2012 Reading list:
Brantley, S., and 26 others, 2011, 12 testable hypotheses on the geobiology of weathering, Geobiology, 9,
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
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
L. Hinnov
February 17, 2012

2. 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:

3. 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,
Brantley et al. (2011)
Hamblin & Christiansen (2004)

4. 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

5. 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:
Ronov & Yaroshevsky, 1969

6. COMMON MINERALS IN ROCKS
The higher the Si:O ratio, the more resistant a mineral is to chemical weathering:

7. 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
High temp. minerals weather first….

8. Downloaded from http://www. skidmore

9. 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.

10. CHEMICAL WEATHERING OF ROCKS AND CO2 DRAWDOWN:
Olivine:
Wollastonite:
(a pyroxene)
Notes:

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

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

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