I'm quite confused about the calculation of the CIA or the Chemical Index of Alteration (same with the other weathering indices). Would the weight percent do for the calculation? Or is the molecular proportion really the one I need?
The chemical index of alteration (CIA) using molecular proportions:
CIA = [Al2O3/(Al2O3+CaO*+Na2O+K2O]×100
where CaO* is the amount of CaO incorporated in the silicate fraction of the rock.
References:
Harnois, L., 1988, The CIW index: A new chemical index of weathering: Sedimentary Geology, v. 55, p. 319–322. doi:10.1016/0037-0738(88)90137-6
Nesbitt, H.W., and Young, G.M., 1982, Early Proterozoic climates and plate motions inferred from major element chemistry of lutites: Nature, v. 299, p. 715–717. doi:10.1038/299715a0
I think an excellent source will be find in:
https://webcache.googleusercontent.com/search?q=cache:OjJKp6mPqBAJ:https://www.tcd.ie/Geology/assets/doc/WeatheringIndexCalculations.xlsx+&cd=5&hl=ru&ct=clnk&gl=ru
Article Chemical weathering indices applied to weathering profiles d...
Dear Mr. Amores,
I have not add too much to what has already been referred to. Please carefully look at the paper published in "Chemical Geology". Perhaps you will be encouraged to re-direct your thoughts also to the integration of mineralogy such as heavy minerals and phyllosilicates into your investigation. Indeed, it not as easy as passing powdered material through an analytical device in a chemical laboratory, but the widening of the database warrants the efforts taken in this direction. The combination of chemical indices and the detailed investigation of the minerals in the topsoil and the weathering mantle are the best and most efficacious approach to be taken. Chemistry alone always means the job halfway done.
Best regards
H.G.Dill
Combined with chemistry of rock weathering, the quantity and nature of newly-formed minerals (e.g., clays, Fe oxyhydroxides...) vs. fresh and/or non completely weathered parent minerals are certainly relevant to investigate and estimate the intensity of parent-rocks weathering. However, here is a review paper of the popular CIA (Nesbit & Young, 1982) with discussion and the proposition of an alternative weathering intensity index or scale, hoping this paper would be useful for you. Enjoy reading and testing.
You know the Fressynet`s investigations of France, he make many calculations in lateritic profile.
I find email, and send to you,
Sincerely, Arturo.
Thanks very much Anicet.
Tomorow, I want to speaks with you,
Sincerely, Arturo.
Hi everyone!
Thank you very much for the responses, especially for the references. They were really very helpful. :)
Hi,
Chemical Index of Alteration helps to measure the rate of weathering of the palaeosol. Nesbit and Young (1982) proposed a formula to measure CIA.
CIA = Al2O3/(Al2O3+CaO+Na2O+K2O)*100
CIA = {Al2O3 / (Al2O3 + CaO* + Na2O + K2O)} x 100
PIA = {(Al2O3 – K2O) / ((Al2O3 - K2O) + CaO* + Na2O)} x 100
CIW = {Al2O3 / (Al2O3 + CaO* + Na2O)} x 100
CIW´ = {Al2O3 / (Al2O3 + Na2O)} x 100
In the above equations the major oxides are expressed in molar propotions and CaO* is the content of CaO incorporated in silicate fraction. McLennan (1993) proposed an indirect method for quantifying CaO content of silicate fraction assuming reasonable values of Ca/Na ratios of silicate material. Procedure for quantification of CaO content (CaO*) of silicate fraction involves subtraction of molar proportion of P2O5 from the molar proportion of total CaO. After subtraction, if the “remaining number of moles” is found to be less than the molar proportion of Na2O, then the “remaining number of moles” is considered as the molar proportion of CaO of silicate fraction. If the “remaining number of moles” is greater than the molar proportion of Na2O, then the molar proportion of Na2O is considered as the molar proportion of CaO of silicate fraction (CaO*).
@ Jhedy Amores
You can find some weathering indices in the Table 2 doc. I hope ıt is useful for your study.
Tamer KORALAY
Dear sir
Before calculating CIA it is necessary identify your sample types ...
you can able to calculate the chemical index of alteration (CIA) by using..
CIA = [Al2O3/(Al2O3+CaO*+Na2O+K2O]×100
where CaO* : concentration of CaO in silicate fraction of the samples
References:
Harnois, L., 1988, The CIW index: A new chemical index of weathering: Sedimentary Geology, v. 55, p. 319–322. doi:10.1016/0037-0738(88)90137-6
Nesbitt, H.W., and Young, G.M., 1982, Early Proterozoic climates and plate motions inferred from major element chemistry of lutites: Nature, v. 299, p. 715–717. doi:10.1038/299715a0
Gents,
Please when using EDXRF, noticed mud additives affect Uranium reading specially Marble (Caco3), what can i do to Remove this affection?
What is the unit of the elements Al2O3, CaO* , Na2O and K2O to calculate CIA?
Should be converted to molar proportions?
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