1. The layer charge of vermiculite minerals is less than the layer charge of the
ID: 294813 • Letter: 1
Question
1. The layer charge of vermiculite minerals is less than the layer charge of the minerals
from which they are derived.
a. What are the minerals from which trioctahedral vermiculites are derived and what are
possible mechanisms of layer charge reduction in these minerals?
b. What are the minerals from which dioctahedral vermiculites are derived and what are
possible mechanisms of layer charge reduction in these minerals?
3. The weathering sequence, biotite ? trioctahedral illite ? saponite ? kaolinite, cannot
occur. Discuss why this is the case.
4. The Goldich stability series and the Bowen reaction series are very similar in their
presentation. Discuss why this should be the case.
Explanation / Answer
1.vermiculites have higher cation exchange capacity and greater exchange for Al4+ for Si
a. Trioctahedral vermiculites are derived from alteration of phlogopite and biotite and sometimes chlorite,pyroxene.
In phlogophite charge is blanced by interlayer potassium which balances the Al for Si substitution.Where as in Vermiculites substitution is blanced by partly by Al,Fe3 for Mg in the octahedral layer and partly by interlayer cations which are divalent Mg.
b.dioctahedral vermiculites are rare but are known to occur in soils.They are alteration product of muscovite
as their diagenesis is not clear it is only known they have high potential for potassium selective absorption
3.biotite and muscovite are weathered to produce trioctahedral, vermiculite and dioctahedral illite
4.The bowen reaction series and goldich stability series are both same bt opposite in nature.The bowens reaction series show the formation of minerals in a specific series when the magma cools.Where as the goldich series shows the stability of the minerals.The last formed in Bowens reaction series (Quartz) is the most stable mineral in goldich stability series
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.