The System SiO₂-AlOOH-Fe₂O₃-H₂O and the Kaolinitic Stage of the Goethite Facies

Abstract

Abstrac~A 25~ 1 atm total pressure phase diagram for the system SiO2-A1OOH-Fe2Os-H20 , is determined using the Phase Rule and Shreinemaker's technique as in Chesworth (1974). The waterpresent assemblages so defined are equivalent to a kaolinitic stage of the goethite facies of the weathering zone. As such they constitute the ideal stable assemblages of several earth-surface deposits and the stage can therefore be used to construct models of these deposits.

Aluminum coprecipitates with Fe (hydr)oxides: Does isomorphous substitution of Al3+ for Fe3+ in goethite occur?

“…These calculations agree with observations that gibbsite is more stable in soil environments than diaspore and boehmite (Chesworth, 1975).…”

The Occurrence of Lepidocrocite in Two Well-Drained Ontario Soils

“…However, this Fe(II) need not come exclusively from Fe(III) reduced as a result of anaerobic environment. Fe(II) from the structure of minerals (e.g., biotite) could serve as starting In nature, lepidocrocite is less stable than its polymorph goethite (Chesworth, 1975) and normally it transforms to the latter. What then causes it to persist for long periods of time in soils and sediments is not fully understood.…”