These trends are probably owing to the pH increase of the solution responsible for bauxitization. This is quite consistent with the results of the previous studies conducted by Calagari and Abedini (2007).
These anomalies decrease in the lower parts of the horizon (BRB, RB, and DRB) due to the complexation of [Ce.sup.4+] with carbonate ligands and hence its leaching during bauxitization processes (Karadag et al., 2009).
COMPUTATION OF MASS CHANGE OF REE DURING BAUXITIZATION
Most of the third and fourth tetrad groups including Dy, Ho, Er, Tm, Yb, and Lu were depleted during bauxitization processes of the parent rocks.
As illustrated in Figure 10c, similar form of tetrad (M-shaped) in chondrite-normalized REE distribution patterns also remains constant with no meaningful variation which is likely due to relatively stable conditions during bauxitization and/or weathering/alteration as well as diagenetic processes.
This feature can likely be related to pH increase of the solution responsible for bauxitization in this district.
Occurrence of both convex (M-shaped) and concave (W-shaped) curves in the chondrite-normalized REE patterns indicate different depositional conditions during bauxitization of the parent rocks.