FIG. 16. A. Plot of total REE vs. Zr for all rock types. Zirconium is an incompatible and immobile element. The positive correlation suggests that the REE were also immobile. B. Plot of Rb vs. Zr, illustrating that Rb acted as a mobile element during alteration. C. Plot of H₂O (wt %) vs. Pd (ppm) for variably altered melanocratic rocks of the southern Roby zone. The lack of any positive correlation suggests that aqueous fluid likely was not important in the concentration of Pd.