Study of the effect of the nature of the rodingite forming fluids in the minerals of the rodingite of Nain ophiolite

Two types of rodingitization (static and dynamic) are observed in the rodingites of the ophiolite north of Nain. Two stages have been occurred in the formation of static rodingites. At the initial stage, epidote, prehnite and hydrogrossular have crystallized respectively at the expense of plagioclase, with the increase of Calcium content rodingite forming fluid. In the advanced stage, xonotlite at the expense of plagioclase, and Mg – chlorite, tremolite and secondary diopside, at the expense of pyroxene, have formed simultaneously with an increase of Si content of rodingite forming fluid. The high content of vein xonotlite, in the dynamic rodingites, shows that the CaO/SiO2 ratio in the fluid is first close to one, but with time, it reduces to less than one and prehnite and pectolite have crystallized. In the dynamic rodingites, due to the low variations of rock – forming fluids, the mineralogy of dynamic rodingites do not vary much. In contrast, the mineralogy of static rodingites display variation, indicating the changing in composition of rock – forming fluids.