WEATHERING OF ULTRAMAFIC ROCKS AND ELEMENT MOBILITY AT MT. PRINZERA, NORTHERN APENNINES, ITALY

The weathering of the Mt. Prinzera serpentinites (Parma province, Nort hern Apennines, Italy) produced dominant smectite and minor Fe-hydroxi des. The mobility of the elements during weathering has been estimated using the ratio K-i = M-i(S)/M-i(R), where M-i indicates the mass of a generic component i before (R) and after (S) the weathering, and usi ng TiO2 as a practically immobile component. For prevalently to tenden tially mobile elements, the degree of mobility, which in our case incr eases as Ki decreases, is in the order Mn approximate to Cr = Fe < V a pproximate to Zn approximate to Co < Ni < Si < Mg < Ca. The elements T i, Ga, Al and Zr are prevalently immobile. The mass chemically removed by the circulating waters during weathering may reach very high value s (on average 52% of the original mass of serpentinite) and the main c ontribution to the mass loss is due to Si and Mg. The composition of t he perennial and ephemeral springs in the area is in agreement with th e degree of the element mobility at least for Cr, Mg and Ca.