Weathering of Ultramafic Rocks and Element Mobility at Mt. Prinzera, Northern Apennines, Italy

Giampiero Venturelli, Simona Contini*, Achille Bonazzi and Alessandro Mangia
Dipartimento di Seienze della Terra, Università di Parma, Viale delle Scienze 78, 43100 Parma, Italy
Dipartimento di Chimica Generale e Inorganica, Università di Parma, Viale delle Scienze 78, 43100 Parma, Italy
*Present address: GEODE SCRL-Studi Geologici e Petrografici, Viale Duca Alessandro 1, 43100 Parma, Italy.

Abstract: The weathering of the Mt. Prinzera serpentinites (Parma province, Northern Apennines, Italy) produced dominant smectite and minor Fe-hydroxides. The mobility of the elements during weathering has been estimated using the ratio Ki=MiS∕MiR, where Mi indicates the mass of a generic component i before (R) and after (S) the weathering, and using TiO2 as a practically immobile component. For prevalently to tendentially mobile elements, the degree of mobility, which in our case increases as Ki decreases, is in the order Mn ≈ Cr = Fe < V ≈ Zn ≈ Co < Ni < Si < Mg < Ca. The elements Ti, Ga, Al and Zr are prevalently immobile. The mass chemically removed by the circulating waters during weathering may reach very high values (on average 52% of the original mass of serpentinite) and the main contribution to the mass loss is due to Si and Mg. The composition of the perennial and ephemeral springs in the area is in agreement with the degree of the element mobility at least for Cr, Mg and Ca.

Keywords: element mobility • weathering • serpentinites • Northern Apennines • Italy

Mineralogical Magazine; December 1997 v. 61; no. 409; p. 765-778; DOI: 10.1180/minmag.1997.061.409.02
© 1997, The Mineralogical Society
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